Tail rotor damage during simulated engine failure training at Redhill

Casualties unknown • Redhill Aerodrome, Surrey, GB

An Enstrom F-28C sustained damage to its tail rotor after the collective lever became restricted during a demonstration landing.

What happened

On 3 October 2002, an Enstrom F-28C, registration G-BURI, was conducting a training flight at Redhill Aerodrome in Surrey. The flight, which had been underway for approximately 45 minutes, involved two crew members performing various instructional maneuvers, including practice engine failures while hovering. During the final phase of the flight, the instructor took control to perform a simulated engine-off landing.

As the instructor attempted a run-on landing toward the northwest, the aircraft entered a flare. However, the instructor encountered difficulty raising the collective lever. Consequently, the helicopter touched down in a nose-high attitude with an excessive rate of descent, causing the tail rotor blades, drive shaft, and guard to strike the ground.

The investigation

Following the incident, investigators examined the aircraft's collective lever mechanism. The Enstrom F-28C utilizes a quick-release retaining pin to secure the right collective lever. Examination of G-BURI revealed that the locking lever on this pin could rotate freely in a horizontal plane, which is not typical for this aircraft type.

Investigators found that the plate surrounding the collective lever cutout in the seat floor was distorted at its aft right edge. It was determined that when the locking lever was rotated 180 degrees, it became trapped between the seat floor and this plate. This positioning created a mechanical restriction that prevented the collective lever from being raised easily. As the pilot applied more force to the lever, the distortion of the plate eventually caused an aft bolt to pull away from its underside lock nut, allowing the lever to move fully, though the damage had already occurred.

Findings

  • The primary cause of the landing accident was a mechanical restriction of the collective lever caused by the interference of the retaining pin's locking lever with a distorted floor plate.
  • The retaining pin on G-BURI was found to be bent, and the locating holes in the collective lever had been distorted, allowing the locking lever to rotate freely.
  • The distortion of the floor plate was consistent with the locking lever being caught between the seat floor and the plate during operation.

Probable cause

The aircraft's tail rotor struck the ground because the pilot could not sufficiently raise the collective lever due to mechanical interference between the collective lever's retaining pin and a distorted floor plate.

Frequently asked questions

What happened in the 2002-10-03 ENSTROM F-28C accident near Redhill Aerodrome, Surrey, GB?

An Enstrom F-28C sustained damage to its tail rotor after the collective lever became restricted during a demonstration landing.

What aircraft was involved and where did it happen?

The accident on 2002-10-03 involved a ENSTROM F-28C, registration G-BURI, at Redhill Aerodrome, Surrey, GB.

What was the probable cause of the accident?

The aircraft's tail rotor struck the ground because the pilot could not sufficiently raise the collective lever due to mechanical interference between the collective lever's retaining pin and a distorted floor plate.

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