What happened
On July 17, 2001, at 10:42 AM, an Avions Mudry CAP 10B departed from Trier-Föhren (EDRT) for an aerobatic training flight. The aircraft was occupied by a flight instructor and a student pilot performing maneuvers within a designated training airspace.
During the flight, the crew performed several aerobatic figures, including a loop and an Immelmann turn. Video evidence captured by a witness showed that after a period of straight flight, the aircraft entered a pull-out maneuver. As the longitudinal axis exceeded 20 degrees relative to the horizon, the right wing structure collapsed upward. The right wing disintegrated, leaving only fragments attached to the fuselage. The remaining portion of the aircraft—consisting of the fuselage, left wing, and tail—entered a violent right-hand spiral dive, following a parabolic trajectory until it impacted the ground near Thalfende. The impact resulted in two fatalities.
The investigation
The BFU analyzed radar data from several stations and reconstructed the flight path using video footage. The investigation focused on the wreckage, which was scattered across a forested area. Investigators recovered the engine, instruments, and a G-meter, which recorded peak accelerations of +8.5 and -5.2 G.
Laboratory analysis of the right wing spar was conducted by the Fraunhofer Institute for Wood Research. The investigation examined the manufacturing quality of the wooden components, the maintenance history of the aircraft, and the flight parameters during the maneuver. The BFU also reviewed the pilot's experience and the aircraft's structural design limits.
Findings
Technical analysis revealed that the structural failure was caused by reduced strength in the wing spar due to manufacturing defects. Specifically, the wooden laminates used in the lower spar flange contained significant fiber deviations. These defects led to the development of compression failures (crushing) within the wood layers.
While the aircraft was operating within its permitted maneuver speeds and load factors, the compromised integrity of the spar meant the structure could no as effectively withstand the loads encountered during the pull-out maneuver. The investigation concluded that these internal defects were not detectable during standard prescribed inspections, as the damage was located in areas difficult to access from the fuselage.