Engines

Engine nonpreservation contributing factor in fatal crash

Subject:

The following text is taken from the Transportation Safety Board of Canada, Aviation Investigation Report A07C0114. The full text is available at:

www.tsb.gc.ca/eng/rapports-reports/aviation/2007/index.asp

“The pilot of the Eurocopter AS 350 B-2 helicopter was ferrying the helicopter, with one passenger. An electronic flight notification was sent by the passenger to another member of his survey company indicating an arrival time of 1905 Central Standard Time. When the helicopter did not arrive, the survey company initiated emergency procedures at 1945. Debris was found the following day in Bernick Lake, approximately 25 nautical miles (nm) southwest of Points North Landing. The helicopter was found at the bottom of the lake with extensive damage and both occupants sustained serious injuries at water impact, but drowned when the helicopter sank.”

Investigation revealed the following:

“The engine (Honeywell LTS101-700D-2, serial number LE-46040C) was removed from the airframe and sent to the TSB Engineering Laboratory for teardown…

The number two bearing was examined visually and localized areas of corrosion were noted. Rub marks were found in the corrosion and the pit edges on the rollers. Inner ring was burnished and plastically deformed, indicating that the number two bearing was operated for some time subsequent to the formation of the corrosion pits. The number three bearing was destroyed.

The engine was a rental engine and had been installed on 17 June 2007. At the time of installation the engine had zero time since overhaul and 6728 hours since new. At the time of the accident, the engine had flown an additional 74.5 hours. There were no reports of engine magnetic chip-detector actuation in the period before the accident. The engine had been in storage and was not operated during the period from 28 May 2004 to 06 June 2007. Both the number two and number three bearings examined were in the engine during this period of time.

The corrosion had to occur when the engine was idle for a period of time and was not stored in accordance with the manufacturer’s procedures. Because both bearings were installed in the engine and as there are no records indicating that the engine had been preserved in accordance with the maintenance manual from 28 May 2004 to 06 June 2007, the corrosion likely occurred during this period”

Image of failed # 3 bearing

* Image of failed # 3 bearing

Transport Canada Comments:
Regardless of how insignificant a maintenance action or procedure may seem it could have major consequences at a future point in time. In the above example, procedures were not followed resulting in a latent condition that led to a catastrophic failure.

When an appliance or part is received for installation, one might assume that the part is serviceable (as long as it has the appropriate documentation). It can be difficult or impossible to know how long it has been in storage or if the manufacturer’s storage procedures were followed. As aviation professionals, we must be aware of all operating requirements for the equipment we maintain.

Inspect New Parts Prior to Install

PRATT & WHITNEY CANADA, PT6A27
SDR # 20110705002

SDR submitted:

When an apprentice engineer received an oil filter Parts Manufacturer Approval (PMA) part number 7579522AM, equivalent to Pratt & Whitney Canada part number 3024084 or 3033315, from the company’s store department, he noticed that the fine cone shaped screen was missing from the end of the filter, that is first inserted into the oil filter housing. This is the first filter that the company has found with the cone screen missing from that type of oil filter. The remaining stock of oil filters in the store’s department were inspected and found serviceable.

Oil filter without cone screen

* Oil filter without cone screen

Oil filter with cone screen

** Oil filter with cone screen

Transport Canada Comments:
Excellent job on the part of the apprentice to discover this defect! This is a good example of remaining vigilant.

Worn Throttle Lever Spline

TELEDYNE CONTINENTAL IO-240-B
SDR # 20110512001

SDR submitted:

During cruise flight, the pilot tried to reduce the power to idle, when he discovered that he was unable to, he returned to home base. An uneventful landing was accomplished using mixture idle cut-off. Upon inspection of throttle linkage, it was discovered that the splines on the throttle lever and shaft were worn. It is speculated that the lever was installed on the shaft with splines misaligned. After an undetermined amount of time, the splines may have realigned themselves with some ‘play’ in actuation, causing additional wear to continue until such a time that the lever would rotate on the shaft without rotating the lever. Originally, Teledyne Continental Motors (TCM) had no splines on the lever, however it was made from a softer material (bronze), allowing it to ‘set’ in place on the throttle shaft.

Transport Canada Comments:
A simple task likely carried out many times in the past, and then a small design change created the potential for an accident.

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