Ducking under because of the impression of being too high when affected by visual illusions.
Maintain a combination of visual flying supported by monitoring of instruments (including the glide slope deviation during the visual segment of an ILS approach).
Monitor the VASI/PAPI, whenever available; this provides additional visual cues to resist the tendency to increase or decrease the rate of descent.
On runways equipped with an ALSF-II approach lighting system, be aware of the two rows of red lights aligned with the touchdown zone lights as an additional safeguard against “ducking under”.
The following provides a summary of the techniques available to counter visual illusions (and prevent from ducking under):
Maintain instruments scan down to touchdown;
Cross-check instrument indications against outside visual cues to confirm glide path;
Use an ILS approach, whenever available;
If no ILS approach is available, fly a constant-angle non-precision approach (CANPA) supported by the use of the Flight Path Vector / Flight Path Target (Director) or use the FMS FINAL APPR mode (as available);
Use available references and indications such as the ND extended runway centerline, the ILS-DME (or VOR-DME) distance – or the FMS track distance to runway threshold - and the altitude above airfield elevation to confirm the glide path (based on a typically 300 ft-per-nm approach gradient); and,
Use VASI / PAPI, if available, down to runway threshold (only when using a 3-bar VASI or a PAPI).
In summary, the main line-of-defense against visual illusions and disorientation is to use and rely on flight instruments.
Coordination
The defined task sharing ensures a continued monitoring of visual and instrument references, throughout the transition to visual references and thereafter (i.e., during a visual approach or during the visual segment of an instrument approach).
In known or anticipated hazard conditions, the PNF should reinforce his / her monitoring of instrument references and of flight progress, for an effective cross-check and back-up of the PF.
Altitude and excessive-parameter-deviation callouts should be the same for instrument approaches and visual approaches, and should be continued during the visual segment (i.e., including glide slope deviation during an ILS approach or vertical speed deviation during a non-precision approach).
In case of a go-around, specific excessive-parameter-deviation callouts should be considered (as indicated in SOPs).
Summary of Key Points
The following critical keypoints need to be emphasized:
Awareness of weather factors;
Awareness of surrounding terrain and obstacles;
Awareness and assessment of approach hazards (i.e., conditions that may result in visual illusions, such as “black hole”); 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：Flight Operations Briefing Notes Human Performance Visual Il(7)
