Accident Overview
On 26 May 1990 at approximately 1020 local time, a Cessna C-421 C (registration HB-LKC) departed Altenrhein aerodrome for a training flight with a pilot and one passenger. The pilot performed two touch-and-go landings before proceeding toward the Zurich-East VOR at an altitude of 3000 feet QNH. After setting cruise power and mixture, both engines lost power. The pilot executed an emergency landing in a winter barley field. Both occupants were uninjured, but the aircraft sustained heavy damage. Minor crop damage occurred.
Flight History
The pilot had not flown the accident aircraft type for 10 months prior to the flight. On the morning of the accident, he conducted an external inspection and noted approximately 260 lbs of fuel in each main tank (totaling 520 lbs), with auxiliary tanks empty. The run-up was normal. After two touch-and-go circuits, the pilot set cruise power at 30 inches manifold pressure and 1700 RPM. About 5-6 minutes later, he adjusted the mixture levers to achieve a fuel flow of approximately 120 lbs/h and then further leaned until the EGT (exhaust gas temperature) rose to 200°F. After 2-3 minutes, both engines began losing power. The pilot reported no asymmetric thrust. He attempted to troubleshoot but lost significant altitude. He extended landing gear and flaps, and the aircraft touched down in a field, leaving a 22-meter skid mark before coming to rest upright. Post-accident examination showed the fuel selectors were on mains, booster pumps on low, and the mixture levers had been moved to rich after landing (by the pilot during the emergency). The fuel remaining was approximately 223 lbs in each main tank.
Aircraft Information
The Cessna 421 C (serial 421C-0084, built 1976) was a twin-engine, six-seat low-wing aircraft with retractable landing gear. It was powered by two Continental GTSIO-520-L engines (375 hp each) and McCauley propellers. The aircraft had a total of 2073:18 hours airframe time. At the time of the accident, the 100-hour inspection was overdue by 8:21 hours. Weight and balance were within limits. Fuel tests showed no contamination.
Investigation Findings
The aircraft wreckage examination revealed that the landing gear and flaps were extended, the throttle and propeller controls were in the idle and max positions respectively (altered after landing), and mixture controls were at rich. The propeller blade deformation indicated low or no engine power at impact. The flight controls showed no pre-existing defects. Weather at the time was good: 1/8 cloud, visibility over 10 km, wind east-northeast 5-10 knots gusting to 20 knots, temperature 14°C, QNH 1021 hPa. No fire occurred. The accident was survivable.
Cause
The accident was due to an emergency landing on soft ground following a power loss on both engines, probably for operational reasons (mixture). A contributory factor was insufficient training of the pilot on the accident aircraft type.