Pilot Equipment Interface

Pilot Equipment Interface


Level busts are often the result of break-down of the pilot-equipment interface; that is to say, the incorrect handling or interpretation of aircraft equipment by the pilot. There are usually two elements to this:

  • The pilot makes an incorrect setting or performs an inappropriate action on the equipment; and,
  • The error is not noticed or not corrected by other flight-crew members.

Typical Scenarios

  • Altimeter Setting Procedures. The pilots set an incorrect or inappropriate pressure setting on the altimeter barometric sub-scale;
  • Use of the Altitude Alerter. The pilots inadvertently select the wrong altitude or flight level on the altitude alerter;
  • Use of the Autopilot.
    • The pilot enters an incorrect target altitude on the Flight Guidance System and fails to confirm the entered target on the Primary Flight Display and/or the Navigation Display;
    • The pilot inadvertently arms a selected mode or selects an incorrect mode;
    • The pilots become pre-occupied with the automatic systems resulting in loss of situational awareness;

See also Aircraft Technical Equipment.

Contributory Factors


A&I Examples

On 11 September 2010, a DHC8-400 being operated by Flybe on a scheduled passenger flight from Bergerac France to Exeter failed to level as cleared during the approach at destination in day VMC and continued a premature descent without the awareness of either pilot due to distraction following a minor system malfunction until an EGPWS  PULL UP Hard Warning occurred following which a recovery climb was initiated. There were no abrupt manoeuvres and no injuries to any of the 53 occupants.

On 7 February 2011 two Air Inuit DHC8s came into head-to-head conflict en route over the eastern shoreline of Hudson Bay in non radar Class  A airspace when one of them deviated from its cleared level towards the other which had been assigned the level 1000 feet below. The subsequent investigation found that an inappropriate FD mode had been used to maintain the assigned level of the deviating aircraft and noted deficiencies at the Operator in both TCAS pilot training and aircraft defect reporting as well as a variation in altitude alerting systems fitted to aircraft in the DHC8 fleet.

On 9 December 2016, a Bombardier DHC8-400 departing Sydney lost prescribed separation against an inbound Boeing 777-200 after its crew failed to ensure that the aircraft levelled as cleared at 5,000 feet and this was exceeded by 600 feet. The Investigation found that the First Officer, as Pilot Flying, had disconnected the autopilot prior to routinely changing the selected airspeed because it tended to disconnect when this was done with altitude capture mode active but had then failed to re-engage it. The Captain's lack of effective monitoring was attributed to distraction as he sought to visually acquire the conflicting traffic.

Further Reading

EUROCONTROL Level Bust Toolkit


SKYbrary Partners:

Safety knowledge contributed by: