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. 

222 

14 CFR Ch. I (1–1–24 Edition) 

§ 121.580 

(d) 

Approach. 

No person may use an 

autopilot at an altitude lower than 50 
feet below the DA(H) or MDA for the 
instrument procedure being flown, ex-
cept as follows— 

(1) For autopilots with an AFM speci-

fied altitude loss for approach oper-
ations— 

(i) An altitude no lower than twice 

the specified altitude loss if higher 
than 50 feet below the MDA or DA(H); 

(ii) An altitude no lower than 50 feet 

higher than the altitude loss specified 
in the AFM, when the following condi-
tions are met— 

(A) Reported weather conditions are 

less than the basic VFR weather condi-
tions in § 91.155 of this chapter; 

(B) Suitable visual references speci-

fied in § 91.175 of this chapter have been 
established on the instrument ap-
proach procedure; and 

(C) The autopilot is coupled and re-

ceiving both lateral and vertical path 
references; 

(iii) An altitude no lower than the 

higher of the altitude loss specified in 
the AFM or 50 feet above the TDZE, 
when the following conditions are 
met— 

(A) Reported weather conditions are 

equal to or better than the basic VFR 
weather conditions in § 91.155 of this 
chapter; and 

(B) The autopilot is coupled and re-

ceiving both lateral and vertical path 
references; or 

(iv) A greater altitude specified by 

the Administrator. 

(2) For autopilots with AFM specified 

approach altitude limitations, the 
greater of— 

(i) The minimum use altitude speci-

fied for the coupled approach mode se-
lected; 

(ii) 50 feet; or 
(iii) An altitude specified by Admin-

istrator. 

(3) For autopilots with an AFM speci-

fied negligible or zero altitude loss for 
an autopilot approach mode malfunc-
tion, the greater of— 

(i) 50 feet; or 
(ii) An altitude specified by Adminis-

trator. 

(4) If executing an autopilot coupled 

go-around or missed approach using a 
certificated and functioning autopilot 

in accordance with paragraph (e) in 
this section. 

(e) 

Go-Around/Missed Approach. 

No 

person may engage an autopilot during 
a go-around or missed approach below 
the minimum engagement altitude 
specified for takeoff and initial climb 
in paragraph (b) in this section. An 
autopilot minimum use altitude does 
not apply to a go-around/missed ap-
proach initiated with an engaged auto-
pilot. Performing a go-around or 
missed approach with an engaged auto-
pilot must not adversely affect safe ob-
stacle clearance. 

(f) 

Landing. 

Notwithstanding para-

graph (d) of this section, autopilot min-
imum use altitudes do not apply to 
autopilot operations when an approved 
automatic landing system mode is 
being used for landing. Automatic 
landing systems must be authorized in 
an operations specification issued to 
the operator. 

[Doc. No. FAA–2012–1059, 79 FR 6086, Feb. 3, 
2014] 

§ 121.580 Prohibition on interference 

with crewmembers. 

No person may assault, threaten, in-

timidate, or interfere with a crew-
member in the performance of the 
crewmember’s duties aboard an air-
craft being operated under this part. 

[Doc. No. FAA–1998–4954, 64 FR 1080, Jan. 7, 
1999] 

§ 121.581 Observer’s seat: En route in-

spections. 

(a) Except as provided in paragraph 

(c) of this section, each certificate 
holder shall make available a seat on 
the flight deck of each airplane, used 
by it in air commerce, for occupancy 
by the Administrator while conducting 
en route inspections. The location and 
equipment of the seat, with respect to 
its suitability for use in conducting en 
route inspections, is determined by the 
Administrator. 

(b) In each airplane that has more 

than one observer’s seat, in addition to 
the seats required for the crew com-
plement for which the airplane was cer-
tificated, the forward observer’s seat or 
the observer’s seat selected by the Ad-
ministrator must be made available 
when complying with paragraph (a) of 
this section.