Background
On the afternoon of 13 August 1961, the pilot of the Chipmunk was serving as a tow pilot at Spreitenbach airfield. After completing four towing flights, the glider pilots informed him that glider operations were concluded for the day. According to the pilot's statement, he then decided to perform a solo flight for his own pleasure.
The Accident
Instead of using the prescribed takeoff direction (100°), the pilot chose a direction approximately 8–12° less. During the takeoff roll, he aborted the start and collided with a Mucha 100 glider that had landed shortly before. The glider was parked on the grass area where the Chipmunk was taking off. The pilot of the Chipmunk stated that he first saw the glider when the tail of his aircraft came into level flight, clearing his forward view. He then reduced power and braked, but with only about 50 meters remaining, the collision was unavoidable. Witnesses reported that the Chipmunk briefly became airborne (about 2 meters high for 100 meters), then touched down again 70 meters before impact and struck the glider. No persons were injured.
Aircraft Damage
The Mucha 100 glider (registration HB-638) was destroyed, with damage estimated at CHF 8,000. The de Havilland Chipmunk (registration HB-TUC) sustained relatively light damage to its left wing and rear fuselage, estimated at CHF 7,000.
Investigation Findings
The investigation report stated that the collision occurred outside the designated takeoff and landing area. The pilot had not verified that his chosen direction was clear of obstacles or that no other aircraft were approaching. The prescribed takeoff direction at Spreitenbach was 100°, and these regulations were posted visibly on the hangar and well known to local pilots. The pilot's own logbook entries indicated previous incidents: a loss of speed on 15 April 1960 resulting in substantial damage to a Rhönlerche, and a takeoff in the wrong direction at Spreitenbach on 11 June 1961. The pilot was described by an examiner as having "good flying sense" but being "too self-confident." Weather conditions were not a factor; light easterly winds prevailed.
The investigating commission concluded that the pilot intended to taxi the aircraft to the hangar rather than perform a takeoff, based on the short distance to the hangar and the fact that a normal takeoff would have cleared the glider. However, the pilot maintained he intended to take off. Ultimately, the probable causes were determined to be disregard of airfield regulations and pilot inattention.