Investigators have attributed to unconscious action two incidents, on the same day, in which EasyJet pilots activated flap retraction after take-off instead of raising the landing-gear.
The more significant of the two events occurred on 16 February as an Airbus A319 (G-EZFA) departed Bristol.
After the captain requested retraction of the landing-gear, at a height of 46ft, the first officer moved the flap lever from its take-off setting to the fully-retracted position.
The flap lever is situated behind the engine thrust levers on the A319, while the landing-gear selector is on the front instrument panel, to the right of the central display screens.
Investigators noted that, during the take-off roll, the first officer had placed his hand behind the thrust levers to suppress a rattling noise from the centre console.
At the point when the flap lever was moved the aircraft was flying at 158kt, just 3kt above the calculated stall speed with clean slats and flaps.
The captain did not initially realise that the flaps were retracting but noticed sudden changes to thresholds on the airspeed scale.
Seven seconds after the flap lever was moved, the captain lowered the nose from 15° to 8° and activated take-off/go-around thrust.
Although the aircraft accelerated, the loss of lift from the fully-retracted flaps caused it to start descending at about 440ft. The descent rate reached 1,300ft/min and, just below 400ft, the ground-proximity warning system issued a ‘don’t sink’ alert.
The A319’s height declined to 378ft before the descent was contained and the aircraft began to climb away.
EasyJet classified the incident as an “action slip”, an inadvertent mistake while carrying out a series of steps which are largely routine and unconscious, says the UK’s Air Accidents Investigation Branch.
It points out that distraction – such as that resulting from the console rattle on take-off – can make pilots “vulnerable” to such errors.
“The crew did not fully appreciate what had happened until after [take-off/go-around thrust] had been selected and, by the time they considered re-selecting flap, the aircraft was recovering to climbing flight,” the inquiry adds.
Investigators have disclosed that a similar event had taken place just 7h earlier, involving an EasyJet Airbus A320 (G-EZTZ) departing from Amsterdam.
The captain, who was the monitoring pilot, fully retracted the flap lever after a gear-up request.
But in contrast to the Bristol incident, the captain immediately realised the error and re-selected the proper flap setting, while informing the flying pilot of the situation. The flying pilot reduced the nose attitude and maintained positive climb.