Runway Visual Perspective
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Correctly judging the required angle of approach to a landing runway when using only direct visual reference, with no external slope indication such as Visual Approach Slope Indicator Systems or Visual Approach Slope Indicator Systems and with no Instrument Landing System (ILS) GS display or non-precision approach plate to refer to, can be challenging when not carried out regularly. The difficulty may be greater at night because visual cues may be restricted to lit objects and runway lighting systems.
The Runway Visual Perspective may give rise to a visual illusion that may result in landing short of the runway, hard landing or runway overrun, but may also cause spatial disorientation and loss of control.
The errors related to wrong angle of approach based on visual cues occur more often during the hours of darkness. Contributory factors are specifics of the terrain, airport environment (e.g. absence of lights creating 'black hole effect') and weather conditions. Some common scenarios include:
- Perception that the aircraft is too high - The pilot of an aircraft approaching a very long runway gains the impression that the aircraft is high on the approach and descends dangerously close to the ground;
- Runway slope and mis-perception of the aircraft position based on visual reference The pilot of an aircraft approaching a runway with a pronounced up-slope gains the impression that the aircraft is high on the approach and descends dangerously close to the ground;
- Mis-identification of the runway: The pilot sees a row of street lights and mistakenly lines up on them instead of the runway (see also Wrong Runway Use);
Visual Illusions Awareness
The Airbus Flight Operations Briefing Note (FOBN) - Visual Illusions Awareness provides a more detailed description of the problems, aided by clear diagrams, and providing more detail on the defences to adopt.
Other relevant sources of information from the Flight Safety Foundation ALAR Toolkit are listed below under Further Reading.
Accidents & Incidents
- AS65, vicinity North Morecambe Platform Irish Sea UK, 2006
- B732, London Gatwick UK, 1993
- B737, vicinity Branson MO USA, 2014
- B752, Newark NJ USA, 2006
- B763, Atlanta GA, USA 2009
- Flying a Visual Approach
- Night Visual Approaches
- Visual Illusions
- Runway Excursion
- Stabilised Approach
- OGHFA Spatial Disorientation Situational Example
Flight Safety Foundation