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737 

Federal Aviation Administration, DOT 

§ 33.96 

§ 33.94

Blade containment and rotor 

unbalance tests. 

(a) Except as provided in paragraph 

(b) of this section, it must be dem-
onstrated by engine tests that the en-
gine is capable of containing damage 
without catching fire and without fail-
ure of its mounting attachments when 
operated for at least 15 seconds, unless 
the resulting engine damage induces a 
self shutdown, after each of the fol-
lowing events: 

(1) Failure of the most critical com-

pressor or fan blade while operating at 
maximum permissible r.p.m. The blade 
failure must occur at the outermost re-
tention groove or, for integrally-bladed 
rotor discs, at least 80 percent of the 
blade must fail. 

(2) Failure of the most critical tur-

bine blade while operating at max-
imum permissible r.p.m. The blade fail-
ure must occur at the outermost reten-
tion groove or, for integrally-bladed 
rotor discs, at least 80 percent of the 
blade must fail. The most critical tur-
bine blade must be determined by con-
sidering turbine blade weight and the 
strength of the adjacent turbine case 
at case temperatures and pressures as-
sociated with operation at maximum 
permissible r.p.m. 

(b) Analysis based on rig testing, 

component testing, or service experi-
ence may be substitute for one of the 
engine tests prescribed in paragraphs 
(a)(1) and (a)(2) of this section if— 

(1) That test, of the two prescribed, 

produces the least rotor unbalance; and 

(2) The analysis is shown to be equiv-

alent to the test. 

(Secs. 313(a), 601, and 603, Federal Aviation 
Act of 1958 (49 U.S.C. 1354(a), 1421, and 1423); 
and 49 U.S.C. 106(g) Revised, Pub. L. 97–449, 
Jan. 12, 1983) 

[Amdt. 33–10, 49 FR 6854, Feb. 23, 1984] 

§ 33.95

Engine-propeller systems tests. 

If the engine is designed to operate 

with a propeller, the following tests 
must be made with a representative 
propeller installed by either including 
the tests in the endurance run or oth-
erwise performing them in a manner 
acceptable to the Administrator: 

(a) Feathering operation: 25 cycles. 

(b) Negative torque and thrust sys-

tem operation: 25 cycles from rated 
maximum continuous power. 

(c) Automatic decoupler operation: 25 

cycles from rated maximum contin-
uous power (if repeated decoupling and 
recoupling in service is the intended 
function of the device). 

(d) Reverse thrust operation: 175 cy-

cles from the flight-idle position to full 
reverse and 25 cycles at rated max-
imum continuous power from full for-
ward to full reverse thrust. At the end 
of each cycle the propeller must be op-
erated in reverse pitch for a period of 
30 seconds at the maximum rotational 
speed and power specified by the appli-
cant for reverse pitch operation. 

[Doc. No. 3025, 29 FR 7453, June 10, 1964, as 
amended by Amdt. 33–3, 32 FR 3737, Mar. 4, 
1967] 

§ 33.96

Engine tests in auxiliary power 

unit (APU) mode. 

If the engine is designed with a pro-

peller brake which will allow the pro-
peller to be brought to a stop while the 
gas generator portion of the engine re-
mains in operation, and remain stopped 
during operation of the engine as an 
auxiliary power unit (‘‘APU mode’’), in 
addition to the requirements of § 33.87, 
the applicant must conduct the fol-
lowing tests: 

(a) Ground locking: A total of 45 

hours with the propeller brake engaged 
in a manner which clearly dem-
onstrates its ability to function with-
out adverse effects on the complete en-
gine while the engine is operating in 
the APU mode under the maximum 
conditions of engine speed, torque, 
temperature, air bleed, and power ex-
traction as specified by the applicant. 

(b) Dynamic braking: A total of 400 

application-release cycles of brake en-
gagements must be made in a manner 
which clearly demonstrates its ability 
to function without adverse effects on 
the complete engine under the max-
imum conditions of engine accelera-
tion/deceleration rate, speed, torque, 
and temperature as specified by the ap-
plicant. The propeller must be stopped 
prior to brake release. 

(c) One hundred engine starts and 

stops with the propeller brake engaged. 

(d) The tests required by paragraphs 

(a), (b), and (c) of this section must be 

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