100 

14 CFR Ch. I (1–1–24 Edition) 

§ 121.185 

(2) It is operated at a weight allowing 

the airplane, with the two critical en-
gines inoperative, to climb at 0.013 V

so

2 

feet per minute (that is, the number of 
feet per minute is obtained by multi-
plying the number of knots squared by 
0.013) at an altitude of 1,000 feet above 
the highest ground or obstruction 
within 10 miles on each side of the in-
tended track, or at an altitude of 5,000 
feet, whichever is higher. 

(b) For the purposes of paragraph 

(a)(2) of this section, it is assumed 
that— 

(1) The two engines fail at the point 

that is most critical with respect to 
the takeoff weight: 

(2) Consumption of fuel and oil is nor-

mal with all engines operating up to 
the point where the two engines fail 
and with two engines operating beyond 
that point; 

(3) Where the engines are assumed to 

fail at an altitude above the prescribed 
minimum altitude, compliance with 
the prescribed rate of climb at the pre-
scribed minimum altitude need not be 
shown during the descent from the 
cruising altitude to the prescribed min-
imum altitude, if those requirements 
can be met once the prescribed min-
imum altitude is reached, and assum-
ing descent to be along a net flight 
path and the rate of descent to be 0.013 
V

so

2 greater than the rate in the ap-

proved performance data; and 

(4) If fuel jettisoning is provided, the 

airplane’s weight at the point where 
the two engines fail is considered to be 
not less than that which would include 
enough fuel to proceed to an airport 
meeting the requirements of § 121.187 
and to arrive at an altitude of at least 
1,000 feet directly over that airport. 

[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] 

§ 121.185 Airplanes: Reciprocating en-

gine-powered: Landing limitations: 

Destination airport. 

(a) Except as provided in paragraph 

(b) of this section no person operating 
a reciprocating engine powered air-
plane may take off that airplane, un-
less its weight on arrival, allowing for 
normal consumption of fuel and oil in 
flight, would allow a full stop landing 
at the intended destination within 60 

percent of the effective length of each 
runway described below from a point 50 
feet directly above the intersection of 
the obstruction clearance plane and 
the runway. For the purposes of deter-
mining the allowable landing weight at 
the destination airport the following is 
assumed: 

(1) The airplane is landed on the most 

favorable runway and in the most fa-
vorable direction in still air. 

(2) The airplane is landed on the most 

suitable runway considering the prob-
able wind velocity and direction (fore-
cast for the expected time of arrival), 
the ground handling characteristics of 
the type of airplane, and other condi-
tions such as landing aids and terrain, 
and allowing for the effect of the land-
ing path and roll of not more than 50 
percent of the headwind component or 
not less than 150 percent of the tail-
wind component. 

(b) An airplane that would be prohib-

ited from being taken off because it 
could not meet the requirements of 
paragraph (a)(2) of this section may be 
taken off if an alternate airport is 
specified that meets all of the require-
ments of this section except that the 
airplane can accomplish a full stop 
landing within 70 percent of the effec-
tive length of the runway. 

(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; 30 
FR 130, Jan. 7, 1965, as amended by Amdt. 
121–251, 60 FR 65928, Dec. 20, 1995] 

§ 121.187 Airplanes: Reciprocating en-

gine-powered: Landing limitations: 
Alternate airport. 

(a) No person may list an airport as 

an alternate airport in a dispatch or 
flight release unless the airplane (at 
the weight anticipated at the time of 
arrival at the airport), based on the as-
sumptions in § 121.185, can be brought 
to a full stop landing, within 70 percent 
of the effective length of the runway. 

(b) 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]