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328 

14 CFR Ch. I (1–1–18 Edition) 

§ 25.1123 

that are outside the engine and auxil-
iary power unit compartments. 

(d) No exhaust gases may discharge 

so as to cause a fire hazard with re-
spect to any flammable fluid vent or 
drain. 

(e) No exhaust gases may discharge 

where they will cause a glare seriously 
affecting pilot vision at night. 

(f) Each exhaust system component 

must be ventilated to prevent points of 
excessively high temperature. 

(g) Each exhaust shroud must be ven-

tilated or insulated to avoid, during 
normal operation, a temperature high 
enough to ignite any flammable fluids 
or vapors external to the shroud. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–40, 42 FR 15043, Mar. 17, 
1977] 

§ 25.1123

Exhaust piping. 

For powerplant and auxiliary power 

unit installations, the following apply: 

(a) Exhaust piping must be heat and 

corrosion resistant, and must have pro-
visions to prevent failure due to expan-
sion by operating temperatures. 

(b) Piping must be supported to with-

stand any vibration and inertia loads 
to which it would be subjected in oper-
ation; and 

(c) Piping connected to components 

between which relative motion could 
exist must have means for flexibility. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–40, 42 FR 15044, Mar. 17, 
1977] 

§ 25.1125

Exhaust heat exchangers. 

For reciprocating engine powered 

airplanes, the following apply: 

(a) Each exhaust heat exchanger 

must be constructed and installed to 
withstand each vibration, inertia, and 
other load to which it would be sub-
jected in operation. In addition— 

(1) Each exchanger must be suitable 

for continued operation at high tem-
peratures and resistant to corrosion 
from exhaust gases; 

(2) There must be means for the in-

spection of the critical parts of each 
exchanger; 

(3) Each exchanger must have cooling 

provisions wherever it is subject to 
contact with exhaust gases; and 

(4) No exhaust heat exchanger or 

muff may have any stagnant areas or 

liquid traps that would increase the 
probability of ignition of flammable 
fluids or vapors that might be present 
in case of the failure or malfunction of 
components carrying flammable fluids. 

(b) If an exhaust heat exchanger is 

used for heating ventilating air— 

(1) There must be a secondary heat 

exchanger between the primary ex-
haust gas heat exchanger and the ven-
tilating air system; or 

(2) Other means must be used to pre-

clude the harmful contamination of the 
ventilating air. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–38, 41 FR 55467, Dec. 20, 
1976] 

§ 25.1127

Exhaust driven turbo-super-

chargers. 

(a) Each exhaust driven turbo-super-

charger must be approved or shown to 
be suitable for the particular applica-
tion. It must be installed and sup-
ported to ensure safe operation be-
tween normal inspections and over-
hauls. In addition, there must be provi-
sions for expansion and flexibility be-
tween exhaust conduits and the tur-
bine. 

(b) There must be provisions for lu-

bricating the turbine and for cooling 
turbine parts where temperatures are 
critical. 

(c) If the normal turbo-supercharger 

control system malfunctions, the tur-
bine speed may not exceed its max-
imum allowable value. Except for the 
waste gate operating components, the 
components provided for meeting this 
requirement must be independent of 
the normal turbo-supercharger con-
trols. 

P

OWERPLANT

C

ONTROLS AND

 

A

CCESSORIES

 

§ 25.1141

Powerplant controls: general. 

Each powerplant control must be lo-

cated, arranged, and designed under 
§§ 25.777 through 25.781 and marked 
under § 25.1555. In addition, it must 
meet the following requirements: 

(a) Each control must be located so 

that it cannot be inadvertently oper-
ated by persons entering, leaving, or 
moving normally in, the cockpit. 

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