27.659—Mass balance.
(a)
The rotors and blades must be mass balanced as necessary to—
(1)
Prevent excessive vibration; and
(2)
Prevent flutter at any speed up to the maximum forward speed.
(b)
The structural integrity of the mass balance installation must be substantiated.
Code of Federal Regulations
[Amdt. 27-2, 33 FR 963, Jan. 26, 1968]