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NTSB recommendations target on-condition maintenance programs
2 October 2009

On November 8, 2005, an Embraer 110P1 crashed into a department store garden center shortly after takeoff from Manchester-Boston Regional Airport (MHT), NH. The airplane was destroyed, and the certificated airline transport pilot was seriously injured. The accident occurred following a loss of power to the left engine.
The NTSB determined that the probable cause of this accident was the pilot’s misapplication of flight controls following an engine failure. Contributing to the accident was the failure of the sun gear, which resulted in the loss of engine power. Contributing to the sun gear failure were the engine manufacturer’s grandfathering of previously recommended, but less reliable, maintenance standards, the Federal Aviation Administration’s (FAA) acceptance of the engine manufacturer’s grandfathering, the operator’s inadequate maintenance practices, and the FAA’s inadequate oversight of the operator.
As a result, the NTSB issued four safety recommendations to the FAA:
– Require all operators of PT6A-34, -35, and -36 engines, including those using on-
condition maintenance programs, to incorporate the reliability standards, particularly those concerning life-limited components, noted in the most current service bulletin into their engine maintenance programs. (A-09-108);
– Evaluate the effectiveness of the Portland Flight Standards District Office’s surveillance of maintenance programs and implement necessary changes so that inadequate maintenance programs are identified and improved. (A-09-109);
– Resolve the differences between Advisory Circular (AC) 120-17A and AC 120-16E in regard to Federal Aviation Administration philosophy and use of on-condition maintenance programs. (A-09-110);
– Once the differences noted in Safety Recommendation A-09-110 are resolved, review existing on-condition maintenance programs to ensure that they are compatible with the most current accepted philosophy. (A-09-111) (NTSB)