Accident Overview
On April 21, 2009, at approximately 1355 eastern daylight time, a Cessna 208, registration N208JW, sustained substantial damage following an engine fire after landing at Frederick Municipal Airport (FDK) in Frederick, Maryland. The airplane was powered by a single Pratt & Whitney Canada PT6A-114 turboprop engine and was operated by Greystoke Engineering, Inc. on a 14 CFR Part 91 ferry flight. The certificated airline transport pilot was not injured. Visual meteorological conditions prevailed, and no flight plan was filed. The flight had originated at Winchester Regional Airport (OKV) in Winchester, Virginia, at 1330.
Pilot Actions
The pilot reported a normal landing on runway 23. During the landing roll with power at idle, he heard a "pop" and the engine "started spooling down." After exiting the runway, he observed smoke coming from the engine compartment. Initially thinking it was residual fuel, he advanced the power lever. He did not see a master caution or engine fire light. As the smoke worsened, he recognized a fire, called for assistance, and shut off the fuel selectors and firewall shutoff valve. Airport line crew arrived and extinguished the fire.
Post-Accident Examination
An FAA inspector examined the airplane and reported extensive thermal damage to the fuselage sub-frame. Preliminary engine inspection revealed heat damage in the turbine section, and numerous turbine blade fragments were found on the runway. The aircraft owner provided a photograph of the exhaust duct interior showing a crescent-shaped witness mark approximately 3/16 inches in length, consistent in size and shape with a compressor turbine (CT) blade tip sample.
Engine Inspection
The engine was sent to Mint Turbines in Stroud, Oklahoma, for disassembly and inspection, conducted by the NTSB with participation from Cessna, Pratt & Whitney Canada, Greystoke Engineering, and Mint Turbines. External examination showed soot on the accessory gearbox but no thermal damage. The turbine exhaust duct had heat discoloration and metal splatter. The combustion chamber and exit duct showed no burn-through or cracks. Fuel nozzle shrouds were sooty, but the orifice was clean. Igniter plugs were intact with slight sooting.
Compressor turbine (CT) blades were melted down to the blade platform, with roots secured to the disk. The CT disk was intact with slight circumferential scoring. CT guide vanes had trailing edge thermal distress and missing material. The power turbine (PT) blades were melted, with outer halves missing and roots secured. PT guide vanes were melted, and T5 temperature probes were thermally damaged. The exhaust duct showed no uncontainment evidence. The reduction gearbox chip detector was clean.
Fuel Control Unit and Maintenance Records
The fuel control unit (FCU) was examined and tested at Pratt & Whitney Canada. No pre-existing defects were found, but high fuel flow was noted during testing. The specific gravity dome was set beyond the recommended range, and adjustments to the high-idle stop and minimum flow stop were detected, with anti-tamper paint disturbed and missing seal wire. Maintenance records indicated the engine had accumulated about 6 hours since an overhaul completed at Northstar Aerospace on September 18, 2008. The overhaul facility was later purchased by Mint Turbines. The airplane owner is the Managing Director of Air Services, Inc., which installed the engine. Examination of records and inquiries did not reveal the source of the FCU adjustments.