SAN MANUEL, AZ, USA
N234GA
MOONEY M20F
DURING CRUISE AT 10,500 FT MSL ON A NIGHT X-COUNTRY FLT, THE PLT SAID THE ENG RAN ROUGH WITH MODERATE VIBRATION LEVELS. PLT DECLARED AN EMERGENCY WITH ABQ ARTCC, WHO VECTORED THE ACFT TO AN UNLIGHTED AIRSTRIP. THE PLT SAID HE HAD DIFFICULTYIN SEEING THE RWY IN THE DARKNESS. THE ACFT LANDED LONG, BLEW A TIRE, VEERED OFF THE RT SIDE OF THE RWY & STRUCK A TREE.EXAMINATION OF THE ENG REVEALED THAT THE #3 CYLINDER WAS AJAR FROM THE CASE, WITH ALL THE TOP HOLD DOWN STUDS & NUTS IN PLACE BUT BENT UPWARD. THE NUTS WERE MISSING FROM THE LOWER FORE & AFT LARGE HOLD DOWN STUDS, & THE REMAINING CENTER STUDS HAD ALL FRACTURED AT THE CYLINDER FLANGE LEVEL. THE ENG WAS OVERHAULED 6 MONTHS AND 21 HRS PRIOR TO THE ACCIDENT. THE FAA AIRWORTHINESS INSPECTOR WHO EXAMINED THE ENG STATED HIS OPINION THAT THE NUTS ON THE LOWER LARGE STUDS WERE UNDERTORQUED AT INSTALLATION.
Source: NTSB Aviation Accident Database
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