IAD04LA016 · Pilatus P3-05

The single-engine experimental airplane was the lead airplane in a formation with three other airplanes, in cruise flight at 1,500 feet above the ground, when it suddenly experienced a catastrophic engine failure and began to veer to the left toward one of the other airplanes. The pilot of the other airplane turned to avoid the accident airplane, and noticed that the accident airplane's cockpit was filling with smoke. Oil was also seen streaming back onto the canopy. The accident pilot requested help, and one of the other pilots attempted to guide him to a safe off-field landing. The accident pilot was then observed to open the cockpit canopy. Smoke and oil were seen pouring onto the pilot's face. The accident airplane then continued to descend until impacting trees and terrain. Examination of the wreckage revealed that the engine's no. 2 connecting rod had separated and punched a hole in the crankcase. A detailed engine exam revealed that the no. 2 connecting rod bearing substrate had delaminated from the steel backing of the bearing, thus allowing excessive bearing clearance. This led to a failure of the rod cap bolts (due to overstress) and separation of the connecting rod from the crankshaft. The separated rod punctured a hole in the engine crankcase, allowing oil to escape and mechanical seizure of the engine. No materials deficiencies of any engine part were noted. The bearing type was the subject of a Lycoming Special Advisory (no. 59-800) in 2000, a Mandatory Service Bulletin (no. 547) in 2001, and another Mandatory Service Bulletin (no. 561) in 2004 which discussed delamination of the bearings for undetermined reasons, and recommended replacement of them with bearings that had "increased durability." These bulletins addressed a higher powered engine (TIO-540), and not the accident engine; however, two other instances of delaminated bearing failures from lower-powered engines (including one similar to the accident engine) were noted. The accident airplane had a propeller installed that was not the one required for normal certification. Additionally, the pilot frequently flew the airplane in formation, thus requiring frequent power changes (with a geared engine). Records indicate that all 6 cylinders were overhauled and sent back to the pilot's mechanic about 6 months before the accident. About 4 months before the accident, the mechanic changed the oil and oil filter about 20 operating hours after the cylinders were replaced. This entry (as well as a previous oil change entry 8 months prior) did not indicate that the oil filters and screens were opened and inspected for metal debris; however, the mechanic stated that he always checked for debris. The airplane had flown an additional 14 flights since the last oil change. The pilot's log indicated that 7 quarts of oil were added to the engine during that time. The final pilot logbook entry was dated one week before the accident and indicated that one quart of oil was added to the engine, at an engine time of 326.2 hours. The logs did not reveal any unresolved discrepancies.

Verbatim NTSB analysis and probable cause from the NTSB dataset