Chapter-4 DECISION HEIGHT AND VISUAL REFERENCES Page-22
CAT II – DH 100ft & RVR 300M
Chapter-4 DECISION HEIGHT AND VISUAL REFERENCES Page-23
(CAT III A – DH 50 ft & RVR 175M)
Chapter-4 DECISION HEIGHT AND VISUAL REFERENCES Page-24
4.5 Visual Reference for CAT III Ops with DH
For CAT IIIA/IIIB operations with DH, the condition required at DH is that there should be visual references (Runway touchdown zone lighting or marking) which confirm that the aircraft is over the touchdown zone of the runway and that a landing may safely be carried out and for fail-operational Category III operations without DH, there is no requirement for visual references for landing. However, minima established to ensure safety during roll-out.
The visual references required at DH in CAT II operations to continue the approach is not less then 3 light segment of the centre line of the approach lights or runway centre line or touchdown zone lights or runway edge lights:
For CAT III B the visual reference must contain at least one centerline light. It is generally accepted that visual segment requires is 60 m. for CAT-IIIA Ops. Go around is mandatory if the visual references do not confirm this requirement.
4.6 Visual Reference for CAT III Ops without DH
For this category of operation, the decision to continue does not depend on visual references, even though a minimum RVR is specified. The decision depends only on the operational status of the aircraft and ground equipment. If a failure occurs prior to reaching the AH, a go-around will be made. A go around must nevertheless be performed if the Auto land warning is triggered.
The ‘sufficient time’ for pilot’s assessment mentioned above is considered to be about 3 seconds above DH.
4.7 Loss of Visual References
A. Operations with DH- before touchdown
If the decision to continue has been made and the visual references subsequently become insufficient (for the appropriate category), or the flight path deviates unacceptably, a go-around must be initiated (a go around is initiated below the MABH, whether auto or manual, may result in ground contact).
NOTE: If the touchdown occurs after GA is engaged the AP remains engaged in that mode, and ATHR remains in TOGA, ground spoilers and auto-brake are inhibited.
B. Operations with and without DH-after touchdown If the visual references are lost after touchdown, a go-around should not be attempted. The roll-out should be continued with AP in ROLL-OUT mode down to taxi speed.
4.8 Cockpit Cut-off Angle The angle made by the direction of aircraft nose with fore and aft axis, with pilot’s eye correctly positioned, is called the Cockpit Cut-off Angle. This is 20 degrees for A319/ A320/ A321/ A330 a/c. With a 4 deg. Pitch angle on final approach, the earliest point visible will be 16 degrees below horizon. The approximate distance from aircraft’s position blocked by nose and the SVR required are as follows;
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