Helicopter Transmission Arrangements with Split-Torque Gear Trains,
TRANSMISSION RESEARCH INC CLEVELAND OH
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A need for progressive improvement in the performance of helicopter propulsion systems leads the transmission designer to examine alternative methods for transferring power from the engines to the rotors. Predominant in this effort is the problem of designing main rotor gearboxes having higher power to weight ratios with increased life and reliability. Development and uprating of components used in production gearboxes has, in the past, enabled transmission designers to match improvements elsewhere in the propulsion system. This short-term form of development is attractive since the design loads and problem areas are known in advance and the improved design can be incorporated into an existing transmission with minimum changes. But the uprating of conventional components results in progressively smaller gains and, as is historically demonstrable, contributes little to the problem of weight reduction for there is a natural tendency to trade-off any potential weight benefit with component life and reliability. As an alternative to component development, this work argues the case for improved drive-train configurations. In particular, the use of torque-splitting gear trains is proposed as a practicable means of improving the effectiveness of helicopter main gearboxes the work thus makes use of and extends concepts presented earlier in references 1 and 2. The potential for major weight reduction exists, but since significant changes to the propulsion configuration may be required, the development of such gear trains is necessarily longterm. No advance in technology level is required.