Incident Overview
The flight impacted terrain in a residential neighborhood about one mile north of the departure airport while executing an emergency return. The airplane struck a wooded area in a 20-degree nose-down trajectory and came to rest approximately 142 feet from the initial impact point.
Pilot Reports and Witness Observations
Approximately 55 seconds after takeoff, the pilot reported smoke in the cockpit. A second report of a fire followed 32 seconds later. A witness observed gray and black smoke trailing from the right side of the exhaust area. Radio transmissions from the flight continued after the initial report of smoke.
Wreckage Examination
Inspection of the wreckage revealed that the turbocharger exhaust V-band clamp had separated through the band. Metallurgical examination determined that the separation was consistent with a fatigue fracture.
Maintenance History
According to maintenance records, the V-band clamp was originally installed in 1990 in response to a service letter (SL). An airworthiness directive (AD) issued in 1991 required replacement of the clamp with one of the same part number specified by the SL. The clamp found in the wreckage was of that same part number. The airplane had received an annual inspection 25 days prior to the accident; at that time, the clamp had accumulated 1,402 hours of service. Since its original installation, the clamp had been repeatedly removed and reinstalled during engine overhauls and exhaust system maintenance.
Emergency Procedures
The airplane's emergency procedures for smoke or fire specify that the master switch and fuel selector valve should be set to the off positions. Inspection of the wreckage revealed that the fuel selector valve was selected to the right fuel tank.