134 

14 CFR Ch. I (1–1–24 Edition) 

§ 121.329 

(2) For flights at cabin pressure alti-

tudes above 14,000 feet up to and in-
cluding 15,000 feet, enough oxygen for 
that part of the flight at those alti-
tudes for 30 percent of the passengers. 

(3) For flights at cabin pressure alti-

tudes above 15,000 feet, enough oxygen 
for each passenger carried during the 
entire flight at those altitudes. 

(d) For the purposes of this subpart 

cabin pressure altitude 

means the pres-

sure altitude corresponding with the 
pressure in the cabin of the airplane, 
and 

flight altitude 

means the altitude 

above sea level at which the airplane is 
operated. For airplanes without pres-
surized cabins, ‘‘cabin pressure alti-
tude’’ and ‘‘flight altitude’’ mean the 
same thing. 

§ 121.329 Supplemental oxygen for sus-

tenance: Turbine engine powered 

airplanes. 

(a) 

General. 

When operating a turbine 

engine powered airplane, each certifi-
cate holder shall equip the airplane 
with sustaining oxygen and dispensing 
equipment for use as set forth in this 
section: 

(1) The amount of oxygen provided 

must be at least the quantity nec-
essary to comply with paragraphs (b) 
and (c) of this section. 

(2) The amount of sustaining and 

first-aid oxygen required for a par-
ticular operation to comply with the 
rules in this part is determined on the 
basis of cabin pressure altitudes and 
flight duration, consistent with the op-
erating procedures established for each 
operation and route. 

(3) The requirements for airplanes 

with pressurized cabins are determined 
on the basis of cabin pressure altitude 
and the assumption that a cabin pres-
surization failure will occur at the alti-
tude or point of flight that is most 
critical from the standpoint of oxygen 
need, and that after the failure the air-
plane will descend in accordance with 
the emergency procedures specified in 
the Airplane Flight Manual, without 
exceeding its operating limitations, to 
a flight altitude that will allow suc-
cessful termination of the flight. 

(4) Following the failure, the cabin 

pressure altitude is considered to be 
the same as the flight altitude unless it 
is shown that no probable failure of the 

cabin or pressurization equipment will 
result in a cabin pressure altitude 
equal to the flight altitude. Under 
those circumstances, the maximum 
cabin pressure altitude attained may 
be used as a basis for certification or 
determination of oxygen supply, or 
both. 

(b) 

Crewmembers. 

Each certificate 

holder shall provide a supply of oxygen 
for crewmembers in accordance with 
the following: 

(1) At cabin pressure altitudes above 

10,000 feet, up to and including 12,000 
feet, oxygen must be provided for and 
used by each member of the flight crew 
on flight deck duty and must be pro-
vided for other crewmembers for that 
part of the flight at those altitudes 
that is of more than 30 minutes dura-
tion. 

(2) At cabin pressure altitudes above 

12,000 feet, oxygen must be provided 
for, and used by, each member of the 
flight crew on flight deck duty, and 
must be provided for other crew-
members during the entire flight at 
those altitudes. 

(3) When a flight crewmember is re-

quired to use oxygen, he must use it 
continuously except when necessary to 
remove the oxygen mask or other dis-
penser in connection with his regular 
duties. Standby crewmembers who are 
on call or are definitely going to have 
flight deck duty before completing the 
flight must be provided with an 
amount of supplemental oxygen equal 
to that provided for crewmembers on 
duty other than on flight duty. If a 
standby crewmember is not on call and 
will not be on flight deck duty during 
the remainder of the flight, he is con-
sidered to be a passenger for the pur-
poses of supplemental oxygen require-
ments. 

(c) 

Passengers. 

Each certificate holder 

shall provide a supply of oxygen for 
passengers in accordance with the fol-
lowing: 

(1) For flights at cabin pressure alti-

tudes above 10,000 feet, up to and in-
cluding 14,000 feet, enough oxygen for 
that part of the flight at those alti-
tudes that is of more than 30 minutes 
duration, for 10 percent of the pas-
sengers. 

135 

Federal Aviation Administration, DOT 

§ 121.333 

(2) For flights at cabin pressure alti-

tudes above 14,000 feet, up to and in-
cluding 15,000 feet, enough oxygen for 
that part of the flight at those alti-
tudes for 30 percent of the passengers. 

(3) For flights at cabin pressure alti-

tudes above 15,000 feet, enough oxygen 
for each passenger carried during the 
entire flight at those altitudes. 

§ 121.331 Supplemental oxygen re-

quirements for pressurized cabin 
airplanes: Reciprocating engine 
powered airplanes. 

(a) When operating a reciprocating 

engine powered airplane pressurized 
cabin, each certificate holder shall 
equip the airplane to comply with 
paragraphs (b) through (d) of this sec-
tion in the event of cabin pressuriza-
tion failure. 

(b) 

For crewmembers. 

When operating 

at flight altitudes above 10,000 feet, the 
certificate holder shall provide enough 
oxygen for each crewmember for the 
entire flight at those altitudes and not 
less than a two-hour supply for each 
flight crewmember on flight deck duty. 
The required two hours supply is that 
quantity of oxygen necessary for a con-
stant rate of descent from the air-
plane’s maximum certificated oper-
ating altitude to 10,000 feet in ten min-
utes and followed by 110 minutes at 
10,000 feet. The oxygen required by 
§ 121.337 may be considered in deter-
mining the supplemental breathing 
supply required for flight crewmembers 
on flight deck duty in the event of 
cabin pressurization failure. 

(c) 

For passengers. 

When operating at 

flight altitudes above 8,000 feet, the 
certificate holder shall provide oxygen 
as follows: 

(1) When an airplane is not flown at 

a flight altitude above flight level 250, 
enough oxygen for 30 minutes for 10 
percent of the passengers, if at any 
point along the route to be flown the 
airplane can safely descend to a flight 
altitude of 14,000 feet or less within 
four minutes. 

(2) If the airplane cannot descend to 

a flight altitude of 14,000 feet or less 
within four minutes, the following sup-
ply of oxygen must be provided: 

(i) For that part of the flight that is 

more than four minutes duration at 

flight altitudes above 15,000 feet, the 
supply required by § 121.327(c)(3). 

(ii) For that part of the flight at 

flight altitudes above 14,000 feet, up to 
and including 15,000 feet, the supply re-
quired by § 121.327(c)(2). 

(iii) For flight at flight altitudes 

above 8,000 feet up to and including 
14,000 feet, enough oxygen for 30 min-
utes for 10 percent of the passengers. 

(3) When an airplane is flown at a 

flight altitude above flight level 250, 
enough oxygen for 30 minutes for 10 
percent of the passengers for the entire 
flight (including emergency descent) 
above 8,000 feet, up to and including 
14,000 feet, and to comply with 
§ 121.327(c) (2) and (3) for flight above 
14,000 feet. 

(d) For the purposes of this section it 

is assumed that the cabin pressuriza-
tion failure occurs at a time during 
flight that is critical from the stand-
point of oxygen need and that after the 
failure the airplane will descend, with-
out exceeding its normal operating 
limitations, to flight altitudes allow-
ing safe flight with respect to terrain 
clearance. 

[Doc. No. 6258, 29 FR 19205, Dec. 31, 1964, as 
amended by Amdt. 121–132, 41 FR 55475, Dec. 
20, 1976] 

§ 121.333 Supplemental oxygen for 

emergency descent and for first aid; 

turbine engine powered airplanes 

with pressurized cabins. 

(a) 

General. 

When operating a turbine 

engine powered airplane with a pres-
surized cabin, the certificate holder 
shall furnish oxygen and dispensing 
equipment to comply with paragraphs 
(b) through (e) of this section in the 
event of cabin pressurization failure. 

(b) 

Crewmembers. 

When operating at 

flight altitudes above 10,000 feet, the 
certificate holder shall supply enough 
oxygen to comply with § 121.329, but not 
less than a two-hour supply for each 
flight crewmember on flight deck duty. 
The required two hours supply is that 
quantity of oxygen necessary for a con-
stant rate of descent from the air-
plane’s maximum certificated oper-
ating altitude to 10,000 feet in ten min-
utes and followed by 110 minutes at 
10,000 feet. The oxygen required in the 
event of cabin pressurization failure by