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:

1. (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.

2. (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. (1) The noise limit specified in § 36.501 of this part, or
   2. (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]