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Federal Aviation Administration, DOT 

§ 25.723 

and the full power of the surface actu-
ating system is applied. 

[Amdt. 25–72, 55 FR 29777, July 20, 1990] 

§ 25.703

Takeoff warning system. 

A takeoff warning system must be in-

stalled and must meet the following re-
quirements: 

(a) The system must provide to the 

pilots an aural warning that is auto-
matically activated during the initial 
portion of the takeoff roll if the air-
plane is in a configuration, including 
any of the following, that would not 
allow a safe takeoff: 

(1) The wing flaps or leading edge de-

vices are not within the approved range 
of takeoff positions. 

(2) Wing spoilers (except lateral con-

trol spoilers meeting the requirements 
of § 25.671), speed brakes, or longitu-
dinal trim devices are in a position 
that would not allow a safe takeoff. 

(b) The warning required by para-

graph (a) of this section must continue 
until— 

(1) The configuration is changed to 

allow a safe takeoff; 

(2) Action is taken by the pilot to 

terminate the takeoff roll; 

(3) The airplane is rotated for take-

off; or 

(4) The warning is manually deacti-

vated by the pilot. 

(c) The means used to activate the 

system must function properly 
throughout the ranges of takeoff 
weights, altitudes, and temperatures 
for which certification is requested. 

[Amdt. 25–42, 43 FR 2323, Jan. 16, 1978] 

L

ANDING

G

EAR

 

§ 25.721

General. 

(a) The main landing gear system 

must be designed so that if it fails due 
to overloads during takeoff and landing 
(assuming the overloads to act in the 
upward and aft directions), the failure 
mode is not likely to cause— 

(1) For airplanes that have passenger 

seating configuration, excluding pilots 
seats, of nine seats or less, the spillage 
of enough fuel from any fuel system in 
the fuselage to constitute a fire hazard; 
and 

(2) For airplanes that have a pas-

senger seating configuration, excluding 

pilots seats, of 10 seats or more, the 
spillage of enough fuel from any part of 
the fuel system to constitute a fire 
hazard. 

(b) Each airplane that has a pas-

senger seating configuration excluding 
pilots seats, of 10 seats or more must 
be designed so that with the airplane 
under control it can be landed on a 
paved runway with any one or more 
landing gear legs not extended without 
sustaining a structural component fail-
ure that is likely to cause the spillage 
of enough fuel to constitute a fire haz-
ard. 

(c) Compliance with the provisions of 

this section may be shown by analysis 
or tests, or both. 

[Amdt. 25–32, 37 FR 3969, Feb. 24, 1972] 

§ 25.723

Shock absorption tests. 

(a) The analytical representation of 

the landing gear dynamic characteris-
tics that is used in determining the 
landing loads must be validated by en-
ergy absorption tests. A range of tests 
must be conducted to ensure that the 
analytical representation is valid for 
the design conditions specified in 
§ 25.473. 

(1) The configurations subjected to 

energy absorption tests at limit design 
conditions must include at least the 
design landing weight or the design 
takeoff weight, whichever produces the 
greater value of landing impact energy. 

(2) The test attitude of the landing 

gear unit and the application of appro-
priate drag loads during the test must 
simulate the airplane landing condi-
tions in a manner consistent with the 
development of rational or conserv-
ative limit loads. 

(b) The landing gear may not fail in 

a test, demonstrating its reserve en-
ergy absorption capacity, simulating a 
descent velocity of 12 f.p.s. at design 
landing weight, assuming airplane lift 
not greater than airplane weight act-
ing during the landing impact. 

(c) In lieu of the tests prescribed in 

this section, changes in previously ap-
proved design weights and minor 
changes in design may be substantiated 
by analyses based on previous tests 
conducted on the same basic landing 

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