NTSB Identification: ATL89FA035.
The docket is stored on NTSB microfiche number 38452.
Accident occurred Monday, November 14, 1988 in MOHAWK, TN
Probable Cause Approval Date: 01/24/1990
Aircraft: HUGHES 269C, registration: N9575F
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 HELICOPTER HAD LANDED AT A PRIVATE AIRSTRIP AND THE INSTRUCTOR DEPLANED. THE DUAL STUDENT REMAINED IN THE HELICOPTER WITH THE ENGINE RUNNING. THE CFI REBOARDED AND THE STUDENT MADE THE TAKEOFF. LATER, ON DOWNWIND IN TRAFFIC PATTERN, A WITNESS REPORTED A LOUD NOISE FROM THE ENGINE. THE MAIN ROTOR WAS OBSERVED TO SLOW NOTICEABLY AND THE HELICOPTER ENTERED A VERY STEEP DESCENT, IMPACTING THE GROUND ABOUT 1,000 FEET SOUTH OF THE RUNWAY. THE ENGINE ROD BOLTS ON THE NUMBER FOUR CYLINDER HAD FRACTURED. EXAMINATION OF THE FLIGHT CONTROLS REVEALED NO EVIDENCE OF PREIMPACT FAILURE. ONE OF THE ROD BOLTS WAS METALLURGICALLY EXAMINED AND SHOWED CRACKING THROUGH 25 PERCENT OF THE BOLT. THE FATIGUE WAS ATTRIBUTED TO INSUFFICIENT PRELOAD ON THE BOLT. THE ENGINE HAD 813 HRS SINCE A MAJOR OVERHAUL AND 36 HRS SINCE ANNUAL INSPECTION.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

ENGINE ASSEMBLY,CONNECTING ROD BOLT..FATIGUE

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

AUTOROTATION..DELAYED

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

ROTOR RPM..NOT MAINTAINED..PILOT IN COMMAND(CFI)

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

MAINTENANCE,OVERHAUL..INADEQUATE..OTHER MAINTENANCE PERSONNEL

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

ENGINE ASSEMBLY,PISTON..BURNED


Contributing Factors

MAINTENANCE,100-HOUR INSPECTION..INADEQUATE..COMPANY MAINTENANCE PERSONNEL

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