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538 

14 CFR Ch. I (1–1–24 Edition) 

§ 27.995 

which relative motion could exist must 
have provisions for flexibility. 

(c) Flexible hose must be approved. 
(d) Each flexible connection in fuel 

lines that may be under pressure or 
subjected to axial loading must use 
flexible hose assemblies. 

(e) No flexible hose that might be ad-

versely affected by high temperatures 
may be used where excessive tempera-
tures will exist during operation or 
after engine shutdown. 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–2, 33 FR 964, Jan. 26, 
1968] 

§ 27.995

Fuel valves. 

(a) There must be a positive, quick- 

acting valve to shut off fuel to each en-
gine individually. 

(b) The control for this valve must be 

within easy reach of appropriate crew-
members. 

(c) Where there is more than one 

source of fuel supply there must be 
means for independent feeding from 
each source. 

(d) No shutoff valve may be on the 

engine side of any firewall. 

§ 27.997

Fuel strainer or filter. 

There must be a fuel strainer or filter 

between the fuel tank outlet and the 
inlet of the first fuel system compo-
nent which is susceptible to fuel con-
tamination, including but not limited 
to the fuel metering device or an en-
gine positive displacement pump, 
whichever is nearer the fuel tank out-
let. This fuel strainer or filter must— 

(a) Be accessible for draining and 

cleaning and must incorporate a screen 
or element which is easily removable; 

(b) Have a sediment trap and drain 

except that it need not have a drain if 
the strainer or filter is easily remov-
able for drain purposes; 

(c) Be mounted so that its weight is 

not supported by the connecting lines 
or by the inlet or outlet connections of 
the strainer or filter itself, unless ade-
quate strength margins under all load-
ing conditions are provided in the lines 
and connections; and 

(d) Provide a means to remove from 

the fuel any contaminant which would 
jeopardize the flow of fuel through 
rotorcraft or engine fuel system com-
ponents required for proper rotorcraft 

fuel system or engine fuel system oper-
ation. 

[Amdt. 27–9, 39 FR 35461, Oct. 1, 1974, as 
amended by Amdt. 27–20, 49 FR 6849, Feb. 23, 
1984; Amdt. 27–23, 53 FR 34213, Sept. 2, 1988] 

§ 27.999

Fuel system drains. 

(a) There must be at least one acces-

sible drain at the lowest point in each 
fuel system to completely drain the 
system with the rotorcraft in any 
ground attitude to be expected in serv-
ice. 

(b) Each drain required by paragraph 

(a) of this section must— 

(1) Discharge clear of all parts of the 

rotorcraft; 

(2) Have manual or automatic means 

to assure positive closure in the off po-
sition; and 

(3) Have a drain valve— 
(i) That is readily accessible and 

which can be easily opened and closed; 
and 

(ii) That is either located or pro-

tected to prevent fuel spillage in the 
event of a landing with landing gear re-
tracted. 

[Doc. No. 574, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–11, 41 FR 55470, Dec. 20, 
1976; Amdt. 27–23, 53 FR 34213, Sept. 2, 1988] 

O

IL

S

YSTEM

 

§ 27.1011

Engines: General. 

(a) Each engine must have an inde-

pendent oil system that can supply it 
with an appropriate quantity of oil at a 
temperature not above that safe for 
continuous operation. 

(b) The usable oil capacity of each 

system may not be less than the prod-
uct of the endurance of the rotorcraft 
under critical operating conditions and 
the maximum oil consumption of the 
engine under the same conditions, plus 
a suitable margin to ensure adequate 
circulation and cooling. Instead of a ra-
tional analysis of endurance and con-
sumption, a usable oil capacity of one 
gallon for each 40 gallons of usable fuel 
may be used. 

(c) The oil cooling provisions for each 

engine must be able to maintain the oil 
inlet temperature to that engine at or 

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539 

Federal Aviation Administration, DOT 

§ 27.1021 

below the maximum established value. 
This must be shown by flight tests. 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–23, 53 FR 34213, Sept. 2, 
1988] 

§ 27.1013

Oil tanks. 

Each oil tank must be designed and 

installed so that— 

(a) It can withstand, without failure, 

each vibration, inertia, fluid, and 
structural load expected in operation; 

(b) [Reserved] 
(c) Where used with a reciprocating 

engine, it has an expansion space of not 
less than the greater of 10 percent of 
the tank capacity or 0.5 gallon, and 
where used with a turbine engine, it 
has an expansion space of not less than 
10 percent of the tank capacity. 

(d) It is impossible to fill the tank 

expansion space inadvertently with the 
rotorcraft in the normal ground atti-
tude; 

(e) Adequate venting is provided; and 
(f) There are means in the filler open-

ing to prevent oil overflow from enter-
ing the oil tank compartment. 

[Doc. No. 5074, 29 FR 15695, Nov. 24, 1964, as 
amended by Amdt. 27–9, 39 FR 35461, Oct. 1, 
1974] 

§ 27.1015

Oil tank tests. 

Each oil tank must be designed and 

installed so that it can withstand, 
without leakage, an internal pressure 
of 5 p.s.i., except that each pressurized 
oil tank used with a turbine engine 
must be designed and installed so that 
it can withstand, without leakage, an 
internal pressure of 5 p.s.i., plus the 
maximum operating pressure of the 
tank. 

[Amdt. 27–9, 39 FR 35462, Oct. 1, 1974] 

§ 27.1017

Oil lines and fittings. 

(a) Each oil line must be supported to 

prevent excessive vibration. 

(b) Each oil line connected to compo-

nents of the rotorcraft between which 
relative motion could exist must have 
provisions for flexibility. 

(c) Flexible hose must be approved. 
(d) Each oil line must have an inside 

diameter of not less than the inside di-
ameter of the engine inlet or outlet. No 
line may have splices between connec-
tions. 

§ 27.1019

Oil strainer or filter. 

(a) Each turbine engine installation 

must incorporate an oil strainer or fil-
ter through which all of the engine oil 
flows and which meets the following re-
quirements: 

(1) Each oil strainer or filter that has 

a bypass must be constructed and in-
stalled so that oil will flow at the nor-
mal rate through the rest of the sys-
tem with the strainer or filter com-
pletely blocked. 

(2) The oil strainer or filter must 

have the capacity (with respect to op-
erating limitations established for the 
engine) to ensure that engine oil sys-
tem functioning is not impaired when 
the oil is contaminated to a degree 
(with respect to particle size and den-
sity) that is greater than that estab-
lished for the engine under Part 33 of 
this chapter. 

(3) The oil strainer or filter, unless it 

is installed at an oil tank outlet, must 
incorporate a means to indicate con-
tamination before it reaches the capac-
ity established in accordance with 
paragraph (a)(2) of this section. 

(4) The bypass of a strainer or filter 

must be constructed and installed so 
that the release of collected contami-
nants is minimized by appropriate lo-
cation of the bypass to ensure that col-
lected contaminants are not in the by-
pass flow path. 

(5) An oil strainer or filter that has 

no bypass, except one that is installed 
at an oil tank outlet, must have a 
means to connect it to the warning 
system required in § 27.1305(r). 

(b) Each oil strainer or filter in a 

powerplant installation using recipro-
cating engines 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 ele-
ment completely blocked. 

[Amdt. 27–9, 39 FR 35462, Oct. 1, 1974, as 
amended by Amdt. 27–20, 49 FR 6849, Feb. 23, 
1984; Amdt. 27–23, 53 FR 34213, Sept. 2, 1988] 

§ 27.1021

Oil system drains. 

A drain (or drains) must be provided 

to allow safe drainage of the oil sys-
tem. Each drain must— 

(a) Be accessible; and 

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