(a)
A module return line check valve provides free flow from the metered pressure port to the antiskid valve via the shutoff valve, and prevents residual pressure in the brake return line.
(6)
Restrictor
(a)
A 2-way restrictor or orifice is in the system pressure line upstream of the shutoff valve. The restrictor limits hydraulic flow during failure conditions (missing O-ring on antiskid valve or shutoff valve, or failed check valve in the shutoff valve).
32-42-00
ALL ú ú 12 Page 11 ú Sep 28/01
A
757 MAINTENANCE MANUAL
F. Normal Antiskid Module Operation (Fig. 5)
(1) The torque motor armature in the first stage of the antiskid valve (servo valve assembly) sits itself between two nozzles as a function of input current. One nozzle is supplied with system pressure and the other is connected to return. With no command applied, the motor moves the armature against the return nozzle and control pressure equals supply pressure. With full current supplied, the motor moves the armature against the pressure nozzle and control pressure equals return pressure. For each in between value of input current there is a characteristic armature position and control pressure value. The valve varies pressure from a high of pilot metered pressure to a low of no pressure (release).
SYSTEM PRESSURE 1ST-STAGE
METERED PRESSURE (EHSV SERVO VALVE ASSEMBLY)
RETURN ARMATURE
BYPASS CHECK
INTERNAL CONTROL ORIFICE VALVE
NON LRU BIAS SPRING
FILTER SHUTOFF (4 PLACES) VALVE
RIGHT HYDRUALIC SYSTEM PRESSURE
RETURN
LRU FILTER BRAKE RETURN
METERED LINE
PRESSURE CHECK VALVE
2ND-STAGETRANSIT
(SLIDE AND SLEEVE ASSEMBLY) FUSE
OUTLET ORIFICERESET KNOB BRAKE BRAKE BRAKE BRAKE BRAKE BRAKE RETURN CHECK VALVE
AFT RELEASED AFT FWD APPLIED FWD
Antiskid Module (Normal) Functional Schematic Figure 5
32-42-00
ALL ú ú 07 Page 12 ú Jun 15/87
A
757 MAINTENANCE MANUAL
(2)
The second stage (slide and sleeve assembly) is a spool valve driven by control pressure (from the first stage) on one end of the spool and brake pressure on the other. When control pressure exceeds pilot's metered pressure, the spool moves to port metered pressure directly to the brake. In the metering region, the second stage spool works as a pressure follower such that the brake pressure equals the control pressure. The bias spring on one end of the spool holds the spool down to allow full applied pressure to the brakes when the first stage is de-energized. A control orifice slows the second stage valve movement to control input. At the brake port an outlet orifice slows the application rate of the brakes in response to pressure input. When the metered pressure is removed, the return check valve allows free flow return from the brakes.
G.
Alternate Antiskid Module Operation (Fig. 6)
(1)
The alternate module functions the same as the normal module except that the module requires no shutoff valve or restrictor in its operation.
H. Antiskid Shuttle Valves (Fig. 7)_______________________
1ST-STAGE (EHSV SERVO ARMATURE VALVE ASSEMBLY)
CONTROL ORIFICE
LEFT (ALTN)
HYDRAULIC
SYSTEM
PRESSURE RETURN
PILOT METERED CHECK VALVE RETURN LINE BRAKE PRESSURE
2ND-STAGE LRU FILTER
(SLIDE AND
SLEEVE ASSEMBLY)
SYSTEM PRESSURE
OUTLET ORIFICE
METERED PRESSURE
FUSE RETURN CHECK VALVE
RETURN RESET
KNOB BRAKE BRAKE
AFT FWD
(FULL APPLY) (FULL RELEASE)
Antiskid Module (Alternate) Functional Schematic
Figure 6
32-42-00
ALL ú ú 12 Page 13 ú Sep 28/00
A
757 MAINTENANCE MANUAL
PRESSURE ALTERNATE DECK (REF) MOUNTING
ANTISKID SUPPORT
A
INPUT (REF)
NORMAL ANTISKID INPUT
SEEA ANTISKID
A
SHUTTLE VALVE MODULE
OUTBD FWD
TO BRAKES
LEFT WHEEL WELL SHOWN RIGHT WHEEL WELL SIMILAR
A
ALTERNATE
ANTISKID
SLIDE PLUG SHUTTLE INPUT
(NORMALLY INSTALLED) SEAL DETENT
SEE B FOR
DEACTIVATION TOOL SHUTTLE SEAL
NORMAL ANTISKID INPUT
SHUTTLE
VALVE
SHUTTLE
DEACTIVATION VALVE
PLUNGER DEACTIVATION
FILTER TOOL
TO BRAKES
A-A B
Antiskid Shuttle Valve
Figure 7
32-42-00
ALL ú ú 01 Page 14 ú Mar 15/87
中國航空網 m.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：757 AMM 飛機維護手冊 起落架 CHAPTER 32 - LANDING GEAR 2(163)
