What happened
A Boeing 737-217 was completing a flight from Québec, Quebec, to Fredericton, New Brunswick, when the aircraft experienced an engine malfunction during its landing roll on runway 15. As the crew deployed the thrust reversers, the No. 1 Pratt & Whitney JT8D-17A engine experienced a sudden spool down, accompanied by visible flames exiting the tailpipe.
Upon noticing the flames, a flight service station specialist alerted the crew and activated the airport crash alarm. Airport firefighters arrived at the aircraft in approximately 70 seconds. The crew successfully secured the malfunctioning engine and brought the aircraft to a halt on the runway. Following a visual inspection by emergency responders, the aircraft taxied to the ramp, where all passengers and crew members deplaned without injury.
The investigation
Investigators examined the engine and discovered that the 4th-stage low-pressure turbine (LPT) wheel had lost all of its blades. While the engine failure was contained, the deployment of thrust reversers caused metal fragments from the shattered blades to be deflected against the aircraft's side. This impact resulted in dents and gouges to the fuselage skin, some of which exceeded serviceable limits, and necessitated the replacement of several windows.
An engine teardown and metallurgical analysis by the TSB Engineering Laboratory focused on the LPT components. The investigation revealed that a single 4th-stage blade had suffered a fracture characterized by both fatigue and overstress. The fatigue crack had originated near the trailing edge and traveled 14 mm along the blade chord. The pattern of this crack was consistent with previous failures linked to blade shroud cross notch (BSC) wear.
Findings
- The primary cause of the engine failure was the fatigue and subsequent overload failure of 4th-stage LPT blades.
- The failure was precipitated by wear at the blade shroud cross notch (BSC), which altered the blade's vibration modes.
- The investigation established that measuring BSC wear via torque readings is not a reliable method for predicting LPT blade failure specifically on the JT8D-17A engine model.
- Although the operator had performed required inspections only 56 hours prior to the event and recorded satisfactory torque readings, the inspection failed to detect the impending failure, a difficulty previously noted in a similar occurrence involving the same engine type in July 2000.