Ice theory over plane drama which injured four

A build-up of ice or of de-icing fluid on a Flybe aircraft might have been the cause of an air emergency in which four people were injured last December, according to an official report published today.

But the Air Accident Investigation Branch of the Department of Transport said it had failed to find conclusive reasons for the incident and further investigations would be carried out.

The crew of the aircraft reported an emergency situation after the plane underwent a “severe and unexpected movement” during a flight from Birmingham to Belfast City Airport on December 12.

The UK Low Level Forecast for the route warned of severe icing in freezing rain and moderate icing in cloud, said the report.

When the BAe 146-200 with 36 passengers and five crew pitched and shuddered violently a male flight attendant fell, breaking his leg, a female colleague suffered a broken ankle and a third attendant and a passenger suffered minor head injuries.

The plane landed safely in Belfast after the captain and co-pilot regained control and levelled the aircraft.

The AAIB said initial analysis of data showed symptoms of increased stiffness in the elevator servo tabs in the control system, possibly due to freezing of the tabs to the elevators’ trailing edges.

It said at this time there was insufficient evidence to reach specific conclusions on the cause of the stiffness, but a further investigation would examine the possibility of natural airframe icing, the effects of de-icing fluid residues and the implications of component failures within the pitch control system.

The report revealed that, when the aircraft elevators were disassembled, bearings which should have contained grease were found to contain “a dried, almost powdery residue which provided no lubrication properties”.

It added: “This raises concerns that moisture ingress into the bearing cage void could cause the bearings to seize as the moisture freezes in flight.”

It said it was believed the bearings had been on the aircraft since it was manufactured in 1989.

The plane was put back into service a week after the incident, the airline said today.