NTSB Identification: CHI01FA220.
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Accident occurred Thursday, July 19, 2001 in EDEN PRAIRIE, MN
Probable Cause Approval Date: 08/26/2002
Aircraft: Mooney M-20R, registration: N2HW
Injuries: 1 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 airplane was observed proceeding westbound from the airport at a low altitude. A witness said, "I watched and listened thinking he would soon apply power and climb. The engine noise was smooth sounding but low. The plane was not gaining altitude and slowly losing altitude." The witness said the airplane flew parallel to, and north of the road in front of her house. "As it crossed the point of my driveway, the plane banked slightly, hit the tree tops and crashed and exploded." Control tower communications revealed that shortly after being instructed to contact departure control, the pilot responded, "two hotel whiskey - engine failure". An examination of airframe records showed that a new engine was installed at the annual inspection on February 5, 2001. The airplane logged approximately 75.7 hours from the time of the annual inspection to the time of the accident. An examination of the airplane's engine revealed that three teeth from the camshaft gear were fractured. An additional eight teeth were crushed, in total rendering the camshaft unable to be driven. A Materials Laboratory examination of the camshaft gear and fractured gear teeth showed two of the three teeth indicating signs of fatigue. The third tooth showed evidence of overstress. Rockwell hardness measurements made on the gear portion of the camshaft gear showed an average hardness of Rockwell 64HR30-N. Specification drawings for the camshaft gear indicated that the gear teeth should be hardened by gas-nitride process to a hardness of Rockwell 69HR30-N, minimum.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The fractured camshaft gear and the pilot not maintaining aircraft control. Factors relating to this accident were metal fatigue in the camshaft gear teeth, the inadvertent stall, the low airspeed, and the trees. Full narrative available
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