EASA accepts Federal Aviation Administration (FAA) Advisory Circular (AC) 20-66B ‘Propeller Vibration and Fatigue’, of 24 March 2011, as an acceptable means of compliance with CS 25.907 regarding the evaluation of vibratory stresses on propellers. The applicant should use in that evaluation fatigue and structural data that is obtained in accordance with the Certification Specifications and Acceptable Means of Compliance for Propellers (CS-P).
When investigating the actual vibration behaviour of each propeller, the applicant should include the operating conditions that correspond to descent with the power levers at flight idle position and with speeds around maximum operating limit speed (VMO). Experience has shown that such conditions may cause cyclic loads and vibrations that may exert excessive stress on some parts of the propeller. As aerodynamic loads differ depending on the position of the engine-propeller assembly on the aeroplane, the applicant should investigate the propellers’ vibration behaviour at all engine-propeller assembly positions.
[Amdt No: 25/27]