NTSB Identification: CHI90LA276.
The docket is stored on NTSB microfiche number 42836.
Accident occurred Thursday, September 27, 1990 in MORRISON, IL
Probable Cause Approval Date: 12/14/1992
Aircraft: MOONEY M20E, registration: N7197U
Injuries: 1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THE ACCIDENT AIRPLANE EXPERIENCED AN INFLIGHT FAILURE OF A PROPELLER BLADE DURING CRUISE FLIGHT. ACCORDING TO THE PILOT'S STATEMENT THE AIRPLANE STARTED A SEVERE VIBRATION AND REDUCING THE ENGINE POWER HAD NO EFFECT ON IT. THE VIBRATION STOPPED AFTER HE SHUT DOWN THE ENGINE AND RAISED THE NOSE IN ORDER TO STOP THE WINDMILLING PROPELLER. DURING THE FORCED LANDING THE LANDING GEAR COLLAPSED AND THE AIRPLANE SLID INTO A DIRT BANK. EXAMINATION OF THE REMAINING PORTION OF THE FAILED PROPELLER BLADE FRACTURE SURFACE SHOWED A FATIGUE CRACK EXTENDING FROM THE LEADING EDGE TO A POINT 3-1/4 INCHES MEASURED IN THE CHORDWISE DIRECTION. THE LEADING EDGE HAD BEEN REWORKED BY FILING OR GRINDING.

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

IMPROPER MAINTENANCE OF THE PROPELLER BLADE BY UNKNOWN PERSONS AND THE SUBSEQUENT FAILURE OF THE BLADE IN FATIGUE DURING CRUISE FLIGHT. A FACTOR WAS: UNSUITABLE TERRAIN.

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