What happened
On April 29, 1999, a Beriev BE103 prototype, a six-seat twin-engine amphibious aircraft, was conducting a test flight in Straubing, Germany. The purpose of the flight was to perform vibration measurements on the propellers. To facilitate these measurements, a test propeller equipped with strain gauges was installed on the left engine, and the engine governor was specifically adjusted to allow a maximum RPM of 2940.
During the takeoff roll, the pilot taxied to the far end of the 940-meter runway. Video footage showed the engines were stabilized before the takeoff roll began. However, the aircraft required an unusually long takeoff run of approximately 700 meters, far exceeding the expected 300 meters. After rotating at a high angle of attack and gaining only 10 to 15 meters of altitude, the pilot retracted the landing gear. Immediately following this, the aircraft entered a shallow descent with a high angle of attack and banked to the left. The aircraft struck an embankment approximately 600 meters beyond the end of the runway and caught fire. The pilot was killed in the accident, and the aircraft was destroyed.
The investigation
The BFU examined the engines, propellers, and flight data recorder (FDR) to determine the cause of the performance deficiency. Investigation of both Teledyne Continental IO-360 E5 engines revealed no mechanical failures, malfunctions, or issues with the fuel systems or spark plugs. While the propeller blades had broken near the hub, analysis of the right propeller hub showed no malfunction in the adjustment mechanism.
Despite heavy damage from the impact and fire, investigators successfully recovered data from the Russian-made BUR-LK flight data recorder. Analysis of the recorded parameters revealed that during previous successful flights, the pilot had set the power levers to 60 degrees (full throttle). On the day of the accident, however, the pilot initially set the left engine to 35 degrees and the right engine to 37 degrees. This setting provided only enough power for cruise flight, which is insufficient for takeoff. Furthermore, after liftoff, the pilot actually reduced the power further by approximately 3 degrees.
Findings
- The primary cause of the accident was the pilot's attempt to take off with significantly reduced engine power and his failure to abort the takeoff despite the evident lack of acceleration.
- The incorrect power setting resulted from a misinterpretation of the procedures required for the modified propeller governor settings on the left engine. To prevent overspeeding the engine during the specific test configuration, the pilot needed to use the RPM levers to reduce speed after reaching takeoff power, rather than relying solely on the power levers.
- A significant contributing factor was a potential language barrier; the pilot declined the use of an interpreter during pre-flight briefings, which likely prevented him from fully understanding the specific operational requirements for the test flight.