For propeller-driven small airplanes in the primary, normal, utility, acrobatic, transport, and restricted categories and for propeller-driven, commuter category airplanes for which an acoustical change approval is applied for under §21.93(b) of this chapter after January 1, 1975, the following apply:

(a) If the airplane was type certificated under this part prior to a change in type design, it may not subsequently exceed the noise limits specified in §36.501 of this part.

(b) If the airplane was not type certificated under this part prior to a change in type design, it may not exceed the higher of the two following values:

(1) The noise limit specified in §36.501 of this part, or

(2) The noise level created prior to the change in type design, measured and corrected as prescribed in §36.501 of this part.

[Amdt. 36-16, 53 FR 47400, Nov. 22, 1988; 53 FR 50157, Dec. 13, 1988; Amdt. 36-19, 57 FR 41369, Sept. 9, 1992]