INDIAN INSTITUTE OF TECHNOLOGY

KANPUR

Composite Hub

Advanced Airfoils

Tip Shape

Vibration Isolation System

Self Sealing Fuel Tanks

Extensive use of

CompositesCabin Door

Hingelesss, Good Manoeuverability, Maintainence Free, Foldable

Efficient Lift

Removable, Low Noise, High Speed

Low Vibratoin, Smooth Ride

Multifunction Displays, AFCS, Less pilot work load

Long Life, Corrosion Resistance

Twin Engines with Full Authority Digital Electronic Control

Easy Access, Sliding Cargo Tracks

Tapered, Swept Back, 25% chord Flaps, Reduced Hover Download Optimised Lift in Forward Flight, Removable

Efficient at forward speeds, Reduced Rotor Wake Interaction, Removable

Tractor Configuration, Cant angle, Low Maintainence

Easily configurable interiors

Variable Incidence Stabilator, Improved longitudanal stability, Easy to trim

Safety, Modular

INDIAN INSTITUTE OF TECHNOLOGY KANPUR

BASELINE HELICOPTERS

Kaman UH-2A

•Turbojet-single 2,500 lb static thrust General Electric YJ85

•Trials carried out using a modified UH-2A Seasprite.

•Modifications were made to graft a pair of wings from a Beech Queen Air light executive transport aircraft onto the sides of the lower fuselage, giving the aircraft a wingspan of 35.25 ft

•Reached speeds up to 225 mph.

•Pilots reported that the wings did not hinder autorotation

Lockheed XH-51 A

•Turbojet-2,500 lb static thrust Pratt & Whitney J60-P-2

•A set of wings spanning 16.9 ft in was fitted to the aircraft

•The auxiliary turbojet and stub wings partially unloaded the main rotor in forward flight, reducing the critical blade tip speedand blade angle

•The wings were each equipped with spoilers to assist entry into autorotation at high speed in an emergency. In addition, the horizontal and vertical tail surfaces were enlarged

•On June,1967, the XH-51A Compound set an record for rotorcraft by attaining a speed of 302.6 mph.

Sikorsky X-2

•Propeller-LHTEC T800 Turbo shaft Engine.

•Incorporated the research findings from Sikorsky S-69 coaxial helicopter developed as a part of the Advancing Blade Concept (ABC) program.

•Maximum Speed 250knots.

•The demonstrator also reached a speed of 260 knots in a shallow 2’’ to 3’’ dive.

•Poor Payload / Gross Weight ratio

MISSIONS

Main Rotor

Auxiliary Thrust

Wing

Main Rotor

Main Rotor

Rescue Mission :i) Speed of 192 knots achievable

ii) Reaches destination within the

golden hour.

iii) Both thrust and lift compounded.

iv) TOGW: 12484 lbs

Return Flight : 11284 lbs

Insertion :i) Best range speed of 120 knots.

ii) Carries a heavy payload of 4000 lbs.

iii) Does not require thrust and lift

compounding and hence wings and

propeller are removed.

iv) TOGW: 13600 lbs

Return Flight : 12267 lbs

Resupply :i) Best Range speed of 120 knots.

ii) Lower payload and hence has

lowest gross weight among the

three missions.

iii) This mission also doesn’t require

thrust and lift compounding.

iv) TOGW :12900 lbs

Return Flight : 11750 lbs

MAIN ROTORITEM DETAIL

Radius 21.325 ft

Chord 1.97 ft

Tip Speed 644 ft/s

Solidity 0.147

Twist -2o

Lock Number 12

Mass 920lbs

Hinge Offset 15%R

BERP Tip

This blade tip

shape

reduces

compressibility

and has high

stall angle.

Tip Speed

•The tip speed is limited to 644 ft/s because of compressibility, noise and retreating blade stall effects

Solidity

•The solidity is high because it has lower vibration, noise, and delayed retreating blade stall

Twist

•It has low twist to prevent blade stress during fast forward flight

Aspect Ratio

•Small aspect ratio to ensure natural frequency of 2nd flapping mode is below 3/rev

WING DESIGN

Variable incidence wing

Flaps

Spoilers and

Brakes

Wing Plan form

and Geometry

Aerofoil

•A majority of past compound helicopter

designs have utilized a compromise wing

aspect ratio of around 6 to create a balance

between low induced drag in cruising flight

and hover download minimization.

•Sweep has been used to a moderate degree

on a majority of the past compound aircraft,

mainly as a means of correctly positioning

the wing aerodynamic centre.

•The general thought on the choice of aerofoil section for

compound helicopters has been to use a section of fairly large

thickness, with low drag in cruising flight, a high maximum

lift coefficient and gentle stall.

•It provides the ability to optimize the wing lift ratio.

•It adds to structural complexity of the design, adding to the weight

of the aircraft and the inability to build in components such as

undercarriage and fuel storage into the wing.

•Since wings are used only in search and rescue mission requiring a

large volume of fuel, this concept was not incorporated.

•A trade off which allows the wing lift to be

controlled to a greater degree is the use of

flaps which allows controlled the wing lift

to a greater degree while not impairing the

structural simplicity.

•A plain flap of 25 per cent of the wing

chord length and with a deflection less than

90o, to a void flow separation, could reduce

the download of a wing by the order of 30

per cent.

•Previous experiences with compound

helicopters have indicated that the auto

rotative capabilities are not enhanced

substantially with spoilers hence they

have not been incorporated into our

design.

AUXILIARY THRUST•Mainly used for improvements in the fuel consumption over the turbojet and the resultant gross weight reductions enabling it to be used for long high-speed missions .

•Used in Bell-533 compound Helicopter.

Turbofan

•The efficiency of the propeller offers improved acceleration and extended range for a set fuel load, particularly if a majority of the flight time is to be spent in cruising flight.

•The first is that by using reverse pitch it acts as an extremely effective braking device to slow the aircraft .

Propeller

•The ducted fan is in a way a compromise between the propeller and the turbofan, attempting to maintain the efficiency of a propeller while using less disc area.

•The shroud incurs a weight penalty for the aircraft and, particularly if wing mounted, may induce significant blockage effects in hovering flight .

Ducted fan

•Has the benefit of being a proven and mature technology.

•Its drawback is that to ensure an adequate fatigue life it generally results in a system of significant weight.

Mechanical

•Single powershaft connectedto a variable pitchfan, the fan pitchdetermining howmuch shaft poweris available forthe rotor shaft.

•Benefit of leavingthe engine coreessentiallyunchanged, apartfrom optimizingthe geometry.

Variable cycle –Single Power Shaft

•Separate turbinefor driving therotor and thepropeller,allowing theirspeeds to beindependentlycontrolled.

•Efficiency willdepend on that offixed geometrysystem at itsdesign point.

Variable Cycle-Separate free Turbines

•By reducing the nozzle area a backpressure is formed, which transfers energy from the shaft to the jet thrust.

•A fixed nozzle was used on the world speed record Lynx aircraft to produce this effect.

Variable Cycle-Variable Nozzle Area

For the given mission profile, and taking into account the

nature of various missions and reconfigurations, propeller

complied with most of the mission requirements and

provided a lighter, less noisy and a reliable source of

auxiliary thrust.

• Ease of Installation and removal during

reconfiguration.

• It has greater fuel efficiency as compared to turbofan

and turbojet engines.

• It reduces mechanical complexity and separation losses

as compared to the fan-in-fin ducted fan concept.

• When auxiliary thrust is not required in Insertion and

Resupply missions, ducted fan concept poses

problems in reconfiguring the helicopter.

• The transmission system

selected is the simple

mechanical transmission as 2

engines were installed.

•According to Trade studies,

Variable Cycle- Single Powered

Shaft gives the best efficiency

for a single engine compound

helicopter with propeller.

WEIGHTS

Mission Location (ft)

Search and

Rescue19.69

Resupply 20.42

Insertion

(outboard)20.68

Insertion

(inboard)19.35

GROUP WEIGHT(lbs)

Main Rotor and Hub 920

Tail Rotor and Hub 127

Body 2445

Engine 1226

Horizontal Stabilizer 60

Vertical Fin 88

Wing 484

Propeller Unit 100

Transmission 1280

Fuel Tanks 3000

Nacelles 296

Crew 730

Cockpit Controls 30

Landing Gear 398

TRIM

Pitch Moment Equation (gives an estimate of Β1c )

Roll Moment Equation (gives

Β1s )

Calculation of Tail Rotor Thrust

coefficient Cat

Calculation of Roll Angle φ

Horizontal Force Equation

(calculation of α,Cat)

Vertical Force Equation (calculation

of Ct)

Calculation of inflow ratio λ

Estimation of θ0,θ1c,θ1s

TRIM CURVES

Inflow Curve Control Input (θ)

Flap Angle (β) Roll Angle(φ)

Search &

Rescue

Insertion

Resupply

PERFORMANCE

REVERSE FLOW AND RETREATING STALL

Reverse Flow

Region

Advancing

Side

Advancing

Side

Retreating

SideRetreating

Side

Stalled Region

Stalled Region

To prevent retreating blade

stall, the airfoil is designed in

such a way that it has a high

stall angle limit. The airfoil als

has a high Mach drag

divergence number.

RECONFIGURATION

•Addition of wings and propeller for compounding lift and thrust

•Cant angle is zero.

•Horizontal stabilizer incidence angle is varied for outbound leg and inbound leg since both are at different speeds and wing setting angle is fixed.

•BERP airfoil is used for the tips.

Rescue

•Wings and Propeller are removed.

•Cant angle and horizontal stabilizer angle is given to adjust for the change in C.G and is the highest for all missions during the inbound leg.

•Swept tips are incorporated in the rotor.

Insertion

•Wings and propeller are removed.

•Cant angle and horizontal stabilizer angle is given to adjust for the change in C.G.

•Swept tips are incorporated in the rotor.

Resupply

SEARCH AND RESCUE CONFIGURATION

POSSIBLE INTERIOR ARRANGEMENTS

IATA

Container

Type 8

IATA

Container

Type 8D

6

Passengers

Cargo

Container

Transport

IMPORTANT COMPONENTS

Wing Flaps

EngineAuxiliary

Propulsion

Tail

Hub

COST

ANALYSIS

•Depreciation Charges

•Dpr= Pr/10000

•Direct Operating Cost

•DOCh=2.25*Dpr/10000 +0.7*Q

where Q is the fuel consumption

in kg/hr.

Direct Operating Cost

•Time of Mission ~ 3 hrs

•Fuel Consumed ~ 1360 kg

•Q=453.33 kg/hr

•Dpr=600

•DOCh=$317.468 /hr

Search & Rescue

•Time of Mission ~4 hrs

•Fuel Consumed~1040 kg

•Q=260 kg/hr

•Dpr=600

•DOCh=$182.135 /hr

Insertion

•Time of Mission ~4 hrs

•Fuel consumed ~900 kg

•Q=225 kg/hr

•Dpr=600

•DOCh=$157.635 /hr

Resupply

•Calculated using Harris and Scully relation.

•It is found that price increases with disk loading.

•Engine power is also a key factor influencing the price

•Pr=$5.1 million

•By factoring in advanced research and development technologies Pr=$ 6 million.

Relative Price of Unit