A320飞机维护手册 AMM AUTO FLIGHT 自动飞行3(96)

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 (a) Overview of predictions The FMS is in charge of predicting aircraft performance along the active flight plan. From the current state of the aircraft and of its environment, these predictions are computed versus defined lateral path, predicted atmospheric conditions and flight strategy defined for each flight phase. The current state of the aircraft is defined by : GW, CG, position, altitude, speed, active control modes (auto/manual in lateral, vertical (Ref. NOTE) and speed). Its environment includes time, wind and temperature. The lateral path considered is composed of all lateral legs and leg transitions except HM leg which is initially supposed not to be flown. But once the aircraft sequences the entry fix, a complete holding pattern is supposed to be flown and predictions assume the aircraft will exit the holding when overflying the fix again. If there is a lateral discontinuity between two points in the flight plan, predictions assume the aircraft will fly directly between the two points (direct distance is used). The flight strategy is defined phase by phase in Para. (2) below. When lateral path, vertical path or speed is in manual control, specific assumptions are used which are described in Para. (3),
 (4) and (5) below.
 These computations involve the use of a performance data base
 which contains aero/engine models of the aircraft and atmospheric
 models.

 1_ Display of predictions
 (Ref. Fig. 008)
 Some data resulting from computing the predictions are
 displayed on the MCDU.
 The flight plan pages display predicted time, speed, altitude
 and remaining fuel at each waypoint and pseudo-waypoint of the
 flight plan.
 Extra and remaining fuel at each fixed waypoint are displayed
 on the VERT REVISE page.
 Time and remaining fuel at destination are displayed on the
 FUEL PRED, CLIMB, CRUISE and DESCENT PERF pages. 

 

 Display of Predictions
 Figure 008

R 1EFF : 001-049, 051-099, 101-105, 151-199, 1 22-73-00Page 17/18 1201-212, 1Config-1 May 01/05 1 1 1CES

 Before transition to TAKEOFF phase, time predictions are in
 ETE if there is no ETT or time constraint in the F-PLN,
 otherwise they are in UTC format.
 After transition to TAKEOFF phase, time predictions are in UTC
 format.
 Speed predictions are in CAS or MACH according to the target
 used.
 Altitudes predictions are in feet below transition altitude
 and in flight levels above.

 2 Update of predictions
_ Predictions are regularly updated according to current aircraft parameters. Moreover, they are recomputed in case of modification of:
 -lateral flight plan (new waypoint, new dest, etc.).
 -vertical flight plan (cruise altitude, constraints, etc.).
 -entered predicted atmospheric conditions (wind, temperature).
 -cost index.

 -speed control (manual/auto).
 In that case, during recomputation time, predictions are
 dashed on the MCDU pages, and pseudo-waypoints are removed
 from the MCDU and ND.

 (b) Overview of vertical guidance
 1 Modes
_ FM vertical guidance modes are CLB, DES, and FINAL. They can be used only in LATERAL AUTO CONTROL.
 -CLB mode is used to climb up to FCU selected altitude, while observing altitude constraints.
 -DES mode is used to descent down to FCU selected altitude according to a precomputed vertical flight path, also observing altitude constraints.
 -FINAL mode can be used on a non-precision approach : VOR, NDB, or RNAV, to descend below FCU selected altitude on the vertical flight path.
 SPEED AUTO CONTROL can be engaged at any time. Except in EXP CLB, EXP DES or SRS mode, it allows the aircraft to fly at the optimum speed according to the selected cost index, while observing speed limits, and in LATERAL AUTO CONTROL, speed constraints, ICAO limits and holding pattern speeds.
 2 Submodes
_ Selected submode determines which control law is used to guide the aircraft. When CLB, DES, or FINAL mode is engaged, selected submode can be:

 -------------------------------------------------------------------|Elevator target| SPEED | VPATH | VPATH | FPA | V/S | |-----------------------------------------------------------------| | Thrust target | THRUST | THRUST | SPEED | SPEED | SPEED | -------------------------------------------------------------------| CLB mode | X | | | | | |---------------|---------|---------|---------|---------|---------| | DES mode | X | X | X | X | X | |---------------|---------|---------|---------|---------|---------| | FINAL mode | | | X | | | -------------------------------------------------------------------
VPATH is an FM pitch control law which can perform path captures or maintain the aircraft on the vertical flight path. Submode switching can occur only when DES mode is engaged.
　
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