Engine Failure Due To Overhauled Idler Gear

Garrett, TPE331-11U
(SDR) # 20120924006

SDR submitted:

A maintenance report indicated that the right hand engine flamed out approximately 40 miles from the runway. Landing was carried out without incident. Troubleshooting revealed a failure of the engine internal drive of the fuel pump.

Idler gear housing with multiple safety pinning holes drilled

View of idler gear out of position

Transport Canada Comments:  

This engine failure was caused by a loss of drive to the fuel pump and fuel control unit which ultimately shut the engine down. The reason for the loss of drive was the idler gear bushing had backed out of the housing assembly. This caused the gear to migrate out of position and loose contact with the other gears in the system. This unit had been overhauled and the bushing replaced (likely more than once) in its service history. It is not known how many times this procedure had been accomplished on this particular unit (it is not a serialized part and as such is not tracked).

As engine fleets age (airframes as well) maintainers and overhaulers must take extra care to look for unusual conditions and wear that the designer may not have been able to predict when the product was first envisioned. Aging aircraft issues are and will continue to be a great challenge to everyone involved in the aviation industry.

Cracked Bleed Air Line

Garrett, TPE331-12UAR-703H
(SDR) # 20120720001

SDR submitted:

When ground testing an engine for an unscheduled propeller dynamic balance, the right-hand (R/H) engine flexible p3 bleed air hose cracked at the flange and separated from the engine case. This caused abnormal exhaust gas temperature values, loss of power, pressurization system failure (only from R/H engine supply) and engine inlet anti-ice failure.

The flexible hose assembly became loose and chaffed on the R/H engine fire extinguisher spray pipe causing its failure. Hot air coming from the broken flange burned the electrical wires causing failure of the R/H engine computer, the fluctuation in the temperature indicator and caused the engine cowling seals in zone 1 to melt.

Hose assembly cracked at flange

Transport Canada Comments:  

There is a post Service Bulletin line assembly available (part number 13711543L401) that addresses this problem. (Service Bulletin 21-JM 7797)

Cracked Power Section Duct

Pratt & Whitney Canada, PT6A-34
(SDR) # 20120618007

SDR submitted:

During a routine inspection, a crack was noticed on the exhaust duct between the "b" flange and "c" flange of the power section.

Power section exhaust duct

Transport Canada Comments:  

The fact that this was found during a routine inspection would indicate that the crack initiated and propagated very quickly. It serves as a reminder to pay close attention when conducting any inspections however ‘routine’ or cursory they may be. Good job spotting this one considering the crack was located on the top of the engine on a DHC-6 aeroplane. This is not the easiest location to access!

Failed P2.8 Check Valve

Pratt & Whitney Canada, PT6C-67C
(SDR) # 20120803005

SDR submitted:

During a 50 hour inspection on an Augusta AW139, a piece of the P2.8 check valve was found in the engine compartment of the #2 engine.

The flapper valve is Post-Pratt & Whitney Service Bulletin 41042. This was introduced as a result of a similar problem with the Pre-Service Bulletin valves.

A failed P2.8 check valve

Transport Canada Comments:  

Service Bulletin 41042 introduced a more robust check valve with improved hinges and contact area for the butterfly. It is obvious that there is still a potential for valve malfunction (due to the hostile environment in which the valve is located). Transport Canada Civil Aviation recommends maintainers inspect this area as per maintenance instructions and any time access permits.

Odor In Cabin Caused By Glycol Ingestion

Pratt & Whitney Canada, PW120A
(SDR) # 20130110001

SDR submitted:

On descent, the flight crew noticed a strong burning plastic smell in the cockpit. An emergency was declared and they donned their oxygen mask. Some electrical systems and engine bleeds were turned off. After a few minutes the smell dissipated. The aeroplane landed without further incident. A maintenance team was dispatched to the outstation and determined that the contamination source originated from the #1 bleed system. The aeroplane was ferried to a maintenance base with the #1 bleed system selected off. Further troubleshooting revealed traces of glycol contamination at the inter compressor case (ICC) plenum, also an unidentified particle was found at the ICC drain. The drain was cleaned, engine ran, environmental system tested and test flight successfully conducted before returning the aeroplane into service.

De-icing procedure on a Dash-8 aeroplane Picture by Photographer Chris Schock

Transport Canada Comments:  

With the return of the icing season, crews are cautioned to follow the recommended procedures when de/anti-icing their aeroplane. Ground crews are also reminded to use caution while carrying out their duties and avoid spraying de/anti-icing fluids into the intake area of aeroplane’s engines. Aircraft manufacturers publish procedures for de-icing and anti-icing their aeroplanes.

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