Easyjet airliner plunged 10,000ft

The Boeing 737 had two passengers on board for the test flight

Air accident investigators have revealed how an Easyjet airliner fell 10,000ft in a steep nose dive during a test flight.

The Air Accidents Investigation Branch (AAIB) said the plane lost height at 350 feet a second before the two pilots recovered from the dive at 5,600ft.

There was "confusion between the two pilots", the AAIB added, describing the event as "a serious incident".

The plane was on a test flight over Norfolk at the time of the incident.

At 15,000ft above the Norwich area, the hydraulic systems that help move the plane's rudder, ailerons and elevators were switched off in a routine test. But this caused the plane to dive suddenly.

Emergency call

Although the 43-year-old captain used "considerable force" on his controls he was initially unable to prevent the plane plummeting towards the ground because it had been left out of balance following a previous flight.

As he rolled the aircraft left at more than 90 degrees to try to stabilise it, the AAIB report notes that there was "confusion between the two pilots", with the captain thinking the hydraulic systems had been restored when in fact they were still switched off.

Having made an emergency call to air traffic controllers, the pilots managed to recover from the dive at about 5,600ft.

The test and customer demonstration flight, on 12 January this year, had two passengers on board. After the incident, the flight was abandoned and the pilots took the plane safely back to Southend.

The balance tabs... [were] adjusted in the opposite sense to that identified as necessary AAIB report

The plane had come to the end of its lease and had just undergone maintenance before being handed on to another operator.

The captain had flown the plane the previous month to Southend for maintenance and had carried out tests during that journey.

He found the "amount of manual stabiliser trim wheel adjustment" required to balance the aircraft in level flight was only just within approved limits, and verbally requested that the matter be looked at.

The report said: "The absence of a formal post-flight debrief and formal written record resulted in the balance tabs, attached to the elevators of the aircraft, being adjusted in the opposite sense to that identified as necessary by the [December] flight test.

"The aircraft was therefore significantly out of trim during the post-maintenance test flight and it was that which initiated the pitch-down incident."