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359 

Federal Aviation Administration, DOT 

§ 25.1439 

(5) Be designed to use any suitable 

hydraulic fluid specified by the air-
plane manufacturer, which must be 
identified by appropriate markings as 
required by § 25.1541. 

(c) 

Tests. Tests must be conducted on 

the hydraulic system(s), and/or sub-
system(s) and elements, except that 
analysis may be used in place of or to 
supplement testing, where the analysis 
is shown to be reliable and appropriate. 
All internal and external influences 
must be taken into account to an ex-
tent necessary to evaluate their ef-
fects, and to assure reliable system and 
element functioning and integration. 
Failure or unacceptable deficiency of 
an element or system must be cor-
rected and be sufficiently retested, 
where necessary. 

(1) The system(s), subsystem(s), or 

element(s) must be subjected to per-
formance, fatigue, and endurance tests 
representative of airplane ground and 
flight operations. 

(2) The complete system must be 

tested to determine proper functional 
performance and relation to the other 
systems, including simulation of rel-
evant failure conditions, and to sup-
port or validate element design. 

(3) The complete hydraulic system(s) 

must be functionally tested on the air-
plane in normal operation over the 
range of motion of all associated user 
systems. The test must be conducted at 
the system relief pressure or 1.25 times 
the DOP if a system pressure relief de-
vice is not part of the system design. 
Clearances between hydraulic system 
elements and other systems or struc-
tural elements must remain adequate 
and there must be no detrimental ef-
fects. 

[Doc. No. 28617, 66 FR 27402, May 16, 2001] 

§ 25.1438

Pressurization and pneu-

matic systems. 

(a) Pressurization system elements 

must be burst pressure tested to 2.0 
times, and proof pressure tested to 1.5 
times, the maximum normal operating 
pressure. 

(b) Pneumatic system elements must 

be burst pressure tested to 3.0 times, 
and proof pressure tested to 1.5 times, 
the maximum normal operating pres-
sure. 

(c) An analysis, or a combination of 

analysis and test, may be substituted 
for any test required by paragraph (a) 
or (b) of this section if the Adminis-
trator finds it equivalent to the re-
quired test. 

[Amdt. 25–41, 42 FR 36971, July 18, 1977] 

§ 25.1439

Protective breathing equip-

ment. 

(a) Fixed (stationary, or built in) pro-

tective breathing equipment must be 
installed for the use of the flightcrew, 
and at least one portable protective 
breathing equipment shall be located 
at or near the flight deck for use by a 
flight crewmember. In addition, port-
able protective breathing equipment 
must be installed for the use of appro-
priate crewmembers for fighting fires 
in compartments accessible in flight 
other than the flight deck. This in-
cludes isolated compartments and 
upper and lower lobe galleys, in which 
crewmember occupancy is permitted 
during flight. Equipment must be in-
stalled for the maximum number of 
crewmembers expected to be in the 
area during any operation. 

(b) For protective breathing equip-

ment required by paragraph (a) of this 
section or by the applicable Operating 
Regulations: 

(1) The equipment must be designed 

to protect the appropriate crewmember 
from smoke, carbon dioxide, and other 
harmful gases while on flight deck 
duty or while combating fires. 

(2) The equipment must include— 
(i) Masks covering the eyes, nose and 

mouth, or 

(ii) Masks covering the nose and 

mouth, plus accessory equipment to 
cover the eyes. 

(3) Equipment, including portable 

equipment, must allow communication 
with other crewmembers while in use. 
Equipment available at flightcrew as-
signed duty stations must also enable 
the flightcrew to use radio equipment. 

(4) The part of the equipment pro-

tecting the eyes shall not cause any ap-
preciable adverse effect on vision and 
must allow corrective glasses to be 
worn. 

(5) The equipment must supply pro-

tective oxygen of 15 minutes duration 
per crewmember at a pressure altitude 
of 8,000 feet with a respiratory minute 

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360 

14 CFR Ch. I (1–1–24 Edition) 

§ 25.1441 

volume of 30 liters per minute BTPD. 
The equipment and system must be de-
signed to prevent any inward leakage 
to the inside of the device and prevent 
any outward leakage causing signifi-
cant increase in the oxygen content of 
the local ambient atmosphere. If a de-
mand oxygen system is used, a supply 
of 300 liters of free oxygen at 70 

°

F. and 

760 mm. Hg. pressure is considered to 
be of 15-minute duration at the pre-
scribed altitude and minute volume. If 
a continuous flow open circuit protec-
tive breathing system is used, a flow 
rate of 60 liters per minute at 8,000 feet 
(45 liters per minute at sea level) and a 
supply of 600 liters of free oxygen at 70 

°

F. and 760 mm. Hg. pressure is consid-

ered to be of 15-minute duration at the 
prescribed altitude and minute volume. 
Continuous flow systems must not in-
crease the ambient oxygen content of 
the local atmosphere above that of de-
mand systems. BTPD refers to body 
temperature conditions (that is, 37 

°

C., 

at ambient pressure, dry). 

(6) The equipment must meet the re-

quirements of § 25.1441. 

[Doc. No. FAA–2002–13859, 69 FR 40528, July 2, 
2004] 

§ 25.1441

Oxygen equipment and sup-

ply. 

(a) If certification with supplemental 

oxygen equipment is requested, the 
equipment must meet the requirements 
of this section and §§ 25.1443 through 
25.1453. 

(b) The oxygen system must be free 

from hazards in itself, in its method of 
operation, and in its effect upon other 
components. 

(c) There must be a means to allow 

the crew to readily determine, during 
flight, the quantity of oxygen available 
in each source of supply. 

(d) The oxygen flow rate and the oxy-

gen equipment for airplanes for which 
certification for operation above 40,000 
feet is requested must be approved. 

§ 25.1443

Minimum mass flow of sup-

plemental oxygen. 

(a) If continuous flow equipment is 

installed for use by flight crew-
members, the minimum mass flow of 
supplemental oxygen required for each 
crewmember may not be less than the 
flow required to maintain, during in-

spiration, a mean tracheal oxygen par-
tial pressure of 149 mm. Hg. when 
breathing 15 liters per minute, BTPS, 
and with a maximum tidal volume of 
700 cc. with a constant time interval 
between respirations. 

(b) If demand equipment is installed 

for use by flight crewmembers, the 
minimum mass flow of supplemental 
oxygen required for each crewmember 
may not be less than the flow required 
to maintain, during inspiration, a 
mean tracheal oxygen partial pressure 
of 122 mm. Hg., up to and including a 
cabin pressure altitude of 35,000 feet, 
and 95 percent oxygen between cabin 
pressure altitudes of 35,000 and 40,000 
feet, when breathing 20 liters per 
minute BTPS. In addition, there must 
be means to allow the crew to use undi-
luted oxygen at their discretion. 

(c) For passengers and cabin attend-

ants, the minimum mass flow of sup-
plemental oxygen required for each 
person at various cabin pressure alti-
tudes may not be less than the flow re-
quired to maintain, during inspiration 
and while using the oxygen equipment 
(including masks) provided, the fol-
lowing mean tracheal oxygen partial 
pressures: 

(1) At cabin pressure altitudes above 

10,000 feet up to and including 18,500 
feet, a mean tracheal oxygen partial 
pressure of 100 mm. Hg. when breathing 
15 liters per minute, BTPS, and with a 
tidal volume of 700 cc. with a constant 
time interval between respirations. 

(2) At cabin pressure altitudes above 

18,500 feet up to and including 40,000 
feet, a mean tracheal oxygen partial 
pressure of 83.8 mm. Hg. when breath-
ing 30 liters per minute, BTPS, and 
with a tidal volume of 1,100 cc. with a 
constant time interval between res-
pirations. 

(d) If first-aid oxygen equipment is 

installed, the minimum mass flow of 
oxygen to each user may not be less 
than four liters per minute, STPD. 
However, there may be a means to de-
crease this flow to not less than two li-
ters per minute, STPD, at any cabin al-
titude. The quantity of oxygen re-
quired is based upon an average flow 
rate of three liters per minute per per-
son for whom first-aid oxygen is re-
quired. 

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