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Boeing halts test flights of 737MAX over engine issue

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Boeing halts test flights of 737MAX over engine issue

Old 11th May 2017, 04:21
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Boeing halts test flights of 737MAX over engine issue

"Boeing is suspending test flights of a new commercial airplane because of possible problems with a key engine part.

The company said Wednesday it was notified of a potential manufacturing-quality issue by CFM, which makes the engines that are going on the Boeing 737 Max.

Boeing says it has not experienced any issues with the low-pressure turbine discs during on-ground testing and test flights of the new plane.

Boeing says it still plans to begin deliveries of the plane later this month, and production will continue. The Max is designed to be a more fuel-efficient version of the workhorse 737, Boeing's most popular commercial plane."

Engine issues holding up a new aircraft? Well now.

Last edited by underfire; 11th May 2017 at 04:39.
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Old 11th May 2017, 05:54
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The report I heard today implied that there was an inspection (borescope, I assume) where they could determine if an engine had a suspect disc. If true, the delay will be days - not weeks or months - to inspect the engines prior to flight (and delivery).
Obviously if an engine is found to have a suspect disc it'll have to be replaced and shipped back to CFM to have the disc replaced...
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Old 11th May 2017, 07:46
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Reading between the lines of this report in the Seattle Times:

Boeing grounds 737 MAX planes over quality issue with engine

the issue appears to be specific to Safran-produced engines and not those manufactured by GE.
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Old 11th May 2017, 15:41
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I'm not a fan of the use of the word "ground or grounding" applied to a maintenance/inspection program. I prefer to use that wording only where a regulatory certificate has been revoked.

What I interpret here is that a manufacturer (GE/Boeing) inspection program has been decided to detect and remove a suspect part from the fleet. Until such time as this is completed, they don't intend to accept an increase in risk nor to transfer the problem to a their customers.

This problem will likely be resolved soonest rather than later as long as the estimated number of inspections or negative results do not increase.

no news is good news
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Old 11th May 2017, 16:30
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If the current partnership between GE & Safran is still the same as the old, a simplified description of responsibilities would be: GE is responsible for the core of the engine (compressor combustor & HP turbine) and Safran is responsible for the fan, LPT and gearbox. Then, modules are exchanged so engines are assembled and tested in both France and the US. I have heard the problem has to do with a manufacturing defect in one of the LPT disks involving one of two suppliers that Safran use for this disk. Don't know for sure this is a fact or not...
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Old 13th May 2017, 07:53
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The issue is apparently related to the forging used for the Safran LPT supplied by a particular vendor. Seems like a precautionary action by Safran. That LPT disc is likely a fracture critical part, so the forging used should have full traceability. Odd that this issue was not found during manufacture of the LPT given the rigorous QA procedures normally used with fracture critical components.
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Old 13th May 2017, 14:13
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Odd that this issue was not found during manufacture of the LPT given the rigorous QA procedures normally used with fracture critical components.
No QA is 100% reliable, thus the part itself must have the in-service time tolerance for the traces left behind. This appears to be more of a zero-time fleet management cost issue than a large safety risk so early in the program. I would be far more concerned if there were potential tens of parts in service that had accumulated thousands of flights
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Old 14th May 2017, 07:56
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Modular logistics

Given the modular design of the CFM56, LEAP, and virtually all modern engines, after the initial surge, there would seem to be little benefit in shipping whole engines back to manufacturers for the limited teardown required for this inspection.

I'd expect that the GE crew in Seattle could remove, ship, and swap LPT modules quickly; This places less risk to the rest of the engine hardware. (I'm speaking of ground shipping damage, of which I've seen more than a little)
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