Mx Aircraft Llc MXS N540JH accident near Fulton, Texas

Probable cause

A total loss of engine power due to the fatigue failure of the crankshaft, which resulted in the pilot’s forced landing to an abandoned airport and the airplane’s subsequent impact with debris on the runway.

NTSB analysis

The airline transport pilot reported that, while in cruise flight at 11,500 ft above mean sea level, the engine began to vibrate. About 30 seconds later, he heard a “bang.” A piece of the engine had penetrated the engine cowling, and engine oil covered the outside of the canopy, restricting the pilot's vision. He stated that the engine lost total power and that an extreme vibration occurred until he slowed the airplane and the propeller stopped rotating. The pilot chose to fly to an airport that he identified on his GPS and performed a forced landing at that airport, during which the left main gear separated from the fuselage after impact with a piece of debris on the runway. The airplane slid on its belly before veering off the runway and coming to rest in the grass. It was later determined the pilot had landed at an abandoned airport.

An initial examination of the engine, which was a modified version of a six-cylinder Lycoming AEIO-540 engine, revealed a hole in the top of the crankcase just behind the oil filler cap at the No. 5 cylinder. The crankshaft was visible through the hole in the top of the engine, and a broken counterweight was noted. Metallurgical examination of the crankshaft revealed that it had fractured between the No. 5 and No. 6 rod journals. The fracture was the result of a fatigue crack that initiated from the aft radius of the No. 5 rod journal. The surface of the No. 5 rod journal and the radii contained circumferential gouges, which suggest that the bearing for this rod journal had shifted or was thinning down; the gouges were the stress raisers that led to the fatigue cracking. Shifting or malfunction of the bearing likely interfered with the lubrication of the rod journal surface and their radii, which likely caused the eventual overheating of the rod journal.

The property that once was the airport belonged to the Texas Parks & Wildlife Department. Although the property was no longer maintained as an airport, the Texas Parks & Wildlife Department had not contacted the Federal Aviation Administration to update the status of the airport. Appropriate steps were taken to decommission the airport after this accident.

Text from the NTSB. Open the NTSB docket for CEN18LA127 for the full record.