(4)
The warning is manually deactivated by the pilot.

(c)
Themeansused to activatethe systemmustfunctionproperly throughoutthe ranges of takeo. weights, altitudes, and temperatures for which certi.cation is requested.]

Amdt. 25-42, E.. 3/1/78
47.4 Landing Gear
FAR 25.721 : General.
(a)
[The main landing gear system must be designed so that if it fails due to overloads during takeo. and landing (assuming the overloads to act in the upward and aft directions), the failure mode is not likely to cause–

(1)
For airplanes thathave apassenger seatingcon.guration, excludingpilots seats, of nine seats orless, the spillage of enoughfuelfrom anyfuel system in the fuselage to constitute a .re hazard; and

(2)
For airplanes thathave apassenger seatingcon.guration, excludingpilots seats,of10 seatsor more,thespillageof enoughfuelfrom anypartof the fuel system to constitute a .re hazard.

(b)
Each airplane that has apassenger seating con.guration excludingpilot seats, of 10 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 failure that is likely to cause the spillage of enough fuel to constitute a .re hazard.

(c)
Compliance with the provisions of this section may be shown by analysis or tests, or both.]

Amdt. 25-32, E.. 5/1/72
FAR 25.723 : Shock absorption tests.
(a) [The analyticalrepresentation of the landinggeardynamic characteristics that is used in determining the landing loads must be validated by energy absorp-tion tests. A range of tests must be conducted to ensure that the analytical representation is valid for the design conditions speci.ed in Sec. 25.473.
(1) The con.gurations subjected to energy absorption tests at limit design conditions must include at least the design landing weight or the design takeo. weight, whichever produces the greater value of landing impact energy.
(2) The test attitude of the landing gear unit and the application of ap-propriate drag loads during the test must simulate the airplane landing conditions in a manner consistent with the development of rational or conservative limit loads.
(b)
The landing gear may not fail in a test, demonstrating its reserve energy ab-sorption capacity, simulating a descent velocity of 12 f.p.s. at design landing weight, assuming airplane lift not greater than airplane weight acting during the landing impact.

(c)
In lieu of the tests prescribed in this section, changes in previously approved design weightsand minorchangesindesignmaybe substantiatedby analyses based onprevious tests conducted on the samebasiclandinggear system that has similar energy absorption characteristics.]

Amdt. 25-103, E.. 6/15/2001
FAR25.725 :[Reserved.]
Reserved.
Amdt. 25-103, E.. 6/15/2001

FAR25.727 :[Reserved.]
Reserved.
Amdt. 25-103, E.. 6/15/2001

FAR 25.729 : Retracting mechanism.
(a) General. For airplanes with retractable landing gear, the following apply :
(1)
Thelandinggear retractingmechanism, wheel welldoors, and supporting structure, must be designed for–

(i)
The loads occurring in the .ight conditions when the gear is in the retractedposition;

(ii)
The combination of friction loads, inertia loads, brake torque loads, air loads, and gyroscopic loads resulting from the wheels rotating at a peripheral speed equal to 1.3VS (with the .aps in takeo. position at design takeo. weight), occurring during retraction and extension at any airspeed up to 1.6VS1 (withthe .apsintheapproachposition at design landing weight), and

(iii) Any load factor up to those speci.ed in Sec. 25.345(a) for the .aps extended condition.

(2)
Unless there are other means to decelerate the airplane in .ight at this speed, thelandinggear, the retracting mechanism, and the airplane struc-ture(including wheel welldoors) mustbedesigned towithstand the .ight loads occurring with the landing gear in the extended position at any speed up to 0.67VC.
　
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