What happened
On July 29, 1999, a Stampe SV4C aircraft, registration EI-BAJ, was performing a private flight from Abbeyshrule to Waterford Airport. During the flight, approximately 8 miles northwest of Kilkenny, the engine began to run intermittently before losing power. The pilot attempted to divert to Kilkenny Airfield, but as the engine power continued to fail, the pilot was forced to select a large field for an emergency landing.
Upon touchdown in the field, which contained a tall crop of barley, the aircraft's undercarriage partially collapsed. The aircraft then nosed over and overturned, resulting in extensive damage to the wings, propeller, and fuselage. Despite the significant impact, both occupants escaped the wreckage without injury.
The investigation
The AAIU investigation focused on the cause of the engine power loss and the mechanical condition of the aircraft. Investigators found that the fuel flow rate during testing was only 2 gallons per hour, which is significantly below the required 7.4 gallons per hour. This deficiency was traced to a partial blockage in the fuel pipe leading from the tank to the filter assembly.
During the examination, the blockage cleared itself when the fuel pipe was moved. While the exact substance causing the obstruction could not be identified, investigators noted that excess sealant from a fuel pipe fitting or foreign matter introduced during refueling were potential causes. The investigation also noted that the aircraft's fuel tank lacked a standard drain, making it difficult to check for water accumulation.
Findings
- The engine failure was directly caused by a restriction in the main fuel line.
- The specific material responsible for the blockage was not determined, though it was likely a single object smaller than 8 mm.
- The aircraft's fuel tank contained approximately 0.5 litres of water.
- The flexible flap tube within the fuel tank was 38 years old and in a brittle, degraded condition.
- A poorly brazed joint on the main undercarriage leg may have contributed to the collapse of the gear during the landing.
Safety action
Following the investigation, the AAIU identified several areas for safety improvement regarding the Stampe SV4C:
- Airworthiness authorities should consider issuing a safety notice regarding the inspection of aging fuel tank flap tubes.
- A recommendation was made to facilitate the installation of self-closing water sample drains on fuel tanks for this aircraft type.
- Authorities should consider a safety letter regarding the inspection of the security of fittings at the top of the main undercarriage leg.