When using external references, the available visual cues must allow the pilot to assess the pitch attitude and bank angle, the lateral position and heading, the horizontal flight path (track) and vertical flight path (flight path angle).
After adequate visual references have been acquired, to allow descending below the MDA(H) or below the DA(H), the different elements of the approach light system provide visual cues for:
.
Assessing the aircraft position, drift angle and distance to the touchdown zone; and,
.
Perceiving any rate of change during the final phase of the approach.
Acquisition of Visual References
The task sharing for acquisition of visual references and for monitoring the flight path and aircraft systems varies depending on :
.
The type of approach (i.e., criticality of time available for acquiring the visual references); and,
.
The level of automation being used :
. hand flying ( using FD );
or,
. AP engaged (i.e. AP monitoring - single AP or dual AP approach).
The formal announcement of visual references should be limited to the runway or runway/airport environment (although announcing the view of the ground may be considered).
Non-precision and CAT I ILS approaches :
Non-precision approaches and CAT I ILS approaches can be flown manually following the FD orders or instruments raw data or with AP engaged.
Acquisition of Visual References
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The PF is engaged directly in either:
.
Hand-flying the airplane and following the FD orders while monitoring instruments and navaids raw data,
or,
.
Supervising the autopilot operation, being ready to take over if required.
The PNF therefore is responsible for progressively acquiring and announcing the visual references while monitoring the flight progress and backing-up the PF.
The PNF scans alternatively inside and outside, announces flight-parameter deviations and announces:
.
“Visual“ (or whatever visual reference is in sight), if adequate visual references are available; or,
.
“One hundred above” then “Minimum“ (if no radio-altimeter autocallout is available), if adequate visual references are not available.
Note :
The PNF should not lean forward while attempting
to acquire visual references.
If the PNF calls “Visual” while leaning forward, the PF might not have visual references yet, because of his/her different viewing angle (cockpit cutoff angle).
The PF confirms the acquisition of visual references and announces “ Landing “ ( or “ Go Around “, if visual references are not adequate ).
For landing, the PF progressively transitions from instrument flying to external visual references.
CAT II / CAT III ILS approaches :
CAT II / CAT III ILS approaches are flown making use of the automatic landing system.
CAT II automatic approaches can be followed by a manual landing (although the standard operating procedure is to use the autoland capability).
In CAT III weather conditions, automatic landing usually is mandatory.
Consequently, the terms “visual references” do not have the same meaning for CAT II and CAT III approaches.
For CAT II approaches, having visual references means being able to see to land (i.e., being able to land manually).
For CAT III approaches, having visual references means being able to see to verify the aircraft position.
The U.S. FAR 91.189 and the European JAR-OPS
1.430 account for this interpretation in defining the minimum visual cues that must be available at the DA(RA DH).
For CAT III with No DH, no visual cue is specified but it is a recommended practice for the PF to look for visual references before touchdown; these visual cues are later used for monitoring the AP guidance during the rollout phase.
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