221 

Federal Aviation Administration, DOT 

§ 121.579 

with regard to compliance with this 
section. 

[Doc. No. 26142, 57 FR 42674, Sept. 15, 1992] 

§ 121.578 Cabin ozone concentration. 

(a) For the purpose of this section, 

the following definitions apply: 

(1) 

Flight segment 

means scheduled 

nonstop flight time between two air-
ports. 

(2) 

Sea level equivalent 

refers to condi-

tions of 25 

°

C and 760 millimeters of 

mercury pressure. 

(b) Except as provided in paragraphs 

(d) and (e) of this section, no certifi-
cate holder may operate an airplane 
above the following flight levels unless 
it is successfully demonstrated to the 
Administrator that the concentration 
of ozone inside the cabin will not ex-
ceed— 

(1) For flight above flight level 320, 

0.25 parts per million by volume, sea 
level equivalent, at any time above 
that flight level; and 

(2) For flight above flight level 270, 

0.1 parts per million by volume, sea 
level equivalent, time-weighted aver-
age for each flight segment that ex-
ceeds 4 hours and includes flight above 
that flight level. (For this purpose, the 
amount of ozone below flight level 180 
is considered to be zero.) 

(c) Compliance with this section 

must be shown by analysis or tests, 
based on either airplane operational 
procedures and performance limita-
tions or the certificate holder’s oper-
ations. The analysis or tests must show 
either of the following: 

(1) Atmospheric ozone statistics indi-

cate, with a statistical confidence of at 
least 84%, that at the altitudes and lo-
cations at which the airplane will be 
operated cabin ozone concentrations 
will not exceed the limits prescribed by 
paragraph (b) of this section. 

(2) The airplane ventilation system 

including any ozone control equipment, 
will maintain cabin ozone concentra-
tions at or below the limits prescribed 
by paragraph (b) of this section. 

(d) A certificate holder may obtain 

an authorization to deviate from the 
requirements of paragraph (b) of this 
section, by an amendment to its oper-
ations specifications, if— 

(1) It shows that due to cir-

cumstances beyond its control or to 

unreasonable economic burden it can-
not comply for a specified period of 
time; and 

(2) It has submitted a plan acceptable 

to the Administrator to effect compli-
ance to the extent possible. 

(e) A certificate holder need not com-

ply with the requirements of paragraph 
(b) of this section for an aircraft— 

(1) When the only persons carried are 

flight crewmembers and persons listed 
in § 121.583; 

(2) If the aircraft is scheduled for re-

tirement before January 1, 1985; or 

(3) If the aircraft is scheduled for re- 

engining under the provisions of sub-
part E of part 91, until it is re-engined. 

[Doc. No. 121–154, 45 FR 3883, Jan. 21, 1980. Re-
designated by Amdt. 121–162, 45 FR 46739, 
July 10, 1980, and amended by Amdt. 121–181, 
47 FR 58489, Dec. 30, 1982; Amdt. 121–251, 60 
FR 65935, Dec. 20, 1995] 

§ 121.579 Minimum altitudes for use of 

autopilot. 

(a) 

Definitions. 

For purpose of this 

section— 

(1) Altitudes for takeoff/initial climb 

and go-around/missed approach are de-
fined as above the airport elevation. 

(2) Altitudes for enroute operations 

are defined as above terrain elevation. 

(3) Altitudes for approach are defined 

as above the touchdown zone elevation 
(TDZE), unless the altitude is specifi-
cally in reference to DA (H) or MDA, in 
which case the altitude is defined by 
reference to the DA(H) or MDA itself. 

(b) 

Takeoff and initial climb. 

No person 

may use an autopilot for takeoff or ini-
tial climb below the higher of 500 feet 
or an altitude that is no lower than 
twice the altitude loss specified in the 
Airplane Flight Manual (AFM), except 
as follows— 

(1) At a minimum engagement alti-

tude specified in the AFM; or 

(2) At an altitude specified by the Ad-

ministrator, whichever is greater. 

(c) 

Enroute. 

No person may use an 

autopilot enroute, including climb and 
descent, below the following— 

(1) 500 feet; 
(2) At an altitude that is no lower 

than twice the altitude loss specified in 
the AFM for an autopilot malfunction 
in cruise conditions; or 

(3) At an altitude specified by the Ad-

ministrator, whichever is greater.