243 

Federal Aviation Administration, DOT 

§ 25.362 

(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] 

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 
accounting for propeller control sys-
tem malfunction, including quick 
feathering, acting simultaneously with 
1g level flight loads. In the absence of 

a rational analysis, a factor of 1.6 must 
be used. 

(2) The limit engine torque to be con-

sidered under paragraph (a)(1) of this 
section must be obtained by— 

(i) For turbopropeller installations, 

multiplying mean engine torque for the 
specified power/thrust and speed by a 
factor of 1.25; 

(ii) For other turbine engines, the 

limit engine torque must be equal to 
the maximum accelerating torque for 
the case considered. 

(3) The engine mounts, pylons, and 

adjacent supporting airframe structure 
must be designed to withstand 1g level 
flight loads acting simultaneously with 
the limit engine torque loads imposed 
by each of the following conditions to 
be considered separately: 

(i) Sudden maximum engine decelera-

tion due to malfunction or abnormal 
condition; and 

(ii) The maximum acceleration of en-

gine. 

(b) For auxiliary power unit installa-

tions, the power unit mounts and adja-
cent supporting airframe structure 
must be designed to withstand 1g level 
flight loads acting simultaneously with 
the limit torque loads imposed by each 
of the following conditions to be con-
sidered separately: 

(1) Sudden maximum auxiliary power 

unit deceleration due to malfunction, 
abnormal condition, or structural fail-
ure; and 

(2) The maximum acceleration of the 

auxiliary power unit. 

[Amdt. 25–141, 79 FR 73468, Dec. 11, 2014] 

§ 25.362

Engine failure loads. 

(a) For engine mounts, pylons, and 

adjacent supporting airframe struc-
ture, an ultimate loading condition 
must be considered that combines 1g 
flight loads with the most critical 
transient dynamic loads and vibra-
tions, as determined by dynamic anal-
ysis, resulting from failure of a blade, 
shaft, bearing or bearing support, or 
bird strike event. Any permanent de-
formation from these ultimate load 
conditions must not prevent continued 
safe flight and landing. 

(b) The ultimate loads developed 

from the conditions specified in para-
graph (a) of this section are to be— 

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