Code of Federal Regulations - Title 14

387

Federal Aviation Administration, DOT

§ 25.149

(b)

Directional control; airplanes with

four or more engines. Airplanes with
four or more engines must meet the re-
quirements of paragraph (a) of this sec-
tion except that—

(1) The two critical engines must be

inoperative with their propellers (if ap-
plicable) in the minimum drag posi-
tion;

(2) [Reserved]
(3) The flaps must be in the most fa-

vorable climb position.

(c)

Lateral control; general. It must be

possible to make 20

banked turns, with

and against the inoperative engine,
from steady flight at a speed equal to
1.3

R1, with—

(1) The critical engine inoperative

and its propeller (if applicable) in the
minimum drag position;

(2) The remaining engines at max-

imum continuous power;

(3) The most unfavorable center of

gravity;

(4) Landing gear (i) retracted and (ii)

extended;

(5) Flaps in the most favorable climb

position; and

(6) Maximum takeoff weight.
(d)

Lateral control; roll capability. With

the critical engine inoperative, roll re-
sponse must allow normal maneuvers.
Lateral control must be sufficient, at
the speeds likely to be used with one
engine inoperative, to provide a roll
rate necessary for safety without ex-
cessive control forces or travel.

(e)

Lateral control; airplanes with four

or more engines. Airplanes with four or
more engines must be able to make 20

banked turns, with and against the in-
operative engines, from steady flight at
a speed equal to 1.3

R1, with max-

imum continuous power, and with the
airplane in the configuration pre-
scribed by paragraph (b) of this section.

(f)

Lateral control; all engines oper-

ating. With the engines operating, roll
response must allow normal maneuvers
(such as recovery from upsets produced
by gusts and the initiation of evasive
maneuvers). There must be enough ex-
cess lateral control in sideslips (up to
sideslip angles that might be required
in normal operation), to allow a lim-
ited amount of maneuvering and to
correct for gusts. Lateral control must
be enough at any speed up to

to provide a peak roll rate necessary

for safety, without excessive control
forces or travel.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–42, 43 FR 2321, Jan. 16,
1978; Amdt. 25–72, 55 FR 29774, July 20, 1990;
Amdt. 25–108, 67 FR 70827, Nov. 26, 2002;
Amdt. 25–115, 69 FR 40527, July 2, 2004]

§ 25.149

Minimum control speed.

(a) In establishing the minimum con-

trol speeds required by this section, the
method used to simulate critical en-
gine failure must represent the most
critical mode of powerplant failure
with respect to controllability ex-
pected in service.

(b) V

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
maintain straight flight with an angle
of bank of not more than 5 degrees.

(c)

may not exceed 1.13

with—

(1) Maximum available takeoff power

or thrust on the engines;

(2) The most unfavorable center of

gravity;

(3) The airplane trimmed for takeoff;
(4) The maximum sea level takeoff

weight (or any lesser weight necessary
to show

);

(5) The airplane in the most critical

takeoff configuration existing along
the flight path after the airplane be-
comes airborne, except with the land-
ing gear retracted;

(6) The airplane airborne and the

ground effect negligible; and

(7) If applicable, the propeller of the

inoperative engine—

(i) Windmilling;
(ii) In the most probable position for

the specific design of the propeller con-
trol; or

(iii) Feathered, if the airplane has an

automatic feathering device acceptable
for showing compliance with the climb
requirements of § 25.121.

(d) The rudder forces required to

maintain control at

may not ex-

ceed 150 pounds nor may it be nec-
essary to reduce power or thrust of the
operative engines. During recovery, the
airplane may not assume any dan-
gerous attitude or require exceptional
piloting skill, alertness, or strength to

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