What happened
On 7 September 2001, a Piper PA-38-112, registration G-BYMD, was conducting a training flight at Shoreham Airport. The flight proceeded normally during the initial takeoff roll along Runway 25, with a student acting as the handling pilot. However, as the aircraft climbed to an altitude between 100 and 200 feet, the engine began to surge and repeatedly cut out.
Upon noticing the instability, the instructor took control of the aircraft. The instructor attempted several corrective measures, including verifying the fuel pump was active, switching the fuel tank selector, and applying full throttle. When these actions failed to stabilize the engine, the instructor notified Air Traffic Control of an engine failure and identified a suitable field for an emergency landing. The aircraft completed a successful forced landing, and no injuries were sustained by the two crew members, nor was there any damage to the aircraft.
The investigation
Investigators examined the aircraft following the incident and discovered that the engine continued to run at idle RPM after the aircraft had come to a stop. A physical inspection of the fuel system revealed that the retaining nut for the gascolator bowl had failed due to stripped threads.
Findings
- The primary cause of the engine instability was the failure of the gascolator bowl retaining nut.
- The stripped threads allowed air to be drawn into the fuel system, particularly during high power settings, which induced the observed engine surges.
- At idle power, the fuel flow was sufficient to maintain engine operation without the induction of air.
- The instructor noted that the condition of the nut was not detectable during a standard pre-flight visual inspection.
- The aircraft had completed only 13 flight hours since its most recent annual inspection.