Identification of random loads impinging on the RAH-66 Comanche Helicopter empennage using spectral analysis
By: Patrick H. Mason
Publisher: Naval Postgraduate School; Available from National Technical Information Service
Published: 1998
Place of publication: Monterey, Calif; Springfield, Va
Language: eng
Number of pages: 146
Description: The Army RAH-66 ComancheHelicopter is currently undergoing developmental flight testing. Theempennage of the aircraft isexperiencing buffeting where the horizontal and vertical tail vibrate at resonant frequencies.   These high buffet loads are manifested in higher than anticipated fitting loads, particularly on the tail, and     vibrations in the crew stations and at the nose cone where the targeting sensors are located. Significant effort has been devoted to identifying the sources of excitation and the nature of the structural response. This thesis      determines the location andmagnitude of empennage vibratory airloads. Because the nature of the excitation is a random function, spectral analysis is used. To obtain the loads, a three step process was utilized. First, from      aircraft differential pressure transducers and accelerometers, the spectral content of theresponse and excitation was determined. Then, using aNASTRAN model modified to replicate the flight test aircraft, frequency response functions were determined between selected points on the aircraft's tail and the accelerometers.  Finally, using this information, a solution was obtained for the vibratory airloads. Having provided information on the nature of the driving forces, structural modifications can be made that move the natural frequencies away from thefrequencies of the applied airloads.
Notes: Thesis advisor(s):  E. Roberts Wood, Donald A. Danielson, Joshua H. Gordis.

"June 1998."

Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, June 1998.

Includes bibliographical references (p. 143-144).

"Approved for public release, distribution unlimited"--Cover.

Also available online.

Mode of access:  World Wide Web.

System requirements: Adobe Acrobat reader.

US Army (USA) author.

dk/dk cc:9116 09/30/98.