Tailplane rotation leads to forced landing of Silence Twister

Casualties unknown • 14 January 2014 Launton, Oxfordshire, GB

A Silence Twister experienced a structural failure during flight near Bicester, resulting in a forced landing and significant airframe damage.

What happened

On 14 January 2014, a Silence Twister, registration G-MRJP, was conducting a private flight near Launton, Oxfordshire. The aircraft was flying at approximately 1,500 ft and 100 kt following recent minor maintenance work. While in flight, the pilot experienced a loud bang, intense vibration, and a sudden yaw and roll to the right.

Recognizing a structural failure, the pilot attempted to return to Bicester Airfield. During handling checks, the pilot determined that maintaining control required continuous full left rudder and a left bank, and that altitude could not be sustained. Consequently, a field was selected for a forced landing. During the landing sequence, the aircraft could not be kept on course and ground looped to the left. The aircraft came to rest in soft mud, resulting in no injuries to the pilot, though the landing gear collapsed and the propeller, wings, and fuselage sustained damage.

Upon exiting the aircraft, the pilot observed that the right-hand tailplane had rotated 90 degrees around its main spar.

The investigation

The investigation focused on the mechanism of the tailplane attachment. The Twister design features demountable tailplanes that slide onto a tubular main spar. To secure the assembly, a wire locking pin is inserted through a plastic guide tube to engage a rigging spigot, preventing lateral movement.

Investigators discovered that the locking pin had failed to engage the spigot. The investigation established that wear within the plastic guide tube had created an unintended exit point for the pin. This allowed the pin to exit the tube before it could properly secure the spigot. Because the tailplane was not laterally locked, it migrated spanwise, which disengaged the hexagonal elevator drive and permitted the tailplane to rotate about the main spar.

Findings

  • The aircraft had recently undergone derigging for maintenance and subsequent reassembly.
  • Wear in the plastic guide tube caused the locking pin to exit the tube prematurely.
  • The locking pin failed to enter the hole in the rigging spigot, leaving the tailplane unlocked.
  • The unlocked tailplane moved spanwise, causing the elevator drive to disengage and the tailplane to rotate.
  • Two independent inspections following the maintenance work failed to identify that the tailplane was not properly secured.

Probable cause

The tailplane rotated during flight because the locking pin failed to engage the rigging spigot due to wear in the plastic guide tube, which allowed the pin to exit the tube before reaching its intended destination.

Frequently asked questions

What happened in the 2014-01-14 Silence Twister accident near 14 January 2014 Launton, Oxfordshire, GB?

A Silence Twister experienced a structural failure during flight near Bicester, resulting in a forced landing and significant airframe damage.

What aircraft was involved and where did it happen?

The accident on 2014-01-14 involved a Silence Twister, registration G-MRJP, at 14 January 2014 Launton, Oxfordshire, GB.

What was the probable cause of the accident?

The tailplane rotated during flight because the locking pin failed to engage the rigging spigot due to wear in the plastic guide tube, which allowed the pin to exit the tube before reaching its intended destination.

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