Engines

Engine High Pressure Turbine Failure 

General Electric CF34-8C5
(SDR) # 20121130002

SDR submitted:

While climbing through 8000 feet, flight crew heard a loud noise followed by a yaw to the right. Right engine parameters indicated the engine was spooling down. Flight crew secured the engine, declared an emergency, turned back and landed without further incident. Initial inspection of the engine by local maintenance revealed no damage to the fan blades however there was significant damage to the turbines.

High pressure turbine stage 2 blades

Transport Canada Comments:  

Engine teardown revealed the failure was caused by high pressure turbine blade release. This is a known problem for CF34 engines and is caused by corrosion under the blade platform. Service Bulletins 72-0228 and 72-0242 introduce re-designed blades that address this issue.

Metal In Oil – A Sign of Engine Distress

Pratt & Whitney - Canada PW123
(SDR) # 20130826001

SDR submitted:

At disassembly of the reduction gear box module (for a light overhaul due to metal in oil), three cracks were noted in the 2nd stage spur gear shaft wall. The cracks were originating from the no 15 bearing mating face and propagating forward. The cracks were adjacent to each other approximately 1.52 mm (0.060") apart. There was material breakout at the tooling slot corner. The separated piece of material was picked by the magnetic chip detector in-field. The missing piece is approximately 1.52 mm (0.060") wide, 2.54 mm (0.100") long and 1.27 mm (0.050") deep.

Bull gear with clear crack indication and missing piece

Transport Canada Comments:  

Metal found in oil systems and chip detector indication is an indicator of engine wear or distress. This can be a precursor to catastrophic failure. These conditions must be investigated further to determine the source. Manufacturer’s instructions regarding metal in oil found in maintenance manuals, Service Bulletins (SB’s) and Service Information Letters (SIL’s) should always be followed.

Cracked Gearbox Housing

Garrett TFE731-2-2B
(SDR) # 20131210001

SDR submitted:

During a visual inspection of the engine gearbox, it was noted that the oil filter housing assembly lower mounting stud ear was cracked. The corrective action taken was to replace the aft gearbox housing case.

Damaged Gearbox Housing

Transport Canada Comments:  

Transport Canada Civil Aviation would like to raise awareness of this defect to operators of TFE731 engines. Due to the location of the stud (six o’clock position) and the length of the housing, the possibility of accidental damage is high. The cause in this case is not known; however it could have been the result of corrosion (or casting inclusion), a past over torque or perhaps an accidental overload or impact damage during installation or shipping. Whatever the case, maintainers are urged to be cautious when working on complex systems and always follow manufacturers instruction.

Broken Fire Loop Wiring Found, Potential In-flight Shutdown Avoided!

General Electric, CF34-3B1
(SDR) # 20121101004

SDR submitted:

During routine maintenance, the left hand jet pipe loop “A” was found unserviceable. Troubleshooting found that the engine fire detection wiring harness was broken at the pylon connector. The fire detection and fire protection wiring harnesses were replaced. This defect, if unnoticed, might have resulted in an in-flight engine shutdown due to a false engine fire or jet pipe overheat warning.

Exposed fire loop wires near cannon connector

Transport Canada Comments:  

This was a good find by the maintenance team who were doing the inspection (in particular considering the defect’s location in the pylon). As aeroplane fleets in Canada and abroad age, there will likely be more of these issues discovered.

Cracked Engine Combustor

Garrett TPE331-10UGR-514H
(SDR) # 20121107004

SDR submitted:

The crew reported that when the power lever was advanced, the engine could only achieve 40% torque. The take off run was aborted and the aeroplane returned to the hangar. A maintenance crew performed a quick visual inspection of the engine and performed an engine ground run with the cowlings open. Startup was noted to be longer than expected and when the engine achieved ground idle, the technician sitting in the cockpit noticed an orange glow from below the engine. Stop procedures where carried out and the engine was shutdown.

A detailed visual inspection confirmed a large 25.4 to 30.48 cm (10 to 12 inch) long crack in the combustion liner. The engine was removed and replaced.

Engine plenum (combustion section) with a visible 25.4 to 30.48 cm crack

Transport Canada Comments:  

The plenums on these engines are operated ‘on condition’. The type certificate holder (Honeywell) has issued Service Bulletin 72-2178 (Combustion Section –inspect combustion case assembly) that recommends it be accomplished at each scheduled fuel nozzle inspection and/or replacement. Transport Canada Civil Aviation recommends that operators familiarize themselves and comply with this service bulletin.

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