What happened
On May 7, 2006, at approximately 14:37 local time, a Grob G 109 motor glider and a Cessna 172 N collided in the vicinity of Aschaffenburg airfield. The motor glider had departed from Siegen-Eisenhardt for a cross-country flight to Aschaffenburg, carrying two occupants. Meanwhile, the Cessna 172 N was conducting a training flight from Reichelsheim, carrying a flight instructor, a student, and one passenger.
As the aircraft approached the airfield, the motor glider was traveling on a course of 057° at approximately 70 knots. The Cessna 172 N was executing a landing pattern, having completed its base leg and transitioning to the downwind leg. The collision occurred at an altitude of approximately 1,100 ft MSL. The impact caused the motor glider to enter an uncontrolled spiral dive, crashing into a wooded area, which resulted in two fatalities for the occupants of the motor glider. The Cessna 172 N sustained heavy damage but was able to continue its flight and land safely at Aschaffenburg, with one person slightly injured.
The investigation
The BFU investigation analyzed radar data from Deutsche Flugsicherung, GPS records from the motor glider, and radio communications. Physical examination of the wreckage revealed that the initial contact occurred between the right main landing gear of the Cessna and the left wingtip of the motor glider. Debris from both aircraft was found scattered across a wide area, including parts of the motor glider's horizontal stabilizer and aileron weights.
The investigation also reviewed the flight paths of both aircraft. The motor glider appeared to be intending to intercept the airfield's established traffic pattern, likely cutting across the base leg at an altitude below the prescribed 1,400 ft MSLT. The Cessna was flying a course of approximately 262° on its downwind leg, positioned roughly 500 meters west of the standard pattern.
Findings
- The primary cause of the accident was that the pilots failed to recognize the other aircraft or the impending collision risk in a timely manner.
- Both crews were aware of each other's intention to land at Aschaffenburg, which imposed a duty to monitor airfield traffic to avoid collisions.
- While the motor glider was theoretically detectable by the Cessna crew at a distance of 3,000 meters, and vice versa, the collision occurred before effective evasive action could be taken.
- The flight instructor in the Cessna attempted an evasive climb by pulling back strongly on the control column after spotting the motor glider in the 2 o'clock position, but the impact was unavoidable.