A320飞机维护手册 AMM AUTO FLIGHT 自动飞行2(66)

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 In cruise, the cruise flight level is maintained by the elevators and the cruise speed by the thrust. For step climb segments, same guidance as for climb. For step descent segments, -1000 ft/mn and cruise speed are held.
 In descent during the idle path, guidance holds the descent path on elevators and the computed thrust on the throttles. For geometric path and repressurization segment, the descent path is also maintained but thrust holds the descent speed. Due to the holding of the descent path and inaccuracies on weather estimates or engine thrust model, the speed may vary during the descent.
 In managed speed control, the speed is allowed to vary within a certain margin which is displayed on the speed scale (PFD). If the lower margin is reached, then thrust is applied to maintain this lower margin. If the higher margin is reached, then, after having confirmed that idle thrust is set, the aircraft will diverge from the descent path by maintaining this higher speed margin on elevator. The MORE DRAG message may then be displayed in the conditions described above (predictions). Descent path control is recovered if the aircraft intercepts again the descent path. If a speed is selected on the FCU, this speed is held by the thrust during the whole descent. However the same reversion modes apply. During the whole descent in managed vertical control and managed lateral control, the desired altitude of the path is displayed on the PFD altitude scale and the vertical deviation is displayed on the MCDU.
 In approach, idle thrust is held during the descent segments and deceleration segments, speed hold is selected in the other segments. Descent path is maintained in descent segment, level flight is held elsewhere. During non-precision final descent a vertical deviation equivalent to an ILS deviation is displayed on the PFD.

 If managed lateral control and managed speed control are engaged but a selected vertical control mode is engaged, the aircraft speed will follow the speed profile defined along the lateral flight plan by prediction computations. This applies in all the flight phases.
 If managed lateral control is not engaged, the aircraft is not guided along the lateral flight plan. There is no reason therefore to limit the guidance to any constraint (altitude/speed/time). Only the speed limits which are altitude-dependent, are respected in climb and descent. In climb and descent segments the elevators control the ECON speed or the selected speed and the thrust set to max climb or idle. During descent, the FMS provides two additive information on the MCDU (PROG page) when GPS option is not activated:
 -
The minimum distance (displayed also on ND) to descent and decelerate from present altitude and speed to ground at VAPP.

 -
The direct distance from present position to the runway threshold, going through the LOC or Runway axis capture point.

 (9) Functions computed by the FMS As additional functions computed by the FMS, the following will be noted:
 (a)
 Pseudo waypoints used and displayed on the ND They are guidance mode dependent (the MCDU pseudo waypoints are based on the optimum profile). The pseudo waypoints are:

 (b)
 Engine out computations The system detects automatically an engine out situation from various signals received from the FADECs. In case of false detection, the crew can revert the FM in No engine failure condition. In ENG OUT situation no flight plan prediction is provided for takeoff, or Go Around phases. In all other phases F-PLN predictions are computed. The engine out max altitude, related to one engine failed, is provided in any flight phase on the MCDU.

 (c)
 Fuel planning Based on the flight plan fuel predictions, the system computes permanently fuel planning parameters such as route reserve, alternate fuel, final fuel and extra fuel. Two types of computation may be performed:

 -
Fuel planning can be computed on demand on ground before engine starts. It consists of the computation of the minimum block fuel for the trip, provided the zero fuel weight has been entered by the crew and assuming 0 extra fuel.

 -
Fuel predictions are computed on ground and in flight. This computes the extra fuel from the zero fuel weight and the fuel on board.

 

 1_ LEVEL which indicates the location of the capture point of the
 next level segment. In case of FCU altitude level, this symbol
 is cyan.
 In case of constraint level, this symbol is magenta. If a
 manual lateral mode is engaged this symbol is located on the
 track which will be flown by the aircraft.
 2_ Start of climb and top of descent which are located on the
 flight plan, where the aircraft should (white) or will (cyan)
 initiate the next climb or descent segment following the
　
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