Wednesday, August 8, 2012

NTSB narrows down GEnx-1B engine issue to fan mid shaft fracture on Air India 787

In a press release issued today, the NTSB said that a fan mid shaft had fractured at the forward end of the shaft.  The NTSB is still trying to understand the root cause of the fracture which led to parts being ejected from the rear of the engine.  The cause can be either a manufacturing flaw in this particular engine or (and highly unlikely) a design flaw. 

Currently there are about 80 GEnx engines that are in service on both the 747-8 and the 787.  Boeing is going to deliver another GEnx powered 787 to Ethiopian Airlines on Monday and thus far there is no indication that those plans have been or are going to change.  This is the first time that there has been a failure of significance on the GEnx engine and given the operating (albeit short) history of the engine, there is no reason to believe that there is a safety risk of using the engine in commercial use at this point.  I believe Boeing will continue deliveries of the GEnx powered 787 going forward with deliveries this month to Qatar Airways, Ethiopian and Air India. Here is the test of the NTSB press release:

NTSB provides factual update on Boeing 787 engine failure in South Carolina

August 8, 2012

WASHINGTON - The National Transportation Safety Board continues its investigation of the July 28, 2012 contained engine failure that occurred on a Boeing 787 Dreamliner during a pre-delivery taxi test in Charleston, South Carolina. A contained engine failure is a specific engine design feature in which components might separate inside the engine but either remain within the engine's cases or exit the engine through the tail pipe. This design feature generally does not pose immediate safety risks.

Last week, the NTSB sent an investigator to the scene to gather information on the incident and subsequently launched a full investigation into the cause of the failure, led by NTSB Investigator-in-Charge, Mr. David Helson.

On August 1, 2012, a team of experts from the NTSB, FAA, Boeing and GE Aviation specializing in engine systems and metallurgy traveled to a GE facility in Cincinnati, OH to disassemble and examine the failed GEnx engine. GE is the manufacturer of the GEnx engine. The parties to the investigation have been extremely cooperative in assisting NTSB personnel in its review and assessment.

As a result of the investigative work to date, the NTSB has determined that a fan mid-shaft on the failed GEnx engine fractured at the forward end of the shaft, rear of the threads where the retaining nut is installed. The fan mid-shaft is undergoing several detailed examinations including dimensional and metallurgical inspections.

The GEnx engine is a newly designed aircraft engine. It is a "dual shaft" engine, meaning that one shaft connects the compressor spool at one end to the high pressure turbine spool at the other end. A longer "fan shaft" connects the fan and booster in the front of the engine to the low pressure turbine in the back.

The cockpit voice recorder and flight data recorder, which is a combined unit on the 787 Dreamliner, was transported to the agency's Recorders Laboratory in Washington, DC for processing and readout. Both recordings captured the event and analysis is ongoing.

Moving forward, investigators will continue the detailed examination of the engine and metallurgical analysis of its components. The investigators have also begun reviewing the engine manufacturing and assembly records.

This investigation is ongoing. The information released today is factual in nature and does not include any analysis. Additional factual information may be released as it is developed.

On a semi-related matter, MAtt Cawby got a picture of ZA288 (LN 53, N20904) for United Airlines at Everett's compass rose.  He says that first fligth of this airplane is imminent.

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