Tail rotor drive failure leads to helicopter accident at Leicester Airport

Casualties unknown • Leicester Airport, GB

A Robinson R22 Beta experienced a sudden loss of tail rotor effectiveness during an instructional flight, resulting in a heavy landing and aircraft rollover.

What happened

On 14 August 2012, a Robinson R2/2 Beta, registration G-BTHI, was conducting a training flight at Leicester Airport. While on final approach to Runway 24 at an altitude of approximately 150 to 200 feet, the aircraft experienced intense vibrations throughout the airframe and controls. During this period, a clutch warning light illuminated, followed quickly by low rotor RPM warnings and an audible warning horn.

While the pilot was transmitting a MAYDAY call, the aircraft's stability was compromised. The pilot initiated an autorotation procedure; however, the helicopter exhibited an unexpected right-hand yaw. Despite the application of full left pedal, the aircraft continued to yaw to the right. To avoid a public road located in the aircraft's flight path, the pilot used the cyclic control to increase the turn rate. The helicopter ultimately made a heavy landing in a field with minimal forward velocity, subsequently rolling onto its left side. The two crew members sustained minor injuries.

The investigation

Investigators examined the wreckage and identified significant mechanical failures within the tail rotor drive system. A large amount of wiring, which likely provided power to the anti-collision light, was found entangled around the tail rotor drive shaft.

Technical inspections revealed that the drive shaft damper assembly, located inside the tail boom, had detached from its mounting bracket. Furthermore, the investigation established that the tail rotor drive had failed at the intermediate flex plate coupling, situated just behind the clutch actuator. The investigators were unable to confirm if the initial failure was the separation of the damper assembly or a failure at the flex plate coupling.

Findings

  • The tail rotor drive system suffered a mechanical failure at the intermediate flex plate coupling.
  • The drive shaft damper assembly had broken away from its bracket.
  • The failure of the tail rotor drive caused an uncontrollable right-hand yaw that could not be corrected with left pedal input.
  • The clutch fuse was discovered to have been displaced from its housing.

Probable cause

The accident was caused by a failure in the tail rotor drive system, specifically at the intermediate flex plate coupling, which resulted in a loss of tail rotor effectiveness and subsequent uncommanded yaw during approach.

Frequently asked questions

What happened in the 2012-08-14 Robinson R22 Beta accident near Leicester Airport, GB?

A Robinson R22 Beta experienced a sudden loss of tail rotor effectiveness during an instructional flight, resulting in a heavy landing and aircraft rollover.

What aircraft was involved and where did it happen?

The accident on 2012-08-14 involved a Robinson R22 Beta, registration G-BTHI, at Leicester Airport, GB.

What was the probable cause of the accident?

The accident was caused by a failure in the tail rotor drive system, specifically at the intermediate flex plate coupling, which resulted in a loss of tail rotor effectiveness and subsequent uncommanded yaw during approach.

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