Flight History
On 23 June 1995 at 0815 local time, the pilot departed Grenchen, Switzerland, for a flight to Augsburg, Germany. Approximately 30 minutes later, during cruise at about 4000 ft QNH, the pilot noticed a change in airflow noise on the right side and observed the right door moving outward at the upper front corner by about 5 cm. Before the pilot could reach the door handle, the door was torn outward and forward, separating from the aircraft and falling to the ground. The pilot observed damage to the underside of the right wing and the right tailplane, and after verifying no unusual vibrations, returned to Grenchen for an uneventful landing. The door and its hinge components were not recovered.
Investigation Findings
The pilot held a valid PPL/IFR license and had 412 total flight hours, 194 on type. The aircraft, a Cessna 182 Skylane RG (registration N-7369X), was privately owned and had been purchased by the pilot in the USA in 1988 and flown to Switzerland in February 1992. It was always parked outdoors. No repairs or adjustments to the doors had been made since the pilot's ownership. The Cessna service manual required inspection of doors, locks, and hinges every 100 hours; the last 100-hour inspection was performed on 10 March 1995 by an FAA-authorized maintenance facility in Germany. Mass and center of gravity were within limits.
Metallurgical examination of the upper hinge by the Swiss Federal Laboratories for Materials Science and Technology (EMPA) revealed that the brass hinge pin had fractured in torsion, and the fracture occurred several flights before the incident. The hinge body was aluminum, and the hinge bearings had not been lubricated during assembly. Corrosion between the aluminum hinge and brass pin had reduced the freedom of movement, causing the upper hinge to seize. When the door was subsequently moved, the pin twisted off. The door remained partially attached because the fracture surface was not perfectly aligned with the hinge separation plane, but the shortened bearing allowed progressive wear from the door's weight. The weakened hinge then failed in flight due to aerodynamic suction, leading to door separation.
Cause
The accident was attributed to corrosion between the aluminum door hinge and the brass hinge pin, which led to fracture of the upper hinge pin on the right door.
Damage
The aircraft was substantially damaged. Damage to third parties was unknown.