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U.S. Army Air Mobility Research and Development Laboratory - Advanced Helicopter Structural Design Investigation - Vol. II - Design Application Study for Free Planet Transmissions

This document is volume 11 of the f iæA_æpeg on the results 
of a preliminary design exercise entitled Advanced Helicopter 
Structural Design Investigation; volume I is USAAFRDL Technical 
Report 75—56A, Investigation of Advanced Structural Component 
Design Concepts. The program was conducted by the Boeing 
Vertol Company for the Eustis Directorate, U. S. Army Air 
Mobility Research and Development laboratory, under contract 
DAAJ02-74-C-0066, from June 1974 through 1975. 
The work includes definition of a state—of—the—art aluminum 
baseline mediurn—range utility helicopter, redesign in advanced 
composites with advanced structural subsystems. and resizing 
of the advanced helicopter to perform che identical mission of 
the baseline hel icopter .

The analysis shown in Table I concludes that the free planet 
transmission as applied to the Medium—Range Utility Transport 
Helicopter (MVP) is equal or superior to a conventional trans— 
mission in all but cost and producibility. The Boeing Vertol 
advanced concept transmission showed significant advantage in 
this area, as well as in others. 
The assessment of the free planet transmission is drawn from 
design studies and analyses shown in this report as well as 
from limited testing of a 500—hp unit performed by Curtiss— 
Wright Corp. Features of the advanced concept transmission 
which are pertinent to the evaluation are outlined in this 
report . 
Further testing of existing free planet hardware is recommended . 
There is a potential for increased load—carrying capacity 
because of better load sharing between planets and for in— 
creased reliability because planet bearings are eliminated . 
These features should be evaluated before final conclus ions 
are drawn.