Engine Failure During Simulated Forced Landing in Grob Tutor

Casualties unknown • 3nm northwest of Cosford, Shropshire, GB

A student pilot was forced to perform an emergency landing in a field near RAF Cosford after an engine failure occurred during a simulated engine-out practice.

What happened

On 12 July 2001, a student pilot was conducting a solo training flight in a Grob G115E Tutor, registration G-BYVO, near RAF Cosford. The flight was intended for aerobatic practice and simulated forced landing (PFL) training. During a stall turn maneuver, the pilot noted a change in the engine note, suggesting a loss of power, though the engine initially recovered.

Following this event, the pilot decided to proceed with the planned simulated engine failure. During the descent, the pilot performed engine warm-up and response checks. However, as the pilot attempted a go-around at approximately 800 feet, the engine began spluttering and failed to respond to the throttle. After an unsuccessful attempt to restart the engine, the pilot executed a forced landing in a nearby field. The aircraft landed heavily on rough ground but sustained no damage.

The investigation

Investigators examined the engine and fuel systems to identify the cause of the power loss. The investigation revealed that the fuel injector assembly showed signs of scoring on the idle control valve and a nick on its rim. Additionally, a significant amount of residue from fuel dye was found around the venturi and air diaphragm.

Further inspection of the fuel filters uncovered various types of metallic and non-metallic debris, including steel, aluminium, brass, and plaster. While the manufacturer deemed the amount of contamination insignificant, the presence of debris was noted. The spark plugs were also found to have large electrode gaps and showed characteristics of running a rich fuel mixture. Ground runs following the investigation showed the engine could operate normally under controlled conditions, making it difficult to pinpoint the exact moment of failure.

Findings

  • The engine failure occurred during a period of simulated engine-out practice.
  • Debris in the fuel system had caused scoring on the injector's idle control valve.
  • The engine appeared to have been running with an over-rich mixture, which may have contributed to the engine's instability during the maneuver.
  • The pilot's attempt to restart the engine while the propeller was windmilling was not in accordance with the correct drill and temporarily disabled a magneto.
  • The pilot did not select the fuel mixture to the rich position during the restart attempt, which could have assisted the engine recovery.

Probable cause

The exact cause of the engine failure could not be determined with certainty, but evidence suggests that debris in the fuel system caused scoring on the injector's idle control valve, potentially leading to an over-rich fuel mixture and subsequent engine instability.

Frequently asked questions

What happened in the 2001-07-12 GROB G115E accident near 3nm northwest of Cosford, Shropshire, GB?

A student pilot was forced to perform an emergency landing in a field near RAF Cosford after an engine failure occurred during a simulated engine-out practice.

What aircraft was involved and where did it happen?

The accident on 2001-07-12 involved a GROB G115E, registration G-BYVO, at 3nm northwest of Cosford, Shropshire, GB.

What was the probable cause of the accident?

The exact cause of the engine failure could not be determined with certainty, but evidence suggests that debris in the fuel system caused scoring on the injector's idle control valve, potentially leading to an over-rich fuel mixture and subsequent engine instability.

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