<div class="htmlview paragraph">Design, fabrication, and test of large high powered helicopter components in the U.S. Army Heavy Lift Helicopter Advanced Technology Component development program demonstrated the feasibility of efficient, large helicopter components and reduced the risk and cost of future heavy lift helicopter development. The components included a 92-foot diameter rotor system, an 18,000 horsepower drive system, a fly-by-wire flight control system, a 35 ton cargo handling system, and 8,000 horsepower turbo-shaft engines.</div> <div class="htmlview paragraph">Bench testing of the large, high power transmissions was not completed and is required to verify the adequacy of the design modifications resulting from the ATC technology development program. Moreover, current design methods were found to be inadequate for large flight weight gears, and new analytical design methods employing finite element techniques will be required for future large aircraft gear design applications.</div> <div class="htmlview paragraph">Extrapolation of the design and manufacturing technologies developed in the ATC program to larger but similar tandem rotor heavy lift configurations indicates that there are no formidable reasons why shaft driven helicopters cannot continue to grow in size. A study comparing shaft driven tandem helicopter configurations with hybrid airship configurations shows the helicopter to be competitive in the logging and containership off-loading applications for which the hybrid airship is being proposed.</div> <div class="htmlview paragraph">The present lack of any heavy lift helicopter development in the U.S. is noted and recommendations made to extend technology development.</div>