Critical to the design of rotorcraft is the placement of the major airframe natural frequencies for sufficient separation from the frequencies of the excitations generated by the rotating components. Often, however, an existing platform which has good frequency characteristics is required to undergo significant modifications which adversely impact the airframe natural frequency placements. A design approach is necessary which provides for re-tuning the modified airframe to return its dynamics characteristics to the quality of the original design. For this purpose, preliminary design studies have been performed for utilizing resilient connections for airframe components to favorably adjust airframe natural frequencies. Specifically, the need arose for frequency re-tuning of the McDonell Douglas AH-64 helicopter due to planned airframe modifications. A preliminary design was developed for mounting the empennage to the tailboom using elastomeric cartridges to tune the frequency of the fundamental airframe mode away from the main rotor rotational frequency (1P). The stiffness of the elastomeric elements was tailored to provide the desired frequency separation. Consideration was given to the effect of the resilient mounts on other major airframe modes, and the design tailored to minimize that effect.
Using resilient connections for helicopter airframe modal frequency placement
Die Verwendung von elastischen Verbindungen zur modalen Frequenzfestlegung von Hubschrauberzellen
Forum, Annual Forum, American Helicopter Society, 50 ; 2 ; 1323-1335
1994
13 Seiten, 11 Bilder, 2 Tabellen, 2 Quellen
Conference paper
English
Using Resilient Connections for Helicopter Airframe Modal Frequency Placement
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