(f)
Two engagement conditions exist: one with the A/T ARM in the OFF position and the other with the A/T ARM switch in the ARM position. 1) When the A/T ARM discrete is high or in the ARM position
and the FMC receives the VNAV discrete from the MCP, then the FMC shall transmit the valid thrust target with the appropriate A/T mode request.
2) When the A/T ARM discrete is low, the FMC shall detect the VNAV discrete from the MCP and transmit the valid thrust target. The thrust target shall be initialized to its current value and ramped to the FMC desired target. All the A/T mode requests shall remain low.
9. Thrust Management (Fig. 35)_________________
A. General
(1) The FMC's thrust management function is responsible for throttle control throughout the entire flight regime. This includes takeoff, climb, cruise, descent and go around.
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(2)
There are three major process within the thrust management function. These are Main Autothrottle Control, Thrust Limit Computations (TLC) and the Autothrottle Servo Card operations.
(3)
The thrust management function requires sensor inputs from the ADCs and IRSs. It also utilizes inputs from the EIUs, cockpit analog signals, MCP, performance function, and the offside FMC. This data is used to control the thrust requirements for all of the airplanes flight path operations.
B. Main Autothrottle Control
(1)
The main autothrottle control performs the major functions within the TMF. These functions consist of determining throttle modes, engagement of these modes, control laws, monitoring the servo loop, performing the stopper test, annunciations and single state definitions.
(2)
Mode logic
(a)
The autothrottle mode logic function comprises the manual and automatic selection of available throttle modes.
(b)
Manually selected modes available from the MCP are speed mode, thrust mode, flight level change mode and VNAV mode. Modes available from other sources are go-around, automatic takeoff and flare retard modes.
(c)
Autothrottle mode selection is possible only when the A/T ARM is armed and the autothrottle engage logic is true.
(3)
Mode engage conditions
(a)
VNAV Mode
1) The VNAV mode request will be engaged if the airplane is airborne, the A/T is armed, the VNAV mode is selected on the MCP, TO limits are false or the airplane is above 400 feet above ground level (AGL) with TO limits active and no disabling states. When VNAV mode is engaged, it can then request the following modes: a) VNAV Mach Control mode b) VNAV Speed Control mode c) VNAV Dormant mode d) VNAV Idle mode e) VNAV Thrust mode
(b)
Go-Around mode
1) There are two types of A/T GA modes which are selected when there are no disabling states and the TO/GA switch is pressed with the A/T enabled and the go-around arm state is true. The go-around arm state is when the airplane is out of TO limits, airborne and having non-zero flaps or having A/P glide slope mode engaged.
2) The two types of go-around modes are A/T G/A mode and A/T EPR G/A mode. The A/T G/A mode increases the thrust at a climb rate subjected to the G/A thrust limit. The A/T EPR GA mode increases the thrust to a EPR limit (maximum thrust).
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L-ADC
~2 429
C-EIU1
LO
429 S
L-FMC
LO
R-FMC SPEED
P
L-ADCXMTR
E
C-ADC FROM
AUTOTHROTTLE
E
R-FMC C-FCC
R-FMC
CAPT ADCì MONITOR SERVO
D
OUTPUT TOSOURCE SELECT ì DETERMINE ENGAGE LOGICGUIDANCE
R
FMC 3 MASTERC
ì PERFORM STOPPER TEST OUTPUT TO
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