Pilot forced to parachute from glider after control connection failure

Casualties unknown • Gibett Hill, Brentor, near Tavistock, Devon, GB

A pilot was forced to abandon a Grob G102 Astir CS via parachute after a control connection disconnected during a private flight in Devon.

What happened

On 23 June 2021, a Grob G102 Astir CS glider, registration G-CJSK, was conducting a private soaring flight near Brentor, Devon. After being launched via winch from Brentora Airfield, the pilot climbed to 4,100 ft. Approximately 50 minutes into the flight, the pilot heard a metallic noise and noticed a loss of responsiveness in the ailerons. Specifically, the right aileron ceased responding to inputs, and the pilot had to use left aileron input to maintain level flight.

As the aircraft encountered sinking air and the airspeed reached 55 kt, the wings began to flutter. The pilot found that increasing speed caused significant airframe shaking. Determining that the aircraft could not be safely landed, the pilot jettisoned the canopy and exited the aircraft using a parachute at an altitude between 1,500 and 2,000 ft. The pilot sustained minor injuries during the parachute landing.

The investigation

The investigation focused on the mechanical failure of the control surfaces. Examination of the wreckage revealed that the right aileron control connection within the fuselage had become disconnected. The right aileron pushrod was found projecting from the fuselage, having pierced the skin upon impact with the ground.

Investigators examined the L’Hotellier type control connection, which utilized a ball and socket mechanism. This specific aircraft was equipped with Wedekind sleeves as a secondary locking device. The British Gliding Association (BGA) conducted testing which revealed that this type of connection can be partially assembled in a way that appears secure during a standard positive control check but fails under load.

Findings

  • The right aileron L’Hotellier control connection became disconnected during flight, likely triggered by turbulence.
  • The control connection was improperly assembled, such that the ball was only partially engaged in the socket.
  • The presence of the Wedekind sleeve prevented the lock plate from returning to its fully locked position, yet the connection was able to pass a standard positive control check.
  • The internal location of the connections within the fuselage made visual verification of the security of the mechanism difficult.

Probable cause

The primary cause of the accident was the disconnection of the right aileron control connection in flight, which occurred because the L’Hotellier fitting was improperly assembled in a manner that allowed it to pass a routine control check while remaining insecure.

Frequently asked questions

What happened in the 2021-06-23 Grob G102 Astir CS accident near Gibett Hill, Brentor, near Tavistock, Devon, GB?

A pilot was forced to abandon a Grob G102 Astir CS via parachute after a control connection disconnected during a private flight in Devon.

What aircraft was involved and where did it happen?

The accident on 2021-06-23 involved a Grob G102 Astir CS, registration G-CJSK , at Gibett Hill, Brentor, near Tavistock, Devon, GB.

What was the probable cause of the accident?

The primary cause of the accident was the disconnection of the right aileron control connection in flight, which occurred because the L’Hotellier fitting was improperly assembled in a manner that allowed it to pass a routine control check while remaining insecure.

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