View
192
Download
13
Category
Tags:
Preview:
Citation preview
A Project Report on
“Design and Fabrication of Unmanned Aerial
Vehicle” By
PRASHANTH NATARAJAN PRATEEK JOLLY
USN: 1PI07ME065 USN: 1PI07ME067
VIPUL PAUL
USN: 1PI07ME119
Submitted to
VISVESVARAYA TECHNOLOGICAL UNIVERSITY
BELGAUM-590 014
in partial fulfillment of the requirements for the
award of the degree of
BACHELOR OF ENGINEERING
IN
MECHANICAL ENGINEERING
Project work carried out at
P.E.S. INSTITUTE OF TECHNOLOGY
BANGALORE-560 085
Under the guidance of
Dr.T.S.PRAHLAD
Chair Professor in Fluid Mechanics,
Department of Mechanical Engineering,
P.E.S.Institute of Technology,
Bangalore-560085.
DEPARTMENT OF MECHANICAL ENGINEERING
P.E.S.INSTITUTE OF TECHNOLOGY
BANGALORE-560 085
Page 1
P.E.S. Institute of Technology
(AUTONOMOUS INSTITUTE UNDER VTU, BELGAUM)
100 ft Ring Road, Banashankari 3rd Stage
,
Bangalore-560085,
Department of Mechanical engineering
CERTIFICATE
Certified that the project work entitled “Design and Fabrication of Unmanned Aerial
Vehicle " carried out by Prashanth Natarajan (1PI07ME065), Prateek Jolly
(1PI07ME067) and Vipul Paul (1PI07ME119) who are bonafide students of P.E.S.Institute
of Technology, in partial fulfilment of Bachelor of Engineering in Mechanical Engineering
of Visvesvaraya Technological University, Belgaum during the year 2011. The project has
been approved as it satisfies the academic requirements in respect of project work prescribed
for the said degree.
Signature of the Guide Signature of the HOD Signature of the Principal
External Viva:
Signature of the Examiner with Date
1.
2.
Page 2
We, Prashanth Natrajan, Prateek Jolly and Vipul Paul, hereby declare that the Project Work
entitled “Design and Fabrication of Unmanned Aerial Vehicle” has been independently
carried out by us under the guidance of Dr. T. S. Prahlad, Chair Professor in Fluid Mechanics,
Department of Mechanical Engineering, P.E.S.I.T, Bangalore in partial fulfilment of the requirements
of the degree in Bachelor of Engineering in Mechanical Engineering Visvesvaraya Technological
University, Belgaum. We further declare that, we have not submitted this work either in part of full to
any other university for award of any degree.
Place: Bangalore.
Date: 27th May, 2011.
Prashanth Natrajan
USN: 1PI07ME065
B.E. (ME)
P.E.S.I.T
Bangalore
Prateek Jolly
USN: 1PI07ME067
B.E. (ME)
P.E.S.I.T
Bangalore
Vipul Paul
USN: 1PI07ME119
B.E. (ME)
P.E.S.I.T
Bangalore
Contents
Abstract ................................................................................................................................................... 7
Acknowledgements ................................................................................................................................. 9
1) Introduction ................................................................................................................................... 10
Applications ....................................................................................................... 10
Steps in the Design Process ................................................................................. 11
1.2.1) Literature survey: ................................................................................................................ 11
1.2.2) Theoretical Design: ....................................................................................................... 11
1.2.3) Prototype Fabrication and flight tests: .......................................................................... 11
2) Problem Statement ........................................................................................................................ 12
2.1) Design Considerations .................................................................................. 12
2.2) Mission ....................................................................................................... 12
3) Design........................................................................................................................................... 13
3.1) Components ................................................................................................. 14
3.2) Weight of Components ................................................................................. 14
3.3) Wing Loading .............................................................................................. 15
3.4) Wing Geometry............................................................................................ 15
3.5) Lift and Drag ............................................................................................... 15
3.6) Airfoil selection .......................................................................................... 16
3.7) Fuselage drag calculations ............................................................................ 19
3.8) Velocity Correction ..................................................................................... 20
3.9) Mission ....................................................................................................... 23
3.10) Take-Off and Climb ................................................................................... 23
3.11) Energy requirements for mission ................................................................. 24
3.11.1) Take-off ......................................................................................................................... 24
3.11.2) Loiter ............................................................................................................................. 24
3.11.3) Descent Glide ................................................................................................................ 24
3.12) Stability .................................................................................................... 26
3.13) Horizontal Tail Sizing ................................................................................ 27
3.14) Elevator Sizing .......................................................................................... 28
3.15) Vertical Tail Sizing .................................................................................... 28
Page 1
3.16) Rudder Sizing ............................................................................................ 29
3.17) Aileron Sizing ........................................................................................... 29
3.18) Components Selected ................................................................................. 30
3.18.1) Global Positioning System (GPS) ............................................................. 30
3.18.2) Camera ................................................................................................... 31
3.18.3) Motor ..................................................................................................... 31
3.18.4) Servo Motors .......................................................................................... 31
3.18.5) Propeller ................................................................................................. 32
3.18.6) Receiver ................................................................................................. 32
3.18.7) Electronic Speed Control ......................................................................... 32
4) Fabrication ...................................................................................................... 33
4.1) Fuselage Fabrication .................................................................................... 34
4.1.1) Balsa Fuselage .......................................................................................... 34
4.1.2) Coroplast Fuselage: ................................................................................... 39
4.2) Wing Fabrication ......................................................................................... 40
4.2.1) Material .................................................................................................... 40
4.2.2) Hot Wire Cutter ........................................................................................ 40
4.2.3) Steps in Fabrication of Foam Wing: ........................................................... 43
5) Glider Tests ................................................................................................................................... 50
5.1) Glider test without a spar ............................................................................. 50
5.2) Glider Tests with Balsa Spar ........................................................................ 50
5.3) Glider tests with Carbon Fibre spar ............................................................... 51
6) Maiden Flight ................................................................................................................................ 53
6.1) Setup........................................................................................................... 53
6.2) Summary ..................................................................................................... 53
6.3) Flight Path .................................................................................................. 53
6.4) Objectives Achieved .................................................................................... 53
6.5) Duration of Flight - 21 seconds ................................................ 53
6.6) Comments ................................................................................................... 54
6.7) Damage Reported ......................................................................................... 54
7) Flight Test Number 1: First Flight with Coroplast Fuselage ........................................................ 56
7.1) Setup........................................................................................................... 56
7.2) Summary ..................................................................................................... 56
7.3) Flight Path .................................................................................................. 56
7.4) Objectives Achieved .................................................................................... 56
Page 2
7.5) Duration of Flight - 1 minute ................................................................ 57
7.6) Comments ................................................................................................... 57
7.7) Damage Reported ......................................................................................... 57
8) Flight Test Number 2: Acrobatics and Manoeuvrability Test ...................................................... 59
8.1) Setup........................................................................................................... 59
8.2) Summary ..................................................................................................... 59
8.3) Flight Path .................................................................................................. 59
8.4) Objectives Achieved .................................................................................... 59
8.5) Duration of Flight: 1.10 minute .................................................................... 60
8.6) Comments ................................................................................................... 60
8.7) Damage Reported ......................................................................................... 60
9) Flight Test Number 3: Heavy Cross Winds with Aborted Landing .............................................. 61
9.1) Setup........................................................................................................... 61
9.2) Summary ..................................................................................................... 61
9.3) Flight Path .................................................................................................. 61
9.4) Objectives Achieved .................................................................................... 61
9.5) Duration of Flight: 2.30 minutes ................................................................... 62
9.6) Comments ................................................................................................... 62
9.7) Damage Reported ......................................................................................... 62
10) Flight Test Number 4: Wing Failure and First Crash ............................................................... 63
10.1) Setup ......................................................................................................... 63
10.2) Summary ................................................................................................... 63
10.3) Flight Path ................................................................................................. 63
10.4) Objectives Achieved .................................................................................. 63
10.5) Duration of Flight: 0.50 minutes ................................................................. 63
10.6) Comments .................................................................................................. 64
10.7) Damage Reported ....................................................................................... 64
10.8) Analysis of the Crash ................................................................................. 66
10.9) Changes in Design ..................................................................................... 66
11) Flight Test Number 5: Gusty Weather Flight ........................................................................... 67
11.1) Setup ......................................................................................................... 67
11.2) Summary ................................................................................................... 67
11.3) Flight Path ................................................................................................. 67
11.4) Objectives Achieved .................................................................................. 67
11.5) Duration of Flight: 3 seconds ...................................................................... 67
Page 3
11.6) Comments .................................................................................................. 68
11.7) Crash Analysis ........................................................................................... 68
11.8) Damage Reported ....................................................................................... 68
11.9) Changes to Design: None ........................................................................... 68
12) Flight Test Number 6: First Long Endurance Flight ................................................................ 69
12.1) Setup ......................................................................................................... 69
12.2) Summary ................................................................................................... 69
12.3) Flight Path ................................................................................................. 69
12.4) Objectives Achieved .................................................................................. 69
12.5) Duration of Flight: 6 minutes ...................................................................... 70
12.6) Comments .................................................................................................. 70
12.7) Damage Reported ....................................................................................... 70
13) Flight Test Number 7: Flight Test for Manoeuvrability ........................................................... 71
13.1) Setup ......................................................................................................... 71
13.2) Summary ................................................................................................... 71
13.3) Flight Path ................................................................................................. 71
13.4) Objectives Achieved .................................................................................. 71
13.5) Duration of Flight: 2.30 minutes ................................................................. 71
13.6) Comments .................................................................................................. 72
13.7) Damage Reported ....................................................................................... 72
14) Flight Test Number 8: First Flight in PESIT with On-board Camera ....................................... 73
14.1) Setup ......................................................................................................... 73
14.2) Summary ................................................................................................... 73
14.3) Flight Path ................................................................................................. 73
14.4) Objectives Achieved .................................................................................. 73
14.5) Duration of Flight: 2.30 minutes ................................................................. 73
14.6) Comments .................................................................................................. 74
14.7) Damage Reported ....................................................................................... 74
15) Flight test number 9: 20 Minute Flight ..................................................................................... 79
15.1) Setup ......................................................................................................... 79
15.2) Summary ................................................................................................... 79
15.3) Flight Path ................................................................................................. 79
15.4) Objectives Achieved .................................................................................. 79
15.5) Duration of Flight: 20 minutes and 36 seconds ............................................. 79
15.6) Comments .................................................................................................. 83
Page 4
15.7) Damage Reported: None ............................................................................. 83
16) Comparison of Google Earth Snapshots with Snapshots Taken From the P❺ ........................ 84
17) What Makes the P❺ Different? .............................................................................................. 87
17.1) Cost Split Up: ............................................................................................ 87
18) Future Work .............................................................................................................................. 90
18.1) Autopilot ................................................................................................... 90
18.2) Live telemetry and Video feed .................................................................... 90
18.3) Extension of Flight time ............................................................................. 91
18.4) Portability ................................................................................................. 91
19) Conclusion ................................................................................................................................ 92
Appendix A: Software Used................................................................................................................... 93
Appendix B: Original Design .................................................................................................................. 95
Appendix C: References: ..................................................................................................................... 125
Page 5
Table of Figures Figure 1: Airfoil Sections ....................................................................................................................... 17
Figure 2: Combined Drag Polar ............................................................................................................. 17
Figure 3: Combined Cl-Alpha Graph ..................................................................................................... 17
Figure 4: PT - 40 Section ........................................................................................................................ 18
Figure 5: Cl - Alpha and Drag Polar ....................................................................................................... 18
Figure 6: Graph to Obtain Optimum Cruise Velocity ............................................................................ 21
Figure 7: Mission Profile ....................................................................................................................... 23
Figure 8: Graph to Obtain Optimum Rate of Climb .............................................................................. 24
Figure 9: Variation of Static Margin with Wing Leading Edge Position ................................................ 27
Figure 10: Elevator Sizing ...................................................................................................................... 28
Figure 11: Tail Volume Ratios ............................................................................................................... 29
Figure 12: The Fuselage Sections Being Cut Out from the Balsa Piece ................................................. 35
Figure 13:The Plywood Pieces Being Positioned Along With the Balsa Side Panels in the Vice and
Being Glued Using Fevicol ..................................................................................................................... 35
Figure 14: The curve of the aft section of the fuselage being done ..................................................... 36
Figure 15: The fuselage during fabrication placed in the vice (Top View) ............................................ 36
Figure 16: Leading edge of the empennage being sanded into shape ................................................. 37
Figure 17: Fuselage after completion ................................................................................................... 37
Figure 18: Fuselage with flap open ....................................................................................................... 38
Figure 19: Fuselage with flap open ....................................................................................................... 38
Figure 20: Hot Wire Cutter .................................................................................................................... 42
Figure 21: The plywood template being placed on the foam block ..................................................... 45
Figure 22: The foam cutter being run on the template. Cutting the leading edge of the wing ........... 45
Figure 23: The foam cutter being run on the template. Cutting the trailing edge ............................... 46
Figure 24: Breaking away the excess foam around the cut wing ......................................................... 46
Figure 25: the wing being removed from the block ............................................................................. 47
Figure 26: The cut wing removed and placed on a table ...................................................................... 47
Figure 27: Applying the Monokote layer using the hot iron ................................................................. 48
Figure 28: A number of attempts to get the correct linkage between the Aileron Servo and the
Ailerons ................................................................................................................................................. 48
Figure 29: Placing the Plastic protective sheath around the wing to hot glue into place .................... 49
Figure 30: Completed Wing (Only MonoKote application left) ............................................................ 49
Figure 31: Broken wing without spar .................................................................................................... 50
Figure 32: Glider with full scale wing and empennage in flight ............................................................ 51
Figure 33: The NAL Grounds where the flight test was carried out ..................................................... 55
Figure 34: The aircraft taking off by hand launch ................................................................................. 55
Figure 35: The team setting up the model before flight ....................................................................... 58
Figure 36: Aircraft being launched and pilot with remote ................................................................... 58
Figure 37: Aircraft in flight .................................................................................................................... 60
Figure 38: Aircraft facing a strong crosswind on landing approach ..................................................... 62
Page 6
Figure 39: the rubber band has eaten half way into the foam wing. The left rubber band has been put
back into position .................................................................................................................................. 64
Figure 40: the wing could be actuated about the carbon fibre spar. This is why the flutter was seen
from the ground .................................................................................................................................... 65
Figure 41: the missing Servo screw. ...................................................................................................... 65
Figure 42: PESIT Garden and Fountain ................................................................................................. 75
Figure 43: Professor M.R.Doreswamy Silver Jublee Block (A- Block) ................................................... 75
Figure 44: Department of Mechanical Engineering (C-Block) ............................................................... 76
Figure 45: F Block (left) and Department of Electrical and Electronics Engineering (Right) ................. 76
Figure 46: Tech Park (E-Block)............................................................................................................... 77
Figure 47: Boys Hostel blocks ............................................................................................................... 77
Figure 49: Stitched image showing the new football ground and a part of the cricket ground ........... 78
Figure 48: Stitched images showing A-block, the fountain, entry way and the Department of
Mechanical Engineering, motorcycle parking in a single frame ........................................................... 78
Figure 50: Aircraft taking off ................................................................................................................. 80
Figure 51: Aircraft on final approach .................................................................................................... 81
Figure 52: Aircraft levelling off .............................................................................................................. 81
Figure 53: Aircraft attempting Flare ..................................................................................................... 82
Figure 54: Aircraft after landing ............................................................................................................ 82
Figure 55: Autopilot chipset .................................................................................................................. 90
Figure 56: Snapshot (12.97108, 77.67567) ........................................................................................... 84
Figure 57: Snapshot (12.560668, 77.327044) ....................................................................................... 85
Figure 58: Snapshot (12.55549, 77.324981) ......................................................................................... 86
Page 7
Abstract
In the present time, the need for small aircraft which can be remotely operated has
taken at most priority in the needs of society. The multiple roles that an UAV can take clearly
shows its versatility. This provided us the motivation required to design an UAV that could
be fabricated using low cost materials but not compromising on the quality of the aircraft.
We started out by defining a problem statement, “To design and fabricate an Unmanned
Aerial Vehicle capable of carrying a light weight camera and a GPS unit, capable of a
sustained flight time of 20 minutes”.
Why did we choose to carry a camera and a GPS unit as payload? The reason is simple, we
wanted our UAV to be used for aerial tracking purposes. We thought the best application for
such an aircraft would be in search and reconnaissance operations after natural calamities and
also for tracking radio collars of endangered animals.
We started off with a long drawn design process following a conceptual design approach. We
also kept looking at the UAVs present in the market and tried our best to incorporate the
positive aspects of these UAVs. Once the design was complete we entered the world of
fabrication which was completely new to us.
It was the first time we were using a myriad of tools and each day was a learning experience
right form choosing the materials to working on them. We had opportunities to visit the
industry and see how Laser cutting is carried out. We carried out a complete survey to find
out the best dealers to buy our components and raw materials from. We also built a number of
tools to fit our needs of the fabrication process. These tools were built from materials that
could be found at home and proved to be very efficient and effective in the fab process.
We had to chance to make a number of innovations and also made a number of low cost and
equally effective solutions to many problems that we faced during the course of the project.
The toughest part of the project was carrying out the flight tests. We believed in the concept
of build and fly where we build our own aircraft and fly it ourselves. A number of flights
were put in and the results were both joyous where we would celebrate a very successful
flight or sometimes would result in us heading back home to repair the aircraft. The long
endurance flights where we kept breaking the time limits that we set were the most satisfying.
The day we completed a 20 minute flight without any glitches was the most joyous moment
for our team.
During the project apart from having fun, we learnt a number of things. The first and most
important thing that we learnt is how to work as a team, then we learnt how difficult it is to
make something fly. We learnt to use a number of tools for the first time, we learnt the
challenges in fabrication, we learnt how to improve upon our mistakes.
At the end of the project we had an aircraft that could fly for the 20 minute duration specified
by the project target and had the capability to take a video on board and also had the
Page 8
provision for a GPS unit to track the entire flight path, thus successfully completing our goals
and our project.
The beautiful thing about this project is that is doesn’t end here. There is always scope for
improvement. There are new areas to venture into and new things to learn.
Page 9
Acknowledgements
This project would not have possible but for the opportunity that the Peoples Educational
Society Institute of Technology, Bangalore gave us.
It is a pleasure for us to thank all those people who supported and guided us to make this
project a success both directly and indirectly.
We extend our gratitude to our guide Dr. T. S. Prahlad, Chair Professor of Fluid Mechanics,
P.E.S.I.T. for allowing us to further our knowledge and gain a profound understanding of the
basic design principles involved in developing an unmanned aerial vehicle. We would like to
sincerely thank him, for offering this project to us and constantly encouraging us along the
duration of the project. Thank you sir for the patience and kindness you have given us, we
truly value it a lot.
We would also like to take this opportunity to thank Mr Satish Nair, Viable Central Asia for
his passion to help and support students. Thank you sir for your contribution to our project.
We would also like to thank Mr Prajwal of NAL, Bangalore for providing us with a number
of suggestions and ideas many of which we have incorporated into our project. We would
also like to thank him for the hardware support he provided us with and the tips he gave us on
flying. Thank you Mr Prajwal for your time and for your patience and your constant
encouragement.
We also express our gratitude to Dr. K.N.B. Murthy, Principal, P.E.S.I.T. and
Dr K. Narasimha Murthy, Head of Mechanical Department, P.E.S.I.T. for encouraging us and
partially funding our project. Thank you Sir. This project would not have been a success if
not for your generosity.
We would like to thank our parents for supporting us in our times of success and failures.
They have been our pillars of support, constantly been by our side and have helped us finish
this project successfully.
Lastly we would like to say that it was a great honour for us to be associated with all these
people and we have enjoyed each moment of the past 3 months in which we have been
learning and progressing under their guidance and support.
Page
10
1) Introduction
Unmanned Aerial Vehicles (UAVs) are remotely piloted or self-piloted aircraft that can carry
cameras, sensors, communications equipment or other payloads. They have been used in a
reconnaissance and intelligence-gathering role since the 1950s, and more challenging roles
are envisioned, including combat missions. To distinguish UAVs from missiles, a UAV is
defined as “a powered, aerial vehicle that does not carry a human operator, uses
aerodynamic forces to provide vehicle lift, can fly autonomously or be piloted remotely,
can be expendable or recoverable, and can carry a lethal or nonlethal payload.”
Currently, military UAVs perform reconnaissance as well as attack missions. While many
successful drone attacks on militants have been reported, they are also prone to collateral
damage and/or erroneous targeting, as with many other weapon types.
UAVs are also used in a small but growing number of civil applications, such as fire fighting
or non-military security work, such as surveillance of pipelines. UAVs are often preferred for
missions that are too "dangerous" for manned aircraft.
Applications
1. Reconnaissance :
Reconnaissance in a purely military sense involves the constant monitoring of enemy
troop movement and formations. Reconnaissance missions require the aircraft to be
behind enemy lines for an extended period of time thus, these missions are highly
dangerous for manned aircraft. Such missions are the domain of UAVs. These aircraft
are capable of surveying enemy positions and providing real time data back to the
controllers and in case a UAV is shot down the mission commander doesn’t have to
worry about pilot casualties.
2. Remote sensing :
UAV remote sensing functions include electromagnetic spectrum sensors, biological
sensors, and chemical sensors. A UAV's electromagnetic sensors typically include
visual spectrum, infrared, or near infrared cameras as well as radar systems. Other
electromagnetic wave detectors such as microwave and ultraviolet spectrum sensors
may also be used, but are not very commonly used. Biological sensors are sensors
capable of detecting the airborne presence of various microorganisms and other
biological factors. Chemical sensors use laser spectroscopy to analyze the
concentrations of each element in the air.
3. Search and rescue:
UAVs will likely play an increased role in search and rescue in the world over the
years. They can be used to find victims and also hostages holed up.
Page
11
4. Providing timely information on highway or other transportation modes on traffic
flow and incidents, and the transmission of this information to the appropriate
decision maker, are key requirements for improving traffic and incident management.
The use of Unmanned Aerial Vehicles (UAVs), equipped with video cameras and/or
other sensors, is a technically viable method of providing timely information to
support decisions regarding major traffic incidents and natural disasters, and also in
providing an improved security and safety for the public.
Steps in the Design Process
1.2.1) Literature survey:
In this step we understand what exactly a UAV is and understand its working. Here
the emphasis was on understanding the intricacies involved in the design process as
well as anticipating problems that can arise while applying the design to the actual
model. A survey was undertaken to find the best materials and places to source the
components and also the tools required to fabricate the prototype
1.2.2) Theoretical Design:
This was the first step taken into engineering design. It includes:
Initial sizing and weight estimation
Layout Drawings
Fuselage design
Wing design
Control surface design
Thrust requirements and power plant selection
1.2.3) Prototype Fabrication and flight tests:
A flight worthy prototype of the aircraft was fabricated and a number of flight tests
were conducted to check the air-worthiness of the aircraft. Each step of the test
demanded more from the aircraft in terms of performance and operation. Also we
used the flight tests to practically reduce the wing span of the aircraft. The flight tests
were also helped us gather a lot of information about parameters that could not be
tested on simulations on the computer.
Page
12
2) Problem Statement
To design and fabricate an Unmanned Aerial Vehicle capable of sustained flight for 20
minutes, carrying a payload of a light weight camera and a GPS unit.
2.1) Design Considerations
1. Endurance – 20 Min
2. Payload: Camera and GPS unit
2.2) Mission
1. Hand launched Take off
2. Climb to desired altitude
3. Cruise for 19 minutes
4. Descent in 2 phases
5. Belly Landing
Two designs have been considered to achieve the goals set by the problem statement. The
first design is a delta wing model on which we had put an additional constraint of a wingspan
of 500mm. Prototype gliders of this design were fabricated and flown, but a number of
problems concerning the speeds and stability of the aircraft arose. These problems have been
discussed as a part of appendix 2. Thereafter we removed the self imposed constraint of a
500mm wingspan and designed an aircraft with a conventional rectangular wing. The initial
design phase of this planform showed us that we had overcome the problems that we faced
with the delta wing. Therefore this is the planform that we chose and further developed.
Our main aim was to try and build the aircraft using materials that are easily available in the
market, cost effective and at the same time not compromise on the quality of the aircraft.
We have tried to keep the costs low by using simple solutions to overcome a number of
hurdles that we faced in the course of completing this project.
Page
13
Design Conventional Planform
20 Minute endurance
Payload of a Camera and GPS unit
Page
14
3.1) Components
The aircraft is expected to be a lightweight reconnaissance aircraft and the components were selected
are listed below.
1. Global Positioning System (GPS)
2. Camera
3. Batteries
4. Motor
5. Servos
6. Electronic Speed Control
7. Transmitter and Receiver
8. Propeller
3.2) Weight of Components
Component Weight (Grams)
Servos 30
G.P.S 70
Camera 35
Receiver 28
Batteries 185
Motor 55
ESC 31
TOTAL PAYLOAD 434 Table 1:Weight Estimate
Page
15
3.3) Wing Loading
The weight of the aircraft being designed has been approximated to 500 grams.
Form a group of R.C aircraft which are a powered glider design similar in weight and having a similar
conventional platform as our design we have initially assumed the Aspect Ratio as 8 and also the wing
loading to be 38.91 N/m2
Thus, A.R = 8
The wing loading is = 38.91N/m2
From the wing loading we can find the wing area; S
= 4.68918/ 38.91= 0.1205 m
2
The wing span (b) can be calculated from the Aspect Ratio and the Wing area
Wing Span = b = √
= √
= 0.9819 m
3.4) Wing Geometry
A conventional rectangular wing is chosen. The wingspan, surface area and aspect ratio are known.
With these parameters we can calculate the Root Chord (Cr) of the wing
Root chord (Cr) =
( )
= 2* 0.1205/ (0.981889984* (1 + 1))
= 0.1227 m
3.5) Lift and Drag
Calculating Reynolds Number at the cruise speed of 14m/s;
Re =
= (1.225* 14* 0.1227)/ (2*10-5
)
= 105246.33
Clrequired = ( ) = (4.68918) / (0.5* 1.225* (14^2) * 0.1205)
Page
16
= 0.3241
3.6) Airfoil selection
A number of low Reynolds number airfoils were analysed for their 2D chars in XFLR5. The
characteristics that we were looking for were high lift at alpha = 0°, the cruise conditions fall within
the drag bucket, and a thick airfoil for structural reasons.
The Airfoils that were shortlisted were
1) Wortmann FX – 60
2) Selig 4083
3) PT 40
4) Gemini
5) Hobie
Page
17
Figure 1: Airfoil Sections
The thicker the airfoil, stronger the wing would be structurally. Therefore, structurally the Gemini,
followed by the PT 40 would produce the strongest wing.
The 2D CFD runs show that the Wortmann airfoil produces the greatest lift for a given angle of attack
followed by the Selig 4083, Hobie, PT 40 and the Gemini.
Figure 2: Combined Drag Polar
Figure 3: Combined Cl-Alpha Graph
Page
18
The Hobie is eliminated because it stalls very early at an angle of 7 degrees.
The Gemini is eliminated because of its sudden stall characteristics.
The Selig 4083 was constructed out of foam, but turned out to be too flimsy, thus getting eliminated.
The Wortmann airfoil, even though it is aerodynamically the best airfoil, producing most lift and least
drag at the cruise Reynolds number, is even weaker than the selig airfoil, especially near the trailing
edge. Therefore even it is eliminated.
The airfoil thus chosen is the PT 40
We have chosen the PT40 airfoil because of its high lift and low drag value at our Cl required along with
its very gentle stalling characteristics. This implies that the operator would have a large buffer zone in
which he can recover the aircraft if it approaches stall. The airfoil is also thicker which helps make the
wing stronger.
Figure 4: PT - 40 Section
Figure 5: Cl - Alpha and Drag Polar
For this value of Clrequired, from the graph the value of alpha initial is very close to 0 Degrees
CdInduced = ( ( ) = (0.3241^2) / (3.14 * 8)
= 0.004179
Page
19
Cf = 0 ( ( )) / (Log (105246.3327))2.58
= 0.007074
Cdw = 2 = 0.014149
3.7) Fuselage drag calculations
Fuselage length = 0.5m
Fuselage height = 0.056m
Fuselage width = 0.056m
Fuselage Wetted area = 0.112 m2
Cdf =
= 0.007074 * 0.112 / 0.1205
= 0.006574847
Overall Drag coefficient:
CdO = Cdw + Cdf = 0.014149 + 0.006574847 = 0.020724093
Accounting 10% more drag for interference we have;
Cd = CdO + CdInduced = 0.026976329
Page
20
3.8) Velocity Correction
Our initial cruise velocity of 14m/s was assumed from an existing Powered Glider R.C model. In the
second iteration we will find the optimum velocities for maximum endurance and range.
Velocity Cl D0 Di Drag Power Sink Rate
5 2.541061 0.042068 0.474343 0.516411 2.582054 0.550641
5.5 2.100051 0.050902 0.392019 0.442921 2.436065 0.519508
6 1.764626 0.060578 0.329405 0.389982 2.339895 0.498999
6.5 1.503587 0.071095 0.280676 0.351771 2.286511 0.487614
7 1.29646 0.082453 0.242012 0.324465 2.271252 0.48436
7.5 1.129361 0.094653 0.210819 0.305472 2.291037 0.48858
8 0.992602 0.107694 0.18529 0.292984 2.34387 0.499847
8.5 0.87926 0.121576 0.164132 0.285708 2.428522 0.517899
9 0.784278 0.1363 0.146402 0.282702 2.544317 0.542593
9.5 0.703895 0.151865 0.131397 0.283262 2.690987 0.573871
10 0.635265 0.168271 0.118586 0.286857 2.86857 0.611742
10.5 0.576204 0.185519 0.107561 0.29308 3.077338 0.656264
11 0.525013 0.203608 0.098005 0.301613 3.317743 0.707532
11.5 0.480352 0.222539 0.089668 0.312207 3.590376 0.765672
12 0.441156 0.242311 0.082351 0.324662 3.895942 0.830837
12.5 0.40657 0.262924 0.075895 0.338819 4.235234 0.903193
13 0.375897 0.284378 0.070169 0.354548 4.609118 0.982926
13.5 0.348568 0.306674 0.065068 0.371742 5.018517 1.070233
14 0.324115 0.329812 0.060503 0.390315 5.464405 1.165322
14.5 0.302148 0.35379 0.056402 0.410193 5.947793 1.268408
15 0.28234 0.37861 0.052705 0.431315 6.469727 1.379714
Page
21
15.5 0.264418 0.404272 0.049359 0.453631 7.031281 1.499469
16 0.248151 0.430774 0.046323 0.477097 7.633552 1.627908
Table 2: Cruise Speed Optimization
Figure 6: Graph to Obtain Optimum Cruise Velocity
From the Graph of Power Vs Velocity we see that the velocity for minimum power is approximately
8m/s.
At this velocity, the Cl value when calculated is found to be 0.9926. This is a very high value nearing
1. The Cl value can be decreased by increasing the cruise velocity of the aircraft.
We change the cruise velocity to 10m/s and recalculate the coefficients.
New Reynolds Number is calculated to be
Re =
= 1.225* 10 * 0.1227 / (2*10
-5) = 75175.95193
Recalculating the Cl value for cruise velocity of 10m/s,
Cl = 0.63520
Also recalculating the values of the Drag Coefficients:
Cdi = 0.0160572
Cdf = 0.007095308
Cdo = 0.022364601
Accounting an additional 10% of Overall Drag to account for interference, we have
Page
22
Cd = 0.040658283
From this value, drag is calculated to be = 0.300117 N
Thus the power required to overcome this drag is = Power = Drag * Velocity = 0.300117 * 10
= 3.00117 W
The stall speed for the aircraft is calculated as, VStall = √
= √
= 5.940751m/s
Page
23
3.9) Mission
The aircraft is hand launched from ground level by the operator. The aircraft ascends to four hundred
feet. The aircraft then loiters in the same area for nineteen to twenty minutes taking photographs. It
then descends back to the ground.
Figure 7: Mission Profile
3.10) Take-Off and Climb
Since the aircraft is hand launched, it needs to clear the ground as quickly as possible without
stalling. The initial thrust supplied to the aircraft must be enough to sustain the velocity of the aircraft
above its stall speed. The power required at take off to reach an assigned altitude of 400ft is calculated
for varying rates of climb at the take off velocity.
The equation to evaluate power consumed for varying rates of climb is
(
)
W – Weight of the aircraft
v – Velocity
D – Drag
L – Lift
θ - Angle of ascent
Page
24
Figure 8: Graph to Obtain Optimum Rate of Climb
The graph also seems to almost level off at about 90 seconds. Therefore a time of 100 seconds is
taken is taken to complete the ascent phase of the flight.
3.11) Energy requirements for mission
With an engine which consumes fuel such as aviation fuel or kerosene, the range or endurance of the
aircraft can be estimated by applying the Breguet formula. Our aircraft does not use a consumable
fuel, but rather a battery to power the electric motor, which is our primary thrust producing prime
over. Thus, in this case we estimate the amount of energy (joules) required to complete the mission
and then choose a suitable battery which can provide this amount of energy.
Our mission is broken up into 3 phases.
1) Takeoff
2) Loiter
3) Descent Glide
The energy required at each stage is estimated theoretically, and then added up to obtain the energy
required for the whole mission.
3.11.1) Take-off
The power required to reach four hundred feet has been estimated to be 8 watts. The aircraft
is expected to achieve this in 100 seconds. The product of time and power gives the energy
required. This is calculated to be 800 J.
3.11.2) Loiter
The aircraft now levels off and circles the area that has to be scanned. The aircraft remains in
this phase for up to nineteen minutes. The power required for sustained flight at 10m/s has
been estimated at 3.6 watts.
3.11.3) Descent Glide
0
5
10
15
20
25
30
35
0 20 40 60 80 100 120 140
Po
we
r (W
)
Time (s)
Selection of Rate of Climb
Page
25
After the aircraft has scanned a particular area, it begins an unpowered glide to the ground.
The aircraft continues in this state till it reaches an altitude of 20 feet.
The power consumed by the servos and the receiver has also been estimated.
Servos - 70mA at 11.1V for 20 minutes = 932 J
Reciever – 10mA at 11.1V for 20 minutes = 133 J
The energy required for the whole mission is estimated to be 6 kJ.
Efficiency of motor = 70%
Efficiency of propeller = 70%
Efficiency of Battery = 80%
The Energy requirement after taking into account the component efficiencies is 15.5 kJ.
Remote control aircraft pilots recommend that if an aircraft is designed to fly for certain endurance,
then, because of weather conditions, the energy requirement is taken as 1.5 times to compensate for
gusts, head winds, mid-course corrections etc.
Therefore the energy requirement = 1.5 x 15.5kJ = 23.25 kJ.
A 1000mA battery provides 36 kJ of energy. With an estimated battery efficiency of 80%, the energy
available from the battery is 28 kJ. Therefore this battery is chosen.
Page
26
3.12) Stability
The aircrafts designed to be very stable longitudinally so that the on-board camera does not jerk or
shudder, thereby compromising on the quality of images taken.
The static margin is the defined as the distance between the C.G. of the aircraft and the Aerodynamic
Center of the wing, and is usually measured as a percentage of the mean aerodynamic chord (MAC).
Since our wing is rectangular, the MAC is the same as the chord.
The static margin for gliders is between five and ten percent. Greater the margin, the greater the
stability. If the margin exceeds 10%, the aircraft become ultra stable and is very difficult to manuver.
The C.G. of the entire structure including the fuselage, tail, servos, motor and esc is found to lie 16
cm from the nose of the aircraft.
The battery is the heaviest component in the aircraft at 185g and is placed in the roomiest part of the
aircraft.
The wing is then moved about till the required static margin is achieved.
Position of
Wing
Wing CG Aerodynamic Center CG of A/C Static margin
3 7.305 6.075 13.41645 49.41324047
3.5 7.805 6.575 13.44913 46.26783837
4 8.305 7.075 13.48181 43.12243627
4.5 8.805 7.575 13.51449 39.97703418
5 9.305 8.075 13.54717 36.83163208
5.5 9.805 8.575 13.57985 33.68622998
6 10.305 9.075 13.61253 30.54082789
6.5 10.805 9.575 13.64521 27.39542579
7 11.305 10.075 13.67789 24.25002369
7.5 11.805 10.575 13.71057 21.1046216
8 12.305 11.075 13.74325 17.9592195
8.5 12.805 11.575 13.77593 14.8138174
9 13.305 12.075 13.80861 11.66841531
9.5 13.805 12.575 13.84129 8.52301321
10 14.305 13.075 13.87397 5.377611114
10.5 14.805 13.575 13.90664 2.232209017
11 15.305 14.075 13.93932 -0.91319308
11.5 15.805 14.575 13.972 -4.058595176
12 16.305 15.075 14.00468 -7.203997273
12.5 16.805 15.575 14.03736 -10.34939937 13 17.305 16.075 14.07004 -13.49480147
13.5 17.805 16.575 14.10272 -16.64020356
14 18.305 17.075 14.1354 -19.78560566
14.5 18.805 17.575 14.16808 -22.93100776
15 19.305 18.075 14.20076 -26.07640985
15.5 19.805 18.575 14.23344 -29.22181195
16 20.305 19.075 14.26612 -32.36721405 Table 3: Placement of Wing to get Appropriate Static Margin
Page
27
Figure 9: Variation of Static Margin with Wing Leading Edge Position
Therefore for a static margin of 10%, the leading edge of the wing is found to lie at 12.4 cm from the
nose of the aircraft.
3.13) Horizontal Tail Sizing
The tail-moment arm (TMA) is the distance between the mean aerodynamics chords of the wing and
the tail. The TMA was taken to be 2.5 times the wing’s MAC.
Therefore, TMA= 0.306841 m.
The area of the horizontal tail (HTA), is given by the formula,
HTA =
Where, WA is the Wing Area.
As the TMA was taken to be 2.5 times the MAC, HTA is 20% of the wing area.
Hence, HTA = 0.2 * 0.120513 = 0.024103 m2.
The aspect ratio of the tail was assumed to be 5.
Therefore, the span of the horizontal tail, bht = √ = 0.347151 m.
The chord of the horizontal tail, Crht =
= 0.06943 m.
y = -6.2908x + 68.286
-40
-30
-20
-10
0
10
20
30
40
50
60
0 5 10 15 20Stat
ic M
argi
n
Dist. From L.E. of Wing to Nose
Longitudinal Stability
Page
28
3.14) Elevator Sizing
The larger the elevator area, in proportion to the horizontal tail’s total area, the more effective the
elevator, as shown by the graph below.
Figure 10: Elevator Sizing
From the graph above, we can see that a value of Se/St lying between 0.3 to 0.35 gives an elevator
effectiveness of 70%. Assuming the value of Se/St as 0.35, we get;
Se = 0.35 * 0.024103 = 0.008436 m2.
3.15) Vertical Tail Sizing
Since the vertical tail is placed on the horizontal tail, the root chord and the tail-moment arm of the
vertical tail is same as that of the horizontal tail.
Crvt= 0.06943 m
TMA = 0.306841 m
Area of vertical tail is given by, Svt=
Page
29
Where, Cvt is the tail volume coefficient, taken from the table below.
Taking the value of Cvt for a sailplane, i.e. Cvt= 0.02.
Thus, Svt =
= 0.007713 m
2
Taking a taper ratio (k) for the vertical tail as 0.6, we get the value of tip chord as,
Ctvt = 0.6 * 0.06943 = 0.041658 m.
The span of the vertical tail is given by, b =
( ( ))
Thus, b is calculated to be 0.13886 m.
3.16) Rudder Sizing
A rudder area of 30% of the vertical tail area is found to optimum for a model this size.
Therefore, Sr = 0.3 * Svt = 0.3 * 0.007713 = 0.0023139 m2.
3.17) Aileron Sizing
The Aileron was sized from a group of RC Powered Glider having similar characteristics as our
aircraft;
The Aileron Dimensions are 20cm X 5cm
Figure 11: Tail Volume Ratios
Page
30
3.18) Components Selected
The aircraft is expected to be a lightweight reconnaissance aircraft and the components were selected
are listed below.
1. Global Positioning System (GPS)
2. Camera
3. Batteries
4. Motor
5. Servos
6. Electronic Speed Control
7. Transmitter and Receiver
8. Propeller
An exhaustive survey of components that meet the design requirements was carried over the internet.
3.18.1) Global Positioning System (GPS)
The GPS unit chosen is the 65CBTOOTH GPS Receiver. The specifications of the
component are as shown in the table below.
Specifications
Dimensions 75 x 42 x 16 (mm)
Weight 70 g
Battery Life 18.5 hours (full charge)
Reacquisition Time 0.1 seconds
Time log 300 hours
GPS data stored 90,000
Recharge Time 2.5 hours
Data Recorded Latitude, Longitude and Speed
Cost Rs. 2395
The 65C BTOOTH unit was chosen as it is a lightweight unit, refreshes its location every 0.1
seconds and has sufficient memory for storing position data. The data recorded can be
transferred to a computer via a USB cable and can be used with applications such as Google
Maps to trace the flight path.
Page
31
3.18.2) Camera
Two types of cameras were considered the first was the Spy Hidden DVR Micro Camera
DV and the second a 3.2MP Spy Pen Camera.
Specifications DVR Micro Camera Spy Pen Camera
Camera Resolution 720 x 480 at 30 fps 640 x 480 at 30 fps
Photograph Resolution 1600 x 1200 pixels 1024 x 768 pixels
Battery Life 60-80 minutes 120 minutes
Recording Time 1 hour Memory Dependent
Data Storage 2-16gb 2gb External Card
Cost Rs. 1200 Rs. 1250
Although the two cameras are almost identical in specifications, a pen camera is preferred as
it smaller in size, lighter and also has external storage thus making it user dependent.
3.18.3) Motor
A brushless DC motor was selected to act as the power plant of the aircraft. A brushless
motor was selected as it is more efficient, produces less heat and is more reliable than a
brushed DC motor. The motor selected was the Emax 1270/13.
Specifications
Recommended Model Weight 1000 grams
Shaft Diameter 4 mm
Weight with cables 55 grams
Dimensions 28.5 x 28.5 mm
Continuous Current 25 Amps
Maximum Thrust 800 grams
Cost Rs. 726
3.18.4) Servo Motors
Two servo motors are required to control the control surfaces namely one for the elevator and
one servo for the aileron. The servo chosen was the Power HD Servo. This servo was chosen
because of its light weight and small size.
Specifications 2 plastic gear servos and 1 metal gear servo
Weight 9 grams
Torque 1.8 kg-cm
Speed 0.12 sec/60
Size 22.5 x 11.5 x 24.6 mm
Cost Plastic Gear: Rs 275
Meatl Gear: Rs 480
Page
32
3.18.5) Propeller
The diameter of the propeller was calculated to be 9 inches. Since the aircraft requires a high
torque during takeoff, a propeller of diameter 8 and a pitch of 4 taken, also this specification
of propeller makes the motor most efficient i.e. a 8X4 propeller. APC 8X4 Propeller is
chosen
Features
High Thrust
Low Noise
Gas filled nylon for strength and durability
Rs. 225
3.18.6) Receiver
Futaba PCM FP-R138 DP
Specifications
Number of channels 8
Dimensions 64 x 35.3 x 20.8 mm
Frequency 72 MHz
Crystal 16
Weight 28 gms
3.18.7) Electronic Speed Control
E-Max ESC
Specifications Programmable ESC
Continuous Current 25 Amps
Dimensions 50x28x12 mm
Surge Current 30 Amps
Weight 31 grams
Cost Rs 1000
Page
33
FABRICATION
Page
34
4.1) Fuselage Fabrication
The fuselage is the part of the aircraft that will hold the payload. We chose to go ahead with a box
type fuselage in which all the components could be easily fit in.
We chose to build two fuselages:
1. The first one is made of Balsa
2. The second one is our lower cost fuselage made of Coroplast
4.1.1) Balsa Fuselage
Steps in Fabrication
1. The side panels were drawn on the Balsa sheet and were cut out.
2. Three plywood pieces measuring 5cmX5cm and 3mm thickness were cut out. These pieces
were used as the Motor Mount and as supports along the length of the fuselage. The two
pieces that would be places along the length of the fuselage needed to have a provision for the
wires to be threaded through. This was achieved by cutting out holes in the plywood pieces.
3. The squares were places at predetermined points and glued to the balsa cut outs with fevicol
and placed in a vice to dry overnight. Additional supports were given to the motor mount
using beading pieces. A third piece was glued in at the point where the fuselage starts to curve
upwards.
4. Two additional pieces of plywood measuring 3cmX3cm and 1cmX1cm were cut out. These
pieces were placed to help hold the gentle taper of the fuselage. The 1cmX1cm piece was
placed at the end of the fuselage thus completing the sides of the fuselage.
5. The bottom of the rectangular section is a single piece of balsa glued onto the sides. The rear
of the bottom portion is tapped with brown tape. This helps in saving weight and also helps in
accessibility of components in this section.
6. The cover of the fuselage is a flap. The reason for choosing a flap is that it provides for
accessibility to the components in the fuselage. The flap is a rectangular piece of Balsa that
has been attached to the body with the help of ribbons. The ribbons make it possible for the
flap to be opened and closed. For the rear we traced out the shape and cut out a piece of
Balsa and glued it onto the fuselage.
Building the empennage:
1. The empennage was fabricated using Balsa. The vertical tail and the horizontal tail were
drawn on the balsa sheets and were cut out.
2. The pieces were then sanded such that the leading edges were rounded and the trailing edges
were sharp.
3. The elevator was cut out from the horizontal tail piece and was attached back to the horizontal
tail with the help of ribbons. The ribbons allow for the upward and downwards deflection of
the elevator.
4. The vertical tail and the horizontal were attached using hot glue. This assembly in turn was
placed on the fuselage with a bead of hot glue.
Page
35
Figure 12: The Fuselage Sections Being Cut Out from the Balsa Piece
Figure 13:The Plywood Pieces Being Positioned Along With the Balsa Side Panels in the Vice and Being Glued Using Fevicol
Page
36
Figure 14: The curve of the aft section of the fuselage being done
Figure 15: The fuselage during fabrication placed in the vice (Top View)
Page
37
Figure 16: Leading edge of the empennage being sanded into shape
Figure 17: Fuselage after completion
Page
38
Figure 18: Fuselage with flap open
Figure 19: Fuselage with flap open
Page
39
Placing of Elevator Servo:
The servo was placed along the centreline of the fuselage on the top surface. We had to make sure that
there was enough movement of the servo arm to facilitate the corresponding movement of the
elevator.
The control line from the servo horn to the elevator horn was then bent and fitted making sure there
was enough clearance for the horn to move freely and that the control line did not interfere with this
movement.
4.1.2) Coroplast Fuselage:
Balsa as a raw material is quite expensive. As our main aim was to keep the costs for materials low
we chose to build a second fuselage using coroplast. Coroplast (Corrugated Plastic) is basically two
thin sheets of plastic with ridges in between. It is a very strong material and is quite economical to
use. It is slightly heavier than Balsa but the difference is not much to cause a major difference in the
flight performance.
Fabrication of the coroplast fuselage:
1. Three sections i.e the sides and the bottom of the fuselage were drawn onto the sheet of
coroplast as a development. This was then cut out and the places where a fold would be done
were cut such that only the top plastic layer was cut but the bottom layer remained.
2. Three plywood pieces measuring 5cmX5cm and 3mm thickness were cut out. These pieces
were used as the Motor Mount and as supports along the length of the fuselage. The two
pieces that would be places along the length of the fuselage needed to have a provision for the
wires to be threaded through. This was achieved by cutting out holes in the plywood pieces.
3. The plywood pieces were placed in similar positions as the Balsa fuselage. The only
difference was the use of hot glue to stick the plywood to the coroplast. Also we did not use
the 3cmX3cm and 1cmX1cm pieces at the tapered region.
4. The tail region was built by hot gluing the 3 pieces such that the correct taper was achieved.
5. To cover the tail region, a coroplast sheet was cut into the correct shape and tapped to the
bottom using duct tape.
6. The flap in this model is different from the Balsa model. We cut the single flap into 3
different flaps thus providing us access to the individual bays if required. Also we found that
it was necessary to remove and replace the battery connections a number of times. With a
single flap it was necessary to remove the wing every time that had to be done.
We chose to have a single small flap at the front which would provide easy access to the
battery leads without the need to remove the wing.
Page
40
Building the empennage:
1. The empennage was fabricated using Balsa. The vertical tail and the horizontal tail were
drawn on the balsa sheets and were cut out.
2. The pieces were then sanded such that the leading edges were rounded and the trailing edges
were sharp.
3. The elevator was cut out from the horizontal tail piece and was attached back to the horizontal
tail with the help of ribbons. The ribbons allow for the upward and downwards deflection of
the elevator.
4. The vertical tail and the horizontal were attached using hot glue. This assembly in turn was
placed on the fuselage with a bead of hot glue.
Placing of Elevator Servo:
Our aim was to try and make the elevator servo sit a little more flush with the fuselage surface
as compared to the Balsa fuselage. We achieved this by cutting out a piece of plywood and
cutting out a slot on this in which the servo would fit into. This piece in turn was hot glued to
the inside of the tail coroplast section.
The servo sat much more flush to the surface and at the same time with enough clearance to
prevent any interference from the elevator control line-servo horn assembly.
4.2) Wing Fabrication
4.2.1) Material
The material chosen to build the wing was High Density Foam. The reasons for choosing this material
to build the wing are:
1. Foam as a construction material is very light
2. It is comparatively easier to work into the complex air foil shapes than balsa
3. It is highly durable once given the necessary treatments which will be explained later
4. It is an easily available material and is very economical
We had to find a way to cut the air foil shape from the foam blocks. On doing some research we
found that the most effective method of cutting foam is using a Hot Wire Cutter.
4.2.2) Hot Wire Cutter
A Hot Wire Cutter basically uses an electric current to heat a wire under tension. When this wire is
passed through the foam the wire cuts the foam.
Fabrication of Hot Wire Cutter
We chose to build the Hot Wire Cutter using cost effective and easily available materials.
Materials Used:
Plywood (5mm thickness)
Compression Springs
Guitar String
Nails and Screws
Page
41
Steps in Fabrication:
We first cut three pieces of plywood.
o Two pieces measuring 30cm X 5cm
o One Piece measuring 100cm X 5cm
These were arranged in the shape of a U such that the longer piece forms the bridge and the
two smaller pieces form the legs. They were fastened in such a way that the hinge provided
for motion
A string was drawn between the free ends of the smaller pieces. Provision was given for wire
leads to be attached to the string.
We then hammered nails near the hinge on which the compression spring would be attached.
The spring keeps the string in tension and also provides strength to the entire assembly.
We also gave a provision for changing the tension in the string by providing two different
positions for the spring. This helped us change the tension if required.
The leads from the string are connected to an adaptor which in turn are connected to a wall
socket
Page
42
Figure 20: Hot Wire Cutter
Page
43
4.2.3) Steps in Fabrication of Foam Wing:
1. The airfoil coordinates were taken from the UIUC online database. These coordinates were in
turn fed into Solid Works after multiplying the values with the predetermined chord length
and a curve was drawn. The curve was then extruded to get a solid. On converting the Solid
from 3D to 2D, one of the views gives the airfoil profile. A print out of the air foil was taken.
2. The airfoil print out was then stuck onto a sheet of 3mm plywood and the sheet was sanded
down to give the shape as close to the airfoil outline as possible. Two of these were made.
3. A number of markings were made on the templates. These markings help provide a reference
during the cutting process making sure that the two persons operating the hot wire are at the
same point during the cutting process.
4. The two templates are placed on either side of the foam block and stuck to it using fevicol.
The Hot Wire is then inserted and made to run along the templates from the leading edge to
the trailing edge and is removed at quarter chord.
5. The excess foam is broken off and the wing is removed. The wing now has the two plywood
templates stuck on either side. These are then removed using a blade.
6. A groove was to be cut into which the spar would sit. This is done again using the hot wire.
We mark off the outline of the spar on either side of the cut foam wing. The hot wire is
lowered and follows the outline drawn thus creating the groove for the spar to sit in.
7. The carbon fibre spar is then taken and fevicol is applied on three sides of the spar. This is
then slid into the groove and a slight pressure is applied to keep it in place. The groove is then
covered with a layer of paper to help give a neat finish to the top surface of the wing.
8. The section where the fuselage is to seat is marked off. This is to place the servo along the
centre line of the wing. A groove of 4.5cmX3.5cm is shaved off the wing. Into this a plywood
piece in which a cut out for the servo has been done is placed and fixed in place using fevicol.
9. Once the aileron position is chosen, a slot is cut in the wing for the aileron to sit.
10. Application of MonoKote:
MonoKote is commercially available light weight plastic shrink wrap film available
in various colour schemes with an adhesive on one side, used to cover and form the
surfaces of a model aircraft.
The MonoKote is cut into shape such that is forms a wrap around the wing and is then
applied with the help of a hot iron. The adhesive on one side is heat activated. Once
the layer sticks to the surface a different temperature is set on the iron, this is to
shrink to layer onto the wing.
11. The aileron is made of balsa wood. The aileron is placed on the foam wing and taped to it in
such a manner that it is free to move up and down.
Page
44
12. The last step in the fabrication of the wing is placing the servo and attaching the control rods
from the servo to the ailerons. We chose a simple system in which a single servo is used to
control both the ailerons. When one aileron is pushed down the other is pulled up. The control
rods are simple cycle spokes that have been bent in such a manner to achieve the movement
necessary.
What we learnt using the Hot Wire Cutter?
It was a first time experience for the team building and using the hot wire cutter and we learnt a
number of things while using it. As the process was carried out we found a number of ways to make it
faster and make the finish better.
A number of challenges and how we overcame them have been listed below:
During the course of fabrication we first used balsa as the wood to make the templates. On
carrying out the process we found out that the hot wire started to eat into the balsa thus
getting stuck in the template itself. The wing that we got first had a very bad finish and was
discarded. We then tried out the same using plywood and found that the wire glided smoothly
on it and thus we choose to go with plywood to make the templates.
In the first few wings we faced the problem of a bow along the trailing edge. After a number
of wings were cut we found that the cause for the problem was that the middle portion of the
wire tends to move slower than the extremes thus causing the bow. The problem was rectified
by moving beyond the trailing edge of the template and staying in the foam for 5 seconds thus
giving enough time for the wire to take up a straight shape.
While cutting the wing we faced the problem of uneven heating along the length of the wire.
The cause of the problem was found to be in the method we had connected the leads to the
wire. We changed this and found that the wire heated evenly.
While cutting the groove for the spar we found that at the centre portion of the wing the
groove was very shallow but at the ends it was very deep. We tried raising the middle portion
and cutting the groove. This proved to work but we required a number of passes and had the
problem of the wire cutting all the way through the foam.
We found out that the best solution was to move the hot wire very slowly. This once again
helps the natural bow that is formed in the wire to come back to the straight line
configuration. Once the first cut is made, the cutter is kept at the bottom of the groove for 5
seconds and then moved up slowly.
With every wing that we made we were able to get a much better finish and were able to get a finished
wing much faster.
Another major problem that we had to overcome was how to prevent the rubber bands which hold the
wing in place on the fuselage from eating into the foam?
The solution that we arrived at is a simple one. We used a slightly think plastic sheet and wrapped it
around the central portion of the wing where the rubber bands would be placed. The sheet was hot
glued into place. The hot glue provided additional strength to this sheet in turn preventing the rubber
bands from eating into the foam wing.
The first wing that we made took not less than three days but as we kept making wings we learnt a
number of things and also were able to implement a number of methods to help increase our
efficiency of production. At the end we were able to make a whole wing right from printing out the
shape to attaching the servos in One day.
Page
45
Figure 21: The plywood template being placed on the foam block
Figure 22: The foam cutter being run on the template. Cutting the leading edge of the wing
Page
46
Figure 23: The foam cutter being run on the template. Cutting the trailing edge
Figure 24: Breaking away the excess foam around the cut wing
Page
47
Figure 25: the wing being removed from the block
Figure 26: The cut wing removed and placed on a table
Page
48
Figure 27: Applying the Monokote layer using the hot iron
Figure 28: A number of attempts to get the correct linkage between the Aileron Servo and the Ailerons
Page
49
Figure 29: Placing the Plastic protective sheath around the wing to hot glue into place
Figure 30: Completed Wing (Only MonoKote application left)
Page
50
5) Glider Tests
We carried out a number of glider tests in order to determine and check a number of parameters:
Whether the tail size was adequate enough to provide stability to the aircraft
To check if the wing could sustain the impact of a belly landing
To check if the foam was a good material to absorb the impact of a belly landing
We built a 1:1 scaled wing using the foam and a 1:1 scaled empennage using coroplast. These were
hot glued onto a stick which represented the fuselage.
5.1) Glider test without a spar
The first test was carried out without a spar in the wing. On impact the wing broke and this suggested
that the placement of a spar in the wing was compulsory.
Figure 31: Broken wing without spar
5.2) Glider Tests with Balsa Spar
The second set of tests was carried out with a new wing having twin Balsa spars and wrapped with
brown tape. We found that the wing with the twin spars absorbs the impact very well and the only
damage that resulted from the landings was a small chipping of the foam on the trailing edge.
Page
51
5.3) Glider tests with Carbon Fibre spar
The third set of tests was carried out with a single carbon fibre spar placed at quarter chord. The spar
gave immense strength to the wing and was clearly better than having a double balsa spar. Once again
the only problem was the slight chipping of the foam on landing impact. This could be easily
prevented by giving a layer of protective coating on the surface of the foam.
The final set of tests was carried out with a wing which had a carbon fibre spar and a layer of
MonoKote applied on its surface. This solved the problem of the trailing edge chipping on landing.
We decided to go ahead with this form of the wing.
Figure 32: Glider with full scale wing and empennage in flight
Page
52
FLIGHT TESTS
Page
53
6) Maiden Flight
Date: 3rd
May 2011
Time: 07:30
Location: NAL grounds
Weather Conditions: Moderate Winds, Overcast conditions
6.1) Setup
1. Wing Span= 95cm
2. 1300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
6.2) Summary
This was the first time we were flying our aircraft. Our main aim was to take-off and land.
We wanted to check if the aircraft was air worthy and if the entire setup would work.
It was also the first ever flight for our pilot
6.3) Flight Path
1. To Take-off at full throttle
2. Turn
3. Land without damaging the model
6.4) Objectives Achieved
1. The take-off was achieved successfully
2. Turn and glide were achieved successfully
3. Landing was perfect
6.5) Duration of Flight - 21 seconds
Page
54
6.6) Comments
Form our first flight we were able to infer the following:
The aircraft took off at a very steep R/C. Thus the motor was switched off at the peak of
ascent.
The aircraft began an unpowered glide covering 2 circuits of the ground showing that the
aircraft has very good glider characteristics.
The aircraft landed smoothly without any damage. The landing was not entirely a smooth
touch down but we managed to land it successfully. The foam layer that we had added for
protection at the nose of the aircraft had done its job well. In fact on inspection we saw that
the foam layer had taken the impact and that there was no damage on the balsa fuselage.
6.7) Damage Reported
There was no damage as such to the aircraft. Only the foam layer that had been added for
protection had taken sum mud on its surface which was a clear indication that the aircraft
landed on the layer.
Page
55
Figure 33: The NAL Grounds where the flight test was carried out
Figure 34: The aircraft taking off by hand launch
Page
56
7) Flight Test Number 1: First Flight with Coroplast
Fuselage
Date: 5th May 2011
Time: 16:30
Location: Disused Test Track
Weather Conditions: Moderate Winds
7.1) Setup
1. Wing Span= 95cm
2. 1300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
7.2) Summary
This was the first flight of the coroplast Fuselage model. Our main aim was to check if there
were any changes brought about due to change in the Fuselage material from traditional Balsa
to coroplast. The coroplast fuselage is slightly heavier than the Balsa model. Also this was the
first flight in moderate wind conditions in an open field.
7.3) Flight Path
1. To Take-off at a medium rate of climb
2. Carry out a Left Aileron turn
3. Trim the control surfaces in flight
4. Carry out a complete circle
5. Carry out a Straight in approach
6. Try a smooth landing
7.4) Objectives Achieved
1. The take-off was achieved successfully
2. Left Aileron Turn
3. Trimming was carried out during the flight
4. The circle was successfully achieved
5. Lining up with the runway was done successfully
Page
57
7.5) Duration of Flight - 1 minute
7.6) Comments
From this first flight we learnt the following:
During launch the aircraft must be held such that the orientation of the wings is parallel to the
ground. As we near the launch velocity the aircraft starts to lift off and the person launching
must simply let go of the aircraft and MUST NOT try and push it into the air
The control surfaces are adequate and provide a good amount of control for roll and pitch
movements of the aircraft.
The control surfaces need to be trimmed in the first flight. This is because of the removable
wing. Every time the wing is mounted and dismounted (for transportation), there is a need to
remove the servo horn. This in turn causes a change in the Neutral Position of the control
surfaces. A certain amount of setting can be done on the ground by visual reference but the
actual feel for the controls can be got only in flight, thus the trimming has to be carried out in
flight.
Once trimmed the aircraft is very stable. We were able to achieve a complete 360 degree
aileron turn. The turn was a large radius turn.
The aircraft had to be given additional throttle during the turn as it tends to loose altitude as it
carries out the maneuver.
Lining up for landing proved to be the most challenging part of the flight as this was carried
out for the first time. The aircraft is made to gain altitude and made to point towards the
runway. The throttle is brought to Zero
As the aircraft comes closer to the ground the attitude control was given through inputs to the
elevator causing the aircraft to flare.
The landing was not entirely a smooth touch down but we managed to land it successfully.
7.7) Damage Reported
There was no damage as such to the aircraft; there were slight bruises that were purely
superficial. The following was noted:
The wing had displaced slightly forward
No damage to the Empennage
No damage to the Fuselage
A complete check of all the servos and the motor was carried out and No damage was
noted.
Page
58
Figure 35: The team setting up the model before flight
Figure 36: Aircraft being launched and pilot with remote
Page
59
8) Flight Test Number 2: Acrobatics and Manoeuvrability
Test
Date: 5th May 2011
Time: 17:00
Location: Disused Test Track
Weather Conditions: Moderate Winds
8.1) Setup
1. Wing Span= 95cm
2. 1300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
8.2) Summary
This was the second flight of the coroplast Fuselage model. Our aim in this flight was to
check the durability of the aircraft by putting it through high G turns and through few
acrobatic manoeuvres. We also wanted to check how effective the rubber bands were in
holding the wing in position by putting the wing through this highly demanding test.
8.3) Flight Path
1. To Take-off at a High rate of climb
2. Carry out a sharp Left Aileron turn and level off
3. Carry out a complete 360 degree turn
4. Carry out a tighter 360 degree turn
5. Level off
6. Clock wise direction loop
7. Sharp 180 degree turn
8. Anti-clock wise loop
9. Line up and perform a Straight in approach Landing
8.4) Objectives Achieved
1. The take-off was achieved successfully
2. Sharp Left Aileron Turn
3. 360 degree turn
4. Tighter 360 degree turn
5. CW loop
6. 180 degree turn
7. Anti-clock wise loop
Page
60
8. Straight in approach landing partially successful
8.5) Duration of Flight: 1.10 minute
8.6) Comments
The aircraft is very manoeuvrable and is able to take sharp turns quite easily. The loss in
altitude during the sharp turns is kept under control by increasing the throttle.
The aircraft was able to pull both directional loops with ease and it was easy to get it back in
control.
The rubber bands held the wing in position during the flight. There was no shifting of the
wing during the flight.
8.7) Damage Reported
There was no damage as such to the aircraft; there were slight bruises that were purely
superficial. The following was noted:
The wing had not displaced on this landing
Slight superficial damage to the Empennage
No damage to the Fuselage
A complete check of all the servos and the motor was carried out and No damage was
noted.
Figure 37: Aircraft in flight
Page
61
9) Flight Test Number 3: Heavy Cross Winds with
Aborted Landing
Date: 5th May 2011
Time: 17:15
Location: Disused Test Track
Weather Conditions: High Cross winds
9.1) Setup
1. Wing Span= 95cm
2. 1300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
9.2) Summary
This was the third flight of the coroplast Fuselage model. Our aim in this flight was to fly the
sorties that we would be doing during an aerial tracking mission. The flight would test the
ability of the aircraft to fly straight line paths at a level attitude and at the end of the run carry
out a turn and repeat the flight in the opposite direction a slight distance offset from the first
run.
9.3) Flight Path
1. To Take-off at a moderate rate of climb
2. Carry out a Left aileron turn
3. Fly a straight path
4. Carry out a tight 180 degree turn
5. Fly a straight path
6. Carry out a tight 180 degree turn
7. Fly a straight path
8. Line up for a landing
9. Attempt a flared, kiss landing
9.4) Objectives Achieved
1. The take-off was achieved successfully
2. Left Aileron turn
3. Sortie of straight line fly-by’s followed by the turns
4. Line up
5. Successful touch down
Page
62
9.5) Duration of Flight: 2.30 minutes
9.6) Comments
The aircraft is very manoeuvrable and was able to achieve the sortie easily.
On landing approach the aircraft faced a strong crosswind. The effect of the gust was to roll
the aircraft CW direction. The pilot tried to put the nose into the incoming wind in order to
perform a Crab Landing but the gust was too strong and blew the aircraft off course. He
managed to line it back up but just 10 feet above the ground the aircraft faced yet another
crosswind gust throwing the aircraft out of the line up once again.
We were able to power up and gain altitude, finish a circuit and line up again and land
successfully. This clearly proved that the motor produces enough lift to help the aircraft climb
even at very low airspeeds.
9.7) Damage Reported
There was no damage as such to the aircraft
The wing had not displaced on this landing
No damage to the Empennage
No damage to the Fuselage
A complete check of all the servos and the motor was carried out and No damage was
noted.
Figure 38: Aircraft facing a strong crosswind on landing approach
Page
63
10) Flight Test Number 4: Wing Failure and First
Crash
Date: 5th May 2011
Time: 17:30
Location: Disused Test Track
Weather Conditions: Heavy Wind Conditions
10.1) Setup
1. Wing Span= 95cm
2. 1300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
10.2) Summary
This was the fourth flight of the coroplast fuselage model in one day. This was to subject the
aircraft to rugged use by continuously taking off and landing in short duration flights.
10.3) Flight Path
1. To Take-off at a moderate rate of climb
2. Carry out a Left aileron turn
3. Carry out a number of circular sorties
4. Line up with the runway
5. Land
10.4) Objectives Achieved
1. The take-off was achieved successfully
2. Left Aileron turn
10.5) Duration of Flight: 0.50 minutes
Page
64
10.6) Comments
The weather conditions got worse after take-off. There were strong guts that were blowing the
aircraft making it extremely difficult to control. The pilot tried to bring the aircraft back in for
a landing but wasn’t successful in doing so
While flying into the wind the aircraft tended to pitch up and stall in spite of throttling up to
100%. The reason was the strong head winds that were hitting the aircraft.
While attempting the final sortie, the aircraft stalled at a high AoA. From the ground a flutter
was visible on the right wing. We immediately realized that the wing had failed. The aircraft
crashed and the chase crew was sent out to recover the aircraft.
10.7) Damage Reported
The following was noted on recovery:
The rubber bands that hold the wing had slipped from its support and had eaten into
the foam all the way till the carbon fibre spar. This had caused the wing to turn
around the spar. This was the flutter that was visible from the ground.
The Aileron servo had lost one of the mounting screws.
Empennage had superficial damage.
No damage to the Fuselage
Figure 39: the rubber band has eaten half way into the foam wing. The left rubber band has been put back into position
Page
65
Figure 40: the wing could be actuated about the carbon fibre spar. This is why the flutter was seen from the ground
Figure 41: the missing Servo screw.
Page
66
10.8) Analysis of the Crash
We carried out a detailed examination of the crash in order to find the reason why it had occurred and
find a solution to prevent it from occurring in subsequent flights
From our study we found two main reasons as to how the crash had been caused:
1. The Aileron servo had lost one of its two mounting screws. This could have caused an
unbalanced force on the ailerons which in turn would have caused excess forces on the wing
and displaced it from its position. This in turn would have caused the rubber bands to slip and
eat into the foam causing failure of the wing
2. The second reason was that the rubber band had slipped from its position and eaten into the
foam wing. This in turn would have caused the flutter of the wing. The flutter in turn would
have pulled on the control rods of the aileron servo and caused a pulling and pushing force on
it. This in turn caused the servo to move and pulled out the servo mounting screw.
Of the two reasons the second one seems more likely.
10.9) Changes in Design
After the crash we made a few changes in the design to prevent the same problems from occurring
again:
1. The size plastic that we wrap around the central portion of the wing was increased from a
span of 10cm to 20cm in order to make sure that there is no way the rubber bands can slip.
2. The Aileron servo mount material was changed from Indian Balsa to 3mm plywood. Also a
layer of hot glue is applied on the surface of the plywood. The two layers ensure that the
servo is held tight and secure.
Page
67
11) Flight Test Number 5: Gusty Weather Flight
Date: 15th May 2011
Time: 15:45
Location: Disused Test Track
Weather Conditions: Overcast Skies, High Velocity Gusty Winds
11.1) Setup
1. Wing Span= 85cm, High Aspect Ratio
2. 2300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
11.2) Summary
The main aim of the test was to check if the aircraft structure can withstand the extremely
gusty winds and also to evaluate the flight dynamics of the aircraft in these conditions
11.3) Flight Path
1. To Take-off at a medium rate of climb
2. Carry out a Left turn
3. Take a circuit above the runway
4. Land
11.4) Objectives Achieved
1. The take-off was achieved successfully
11.5) Duration of Flight: 3 seconds
Page
68
11.6) Comments
1. The aircraft levelled off, elevator control was lost abruptly and the aircraft went into a
shallow dive.
2. Crash landed on the runway
11.7) Crash Analysis
1. As soon as the launcher released the aircraft, a side gust shifted the wing, making it skew
with respect to the fuselage.
2. The trailing edge of the wing jammed the elevator servo, thus fixing the elevator in one
place.
3. This caused the aircraft to go into a shallow dive
11.8) Damage Reported
1. The wing had displaced from its position, but was structurally alright
2. The coroplast fuselage absorbed the shock of impact well and did not show any sign of failure
3. The propeller shattered into 2 fragments
11.9) Changes to Design: None
Page
69
12) Flight Test Number 6: First Long Endurance
Flight
Date: 13th May 2011
Time: 12:00
Location: Disused Test Track
Weather Conditions: Clear Skies, Low Winds
12.1) Setup
1. Wing Span= 85cm, High Aspect Ratio
2. 2300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
12.2) Summary
This was the first flight with the high aspect ratio 85 cm wing. The main aim of the flight was
to fly for 5 minutes, the longest endurance flight till date.
We wanted to check how much the battery would drain by during the flight, check by how
much the components inside the aircraft heat up during a long flight and also check how the
aircraft performs during long duration flights.
12.3) Flight Path
1. To Take-off at a medium rate of climb
2. Carry out a Left Aileron turn
3. Trim the control surfaces in flight
4. Carry out circuits for the 5 minute duration
5. Carry out a Straight in approach
6. Smooth Landing
12.4) Objectives Achieved
1. Flight duration of 5 minutes was achieved
2. The take-off was achieved successfully
3. Left Aileron Turn
4. Trimming was carried out during the flight
5. A number of circuits were carried out
6. Lining up with the runway was done successfully
Page
70
12.5) Duration of Flight: 6 minutes
12.6) Comments
From this first flight we learnt the following:
The aircraft performs well on long duration flights. The pilot was comfortable flying the
aircraft for the long duration. He did not feel the need to continuously give input to the
aircraft thus proving it to be stable which is an advantage for long duration flights as it helps
prevent pilot fatigue from setting in.
For most of the flight we were able to fly at 75% throttle.
The battery and the other electronic components heated up normally. No overheated
components were noted.
The lining up and the landing were carried out successfully.
While landing the aircraft hit a low bush. The impact was on the right wing. When checked it
was noted that no damage had been sustained. The foam wing had absorbed the impact very
well.
12.7) Damage Reported
There was no damage as such to the aircraft in spite of the wing hitting the bush. The
following was noted:
The wing had displaced slightly at an angle. This was a result of the impact into the
bush. The wing was put back into its correct position immediately with no effort at
all.
No damage to the leading edge which clearly shows that the foam wing is ideal for
impact absorption
No damage to the Empennage
No damage to the Fuselage
A complete check of all the servos and the motor was carried out and no damage was
noted.
Page
71
13) Flight Test Number 7: Flight Test for
Manoeuvrability
Date: 13th May 2011
Time: 12:20
Location: Disused Test Track
Weather Conditions: Clear Skies, Low Winds
13.1) Setup
1. Wing Span= 85cm, High Aspect Ratio
2. 2300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
13.2) Summary
The main aim of the test was to check the aircrafts manoeuvrability by making it to carry out
a “Figure of 8” turn followed by a number of circles each lesser in radius. These tests help us
determine the shortest turn radius of the aircraft and help the pilot gain knowledge on how the
aircraft performs and responds while carrying out the manoeuvres.
13.3) Flight Path
1. To Take-off at a medium rate of climb
2. Carry out a Left Aileron turn
3. Carry out a Figure of 8 Turn
4. Try a Zero Radius Turn
5. Carry out a number of circular circuits each with a smaller radius
6. Smooth Landing
13.4) Objectives Achieved
1. The take-off was achieved successfully
2. Left Aileron Turn
3. Two Figure of 8 turns were carried out
4. Zero radius turn was attempted
5. Short radius circuits were carried out
13.5) Duration of Flight: 2.30 minutes
Page
72
13.6) Comments
From this first flight we learnt the following:
The aircraft carried out the Figure if 8 turn with ease.
A zero radius turn was attempted. In order to carry out the turn, the pilot needs to cut back on
the throttle, give a nose up moment through the up elevator and give a full directional aileron.
The resulting forces cause the aircraft to pitch up and roll.
The problem with this maneuver is that the aircraft loses altitude. The turn was attempted and
the aircraft did respond to the inputs and the turn was partially carried out but the aircraft
started to lose altitude so preventive action was taken, the turn was aborted and a circuit was
carried out.
A number of turns were carried out and each of the turns had a smaller radius as compared to
the previous turn. The aircraft handled and responded well.
The lining up and the landing were carried out successfully. The throttle was cut off after
lining up and the aircraft flared about 15 feet above the ground and landed in a perfect
landing.
13.7) Damage Reported
There was no damage to the aircraft.
Page
73
14) Flight Test Number 8: First Flight in PESIT with
On-board Camera
Date: 16th May 2011
Time: 13:00
Location: PESIT
Weather Conditions: Clear Skies, moderate Winds
14.1) Setup
1. Wing Span= 85cm, High Aspect Ratio
2. 2300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
5. On board camera
14.2) Summary
The main aim of the test was to fly our first flight over PESIT. The additional payload on this
flight was the pen camera. We wanted to try and take a video from the aircraft of the college
campus in order to retrieve few aerial pictures
14.3) Flight Path
1. To Take-off at a medium rate of climb
2. Carry out 2 circuits of college
3. Line up and carry out a Smooth Landing
14.4) Objectives Achieved
1. The take-off was achieved successfully
2. The circuits were successful
3. A smooth landing was achieved
4. On board camera successfully recorded a video and images were retrieved.
14.5) Duration of Flight: 2.30 minutes
Page
74
14.6) Comments
Through this flight we were able to conclude the following:
1. That the pen camera is good enough for the aerial photography that we wanted to achieve.
The video quality was good.
2. The camera placement provided a clear view of the ground and there were no hindrances
during the flight.
We noted that the camera tends to shake when the aircraft is throttled up.
14.7) Damage Reported
There was no damage to the aircraft or the camera.
Page
75
Pictures of the college obtained from the on-board camera after processing:
Figure 42: PESIT Garden and Fountain
Figure 43: Professor M.R.Doreswamy Silver Jublee Block (A- Block)
Page
76
Figure 44: Department of Mechanical Engineering (C-Block)
Figure 45: F Block (left) and Department of Electrical and Electronics Engineering (Right)
Page
77
Figure 46: Tech Park (E-Block)
Figure 47: Boys Hostel blocks
Page
78
Pic:
Figure 49: Stitched image showing the new football ground and a part of the cricket ground
Figure 48: Stitched images showing A-block, the fountain, entry way and the Department of Mechanical Engineering, motorcycle parking in a single frame
Page
79
15) Flight test number 9: 20 Minute Flight
Date: 17th May 2011
Time: 11:00
Location: Disused Test Track
Weather Conditions: Clear Skies, No Winds
15.1) Setup
1. Wing Span= 85cm, High Aspect Ratio
2. 2300 mah Battery
3. Coroplast Fuselage
4. Wing fixed by Rubber Bands being wrapped around the Fuselage
5. Camera on Board
15.2) Summary
The objective of this test flight was to see whether the aircraft with this configuration can match the
project requirement of 20 minutes flight time. The aircraft was to be flown just like it would on a real
mission in very large oval shaped patterns and with very gentle turns.
15.3) Flight Path
1. To Take-off at a medium rate of climb
2. Carry out a Left Aileron turn
3. Trim the control surfaces in flight
4. Carry out circuits for the 20 minute duration
5. Carry out a Straight in approach
6. Smooth Landing
15.4) Objectives Achieved
1. The take-off was achieved successfully
2. Left Aileron Turn
3. Trimming was carried out during the flight
4. A number of circuits were carried out
5. Flight duration of 20 minutes was achieved
6. Lining up with the runway was done successfully
7. Very smooth soft belly landing
15.5) Duration of Flight: 20 minutes and 36 seconds
Page
80
Figure 50: Aircraft taking off
Page
81
Figure 51: Aircraft on final approach
Figure 52: Aircraft levelling off
Page
82
Figure 53: Aircraft attempting Flare
Figure 54: Aircraft after landing
Page
83
15.6) Comments
1. The aircraft matched the project requirement of 20 minute flight time.
2. The flight was carried out with a camera on board.
3. The aircraft was successfully trimmed to fly stick free
4. The aircraft can sustain itself at about 52-53% thrust
5. There was no loss in power for the duration of the flight, i.e. the throttle setting did not
need to be changed once the aircraft was trimmed.
6. The aircraft is very stable when flying in a straight line.
15.7) Damage Reported: None
The team with the aircraft after the successful 20 minute flight
Page
84
16) Comparison of Google Earth Snapshots with Snapshots Taken From the P❺
The photographs retrieved from the on board camera were compared to
images from Google Earth. We carried out one trial flight with a GPS
system on board. The photographs below show a part of the flight path and
where a snapshot was taken by the UAV, on Google Earth.
Figure 55: Snapshot (12.97108, 77.67567)
Page
85
Figure 56: Snapshot (12.560668, 77.327044)
Page
86
Figure 57: Snapshot (12.55549, 77.324981)
Page
87
17) What Makes the P❺ Different?
The USP of our model is its base cost. Since the aircraft is either made of coroplast or balsa,
and not an expensive, exotic material such as Kevlar or carbon fibre, the base cost of the
model as a whole comes down drastically. A lot of the materials used to build the aircraft
were not specialized aeromodellers’ materials, but things that we adapted such that they
served the purpose. For example, the wing coating where the rubber bands sit is usually
coated with a layer of fibre glass. This gives a very strong smooth finish, but is very
expensive and also has a very large weight penalty. We used a stick file to do the same job,
thus essentially reducing the cost of coating from about 400 rupees to 10 rupees, while having
a lower weight penalty. Of course, the strength provided by the stick file is much lower than
that of the glass fibre, but the strength provided was enough. We have used this same
approach a number of times in numerous places, thus effectively lowering the cost of the
aircraft.
As part of our literature survey, we looked at the cost of similar sized UAVs in the market.
One of the aircraft we found was a low cost mini UAV called Featherlite, manufactured by
Aeroart. This low cost UAV has a wingspan of 1.9m and has an endurance of 1 hour. It costs
5,03,700 Indian rupees (7900 Euros).
The cost break up of our aircraft with an autopilot (Future Work) integrated is as given below
The following is the cost estimate for this aircraft if it is to be sold as a kit:
The aircraft is available in two specifications:
o Balsa fuselage
o Coroplast fuselage
Both the kits will come with the same equipment but would differ only in the fuselage
material and hence their costs
17.1) Cost Split Up:
1. Electronics:
Component Quantity Cost (Rupees)
Tipple 20C 2300 mah 3S 1 1450
EMAX ESC 25A 1 1000
EMAX Grand Turbo
Motor GT2210/13
1 725
Futaba Tx/Rx 4Ch 1 6000
Servo Plastic Gear 2 550
Servo Metal Gear 1 480
3.5 mm Gold Connectors 2 90
TOTAL 10,295
Page
88
2. Raw material:
o Balsa Fuselage:
The Balsa fuselage requires two sheets of Balsa measuring 1m X 10cm.
Each sheet costs Rs 350. In addition, half a sheet of Balsa is required to build
the Empennage.
Plywood reinforcement at 3 sections along with the motor mount = Rs 50.
Thus material cost for fuselage = Rs 925
o Coroplast Fuselage:
The coroplast fuselage requires sheet of coroplast measuring 60cm X 50cm.
This sheet would approximately cost Rs 50.
Plywood reinforcement at 3 sections along with the motor mount = Rs 50.
The coroplast model also would require half a sheet of Blasa costing Rs 175,
Thus the total cost for the Coroplast fuselage = Rs 275
Foam:
Both the models require foam for building the wing. The approximate cost for foam to
build a wing is around Rs 50
3. Additional Components:
Components Cost (Rupees)
Carbon Fibre Rod 200
Horns and Clevis 25
MonoKote, 2 colours 200
Propeller (2 nos) 180
Cycle Spokes (4 nos) 10
TOTAL 615
4. Miscellaneous Items:
Item Cost (Rupees)
Glue 100
Double Sided Tape 10
Cutter 25
Plywood Sheet (3mm) 50
TOTAL 185
Fuselage Type Balsa Coroplast
Cost (Rupees) 12070 11420
Page
89
The cost of the aircraft if it is to be sold as a Ready to Fly (RTF) kit is approximately 11000
rupees. This places our coroplast model very competitively in the trainer aircraft class of
remote controlled aircraft.
Another aircraft with specifications similar to ours can be found at the following address:
http://www.jackshobbies.in/products_big.aspx?imgid=1061
The cost breakup of the components if the P❺ was to be converted into a fully-fledged UAV
is as given below
Cost of Camera = Rs 1250
Cost of GPS = Rs 2900
Autopilot = Rs 18,900 (400 USD)
UAV Specific PDA = Rs 50,000
Fuselage Type Balsa Coroplast
Cost (Rupees) 85,120 84,470
As mentioned above, The Featherlite manufactured by Aeroart costs 5,03,700 Indian rupees
(7900 Euros).
The above estimate shows that the cost of our UAV would be less than a fifth that of the
Featherlite. Inspite of having a lower endurance, the fact that our UAV is more compact and
cheaper would place it above the Featherlite when it comes to non-military operations such as
disaster management, vehicular movement tracking updates and animal radio collar tracking.
Page
90
18) Future Work
18.1) Autopilot
Every UAV is armed with an autopilot. The autopilot enables the operator to fly the aircraft by only
inputting target coordinates on a computer. The autopilot also assists in stabilizing the aircraft and
optimizing the various systems onboard the UAV. The cheapest quality UAV autopilot available
today is an open source autopilot whose code is available online called ARDUPILOT from
www.diydrones.com. This autopilot costs roughly 18000 rupees and provides both in flight
stabilization and GPS navigation.
Figure 58: Autopilot chipset
18.2) Live telemetry and Video feed
Our aircraft records video and GPS tracking data onboard and this data is recovered when the aircraft
lands. A UAV’s current position needs to be known to the operator while it is in flight, along with a
live video feed of the area it is flying over. The telemetry (tracking) part is taken care of by the
autopilot. The video feed is an optional upgrade with the ARDUPILOT, but costs approximately 5000
rupees more.
Page
91
18.3) Extension of Flight time
Improvements in the aerodynamics of the aircraft by making it more streamlined, adding appropriate
wingtips, designing a specialized airfoil for our application.
Use of exotic materials such as composites to lower the weight of the structure as well as strengthen it
more.
On board system managers that optimize the energy usage.
18.4) Portability
The whole aircraft along with its controller station needs to be made portable since the range of the
aircraft is limited. Due to this short range the aircraft needs to be taken close to the area that needs to
be scanned and then launched. This means that the operator would have to carry it to such a location.
Thus the design, lightening and strengthening of all the controller and its subsystems needs to be done
keeping this in mind.
Page
92
19) Conclusion
The challenge of designing, fabricating and flying a mini unmanned aerial vehicle for at least
20 minutes has been achieved.
Over the course of 2 months, 2 separate designs were created on paper and their gliders were
evaluated. The aircraft chosen was then fabricated over the period of a month and the aircraft
first flew on the 10th
of May, 2011 for 18 seconds.
Subsequently a number of flight tests were carried with various configurations to study their
effects on flight dynamics while the aircraft was flying. Each flight pushed the known limit of
the aircraft a little more, whether it was the flight time or the structural strength.
The design objectives of the project were achieved on the 17th
of May, 2011 when the aircraft
flew non-stop for more than 20 minutes.
During the project apart from having fun, we learnt a number of things.
The first and most important thing that we learnt is how to work as a team, then we
learnt how difficult it is to make something fly.
We learnt to use a number of tools for the first time, we learnt the challenges in
fabrication
We learnt how to improve upon our mistakes and we learnt the hard way the truth
behind the adage, “learn from your mistakes”.
Each day was a new challenge and a learning curve and we overcame these challenges
through hard work, team spirit and sheer determination.
This is not the end of this project, but just the beginning. The aircraft is yet to be pushed to its
utter limits, optimized to fly better, and with auto-pilot integration, our aircraft has the
potential to be the finest and cheapest unmanned flight surveillance solution to a number of
demanding situations.
Page
93
Appendix A: Software Used
SolidWorks 2010
SolidWorks is a 3D mechanical CAD program and developed by Dassault Systems. SolidWorks is
currently used by over 1.3 million designers and engineers in 130,000 companies worldwide.
SolidWorks was the CAD tool of choice for this project. All CAD models and drawings were done
using SolidWorks. SolidWorks was preferred as it has an easy to understand interface that can easily
be used by both amateurs and professionals to create CAD models of objects very easily and with a
very high degree of realism and accuracy in a very short span of time.
The SolidWorks curve wizard is unique to SolidWorks in terms of the ease with which files having
coordinates of the curves can be imported. This curve wizard was especially helpful for us, as we had
to make drawings and models of different airfoils that we were going to use. Many other CAD
software such as SolidEdge were tried but the ease and the functionality of SolidWorks scored over
all other software. The ability of the software to store the models and drawings in different formats
was also of great benefit to us.
SolidWorks is more than just a CAD tool. It can be used to carry out structural and flow anlaysis as
well as computational fluid dynamic (CFD) simulations. Real life conditions and constraints can be
applied to the model and simulated to understand the behaviour of the model.
XFLR5
XFLR5 is an analysis tool for airfoils, wing and planes operating at low Reynolds Numbers. It
includes:
XFoil’s Direct and Inverse analysis capabilities.
Wing design and analysis capabilities based on the lifting line theory, on the vortex lattice method,
and on a 3D plane method.
XFLR5 is capable of plotting an airfoil in 2D by importing the coordinates from a notepad file. This
feature of XFLR was not only made evaluation of airfoil parameters easy but also saved us valuable
time.
XFLR5 was used to evaluate airfoil parameters such as the lift vs angle of attack, the coefficient of lift
vs coefficient of drag etc. The program evaluated these characteristics at different angles of attack,
Reynolds Number and mach number. The results were represented in a graphical form, which made it
easy for us to interpret and understand the airfoil performance.
XFLR5 is available as freeware and is used by students and professionals around the globe to
understand and study the performance parameters of airfoils.
Page
94
MotoCalc
MotoCalc is a program for predicting the performance of an electric model aircraft power system,
based on the characteristics of the motor, battery, gearbox, propeller or ducted fan, and speed control.
By specifying a range for the number of cells, gear ratio, propeller diameter, and propeller pitch,
MotoCalc can produce a table of predictions for each combination.
MotoCalc can predict weight, current, voltage at the motor terminals, input power, output power,
power loss, motor efficiency, motor RPM, power-loading, electrical efficiency, motor RPM, propeller
or fan RPM, static thrust, pitch speed, and run time. By producing a table of predictions, MotoCalc
helps in determining the optimum propeller size and/or gear ratio for the aircraft.
MotoCalc can also carry out in-flight analysis for a particular combination of components, predicting
lift, drag, current, voltage, power, motor and electrical efficiency, RPM, thrust, pitch speed, propeller
and overall efficiency, and run time at various flight speeds. It can also predict stall speed, hands-off
level flight speed, throttle, and motor temperature, optimal level flight speed, throttle, maximum level
flight speed, rate of climb, and power-off rate of sink.
MotoCalc's graphing facility can plot any two parameters against any other (for example, lift and drag
vs. airspeed), making it easier to interpret performance of the aircraft.
For particular requirements, such as a minimum run time, maximum current, or maximum power loss
(which is dissipated as heat), MotoCalc's filter facility can be used to filter out the unacceptable
combinations.
As we were beginners to electric flight, MotoCalc’s MotoWizard was able to guide us and give
suggestions regarding the ideal power system for our requirements by asking a few questions about
the model and our preferences. The results of the analysis were very detailed and explained in simple
language how the aircraft and the power system would perform under different conditions.
Page
95
Appendix B: Original Design Delta Wing Plan form
500 mm Wing span
20 Minute Endurance
Page
96
Wing Loading:
The relationship between wing size, weight, and speed is embodied in the "Great Flight Diagram",
which plots weight against cruising speed shown below.
Fig: The Great Flight Diagram
Page
97
Weight Estimation by Component Breakup:
Components Weight (grams) Servos 30
GPS 70
Camera 35
Receiver 28
Batteries 100
Motor 145
ESC 25
Structure
Fuselage 72
Wing 73.575
Tail 20
Carbon fibre
2m 10
TOTAL WEIGHT 608.575
This weight is a very rough approximation of the all up weight of the aircraft. Therefore the weight
considered for design was assumed to be double this, due to factors such as reinforcement of the
structure, glue, additional components, wiring etc.
The weight of the aircraft being designed has been approximated to 1.25 Kg
From the Great Flight Diagram, we see that the weight of our aircraft comes in the range of the
Snowy Owl and the Osprey.
Considering the Osprey’s characteristic values from the graph we have:
Cruising speed ≈ 15 m/s
Wing Loading = W/S ≈ 100 N/m2
= 10.1936 Kg/m2
From the wing loading we can calculate the Wing Area (S)
= 1.250 / 10.1936 = 0.12262 m
2
Wing Span (b) has been predefined in the design criteria as 500mm,
Aspect ratio = A.R =
= 0.5
2 / 0.12262 = 2.038736
Page
98
Wing Geometry:
Now the wingspan, surface area and aspect ratio are known.
Taper ratio is the ratio of tip chord to root chord.
We assume the entire wing to be swept with a taper ratio (k) of 0.45;
This is because of structural reasons. If the taper ratio is one, the most amount of lift is produced but
due to a uniformly distributed load the wing becomes weak structurally. If the taper ratio is zero the
wing is structurally very strong but is aerodynamically inefficient since a lot of lift producing span is
lost. A taper ratio of 0.45 is the optimum value taking structural safety and lift producing ability into
account.
Root chord (Cr) =
( )
= 2* 0.12262 / (0.5 * (1 + 0.45))
= 0.338276 m
Tip chord = k * (Cr)
= 0.45 * (0.338276)
= 0.152224 m
Mean Aerodynamic Chord = MAC = (
)
= 0.667 * (0.45 + 1/(1 + 0.45)) * (0.338276))
= 0.2570 m
Lift and Drag:
Calculating Reynolds Number at the cruise speed of 15m/s ;
Re =
= (1.225* 15* 0.2570)/ (2*10-5
)
= 236129.7
Clrequired = ( ) = (1.250 * 9.81) / (0.5* 1.225* (15^2) * 0.12262)
= 0.725624
Page
99
Airfoil selection
For aircraft that operate in the region of low Reynolds number and have a requirement of high lift,
there is a series of specialized airfoils created by Michael S. Selig. These airfoils are now standard on
this size of aircraft. We have chosen the selig1210 because of its high lift and moderate drag along
with its very gentle stalling characteristics. This implies that the operator would have a large buffer
zone in which he can recover the aircraft if it approaches stall.
Fig: Cl vs Alpha Fig Cl vs Cd
For this value of Clrequired, from the graph the value of alpha initial = -3.5 Degrees
CdInduced = ( ( ) = (0.725624^2) / (3.14* 2.038736)
= 0.082249
Cf = 0 ( ( )) / (Log (2255325.43))2.58
= 0.006002
Cdw = 2
= 0.012003
Page
100
Fuselage drag calculations:
Fuselage length = 0.5m
Fuselage height = 0.06m
Fuselage width = 0.06m
Fuselage wetted area (A) = 0.075m2
Cdf =
= 0.005943*0.075 / 0.122625
= 0.003671
Overall Drag coefficient:
CdO = Cdw + Cdf = 0.011886 + 0.003671 = 0.015674
Accounting 10% more drag for interference we have;
Cd = CdO + CdInduced = 0.015674 + 0.082249 = 0.099491
Page
101
Velocity Correction:
Our initial cruise velocity of 15m/s was assumed from the great flight diagram. In the second iteration
we will find the optimum velocities for maximum endurance and range.
Velocity Cl D0 DL D Cd VSink
5 6.530612 0.028234 12.50957 12.5378 6.677229 -5.11225
6 4.535147 0.040658 8.687199 8.727857 3.227899 -4.27051
7 3.331945 0.055339 6.382432 6.437772 1.74926 -3.67498
8 2.55102 0.07228 4.88655 4.95883 1.031607 -3.23512
9 2.015621 0.091479 3.860978 3.952457 0.649676 -2.90089
10 1.632653 0.112938 3.127392 3.240329 0.431424 -2.64247
11 1.3493 0.136654 2.584621 2.721276 0.299435 -2.4411
12 1.133787 0.16263 2.1718 2.33443 0.215841 -2.28446
13 0.966067 0.190864 1.850528 2.041392 0.160825 -2.16417
14 0.832986 0.221358 1.595608 1.816966 0.123426 -2.07442
15 0.725624 0.25411 1.389952 1.644061 0.097286 -2.01108
16 0.637755 0.28912 1.221637 1.510758 0.078572 -1.97122
17 0.564932 0.32639 1.082142 1.408532 0.064891 -1.9527
18 0.503905 0.365918 0.965244 1.331162 0.054702 -1.954
19 0.452258 0.407705 0.866314 1.274018 0.046988 -1.97401
20 0.408163 0.45175 0.781848 1.233598 0.041061 -2.01198
21 0.370216 0.498055 0.709159 1.207214 0.036447 -2.0674
22 0.337325 0.546618 0.646155 1.192773 0.032812 -2.13994
23 0.30863 0.59744 0.591189 1.188629 0.029916 -2.22944
24 0.283447 0.65052 0.54295 1.19347 0.027587 -2.33584
25 0.261224 0.70586 0.500383 1.206242 0.025696 -2.45921
26 0.241517 0.763458 0.462632 1.22609 0.024149 -2.59966
27 0.223958 0.823315 0.428998 1.252312 0.022872 -2.75739
28 0.208247 0.885431 0.398902 1.284333 0.021811 -2.93262
29 0.194132 0.949805 0.371866 1.321671 0.020924 -3.12566
30 0.181406 1.016438 0.347488 1.363926 0.020177 -3.33682
31 0.169891 1.08533 0.325431 1.410761 0.019545 -3.56645
32 0.159439 1.156481 0.305409 1.46189 0.019008 -3.81492
33 0.149922 1.22989 0.28718 1.51707 0.018548 -4.08264
34 0.141233 1.305558 0.270536 1.576094 0.018153 -4.37001
35 0.133278 1.383485 0.255297 1.638782 0.017811 -4.67746
36 0.125976 1.463671 0.241311 1.704982 0.017516 -5.00545
37 0.119259 1.546115 0.228444 1.774559 0.017258 -5.35443
38 0.113065 1.630818 0.216578 1.847397 0.017034 -5.72486
39 0.107341 1.71778 0.205614 1.923395 0.016837 -6.11722
40 0.102041 1.807001 0.195462 2.002463 0.016663 -6.53199
41 0.097124 1.898481 0.186044 2.084524 0.01651 -6.96966
42 0.092554 1.992219 0.17729 2.169508 0.016375 -7.43073
43 0.088299 2.088216 0.16914 2.257355 0.016255 -7.9157
44 0.084331 2.186471 0.161539 2.34801 0.016148 -8.42507
Page
102
The induced drag is minimum at high velocity and very high at low velocity. The parasite drag is
minimum at low velocity and maximum at high velocity. The total drag caused due to these two
components is minimum at the point of intersection of these two drags. The velocity at the minimum
drag is used to get a rough estimation of the cruise velocity of the aircraft.
The velocity at which the sink rate is minimum is the velocity for maximum endurance, from the
graph this is approximately 18.5 m/s.
0
0.5
1
1.5
2
2.5
3
3.5
0 10 20 30 40 50
D
r
a
g
Velocity
Drag vs Velocity
D0
DL
D
Page
103
The point of intersection of the curve and the tangent drawn from the origin to the curve gives the
velocity for maximum range. This is approximately 22 m/s.
Taking the velocity value for maximum range and recalculating the Reynolds Number,
Re =
= 1.225* 22*0.2570 / (2*10
-5) = 291226.6
Also recalculating the Cl value for maximum endurance velocity,
Cl = ( ) = 12.2625 / (0.5*1.225*18.52*0.122625)
= 0.477035
Fig: Clvs Alpha
For the new value of Cl, it can be seen that the initial alpha value shifts to -4 degrees (Show by the
orange line)
New value of Drag = 1.3189 N
Power required for cruising = = 1.3189 * 18.5
= 24.4 W
Page
104
Mission
The aircraft is hand launched from ground level by the operator. The aircraft ascends to four hundred
feet. The aircraft then loiters in the same area for nineteen to twenty minutes taking photographs. It
then descends back to the ground.
Takeoff and climb
The takeoff velocity of the aircraft is approximately 12m/s, 2 cases have been considered for the
climb analysis.
In the first case, the aircraft immediately begins to climb at 12 m/s. In the second case, the aircraft
accelerates to 18.5 m/s(cruise speed) and then begins to climb. The power required to climb to 400
feet is plotted against the time it takes the aircraft to attain this altitude and a suitable time is chosen
such that the power consumption is not very high.
The equation to evaluate power consumed for varying rates of climb is
(
)
W – Weight of the aircraft
v – Velocity
D – Drag
L – Lift
θ - Angle of ascent
Page
105
The graph clearly shows that the power required to climb at 18.5m/s is about 10 to 20 watts lower
than if the aircraft begins to climb immediately at 12m/s. The graph also seems to almost level off at
about 50 seconds. Therefore a time of 60 seconds is taken is taken to complete the ascent phase of the
flight.
Energy requirements for mission
With an engine which consumes fuel such as aviation fuel or kerosene, the range or endurance of the
aircraft can be estimated by applying the Breguet formula. Our aircraft does not use a consumable
fuel, but rather a battery to power the electric motor, which is our primary thrust producing prime
over. Thus, in this case we estimate the amount of energy (joules) required to complete the mission
and then choose a suitable battery which can provide this amount of energy.
Our mission is broken up into 4 phases.
1) Takeoff
2) Loiter
3) Descent Glide
4) Flare
0
20
40
60
80
100
120
140
160
180
200
0 20 40 60 80 100 120 140
PO
WER
(w
atts
)
TIME (s)
Power v/s Time
18.5 m/s
12 m/s
Page
106
The energy required at each stage is estimated theoretically, and then added up to obtain the energy
required for the whole mission.
1) Take-off
The power required to reach four hundred feet has been estimated to be 49 watts. The aircraft
is expected to achieve this in 60 seconds. The product of time and power gives the energy
required. This is calculated to be 2925 J.
2) Loiter The aircraft now levels off and circles the area that has to be scanned. The aircraft remains in
this phase for up to nineteen minutes. The power required for sustained flight at 18.5 m/s has
been estimated at 24 watts.
3) Descent Glide
After the aircraft has scanned a particular area, it begins an unpowered glide to the ground.
The aircraft continues in this state till it reaches an altitude of 20 feet.
4) Flare
The aircraft now slows down and increases its angle of attack to 5 degrees. This is a
controlled stall phase where the aircraft nose points up, but the aircraft descends to the ground
very slowly. It is also called feathering. This phase requires a power of 30 watts.
The energy required for the whole mission is estimated to be 31171.87 joules. The battery selection is
done based on this requirement.
Battery Type Rating
(mah)
Battery
Energy(J)
Battery
Efficiency
90%(J)
Propeller
Efficiency
85%(J)
Motor
Efficiency
85%(J)
No. of
Batteries
GB/T118287 SAMSUNG BATTERY 1500 19980 17982 15284.7 12992 3
Sony Erricson BST 38 970 12920.4 11628.36 9884.106 8401.49 4
Nokia bl 5c 1020 13586.4 12227.76 10393.6 8834.557 4
Rcforall lipobattery 1300 51948 46753.2 39740.22 33779.19 1
Nokia BP 4L 1500 19980 17982 15284.7 12992 3
The efficiency of the battery, propeller and the motor are taken into account and 5 lithium polymer
batteries are considered for our energy requirements. The Rcforall battery turns out to be the lightest
and cheapest option. Therefore it is the battery we have chosen.
Page
107
Stability
The aircraft s designed to be very stable so that the onboard camera does not jerk or shudder, thereby
not compromising on the quality of images taken.
The stability along the lateral axis of the aircraft has been carried out, with a static margin of 10%,
which is ideal for delta wing aircraft. The components have been placed as per space constraints, and
then a dead weight is placed at the aft most position of the aircraft to shift the center of gravity
appropriately.
Component Length
(cm)
Weight
(Grams)
Moment
(gm-cm)
Motor 1.75 145 253.75
Rudder servo+ESC 4.625 20 92.5
Reciever + Camera 9.35 63 589.05
Wing 38.72414 73.575 2849.128
Battery 46.5 93 4324.5
GPS 46.25 75 3468.75
Elevon Servos 23.125 18 416.25
Fuselage 25 72 1800
The above table places the C.G. of the aircraft without the dead weight at 24.65cm from the nose of
the aircraft.
From the position of the wing, the expected center of gravity with a 10% static margin is calculated to
be at 28.15cm from the nose.
Therefore a dead weight of lead is added to the aft most position of the aircraft to pull the C.G. aft so
that the aircraft balances at 28.15cm from the nose. This dead weight has been calculated to be
94gms.
Page
108
Control Surface sizing:
Aileron Sizing:
The aileron span is taken as 85% of the wetted span.
Therefore Aileron span = ba = = 0.85*(50-6) = 37.4 cm
Taking the ratio of Aileron span to Wing span we get 0.748
Reference: Aircraft Design: A conceptual approach by Daniel.P.Raymer
From the graph for a value of 0.748 we get the ratio of Aileron chord to Wing chord as 0.13
Therefore Aileron chord = 0.13* 0.257012 = 3.341155 cm
Page
109
Tail Sizing:
Reference: Aircraft Design: A conceptual approach by Daniel.P.Raymer
From the table above we assume the Tail volume coefficient for a Military cargo/ bomber as 0.08
For delta wings the general practice is to consider the tail area as 25% of the wing area
Therefore, St = 0.25 * 0.122625 = 0.03065625 m2
Calculating Lvt which is the distance between the Aerodynamic centers of the tail and wing.
Reference: Aircraft Design: A conceptual approach by Daniel.P.Raymer
Page
110
Lvt = ( ) = 0.08 * 0.5* .122625 / 0.03065625
= 0.16 m
Assuming a taper ratio for the vertical tail as 0.8 and the span to be 15cm we get;
Cr = 0.227083333m
Ct = 0.181666667m
Also, calculating the value for MAC; MAC = 0.205216049m
Considering AC to be 25% of MAC, AC= 0.051304012m
Leading edge of the root chord of the vertical tail is therefore calculated to be at 39.399cm from the
nose.
Page
111
Glider Fabrication
The main aim of the glider was to ascertain whether the delta wing design was feasible and if the
aircraft showed good gliding characteristics. The glider was a scaled down version of the original
design having a wingspan of 300mm with the other dimensions geometrically scaled down
accordingly.
Material Selection
Since the glider was a scale model, the material that is chosen should be the best trade-off between
weight of the structure of the aircraft and cost required to make the glider.
Based on this selection criterion, three materials were considered for the fabrication of the glider.
They were:
I. Glass Reinforced Plastic (GRP) (Density- 2000 Kg/m3)
II. Balsa Wood (Density – 200 Kg/m3)
III. Corrugated Plastic (CoroPlast) (Density – 1000 Kg/m2)
GRP was the densest and most expensive material, hence was rejected. Balsa Wood, though the least
dense among the three was twice as expensive as a corrugated plastic sheet. Taking these factors into
account, corrugated plastic was the preferred material for the glider.
Wing fabrication
1. The location of the ribs in the wing was taken into account and the chord of each rib was
calculated.
2. A template of each rib was then made using SolidWorks.
3. Using this template, the ribs were laser cut on a 5mm thick sheet of corrugated plastic. The
laser used was a carbon dioxide laser running at 15W.
4. The central spar, leading edge and trailing edge of the wing were made of balsa wood in order
to reduce the structural weight of the wing.
5. To accommodate the central spar, the ribs were arranged up with their trailing edges
positioned along a straight line; the position of the central spar on each rib was marked and a
hole was punched.
6. For the leading edge, a square cross-section balsa rod was taken and sanded into shape. To
accommodate the leading edge, an L shaped cut was made in the front portion of the ribs.
7. The ribs were positioned along the trailing edge and stuck to the balsa using hot glue. The
central spar was then passed through the ribs and glued into place with hot glue. Similarly, the
leading edge was glued onto the ribs, making sure that the leading edge was sitting snugly in
the cuts made in the ribs.
8. Kite paper was used for the outer skin of the wing. Kite paper was used as it is cheap, easily
available and gives a very smooth surface finish.
9. The kite paper was first cut according the size of the wing and stuck onto the ribs using
fevicol. Kite paper once placed over the ribs was completely soaked in water. Kite paper has
the ability to shrink as it dries giving a very smooth and taut outer skin.
10. To facilitate the shrinking, the wing was placed in the sun and left to dry.
Page
112
Fig: Wing with wet kite paper wrap being left to dry in the sun
Page
113
Fuselage Fabrication
1. The four side panels of the fuselage along with front and rear pieces to close the fuselage
were drawn on a sheet of corrugated plastic as a development. Each piece was then cut
out from the sheet.
2. The left side panel of the fuselage and the base piece were then placed at a 90-degree
angle and hot glued in place. Similarly, the right panel of the fuselage was placed and hot
glued.
3. To support the side panels of the fuselage and prevent them from caving in, small right-
angled triangular pieces of balsa were placed at regular intervals along the edge where the
panel was glued onto the base.
4. The top of the fuselage was then hot glued in place. To close the fuselage the front and
the rear pieces were hot glued at the front and the rear.
5. To accommodate the wing, holes were made in the side panels at the locations where the
leading edge, the central spar and the trailing edge met the fuselage.
6. Duct tape was used to close the openings formed because of cutting the corrugated plastic
sheet.
Empennage Fabrication
1. The empennage was fabricated using corrugated plastic. The vertical and horizontal tails
were drawn on a sheet of corrugated plastic as a development. These pieces were then cut
out carefully from the sheet.
2. The midpoint of the horizontal tail was marked and the vertical tail was hot glued in
place.
3. To support the vertical tail and provide a larger area to stick the vertical tail to the
horizontal tail, two rectangular pieces of balsa wood were stuck using hot glue at the
junction where the vertical tail joined with the horizontal tail.
4. This assembly was the placed on the fuselage and using a bead of hot glue was stuck
firmly to the fuselage.
Page
114
Fig: Laser cutting of the ribs
Fig: Kite paper attached to the Rib and spar structure
Page
115
Fig: Fuselage being drawn on the coroplast sheet
Fig: The panels hot glued with wood supports
Page
116
Problems faced during glider fabrication
1. The biggest problem we faced was regarding the laser cutting of the ribs from corrugated
plastic. Very few places in Bangalore have machines that are capable of laser cutting
corrugated plastic. After a weeklong search, we were able to locate a company in Whitefield
by the name of ViableAsia, which could help us out.
2. During the initial fabrication phase of the fuselage, the fuselage was cut such that the ridges
were in a direction perpendicular to the ground. With such an arrangement, the ability of the
corrugated plastic to absorb heavy impact was reduced considerably. To overcome this, the
fuselage was cut keeping the ridges parallel to the ground.
3. When the wings were attached to the fuselage the trailing edge of the wing was not snug fit
and had a tendency to slip out even after a bead of hot glue was applied. To prevent this, a
rectangular piece of balsa was inserted in the hole creating a snug fit for the wing.
4. In order to get a smooth surface after shrinking, the kite paper must be stuck very carefully
over the ribs to ensure that it is smooth and there are no ridges or contusions.
Page
117
Glider Tests
Glider tests were carried out to evaluate the following parameters:
To evaluate the aircraft’s roll and lateral stability.
To evaluate the aircraft glide performance.
To evaluate the ability of the material to absorb the impact of a belly landing.
The glider tests were carried out on a 1:0.6 scale model of the aircraft. The glider tests were carried
out both indoors and outdoors.
Glider Test – I
This test was carried out outdoors. The aircraft’s centre of gravity was found to be lying closer to the
aft of the aircraft making the aircraft tail heavy. To pull the centre of gravity forward, ballast in the
form of coins were added to the nose of the aircraft.
The glider was hand launched from a height of 6 feet.
Evaluation of glider performance
During the initial flight, the glider had a propensity to turn left soon after launch. This was overcome
by trimming the ailerons and by altering the throwing action. After trimming, the glider was launched
again and the glider displayed good gliding performance as well as good roll and lateral stability and
glided a distance of over 12 feet. The glider belly landed on gravel and showed no signs of damage.
Fig 1: The Correct throwing action
Page
118
Fig 2: Glider after launch
Fig 3: Glider landing in gravel
Page
119
Glider Test – II
This test was carried out indoors. The aircraft’s centre of gravity was found to be lying closer to the
aft of the aircraft making the aircraft tail heavy. To pull the centre of gravity forward, ballast in the
form of coins were added to the nose of the aircraft.
The glider was hand launched from a height of 10 feet.
Evaluation of glider performance
The glider initially showed good gliding performance but a few seconds into flight, the aircraft stalled
resulting in a spin and a nosedive. The nosedive resulted in a nose first crash into the ground. The stall
was caused because the angle at which the glider was launched was incorrect. No signs of damage
were observed on the glider.
Fig 1: Incorrect angle of launch
Page
120
Fig 2: Glider stalls in mid flight
Fig 3: Nosedive because of stall
Page
121
Fig 4: Resulting Crash
The angle at which the glider was launched was corrected and the glider was launched again. This
time the glider showed good gliding performance and glided a distance of 10 feet. The glider landed
smoothly and no signs of damage were observed.
Fig 1: Corrected angle of launch
Page
122
Fig 2: Glider after launch
Fig 3: Smooth landing
The glider tests conclusively proved that the aircraft exhibits good gliding performance and lateral
and roll stability. The tests also proved that corrugated plastic was capable of withstanding a belly
landing under different ground conditions.
Page
123
Problems with the Delta Wing configuration:
1. Sweep
There were 2 basic problems with the swept planform
Construction of the internal frame of the swept wing was difficult and time
consuming because if there was any inaccuracy, the pieces would not fit together.
Stall characteristics – Though the swept wing can go to higher angles of attack
without stalling than a conventional planform, the aircraft finds it very difficult to
recover once it has stalled and begins to spin.
Fig :Dh 108 Swallow – Delta Wing Notorious For Spin Instability
2. No weight tolerance
There was no tolerance added for any kind of extra weight in the form of glue, wires,
packaging. Cfd runs on Solidworks showed us that we could expect a lift of 500gms at cruise
condition, whereas our all up weight was 503gms.
3. No Construction tolerance
A small warp or structural defect causes instability in flight. The model does not have
forgiving flight characteristics, in that a small mistake from the pilot puts the aircraft in an
unrecoverable state.
4. Difficulty faced during hand launch:
The high wing loading causes the aircraft to have a very high stall speed of 9 m/s (32.4
kmph), which in turn means that the take-off velocity of the aircraft is about 12 m/s (43
kmph). Since our aircraft is a hand launched aircraft, this take off velocity becomes
impractical.
Page
124
In order to overcome the above mentioned difficulties:
1) We removed the 500 mm constraint so that the wing loading remains low enough.
2) We changed the planform from a delta to a conventional planform. The conventional
planform includes a wing +horizontal stabilizer + vertical stabilizer. Also the wing would be a
rectangular wing.
3) We started with a 1m wing span, and then practically shortened the span while increasing the
chord length, keeping the wing loading a constant and seeing how short a wingspan we could
achieve so that the aircraft’s flight characteristics suit our requirements.
Page
125
References
1. Aircraft Design: A Conceptual Approach; Daniel P. Raymer
American Institute of Aeronautics and Astronautics Inc Publication
2. Model Aircraft Aerodynamics; Martin Simons
A Special Interest Model Books Publications
3. Basics Of R/C Model Aircraft Design; Andy Lennon
AirAge Media Publications
4. Aircraft Performance and Design: Dr J.D.Anderson Jr
A WCB/McGraw-Hill Publication
5. Beginners Guide To Radio Control Airplanes, Nickademuss
www.instructables.com
Bibliography
Apart from the above sources, these websites were helpful in understanding the practicalities of
flying and fabricating remote controlled aircraft.
1. www.rcgroups.com
2. www.ebay.in
3. www.rcindia.com
4. www.rcthrustcalc.com
5. www.rcdhamaka.com
6. www.rcforall.com
7. www.bananahobby.com
8. www.instructables.com
Recommended