Configuration design and optimisation study of a compound gyroplane

5/24/2018 Configuration design and optimisation study of a compound gyroplane - sli...

http:///reader/full/configuration-design-and-optimisation-study-of-a-compou

Configuration design and optimisation studyof a compound gyroplane

Ngoc Anh Vu, Young-Jae Lee, Jae-Woo Lee and Sangho Kim

Aerospace Information Engineering Department, Konkuk University, Seoul, South Korea, and

In Jae Chung

Agency for Defense Development, Dae Jeon, South Korea

AbstractPurpose The purpose of this paper is to study the conceptual design and optimisation of a compound gyroplane. A study of a compound gyroplaneconfiguration and its characteristics was performed to develop a sizing program.Design/methodology/approach The vertical takeoff and landing capabilities of a helicopter are particularly important. The need for efficient hoveand the effectiveness of forward flight in the helicopter can cause conflicts within the design process. The designers usually wish to increase thehelicopters maximum forward speed. Recently, the compound aircraft is one of the concepts considered for the purpose of expanding the flightenvelope of rotorcraft. The study of the compound gyroplane showed its advance capabilities for this purpose. Understanding its characteristics,a number of calculations are conducted to implement a sizing program for compound gyroplanes based on the conventional helicopter sizing process.Findings The results of the sizing program were validated using existing aircraft data such as the Challis Heliplane, Carter Copter, FB-1 Gyrodyne,and Jet Gyrodyne. The program is appropriate to size a compound gyroplane at the conceptual design phase. An optimisation study was also performed

to enhance sizing results. The compromise between the rotor lift sharing factor and the ratio of the wing span (Bw) to rotor diameter (D) was solved bychoosing the total gross weight (TOGW) as the objective function, while the design variables are compromising factors. The optimum results showedthat the TOGW of all four kinds of compound gyroplanes was considerably reduced.Originality/value A conceptual sizing program for unconventional compound aircraft was developed. The study showed that an optimum designprocess is necessary to enhance the sizing results.

Keywords Compound gyroplane, Design optimisation, Aircraft sizing, Aircraft, Helicopters

Paper type Research paper

Nomenclature

SymbolBw wing span (m)

D rotor diameter (m)

N rotor lift sharing factor

A rotor disc area (m2

)

V rotor rotational speed (rad/s)

R rotor radius (m)

CP0 rotor profile power coefficient

Cd0 rotor average profile drag coefficient

s rotor solidity

m advance ratiok rotor induced power correction factor

CQ rotor profile torque

CQi rotor induced torque

l inflow ratio

CT rotor thrust coefficienta rotor disc tilting angle

r air density (slugs/ft3)

Trotor rotor thrust (N)

Hrotor rotor drag force (N)

Dwing wing drag (N)

Dfuselage fuselage drag (N)Tprop thrust required for the propeller (N)

CH rotor drag force coefficients

P required power for compound gyroplane (kW)

V forward speed (m/s)

hprop propeller efficiency

Q available torque from tip-jet system (N.m)

Fj tip drive force of tip-jet system (N)

mj tip-jet mass flow rate (kg/s)

VT rotor tip speed (m/s)

Vj tip-jet nozzle exit velocity (m/s)

T0d total temperature in the rotor duct (K)

P0d total pressure in the rotor duct (N/m2

)

Lwing wing lift (N)

CW

wing lift coefficientW/S wing loading (N/m2

)

AbbreviationsTOGW total gross weight

CRW canard rotor/wing

VTOL vertical takeoff/landingThe current issue and full text archive of this journal is available atwww.emeraldinsight.com/1748-8842.htm

Aircraft Engineering and Aerospace Technology: An International Journal

83/6 (2011) 420428

q Emerald Group Publishing Limited [ISSN 1748-8842]

[DOI 10.1108/00022661111173298]

This work was supported by a National Research Foundation Granfunded by the Korean Government with project reference K2060100001,and also the Defence Acquisition Program Administration and Agency forDefen ce Dev elopment in Republic of K or ea u nd er con tr acUD070041AD.

420



STOL short takeoff/landing

SQP sequential quadratic programming

GA genetic algorithm

MDO multidisciplinary design optimization

UAV unmanned air vehicle

CFD computational fluid dynamics

FEM finite element method

SLP sequential linear programWE empty weight

PL payload

HT horizontal tail

VT vertical tail

Introduction

The helicopter is a complex system. The main complexity

comes from the rotor aerodynamics. A helicopter design is

usually evaluated by its hover and forward flight performance.

These demands are conflicting. The helicopter must achieve a

steady hovering flight condition with efficient performance.

This is achieved with a large main rotor size where the bladesrotate in the horizontal plane (Newman, 2006). The blade tip

Mach number is usually 0.5-0.7. After achieving an efficient

hover, the helicopter is required to move into forward flight.

Therefore, the rotor of a helicopter is responsible for providing

lift in opposition to the helicopters weight, propulsion

(horizontal thrust) to overcome the drag of the aircraft, and

force and moment to control the altitude and position of the

helicopter. In forward flight, a component of the free stream

adds to or subtracts from the rotational velocity at each part of

the blade (Leishman, 2006). This produces a dissymmetry of

the aerodynamic condition on the retreating side to the

advancing side of the rotor. In order to overcome this particular

problem, Juan de la Cierva came up with the solution of using

flapping hinges which enable the rotor blades to move, in a

vertical sense, out of the plane of rotation (Newman, 2006).However, the forward speed of the helicopter is limited due to

the problem of compressibility of the advancing blade tip, and

stall condition of the retreating blade tip. One method of

overcoming the limitations of the rotor is to provide it with a lift

and propulsion source by using an additional wing and/or

propeller, commonly known as the compound helicopter.

One of the advanced concepts studied by Carter Aviation

Technologies is the slowed rotor/compound aircraft.

The aircraft technology is so named because it involves

dramatically slowing the rotor of a hybrid rotorcraft and

transferring lift to wings that are optimised for high-speed

flight (Carter, 2010). In forward flight, the rotating speed of

the rotor is reduced in comparison with hover performance.

In some concepts, the rotor is still powered by the engine. Theconcept of the rotor not being powered by the engine but by

an autorotation phenomenon is called the gyroplane. In this

study, a compound gyroplane with an additional wing and

with the rotor on an autogiro is considered. An autogiro has a

rotor that can turn freely on a rotor shaft. The rotor tilts

backward at an angle of attack. The aircraft moves forward in

level flight powered by a propeller. The resultant aerodynamic

forces on the blades cause the necessary torque to spin the

rotor and create lift (Leishman, 2004). Both wing and rotor

generate lift, however the division of lift on the rotor and the

wing are different in each flight condition (low speed, high

speed, etc.). The thrust is usually generated by turbofan

or turboprop engines via propellers. The autogiro was

developed by Juan de la Cierva and it was the first type of

rotating-wing aircraft to fly successfully (de la Cierva and

Rose, 1931). The aerodynamic phenomenon of autorotating

bodies had been observed in variety of experiments by the

beginning of the twentieth century, which date to earlier

theoretical work by the Scottish Physicist James Maxwell

Wheatley (1933) studied the load sharing between the rotorand the wing and also examined the manoeuvrability

characteristics of the autogiro.

Gustafson (1971) gave a first-hand summary of the early

NACA technical work on both autogiros and helicopters

In the 1950s, there was a series of prototypes designed by the

Fairey Company in Britain and Lockheed in the USA. These

were designed to overcome the inherent forward flight speed

limitations of a conventional helicopter. During the late 1950s

and early 1960s, single and two seat commercial autogiros

were developed in North America for the private aviation

market by three companies: Umbaugh (later air and space),

Avian, and McCulloch.

Recently, there are two companies in the USA that

have developed the idea of the autogiro or gyroplane. Using

modern technologies they have exploited its capabilities. These

companies are Carter Aviation Technologies and Groen

Brothers Aviation. The Carter concept incorporates a rotor

and fixed wing. The rotor provides nearly all of the lift during

takeoff and landing, the wing provides most of the lift in high

forward speed, the rotor completely offloaded and operating in

its autorotation.

Groen Brothers Aviation Company and the GeorgiaInstitute

of Technology have been developing the Heliplane for

the DARPA project. A reaction driven system is applied in the

Heliplane for vertical flight. When the Heliplane takes off, the

engine nozzleclosesand gasflow goesto the rotor tip-jetnozzles

through duct pipes. When it cruises, the duct pipes are closed

and the engine nozzle is opened, and then the gas flow is blown

out through the nozzle.From a scientific perspective, there are very few studies

regarding autogiros. At Glasgow University, the stability

control, and handling qualities of autogiros have been

examined (Houston, 1998).

This paper describes the characteristics of the compound

gyroplane and its advantages, thereby developing a sizing

program for this kind of configuration. An optimisation study

was also performed in order to enhance the sizing results

This is a valuable accomplishment for the conceptual design

study of unconventional rotorcraft.

Aircraft configuration design and optimisationstudy

This section will discuss about configuration design

and optimisation study of fixed-wing aircraft, helicopter, and

compound aircraft. The characteristics of compound

gyroplane will be discussed.

Compound gyroplane characteristics

As the helicopter moves forward, theadvance ratio andblade tip

Mach number also increases in response to the speed of the

helicopter. The rotor of a conventional helicopter has a fixed

rotating speed. The advance ratio is defined by a ratio of the

forward speedof themachineto therotorblade tip speed. Asthe

advance ratio increases, the advancing rotor tip speed could

Configuration design and optimisation study of a compound gyroplane

Ngoc Anh Vu, Young-Jae Lee, Jae-Woo Lee, Sangho Kim and In Jae Chung

Aircraft Engineering and Aerospace Technology: An International Journa

Volume 83 Number 6 2011 420 428

421



reach the supersonic condition where the drag increases

significantly, known as drag divergence; in addition the

retreating rotor tip speed could enter the stall condition due

to the high angle of attack of the blade. The compressibility at

the advancing blade tip and the stall at the retreating side limit

theforward speed. A solution to theproblem is to supply thelift

and propulsion by providing the fuselage with a wing to offload

the rotor, together with an auxiliary propulsion device. Theidealeads to the launch of a new hybrid aircraft concept. An aircraft

with wings,propellers, androtorspoweredby an engine is called

a compound helicopter. As the rotor freely rotates in forward

flight, the hybrid aircraft as mentioned is called a compound

gyroplane. According to those discussions, the lift from the

rotor of a compound gyroplane is the major component when

it flies at takeoff, landing, or low speed. On the other hand, the

wings are the main surface that generates lift at high speed.

When compared to a fixed-wing aircraft, the compound

gyroplane needs a very short runway for takeoff and landing.

The rotor of a gyroplane always operates in an autorotative

condition, where the power to turn the rotor comes from a

relative flowdirectedupward. As theaircraft moves forward, the

rotor continues to turn and produce lift. Because the rotor is

always in the autorotative state, the gyroplane always descends

and lands safely when engine power is lost. The gyroplane

system is simpler than a shaft-driven helicopter because it does

not need an engine gearbox and rotor transmission. The

separate countering torque reaction, such as the tail rotor on the

helicopter, is also not necessary. These all significantly reduced

the weight, design, production and capital cost. The five-seater

aircraft, the slow rotor/compound prototype of Carter, has

achieved an advance ratio of 0.87. It demonstratesthe validity of

the technology and feasibility of constructing rotorcraft capable

of high-speed and high-altitude flight with a fuel efficiency

approaching that of fixed-wing aircraft (Carter, 2010). The

lightweight sports gyroplane can fly at a cruising condition of

about 18 knots (33 km/h).

One disadvantage of the gyroplane is that it cannot hover.In 1933, de la Cierva and James Bennettbuilt a system in which

the rotor could be clutched to theengine through a transmission

when the gyroplane was on the ground. The friction from its

wheels prevents it from turning and responding to the rotor

torque reaction. In this condition, the blades could be set to a

flat pitch. When the speed of the rotor reaches the necessary

speed to lift the aircraft, the rotor would be declutched from the

engine transmission and the collective pitch increased. This

technique is termed jump takeoff (Prewitt, 1938). This system

could also support the hover take offand landing of a gyroplane.

However, the machine needs a device to react to the rotor

torque. For that purpose two propellers on either side (left and

right) of the machine are preferred, as in the Carter Heliplane.

Some other technologies known as the pressure jet propulsionsystem are applied to eliminate rotor torque. According to this

concept, the rotor is turned by the engine exhaust air ejected

through the rotor-tip nozzles. It should be noted that the

installation of any system such as clutch-declutch system,

or tip-jet system, could increase the complexity of the machine

system and consequently increase the maintenance, operation

cost, and the overall weight of the vehicle.

Classification of aircraft

Figure 1 shows compound aircraft classifications proposed

by the author. The compound gyroplane belongs to the

compound aircraft category. There are three different kinds

of aircraft in this category. The first is the multimode aircraft

including the tilt-rotor aircraft, tilt-wing aircraft, and canard

rotor/wing (CRW). The second is the compound helicopter

this is a winged helicopter which has an auxiliary engine

the AH-56 Cheyenne belongs to this category. The last

classification is the compound gyroplane, which is divided into

two subcategories: short takeoff and landing (STOL) and

vertical takeoff and landing (VTOL) compound gyroplanesThe Carter Copter is a STOL, while the Heliplane is a VTOL.

Optimisation design studies

Design is a process of finding a set of design variables which

satisfy the predefined design requirements and the system

performance. To find the set of design variables a designer

carries out a sensitivity study, a study of the effects on a design

objective with respect to changes in each of the design variables

Based on the sensitivity study, the design variables are then

properly bounded; that is their maximum and minimum values

are determined. Finally, a number of diverse optimisation

algorithms such as gradient based, sequential quadratic

programming, genetic algorithm, etc. are applied to seek the

optimum solution.Since each system in an engineering design consists o

multiple disciplines that are linked together, a design

process should consider all of these systems concurrently

Multidisciplinary design optimisation (MDO), which

allows designers to incorporate all the relevant disciplines

simultaneously, takes into account mutually dependent design

elements from various fields, and has the advantage of reduced

time and cost compared to serial design approaches. Since

MDOwas originallydevised in the 1990s, it has beendeveloped

for the design of aircrafts, although it has also recently been

applied to diverse design applications including shipbuilding

and automobile engineering. Applying MDO methodologies to

actual design problems requires several techniques such as

system modelling, analysis of each discipline, approximation

system decomposition, sensitivity analysis, and optimisation.

Design optimisation of aircraft

The state of the art of aircraft design optimisation is discussed

in this section.

Fixed-wing aircraft

Generally, fixed-wing aircraft design optimisation based on

semi-empirical equations has been well established since the

beginning of aircraft design. These methods, based on

Jan Roskam, Raymer methods, GASP, and ACSYNT, have

been used extensively and efficiently to acquire rapid analysis

results in MDO frameworks.

These low-fidelity methods consist of aerodynamics

propulsion, mission, weight, stability and control (S & C)and performance modules. For design optimisation of a

conventional fixed-wing aircraft, sizing is first carried ou

using the aerodynamics, propulsion, mission, and weigh

modules. Then, a performance measure of the aircraft o

interest is taken using the S & C and performance module

Finally,designoptimisation is carriedout based on the results o

the analysis to find the best aircraft configuration by setting the

design objectives, typically taken as the takeoff gross weight

or endurance of the aircraft. This low-fidelity model has been

successfully used for the design of various conventiona

aircraft including an advanced fighter and an unmanned air

vehicle (UAV).




Volume 83 Number 6 2011 420 428

422



However, this low-fidelity model is basically built on

conventional fixed-wing aircraft regression data. Hence, the

design of unconventional aircraft, such as UAV and unmanned

combat air vehicles, may possibly encounter problems when

low-fidelity analysis is used.

More recently, to obtain more reliable aircraft design

results, high-fidelity methods such as computational fluid

dynamics (CFD) and the finite element method (FEM) have

been used in MDO frameworks. For example, an MDO of themain wing for an unconventional aircraft has been performed

using CFD and FEM (Choi, 2010). In addition, much

research into MDO framework development has been carried

out in order to provide more convenient MDO environments

for the designer. Although the computational cost of solving

the high-fidelity codes has decreased rapidly due to the

development of computer resources over recent years,

obstacles are still encountered when applying them to large

MDO problems based on high-fidelity codes.

Helicopter

State of the art of conceptual helicopter design still relies on a

few well-known codes such as HESCOMP, VASCOMP, and

GTPDP, which employ empirical equations. In contrast to

fixed-wing design, most of the research focuses on the designof the rotor blade to optimise performance, vibration, noise,

and so on because the performance of the rotor blade plays an

essential role in most of the disciplines regarding helicopter

design.

Recently, several efforts to simulate the aerodynamics of the

helicopter rotor blade have been in progress. However,

achieving results remains difficult and expensive.

Compound aircraft

Only a few design optimisations of compound aircraft have

been made by some technologically advanced countries. For

example, MDO has been carried out for sizing stopped rotor

configurations which utilise reaction drive and circulation

control (Dimitriet al., 1994). Recently, the NASA Heavy Lift

Rotorcraft Systems Investigation was conducted to identify

candidate configurations for large civil VTOL transport

that is technically promising and economically competitive

(Johnson et al., 2006). Yeo and Johnson (2008) carried out

the optimum design of a compound helicopter and conducted

performance, S & C analyses using comprehensive rotorcraft

analysis, CAMRAD II. In Korea, there has also been someresearch into the design optimisation of a tilt-rotor

configuration and CRW configuration as part of the Korean

Smart UAV development project.

Meanwhile, little research on the design optimisation o

compound gyroplanes has been reported, since compound

aircraft are rarely developed. Currently, in the development of

the Heliplane, the design method for the CRW configuration is

used since the reaction drive for CRW is also applicable to the

Heliplane. However, it would seem that no proper design tools

for the Carter Copter design have existed until recently. Based

on the characteristics of the compound gyroplane, the design

features of fixed-wing aircraft and rotorcraft should be taken

into account simultaneously. Otherwise emerging aerodynamic

characteristics due to the unconventional configuration, such as

interference drag between the rotor and wing of the compound

gyroplane, cannot be properly analysed. In particular, since the

balance of lift on the wing and the rotor for each flight mode

should be carefully handled, establishing a design process using

an optimisation method is essential for compound gyroplane

design. In addition, considering the complexity and the

unfamiliarity of the compound gyroplane and the expected

rise in demand for this unconventional aircraft concept

MDO studies should be actively continued. For this purpose,

a compound gyroplane sizing program has been developed and

its suitability has been validated using existing aircraft data

Using the sizing program developed, a conceptual design

Figure 1Classification of aircraft

Aircraft

Compound

Aircraft

Rotary Wing

Aircraft

Fixed Wing

Aircraft

Compound

Helicopter

Transition Aircraft

(Multimode)

Tilt Rotor Tilt WingCanard Rotor /

Wing (CRW)

STOL Gyroplane

(Carter Copter)

VTOL Gyroplane

(Heliplane)

Compound

Gyroplane

Gyroplane

(No Wing)Helicopter




Volume 83 Number 6 2011 420 428

423



and optimisation study has been performed to obtain the

configuration and weight of a compound gyroplane in the

present work.

Compound gyroplane sizing programdevelopment

In the sizing program developed, HESCOMP, the rotarywing sizing program and the CRW sizing program which was

developed by Konkuk University, were based on (Jeon et al.,

2008). The winged helicopter was chosen for the

compound gyroplane concept from among the rotary-wing

aircraft concepts that can be analysed in HESCOMP (Davis

and Wisniewski, 1973). In general, all data trends of the

compound gyroplane come from conventional helicopter

statistical data. Some modules are added to and eliminated

from the conventional helicopter sizing process. In this study,

the compound gyroplane is considered for the sizing process.

The VTOL performance are conducted by the tip-jet system.

Development considerations

Inherently, the conventional helicopter employs a turbo-shaft

engine to drive the main rotor and tail rotor. In contrast witha conventional helicopter, the compound gyroplane uses

turboprop or turbofan engines to drive the propeller and to

directly provide thrust. Therefore, an engine cycle analysis

module was developed in order to analyse turbofan and

turboprop engines. In the configuration and weight analysis

modules, the additional fixed main wing is sized according to a

lift sharing factor between the wing and rotor. Horizontal

tail (HT) and vertical tail sizing are based on size trends of

helicopter data. In comparison to the helicopter, the compound

gyroplane has no tail rotor or rotor transmission system, so that

the weight of these components should be eliminated from the

sizing process.

At low speed most of the lift was obtained from the rotor,

while at high speed most of the lift was obtained from themain wing. Therefore, the lift sharing factor (N) between the

rotor and the wing is considered in this program.

The energy to drive the rotor in forward flight comes from

the relative airstream directed upward through the rotor

(Leishman, 2006). For this reason, the interference between

the rotor and the wing is eliminated.

Program development

The compound gyroplane sizing program consists of eight

modules as shown in Figure 2. A rotor performance analysis

module for calculating the rotor performance, a mission

analysis module for calculating fuel weight, an aerodynamic

analysis module for calculating drag and lift, an engine

cycle analysis module for calculating the available power and

selecting the engine, a configuration module for geometrydefinition, a weight module for calculating the weight of

components and takeoff gross weight, an atmosphere analysis

module for calculating atmospheric conditions, and a tip-jet

module for calculating the reaction driven system condition,

such as duct loss and mass-flow rate. In this program, thetip-jet

module is only used for a VTOL compound gyroplane

(Leeet al., 2009).

Required power module (trim module)

The rotor of a compound gyroplane is not powered by an

engine. The power comes from the relative airstream directed

upward through the rotor. The rotor of a gyroplane always

operates in an autorotative condition. Therefore, the system

should be solved for a zero-power condition. The forces

acting on the aircraft are shown in Figure 3.

The profile power of the rotor is given as (Leishman, 2004)

CP0 sCd0

8 13m2

3

8m4

1

The net shaft torque is zero because of the autorotative

condition:

CQ CQ 0 CQiCP0 klCT0 2

The inflow ratio is given by Leishman (2004):

l m tan2a CT

2ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffim2 l2

p 3A negative sign preceding the a must be used because the disk

tilts backwards.

In the compound gyroplane, the wing shares the lift with

the rotor. Therefore, the lift sharing factor N is assumed in

advance. In addition, the thrust coefficient of the rotor is

calculated for the thrust vector based on the lift force whichthe rotor should generate:

CT GW:N

rAVR2 cosa4

Equations (2) and (3) are solved simultaneously for the

advance ratio m and the angle of attack of the rotor disc a.

Since autorotation is obtained, the thrust required for the

propeller is calculated as:

Tprop Trotor sina Hrotor cosa Dwing Dfuselage 5

Where the drag force coefficient of the rotor is:

CHsC

d08 2

m 0:5m3

6

The required power for a compound gyroplane at level flight

is then calculated as:

PTpropV

hprop7

Engine cycle module and tip-jet system

The ONX program written for preliminary analysis o

common air-breathing aircraft engine cycles is used. This

program can be used to analyse the design point performance

of an engine cycle with changes in the design flight condition

(altitude, Mach number), cycle design variables (fan pressure

ratio, cycle bypass ratio, compressor pressure ratio, etc.) cycledesign limit (maximum temperature at main burner or

afterburner exit), or component efficiency (main burner

combustion efficiency) (Jack, 1996).

In cases where the tip-jet system is applied to provide hover

capacity for the compound gyroplane, the required torque to

drive the rotor is produced by a force created by the air

ejected through the rotor tip nozzles (Dimitri et al., 1994

Jeon et al., 2008):

Q Fj R 8

Fj _mjVj2VT 9




Volume 83 Number 6 2011 420 428

424



The tip-jet velocity can be calculated based on the assumption

that the flow undergoes an isentropic expansion from the

rotor blades internal pressure to the free-stream pressure

outside the exhaust nozzle (Dimitri et al., 1994; Jeon et al.,

2008):

Vj

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi2RT0d

g

g2 1

12

P1

P0

g21=g" #vuut 10

These modules are additional modules for compound

gyroplane sizing in comparison with the conventional

com pound helicopter sizing process. S om e other

components such as tail rotor and transmission are not

considered in this process.

In general, the flight conditions, initial engine parameters

and lift sharing factor between the rotor and wing data are

input first, and then the compound gyroplane configuration is

decided in the configuration module. The results from

preceding steps are used as input data for the aerodynamic

module and engine cycle analysis module. The lift and drag

data from the aerodynamic module are used for calculating

the installed engine power in the engine cycle analysis

module. Thereafter, the empty weight is estimated based on

the empirical formulation. Fuel weight is calculated according

to a specified mission and is added to the empty weight to get

the total gross weight (TOGW). The discrepancy between

Figure 2Module composition

Engine CycleModule

(Turbofan, Turboprop)

Configuration

Module(Define Geometry)

Weight Trend

Module(Calculate TOGW)

Atmosphere

Module(Calculate Atmosphere

Condition)

Tip Jet ModuleOnly VTOL Compound

Gyroplane

Trim Module(Calculate Power Required)

Mission Analysis

Module(Calculate Fuel Weight)

Aerodynamic

Module(Calculate Lift & Drag)

Figure 3The forces acting on compound gyroplane components

T_propeller

GW

L_wing

D_wing

H_rotor

T_rotor

L_rotor

D_induced

D_body

Source:Ahn and Chae (2009)




Volume 83 Number 6 2011 420 428

425



the calculated TOGW and initial TOGW creates iterations of

the process. Otherwise, the process ends.

The total program process is shown in Figure 4 (Lee et al.,

2010).

Program validation

The Carter Copter, Challis Heliplane, and FB-1 Gyrodyne

were selected to validate the STOL compound gyroplaneprogram, and the Jet Gyrodyne is selected for VTOL

compound gyroplane program validation. In the case of

STOL, the difference between existing data and calculated

data is less than 10 per cent. The rotor-lift sharing and wing

span to rotor diameter ratio (Bw/D) factors all play important

roles in obtaining sizing results. Currently, there are no data

trends that can be used to estimate these factors. Therefore,

an optimisation loop is performed to enhance the sizing

results. Figures 5 and 6 show the trends of Bw/D and N in

response to the TOGW calculated by the sizing program for

the Carter Copter. In general, the takeoff gross weight

increases when the Bw/D increases and N decreases. Other

compound gyroplanes tendencies are the same as those

shown by these graphs (Lee et al., 2010).

In the case of VTOL, the Jet Gyrodyne is used for validation.

The Jet Gyrodyne uses a pressure-jet rotor drive system for

vertical flight, while the sizing program assumes that a tip-jet

system is used for calculating VTOL. However, the sizing

results still show good agreement with existing data. Tables I-IV

show the program results and existing air vehicles data.

Optimisation study on compound gyroplaneThe lack of statistical data trends for compound gyroplanes

leads to the requirement for implementing an adequate sizing

process. In this study, the optimisation problem is performed to

reduce the TOGW. The design variables are Bw/D and N. The

design constraints are defined as the lift to drag ratio (L/D) and

the minimum speed for cruising flight. The design optimization

tools 5.X is employed to perform the optimisation process

The optimal results obtained using sequential linear program,

a gradient-based method, are shown in Tables V-VIII.

The optimal results show that TOGW could be reduced by

altering Bw/D and N without degrading the L/D ratio and

minimum cruising speed performance. The tradeof

between wing span and rotor diameter is a critical issue

Figure 4Sizing program process

Conceptual Sizing Process

ConfigurationRotor Lift Estimation:

Vertical Takeoff (100%)Wing Lift Estimation:

LWing= GW (1-N)Fuselage Sizing

HT, VT Sizing

Pylon Sizing

Wing Sizing

Rotor Disc AreaCalculation

Power Calculation

Duct Loss

Calculation

Vertical Flight

(VTOL)

Low Speed

Cruise Flight

High Speed

Cruise Flight

Wing Lift /Drag

Profile Drag

Rotor Lift /Drag

Aerodynamic

Initial Sizing Results

Max PreqMax Preq

Configuration Data

Yes

NoRevised GW

Empty

Weight

Installed

Power

Gw = WE + PL + Fuel WeightGW(Initial) =

GW(Mission)?

Mission Analysis

Mission SegmentFuel Weight

Total Required Fule

Total Fuelreq

Engine Sizing

Weight

Weight Data

Mission Fuel req.

Aerodynamic Data

Propulsion Data

Maximum Power

Required

Span, Cw, W/SCalculation

DMR, Solidity

Calculation

Mission Profile, Requirements, Assumption Basic Data (Rotor Lift Sharing Factor, Bw/D, Aircraft Lauout)




Volume 83 Number 6 2011 420 428

426



of the compound gyroplane. The lift sharing factor and ratio

(between wing span and rotor diameter) parameters are

assumed in advance in the sizing process. The optimisation

processes were performed in order to identify those parameters

suitable for weight reduction. The optimal results throughout

the validated aircraft showed that the weight can be significant

Figure 5Bw/D vs TOGW

3,200

3,000

2,800

2,600

2,400

Bw/D

2,200

0.1

0.25

0.55

0.85 2.

5 410.

70.

4

TOGW

Figure 6N vs TOGW

3,200

3,000

2,800

2,600

2,400

N

2,200

2,000

0.1

0.2

0.5

0.4

0.8

0.9

0.7

0.6

0.3

TOG

W

Table I Challis Heliplane UAV results (STOL)

Parameter Existing aircraft Output Error (%)

TOGW 662 kg 647 kg 2.3

Empty weight 417 kg 455 kg 8.9

Power 313 kW 324 kW 3.6

Body length 8.13 m 7.5 m 7.8

Rotor diameter 7.67 m 6.95 m 9.4

Main wing span 3.81 m 3.47 m 8.8

HT span 1.78 m 1.77 m 0.5

Table III FB-1 Gyrodyne results (VTOL)

Parameter Existing aircraft Output Error (%

TOGW 2,172 kg 2,100 kg 3.3

Empty weight 1,629 kg 1,496 kg 8.2

Power 388 kW 414 kW 5.7




HT span 3.66 m 3.87 m 6.7

Table IV Jet Gyrodyne results (VTOL)

Parameter Existing aircraft Output Error (%

TOGW 2,177 kg 2,220 kg 2.0

Empty weight 1,633 kg 1,628 kg 0.3

Power 388 kW 359 kW 7.5



Main wing span 5.79 m 6.31 m 8.9HT span 3.66 m 3.78 m 3.3

Table II Carter Copter results (STOL)

Parameter Existing aircraft Output Error (%)

TOGW 1,452 kg 1,375 kg 5.3

Empty weight 907 kg 881 kg 2.9

Power 448 kW 462 kW 3.2

Body length 8.08 m 8.44 m 4.5Rotor diameter 10.24 m 10.94 m 6.8


Main wing area 7.15 m2 6.70m2 6.4

Table V Challis Heliplane optimisation results (STOL)

Problem

composition Initial value Results

Objective (kg) 662 581

Design variables 0.10 # Bw/D # 0.90 0.50 0.39

0.10 # N # 0.90 0.25 0.57

Design constraints L/D $ L/D(baseline) 4.93 4.99

Vmin# Vmin(baseline) 54 k m/h 52 k m/h

Table VI Carter Copter optimisation results (STOL)

Problem


Objective (kg) 1,452 1,253


0.10 # N # 0.90 0.20 0.34



Table VII FB-1 Gyrodyne optimisation results (STOL)

Problem




0.10 # N # 0.90 0.30 0.26






Volume 83 Number 6 2011 420 428

427



reduced by reorganising therelation betweenthe rotor andwing

configuration. The optimal lift sharing factors are around 0.35

for most aircrafts, while the wing span/rotor diameter vary in

wide range according to the TOGW. Large aircraft such as

Gyrodyne require a larger wing span compared to existing

aircraft to reduce the weight.

Conclusion

This study described the characteristics of the compound

gyroplane and its advantages, thereby developing the sizingprogram for this kind of configuration. The sizing process

generated shows that it is appropriate for the conceptual level

of compound gyroplane design. The validations present good

agreement between existing compound gyroplane data and

the estimated data. Although the statistical data of compound

gyroplanes are quite deficient, the authors have developed a

sizing process where the well known HESCOMP program is

based on. Good agreement between some existing gyroplanes

such as the Challis Heliplane, Carter Copter, FB-1 Gyrodyne,

and Jet Gyrodyne and results of the sizing process are shown.

The ratio of the wing span to rotor diameter (Bw/D) and lift

sharing (N) factors should correspond to the size and

performance mission of each gyroplane. However, these

factors are inputs of the sizing process, and thus an

optimisation process is necessary to complement the lack ofexisting data trends. The optimal results show that TOGW

could be reduced by altering Bw/D and N without degrading

the ratio and minimum cruising speed performance.

References

Ahn, B.H. and Chae, H.G. (2009), Gyroplane Level 1 Trim

Analysis Theory Manual, Alpha Engineering, Bear, DE.

Carter, J. Jr (2010), The Carter Heliplane Transport Slowed

Rotor/Compound Aircraft: Candidate for the Air-maneuver

Trasport (AMT), Carter Aviation Technologies, Wichita

Falls, TX.

Choi, S.M. (2010), Multidisciplinary UAV design

optimization implementing multi-fidelity analysistechniques, Master thesis, Aerospace Engineering

Department, Konkuk University, Seoul.

Davis, S.J. and Wisniewski, J.S. (1973), The helicopter

sizing and performance computer program,Users Manual

for HESCOMP, Boeing Vertol Company, Philadelphia, PA.

de la Cierva, J. and Rose, D. (1931), Wings of Tomorrow

The Story of the Autogiro, Brewer, Warren and Putnam

New York, NY.

D im it ri , N. M. , Ta i, J. a nd D an ie l, P. S. (1 994 )

A multidisciplinary design optimization approach to

sizing stopped rotor configuration utilizing reaction drive

and circulation control, paper presented at 5th AIAA

NASA/USAF/ISSMO Symposium on MultidisciplinaryAnalysis and Optimization, Panama City, FL.

Gustafson, F.B. (1971), A history of NACA/NASA rotating-

wing aircraft research, 1915-1970, Vertiflite, American

Helicopter Society, Vol. 1 No. 1, pp. 6-15.

Houston, S.S. (1998), Identification of autogyro

longitudinal stability and control characteristics, Journa

of Guidance, Control, and Dynamics, Vol. 21 No. 3

pp. 391-9.

Jack, D.M. (1996), ONX and OFFX User Guide, American

Institute of Aeronautics and Astronautics, Reston, VA.

Jeon, W.S., Lee, J.W., Byun, Y.B. and Yu, H.Y. (2008)

Rotor performance optimization of the canard rotor wing

aircraft, KSAS Journal, Vol. 36 No. 2.

Johnson, W., Yamauchi, G.K. and Watts, M.E. (2006)Design and technology requirements for civil heavy lift

rotorcraft, Proceedings of the American Helicopter Society

Vertical Lift Aircraft Design Conference, American Helicopte

Society, Alexandria, VA, USA.

Lee, Y.J., Kang, H.J., Kim, J.M., Lee, J.W. and Chung, I.J

(2009), Now and future of compound aircraft

KSAS Magazine, Vol. 3 No. 2, pp. 21-9.

Lee, Y.J., Vu, N.A., Kim, J.M., Kim, S.H., Lee, J.W. and

Chung, I.J. (2010), Design and optimization study on

compound gyroplane aircraft, paper presented a

6th China-Japan-Korea Joint Symposium on Optimization

of Structural and Mechanical Systems, Kyoto.

Leishman, J.G. (2004), Development of the autogiro

a technical perspective, Journal of Aircraft, Vol. 41 No. 4

pp. 765-81.

Leishman, J.G. (2006), Principles of Helicopter Aerodynamics

2nd ed., Cambridge Aerospace Series, Cambridge

University Press, New York, NY.

Newman, S. (2006), The helicopter efficiency or

efficacy?, Aircraft Engineering & Aerospace Technology

Journal, Vol. 78 No. 1, pp. 15-19, Technical Paper.

Prewitt, R.H. (1938), Possibilities of jump-off autogiro

Journal of the Aeronautical Sciences, Vol. 6 No. 1, pp. 10-14

Wheatley, J.B. (1933), Wing pressure distribution and rotor

blade motion of an autogiro as determined in flight

NACA Report 475.

Yeo, H. and Johnson, W. (2008), Optimum design of a

compound helicopter, Journal of Aircraft, Vol. 46 No. 4

pp. 1210-21.

Corresponding author

Jae-Woo Lee can be contacted at: [email protected]

Table VIII Jet Gyrodyne optimisation results (VTOL)

Problem




0.10 # N # 0.90 0.30 0.32






Volume 83 Number 6 2011 420 428

428

To purchase reprints of this article please e-mail: [email protected]

Or visit our web site for further details: www.emeraldinsight.com/reprints

Documents

Configuration design and optimisation study of a compound gyroplane