The AIAI issuing the following findings:
- The “sudden technical failure” occurred without any prior indications
- The right hand engine failed with both high pressure turbine (HPT) and low pressure turbine (LPT) disintegrating as soon as take-off power was applied. The failure was contained, with no other damage, and consequently no requirement for the fire engine
- The examination by SR Technic Zurich (SRT) revealed cracks in blades installed during the last overhaul and which were most probably the cause of the engine failure
- A Borescope inspection, which Boeing requires every 1,600 cycles, was carried out 722 flight hours prior to the failure
- The engine failure and shutdown occurred at the beginning of the take-off run. The aircraft is capable of completing its take-off on just one engine (editorial question: even at low speed before sufficient rudder authority has been achieved?)
- From analysis of the recordings and pilot's debriefing, there were no prior indications before the engine failure
- All actions by the crew were efficient and with accordance with requisite procedures
- The crew's reports were incomplete and resulted in discrepancies between the data available to the company and airport authorities respectively
- The tower's handling of traffic, both on the ground and in the air, was correct and efficient
- The assessment of the situation by the various authorities concerned was uncoordinated, resulting in some confusion during the taxiing back
- Runway examination for FOD was carried out correctly
- Definitions of some terms used in English and Hebrew during emergency procedures are not adequate or sufficiently clear
- The reports by the airport authorities were issued only after the event and those by the company somewhat late
- An objective investigation should be conducted by an independent body under supervision of the chief investigator or his representative. In this case, the investigation was carried out by SRT and Chromalloy
- The engine manufacturer, CFM, does not recognize Chromalloy as a repair facility, even though it has FAA certification
- The last repair of these blades, carried out by Chromalloy Nevada, included removal of the coating. However, examination of the damaged blades did not show any signs of reapplication of coating, which would have clearly revealed any cracking
The AIAI reported that the AIAI was notified of the occurrence 40 minutes after the rejected takeoff and immediately dispatched investigators to Ben Gurion Airport to secure the flight data and cockpit voice recorders as well as supervise the removal of the engine from the aircraft and initiate the examination of the engine.
In general the AIAI hwoever complained about the disorganized organisation by the operator in conveying pertinent information to the investigation.
The engine had been built in 1999 and underwent overhaul in April 2009. The engine had accumulated 43,086 flight hours in 12,952 flight cycles since new and 13,626 flight hours in 3,880 flight cycles since overhaul.
Inspection of the right hand engine revealed that the high pressure rotor could be turned freely, the low pressure rotor however had seized. The low and high pressure compressor as well as the combustion chamber were found undamaged, all blades of the high pressure turbine except for the blade roots were missing, all stages of the low pressure turbine showed substantial damage, the magnetic chip detector did not contain any metallic particles.
The AIAI reported that it was impossible to determine the actual cause of the engine failure without detailed investigation and complained that this investigation was carried out by SR Technic in Zurich, who had last overhauled the engine.
The AIAI summarized the investigation report by SRT: The engine failure was caused by a single forceful event, no evidence of fatigue was found.
The AIAI annotated that the report was sent in part to the engine manufacturer who responded that the treatment of the turbine blades had not been in line with the procedures required by the engine manufacturer. Chromalloy Nova, who had carried out the blade overhaul, had not been approved by CFM. The procedure used by Chromalloy is not recognized by CFM.
The AIAI analysed that it was quite normal in the aviation world to use "DER repairs" (Designated Engineer Representative repairs), that permit repairs even by facilities not authorized by the component manufacturer as long as at least one employee of that facility has been certified by the FAA and is a Designated Engineer Representative. El Al as result of the investiation have ceased to involve DER repairs and now send all blades to CFM for repairs/overhaul including all blades that have been treated by Chromalloy.
The AIAI analysed that cracks, that most probably developed a long time prior to the actual engine failure, had not been detected by borescopic inspections. The AIAI therefore wrote, that borescopic examinations have a low reliability to detect blade cracks.
The AIAI heavily criticized the crew resource management following the occurrence reasoning that each of the three pilots on the flightdeck, one captain (55, ATPL, 30,000+ hours total, 22,000+ hours in command) in the left hand seat, a first officer (47, ATPL, 8,500 hours total, 3,500 hours on type) and second captain (no data provided) on the observer's seat, had a different recollection of the occurrence signifying that there had been insufficient communication on the flight deck to develop a common understanding of what had happened. In addition, the communication between crew, tower, dispatch and company maintenance was inadequate for a speedy and efficient dealing with the resulting situation.
One safety recommendation was issued to the operator to introduce a centralized professional body to ensure coordination and dissemination of all relevant information to all relevant authorities. Three safety recommendations were issued to the Israeli Authorities at the airport and Civil Aviation Authority to review safety and crisis management at Ben Gurion Airport, review the procedures at SRT and review communication problems that arose despite standard phraseology used, that however was without precise definition.
The full AIAI report is available here (only in Hebrew)