123 

Federal Aviation Administration, DOT 

§ 121.333 

§ 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 
§ 121.337 may be included in deter-
mining the supply required for flight 
crewmembers on flight deck duty. 

(c) 

Use of oxygen masks by flight crew-

members. 

(1) When operating at flight 

altitudes above flight level 250, each 
flight crewmember on flight deck duty 
must be provided with an oxygen mask 
so designed that it can be rapidly 

VerDate Sep<11>2014 

08:20 May 17, 2019

Jkt 247048

PO 00000

Frm 00133

Fmt 8010

Sfmt 8010

Y:\SGML\247048.XXX

247048