323 

Federal Aviation Administration, DOT 

§ 25.1013 

minutes cruise at a speed for maximum 
range. However, if there is an auxiliary 
control independent of the main jetti-
soning control, the system may be de-
signed to jettison the remaining fuel 
by means of the auxiliary jettisoning 
control. 

(g) The fuel jettisoning valve must be 

designed to allow flight personnel to 
close the valve during any part of the 
jettisoning operation. 

(h) Unless it is shown that using any 

means (including flaps, slots, and slats) 
for changing the airflow across or 
around the wings does not adversely af-
fect fuel jettisoning, there must be a 
placard, adjacent to the jettisoning 
control, to warn flight crewmembers 
against jettisoning fuel while the 
means that change the airflow are 
being used. 

(i) The fuel jettisoning system must 

be designed so that any reasonably 
probable single malfunction in the sys-
tem will not result in a hazardous con-
dition due to unsymmetrical jetti-
soning of, or inability to jettison, fuel. 

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as 
amended by Amdt. 25–18, 33 FR 12226, Aug. 30, 
1968; Amdt. 25–57, 49 FR 6848, Feb. 23, 1984; 
Amdt. 25–108, 67 FR 70827, Nov. 26, 2002] 

O

IL

S

YSTEM

 

§ 25.1011

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 may not 

be less than the product of the endur-
ance of the airplane under critical op-
erating conditions and the approved 
maximum allowable oil consumption of 
the engine under the same conditions, 
plus a suitable margin to ensure sys-
tem circulation. Instead of a rational 
analysis of airplane range for the pur-
pose of computing oil requirements for 
reciprocating engine powered air-
planes, the following fuel/oil ratios 
may be used: 

(1) For airplanes without a reserve 

oil or oil transfer system, a fuel/oil 
ratio of 30:1 by volume. 

(2) For airplanes with either a re-

serve oil or oil transfer system, a fuel/ 
oil ratio of 40:1 by volume. 

(c) Fuel/oil ratios higher than those 

prescribed in paragraphs (b)(1) and (2) 
of this section may be used if substan-
tiated by data on actual engine oil con-
sumption. 

§ 25.1013

Oil tanks. 

(a) 

Installation. 

Each oil tank instal-

lation must meet the requirements of 
§ 25.967. 

(b) 

Expansion space. 

Oil tank expan-

sion space must be provided as follows: 

(1) Each oil tank used with a recipro-

cating engine must have an expansion 
space of not less than the greater of 10 
percent of the tank capacity or 0.5 gal-
lon, and each oil tank used with a tur-
bine engine must have an expansion 
space of not less than 10 percent of the 
tank capacity. 

(2) Each reserve oil tank not directly 

connected to any engine may have an 
expansion space of not less than two 
percent of the tank capacity. 

(3) It must be impossible to fill the 

expansion space inadvertently with the 
airplane in the normal ground attitude. 

(c) 

Filler connection. 

Each recessed oil 

tank filler connection that can retain 
any appreciable quantity of oil must 
have a drain that discharges clear of 
each part of the airplane. In addition, 
each oil tank filler cap must provide an 
oil-tight seal. 

(d) 

Vent. 

Oil tanks must be vented as 

follows: 

(1) Each oil tank must be vented 

from the top part of the expansion 
space so that venting is effective under 
any normal flight condition. 

(2) Oil tank vents must be arranged 

so that condensed water vapor that 
might freeze and obstruct the line can-
not accumulate at any point. 

(e) 

Outlet. 

There must be means to 

prevent entrance into the tank itself, 
or into the tank outlet, of any object 
that might obstruct the flow of oil 
through the system. No oil tank outlet 
may be enclosed by any screen or guard 
that would reduce the flow of oil below 
a safe value at any operating tempera-
ture. There must be a shutoff valve at 
the outlet of each oil tank used with a 
turbine engine, unless the external por-
tion of the oil system (including the oil 
tank supports) is fireproof. 

(f) 

Flexible oil tank liners. 

Each flexi-

ble oil tank liner must be approved or 

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