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ASN Wikibase Occurrence # 247551
Last updated: 6 February 2021
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Date:01-DEC-2005
Time:
Type:Silhouette image of generic B763 model; specific model in this crash may look slightly different
Boeing 767-3Q8ER
Owner/operator:Skymark Airlines
Registration: JA767B
C/n / msn: 27617/722
Fatalities:Fatalities: 0 / Occupants: 90
Other fatalities:0
Aircraft damage: Minor
Category:Serious incident
Location:Kagoshima Airport -   Japan
Phase: Take off
Nature:Passenger - Scheduled
Departure airport:Kagoshima Airport
Destination airport:Tokyo International Airport
Investigating agency: JTSB
Narrative:
The Boeing 767-300 JA767B, operated as Skymark Airlines scheduled Flight 306, took off from Kagoshima Airport at 16:45 (Japan Standard Time, UTC+9h) on December 1, 2005. Immediately after takeoff, vibration started on the right engine , and at about 16:48 the fire warning on the right engine was activated. The flight crew shut down the right engine and returned to the Kagoshima Airport at 17: 04 for a successful single engine landing.
Of the total of 90 persons on board, consisting of a pilot in command (PIC), a co-pilot, nine flight attendants, and 79 passengers, no one was injured. The aircraft suffered minor damage. After takeoff, the grass area alongside the runway caught fire.

PROBABLE CAUSE
It is estimated that this serious incident was caused as follows: When the Aircraft became airborne, one of the 2nd stage high-pressure turbine blades of the right engine was fractured which had had considerable fatigue crack, leading other blades to be fractured which caused vibration to the right engine from unbalanced rotation, and the vibration further caused fracture of the fuel supply tube #6 inside the shroud can, moreover, the retaining ring at the end of the shroud can was dislodged by the pressure of fuel injected in the shroud can as well as by the engine vibration causing the fuel to leak, then the fuel was ignited when it contacted the hot section, and resulted in a flame in the engine designated fire zone.
Although the exact cause of the fatigue crack found in the turbine blade could not be determined precisely, it is considered possible that the following factors were combined and contributed:
-because the TA (turnaround) radius of the cooling air passage inside the blades was smaller, the stress was prone to concentrate on that area and thereby it became prone to cause cracks, and later, the cracks progressed due to low-cycle fatigue,
-because sulfur was detected from the rupture surface, the blade was in the condition that crack came by hot corrosion.
-thinner LE passage wall of the shank created the high stresses on the entire blades.
The most probable cause for the fracture of the fuel supply tube was the excessive loads placed on the tube due to vibrations from the engine imbalance.
As for the fire warning which did not activate immediately until a significant area of the core cowl had been melted, it is estimated that it was because the flame was directed to the area where no fire detector element was routed.

Sources:

JTSB

Accident investigation:
cover
  
Investigating agency: JTSB
Status: Investigation completed
Duration: 3 years
Download report: Final report


Images:

Photo of JA767B courtesy AirHistory.net


Tokyo - Haneda International (RJTT / HND)
12 October 2003; (c) Alastair T. Gardiner


Photo: JTSB

Revision history:

Date/timeContributorUpdates
06-Feb-2021 16:49 harro Added

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