CESSNA 208 near Frederick, MD — 2009-04-21

Probable cause

A loss of engine power due to the failure of one or more compressor turbine blades for an undetermined reason.

NTSB narrative

During the landing roll, with the power lever at idle, the pilot heard a “pop,” followed by indications of the engine “spooling down.” He exited the runway and observed smoke coming from the engine compartment. Thinking this was residual fuel, he “spooled the engine.” Realizing there was a fire, he called for assistance and shut off the fuel selectors and firewall shutoff valve. After the accident, a FAA inspector examined the airplane and reported extensive thermal damage to the fuselage sub-frame and evidence of an engine fire. Numerous engine turbine blades were found on the pavement adjacent to where the fire occurred. A disassembly and inspection of the engine revealed that one or more of the compressor turbine (CT) blades failed. The engine was overhauled about 6 hours prior to the accident. The CT blades were manufactured under the FAA Parts Manufacture Approval (PMA) program. Extreme heat damage obliterated the fracture surfaces of the blades, therefore the reason for the blade failure(s) could not be determined. A functional test of the fuel control unit (FCU) revealed the Sg (specific gravity) dome, high idle stop screw, and minimum flow stop were set above the recommended range, which would result in higher than normal fuel flow. The FCU adjustments appeared to be made after the overhaul, however it could not be determined when the adjustments occurred. Although the higher than normal fuel flow setting probably did not result in the CT blade failures, it could have exacerbated the thermal damage and fire.

Analysis

Primary failure mode

Mechanical failure

First missed decision gate

Pilot could have shut down the engine after hearing the 'pop' sound.

NTSB coding

• Powerplant sys/comp malf/fail · Taxi-from runway

Evidence available

• 10 docket documents

Docket documents10

• Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1form
• FAA Inspector Statementinterview
• Statement of Party Representatives to NTSB Investigationinterview
• Aircraft Maintenance Recordsother
• CT Disk Exam Notesother
• Correspondence - Kasabulaother
• Correspondence - Wallaceother
• Log of Engine Testother
• Powerplants Group Notesother
• PWC Fuel Control Inspection Reportreport