What happened
On August 29, 2009, a Cessna U 206 G departed from the Rheine-Eschendorf airfield (EDXE) for a VFR skydiving flight. The aircraft was carrying the pilot, three skydivers, and a tandem jump team. Approximately three minutes into the climb, the pilot noticed unusual noises and a significant rise in exhaust gas temperature, which was roughly 100°C above normal levels.
As the aircraft leveled off at an altitude between 1,200 and 1,400 feet AMSL, severe vibrations occurred, followed by smoke and flames emerging from the engine compartment. The engine then ceased functioning abruptly. Realizing the airfield was no longer reachable, the pilot initiated an emergency descent. The three skydivers successfully performed an emergency jump at approximately 1,000 feet and landed safely, while the tandem team remained on board.
With limited time and altitude, the pilot selected an emergency landing site in a field of corn located about 1.2 NM east of the airfield. The aircraft entered the tall crops at minimum airspeed with full flaps extended. During the landing, the aircraft slid approximately 40 meters and briefly tipped onto its nose before coming to rest. There were no fatalities or injuries, though the aircraft sustained heavy damage and there was damage to the surrounding crops.
The investigation
The BFU examined the engine and the aircraft's maintenance history. The engine was dismantled for inspection, revealing significant internal damage. Investigators found large amounts of metal shavings and deposits in the oil filter housing. Specifically, the connecting rod at cylinder No. 4 had broken and deformed, and the rod bearing at cylinder No. 1 was missing its bearing shells. The crankshaft bearings also showed signs of wear, and the crankshaft contained deposits of black tar and oil sludge. Notably, a grain ear was found inside the oil pan, though its exact role in the failure could not be determined.
Maintenance records showed that a 100-hour inspection had been performed just three days prior to the accident. During that inspection, cylinder compression tests had shown values approaching the maximum allowable tolerance limits. Additionally, the engine had been consuming approximately 0.7 liters of oil per hour during the preceding three days of operation.
Findings
- The primary cause of the engine failure was an interruption of the oil supply to the connecting rod and crankshaft bearings of cylinders No. 1 and No. 2.
- The reduction in oil supply to the crankshaft bearings was likely caused by the movement of particles from accumulated tar and oil sludge within the engine.
- The pilot's ability to select an alternative landing site was severely restricted by the low altitude and the rapid progression of the engine failure.
- The choice of a field with high vegetation was a consequence of the limited time and available landing options during the emergency descent.