757-200 MAINTENANCE MANUAL SUPPLEMENT Part I 维护手册补充(12)

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LRU replacement, for components in the Autostow system or in interfacing systems may cause faults to be stored.  Faults to be cleared by SAC light test.
The second test is a rigging test and retracts the actuator, for an indefinite period of time, to facilitate system rigging.  The "Speedbrake Do Not Arm" and “Test in Progress” lights are turned on during this test.
The third test is to check the module lamps and uses both test switches
simultaneously.

Faults detected on the ground are not latched in the SAC.  Therefore, when on the ground the fault indication will be rescinded once the fault condition is removed. Faults detected in flight are latched.
C.  In-Flight Test
The SAC automatically tests the Autostow function in-flight, to improve availability.  The test's logic is shown in Figure 5.  The test commands the Autostow actuator to retract, for four seconds, when the T.E. flaps are retracted to their cruise position.  Airspeed greater than 200 knots and Air/Ground logic prevent the test from operating when the airplane is on-ground.  In-flight flap retraction was selected as the test's trigger because:
(1)  
Inadvertent Autostow operation when the airplane is on-ground could be a hazardous event if combined with an RTO, whereas inadvertent in-flight Autostow operation is only a minor event, and

(2)  
The speedbrakes are not deployed during flap cleanup; the test is invisible to the flight crew, since Autostow operation does not cause speedbrake lever motion if the lever is down.

If Autostow fails to operate when commanded by the test, then the "Speedbrake Do Not Arm" light illuminates as described in previous paragraph titled ‘Failure Annunciation’, and shown in the Figure 6 logic.
Aviation Partners Boeing
757-200
MAINTENANCE MANUAL SUPPLEMENT
 Part I

D.  Dispatch Considerations
The following MMEL dispatch relief is provided if the Speedbrake Autostow function is inoperative.  Airspeed must not exceed 275 KAIS and severe turbulent air penetration speed is 275 KAIS or .78 Mach, whichever is lowest.  Alternatively, takeoff weight must not exceed 221,500 pounds with no airspeed restrictions.  Note that the Speedbrake Autowstow function must be considered inoperative if the Auto Speedbrake System has been deactivated
E.  Maintenance Requirements
The Speedbrake Autostow function requires periodic maintenance, in addition to the automatic in-flight test described above.  The numerical probability analysis in this document is based on a 6000 hour check interval for the items listed below; the actual check interval is to-be-determined, but will be documented in the Maintenance Planning Document AP57.2-0604.
.  
Check the Autostow mechanism to verify the spring has not failed and that there are no disconnects in the linkages or cam.
　
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