(2)
The snubber valve on the inner cylinder of the shock strut moves up and down when the shock strut operates, acting as a one-way restrictor. While the shock strut is compressing, the snubber valve allows an unrestricted flow of hydraulic fluid from the upper chamber into the annular space between outer and inner cylinders. When the shock strut extends, the snubber valve moves upward, closing off holes in the upper bearing. This action restricts flow from the annular space and thus absorbs shock struct rebound. When the shock strut is serviced with fluid in the compressed position, the outer cylinder contains fluid all around the piston rod and in the space between the inner and outer cylinders. The shock strut is then inflated with nitrogen or air to the specified pressure.
(3)
Shocks are absorbed by the flow of hydraulic fluid through the annular space between the orifice and the tapered metering pin. As the shock strut is compressed, fluid flows through the orifice. Movement of the tapered metering pin through the orifice progressively varies the area of the annular space between orifice and pin. The variation in area results in an adjusted rate of hydraulic flow from the inner cylinder chamber to the upper side of the piston. This provides uniform control of impact loads on the airplane structure when landing.
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32-11-00
ALL ú ú 01 Page 11 ú Jun 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
(4)
Taxi shocks are cushioned by the increasing volumne of hydraulic fluid above the piston further compressing the volume of compressed air or nitrogen in the upper end of the outer cylinder. As the shock strut extends, there is a reversal of flow through the orifice. The hydraulic fluid now being forced from the upper to the lower side of the piston must pass through the space around the metering pin, and through holes in the orifice support tube. Also, fluid in the annular space between the inner and outer cylinders is forced through the snubber valve restriction, and through the upper bearing into the upper chamber. The resulting resistance to hydraulic flow dampens the return movement of the shock strut.
(5)
The truck positioning mechanism of the wing landing gear returns the wheel truck to a pitched-up position at an angle of 51.75 degrees with shock strut after liftoff, thus assuring correct truck positioning of the wing landing gear for retraction. The tilting force is supplied by hydraulic pressure acting on a floating piston. The truck positioner actuator consists of two interconnected cylinders. The main barrel contains the piston with internal transfer tube and capacitor piston. A compensator valve assembly, in check valve, out check valve, and lockup valve are installed in the side chamber. A high pressure relief in the head end controls flow between cylinders.
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
32-11-00
ALL ú ú 01 Page 12 ú Jun 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 FAULT ISOLATION/MAINT MANUAL
WING GEAR
COMPONENT SHT FIG. 102 QTY ACCESS/AREA REFERENCE
ACTUATOR - TRUCK POSITIONING 1 2 LEFT AND RIGHT WING GEAR 32-11-20
ASSEMBLY - SHOCK STRUT PRESSURE GAGE 2 2 LEFT AND RIGHT WING GEAR 32-11-02
ASSEMBLY - SIDE STRUT COMPONENT 1 2 LEFT AND RIGHT WING GEAR 32-11-27
BEAM - WALKING 1 2 LEFT AND RIGHT WING GEAR 32-11-15
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本文链接地址：747-400 AMM 飞机维护手册 起落架 LANDING GEAR 1(73)
