Pre-flight cracks in 787 engine

http://www.ntsb.gov/news/2012/120927.html

by kghose • 14 years ago

59 23 14 years ago

more info - http://www.flightglobal.com/news/articles/ntsb-urges-groundi...

(this is serious because - as far as i can tell - this engine has a 330 minute ETOPS rating http://www.geaviation.com/press/genx/genx_20120308.html http://en.wikipedia.org/wiki/ETOPS which means that a twin engine plane (like the dreamliner) can fly 5.5 hours (the number in the report above) from "safety" (eg over the atlantic), so if one engine fails the other must continue working for that time. if the problem is common then that is not so reasonable an assumption...)

(not all dreamliners are affected; rolls royce also provide engines)

marklabedz2• 14 years ago

A little more info on ETOPS and the challenges created by multiple similar failures within a small population...

There are two parts to ETOPS (tongue in cheek "Engines Turn or Or People Swim")..The first is the certification to design standards, including flight testing. The second, and perhaps more crucial element, is the operations/procedures certifications. In the first stage, the entire system (engines, airframe, fuel system and everything else) is evaluated as a comprehensive whole. Essentially, you're looking to eliminate single points of failure.

The second part is arguably more important as it deals with the statistical failure rates. The assumption is that a modern jet (turbofan) engine is highly reliable. As the basis of such procedures, multiple, similar failures are worrisome. An airline must have approved ETOPS operations to fly routes requiring ETOPS (a certified airplane is necessary but not sufficient). Common operational procedures include not replacing both engines at the same time, servicing similar fuel system components together, etc. Basically, avoid the possibility of introducing a single point of failure into otherwise redundant systems.

cstross• 14 years ago

Single points of failure can emerge but hopefully they're rare. The classic case is something like British Airways Flight 38 at Heathrow in 2008:

http://en.wikipedia.org/wiki/British_Airways_Flight_38

(By sheer good luck and good piloting skills the crew were able to make it over the runway threshold after both engines lost power during final approach: injuries and a hull loss, but no deaths. Problem was a design flaw in the fuel oil heat exchangers, only triggered by unusual meteorological conditions on a long flight. Both engines had the same design issue and were drinking the same fuel ...)

ktsmith• 14 years ago

> The assumption is that a modern jet (turbofan) engine is highly reliable.

I was really surprised to find how true this was. One of my first jobs was working in a manufacturing plant for a company remanufacturing various parts of various jet engines (rebuilding blades, putting new airfoils into damaged vanes etc). The joke on the floor for new employees was that once you saw how badly damaged the engines were by the time they got to us you'd never want to fly again. It was also very interesting to see how much FAA regulation was involved in the manufacturing/remanufacturing process and how often people tried to skirt those rules to save parts due to how expensive they are.

hga• 14 years ago

I'm glad they're paying attention to single points of failure in maintenance: echoing cdtross, I can remember reading about a flight taking off from Miami, I think it was, going over water, where in pretty short order all engines failed hard due to their all having been incorrectly serviced in the same way, something to do with oil seals. Fortunately it wasn't far out when this happened and it had enough energy to make it back safely to the airport.

omegant• 14 years ago

That's a big failure for engines that have been ground tested only. I can't understand how they didn't check (I mean fresh engines just off reasembly line for inspection) them before. This is more or less normal with new models but maybe not this way.

jjm• 14 years ago

Sounds kind of crazy to not test engines under real world conditions. What I mean is not be able to test it under conditions found during actual work (found in the air) prior to release.

lmg643• 14 years ago

another reason not to fly on the 787 until it's been in use for several years...

marklabedz2• 14 years ago

Its not just the 787 that uses these engines.

EDIT: ...and not all 787s use these engines.

photorized• 14 years ago

What's unsettling is that the failure is in the inherently reliable component (shaft).

eduardordm• 14 years ago

I experienced such failure on a plane I was flying (CFM56). I don't remember what the exact problem was, but it had something to do with a batch of materials they used in the construction of some blades. A whole lot had to be replaced. It was my 138th hour flying as capt.

This is a new engine, without figuring what causes those fractures, NTBS should ground them. I bet they already know what it is.

My father (37 year of flying) always tell me stories where engines in the industry had vibration resonance problems that caused fractures in the whole airplane those engines never ended up flying.

sbierwagen• 14 years ago

As every Boeing employee reliably complains, every time a story like this comes out, Boeing doesn't make the engines. They're GE engines. It's a GE problem. They're just mounted to a Boeing plane.

When Bridgestone makes bad tires that fall apart while driving, the headlines are not "tires on Ford car explode, kill family", it's "Bridgestone tires burst into flame, kill busload of orphans".

And, as andrewcooke points out, not every 787 flies with GE engines, since Rolls Royce is also a vendor.

bobbles• 14 years ago

If those bridgestone tyres happened to be the ones that came WITH the car as you purchased it, there would likely be strong backlash against Ford.

gvb• 14 years ago

They did. http://en.wikipedia.org/wiki/Firestone_and_Ford_tire_controv...

riffic• 14 years ago

In my mind Boeing bears just as much responsibility for the quality missteps of their vendors.

The key is integration - Boeing is responsible for the testing and when problems are discovered, they need to be brought to the attention of GE.

rgwright• 14 years ago

GE is not a vendor to Boeing, they are both suppliers to the airline. The standard setup for both commercial and military sales is for the customer to buy the engines and airframe separately. Both the engine company and airframer collaborate in the integration testing, with the engine company being primarily responsible for the engine.

alphasierra• 14 years ago

For those of you not following these events closely: the 747-8 and the 787 (both new) both utilize a very similar engine from GE (the GEnx).

The GEnx 1B (787) failed in July this year and kicked off an investigation that is trying to determine if there is an engineering or manufacturing problem in the parts that connect two shaft pieces together to form the main shaft in the engine.

The GEnx 2B (747-8) failed in early September this year and the initial investigation is not complete.

This memo confirms that the 747-8 and the 787 failures are NOT related.

That being said, the NTSB wants to pull the ETOPS certificate from the -1B engines which would effectively ground the majority of the 787 fleet (the 787 is optimized for long flights which would be majority over water/out of gliding range and the GEnx has the widest install base on the 787).

The FAA has indicated that they will take a watching brief for the time being.

Pre-flight cracks in 787 engine

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