spaschal on DSK3GDR082PROD with CFR

Section 33.28

14 CFR Ch. I (1-1-19 Edition)

or external to the engine. The overspeed resulting from any other single
failure must be considered when selecting the most limiting overspeed conditions applicable to each rotor. Overspeeds resulting from combinations of
failures must also be considered unless
the applicant can show that the probability of occurrence is not greater
than extremely remote (probability
range of 10Section7 to 10Section9 per engine flight
hour).
(d) In addition, the applicant must
demonstrate that each fan, compressor,
turbine, and turbosupercharger rotor
complies with paragraphs (d)(1) and
(d)(2) of this section for the maximum
overspeed achieved when subjected to
the conditions specified in paragraphs
(b)(3) and (b)(4) of this section. The applicant must use the approach in paragraph (a) of this section which specifies
the required test conditions.
(1) Rotor Growth must not cause the
engine to:
(i) Catch fire,
(ii)
Release
high-energy
debris
through the engine casing or result in
a hazardous failure of the engine casing,
(iii) Generate loads greater than
those ultimate loads specified in
Section 33.23(a), or
(iv) Lose the capability of being shut
down.
(2) Following an overspeed event and
after continued operation, the rotor
may not exhibit conditions such as
cracking or distortion which preclude
continued safe operation.
(e) The design and functioning of engine control systems, instruments, and
other methods not covered under Section 33.28
must ensure that the engine operating
limitations that affect turbine, compressor, fan, and turbosupercharger
rotor structural integrity will not be
exceeded in service.
(f) Failure of a shaft section may be
excluded from consideration in determining the highest overspeed that
would result from a complete loss of
load on a turbine rotor if the applicant:
(1) Identifies the shaft as an engine
life-limited-part and complies with
Section 33.70.
(2) Uses material and design features
that are well understood and that can

be analyzed by well-established and
validated stress analysis techniques.
(3) Determines, based on an assessment of the environment surrounding
the shaft section, that environmental
influences are unlikely to cause a shaft
failure. This assessment must include
complexity of design, corrosion, wear,
vibration, fire, contact with adjacent
components or structure, overheating,
and secondary effects from other failures or combination of failures.
(4) Identifies and declares, in accordance with Section 33.5, any assumptions regarding the engine installation in making the assessment described above in
paragraph (f)(3) of this section.
(5) Assesses, and considers as appropriate, experience with shaft sections
of similar design.
(6) Does not exclude the entire shaft.
(g) If analysis is used to meet the
overspeed requirements, then the analytical tool must be validated to prior
overspeed test results of a similar
rotor. The tool must be validated for
each material. The rotor being certified must not exceed the boundaries
of the rotors being used to validate the
analytical tool in terms of geometric
shape, operating stress, and temperature. Validation includes the ability to
accurately predict rotor dimensional
growth and the burst speed. The predictions must also show that the rotor
being certified does not have lower
burst and growth margins than rotors
used to validate the tool.
[Doc. No. FAA-2010-0398, Amdt. 33-31, 76 FR
42023, July 18, 2011]

Section 33.28

Engine control systems.

(a) Applicability. These requirements
are applicable to any system or device
that is part of engine type design, that
controls, limits, or monitors engine operation, and is necessary for the continued airworthiness of the engine.
(b) Validation - (1) Functional aspects.
The applicant must substantiate by
tests, analysis, or a combination thereof, that the engine control system performs the intended functions in a manner which:
(i) Enables selected values of relevant control parameters to be maintained and the engine kept within the

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