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ASN Wikibase Occurrence # 74533
Last updated: 1 July 2020
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Date:04-JUL-2008
Time:
Type:Silhouette image of generic B743 model; specific model in this crash may look slightly different
Boeing 747-306
Owner/operator:Saudi Arabian Airlines
Registration: HS-VAC
C/n / msn: 23056/587
Fatalities:Fatalities: 0 / Occupants:
Other fatalities:0
Aircraft damage: Minor
Location:Jeddah-King Abdul-Aziz International Airport (JED) -   Saudi Arabia
Phase: Initial climb
Nature:Ferry/positioning
Departure airport:Jeddah-King Abdul-Aziz International Airport (JED)
Destination airport:Jakarta
Narrative:
On July 4, 2008 a Saudi Arabian Airlines Boeing 747-300 experienced an uncontained failure of its No. 1 engine, a General Electric CF6-50 turbofan, during initial climb after takeoff from the King Abdul-Aziz International Airport (JED), Jeddah, Kingdom of Saudi Arabia. The non-commercial flight was repositioning the airplane from JED to Jakarta, Indonesia for maintenance, including maintenance to the No. 1 engine due to degraded power. The flight crew reported that they reduced the No. 1 engine thrust following takeoff after noticing fluctuations in its exhaust gas temperature and fan speed (N1) indications. According to the captain, the fluctuations continued during the initial climb, and about one minute later, at about 1,100 feet above ground level (AGL), the engine's low oil pressure warning illuminated and the oil quantity indicator read zero. The flight crew shut down the engine, dumped fuel, and returned to the airport, where an uneventful landing was accomplished. No injuries were reported. Post-flight inspection of the airplane found that the aft end of the No. 1 engine was missing, and that the airplane's left wing and flaps were damaged from impact penetrations.

The liberated components were recovered about 2 miles from the departure end of the runway. Examination of photographs of the No. 1 engine and the recovered parts indicated that the engine's LPT S3 disk had separated at the forward spacer arm, and that all components aft of the separation were missing.

The liberated parts were submitted to GE's materials lab in Evandale, Cincinnati Ohio for examination with NTSB oversight. Metallurgical examination of the LPT S3 disk found that it had separated at the disk forward spacer arm-to-rim forward face fillet radius. Fatigue cracks on the inner surface initiated from sites typically spaced 0.1 inch to 0.2 inch apart around the circumference of the spacer arm. The fracture surfaces exhibited features consistent with high stress, high-cycle fatigue, termed high amplitude fatigue (HAF). The features indicated that, once initiated, the cracks propagated rapidly through the spacer arm thickness and joined to form a single circumferential crack, resulting in disk separation. The freed aft portion of the LPT rotor accelerated, resulting in penetration of the engine case and high-energy uncontainment.
A post-incident video borescope inspection (BSI) of the engine's high pressure turbine (HPT) found three HPT stage one (S1) blades over a nine-blade sector were missing material, equivalent to the loss of about 1.8 blade airfoils.

The investigation was initially conducted by the General Authority of Civil Aviation (GACA, Kingdom of Saudi Arabian, and was handed off to the United States on April 11, 2009. The Kingdom of Saudi Arabia participation continued as the State of Occurrence.

FAILURE MODE

This localized material loss resulted HP rotor unbalance. The unbalance-induced synchronous vibration forces interacted with the engine low pressure (LP) rotor system through the No. 5 bearing support and excited a 1-diameter bladed-disk mode response in the LPT stage 3 (S3)disk.

The resonant amplitude of the alternating stress experienced by the disk will result in bending loads that exceed the material endurance limit, and HAF cracks will initiate along the circumference of the LPT S3 disk forward spacer arm. Once initiated, the cracks propagate rapidly through the spacer arm thickness and the individual cracks join to form a single circumferential crack, resulting in a 360 degree separation. The freed aft portion of the LPT rotor accelerates, resulting in engine case penetration and the release of high-energy debris, as disk fragments and all engine components aft of the LPT S3 nozzles are liberated.

Sources:

https://ntsb.gov/ntsb/brief.asp?ev_id=20081219X16535&key=1
http://www.ntsb.gov/recs/letters/2010/A-10-098-101.pdf

Safety recommendations:

Safety recommendation A-10-100 issued 27 May 2010 by NTSB to FAA
Safety recommendation A-10-101 issued 27 May 2010 by NTSB to FAA
Safety recommendation A-10-98 issued 27 May 2010 by NTSB to FAA
Safety recommendation A-10-99 issued 27 May 2010 by NTSB to FAA


Images:

Photo of HS-VAC courtesy AirHistory.net


Sharjah - International (OMSJ / SHJ)
13 April 2005; (c) Streep

Revision history:

Date/timeContributorUpdates
27-May-2010 23:30 harro Added
05-May-2012 06:22 gerard57 Updated [Total fatalities, Other fatalities, Source, Narrative]

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