1、90 FTM 7Advanced Rotorcraft Transmission Program -A Status Reviewby: Raymond J. Drago and Joseph W. Lenski, Jr., Boeing Helicopters,iIIAmerican Gear Manufacturers AssociationTECHNICAL PAPERAdvanced Rotorcraft Transmission Program - A Status ReviewRaymond J. Drago and Joseph W. Lenski, Jr.Boeing Heli
2、coptersThe Statements and opinions contained herein are those of the author and should not be construed as anofficial action or opinion of the American Gear Manufacturers Association.!i,I i,ii l,1Copyright 1990American Gear Manufacturers Association1500 King Street, Suite 201Alexandria, Virginia, 22
3、314October, 1990ISBN: 1-55589-559-XAdvanced RotocraftTransmission Program- A Status Report -Raymond J. Drago, PE aircraft design where the drive system benefits can beadvanced gear and bearing materials; double helical incorporated into the basic vehicle sizing. In this case,planetary gear mesh; and
4、 helical gearing throughout the the reduced transmission weight has a spin-off effectrest of the drive train. The speed reduction taken in the with lower gross weight which can perform the sameplanetary stage, at roughly 5.1:1, is slightly higher than mission. The effect on major aircraft design par
5、ameterstypical rotorcraft planetary reductions which are usually is illustrated in Figure 6. The advanced drive systemin the range of 3 or 4:1. This configuration resulted in contributes greatly to a reduction in vehicle grossa lightweight compact design and high reliability gains weight and empfi w
6、eight. Also, engine size can beare expected through a significant reduction in parts reduced from 4038 HP to 3724 HP. The reduction incount, vehiclegrossweightand enginepowerratingwiUfactorinto the acquisition cost of such a vehicle.-4-XMSN Weight (LB) II r 00o(u=, 1,802 WITH EXTERNAL_ FUEL“r.CNKS D
7、ES,UN_U_ I , 5 0 0 -1000- -=RADIUSDESIGN_/ _EL 13590-i I 1,250 -50 100 150 200 250 3(I 350 400_s_oN l_mnJs_0 Baseline ARTFigure 5. ART A/C Mission PerformanceVehicle Gross Weight LB)18,00017,17017 ,000 -16,224In addition toi n,J.mrrove_ aircraft ,-,4ve,_ormance, the ART z 6, o oo -technology will al
8、so impact the TIR aircraft flyawaycost. Cost studies were conducted comparing baseline 15,000 -and a modified ART aircraft. To evaluate the effect onflyaway cost, a series of trend studies were conductedbased upon the assumptions defined in Table 2 14,000- Baseline ARTconcerning the parameters that
9、influence the economicaspects.Installed Power (HP)4,5004,0384,000 -Table 2. Initial Values to Establish Baseline 3,7 24Cost Comparison3,500 -ProfitFactor 10%Number of Prototypes in Development 3 3, o oo -Program B a s e l i n e A R TTotal Number of Production Aircraft 600Number of Ground Test Articl
10、es 1 weight Empty (LB)iI,O00Number of Flight Test Hours 2000 1o, 7 5 9Time Between Engine Overhauls, Hrs 5000 z 0,5 0 0 -Time Between Dynamic System 3500 9, 97 0Overhauls,Hrs 1o, ooo-Transmission System Used Entire Flight? Yes 9, 5 00Annual Interest Rate on Capital 10%Depreciation Period (Yrs.) 25 9
11、, 0 00 - Baseline ARTResidual Value 0Annual Utilization 420 Figure 6 - ART Effect on A/C Design ParametersCustomerAircraftBuy 60 per Year-5-The results of these studies are summarized in Figures production run of 600 TrR aircraft or an approximate7 and 8. In Figure 7, the greatest cost reduction occ
12、urs cost reduction of $.5 million per aircraft.for the dynamic system which is the result of theimprovements identified in the ART drive system. This _smN_ rorAm.=,Mmresults in a 14% reduction in drive systems cost based _ t_,NSm_SStONTOmSM,.7,t-_upon a 600 TIR A/C production run. The reduction indr
13、ive system cost also had some smaller effects on theengines (7%) and airframe (2%) cost reductions. Whenthe component cost breakdown were incorporated intothe flyaway cost, the cost reduction has been reduced _caArrFLYAWAYto approximately 4%. Although the drive system cost cosyreduction is quite sig
14、nificant, the drive system only la_makes up 10% of the total aircraft cost. The costimpact of ART will still result in a savings ofapproximately $250,000 per aircraft or a total programsavings of $150,000,000 for a 600 A/C production run.This cost savings represents a significant payback on ,a_ _rt
15、sr,_s r_rALthe cost of the ART technology program. It isanticipated that additional cost savings will be achieved Figure 8 - Aircraft Flyaway Cost Comparisonwhen improved MTBRs are included in the operatingcost of the TTR aircraft. The results of this studyshown in Table 3 indicates a 27% reduction
16、in life cyclecost when ART is incorporated. This is an additionalsavings of $152,552 for a 600 A/C fleet. s_smu_totAL=s_sa_ Table 3. Comparative CosP Estimates AitT TRANSMISSION TOTAL ffi SM5,13 (-,4%4I3 .COSTSBAdSIKOON_c_oot_noN_ Line ghter weight, longer fatigue life and improvement in surface fat
17、igue may also accruecorrosionresistance,it is expectedthat the use of . hybrid bearings can make a significantimpact toward .achieving the design goals of the ART transmission _,-_r-_,.,.t _*/_J .i,_, f,rj:- .: _? ;.j t.“.,i,le_#7:;/.:f_,_ _x #_Boeing Helicopters plans to test the hybrid bearing _:-
18、_:-“;._“:,lm,/.-.,:“_;_ “ “ “concept in a CH-47 engine transmission to compare _;-s.t: - -“._:-“-: :=_these results with standard bearing operation. Extensive ._ q_:)-_,_-._ t _N_Ntesting is planned to evaluate these bearings over a _-“-“_“_-“-_2.: ;!:il!i_:C_:_:_/ 2_wide range of operating conditio
19、ns Included in these x_. i, _i_! ,_,v ,.,.tests will be the reduction in oil supply, the use of new _._. _J_ _ilubricants and the determination of heat generation _rates.PANC#*KEroRaI_ U_D _I_ _d_._. Precision Net Forged Spur GearsFigure 1_ - Standard Forged GearsPrecision, near net shape forging of
20、 helicopter gearsoffers a considerable number of advantages in thedesign of Advanced Rotorcraft Transmissions becausethis process has shown the potential for:1St_CO_T REDUCIIONa. Reducing machining, material and “_“_*_*_*energyrequirementsb. Increasingfatiguelife _ ._I_1c. Improving the endurance li
21、mit. ,_,_Thus,theprocesscanbe expectedtocontributedirectly . . _Itl_AI;ItiE1 _H_PE FONG_-DGEJ_I_ I_PF_EO _L;z I I I I I I I15 4.0 Itt 5.1 1,1 Ik_ 1./_lilllrl blK MII I I I J tlol,aLI ZI 10 14 11_., , -,_ lailirl i IWklFigure 19 - Scoring, Std & HCR-NIFFigure 1“/- Comparison of Std. & HCR ContactsPre
22、vious NASA Testing (Reference 1) of very smallUnfortunately, the extended contact associated with gears using this tooth form indicated, as shown inHCR involute gears also results in higher sliding Figure 18, that their surface load capacity wasvelocities and lower relative curvature radii at the su
23、bstantially higher than that of conventional involuteextremes of contact thus reducing both the scoring gears and that their bending load capacity (at equalresistance and surface durability of the gears. This stress) was at least equal to and actually slightly greatereffect is largely counteracted b
24、y the improved load than the standard involute gears.- 12-The scoring resistance of the HCR-NIFgears, however, Among the several ways in which the gear toothdid appear, as Figure 19 indicates, to be lower than meshing forces may be reduced, two of the mostthat of equivalent standard involute gears.
25、The lower directly applicable to helicopter transmissions are thescoring load capacity performance may have been due form of the teeth and the overall contact ratio 2. Bothto inadequate profile modification on the small test approaches are quite attractive for an aerospacegears. This design effort w
26、ill, therefore, concentrate on application since, unlike other “treatment“ methods,modifying the HCR-NIF gears so that their scoring load which are applied with penalties to either system weightcapacityis improved, or performance, these approaches have the potentialfor reducing noise without causing
27、 any increase inGut type _mum overall system weight or reducing performance. In fact,Htctz_tross, both approaches also offer the possibility of actuallyNfm_l) providing improved gear performance in terms of0 $ta_rd 1_3_10_2_0000t longer life, higher load capacity, improved reliability, NIwtOOtll_m 1
28、1_,107t21401_ and reduced weight while simultaneously reducing noiselevels.- Theobjectiveof thisprogramistodefine,bycontrolled- testingand actualnoisemeasurements,the effectofchanges in the Profile, Face, and Modified Contact- ratiosand the gear tooth form,separatelyand incombination, for spur and h
29、elical gears, on the noiselevels produced by otherwise identical spur and helical_ gears.In order to accomplish the objective defined above, aprogram has been defined to design appropriate gears,/ 0 /rn fabricate a sufficient number of test specimens, andconduct the testing required./ /AF Thespecifi
30、cgearconfigurationstobe testedareshownI L I , I , 1,1 I , I , I, I, , in Table 7. While a wide range of specimens is shown,1 _ 4 6 8 10 _1 40 _ 100 _lltll_ they will all be configured as nearly alike as practical,Gmrlifl, ychls within the limitations imposed by manufacturingU_t.g0at_tal _ _ _ _ _ If
31、finl. considerations and the test stand.Figure 18 - Surface DurabiliW_ Std & HCR-NIF These test gears are all compatible with the NASALewis Noise Test Rig, Figure 20, which will be used forall testing in this program.GEARNOISE DYNAMICI7. Parallel Axis Gear Noise Study MEASUREM|NTI P_tML_IC ruol_ OFG
32、EARDESIGNVARIAIII,.I_The problem of gear noise in helicopter transmissions _ma _n_n_-_r5hpMAXIMUMINPUT$PEED-dI,II00Wis ever present. The main exciting forces which produce u,xuuumotrrPtnSPEm-l,mthis noise are the meshing forces of the gear teeth in H-, xthe transmission. While this is certainly anov
33、ersimplification, since many factors influence Figure 20 - NASA Gear Noise Test Rigtransmission noise aside from the gear mesh forces, thesimple fact remains that if the basic exciting forces arereduced and no amplifying factors are presenP, theoverall noise level of the system will be reduced.z The
34、 contact ratio may be (not quite correctly) thought of as1 Resonances in the system, for example are likely to control the average number of teeth sharing load as the gear goes throughthe noise level to such an extent that the mesh forces would have mesh.to be zero, an .impossible situation, if nois
35、e level is to be affected!- 13 -design, build, and test a set of spur gears which utilizesurface modified titanium as the gear material.Table 7. Proposed Gear Noise Test Matrix “-._/_._* LIGHT WEIGHT ACCESSORRY GEARS* IONGUARD FOR WEAR RESISTANCEContactl_tim _EQUA_SURFACBDUR_n.aTYTest Tooth Type1 vr
36、m_RLOWPOWERProfile Face Mod Form LOWCOEmcm_roFmcnosBaseline 1.25 0.00 1.25 Involute SSpurHCR 2.15 0.00 2.15 Involute S Figure 21 - Surface Modified Titanium GearsINVBaseline 1.25 1.25 1.77 Involute HHelicalThe test program will be aimed at investigating theDouble 1.25 1.25 1.77 Involute HHelical ove
37、rall performance and noise characteristics of surfacemodified Accessory gears, particularly their relativeHCR 1.25 1.75 2.15 Involute H scoring and surface durability capacities as compared toINV a set of conventional steel gears at the same reductionHCR 2.15 2.25 3.11 Involute H ratio and center di
38、stance.INVTwo sets of spur gears will be designed to operate onNIF 1.25 0.00 1.25 Non SBaseline Involute the 6 inch center distance Boeing Helicopters GearResearch Test Rig in the overhung configuration. OneNIF 2.15 0.00 2.15 Non S set of gears will be designed for durability testing whileHCR Involu
39、te the secondset willbe designedfor scoringtesting.TheNOTE: tS= Spur, H = Helical durability test gears are a 1.67:1 ratio set while thescoring test gears are a 1:1 ratio set. This being thecase, the pinion and gear used in the durability testingare different while the pinion and gear used in the8.
40、Surface Modified Titanium Accessory Spur Gearsscoring testing are identical.Accessory gears in many helicopter applications, Five sets of each type of gear will be required. Sinceespecially for high power aircraft, are sized more bygeometric requirements than by load capacity. In the pinion and gear
41、 used in the durability testing aredifferent, five durability pinions and five durabilitygeneral, the pitch diameters of such accessory gears are gears will be required. Conversely, since the scoring testdetermined by the restraints imposed by the overall pinion and gear are identical, ten identical
42、 scoring gearsdesign of the gear box thus as the basic gear box gets test gears are required. The gears will be manufacturedlarger, the accessory gears are often designed with verysmall face/diameter ratios and are thus heavier than from Ti-6A1-4V Titanium Alloy in accordance with therequired to tra
43、nsmit the power required by the contractors normal practice so that they are fullyindividual accessories. Since there are practical limits representative of actual aircraft gears however the gearon how small the face width can be on a large diameter tooth profiles will be surface modified by two can
44、didateprocesses in an effort to avoid the galling problemsgear, such gears are often weight inefficient. One way which have thus far limited the application of Titaniumof reducing the weight of these gears would be to usea material which has a lower unit weight than the steel gears in power systems.
45、typicallyused. A complete inspection data history (lead, profile,Titanium is one such material, however, it has not spacing, runout, and finish)will be compiled for eachgained wide spread use because it performs poorly in gear set. Test slugs wiU be included in the heat treat lotdynamic, frictional
46、applications. Titanium gear teeth which contains these gears so that their metallurgicalsuffer from a rapid galling type failure, despite the best characteristics may be defined.lubrication. Recent advances in surface modificationprocesses, such as ion implantation, Figure 21, however Two types of t
47、esting will be accomplished during themay make it possible to treat the surface of titanium course of this program. They are aimed at investigatingthe most immediate concerns associated with the use ofgears to minimize the galling problem. If this approachis successful, a definite weight advantage c
48、an be titanium gears, that is surface load capacity and noisecharacteristics. The tests will all be accomplished atobtained. Thus the objective of this program is to Boeing Helicopters Gear Research Test Facility.- 14 -SUMMARY ACKNOWLEDGEMENTWork being conducted by Boeing Helicopters under the Suppo
49、rt of this work by the Lewis Research Center ofAdvanced Rotorcraft Transmission (ART)Technology the National Aeronautics and Space AdministrationIntegrated Demonstration program will provide and the U.S. Army under contract NAS 3-25421 issignificant advancements in the state-of-the-art for gratefully acknowledged. The interest shown by thefuture rotorcraft drive systems. This type of work has Project Manager, Mark J. Valco, is particularlybeen much needed to keep pace wi
