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Federal Aviation Administration, DOT 

§ 33.71 

§ 33.70

Engine life-limited parts. 

By a procedure approved by the FAA, 

operating limitations must be estab-
lished which specify the maximum al-
lowable number of flight cycles for 
each engine life-limited part. Engine 
life-limited parts are rotor and major 
static structural parts whose primary 
failure is likely to result in a haz-
ardous engine effect. Typically, engine 
life-limited parts include, but are not 
limited to disks, spacers, hubs, shafts, 
high-pressure casings, and non-redun-
dant mount components. For the pur-
poses of this section, a hazardous en-
gine effect is any of the conditions list-
ed in § 33.75 of this part. The applicant 
will establish the integrity of each en-
gine life-limited part by: 

(a) An engineering plan that contains 

the steps required to ensure each en-
gine life-limited part is withdrawn 
from service at an approved life before 
hazardous engine effects can occur. 
These steps include validated analysis, 
test, or service experience which en-
sures that the combination of loads, 
material properties, environmental in-
fluences and operating conditions, in-
cluding the effects of other engine 
parts influencing these parameters, are 
sufficiently well known and predictable 
so that the operating limitations can 
be established and maintained for each 
engine life-limited part. Applicants 
must perform appropriate damage tol-
erance assessments to address the po-
tential for failure from material, man-
ufacturing, and service induced anoma-
lies within the approved life of the 
part. Applicants must publish a list of 
the life-limited engine parts and the 
approved life for each part in the Air-
worthiness Limitations Section of the 
Instructions for Continued Airworthi-
ness as required by § 33.4 of this part. 

(b) A manufacturing plan that identi-

fies the specific manufacturing con-
straints necessary to consistently 
produce each engine life-limited part 
with the attributes required by the en-
gineering plan. 

(c) A service management plan that 

defines in-service processes for mainte-
nance and the limitations to repair for 
each engine life-limited part that will 
maintain attributes consistent with 
those required by the engineering plan. 
These processes and limitations will 

become part of the Instructions for 
Continued Airworthiness. 

[Amdt. 33–22, 72 FR 50860, Sept. 4, 2007] 

§ 33.71

Lubrication system. 

(a) 

General. 

Each lubrication system 

must function properly in the flight at-
titudes and atmospheric conditions in 
which an aircraft is expected to oper-
ate. 

(b) 

Oil strainer or filter. 

There must be 

an oil strainer or filter through which 
all of the engine oil flows. In addition: 

(1) Each strainer or filter required by 

this paragraph that has a bypass must 
be constructed and installed so that oil 
will flow at the normal rate through 
the rest of the system with the strainer 
or filter element completely blocked. 

(2) The type and degree of filtering 

necessary for protection of the engine 
oil system against foreign particles in 
the oil must be specified. The applicant 
must demonstrate that foreign par-
ticles passing through the specified fil-
tering means do not impair engine oil 
system functioning. 

(3) Each strainer or filter required by 

this paragraph must have the capacity 
(with respect to operating limitations 
established for the engine) to ensure 
that engine oil system functioning is 
not impaired with the oil contaminated 
to a degree (with respect to particle 
size and density) that is greater than 
that established for the engine in para-
graph (b)(2) of this section. 

(4) For each strainer or filter re-

quired by this paragraph, except the 
strainer or filter at the oil tank outlet, 
there must be means to indicate con-
tamination before it reaches the capac-
ity established in accordance with 
paragraph (b)(3) of this section. 

(5) Any filter bypass must be de-

signed and constructed so that the re-
lease of collected contaminants is 
minimized by appropriate location of 
the bypass to ensure that the collected 
contaminants are not in the bypass 
flow path. 

(6) Each strainer or filter required by 

this paragraph that has no bypass, ex-
cept the strainer or filter at an oil 
tank outlet or for a scavenge pump, 
must have provisions for connection 
with a warning means to warn the pilot 
of the occurance of contamination of 

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