ED Decision 2003/15/RM
Each part of the rotorcraft must be free from excessive vibration under each appropriate speed and power condition.
ED Decision 2023/001/R
This AMC supplements FAA AC 27-1B, § AC 27.251 and should be used in conjunction with that AC when demonstrating compliance with CS 27.251.
The applicant should investigate each individual installation of the rotorcraft for compliance with CS 27.251. The absence of coupling with the rotor vibration frequencies should be demonstrated by a combination of analysis, vibration and flight tests.
Qualitative and quantitative flight tests should be performed depending on the extent of the change. For any installation, the failure of which or its attachment would have a catastrophic consequence, a fatigue evaluation should be performed when the vibrations are likely to affect the fatigue strength.
[Amdt 27/10]