271 

Federal Aviation Administration, DOT 

§ 23.909 

under normal daylight ground condi-
tions. 

(g) If the engine exhaust gases are 

discharged into the pusher propeller 
disc, it must be shown by tests, or 
analysis supported by tests, that the 
propeller is capable of continuous safe 
operation. 

(h) All engine cowling, access doors, 

and other removable items must be de-
signed to ensure that they will not sep-
arate from the airplane and contact 
the pusher propeller. 

[Doc. No. 4080, 29 FR 17955, Dec. 18, 1964, as 
amended by Amdt. 23–26, 45 FR 60171, Sept. 
11, 1980; Amdt. 23–29, 49 FR 6847, Feb. 23, 1984; 
Amdt. 23–43, 58 FR 18970, Apr. 9, 1993; Amdt. 
23–59, 73 FR 63345, Oct. 24, 2008] 

§ 23.907

Propeller vibration and fa-

tigue. 

This section does not apply to fixed- 

pitch wood propellers of conventional 
design. 

(a) The applicant must determine the 

magnitude of the propeller vibration 
stresses or loads, including any stress 
peaks and resonant conditions, 
throughout the operational envelope of 
the airplane by either: 

(1) Measurement of stresses or loads 

through direct testing or analysis 
based on direct testing of the propeller 
on the airplane and engine installation 
for which approval is sought; or 

(2) Comparison of the propeller to 

similar propellers installed on similar 
airplane installations for which these 
measurements have been made. 

(b) The applicant must demonstrate 

by tests, analysis based on tests, or 
previous experience on similar designs 
that the propeller does not experience 
harmful effects of flutter throughout 
the operational envelope of the air-
plane. 

(c) The applicant must perform an 

evaluation of the propeller to show 
that failure due to fatigue will be 
avoided throughout the operational life 
of the propeller using the fatigue and 
structural data obtained in accordance 
with part 35 of this chapter and the vi-
bration data obtained from compliance 
with paragraph (a) of this section. For 
the purpose of this paragraph, the pro-
peller includes the hub, blades, blade 
retention component and any other 
propeller component whose failure due 

to fatigue could be catastrophic to the 
airplane. This evaluation must include: 

(1) The intended loading spectra in-

cluding all reasonably foreseeable pro-
peller vibration and cyclic load pat-
terns, identified emergency conditions, 
allowable overspeeds and overtorques, 
and the effects of temperatures and hu-
midity expected in service. 

(2) The effects of airplane and pro-

peller operating and airworthiness lim-
itations. 

[Amdt. 23–59, 73 FR 63345, Oct. 24, 2008] 

§ 23.909

Turbocharger systems. 

(a) Each turbocharger must be ap-

proved under the engine type certifi-
cate or it must be shown that the tur-
bocharger system, while in its normal 
engine installation and operating in 
the engine environment— 

(1) Can withstand, without defect, an 

endurance test of 150 hours that meets 
the applicable requirements of § 33.49 of 
this subchapter; and 

(2) Will have no adverse effect upon 

the engine. 

(b) Control system malfunctions, vi-

brations, and abnormal speeds and 
temperatures expected in service may 
not damage the turbocharger com-
pressor or turbine. 

(c) Each turbocharger case must be 

able to contain fragments of a com-
pressor or turbine that fails at the 
highest speed that is obtainable with 
normal speed control devices inoper-
ative. 

(d) Each intercooler installation, 

where provided, must comply with the 
following— 

(1) The mounting provisions of the 

intercooler must be designed to with-
stand the loads imposed on the system; 

(2) It must be shown that, under the 

installed vibration environment, the 
intercooler will not fail in a manner al-
lowing portions of the intercooler to be 
ingested by the engine; and 

(3) Airflow through the intercooler 

must not discharge directly on any air-
plane component (e.g., windshield) un-
less such discharge is shown to cause 
no hazard to the airplane under all op-
erating conditions. 

(e) Engine power, cooling character-

istics, operating limits, and procedures 

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