Current design methodologies as applied to rotorcrafttransmissions yield reliable, safe, and weight effective systems.In general, weight and performance (i.e., torque transmission perpound of transmission weight) are the primary active variableswhile safety is addressed by monitoring the design so thatconventional criteria, such as calculated stresses, are kept withinestablished allowable levels. This procedure is almost universallyapplied and has been quite successful both at Boeing Defense &Space Group, Rotorcraft and at other major rotary wing firms.
It is possible, however, to raise these already good safetycharacteristics to ultra safe levels through the use of certaindesign approaches. UltraSafe gear system design will require abasic change in the overall philosophy of design as it is practicedtoday. This change must be revolutionary rather thanevolutionary.
In order to develop an UltraSafe transmission a basic paradigmshift will be required. In addition to addressing the designprocess from the typical “prevent a failure from occurring” pointof view, it will also be necessary to view the system from thepoint of view of “what happens when a failure occurs”.
The current State-of-Technology is such that the concept ofsafety is addressed during the design process in an indirect ratherthan direct manner. Major design goals are achieved by designingcomponents so that they meet the applicable allowable stress levelsin order to insure that the possibility of a failure occurring isreduced to a finite but acceptable level.
Since it is not possible to design, manufacture, build or useany machine with absolute 100% certainty that a failure, at somepoint, for some cause, in some manner, will not occur, the designprocess must address the problem of failure in a more directmanner. The current State-of-Technology does not adequately addressthis facet of the design process.
The objective of this program is the development of a set ofdesign guidelines and specific design techniques which will make adramatic improvement in the failsafe operation of helicopter andtiltrotor aircraft transmissions while not significantly affectingeither performance or weight characteristics. This paper presentsthe initial results of an ongoing program aimed at achieving thisobjective.
- Edition:
- 97
- Published:
- 11/01/1997
- Number of Pages:
- 24
- File Size:
- 0 files
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