曝光台 注意防骗
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General
During cruise flight, the A/T controls engine thrust to control
airspeed. This may be an FMC target speed or a speed selected
on the MCP.
During cruise flight, the normal DFCS pitch mode is VNAV. You
can also select altitude hold (ALT HOLD) as the DFCS pitch
mode.
VNAV Altitude Acquire/Altitude Hold
During DFCS VNAV climb, the airplane climbs to either the FMC
target altitude or to a lower intermediate altitude selected on the
MCP. The A/T is in the N1 mode. As the airplane gets near the
selected altitude, the DFCS acquires and levels off at the
altitude. The A/T goes from the N1 to the FMC SPD mode. These
are the annunciations as the airplane levels off:
* A/T goes from N1 to FMC SPD mode
* MCP IAS/MACH window is blank
* DFCS pitch mode is ALT ACQ then ALT HOLD for level off at
MCP altitude, or VNV PTH for FMC altitude.
VNAV Cruise
During DFCS VNAV cruise, the A/T is in FMC speed mode. The
A/T controls thrust to hold the FMC target airspeed while the
autopilot uses the elevators to hold altitude. These are the
annunciations during VNAV cruise:
* A/T is in FMC SPD mode
* A/T N1 and Speed mode lights are off on the MCP
* MCP IAS/MACH window is blank
* VNAV PTH is the DFCS pitch mode.
In VNAV cruise, the A/T is in FMC SPD mode and the A/T speed
mode switch light on the MCP is off. When the MCP mode switch
lights are off, this means that you can not de-select the active
mode by a push of the switch. To change the mode you must
select a new mode.
ALT HOLD
In the DFCS altitude hold mode (ALT HOLD), the target altitude
is the altitude selected on the MCP. During the climb (or
descent), as the airplane gets near the MCP selected altitude,
DFCS acquires and then holds this altitude. The A/T controls the
thrust levers to hold the selected target airspeed on the MCP
while the A/P uses the elevators to hold the selected altitude on
the MCP. These are the mode annunciations as DFCS acquires
and holds the selected altitude in the ALT HOLD mode:
* A/T is in MCP SPD mode
* Speed mode light is ON
* MCP IAS/MACH window shows the selected speed
* ALT ACQ then ALT HOLD is the DFCS pitch mode.
A/T SYSTEM - OPERATION - CRUISE
EFFECTIVITY
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737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
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A/T SYSTEM - OPERATION - CRUISE
A/T SYSTEM - OPERATION - CRUISE
EFFECTIVITY
SHZ ALL 22-31-00
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A/T SYSTEM - OPERATION - CRUISE
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737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
General
During descent, the A/T controls engine thrust to control either
the airspeed or descent rate (V/S), depending on the mode
selected.
During descent, the A/T normally retards thrust to idle
consistent with the DFCS pitch mode selected. The normal
DFCS pitch mode during descent is VNAV. The pilot can select
other modes. These are the DFCS pitch modes available for
descent:
* Vertical navigation (VNAV)
* Level change (LVL CHG)
* Vertical speed (V/S).
VNAV Descent
During DFCS VNAV cruise, when the airplane gets to the FMC
calculated top of descent (TOD) point, the A/T moves the T/Ls
slowly to the aft stops to retard thrust to idle for descent. These
are the mode indications:
* A/T goes from MCP SPD to RETARD to ARM mode
* A/T mode lights are off
* MCP IAS/MACH window is blank (FMC speed)
* VNAV is the DFCS pitch mode.
During DFCS VNAV descent, normally the thrust levers are at
idle and the A/T mode is ARM. The DFCS may request an A/T
mode change from ARM to FMC SPD mode to increase thrust to
hold the FMC target speed or descent rate.
The airplane continues to descend to the FMC or MCP selected
altitude. As the DFCS acquires and levels off at the selected
altitude, the A/T changes from ARM to FMC SPD mode (if not
already in FMC SPD). The A/T controls engine thrust to hold the
airspeed to the FMC target speed. The autopilot stays in VNAV
and uses the elevators for pitch control to hold the selected
altitude.
LVL CHG Descent
LVL CHG can be selected as the DFCS pitch mode for descent
(or climb). For descent, the pilot selects a lower target altitude
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