Originally Posted by
Search&Rescue
§29.861 Fire protection of structure, controls, and other parts.
Each part of the structure, controls, and the rotor mechanism, and other parts essential to controlled landing and (for category A) flight that would be affected by powerplant fires must be isolated under § 29.1191, or must be—
(a) For category A rotorcraft, fire- proof; and
(b) For Category B rotorcraft, fire- proof or protected so that they can per- form their essential functions for at least 5 minutes under any foreseeable powerplant fire conditions.
[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as amended by Amdt. 27–26, 55 FR 8005, Mar. 6, 1990]
(And ”Fire proof” should be associated with a test flame temperature of 2000 degrees F for at least 15-minute duration...)
Very good. FWIW, those are the current regulation/guidance. At the time of the S-76 certification, (category B occurred in 1978, and category A followed in 1979), there was no quantified definition of “fireproof.” In 1993, the FAA published AC33-2B, which stated:
The FAR Part 1 definitions of “fire-resistant” and “fire proof” are very broad and are not quantified in terms of flame temperature and time of immersion. For purposes of engine certification, fire resistant should be associated with a test flame temperature of 2000 degrees F, for at least a 5-minute duration; fireproof should be associated with a test flame temperature of 2000 degrees F, for at least a 15-minute duration.