Runway Misalignment

Description

Runway misalignment is a situation where a crew fails to position their aircraft on the runway centreline prior to commencing a take off. While it is possible to successfully complete the roll, the situation sometimes results in a Rejected Take Off or a Runway Excursion. Also, even in the case of aircraft becoming airborne, it is not uncommon to either receive damage to the aircraft or to cause damage to ground equipment (most often to the runway edge lights).

Contributory Factors

The following is an (non-exhaustive) list of factors that may contribute to aircraft misalignment. Normally any of these, on its own, would not be sufficient to cause enough degradation of the crew Situational Awareness. When several of them are combined however, the risk increases. The factors may roughly be combined into three groups:

  • Environmental factors. These include weather phenomena (e.g. time of day, precipitation, etc.) and features the physical environment (e.g. aerodrome lights) which affect the flight crew situational awareness. The most common of these are:
    • Nighttime. When pilots taxi and take off during daylight conditions, they normally have a wide range of visual cues by which they can navigate and verify their location. At night however, the amount of visual information available is markedly reduced.
    • Poor visibility/vision or bad weather (rain) reduces the amount of visual cues available.
    • Wide runway/extra pavement near taxiway. Seeing tarmac on both sides of the lights may cause the crew to interpret their position as being on the centreline.

An example of a runway having extra pavement
    • Displaced threshold (lights and markings start further down the runway). In these cases the pilots will not be able to see the normal threshold markings, such as the runway number or 'piano keys', which provide important cues during the line up phase of flight.
    • Lack of runway centreline lights.
    • Same colour used for runway edge and runway centreline lights. While at some point the edge lights change to yellow and the centreline lights to red-white and finally red only, at lineup the colour is white for both. Note: this is an ICAO standard.
    • Recessed runway edge lights. Centreline lighting, when present, is always recessed in order to allow aircraft to safely travel over the centreline during takeoff. Therefore, if the edge lighting is also recessed, then the crew may mistake it for a centreline lighting. If the lights are not recessed, they are normally raised (and frangible) and this may facilitate distinction.

The picture on the left shows a line of raised runway edge lights and the picture on the left shows a recessed runway centreline light
  • Human factors. As with most occurrences, these are often cited as contributors. Their effect is normally not recognized until it is too late. Examples of these are:
    • Flight crew divided attention/distraction/eyes inside (including due to workload and lack of familiarity with runway or airport).
    • Fatigue increases the risk of human error.
  • Operational factors. Unlike the other two groups, these are conscious choices normally aimed at expediting traffic, e.g.:
    • Issuing air traffic control clearance when taxiing or entering runway may distract the flight crew or increase their workload ultimately resulting in reduced situational awareness. This risk is often mitigated by imposing procedures on the timing of ATC clearances. For example, controllers may be required to issue clearances before the aircraft has commenced taxi or to ask the flight crew to report when ready to receive it.
    • Immediate Тakeoff Clearances reduce the the crew’s time for conducting a thorough outside visual check and verifying runway alignment before initiating the take off roll.
    • Intersection departures. The effect is similar to the displaced threshold mentioned above the difference being that intersection departures are used for operational reasons.

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