What happened
On May 13, 2000, at 10:15 local time, a Grob G-109 (registration EC-DRP) was performing a local pleasure flight from Sabadell Airport in Barcelona. During the pre-flight checks at the holding point for runway 31, the pilot noted that the engine was unable to reach 2,500 R.P.M. at maximum power, despite the propeller pitch being correctly set. Despite this performance deficiency, the pilot proceeded with the takeoff.
During the takeoff roll, the aircraft experienced a slight tailwind of 2 to 3 knots. As the aircraft climbed, it reached an altitude of approximately 200 meters but maintained a high pitch attitude. The pilot attempted to lower the nose to gain airspeed, but the aircraft began to lose altitude once it passed the end of the runway. To avoid an industrial building ahead, the pilot executed a turn to the left; however, one of the wings struck a lamppost, causing the aircraft to crash into a parking area adjacent to the building. The aircraft was destroyed, and the pilot sustained serious injuries, while the passenger remained uninjured.
The investigation
The investigation focused on the engine performance and the accuracy of the pilot's weight and balance calculations. Investigators examined the propeller, a Hoffmann HO-V62 R/L 160BT, which had recently been returned from maintenance. While the aircraft's documentation listed a different propeller model, the manufacturer confirmed the installed model was a compatible evolution of the approved type. The investigation concluded the propeller was not the cause of the low engine RPM.
Crucially, the investigation revealed a significant error in the pilot's weight calculations. The pilot used a zero weight of 580 kg, which matched the flight manual. However, due to previous modifications, the actual zero weight of EC-DRP was 627 kg. This discrepancy meant the aircraft's actual takeoff weight was approximately 831 kg, exceeding the maximum allowable takeoff weight of 825 kg.
Findings
- The primary cause of the accident was the use of an incorrect zero weight in the takeoff weight calculation, resulting in an overweight operation.
- The engine failed to meet the performance standards established in the flight manual, as it could not reach the required 2,750 ± 100 R.P.M. during the power check.
- A tailwind during the takeoff roll acted as a contributing factor to the degraded performance.
- The pilot failed to abort the takeoff despite observing that the engine was not performing within manual specifications.
Safety action
- It is recommended that flight schools and flying clubs implement procedures to ensure that accurate performance data, specifically an updated and verified weight and balance sheet, is always available on board.
- It is recommended that the Directorate General of Civil Aviation develop and distribute guides to general aviation operators specifying which documents must be carried to ensure reliable weight and balance calculations.