(b)
Display The DIST TO DEST and DIR DIST TO DEST are output for display on the MCDU. The DIST TO DEST is displayed on F-PLN page on the MCDU, in line 6 dedicated to the destination.
(5)
Influence of transitions The lateral reference parameters defined in Para. (2) depend on the type of leg as the path errors. But only the desired track and path errors depend on the type of transition. The influence is given hereafter.
-Type I : Time to go, bearing to go, distance to go are referred to the active leg termination. Desired track and crosstrack errors are computed for the curved path of the transition.
Lateral Path Error on Circular Path
Figure 032
Along Track Distance
Figure 033
-
Type II : Distance to go, time to go, bearing to go, crosstrack error, desired track are all referenced to the path to be captured. For holding pattern entries, distance to go, time to go, bearing to go are referred to the holding fix. Crosstrack error and desired track are always referenced to the associated part of the entry path that guidance is currently controlling. When an entry ends in a type II transition, they are referenced to the inbound course of the leg.
-
Type III : The parameters are referenced to the heading leg.
-
Type IV : All parameters except crosstrack error and desired track are referenced to the next leg at the start of transition. Crosstrack error and desired track are referenced to the arc until sequencing of the arc.
-
Type V : All parameters are referenced to the course leg.
G. NAV Guidance Mode
(1) NAV mode engagement conditions
Lateral auto pilot modes available are: (Ref. 22-12-00)
-autocontrol
-heading/track control.
When lateral autocontrol is selected, four modes are available:
-RWY
-NAV
-LOC (capture/track) and LAND
-GO AROUND.
Only NAV mode is managed by the FM.
(a) Autocontrol mode (NAV) This mode is armed if the pilot pushes the FCU heading/track selector knob (FCU : Flight Control Unit). Autocontrol engagement depends upon whether the aircraft is within the capture zone of the active leg. This capture zone is unlimited for heading/track legs (VX or CX legs except CF leg), this means that if LAT AUTO control is armed while one of these legs is active, it is immediately engaged. For fixed path legs, the capture zone is a 1 NM wide zone around the active leg, or at the capture point which allows a comfortable F-PLN capture without overshoot. If the aircraft is within the capture zone, then autocontrol is engaged (FCU heading/track display is dashed). Else, the previously selected HDG/TRK remains displayed and modifiable on the FCU until autocontrol is engaged. In this case, if the track corresponding to the selected heading/track intercepts the F-PLN before the TO waypoint, the F-PLN becomes as shown in the following figure. Else the flight plan remains as original.
(Ref. Fig. 034, 035)
Note that performing a DIR TO revision engages NAV if it was not
active.
When autocontrol is active, the aircraft flies the flight plan as
defined by the displays on the MCDU and on the ND (except when
LOC mode is active).
The autocontrol engagement state is checked each time one of the
following events occurs :
-autocontrol is selected via the FCU
-
a F-PLN change occurs which affects the active leg
-
a parallel offset is entered or cancelled.
If the lat autocontrol is deactivated, the control reverts to
heading/track control and the heading or track is synchronized
with the current one before loss of the autocontrol.
(b) Heading/track control Heading/track is engaged if the pilot chooses a target by means of the heading/track selector knob and pulls the knob. The FCU displays the selected heading or track. Selection of heading or track mode is done via the HDG-V/S/TRK-FPA selection pushbutton switch on the FCU. In heading/track mode, the flight plan remains active without modification. On ND, the flight plan becomes dashed. Leg sequencing is automatic as if LAT AUTO CONTROL remained active.
(2) En route and terminal area guidance submodes (NAV mode engaged) The various guidance submodes in these areas are:
-lateral path for geographical path legs
-heading for heading legs
-track for course legs
(a) Guidance mode selection The selection of the submode is determined according to the leg type of the active leg or the transition. If the active leg is a heading leg (VX legs), the heading submode is requested. If the active leg is a course leg (CX legs except CF leg), the track submode is requested. If the active leg is not a heading leg or a course leg (except CF leg), the lateral path submode is requested. This mode is deactivated if one of the following events occurs:
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：A320飞机维护手册 AMM AUTO FLIGHT 自动飞行3(76)
