(3)
Landing gear doors, their operating mechanism, and their supporting structures mustbedesignedfortheyawing maneuversprescribedforthe airplanein additiontothe conditions of airspeed andloadfactorprescri-bedinparagraphs(a)(1) and(2) of this section.

′
Elodie Roux. Septembre 2003
Subpart D : Design and Construction
(b)
Landing gear lock. There must be positive means to keep the landing gear extended, in .ight and on the ground.

(c)
Emergency operation. There must be an emergency means for extending the landing gear in the event of–

(1)
Any reasonablyprobablefailureinthe normal retraction system; or

(2)
Thefailure of any single source ofhydraulic, electric, or equivalent energy supply.

(d)
Operation test. The proper functioning of the retracting mechanism must be shown by operation tests.

(e)
Position indicator and warning device. If a retractable landing gear is used, there mustbe alandinggearpositionindicator(as well as necessary switches to actuate the indicator) or other means to inform the pilot that the gear is securedinthe extended(or retracted)position.This means mustbedesigned as follows :

(1)
If switches are used, they mustbelocated and coupled to thelandinggear mechanical systems in a manner that prevents an erroneous indication of ”down andlocked” if thelandinggearis notin afully extendedposition, or of ”up and locked” if the landing gear is not in the fully retracted position. The switches may be located where they are operated by the actual landing gear locking latch or device.

(2)
[The .ightcrew must be given an aural warning that functions conti-nuously, or is periodically repeated, if a landing is attempted when the landing gear is not locked down.

(3)
The warning mustbegivenin su.cienttimeto allowthelandinggearto be locked down or a go-around to be made.

(4)
Theremust notbeamanual shut-o.meansreadily availabletothe .ight-crewfor the warning requiredbyparagraph(e)(2) ofthis section suchthat it could be operated instinctively, inadvertently, or by habitual re.exive action.

(5)
The system used to generate the aural warning must be designed to eli-minate false or inappropriate alerts.

(6)
Failures of systems used to inhibit the landing gear aural warning, that would prevent the warning system from operating, must be improbable.]

(f)
Protection of equipment in wheel wells. Equipment that is essential to safe operationof the airplaneand thatislocatedin wheel wells mustbeprotected from the damaging e.ects of–

(1)
A bursting tire, unlessit is shown that a tire cannotburstfrom overheat; and

(2)
A loose tire tread, unless it is shown that a loose tire tread cannot cause damage.

Amdt. 25-75, E.. 1/6/92
FAR 25.731 : Wheels.
(a) Each main and nose wheel must be approved.
(b)
The maximum static load rating of each wheel may not be less than the cor-responding static ground reaction with–

(1)
Design maximum weight; and

(2)
Critical center of gravity.

(c)
The maximum limit load rating of each wheel must equal or exceed the maxi-mum radial limit load determined under the applicable ground load require-ments of this part.

(d)
[Overpressure burst prevention. Means must be provided in each wheel to prevent wheel failure and tire burst that may result from excessive pressu-rization of the wheel and tire assembly.

(e)
Braked wheels. Each braked wheel must meet the applicable requirements of Sec. 25.735.]

Amdt. 25-107, E.. 5/24/2002
FAR 25.733 : Tires.
(a)
When a landing gear axle is .tted with a single wheel and tire assembly, the wheel must be .tted with a suitable tire of proper .t with a speed rating approved by the Administrator that is not exceeded under critical conditions and with a load rating approved by the Administrator that is not exceeded under–
　
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