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14 CFR Ch. I (1–1–24 Edition) 

§ 33.17 

(b) Conform to approved specifica-

tions (such as industry or military 
specifications) that ensure their having 
the strength and other properties as-
sumed in the design data. 

(Secs. 313(a), 601, and 603, 72 Stat. 759, 775, 49 
U.S.C. 1354(a), 1421, and 1423; sec. 6(c), 49 
U.S.C. 1655(c)) 

[Amdt. 33–8, 42 FR 15047, Mar. 17, 1977, as 
amended by Amdt. 33–10, 49 FR 6850, Feb. 23, 
1984] 

§ 33.17

Fire protection. 

(a) The design and construction of 

the engine and the materials used must 
minimize the probability of the occur-
rence and spread of fire during normal 
operation and failure conditions, and 
must minimize the effect of such a fire. 
In addition, the design and construc-
tion of turbine engines must minimize 
the probability of the occurrence of an 
internal fire that could result in struc-
tural failure or other hazardous effects. 

(b) Except as provided in paragraph 

(c) of this section, each external line, 
fitting, and other component, which 
contains or conveys flammable fluid 
during normal engine operation, must 
be fire resistant or fireproof, as deter-
mined by the Administrator. Compo-
nents must be shielded or located to 
safeguard against the ignition of leak-
ing flammable fluid. 

(c) A tank, which contains flammable 

fluids and any associated shut-off 
means and supports, which are part of 
and attached to the engine, must be 
fireproof either by construction or by 
protection unless damage by fire will 
not cause leakage or spillage of a haz-
ardous quantity of flammable fluid. 
For a reciprocating engine having an 
integral oil sump of less than 23.7 liters 
capacity, the oil sump need not be fire-
proof or enclosed by a fireproof shield. 

(d) An engine component designed, 

constructed, and installed to act as a 
firewall must be: 

(1) Fireproof; 
(2) Constructed so that no hazardous 

quantity of air, fluid or flame can pass 
around or through the firewall; and, 

(3) Protected against corrosion; 
(e) In addition to the requirements of 

paragraphs (a) and (b) of this section, 
engine control system components that 
are located in a designated fire zone 

must be fire resistant or fireproof, as 
determined by the Administrator. 

(f) Unintentional accumulation of 

hazardous quantities of flammable 
fluid within the engine must be pre-
vented by draining and venting. 

(g) Any components, modules, or 

equipment, which are susceptible to or 
are potential sources of static dis-
charges or electrical fault currents 
must be designed and constructed to be 
properly grounded to the engine ref-
erence, to minimize the risk of ignition 
in external areas where flammable 
fluids or vapors could be present. 

[Doc. No. FAA–2007–28503, 74 FR 37930, July 
30, 2009] 

§ 33.19

Durability. 

(a) Engine design and construction 

must minimize the development of an 
unsafe condition of the engine between 
overhaul periods. The design of the 
compressor and turbine rotor cases 
must provide for the containment of 
damage from rotor blade failure. En-
ergy levels and trajectories of frag-
ments resulting from rotor blade fail-
ure that lie outside the compressor and 
turbine rotor cases must be defined. 

(b) Each component of the propeller 

blade pitch control system which is a 
part of the engine type design must 
meet the requirements of §§ 35.21, 35.23, 
35.42 and 35.43 of this chapter. 

[Doc. No. 3025, 29 FR 7453, June 10, 1964, as 
amended by Amdt. 33–9, 45 FR 60181, Sept. 11, 
1980; Amdt. 33–10, 49 FR 6851, Feb. 23, 1984; 
Amdt. 33–28, 73 FR 63346, Oct. 24, 2008] 

§ 33.21

Engine cooling. 

Engine design and construction must 

provide the necessary cooling under 
conditions in which the airplane is ex-
pected to operate. 

§ 33.23

Engine mounting attachments 

and structure. 

(a) The maximum allowable limit 

and ultimate loads for engine mount-
ing attachments and related engine 
structure must be specified. 

(b) The engine mounting attach-

ments and related engine structure 
must be able to withstand— 

(1) The specified limit loads without 

permanent deformation; and 

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