GRAND CANYON, AZ, USA
N6670R
MOONEY M20C
WHILE CRUISING EN ROUTE ALL ENGINE POWER WAS SUDDENLY LOST AND THE PLT ATTEMPTED AN EMERGENCY LDG AT THE GRAND CANYON ARPT. DURING THE GLIDE, THE ACFT CRASHED INTO AN OUTCROP OF ROCKS ON A STEEP CLIFF, 0.5 MI FROM THE END OF THE RWY. EXAM OF THE ENGINE REVEALED THAT ONE OF THE #3 CONNECTING ROD BOLT NUTS HAD BACKED OFF THE BOLT, AND OTHER NUT HAD BEEN PARTIALLY STRIPPED OFF ITS BOLT. THE ENGINE HAD BEEN OPERATED FOR 212 HRS SMOH. LAB EXAM OF THE BOLT/NUT INTERFACE INDICATED THAT THE NUTS HAD BEEN UNDERTORQUED WHEN THEY WERE LAST INSTALLED.
Source: NTSB Aviation Accident Database
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