DTIC ADA523066: Aeromechanics Analysis of a Heavy Lift Slowed-Rotor Compound Helicopter

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by  Defense Technical Information Center

Aeromechanics AnalysisofaHeavyLiftSlowed-Rotor Compound Helicopter
HyeonsooYeo WayneJohnson
AeroflightdynamicsDirectorate(AMRDEC) FlightVehicleResearchandTechnologyDivision
U.S.ArmyResearch,Development,andEngineeringCommand NASAAmesResearchCenter
AmesResearchCenter,MoffettField,California MoffettField,California
Abstract
A heavy lift slowed-rotor tandem compound helicopter was designed as a part of the NASA Heavy Lift
Rotorcraft Systems Investigation. The vehicle is required to carry 120 passengers over a range of 1200
nautical miles and cruise at 350 knots at an altitude of 30,000 ft. The basic size of the helicopter
was determined by the U.S. Army Aeroflightdynamics Directorate’s design code RC. Then performance
optimization and loads and stability analyses were conducted with the comprehensive rotorcraft analysis
CAMRAD II. Blade structural design (blade inertial and structural properties) was carried out using the
loading conditionfrom CAMRAD II. Performanceoptimizationwas conductedto find the optimum twist,
collective,tipspeed,andtaperusingthecomprehensiveanalysis. Designswerealsodevelopedforalternate
missionstoexploretheinfluenceofthedesignconditiononperformance.
Notation SFC specificfuelconsumption
SHP shafthorsepower
A rotordiskarea SLS sealevelstandard
C dragcoefficient SOA stateoftheart
D
C skinfrictioncoefficient VTOL verticaltakeoffandlanding
f
C rotorthrustcoefficient
T
C rotorweightcoefficient
W
D/q airframedragdividedbydynamicpressure Introduction
L/D aircrafteffectivelift-to-dragratio
M Machnumber TheNASA HeavyLiftRotorcraftSystemsInvestigation
Mat advancingtipMachnumber wasconductedtoidentifycandidateconfigurationsfora
P aircraftpower large civil VTOL transportthat is technicallypromising
Preq requiredpower and economically competitive [1]. The vehicle is
R rotorradius required to carry 120 passengers over a range of
Swet wettedarea 1200 nautical miles and cruise at 350 knots at an
V flightspeed altitude of 30,000 ft. A large civil tandem compound
Vbr bestrangeflightspeed (LCTC)helicopterwasdesignedasoneofthecandidate
W grossweight configurations to meet this NASA 15-year notional
W/A diskloading capability. Therotorcraftnotionalcapabilitiesandsector
µ advanceratio technologygoalsareinTables1and2,respectively.
! airdensity
" solidity The compound helicopter is one of the methods of
achievinghighspeedcapabilitywhileretainingthehover
HOGE hoveroutofgroundeffect advantagesof a helicopter. The compoundhelicopter is
ISA internationalstandardatmosphere defined as a helicopter with both a wing and auxiliary
MCP maximumcontinuouspower propulsion. In general, the lifting and propulsive
MRP maximumratedpower force capabilities of a helicopter rotor decrease with
OEI oneengineinoperative forwardspeedasa resultofasymmetricflowconditions
encountered by the rotor. The compound helicopter
PresentedattheAmericanHelicopterSocietyInternationalVerticalLift circumvents these limits by sharing lift between the
AircraftDesignConference,SanFrancisco,California,January18-20,
2006. wing and rotor as well as eliminating the need for rotor
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1. REPORT DATE 3. DATES COVERED
JAN 2006 2. REPORT TYPE 00-00-2006 to 00-00-2006
4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
Aeromechanics Analysis of a Heavy Lift Slowed-Rotor Compound
5b. GRANT NUMBER
Helicopter
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S) 5d. PROJECT NUMBER
5e. TASK NUMBER
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
US Army Aviation and Missile Command,Army/NASA Rotorcraft REPORT NUMBER
Division,Army Aeroflightdynamics Directorate (AMRDEC),Moffett
Field,CA,94035
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)
11. SPONSOR/MONITOR’S REPORT
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13. SUPPLEMENTARY NOTES
14. ABSTRACT
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Standard Form 298 (Rev. 8-98)
Prescribed by ANSI Std Z39-18
propulsive force. To maintain low rotor drag at high and produces the stability results. The aerodynamic
speed,itisnecessarytoslowtherotor. model includes a wake analysis to calculate the
rotor nonuniform induced-velocities, using rigid,
This paper presents the results of the heavy lift slowed-
prescribed, or free wake geometry. CAMRAD II has
rotor tandem compoundhelicopter design investigation.
undergone extensive correlation of performance and
It describes the approach used for developing the
loads measurements on helicopters [5–7]. A complete
design. The complete design is presented together with
aeroelastic model was developed for the analysis of the
an optimization study conducted. Designs were also
compoundhelicopter.
developedforalternatemissionstoexploretheinfluence
ofthedesignconditiononperformance. A low weight rotor system is an important goal for the
design of a heavy lift helicopter. Blade structural loads
calculations were used to design composite rotor blade
DesignApproach
sections, and the resulting blade structural and inertial
properties were used to repeat the loads and stability
The design process of the heavy lift slowed-rotor
calculations.Thebladecrosssectiondesign/optimization
tandem compound helicopter is shown in Fig. 1.
proceduresweredevelopedtoachievethetargetedweight
Rotorcraft behavior is inherently multidisciplinary and
reduction, while satisfying the stiffness and strength
its design is fundamentally an iterative process. The
requirements.
basic size of the helicopter was determined by the
U.S. Army Aeroflightdynamics Directorate’s design
code RC [2]. Then performance optimization and MissionandDesignConditions
loads and stability analyses were conducted with the
comprehensive rotorcraft analysis CAMRAD II [3]. The mission is to transport120 passengersovera range
Blade structural design (blade inertial and structural of 1200 nautical miles. The payload comprises 120
properties) was carried out using the loading condition passengers at 220 lb each (190 lb + 30 lb baggage), 2
from CAMRAD II [4]. The design process was flight crew at 240 lb each and 3 cabin crew at 210 lb
completed when the vehicle performance, loads, and each. The design mission and power requirements are
stabilityresultsdidnotchangebetweeniterations. describedinTable3. Althoughtheaircraftwasdesigned
to the mission defined in Table 3, hence with very little
Rotorcraft sizing processes parametric equations and
hover time (2 minutes), efficient hover and low speed
semi-empirical math models with designer inputs. RC
capability is essential for a VTOL transport. This is
iterates on the rotorcraft design (engine size, rotor
reflectedintherequirementforOEIhovercapability.The
diameter,grossweight,etc.) untilitreachesaconverged
resulting designs optimize at balanced cruise and OEI
solutionthatmeetsdesignrequirements(payload,range,
hoverpower[8].
etc.). During each step of the iteration cycle, RC also
conducts design-critical flight and mission performance Critical design conditions appropriate for civil heavy
analysis. TherotorperformancemodelintheRC sizing lift rotorcraft operations were defined for calculation
code was calibrated using the performance calculated of performance, loads, and stability. Table 4
by CAMRAD II, and the sizing task repeated. An summarizes these aeromechanics analysis conditions.
estimate of the drag of the airframe was used to The comprehensive analysis code was used to conduct
define the aerodynamic model for the sizing code and theaeromechanicalanalysisofTable4.
the comprehensive analysis. In the current analysis,
the sizing code incorporated significant weight savings
(relative to current technology scaled to large size) as TechnologyFactorsandDesignParameters
a result of structure, drive train, and engine technology,
such as new materials, new design methods, new High speed, high altitude, and long range are required
operatingprocedure,etc. tomeetthetechnologygoalsofthecurrentinvestigation.
The heavylift rotorcraftmusthave lowdisk loadingfor
CAMRAD II is an aeromechanics analysis of
good hover efficiency, and low drag for efficient cruise.
rotorcraft that incorporates a combination of advanced
Thetargetforimprovementinhoverefficiencyimpliesa
technologies, including multibody dynamics, nonlinear disk loading of about W/A = 10 lb/ft2. The actual disk
finite elements, and rotorcraft aerodynamics. The
loadingofthedesignwasdeterminedbasedonminimum
trim task finds the equilibrium solution for a steady
aircraftweight,power,andcost.
state operating condition, and produces the solution
for performance, loads, and vibration. The flutter Figure 2 shows historic trends for aircraft drag. For
task linearizes the equations about the trim solution, the current heavy lift rotorcraft investigation, the target
2
airframe and wing drag was D/q = 1.6(W/1000)2 3. loads, and stability calculations were performed for the
Thisdraglevelis higherthancurrentturbopropaircraft, conditions defined in Table 4. The comprehensive
although about 24% lower than is customary in the analysis modeled the auxiliary propulsion as forces
helicopter industry. Consequently, good aerodynamic applied to the airframe. Rotor/rotor and rotor/wing
designpracticeshouldbesufficientto achievethetarget interference were accounted for using the vortex wake
for airframe drag. Figure 3 shows historic trends model. For all the calculations made in this study, an
for rotor hub drag. In cruise, hub drag must be elasticblademodelwasused.
added to the airframe and wing drag of the aircraft.
Inhoverandlowspeedflight,standardtandemhelicopter
For this investigation, the target hub drag was D/q =
0.4(W/1000)2 3, which is less than half of current hub controls, plus aircraft pitch and roll attitude, could be
used to trim this aircraft. At moderatespeeds, the pitch
drag levels. Achieving this hub drag level will require
angle could be fixed and the propeller thrust trimmed
advancedtechnology,certainlyfairingsbutpossiblyalso
instead. Even at low speeds, the lateral stick would be
activeflowcontrol.
connected to the ailerons, and the longitudinal stick to
An assessment of engine and drive train technology theelevator.
was made in order to define and substantiate the sizing
code models. The engine model represents what can Loadfactorsweepwasconductedat80knots,sealevel,
be obtained from (or required of) a modern technology 650 ft/sec tip speed. The turn rate was increased to
engine. A drive train concept was developed for the achieve a load factor of up to 1.5g. The analysis was
heavyliftrotorcraftdesigndescribedhere[9]. conducted using nonuniform inflow with a free wake
geometry. For the load factor sweep (to obtain blade
Basic parameters of the rotorcraft were chosen based loads),themeanpropellerthrustwasfixedattheaircraft
on an assessment of current and future technology, as drag value, and the pilot’s controls (collective, and
shown in Table 5. The rotor blade loading (CW " longitudinal and lateral cyclic pitch), aircraft pitch and
= 0.141, based on gross weight and thrust-weighted rollattitude,aircraftlateralstick(connectedtoailerons),
solidity)waschosenbasedonlowspeedmaneuverability andpedal(connectedtodifferentialpropellerthrust)were
requirements. TheCW "valuecorrespondstoaboutan used to trim the aircraft. In addition, rotor flappingwas
8% improvementin maximum lift capability, compared trimmed to zero (for load control). Thus, there were 10
to current technology. A relatively low hover tip speed trimvariablesfortheloadfactorsweep.
(650 ft/sec) was used, reflecting the importance of the
noisegoal. Thecruisetipspeedwaschosentooptimize In cruise, the aircraft was trimmed using lateral stick to
the performance. Hover download value used in this the ailerons, longitudinal stick to the elevator, pedal to
study is consistent with current technology. A low differential propeller thrust; plus propeller thrust, and
wing loading(80lb/ft2) was chosenforgoodlowspeed aircraft pitch and roll angles. Front and rear rotor
maneuverabilityandawideconversionspeedrange.The collective pitch angles were set to values optimized for
totaldrag(D/q/(W/1000)2 3)was1.9. Table6showsthe cruiseperformance(optimizedrotorthrust). Inaddition,
cruisedragbuildup. rotor flapping was trimmed to zero (for load control)
usingrotorcyclicpitch;thustherewere10trimvariables
forcruise.
SummaryofDesign
A hingeless rotor hub was used. To reduce mean
The heavy lift slowed-rotor compound helicopter blade lag bendingmoment, the hub incorporated0.006-
configurationdevelopedinthisstudyisshowninFig.4. R torque offset. Blade structural design (blade inertial
Theaircrafthastwomainrotorsintandemconfiguration, andstructuralproperties)wasperformedusingtheblade
ahighwing,pusherpropellersforcruisepropulsion,and loads for the load factor sweep. The half peak-to-peak
ahorizontaltail. Thelengthofthefuselagefollowsfrom bladeflapandlagbendingandtorsionmomentvaluesat
thespecificationofthepayload,andthediskloadingwas 50%R of the frontrotor blade are shown in Fig. 5. The
optimized to balance the cruise and hover power. As a highest load factor used was 1.48 with the turn rate of
result,therewasnooverlapoftherotors. Thetworotors 15 deg/sec. The blade loads for the load factor sweep
are separated by 90 ft horizontally and 5.8 ft vertically. werehigherthanthoseforthelevelflightspeedsweepas
The shaft incidence is 0 deg for both forward and rear showninFig.6.
rotors.Thehorizontaltailwassizedbytrimrequirements
Figure 7 shows the calculated blade frequencies, at a
ratherthanstability.
collectivepitch angleof 10 deg. Athelicopter-modetip
Table7showsthecharacteristicsoftheheavyliftslowed- speeds,thelagfrequencywasabove6/revandthetorsion
rotortandemcompoundhelicopterdesign. Performance, frequencyabout7.5/rev. Rotor stability calculation was
3
conductedinhoverandforwardflightcondition.Figure8 meritwereexaminedbyreplacingthecompoundtandem
shows damping ratio as a function of thrust at sea level rotor quantities with the conventional rotor quantities.
standardcondition. Nostabilityissueswereobservedup Figure12showstheparametricstudyresults. Thetwist,
to CT " of 0.2, although the damping ratio of the 2nd taper, and tip speed increased the figure of merit at low
flap mode was significantly reduced for CT " of larger blade loading, but decreased it at high blade loading.
than 0.18. Figure 9 shows stability calculations in level The biggest influence came from the airfoil change. A
flight for 30K ISA condition. No stability issues were significant reduction of the hover figure of merit was
observedupto500knots. observed at high blade loading and the trend became
similartotheconventionalrotor.Itappearsthatthestate-
Performance results from the comprehensive analysis of-the-art airfoils used for the compound tandem rotor
are shown in Figs. 10 and 11. These results are design have a strong influence on the figure of merit
for the state-of-the-art rotor airfoils. The final design trend.
was obtained using an optimum twist of 0 deg inboard
(0.0R to 0.5R) and -12 deg outboard (0.5R to 1.0R),
PerformanceOptimization
an optimum collective angle of -2 deg, and a taper of
0.8 (tip/root chord). These performance optimization
This section describes performance optimization
resultswillbefurtherdiscussedinthenextsection. The
conducted with the comprehensive analysis. The blade
hover figure of merit of an isolated rotor is calculated
twistwasvariedtooptimizetherotorforhoverandcruise
for 5k/ISA+20oC condition with 650 ft/sec tip speed.
performance. The hover condition was 5k/ISA+20oC,
The results are shown in Figure 10. The calculation
wasconductedusingnonuniforminflowwithafreewake 650ft/sectipspeed,CT "=0.149.Thecruisecondition
was 350 knots, 30k ISA, 205 ft/sec tip speed, 138,764
geometry. The figure of merit increases as the thrust
lb gross weight. The twist distribution had two linear
increasesuptoaroundCT "=0.18,andthendecreases.
segments, inboard (0.0R to 0.5R) and outboard (0.5R
The figure of merit is around 0.73 at the design thrust
to 1.0R). Figure 13 presents the results for twist
(CT "=0.149).Figure11showstheaircraftlift-to-drag
optimization. Foreachvalueofoutboardtwist(-15,-12,
ratio at 30,000 ft. The calculation was conductedusing
-9, -6, -3, and0 deg), the inboardtwist valuesare -3, 0,
nonuniform inflow with a prescribed wake geometry.
3, and 6 deg. Two linear twist segments perform better
Rotor/rotor and rotor/wing interference were included
thanasinglelineartwistdistributionasshowninFig.14.
in the comprehensive analysis model. The speed was
A large negativetwist improveshover performance, but
varied from 250 to 450 knots; with the rotor tip speed
the zero twist gives the best cruise performance. The
decreased from hover to cruise speed (350 knots) to
optimum twist of 0 deg inboard and -12 deg outboard
maintain Mat = 0.8 and then 205 ft/sec tip speed was
wasselectedbasedonthehover-cruisecompromise.The
maintained up to 450 knots. The rotor performance
optimum twist shows almost same (0.3% improvement)
in cruise is presented in terms of aircraft L/D=WV/P,
hoverfigureof meritas the -9 deg linear twist case, but
calculated without accessory or other losses, and using
theaircraftL/Dwas1.6%largerthanthatforthe-9deg
apropellerefficiencyof0.86(fromthesizingcode).The
lineartwistcase.
aircraftlift-to-dragratio decreasesas speedgoesup. At
the design cruise speed, the aircraft lift-to-drag ratio is Collectivepitchofthefrontandrearrotorswasvariedto
10.14. find theoptimumrotorthrustforhighspeedcruise. For
anuntwistedrotor,thebestaircraftperformancewouldbe
The maximum hover figure of merit of the compound
obtainedwith zerocollective(nolift, noinducedpower,
tandem rotor occurs at around CT " = 0.17 (Fig. 10), minimum profile power). With negative outboardtwist,
which is high compared with many conventional
forimprovedhoverperformance,theoptimumcollective
helicopterrotors. Thefigure ofmeritfora conventional
anglewas-2degforbothfrontandrearrotors,asshown
articulated rotor was calculated and compared with that
in Fig. 15(a). The optimum collective angle resulted in
of the compound tandem rotor, as shown in Fig. 12.
therotorscarryingabout6.8%oftheaircraftlift(therotor
The conventional rotor had 7 blades, existing airfoils,
thrustvariationwith collective was negativeat this high
and typical solidity, twist, tip speed. The maximum
advance ratio), as shown in Fig. 15(b). This optimum
figureofmeritoftheconventionalrotoroccurredatlow
occurredwithasmall,positiveshaftpowertotherotors.
bladeloadingand thefigureof meritvaluedecreasedas
Withtherotorinautorotation(achievedusinganafttiltof
the blade loading increased. A parametric study was
therotor)therotorthrustwaslarge,hencethetotalrotor
conducted to examine the differences in the figure of
draglargerandtheaircraftL/Dsomewhatsmaller.
merit trend. The parameters investigated in this study
are twist, taper, tip speed, and airfoils. The effects of The rotor advancing tip Mach number was varied from
those parameters on the prediction of hover figure of 0.7 to 0.9to find the optimumrotorrotationalspeed for
4
highspeedcruiseflight,asshowninFig.16.Tomaintain altitude increases because the lower density makes it
low rotor drag at high speed, it is necessary to slow the moreefficientforthewingtogeneratetherequiredlift.
rotor.TheoptimumcruiseperformancewasfoundatMat
=0.80(fortheairfoilsused). Furtherreductionsinrotor
rotationalspeeddidnotimprovetheaircraftL/D. Conclusions
ThebladetaperwasvariedasshowninFig.17.Thetaper A heavy lift slowed-rotor compound helicopter was
model considered was constant thrust-weighted solidity designed as a part of the NASA Heavy Lift Rotorcraft
(chordat75%R).TheaircraftL/Ddecreasedasthetaper Systems Investigation. The vehicle is required to
wasreduced.Althoughthetaperof1.0producedthebest carry 120 passengers over a range of 1200 nautical
aircraftL/D,thetaperof0.8(tip/rootchord)wasselected miles and cruise at an altitude of 30,000 ft at 350
toreducethebladeweight. knots. The basic size of the helicopter was determined
by the U.S. Army Aeroflightdynamics Directorate’s
design code RC. Then performance optimization and
AlternateMissions
loads and stability analyses were conducted with the
comprehensive rotorcraft analysis CAMRAD II. Blade
Theslowed-rotorcompoundhelicopterwasalsosizedfor
structuraldesign(bladeinertialandstructuralproperties)
analternatemission,composedofthree400nmsegments
was carried out using the loading condition from
(takeoff, climb, cruise at 30k, descent, and landing;
CAMRAD II. Performanceoptimization was conducted
with one reserve segment), instead of a single 1200 nm
to find the optimum twist, collective, tip speed, and
segment. Table 8 shows the aircraft designed for the
taperusingthecomprehensiveanalysis. Thefinaldesign
alternatemission. Theadditionalclimbanddescenttime
showed an efficient hover and cruise speed capability
inthe3x400missionresultedinheavieraircraftcarrying
(hoverfigureofmeritof0.73andaircraftlift-to-dragratio
more fuel. Thus, the aircraft required longer and wider
of 10.14), withoutany stability issues either in hoveror
rotorblades.
inhighadvanceratioforwardflight.
To explore the influence of the design condition on
Designs were also developed for alternate missions
performance, the performance optimization and aircraft
to explore the influence of the design condition on
sizingwereperformedforthefollowingalternatedesign
performance. In this study, both tandem main rotors
cruiseconditions:
and a single main rotor configurations were developed.
Therotor/rotorinterferenceresultedinasmallreduction
a)30kISAand350knots
in aircraft L/D for the tandem configuration compared
b)20kISAand350knots
to the single main rotor. The efficiency improves as
c)20kISAand250knots
altitude increases because the lower density makes it
d)10kISAand250knots
e)5kISA+20oCand250knots moreefficientforthewingtogeneratetherequiredlift.
In this study, designs were developed for both tandem
References
main rotorsanda single mainrotor configurations. The
comprehensive analysis was used to optimize the rotor
[1] Johnson, W., Yamauchi, G. K., and Watts, M. E.,
performance. The comprehensive analysis results were
“Design and Technology Requirements for Civil
used to estimate aircraft L/D=WV/P as a function of
HeavyLiftRotorcraft,”ProceedingsoftheAmerican
flight speed, as shown in Fig. 18. The performance
Helicopter Society Vertical Lift Aircraft Design
calculation used the disk loading of 15 lb/ft2 and total
Conference,SanFrancisco,CA,January2006.
dragD/q/(W/1000)2 3 = 1.9. Thenumberofbladeswas
increasedtosixtoobtainareasonablechordlength. The
[2] Preston, J., and Peyran, R., “Linking a Solid-
optimum twist was 0 deg inboard (0.0R to 0.5R) and -
Modeling Capability with a Conceptual Rotorcraft
12 deg outboard (0.5R to 1.0R), same as the baseline,
Sizing Code,” Proceedings of the American
and the taper was 0.8 (tip/root chord). The optimum
Helicopter Society Vertical Lift Aircraft Design
tip speedwas foundto be Mat = 0.60 for5k ISA+20oC Conference,SanFrancisco,CA,January2000.
and 250 knots, Mat = 0.65 for 20k ISA and 250 knots
and for 10k ISA and 250 knots, and Mat = 0.85 for [3] Johnson, W., “Technology Drivers in the
30k ISA and 350knotsand for 20k ISA and 350knots. Development of CAMRAD II,” Proceedings of
Therotor/rotorinterferenceresultedinasmallreduction the American Helicopter Society Aeromechanics
in aircraft L/D for the tandem configuration compared Specialist Meeting, San Francisco, CA, January
to the single main rotor. The efficiency improves as 1994.
5
[4] Zhang,J.,andSmith,E.,“DesignMethodologyand [7] Yeo, H., and Johnson, W., “Comparison of Rotor
Analysis of Composite Blades for a Low Weight Structural Loads Calculated Using Comprehensive
Rotor,” Proceedings of the American Helicopter Analysis,” Proceedings of the 31st European
Society Vertical Lift Aircraft Design Conference, RotorcraftForum,Florence,Italy,September2005.
SanFrancisco,CA,January2006.
[8] Johnson, W., Yamauchi, G. K., and Watts,
[5] Yeo, H., Bousman, W. G., and Johnson, W.,
M. E., “NASA Heavy Lift Rotorcraft Systems
“Performance Analysis of a Utility Helicopter with
Investigation,” NASA TP-2005-213467, September
Standard and Advanced Rotor,” Journal of the
2005(inpublication).
American Helicopter Society, Vol. 49, No. 3, July
2004. [9] Handschuh, R. F., “Current Research Activities in
[6] Yeo, H., and Johnson, W., “Assessment of Drive System Technology in Support of the NASA
ComprehensiveAnalysisCalculationofAirloadson Rotorcraft Program,” Proceedings of the American
HelicopterRotors,”JournalofAircraft,Vol.42,No. Helicopter Society Vertical Lift Aircraft Design
5,September-October2005. Conference,SanFrancisco,CA,January2006.
Table1 Rotorcraftnotionalvehicle15-yearcapabilities.
Payload 120passengers
Cruisespeed M=0.60(350knots)at30,000ft
Range 1200nm
Operations Automatedsingle-pilotCATIIICSNIforheavylift
Table2 Rotorcraftvehiclesector15-yeartechnologygoals.
Hoverefficiency,W/P 6
Efficientcruise,L/D 12
Emptyweightfraction 0.41
Communitynoise SOA-14EPNdb
Flightcontrol Automatedsingle-pilotCATIIICSNI
AdvancedengineSFC SOA-10%
AdvancedengineSHP/W SOA*120%
Cabinnoiseandvibration 77dBA&0.05g
6
Table3 Designmission.
1200nmrange,120passengers
Cruiseat350knotsand30,000ft(min22,000ft,foricing)
Designmission
Idle5min
o
Takeoff+1minHOGE 5kISA+20 C
[convert]
ClimbatV (0kISAto30kISA,distancepartofrange)
br
Cruiseat350knots,for1200nmrange 30kISA
Reserve:30min+30nmatV 30kISA
br
DescentatV (norangecredit)
br
[convert]
o
1minHOGE+Landing 5kISA+20 C
Idle5min
Designpower
o
Hover:95%MRP,5kISA+20 C
Cruise:100%MCP,30kISA
Oneengineinoperative(OEI)
o
at5kISA+20 C,133%(OEIMCP)greaterthan90%(HOGEPreq)
at22kISA,(OEIMCP)greaterthan(PreqatVbr)
4engines
Table4 Criticaldesignconditionsforaeromechanicsanalysis.
Bladestability
Thrustsweepinhover(SLS),torotorstall
Levelflightspeedsweep(30kISA),tomaximumpower
Performance
Thrustsweepinhover(5kISA+20oC),forpowerandfigureofmerit
Speedsweepinhighspeedforwardflight(30kISA)forpowerandefficiency
Loads(blade,hub,control),deflection,andvibration
Loadfactorsweepat80knots(SLS),to1.5g
Levelflightspeedsweep(30kISA),tomaximumpower
Table5 Advancedtechnologyestimates.
HoverCW ",(5kISA+20oC) 0.141
Hoverdownload 5.7%
Tipspeed,hover ft/sec 650
Tipspeed,cruise ft/sec 205
Cruisespeed,30k knots 350
Drag,(D/q)/(W/1000)2 3 ft2 1.9
Wingloading lb/ft2 80
7
Table6 Cruisedragbuildup.
WingD/q 15.84
Area 1735
C .0091
D
BodyD/q 12.42
Swet 3650
C .0021
f
Interference 4.86
HorizontaltailD/q 1.92
Area 217
PylonD/q 9.39
HubD/q 10.72
HubD/q/(W/1000) 2 3 .40
TotalD/q 50.28
D/q/(W/1000)2 3 1.88
Table7 Characteristicsoftheheavyliftslowed-rotortandemcompoundhelicopterdesign.
MissionGW(lb) 138,764
Engines(hp) 4x9684
Missionfuel(lb) 17,902
Rotordiameter(ft) 76.7
DiskloadingW/A(lb/ft2) 15
CW "(geom,5kISA+20oC) 0.133
CW "(T-wt,5kISA+20oC) 0.141
Tipspeed(ft/sec) 650/205
maximumMat 0.80
Solidity 0.1321
Numberofblades 4
Chord(75%R,ft) 3.98
Aspectratio 9.6
Taperratio 0.8
DragD/q(ft2) 50.3
(D/q)/(W/1000)2 3 1.9
Wingloading(lb/ft2) 80
Area(ft2) 1735
Span(ft) 144
Aspectratio 12.0
Cruisepower(hp) 14,724
CruiseL/D=WV/P 10.14
8
Table8 Designsforalternate(three400nmsegments)mission.
Grossweight(lb) 155,540
Enginepower(hp) 4x10,819
Missionfuel(lb) 24,894
Rotordiameter(ft) 81.2
DiskloadingW/A(lb/ft2) 15
CW "(T-wt,5kISA+20oC) 0.141
Numberofblades 4
Chord(75%R,ft) 4.22
Wingloading(lb/ft2) 80
DragD/q(ft2) 55.0
sizing propulsion system
noise
RC airframe aerodynamics
handling qualities
performance opt
CAMRAD II
rotor airfoils
blade aerodynamics
loads, stability
CAMRAD II
hub concept
blade structural
design materials
noise
control concept
vibration
flight profiles
weight, performance, drag
resolve differences with RC
Fig.1 Designiterationprocess.
9