An ultra-safe, high ratio compound planetary transmission, forapplication as a helicopter main rotor drive, has been designedunder the sponsorship of the National Rotorcraft Technology Center-Rotorcraft Industry Technology Association (NRTC/RITA). It isanticipated that this new planetary transmission offersimprovements relative to the current state-of-the-art including,reduced weight, reduced transmitted noise and improved fail-safety.This paper discusses the analysis and design results for thesubject planetary transmission. Fabrication and testing of thetransmission will be conducted in subsequent phases of theproject.
Typically, the final stage in helicopter main rotor drivesconsists of one or two simple planetary stages which themselves arecomposed of a sun gear,multiple planet gears (typically between 3and 6) and an internal gear which is generally the fixed member ofthis epicyclic system. The main rotor transmission is the mostcritical and usually the heaviest assembly in the drive system forany rotary wing aircraft, be it a single or tandem rotor helicopteror a tilt rotor vehicle.
The new ultra-safe, high ratio planetary transmission designutilizes a compound planetary configurationwith a 17.5:1 reductionratiowhich would replace a conventional two stage simple planetarytransmission. The new design uses ultra-safe principles such assplit-torque paths and high combined contact ratio gearing. Doublehelical gears in the planet/ ring meshes balance axial tooth forcesso that axial bearing reactions are not required. The spur gearsun/planet meshes are staggered to achieve a compact spatialarrangement.
In order to provide major, simultaneous improvements in weight,noise, power density, and reliability, a paradigm shift must occurin the basic design of the gear system in this component. Thisprogram brings together a large number of individual gear systeminnovations which, taken together, are expected to yield a largeimprovement in noise and performance combined with improvedreliability and fail safety.
- Edition:
- 04
- Published:
- 10/01/2004
- Number of Pages:
- 12
- File Size:
- 1 file , 610 KB
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