NTSB Identification: LAX02LA104.
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Accident occurred Thursday, March 07, 2002 in BULLHEAD CITY, AZ
Probable Cause Approval Date: 09/30/2003
Aircraft: Cessna 172L, registration: N7774G
Injuries: 2 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.
During the takeoff departure the student pilot experienced a catastropic failure of the propeller. Control tower personnel reported that shortly after takeoff, about 800 feet above the runway, the airplane experienced a mechanical problem and returned to the runway. They also noted substantial damage to the front of the engine compartment with debris scattered on the runway. Preliminary examination of the airplane revealed a disintegrated propeller hub with loss of a propeller blade and a severed crankshaft aft of the shaft flange. Substantial damage was evident to the firewall assembly with the engine pointing down about 30 degrees. The pilot stated that there were no prior indications of a discrepancy with the engine or airframe during the run-up or takeoff. He said that the engine ran smoothly until there was a big explosion that "took off the front end." The last documented annual inspection occured in January 2001; an inspection that is required every 12 months per FAR 91.409a (1), as are other inspections and procedures. According to records, the propeller was installed on the airplane during a powerplant modification February 1, 1988, at airplane tachometer reading of 3,966 hours. The propeller had been overhauled August 24, 1987, at 1,971 hours. At the time of the accident, the propeller had accrued 313 hours since overhaul, over 14 years prior. The McCauley factory recommended overhaul is 1,200 hours or 60 months. Examination of the propeller hub revealed a crack progression from a corrosion pit inside the hub to a point of overload failure. McCauley Service Bulletins 213 and 213A were issued January 20, 1994, and June 5, 1998, to provide improved lubrication and corrosion protection, as well as a built-in means of crack detection. According to SB213A, the recommended compliance time for propellers greater than 900 hours or 59-calendar months since last overhaul/penetrant inspection is within the next 100 hours, or at the next annual inspection, whichever occurs first.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to comply with maintenance/inspection requirements that resulted in a propeller failure. Full narrative available
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