What happened
On 21 July 2014, a Piper PA-28R-20T, registration G-BEOH, was performing a private flight from Gloucester to Cherbourg. The aircraft, carrying one pilot and two passengers, departed from Gloucestershire Airport under fine and calm weather conditions. The takeoff mass was recorded at 2,83 to 2,836 lb, which was within the maximum allowable limits.
After successfully lifting off and retracting the landing gear, the pilot attempted to reduce the engine power from takeoff settings to a climb setting. During this transition, the pilot experienced a significant and unexpected drop in engine power, causing the aircraft to sink. In an attempt to maintain altitude, the pilot applied full power, which caused a brief turbo overboost.
As the aircraft continued its flight path, it approached the edge of a golf course approximately 550 m from the runway end. The aircraft struck treetops in two separate locations. During the incident, the pilot switched the fuel tank selector to the alternative tank, after which the engine power began to recover. Following the second tree strike, the aircraft gained sufficient altitude to rejoin the visual circuit and landed safely without further issues. There were no fatalities or injuries.
The investigation
The investigation involved a review of the pilot's report, the airport operator's findings, and a technical examination by the aircraft's maintenance organisation. Air Traffic Control observed a sluggish takeoff roll and noted the aircraft's slow climb before it disappeared behind trees.
Technical inspectors focused their attention on the fuel gascolator. While the unit appeared correctly installed and showed no external leaks when static, investigators discovered that the gascolator bowl could rock fore and aft. When this movement occurred, fuel leaked freely down the outside of the bowl, revealing a compromised seal.
Findings
- The upper housing of the gascolator was found to be distorted, likely due to long-term pressure from the bail wire assembly.
- This distortion prevented the square section seal from sitting flat, creating an uneven sealing surface.
- Air was ingested into the fuel system due to the combination of the distorted housing, engine vibrations during takeoff, and high fuel flow requirements.
- This air ingestion led to intermittent fuel starvation, which the pilot attempted to rectify by switching fuel tanks.
- Standard power checks at 2,000 rpm prior to departure would not have revealed the issue, as the fuel flow at that lower setting was insufficient to trigger the leak.