-horizontal path : capture and holding of path that the FM computes
-heading : holding of heading selected by the FM
-track : holding of track selected by the FM
(d)
Elaboration of orders The principle of elaboration of AP/FD orders by the heading or track holding laws has been described in the previous chapter. When the selected guidance consists in holding a horizontal path computed by the FM, the AP/FD orders are elaborated by the horizontal path law.
(Ref. Fig. 009)
NOTE : Phi N is a precommand determined by the FM. XTK and TAE
____ are used to slave the aircraft to this predetermined path.
(e) Operational logic The logic which enables to arm and activate the NAV mode is as follows :
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1_ NAV armed
The NAV is armed if a lateral flight plan is available and if
one of the conditions below is present :
- push action on the heading/track selector knob except if the
LOC mode is active
- aircraft on ground on condition that there is no preset
heading value or any mode except the Runway mode active
- action on APPR pushbutton switch on the FCU and on condition
that a RNAV approach is selected on the MCDU.
The NAV mode is disarmed through:
- selection of a preset heading value
- pull action on the heading selector knob
- arming of LOC mode (action on the LOC pushbutton switch)
- selection of the GO AROUND mode
- loss of the RNAV approach arming essentially due to action
on the APPR pushbutton switch.
2_ NAV active
The NAV mode becomes active in presence of one of the
conditions below:
- the conditions of capture of the flight plan are met, with
the NAV mode armed at takeoff, switching to NAV takes place
at 30 ft.
- DIR TO is selected on the MCDU on condition that the LOC
mode is not selected below 700 ft.
This mode is lost upon selection of another lateral mode and
through the loss of the lateral flight plan except when the
APPR mode is engaged.
(a) Characteristics This mode enables to capture and track a LOCALIZER beam independently of the GLIDE beam. This mode is used: - on the airfields not provided with glide transmitters
-in the event of very noisy ILS beams (Cat. 1 beams for
example). This mode includes:
-an arming phase,
-
a capture phase,
-
a track phase.
During the arming phase, the HDG, TRK and NAV modes can be used
as support modes.
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Engagement of NAV Mode at Takeoff
Figure 006
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1
Engagement of NAV Mode (HDG TRK Selector Knob)
Figure 007
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1
Engagement of NAV Mode (DIRECT TO)
Figure 008
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1
Horizontal Path Law
Figure 009
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1 1 Feb 01/98
1 1
1CES 1
(b)
Operational use (Ref. Fig. 010) After the LOC frequency and the runway heading have been selected on the MCDU or RMP, arming of the LOC mode is controlled through push action on the LOC pushbutton switch on the FCU. During the arming phase, the support mode must cause the aircraft to follow a path which authorizes capture of the LOC beam. The conditions for activation of the LOC CPT and LOC TRACK modes and the associated guidance are described in 22-13-00. Engagement of the LOC mode armed or active is indicated on the FCU through illumination of the 3 green bars on the pushbutton switch and of the LAT indicator light.
(c)
Operational logic
1 LOC mode armed
_ The LOC mode is armed through action on the LOC pushbutton switch and on condition that:
R - one ILS/MMR receiver is available
-radio altitude is higher than 400 ft, (on the ground with engine stopped, this condition is overridden)
-the active modes are not TAKEOFF or GO AROUND. This mode is disarmed through:
-a new action on the LOC pushbutton switch (does not arm NAV automatically)
-arming of the NAV mode
-engine starting on the ground
-engagement of the go around mode.
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