What happened
On July 28, 2007, a Grumman AA-1B, registration OO-PMS, was conducting a navigation flight from Charleroi Airport. The flight, which included a pilot and one passenger, followed a route toward Middelburg, Netherlands, before beginning a return leg toward Belgium. During the return journey, the aircraft's engine began to sputter as the pilot approached the Whisky checkpoint. Although the pilot attempted to stabilize the engine by adjusting power and the fuel pump, the engine eventually ceased functioning as the aircraft entered the Charleroi airport zone.
Unable to reach the runway, the pilot attempted a glide toward the control tower. The aircraft struck the ground in a construction area just outside the airport perimeter. The aircraft slid for approximately 60 meters before striking an embankment and the perimeter fence, causing the aircraft to rotate 180 degrees. Both occupants exited the aircraft without injuries.
The investigation
Investigators from the AAIU(Be) examined the wreckage and the aircraft's maintenance history. The engine was tested the following day, and it started normally using the left fuel tank. However, post-accident measurements revealed that while the left tank contained 7.3 USG of fuel, the right tank was completely empty.
Technical analysis focused on fuel management and the aircraft's performance charts. The investigation looked into the accuracy of the fuel consumption tables provided in the flight manual, the visibility of the fuel gauges, and the pilot's execution of emergency checklists. The investigation also noted that the aircraft's RPM indicator, which is critical for determining fuel flow, was not subject to regular accuracy checks under the existing maintenance program.
Findings
- The engine shutdown was caused by fuel starvation resulting from a combination of factors.
- The flight duration exceeded the original flight plan.
- The pilot's actual fuel tank switching sequence deviated from the intended plan.
- The aircraft's fuel consumption was higher than calculated because the pilot used a 'full rich' mixture setting as instructed for low-altitude flight.
- Monitoring fuel levels was extremely difficult because the fuel gauges were obscured by the presence of a passenger.
- The pilot did not complete all steps of the emergency checklist due to the high sink rate of the aircraft during the glide.