242 

14 CFR Ch. I (1–1–24 Edition) 

§ 25.353 

(1) The control system on control 

surface stops; or 

(2) A limit pilot force of 300 pounds 

from V

MC

to V

A

and 200 pounds from V

C

/ 

M

C

to V

D

/M

D

, with a linear variation 

between V

A

and V

C

/M

C

. 

(b) With the cockpit rudder control 

deflected so as always to maintain the 
maximum rudder deflection available 
within the limitations specified in 
paragraph (a) of this section, it is as-
sumed that the airplane yaws to the 
overswing sideslip angle. 

(c) With the airplane yawed to the 

static equilibrium sideslip angle, it is 
assumed that the cockpit rudder con-
trol is held so as to achieve the max-
imum rudder deflection available with-
in the limitations specified in para-
graph (a) of this section. 

(d) With the airplane yawed to the 

static equilibrium sideslip angle of 
paragraph (c) of this section, it is as-
sumed that the cockpit rudder control 
is suddenly returned to neutral. 

[Amdt. 25–91, 62 FR 40704, July 29, 1997] 

§ 25.353

Rudder control reversal condi-

tions. 

Airplanes with a powered rudder con-

trol surface or surfaces must be de-
signed for loads, considered to be ulti-
mate, resulting from the yaw maneu-
ver conditions specified in paragraphs 
(a) through (e) of this section at speeds 
from V

MC

to V

C

/M

C

. Any permanent de-

formation resulting from these ulti-
mate load conditions must not prevent 
continued safe flight and landing. The 
applicant must evaluate these condi-
tions with the landing gear retracted 
and speed brakes (and spoilers when 
used as speed brakes) retracted. The 
applicant must evaluate the effects of 
flaps, flaperons, or any other aero-
dynamic devices when used as flaps, 
and slats-extended configurations, if 
they are used in en route conditions. 
Unbalanced aerodynamic moments 
about the center of gravity must be re-
acted in a rational or conservative 
manner considering the airplane iner-
tia forces. In computing the loads on 
the airplane, the yawing velocity may 
be assumed to be zero. The applicant 
must assume a pilot force of 200 pounds 
when evaluating each of the following 
conditions: 

(a) With the airplane in unacceler-

ated flight at zero yaw, the flightdeck 
rudder control is suddenly and fully 
displaced to achieve the resulting rud-
der deflection, as limited by the con-
trol system or the control surface 
stops. 

(b) With the airplane yawed to the 

overswing sideslip angle, the flightdeck 
rudder control is suddenly and fully 
displaced in the opposite direction, as 
limited by the control system or con-
trol surface stops. 

(c) With the airplane yawed to the 

opposite overswing sideslip angle, the 
flightdeck rudder control is suddenly 
and fully displaced in the opposite di-
rection, as limited by the control sys-
tem or control surface stops. 

(d) With the airplane yawed to the 

subsequent overswing sideslip angle, 
the flightdeck rudder control is sud-
denly and fully displaced in the oppo-
site direction, as limited by the control 
system or control surface stops. 

(e) With the airplane yawed to the 

opposite overswing sideslip angle, the 
flightdeck rudder control is suddenly 
returned to neutral. 

[Amdt. No. 25–147, 87 FR 71210, Nov. 22, 2022] 

S

UPPLEMENTARY

C

ONDITIONS

 

§ 25.361

Engine and auxiliary power 

unit torque. 

(a) For engine installations— 
(1) Each engine mount, pylon, and ad-

jacent supporting airframe structures 
must be designed for the effects of— 

(i) A limit engine torque cor-

responding to takeoff power/thrust and, 
if applicable, corresponding propeller 
speed, acting simultaneously with 75% 
of the limit loads from flight condition 
A of § 25.333(b); 

(ii) A limit engine torque cor-

responding to the maximum contin-
uous power/thrust and, if applicable, 
corresponding propeller speed, acting 
simultaneously with the limit loads 
from flight condition A of § 25.333(b); 
and 

(iii) For turbopropeller installations 

only, in addition to the conditions 
specified in paragraphs (a)(1)(i) and (ii) 
of this section, a limit engine torque 
corresponding to takeoff power and 
propeller speed, multiplied by a factor 

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