What happened
On October 1, 2001, a Cessna F172G, registration D-EJUS, was conducting a transit flight from Son Bonet aerodrome to Palma de Mallorca airport. The aircraft was flying in a formation with two other aircraft when, approximately 35 minutes into the flight, the pilot observed rising engine temperatures and a decrease in engine RPM. Following the observation of smoke emanating from the engine, reported by the accompanying aircraft, the pilot initiated an emergency landing.
Seeking a location away from populated areas, the pilot identified a road with no traffic. During the landing maneuver, the aircraft deviated from the center of the road, causing the left wing lift strut to strike a stone wall. The right wing tip then impacted a concrete post, which induced a rightward turn and caused the aircraft to crash into a second stone wall on the left side of the road. The impact resulted in important damage to the aircraft.
The investigation
The investigation focused on the mechanical state of the Rolls Royce O-300-D engine and the circumstances of the landing. Investigators examined the fuel, lubrication, and ignition systems, as well as the physical wreckage.
Engine inspections revealed that the propeller blades were either intact or bent backward, indicating the engine was at low RPM or stopped at the moment of impact. While the fuel system and lubrication system showed no evidence of leaks prior to the crash, the oil filter contained metal splinters and significant carbon residues. Furthermore, the investigation found that the magneto timing was incorrect; the right magneto was set 1° below the manual specification, while the left magneto was set 2° above the specification. Cylinder compression tests identified significant failures in cylinders 2, 3, and 6. Specifically, in cylinder 3, the piston and piston rings were found to be broken.
Findings
- The primary cause of the accident was a loss of engine power that necessitated an emergency landing in an unsuitable area.
- The engine failure was attributed to the breakage of the piston and piston rings in cylinder 3.
- Incorrect magneto timing (preignition/postignition) likely contributed to the deterioration of the engine components.
- The aircraft's impact with the concrete post and stone walls was a result of the narrowness of the chosen landing site and the deviation from the road centerline.