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AP/FD VERTICAL MODES - DESCENT MODE
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FCOM 19 AUG 10
AIRCRAFT BELOW THE DESCENT PROFILE
If the aircraft is below the descent profile, its speed will be maintained at target speed until it
reaches the descent profile. The lower margin becomes effective when the aircraft is on the
descent profile but has to loose speed in order to stay on it.
The intercept point on the navigation display is based on the following assumptions:
If the aircraft is flying at an altitude that is higher than both the descent speed limit
altitude and the destination elevation +5 000 ft:
The FMGES maintains the V/S at -1 000 ft/min and the target speed, until the aircraft reaches
the altitude constraint or intercepts the descent profile.
If the aircraft is flying at an altitude that is lower than either the descent speed limit
altitude, or the destination elevation +5 000 ft:
The FMGES maintains the V/S at - 500 ft/min and the target speed, until the aircraft reaches
the altitude constraint or intercepts the descent profile.
LEVELING OFF AT A CONSTRAINT
If the aircraft levels off at an ALT CSTR, the DES mode arms and remains armed until the
aircraft passes the constraint, then reengages (if the FCU altitude is set below the altitude of the
constraint).
If the FCU selected altitude is that of a constraint, the flight crew may continue the descent below
that altitude by turning the ALT knob and pushing it in. This arms the DES mode, which reengages
when the aircraft passes the constraint waypoint.
GUIDANCE IN A HOLD
Just before the aircraft enters a holding pattern, the speed target becomes the holding speed.
In the holding pattern, the DES mode commands the V/S at -1 000 ft while A/THR maintains the
holding speed. The aircraft will level off at the next altitude constraint if it is reached during the
hold.
The vertical deviation (VDEV) is based on the altitude at which the aircraft is supposed to cross
the exit fix in order to be properly positioned on the descent profile.
Until the flight crew exits the hold, the FMGES in DES mode will maintain V/S = -1 000 ft/min
considering downpath vertical constraint. This means that the aircraft will not descent below the
next altitude constraint. If the aircraft reaches the next altitude constraint it will level off and ALT
CST mode will engage.
A330/A340 FLIGHT CREW
OPERATING MANUAL
AIRCRAFT SYSTEMS
AUTO FLIGHT - FLIGHT GUIDANCE
AP/FD VERTICAL MODES - DESCENT MODE
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FCOM 19 AUG 10
TOO STEEP PATH
A descent segment is called “too steep path” when the FMGES predicts that the descent segment
between two constraint waypoints is impossible to fly at the planned descent speed with half
speedbrake extended.
When this occurs, the MCDU displays no predictions between the upper and the lower points of
the too steep path. Relevant message “TOO STEEP PATH” is displayed on MCDU.
A330/A340 FLIGHT CREW
OPERATING MANUAL
AIRCRAFT SYSTEMS
AUTO FLIGHT - FLIGHT GUIDANCE
AP/FD VERTICAL MODES - DESCENT MODE
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FCOM 19 AUG 10
When the aircraft reaches the beginning of the too steep path segment, the FM recomputes the
VDEV using an idle segment from the end of the too steep path segment.
A330/A340 FLIGHT CREW
OPERATING MANUAL
AIRCRAFT SYSTEMS
AUTO FLIGHT - FLIGHT GUIDANCE
AP/FD VERTICAL MODES - OPEN DESCENT MODE
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FCOM 19 AUG 10
GENERAL
Applicable to: ALL
The OPEN DES mode is a selected mode. It maintains a SPD/MACH (selected or managed) with the
AP/FD pitch mode while autothrust (if active) maintains IDLE thrust.
It is not to be used for final approach.
ENGAGEMENT CONDITIONS
Applicable to: ALL
The OPEN DES mode can only be engaged, if the following conditions are met:
‐ The aircraft has been in flight for more than 5 s
‐ LAND mode is not engaged
‐ The FCU selected altitude is lower than present altitude.
The OPEN DES mode is engaged by:
‐ Pulling out the ALT knob.
Note: When OP DES is engaged:
‐ The FMA displays “OP DES”
‐ The managed LVL/CH dot on the FCU goes out
‐ The system arms the ALT mode.
DISENGAGEMENT CONDITIONS
Applicable to:
The OPEN DES mode is disengaged by one of the following conditions:
‐ Manual engagement of another vertical mode
‐ Selection of an altitude higher than the present altitude. V/S (FPA) engages on the current V/S
(FPA).
DISENGAGEMENT CONDITIONS
Applicable to: ,
The OPEN DES mode is disengaged by one of the following conditions:
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A330/A340机组操作手册 FLIGHT CREW OPERATING MANUAL FCOM 2(46)
