Summary
On 11 April 1967 at approximately 1300 MEZ, a Grunau-Baby glider, registration HB-188, sustained substantial damage while attempting to land at Birrfeld airfield. The pilot suffered a lumbar vertebra contusion.
Investigation
The glider, owned and operated by the Akademische Segelfluggruppe Zürich, had a valid airworthiness certificate and no evidence of pre-impact defects was found. The pilot, born 1938, held a valid glider pilot license issued on 9 August 1966, with a total flight experience of approximately 21 hours in 105 flights, including about 6 hours in 21 flights since receiving the license.
Weather conditions were sunny with cumulus clouds and light winds. The accident occurred in the approach sector of runway 26, about 100 meters outside the runway threshold and along the extension of the southern airfield boundary. The grass runway measures 600 meters by 40 meters and lies in open terrain offering good opportunities for outlandings.
The pilot had taken off at 1351 MEZ and was towed to the Holderbank/Schinznach-Bad region, where he released at approximately 700 meters above the airfield. He had set the altimeter to zero at field elevation before departure but noticed shortly after takeoff that it was not indicating correctly, forcing him to rely on visual height estimates throughout the flight.
After release, the pilot executed two large circles in search of thermal lift but found none and decided to return to the airfield about 5-6 km away. He arrived at what he considered sufficient altitude to fly a half circuit and integrate into the glider traffic on runway 26. After flying the downwind leg parallel to the runway, he began a 180-degree left turn approximately 100 meters east of the runway to align for final approach. During the turn, the left wingtip struck a 2.5-meter-high earth wall that extends along the southern runway boundary. The glider yawed approximately 180 degrees and touched down heavily sideways outside the airfield, resulting in substantial damage and the pilot's injury.
Discussion
The accident was attributed to the pilot's incorrect assessment of his altitude during the approach and his failure to recognize that it would be insufficient for a half circuit. Consequently, he did not consider an outlanding near the airfield, which would have been feasible without difficulty, and initiated the final turn at inadequate height. The defective altimeter, noted soon after takeoff, may have complicated the pilot's overall flight planning, but in the final phase—at altitudes below about 50-100 meters—he relied solely on visual estimates. The pilot's limited flight experience (approximately 3 hours since passing his glider test) and lack of recent practice (his last flight, over three months earlier, lasted only 5 minutes) rendered him unable to handle the task, leading to the altitude misjudgment and incorrect assessment of the situation.
Conclusions
The accident occurred because the inexperienced and untrained pilot was unable to correctly assess his altitude during the approach and consequently made ground contact while turning.