NTSB Identification: CHI95FA071.
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Accident occurred Saturday, January 21, 1995 in DES MOINES, IA
Probable Cause Approval Date: 09/24/1995
Aircraft: BACON QUESTAIR-VENTURE, registration: N4QV
Injuries: 2 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
THE PRIVATE PILOT DECLARED AN EMERGENCY WHILE AT 16,000 FEET IN VFR CONDITIONS OVERHEAD THE 9,000 FOOT RUNWAY. DURING THE DESCENT HE STATED HIS ENGINE RAN ROUGH, THEN SMOOTHED OUT. APPROXIMATELY 4,000 FT AGL HE STATED HE 'HAD A MAJOR PROBLEM...COMING DOWN.' WITNESSES DESCRIBED THE AIRPLANE IN A STEEP DESCENT, THEN ENTERING A SPIN AT APPROXIMATELY 1,000 FT AGL. THE AIRPLANE IMPACTED 3/4 MILE SHORT OF THE RUNWAY. TESTING REVEALED THE CRANKSHAFT FAILED IN 2 PLACES, BOTH WITH AREAS OF FATIGUE CRACKING. THE FATIGUE ORIGIN WAS SUBSURFACE, THE SHAFT WAS MACHINED, NOT FORGED, AND HAD AN ESTIMATED 150 TO 200 HOURS IN OPERATION. NO OTHER DISCREPANCIES WERE FOUND WITH THE AIRPLANE.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to maintain aircraft control during the emergency descent, resulting in a stall/spin. Factors were material defects in the material used to manufacture the crankshaft, resulting in the crankshaft fracturing after approximately 200 hours in service. Full narrative available
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