What happened
On May 12, 2017, a LANCAIR IV P, registration SE-XRU, was conducting a private cross-country flight from Aarhus, Denmark, to Kjeller, Norway. During the initial climb, the pilot noticed smoke appearing to emanate from the wings, though the aircraft continued its departure normally.
While climbing through 12,000 feet, the pilot observed the engine oil pressure dropping toward the low-pressure red line. In an attempt to stabilize the engine, the pilot reduced manifold pressure and began a descent back toward Aarhus. However, the oil pressure continued to decline, eventually falling below the minimum threshold. As the aircraft descended through 2,000 feet, the engine ceased functioning entirely after the pilot attempted to shut it down manually. Unable to reach the nearby airport at Grenaa, the pilot executed an emergency landing in an agricultural field. The impact caused substantial damage to the aircraft, including a broken wing and collapsed landing gear, though there were no injuries to the pilot or passenger.
The investigation
The Danish Accident Investigation Board examined the wreckage and the engine components to identify the cause of the failure. Investigators performed a metallurgy examination on the connecting rod bolts of the fourth cylinder and inspected the engine's internal components. The investigation also reviewed maintenance records and recent flight history, specifically noting a demonstration flight performed weeks prior that had shown significantly higher oil consumption than usual.
Findings
- The engine inspection revealed severe internal damage, including bearing shells that had operated without lubrication and heat damage to several connecting rod big ends.
- Evidence suggested the engine failure was likely caused by oil starvation.
- While the engine showed signs of extreme distress, investigators could not definitively determine why the oil level had depleted to such a critical level.
- A previous flight had recorded an unusual consumption of 3 quarts of oil, which may have been a precursor to the eventual failure, though the pilot believed the increased consumption was normal following recent maintenance.
- Metallurgy tests confirmed that the fractures in the engine bolts were consequential results of the engine's mechanical failure rather than the initial cause.