Federal Aviation Administration, DOT

Section 33.75

thrust response must occur from a stabilized static condition using only the
bleed air and accessories loads necessary to run the engine. This takeoff
rating is specified by the applicant and
need not include thrust augmentation.
[Amdt. 33-1, 36 FR 5493, Mar. 24, 1971]

Section 33.74 Continued rotation.
If any of the engine main rotating
systems continue to rotate after the
engine is shutdown for any reason
while in flight, and if means to prevent
that continued rotation are not provided, then any continued rotation during the maximum period of flight, and
in the flight conditions expected to
occur with that engine inoperative,
may not result in any condition described in Section 33.75(g)(2)(i) through (vi) of
this part.

spaschal on DSK3GDR082PROD with CFR

[Amdt. 33-24, 72 FR 50867, Sept. 4, 2007]

Section 33.75 Safety analysis.
(a) (1) The applicant must analyze
the engine, including the control system, to assess the likely consequences
of all failures that can reasonably be
expected to occur. This analysis will
take into account, if applicable:
(i) Aircraft-level devices and procedures assumed to be associated with a
typical installation. Such assumptions
must be stated in the analysis.
(ii) Consequential secondary failures
and latent failures.
(iii) Multiple failures referred to in
paragraph (d) of this section or that result in the hazardous engine effects defined in paragraph (g)(2) of this section.
(2) The applicant must summarize
those failures that could result in
major engine effects or hazardous engine effects, as defined in paragraph (g)
of this section, and estimate the probability of occurrence of those effects.
Any engine part the failure of which
could reasonably result in a hazardous
engine effect must be clearly identified
in this summary.
(3) The applicant must show that
hazardous engine effects are predicted
to occur at a rate not in excess of that
defined as extremely remote (probability range of 10Section7 to 10Section9 per engine
flight hour). Since the estimated probability for individual failures may be
insufficiently precise to enable the ap-

plicant to assess the total rate for hazardous engine effects, compliance may
be shown by demonstrating that the
probability of a hazardous engine effect
arising from an individual failure can
be predicted to be not greater than 10Section8
per engine flight hour. In dealing with
probabilities of this low order of magnitude, absolute proof is not possible,
and compliance may be shown by reliance on engineering judgment and previous experience combined with sound
design and test philosophies.
(4) The applicant must show that
major engine effects are predicted to
occur at a rate not in excess of that defined as remote (probability range of
10Section5 to 10Section7 per engine flight hour).
(b) The FAA may require that any assumption as to the effects of failures
and likely combination of failures be
verified by test.
(c) The primary failure of certain single elements cannot be sensibly estimated in numerical terms. If the failure of such elements is likely to result
in hazardous engine effects, then compliance may be shown by reliance on
the prescribed integrity requirements
of SectionSection 33.15, 33.27, and 33.70 as applicable.
These instances must be stated in the
safety analysis.
(d) If reliance is placed on a safety
system to prevent a failure from progressing to hazardous engine effects,
the possibility of a safety system failure in combination with a basic engine
failure must be included in the analysis. Such a safety system may include
safety devices, instrumentation, early
warning devices, maintenance checks,
and other similar equipment or procedures. If items of a safety system are
outside the control of the engine manufacturer, the assumptions of the safety
analysis with respect to the reliability
of these parts must be clearly stated in
the analysis and identified in the installation instructions under Section 33.5 of
this part.
(e) If the safety analysis depends on
one or more of the following items,
those items must be identified in the
analysis and appropriately substantiated.
(1) Maintenance actions being carried
out at stated intervals. This includes
the verification of the serviceability of

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