646 

14 CFR Ch. I (1–1–24 Edition) 

§ 29.1101 

section if the heat rise utilized is that 
which will be available, automatically, 
for the applicable altitude and oper-
ation condition because of super-
charging. 

(Secs. 313(a), 601, and 603, 72 Stat. 752, 775, 49 
U.S.C. 1354(a), 1421, and 1423; sec. 6(c), 49 
U.S.C. 1655 (c)) 

[Amdt. 29–3, 33 FR 969, Jan. 26, 1968, as 
amended by Amdt. 29–12, 41 FR 55473, Dec. 20, 
1976; Amdt. 29–13, 42 FR 15046, Mar. 17, 1977; 
Amdt. 29–22, 49 FR 6850, Feb. 23, 1984; Amdt. 
29–26, 53 FR 34219, Sept. 2, 1988] 

§ 29.1101

Carburetor air preheater de-

sign. 

Each carburetor air preheater must 

be designed and constructed to— 

(a) Ensure ventilation of the pre-

heater when the engine is operated in 
cold air; 

(b) Allow inspection of the exhaust 

manifold parts that it surrounds; and 

(c) Allow inspection of critical parts 

of the preheater itself. 

§ 29.1103

Induction systems ducts and 

air duct systems. 

(a) Each induction system duct up-

stream of the first stage of the engine 
supercharger and of the auxiliary 
power unit compressor must have a 
drain to prevent the hazardous accu-
mulation of fuel and moisture in the 
ground attitude. No drain may dis-
charge where it might cause a fire haz-
ard. 

(b) Each duct must be strong enough 

to prevent induction system failure 
from normal backfire conditions. 

(c) Each duct connected to compo-

nents between which relative motion 
could exist must have means for flexi-
bility. 

(d) Each duct within any fire zone for 

which a fire-extinguishing system is re-
quired must be at least— 

(1) Fireproof, if it passes through any 

firewall; or 

(2) Fire resistant, for other ducts, ex-

cept that ducts for auxiliary power 
units must be fireproof within the aux-
iliary power unit fire zone. 

(e) Each auxiliary power unit induc-

tion system duct must be fireproof for 
a sufficient distance upstream of the 
auxiliary power unit compartment to 
prevent hot gas reverse flow from burn-
ing through auxiliary power unit ducts 

and entering any other compartment 
or area of the rotorcraft in which a 
hazard would be created resulting from 
the entry of hot gases. The materials 
used to form the remainder of the in-
duction system duct and plenum cham-
ber of the auxiliary power unit must be 
capable of resisting the maximum heat 
conditions likely to occur. 

(f) Each auxiliary power unit induc-

tion system duct must be constructed 
of materials that will not absorb or 
trap hazardous quantities of flammable 
fluids that could be ignited in the 
event of a surge or reverse flow condi-
tion. 

(Secs. 313(a), 601, 603, 604, Federal Aviation 
Act of 1958 (49 U.S.C. 1354(a), 1421, 1423, 1424), 
sec. 6(c), Dept. of Transportation Act (49 
U.S.C. 1655(c))) 

[Doc. No. 5084, 29 FR 16150, Dec. 3, 1964, as 
amended by Amdt. 29–17, 43 FR 50602, Oct. 30, 
1978] 

§ 29.1105

Induction system screens. 

If induction system screens are 

used— 

(a) Each screen must be upstream of 

the carburetor; 

(b) No screen may be in any part of 

the induction system that is the only 
passage through which air can reach 
the engine, unless it can be deiced by 
heated air; 

(c) No screen may be deiced by alco-

hol alone; and 

(d) It must be impossible for fuel to 

strike any screen. 

§ 29.1107

Inter-coolers and after-cool-

ers. 

Each inter-cooler and after-cooler 

must be able to withstand the vibra-
tion, inertia, and air pressure loads to 
which it would be subjected in oper-
ation. 

§ 29.1109

Carburetor air cooling. 

It must be shown under § 29.1043 that 

each installation using two-stage su-
perchargers has means to maintain the 
air temperature, at the carburetor 
inlet, at or below the maximum estab-
lished value. 

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