M-Squared Aircraft SPRINT 1000 N138ZX accident near Gurdon, Arkansas

Probable cause

Inadequate engine maintenance, which resulted in the failure of the MAG piston ring and the subsequent total loss of engine power due to a piston seizure.

NTSB analysis

The pilot reported that he and a passenger had just departed on a local, personal flight when the engine “suddenly stopped.” Shortly thereafter, the engine seized, and the airplane began to descend rapidly. The pilot deployed the airplane's ballistic parachute about 200 ft above ground level, and the airplane then landed hard in a residential area, which resulted in substantial damage to the wings and fuselage. The pilot recalled that, during the takeoff and climb, the instruments showed no unusual indications and that the engine made no unusual sounds.

Examination of the engine revealed that the top of the MAG piston ring had failed, which resulted in damage to the MAG piston and cylinder walls. Both rubber PTO and MAG carburetor intake sockets were worn and cracked. Complete engine records were not available, and no record was found indicating that the engine had been overhauled during its 23 years of operation. The engine manufacturer recommended that the engine should be overhauled every 300 hours or 5 years, whichever occurred first, and that the rubber carburetor intake sockets should be replaced every 5 years or as signatures of deterioration were detected. Cracked rubber carburetor intake sockets can result in a lean mixture and lead to a piston seizure. The inadequate maintenance of the engine likely led to the failure of the MAG piston ring and the subsequent loss of all engine power due to a piston seizure.

Text from the NTSB. Open the NTSB docket for CEN18LA189 for the full record.