What happened
On April 1, 1961, two gliders belonging to the Schaffhausen Gliding Group were performing ridge soaring maneuvers near the Randenturm at Schloss Randen. The first aircraft, a Grunau Baby GB II with registration HB-170, had been towed to an altitude of approximately 900 meters earlier in the afternoon. Shortly thereafter, a second glider, a Rhönlerche RL II registered as HB-669, followed a similar flight path.
At approximately 15:00, the HB-669 was flying roughly 50 meters behind and 20 to 30 meters below the HB-170. As the HB-170 initiated a right-hand turn, the pilot of the HB-669 observed the aircraft tilting slightly to the left and mistakenly assumed the lead aircraft intended to turn left. In response, the pilot of the HB-669 also entered a right-hand turn. This maneuver caused the pilot to lose visual contact with the lead aircraft. When the pilot of the SB-669 regained sight of the HB-170, a collision was unavoidable. The left wingtip of the Rhönlerche struck the nose of the Grunau Baby, causing the wingtip to break off and become embedded in the other aircraft's fuselage.
Despite the impact, both pilots were able to land the aircraft safely. The HB-669 returned to the Schaffhausen-Neunkirch airfield, while the HB-170 experienced a brief dive before managing to land near Hinterranden.
The investigation
The investigation examined the flight paths, pilot qualifications, and aircraft conditions. Both pilots were found to have good flying skills and no underlying health issues were identified. The aircraft, a Grunau Baby GB II and a Rhönlerche RL II, showed no technical defects prior to the incident. The investigation focused on the sequence of maneuvers and the decision-making process regarding separation during the turn.
Findings
- The primary cause of the collision was the improper maneuvering of the pilot of the HB-669, who reacted to the lead aircraft's turn with a similar turn rather than maintaining separation.
- The pilot of the HB-669 flew too close to the HB-170, reducing the safety margin to a level that was inappropriate for their level of experience.
- The pilot of the HB-669 lost visual contact with the other aircraft due to the simultaneous right-hand turns, which led to a rapid decrease in separation.
- The HB-170 sustained heavy damage to its instrument panel, cockpit canopy, and nose, while the HB-669 suffered severe damage to its left wing.