On Condition Engine Failure

SDR # 20111025010

SDR submitted:

The aeroplane had to land because of a loss of engine power and high vibration. A stuck valve and bent push rod were found on the left-hand rear cylinder (engine was on condition). The customer decided to replace the engine with an overhauled unit. No damage to the aeroplane.

Bent pushrod due to stuck valve

* Bent pushrod due to stuck valve

Bent tube and oil leak

* Bent tube and oil leak

Transport Canada Comments:
Operating a piston engine on condition can certainly offer significant cost savings to the owner. This does however come with certain risks. Extra maintenance can be performed to help mitigate those risks. As mentioned in a previous Feedback article, Avco Lycoming Service Bulletin (SB) 388 and Service Instruction (SI) 1425A provide great information regarding engine operation and valve maintenance. Both are available to the general public on Avco Lycoming’s web site. (http://www.lycoming.textron.com/).

Exhaust Heat Damage

SDR # 20111109004

SDR submitted:

During the 100 hour inspection, cylinder #4 exhaust riser was found bulged at the collector. The bulge is consistent with the direction of cylinder #4 exhaust flow. Upon removal, the exhaust was noticed to be quite thin and appeared to have lost material. A gentle tap with a soft faced hammer easily collapsed the pipe. The engine has individual cylinder head temperature and exhaust gas temperature probes so overheating would be unlikely. Engine cylinder #4 was still serviceable, no other issues were found.

Exhaust pipe showing damage

* Exhaust pipe showing damage

Transport Canada Comments:
Anomalies like this are rare but thankfully it was caught before any serious damage could occur

Propeller Cylinder Gouged

SDR # 20111014002

SDR submitted:

While performing an inspection of the left engine, upon spinner removal it was noticed that the Hartzell propeller counterweights have been touching the propeller cylinder on each side, gouging the cylinder approximately 6.35 mm (0.025 inch) deep. The Propeller was removed and sent to a propeller shop for inspection.

Cylinder showing damaged area

* Cylinder showing damaged area

Transport Canada Comments:
An investigation revealed improperly installed counter weights at some point in the propeller’s history. A careful inspection is required after any maintenance task.

Automated Low Cycle Fatigue Counting

PW 206B &PW206B2 engines

SDR submitted:

The Eurocopter Deutschland Gmbh helicopter Cockpit Display System (CDS) or Central Panel Display System (CPDS) is unable to accommodate engine Low Cycle Fatigue (LCF) counts above 9999 cycles.

However, the Pratt & Whitney Canada (P&WC) engine Power Turbine (PT) disk and Impeller LCF cycle limits as published in the P&WC Engine Maintenance Manual (EMM) are in excess of 10 000 cycles and therefore require more than the present 4 digits available on the helicopter CDS/CPDS cockpit display.

In the event that the helicopter is unable to accurately display the accumulated engine cycles, then this data may be directly obtained from the engine Data Collection Unit (DCU) contained within the P&WC Ground Base Software program. Alternatively, LCF counts can be manually recorded as defined in the P&WC EMM Airworthiness Limitations Section.

Transport Canada Comments:
Transport Canada Civil Aviation recommends that owners and operators familiarize themselves with the above criteria and then comply with P&WC Service Information Letter (SIL) PW200-050 or any later SIL revisions.

Another aging aircraft issue

SDR # 20111003001

SDR submitted:

Left-hand engine was shut down after losing engine oil pressure in flight due to oil starvation. The aeroplane landed safely at the closest airport. A ground inspection revealed that the oil starvation was caused by a swollen engine breather line coupling that caused breather restriction. This restriction caused an internal engine pressure build up and oil escaping through the engine bearing labyrinth seal and accessory gearbox output shaft seal. A negligible oil leak was found on the left-hand engine cowling because a majority of the oil was internally burnt in the engine and could not be detected in-flight by the crew.

The swollen breather coupling, part number 159P10019-75, on the left-hand engine breather line rear section was repaired prior to 1997 and is not the original breather installation. The coupling was replaced. A ground run-up and a flight test revealed no more oil consumption on the left-hand engine.

Both engines breather lines were inspected for defective couplings before maintenance released the aeroplane.

Swollen coupling causing oil loss

* Swollen coupling causing oil loss

Transport Canada Comments:
The importance of proper inspection and attention to manufacturers’ instruction (including their Service Bulletin publications) cannot be understated. In this instance it is likely that all instructions were followed, however the failure still occurred. It is also important that the manufacturer has access to the failed components so as to determine the root cause and develop fleet wide corrective action.

Date modified: