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27th February 1987

Updated: Feb 27, 2022

A British Aerospace BAe-146-200A (BAe-146) was operating a scheduled flight from Los Angels International Airport (California, USA) to Reno/Tahoe International Airport (Nevada, USA) onboard 83 passengers, 2 cabin crew and 2 pilots. The take-off and climb were uneventful, and the crew had settled in for the cruise section of the flight at Flight Level 260, while the cabin crew started their service.

Allied SIgnal ALF 502 engine (Source: V2 Aviation)

Approximately 40 minutes after takeoff a loud noise was heard and the #3 engine (Right-hand inboard) had suffered an uncontained engine failure. Blades of the number 4 power turbine had been ejected from the engine also penetrating the pressurised fuselage. None of the occupants of the cabin was injured, Besides the damage to the fuselage, aircraft systems were not affected. A Mayday call was made to ATC and a diversion to Fresno Airport (California, USA) was initiated. An uneventful landing was made.

An investigation by the National Transportation Safety Board was launched and the failed engine was examined. The uncontained engine failure was obvious, but what had caused it?

Allied SIgnal ALF 502 engine (Source: V2 Aviation)

The engine was examined and metallic (ferrous) contamination was found in the oil system, Furthermore, it was found that the engine oil had been bypassing the engine oil filter (a 5 micron filter) for at least 40 days. Prior to the oil filter being bypassed a Filter Impending Bypass Indicator will activate when the pressure difference between inlet and outlet pressure of the filter is 13 PSId. The Filter Bypass Valve will will open at a differential pressure of 17 PSId. During this time no corrective action was taken by the airline's maintenance department. In the three months prior to the accident the engine oil and the oil filter had been changed three times. It was determined during the investigation that the contaminated oil system had contributed to the failure of the number four turbine ball bearing,

as a result of reduced lubrication or lack of lubrication.

This led to an overheating and a subsequent failure of the bearing, causing an Overspeed of the turbine and the structural failure of the turbines, shedding its blades.

A PSA BAe-146-200 (Source; Public Domain)

The NTSB report (available by clicking here) concluded that the probable cause of the uncontained engine failure was: Failure of the maintenance department to adequately examine the engine lubrication system when contamination was detected.

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