Accident Overview
On Friday, June 18, 1993, at approximately 1650 local time, a Piper PA-28-161 (registration HB-PGG) crashed on the Obersee near Lachen, Switzerland. The aircraft had departed from Wangen-Lachen airfield with a pilot and a passenger for a pleasure flight. Shortly after takeoff, the engine lost power and began to stutter, forcing the pilot to execute an emergency landing on the lake. The aircraft capsized after touchdown and sank; however, both occupants managed to free themselves and were rescued by a boat. The aircraft sustained substantial damage, primarily from water ingress and recovery, while the occupants remained uninjured.
Aircraft and Crew
The aircraft was a single-engine, four-seat low-wing Piper PA-28-161, manufactured in 1981, with a Lycoming O-320-DG3 engine (118 kW/160 hp). It was owned and operated by Aero Locarno SA. The pilot, a Swiss national born in 1958, held a private pilot license issued in 1982 and had logged 254 total flight hours, with 87 hours on the accident type. The passenger, also Swiss born in 1958, had no aviation experience.
Flight Details
The pilot had flown from Locarno to Wangen-Lachen earlier that day, landing after 58 minutes. After a half-hour break, the passenger arrived. The pilot prepared the aircraft, taxied to runway 26, and performed pre-takeoff checks. During the takeoff roll, the engine produced normal power. After liftoff, at about 15-20 meters above ground, the engine power dropped and the engine began to stutter. A flight instructor observing the departure noted a slightly low engine tone and a light black smoke trail.
Emergency Landing
The pilot repeatedly adjusted the mixture, fuel pump, and carburetor heat. He briefly regained power after about 15 seconds, then attempted a right turn over the Obersee to return to the airfield. Power faded completely, and he performed a forced landing on the lake approximately 900 meters northwest of the airfield. The aircraft nosed over and began to sink. Once the cabin filled with water, the occupants opened the door and surfaced, where they were picked up by boats.
Investigation Findings
Examination of the wreckage revealed no mechanical defects in the engine, fuel system, or airframe. The fuel tanks contained a water-fuel mixture. The carburetor was found to have two deficiencies: the basic adjustment was set for an excessively rich mixture, and a small component known as the "pump discharge tube" was missing from the carburetor housing. This tube had been secured with adhesive in this carburetor type, and no remnants of a metallic bond were found. An airworthiness directive (HB 93-483) addressing potential power loss due to a two-piece venturi was not yet effective at the time of the accident. The spark plugs indicated a rich mixture; no other anomalies were noted.
Probable Cause
The accident was caused by a loss of engine power during the initial climb due to insufficient mixture formation in the carburetor.