CT155205 Hawk - Epilogue

Report / February 4, 2009 / Project number: CT155205 - D Category

Location: 4 Wing Cold Lake, Alberta
Date: 2009-02-04
Status: Investigation Complete

At approximately 2015 UTC on 4 February 2009, a formation of two Hawk aircraft conducting a low altitude air-to-surface tactics training mission commenced a hard right turn into a simulated bandit aircraft positioned 2 miles to the right of the formation. During the hard right turn, as the pilot of the occurrence aircraft selected full throttle, a series of bangs and a machine gun-like noise was heard in the cockpit followed by engine vibrations. The pilot immediately commenced a climb, retarded the throttle to idle and terminated the exercise. The pilot determined that the engine was in an overtemp condition and carried out the emergency checklist procedure by performing the immediate relight drill. The relight was uneventful except for a significant vibration that sounded mechanical in nature, that developed when the throttle was advanced to more than 88% RPM. The pilot selected 85%, continued a shallow climb and steered the aircraft towards 4 Wing Cold Lake. The pilot flew a straight in Forced Landing procedure and landed the aircraft without further incident.

Post flight inspection revealed that a single Low Pressure Turbine (LPT) blade was missing from the engine. It was determined the blade failed below the root-to-blade “platform” due to a pre-existing fatigue crack that grew in size through normal engine use until the blade finally failed. 

At the time of this occurrence there was a known issue with fatigue cracking of the LPT blades in this area and the Original Equipment Manufacturer (OEM) had implemented corrective action to resolve the issue. However, due to quality control issues on the part of the OEM, non-compliant LPT blades were inadvertently introduced into the occurrence aircraft's engine.

The OEM has since changed their quality control processes and a vendor audit was carried out to verify blade quality. Blade life, originally 2,000 hours, has also been reduced to 1,000 hours until such time as the subjective aspects of the OEM's inspection processes have been made more objective.

There have been no documented blade failures since this occurrence.

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