99 

Federal Aviation Administration, DOT 

§ 121.183 

(c) This section does not apply to 

large nontransport category airplanes 
operated under § 121.173(c). 

[Doc. No. 6258, 29 FR 19198, Dec. 31, 1964, as 
amended by Amdt. 121–251, 60 FR 65928, Dec. 
20, 1995] 

§ 121.181 Airplanes: Reciprocating en-

gine-powered: En route limitations: 

One engine inoperative. 

(a) Except as provided in paragraph 

(b) of this section, no person operating 
a reciprocating engine powered air-
plane may take off that airplane at a 
weight, allowing for normal consump-
tion of fuel and oil, that does not allow 
a rate of climb (in feet per minute), 
with one engine inoperative, of at least 

(0.079–0.106/N) V

so

2 

(where 

N 

is the number of engines in-

stalled and 

V

So

is expressed in knots) at 

an altitude of at least 1,000 feet above 
the highest ground or obstruction 
within 10 miles of each side of the in-
tended track. However, for the pur-
poses of this paragraph the rate of 
climb for airplanes certificated under 
part 4a of the Civil Air Regulations is 
0.026 V

so

2. 

(b) In place of the requirements of 

paragraph (a) of this section, a person 
may, under an approved procedure, op-
erate a reciprocating engine powered 
airplane, at an all-engines-operating 
altitude that allows the airplane to 
continue, after an engine failure, to an 
alternate airport where a landing can 
be made in accordance with § 121.187, al-
lowing for normal consumption of fuel 
and oil. After the assumed failure, the 
flight path must clear the ground and 
any obstruction within five miles on 
each side of the intended track by at 
least 2,000 feet. 

(c) If an approved procedure under 

paragraph (b) of this section is used, 
the certificate holder shall comply 
with the following: 

(1) The rate of climb (as prescribed in 

the Airplane Flight Manual for the ap-
propriate weight and altitude) used in 
calculating the airplane’s flight path 
shall be diminished by an amount, in 
feet per minute, equal to 

(0.079–0.106/N) V

so

2 

(when 

N 

is the number of engines in-

stalled and 

V

So

is expressed in knots) 

for airplanes certificated under part 25 
of this chapter and by 0.026 V

so

2 for air-

planes certificated under part 4a of the 
Civil Air Regulations. 

(2) The all-engines-operating altitude 

shall be sufficient so that in the event 
the critical engine becomes inoperative 
at any point along the route, the flight 
will be able to proceed to a predeter-
mined alternate airport by use of this 
procedure. In determining the takeoff 
weight, the airplane is assumed to pass 
over the critical obstruction following 
engine failure at a point no closer to 
the critical obstruction than the near-
est approved radio navigational fix, un-
less the Administrator approves a pro-
cedure established on a different basis 
upon finding that adequate operational 
safeguards exist. 

(3) The airplane must meet the provi-

sions of paragraph (a) of this section at 
1,000 feet above the airport used as an 
alternate in this procedure. 

(4) The procedure must include an ap-

proved method of accounting for winds 
and temperatures that would otherwise 
adversely affect the flight path. 

(5) In complying with this procedure 

fuel jettisoning is allowed if the certifi-
cate holder shows that it has an ade-
quate training program, that proper in-
structions are given to the flight crew, 
and all other precautions are taken to 
insure a safe procedure. 

(6) The certificate holder shall speci-

fy in the dispatch or flight release an 
alternate airport that meets the re-
quirements of § 121.625. 

(d) This section does not apply to 

large nontransport category airplanes 
operated under § 121.173(c). 

[Doc. No. 6258, 29 FR 19198, Dec. 31, 1964; 30 
FR 130, Jan. 7, 1965, as amended by Amdt. 
121–251, 60 FR 65928, Dec. 20, 1995] 

§ 121.183 Part 25 airplanes with four 

or more engines: Reciprocating en-

gine powered: En route limitations: 

Two engines inoperative. 

(a) No person may operate an air-

plane certificated under part 25 and 
having four or more engines unless— 

(1) There is no place along the in-

tended track that is more than 90 min-
utes (with all engines operating at 
cruising power) from an airport that 
meets the requirements of § 121.187; or