Aileron Jamming Incident Involves BAe 146 in Swedish Airspace

Casualties unknown • Incident Involving Aircraft SE-DRG, in Controlled Airspace West of Stockholm, SE

A flight crew successfully managed a serious flight control malfunction after a loose aileron cover plate caused mechanical jamming during takeoff.

What happened

On 13 January 1997, a BAe 146 Series 200, registration SE-DRG, departed from Stockholm/Bromma airport for a scheduled flight to Göteborg/Landvetter. Shortly after takeoff, while climbing through approximately 1,300 feet in darkness, the aircraft entered a left turn. As the copilot attempted to level the wings, the right control wheel became restricted, moving only 10 to 20 degrees from its neutral position.

The captain verified the control jam and took decisive action by applying significant force to the left control wheel, which successfully disconnected the left aileron control system from the right. This allowed the crew to maintain roll control using large inputs on the left side of the cockpit. Due to the degraded maneuverability and challenging weather conditions, the crew declared an emergency and diverted to Norrköping/Kungsängen. The aircraft landed safely without injuries to the 38 passengers or the 2 crew members.

The investigation

SHK investigators examined the aircraft's aileron control systems and identified two distinct technical issues. First, they discovered that the chain in the right control column assembly was slack, which allowed a bolt head to strike the upper edge of an inspection hole, causing mechanical interference.

However, because a similar jamming sensation occurred during a subsequent test flight after the chain issue had been addressed, investigators focused on the right aileron itself. Further inspection revealed that a top cover plate over the center hinge of the right aileron was loose because the fixing screws had not been fully tightened. Under aerodynamic loads during flight, the forward edge of this plate lifted and caught against the trailing edge of the wing skin, physically preventing the upward movement of the aileron.

Findings

  • The crew performed their duties in a professional and exemplary manner.
  • The aircraft was airworthy and had been maintained according to existing regulations.
  • A loose cover plate on the right aileron caused the control jam by catching against the wing skin.
  • The specific technical faults were previously unknown to both the airline and the manufacturer.
  • Existing maintenance manuals did not include instructions for checking the play of these cover plates or the tension of the control column chains.

Probable cause

The incident was caused by a loose aileron cover plate that, under aerodynamic pressure, moved into the path of the wing skin, thereby jamming the upward movement of the aileron control.

Frequently asked questions

What happened in the 1997-01-13 aircraft accident near Incident Involving Aircraft SE-DRG, in Controlled Airspace West of Stockholm, SE?

A flight crew successfully managed a serious flight control malfunction after a loose aileron cover plate caused mechanical jamming during takeoff.

What aircraft was involved and where did it happen?

The accident on 1997-01-13 involved a aircraft, registration SE-DRG, at Incident Involving Aircraft SE-DRG, in Controlled Airspace West of Stockholm, SE.

What was the probable cause of the accident?

The incident was caused by a loose aileron cover plate that, under aerodynamic pressure, moved into the path of the wing skin, thereby jamming the upward movement of the aileron control.

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