Serious incident Fokker 100 OE-LVE, Sunday 6 November 2016

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Date:	Sunday 6 November 2016
Time:
Type:	Fokker 100
Owner/operator:	Austrian Airlines
Registration:	OE-LVE
MSN:	11499
Year of manufacture:	1993
Fatalities:	Fatalities: 0 / Occupants:
Other fatalities:	0
Aircraft damage:	Minor, repaired
Category:	Serious incident
Location:	over Serbia - Serbia
Phase:	En route
Nature:	Passenger - Scheduled
Departure airport:	Wien-Schwechat International Airport (VIE/LOWW)
Destination airport:	Pristina Airport (PRN/LYPR)
Investigating agency:	CINS
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
Austrian Airlines flight OS769, a Fokker 100, was en route at FL350 when the crew felt a sudden vibration accompanied by unfamiliar sounds.
Immediately after the onset of the vibrations, there was an indication of increased vibrations in engine No. 1, followed by an additional indication of problems with engine No. 1, and then the illumination of the engine failure warning for engine No. 1 (Eng Fail 1). The crew performed the shutdown procedure for engine No. 1 and continued flying with a single engine.
The crew decided to divert and land at the nearest airport, Belgrade Airport.

After notifying air traffic control and declaring an emergency (Mayday-mayday), the crew was given landing priority and conducted a safe landing at the airport. During the landing, passengers seated near the windows in the rear left section of the aircraft observed sparking and flashes coming from engine No. 1.

Direct Cause:
The investigation determined that the direct cause of the serious incident was the fracture of fan blade number 17 on engine No. 1 (serial number 17602).

Contributing Causes:
A contributing cause of the serious incident was the excessive use of DFL lubricant intended to reduce friction between the root of the blade and the groove in the disk where the blade sits. This led to axial displacement and increased axial load, resulting in the loss of the blade retainer and movement of the blade, which caused uncontrolled vibration of the blade set.

Accident investigation: