Inadvertent trim application investigated in Shoreham gyrocopter accident

Casualties unknown • Shoreham Airport, West Sussex, GB

An investigation into the accident involving a Rotorsport UK Calidus at Shoreham Airport examined whether accidental activation of the nose-up trim system contributed to an over-rotation during takeoff.

What happened

On 29 September 2012, a Rotorsport UK Calidus, registration G-ETOJ, was involved in an accident during takeoff from Shoreham Airport, West Sussex. During the initial stages of the takeoff roll, the aircraft experienced an apparent over-rotation. The pilot reported that there were anecdotal accounts of the nose-up trim being accidentally engaged when the control stick was moved fully aft at the start of the takeoff run. It was suggested that this could occur if the top of the control stick made contact with the seat harness buckle, a possibility particularly relevant to pilots of larger build.

The investigation

The AAIB examined the aircraft's two-axis electro-pneumatic trim system. This system utilizes an electrical pneumatic motor to build pressure in pitch and roll cylinders attached to the flight controls. The pilot uses buttons located on the top of the control column to manage the trim. When the aft button is pressed, a valve opens, allowing the motor to build pressure for nose-up trim. This pressure is monitored via a gauge on the instrument panel, and the forward button is used to release air and reduce nose-up trim.

During the investigation, the AAIB consulted a gyroplane flying expert with experience operating the Rotorsport UK Calidus. This expert confirmed that accidental trim application had occurred to them on approximately six occasions, though without resulting in an incident. The investigation also noted that while the trim system does not provide additional pitch authority when the stick is already fully back, the accidental application of nose-up trim could still impact the aircraft's rotation.

Findings

  • The Rotorsport UK Calidus featured an electro-pneumatic trim system operated by buttons on the control stick.
  • There was a possibility that the nose-up trim could be accidentally activated if the top of the stick struck the seat harness buckle during full aft stick application.
  • An aviation authority expert confirmed that inadvertent trim activation is a known occurrence in this aircraft type.

Probable cause

The investigation considered that the accidental activation of the nose-up trim system, potentially caused by the control stick making contact with the seat harness buckle, may have contributed to the over-rotation of the aircraft during takeoff.

Frequently asked questions

What happened in the 2012-09-29 Rotorsport UK Calidus accident near Shoreham Airport, West Sussex, GB?

An investigation into the accident involving a Rotorsport UK Calidus at Shoreham Airport examined whether accidental activation of the nose-up trim system contributed to an over-rotation during takeoff.

What aircraft was involved and where did it happen?

The accident on 2012-09-29 involved a Rotorsport UK Calidus, registration G-ETOJ, at Shoreham Airport, West Sussex, GB.

What was the probable cause of the accident?

The investigation considered that the accidental activation of the nose-up trim system, potentially caused by the control stick making contact with the seat harness buckle, may have contributed to the over-rotation of the aircraft during takeoff.

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