Sec. 23.933 - Reversing systems.
(a) For turbojet and turbofan
reversing systems. (1) Each system intended for ground operation only
must be designed so that, during any reversal in flight, the engine will
produce no more than flight idle thrust. In addition, it must be shown by
analysis or test, or both, that --
(i) Each operable reverser can be
restored to the forward thrust position; or
(ii) The airplane is capable of
continued safe flight and landing under any possible position of the
(2) Each system intended for in-flight
use must be designed so that no unsafe condition will result during normal
operation of the system, or from any failure, or likely combination of
failures, of the reversing system under any operating condition including
ground operation. Failure of structural elements need not be considered if
the probability of this type of failure is extremely remote.
(3) Each system must have a means to
prevent the engine from producing more than idle thrust when the reversing
system malfunctions; except that it may produce any greater thrust that is
shown to allow directional control to be maintained, with aerodynamic
means alone, under the most critical reversing condition expected in
(b) For propeller reversing systems.
(1) Each system must be designed so that no single failure, likely
combination of failures or malfunction of the system will result in
unwanted reverse thrust under any operating condition. Failure of
structural elements need not be considered if the probability of this type
of failure is extremely remote.
(2) Compliance with paragraph (b)(1) of
this section must be shown by failure analysis, or testing, or both, for
propeller systems that allow the propeller blades to move from the flight
low-pitch position to a position that is substantially less than the
normal flight, low-pitch position. The analysis may include or be
supported by the analysis made to show compliance with §35.21 for the type
certification of the propeller and associated installation components.
Credit will be given for pertinent analysis and testing completed by the
engine and propeller manufacturers.
[Doc. No. 26344, 58 FR 18971, Apr. 9, 1993, as
amended by Amdt. 23-51, 61 FR 5136, Feb. 9, 1996]