199 

Federal Aviation Administration, DOT 

§ 23.149 

(5) All propeller controls in the posi-

tion at which compliance with § 23.69(a) 
has been shown. 

(c) For all airplanes, it must be 

shown that the airplane is safely con-
trollable without the use of the pri-
mary lateral control system in any all- 
engine configuration(s) and at any 
speed or altitude within the approved 
operating envelope. It must also be 
shown that the airplane’s flight char-
acteristics are not impaired below a 
level needed to permit continued safe 
flight and the ability to maintain atti-
tudes suitable for a controlled landing 
without exceeding the operational and 
structural limitations of the airplane. 
If a single failure of any one con-
necting or transmitting link in the lat-
eral control system would also cause 
the loss of additional control sys-
tem(s), compliance with the above re-
quirement must be shown with those 
additional systems also assumed to be 
inoperative. 

[Doc. No. 27807, 61 FR 5188, Feb. 9, 1996] 

§ 23.149

Minimum control speed. 

(a) V

MC

is the calibrated airspeed at 

which, when the critical engine is sud-
denly made inoperative, it is possible 
to maintain control of the airplane 
with that engine still inoperative, and 
thereafter maintain straight flight at 
the same speed with an angle of bank 
of not more than 5 degrees. The method 
used to simulate critical engine failure 
must represent the most critical mode 
of powerplant failure expected in serv-
ice with respect to controllability. 

(b) V

MC

for takeoff must not exceed 

1.2 V

S1

, where V

S1

is determined at the 

maximum takeoff weight. V

MC

must be 

determined with the most unfavorable 
weight and center of gravity position 
and with the airplane airborne and the 
ground effect negligible, for the takeoff 
configuration(s) with— 

(1) Maximum available takeoff power 

initially on each engine; 

(2) The airplane trimmed for takeoff; 
(3) Flaps in the takeoff position(s); 
(4) Landing gear retracted; and 
(5) All propeller controls in the rec-

ommended takeoff position through-
out. 

(c) For all airplanes except recipro-

cating engine-powered airplanes of 
6,000 pounds or less maximum weight, 

the conditions of paragraph (a) of this 
section must also be met for the land-
ing configuration with— 

(1) Maximum available takeoff power 

initially on each engine; 

(2) The airplane trimmed for an ap-

proach, with all engines operating, at 
V

REF

, at an approach gradient equal to 

the steepest used in the landing dis-
tance demonstration of § 23.75; 

(3) Flaps in the landing position; 
(4) Landing gear extended; and 
(5) All propeller controls in the posi-

tion recommended for approach with 
all engines operating. 

(d) A minimum speed to inten-

tionally render the critical engine in-
operative must be established and des-
ignated as the safe, intentional, one- 
engine-inoperative speed, V

SSE

. 

(e) At V

MC

, the rudder pedal force re-

quired to maintain control must not 
exceed 150 pounds and it must not be 
necessary to reduce power of the opera-
tive engine(s). During the maneuver, 
the airplane must not assume any dan-
gerous attitude and it must be possible 
to prevent a heading change of more 
than 20 degrees. 

(f) At the option of the applicant, to 

comply with the requirements of 
§ 23.51(c)(1), V

MCG

may be determined. 

V

MCG

is the minimum control speed on 

the ground, and is the calibrated air-
speed during the takeoff run at which, 
when the critical engine is suddenly 
made inoperative, it is possible to 
maintain control of the airplane using 
the rudder control alone (without the 
use of nosewheel steering), as limited 
by 150 pounds of force, and using the 
lateral control to the extent of keeping 
the wings level to enable the takeoff to 
be safely continued. In the determina-
tion of V

MCG

, assuming that the path of 

the airplane accelerating with all en-
gines operating is along the centerline 
of the runway, its path from the point 
at which the critical engine is made in-
operative to the point at which recov-
ery to a direction parallel to the cen-
terline is completed may not deviate 
more than 30 feet laterally from the 
centerline at any point. V

MCG

must be 

established with— 

(1) The airplane in each takeoff con-

figuration or, at the option of the ap-
plicant, in the most critical takeoff 
configuration; 

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