Grob G109 crashes after takeoff attempt with incorrect propeller pitch

Casualties unknown • Husbands Bosworth, Leicester, GB

A private flight involving a Grob G109 resulted in extensive aircraft damage after the propeller was left in coarse pitch during takeoff from Husbands Bosworth.

What happened

On 28 May 2021, a Grob G109, registration G-CLIA, was attempting a takeoff from Husands Bosworth Airfield with one pilot and one passenger. During the takeoff roll, the pilot noticed sluggish acceleration and announced an intention to abort the maneuver. However, the passenger, a qualified instructor, took control of the aircraft.

The aircraft became airborne but failed to climb, reaching a maximum altitude of only 100 ft agl before descending. While attempting to steer the aircraft toward a nearby field, the right wing struck a tree. This impact caused the aircraft to rotate 180 degrees and pitch downward, resulting in a nose-down impact with the ground. The impact caused extensive damage, including a broken fuselage and wing, but no injuries were sustained by the two occupants.

The investigation

Investigators examined the propeller and hub, finding evidence that the propeller was in coarse pitch at the moment of impact. Analysis of the aircraft's performance revealed that the takeoff roll exceeded 900 m, significantly higher than the expected distance for a takeoff on grass.

The investigation established that the pilot had omitted the final engine power check, which would have confirmed the propeller was in the required fine pitch setting. This omission was likely driven by the presence of a glider on final approach, which prompted the crew to commence the takeoff without delay to avoid interfering with the other aircraft.

Findings

  • The takeoff was attempted with the propeller in coarse pitch, which severely restricted engine performance.
  • The pilot failed to perform the final power check, which was the last opportunity to identify the incorrect pitch setting.
  • The pilot in command's decision to abort the takeoff was not effectively communicated to or acted upon by the passenger.
  • There had been no prior discussion between the occupants regarding roles and responsibilities in the event of an emergency.
  • A recent reduction in the maximum RPM margin may have made the incorrect pitch setting harder to detect visually.

Probable cause

The accident was caused by the propeller being left in coarse pitch for takeoff, which resulted in insufficient climb performance. This error went undetected because the pilot omitted the final power check, likely to avoid obstructing a glider on final approach.

Frequently asked questions

What happened in the 2021-05-28 Grob G109 accident near Husbands Bosworth, Leicester, GB?

A private flight involving a Grob G109 resulted in extensive aircraft damage after the propeller was left in coarse pitch during takeoff from Husbands Bosworth.

What aircraft was involved and where did it happen?

The accident on 2021-05-28 involved a Grob G109, registration G-CLIA, at Husbands Bosworth, Leicester, GB.

What was the probable cause of the accident?

The accident was caused by the propeller being left in coarse pitch for takeoff, which resulted in insufficient climb performance. This error went undetected because the pilot omitted the final power check, likely to avoid obstructing a glider on final approach.

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