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Federal Aviation Administration, DOT 

§ 33.75 

thrust response must occur from a sta-
bilized static condition using only the 
bleed air and accessories loads nec-
essary 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] 

§ 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 pro-
vided, then any continued rotation dur-
ing the maximum period of flight, and 
in the flight conditions expected to 
occur with that engine inoperative, 
may not result in any condition de-
scribed in § 33.75(g)(2)(i) through (vi) of 
this part. 

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

§ 33.75

Safety analysis. 

(a) (1) The applicant must analyze 

the engine, including the control sys-
tem, 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 proce-

dures 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 re-
sult in the hazardous engine effects de-
fined in paragraph (g)(2) of this section. 

(2) The applicant must summarize 

those failures that could result in 
major engine effects or hazardous en-
gine effects, as defined in paragraph (g) 
of this section, and estimate the prob-
ability 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 (prob-
ability range of 10



to 10



per engine 

flight hour). Since the estimated prob-
ability for individual failures may be 
insufficiently precise to enable the ap-

plicant to assess the total rate for haz-
ardous 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 10




per engine flight hour. In dealing with 
probabilities of this low order of mag-
nitude, absolute proof is not possible, 
and compliance may be shown by reli-
ance on engineering judgment and pre-
vious 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 de-
fined as remote (probability range of 



to 10



per engine flight hour). 

(b) The FAA may require that any as-

sumption as to the effects of failures 
and likely combination of failures be 
verified by test. 

(c) The primary failure of certain sin-

gle elements cannot be sensibly esti-
mated in numerical terms. If the fail-
ure of such elements is likely to result 
in hazardous engine effects, then com-
pliance may be shown by reliance on 
the prescribed integrity requirements 
of §§ 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 pro-
gressing to hazardous engine effects, 
the possibility of a safety system fail-
ure in combination with a basic engine 
failure must be included in the anal-
ysis. Such a safety system may include 
safety devices, instrumentation, early 
warning devices, maintenance checks, 
and other similar equipment or proce-
dures. If items of a safety system are 
outside the control of the engine manu-
facturer, 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 in-
stallation instructions under § 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 substan-

(1) Maintenance actions being carried 

out at stated intervals. This includes 
the verification of the serviceability of 

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