Accident Overview
On 1 May 1966 at approximately 1619 MEZ, a Piper PA-22-150 Tri-Pacer with registration HB-OPL sustained substantial damage during a takeoff attempt at the private airfield Wangen-Lachen in the canton of Schwyz, Switzerland. The aircraft was being used for flight training under the supervision of a flight instructor. The student pilot, who was at the controls, was not injured.
Sequence of Events
The student pilot, accompanied by the instructor and a passenger, had flown from Spreitenbach to Wangen-Lachen for touch-and-go landing practice. After landing, the instructor instructed the student to taxi back to the landing T and perform a solo circuit. The first takeoff was extremely tight, with the aircraft lifting off only at the field's edge near the lake. Concerned, the instructor walked the eastern portion of the field and, believing the ground sufficiently firm, signaled the student to commence a second takeoff from the eastern end. The student aligned the aircraft and applied full power. Initially acceleration was good, but the aircraft encountered soft spots where the main wheels sank slightly, then the nose wheel dug approximately 30 cm into the ground left of the centerline. The nose wheel strut bent backward, and the propeller, nose, and left wing contacted the ground. The aircraft slid to a stop after about 110 m.
Aircraft and Site Information
The Piper PA-22-150 Tri-Pacer (serial number not specified) was a four-seat, strut-braced high-wing monoplane with fixed tricycle landing gear. It was powered by a Lycoming O-320 engine producing 150 hp. At the time of the accident, the airframe and engine had accrued 983 hours each. The aircraft's weight was approximately 700 kg, below the maximum of 907 kg, and the center of gravity was within limits. The airfield had a single grass runway measuring 440 m by 30 m, oriented 09/27. Due to drainage and grading works, a NOTAM had been issued on 27 January 1966 temporarily closing the field, but operations on the western two-thirds were permitted. On the day of the accident, the landing T was placed 150 m from the eastern end, leaving about 300 m to the lake shore.
Personnel
The student pilot, born in 1939, held a learner's permit for motorized aircraft issued on 27 October 1965, valid until 18 October 1967, with an extension for cross-country flights from 30 April 1966. Total flying experience was 12 hours and 6 minutes with 122 landings, of which 2 hours 54 minutes and 29 landings were solo; all solo flights were on the accident type. The flight instructor, born in 1927, held a valid private pilot license from 23 May 1947 and an instructor endorsement from 25 June 1960. The airfield was operated by the Ausser-Schwyzerische Fluggemeinschaft (ASFG); the airfield manager (born 1929) and other pilots were involved in organizing flight operations that day.
Probable Cause
The immediate cause of the accident was that the student pilot, on the instruction of his flight instructor, initiated the takeoff on a part of the airfield that was insufficiently load-bearing.