Summary
On Sunday, 13 September 1959 at approximately 1810 local time, a collision occurred on the grass runway of Lachen-Wangen airfield between two Piper J3C (L4) aircraft, registered HB-OIR and HB-OBP. The aircraft HB-OBP was taxiing from its parking position across the runway for takeoff, while HB-OIR was on final approach to land. As HB-OIR flared about half a meter above the runway, it struck HB-OBP. Neither the pilots nor their passengers suffered any injuries. Both aircraft were substantially damaged.
Aircraft and Pilots
Both aircraft were Piper J3C (L4) high-wing monoplanes with Continental A-65 engines, privately owned and operated. HB-OIR had accumulated 1,742 flight hours since its Swiss certification in 1947; HB-OBP had 1,481 hours since 1947. The pilot of HB-OIR, born in 1903, held a private pilot license (issued 1948, valid until 5 January 1961) with endorsements for glider towing and a limited commercial pilot license. He had 334 total flight hours with 1,484 landings. In 1959, he had flown only 4 hours before the accident. His passenger, born in 1932, was a German national. The pilot of HB-OBP, born in 1914, held a private pilot license (issued 29 October 1949 after a retest) and a limited commercial pilot license (after a retest on 29 November 1950), with endorsements for towing and aerobatics. He had 517 total flight hours with 1,815 landings, including 50 hours in 1959. He was also the deputy airfield manager and served as flight operations officer on the afternoon of the accident. His passenger, born in 1903, was a Swiss national and held a private pilot license provisionally renewed on 22 August 1959.
Sequence of Events
The pilot of HB-OIR departed Lachen at 1750 for a local flight. He overflew the field at 300 m, then began a landing approach to the east, as indicated by the landing arrow at the western end. During the approach, he saw two parked Pipers near the restaurant and the fuel pump, including HB-OBP. He saw the runway was clear and continued to land. While flaring, he saw HB-OBP taxiing across the runway directly in front of him. He attempted to turn right but could not avoid collision. HB-OIR struck the rear fuselage of HB-OBP, causing HB-OIR to nosed over and come to rest inverted. The passenger of HB-OIR said he saw HB-OBP rolling towards the runway but assumed it would stop before the edge; when it continued, he had no time to warn the pilot.
The pilot of HB-OBP had fueled his aircraft and then taxied in a left turn towards the runway, with the passenger in the rear seat. Initially planned as a training flight for the passenger, it was agreed that the pilot would taxi and take off. Before crossing the runway boundary, the pilot attempted to close the cockpit window but dropped the retaining screw onto the floor; he searched for it without stopping or slowing for several seconds. Immediately afterward, he taxied onto the runway at an angle, about 100 m from the start, and had rolled about 17 m when the collision occurred. Neither he nor his passenger saw the approaching aircraft HB-OIR before impact.
Weather Conditions
The accident occurred about half an hour before sunset under a cloudless sky. The wind was from the east at approximately 5 km/h, barely noticeable. The landing arrow was placed 60 m inside the western end, indicating takeoffs and landings should be from west to east. The sun was exactly due west, 5–6° above the horizon, along the runway axis, potentially causing glare for the occupants of the taxiing aircraft.
Regulations
The Federal Department of Posts and Railways had issued regulations on 20 September 1950 stating:
- Article 23.1: Aircraft landing or on final approach have right of way over all other aircraft.
- Article 24: An aircraft ready for takeoff must not start if there is risk of collision.
The local airfield regulations (1 May 1951) required:
- Article 7: The airfield manager or deputy is responsible for safe operations.
- Article 8: Taxi slowly, use the rolling zone south of the runway, and give way to departing and landing aircraft.
- Article 10: Take off from the runway start.
- Article 13: Maintain intensive airspace observation.
Damage
No injuries were sustained by any of the four occupants. HB-OIR suffered damage to the engine cowling, undercarriage, and propeller, while the wings, rear fuselage, and tail remained externally intact. HB-OBP sustained destruction of the fuselage from the cabin aft to the tail, while the cabin, wings, engine, propeller, undercarriage, and tail remained externally intact.
Probable Cause
The collision occurred primarily due to disregard of taxiing regulations and insufficient airspace observation by the pilot who was preparing to take off.