Boeing is facing fresh crisis after another airline found cracks in a 737 plane

https://www.businessinsider.com/boeing-737-ng-qantas-finds-crack-airlines-inspect-fleets-reports-2019-10

by hourislate • 7 years ago

110 45 7 years ago

tyingq6• 7 years ago

Not excusing anything about MCAS, but the "cracks in an aluminum airframe" thing is a VERY normal and established cycle/process. Well known and a normal thing. This news piece is just journalistic piling on to hot news.

There is "no news" here.

wil4213• 7 years ago

Just to add, here’s a forum discussion from 5 years about about aircraft cracks in general. People are saying they are common in all aircraft even during manufacturing.

https://www.airliners.net/forum/viewtopic.php?t=773937

vultour• 7 years ago

Except this is not about cracks in the airframe but in a component that is certified for significantly more cycles than when the cracks are being found. If these were benign FAA wouldn’t have released an AD to inspect and repair them.

msbarnett3• 7 years ago

The issue here isn’t about airframe cracking in general, which is fairly normal and expected in the lifetime of the plane, but cracking in the “pickle fork” in particular— which is abnormal, as these are not normally expected to crack during the plane’s lifetime according to Boeing’s own modelling and expectations — engineers had rated these at 90,000 cycles, the effective lifetime of the craft.

This appears to indicate (yet another) QC and manufacturing deficiency (Boeing already is dealing with other such issues with the 787 and KC-46).

The claim by OP that this is normal because aluminum cracking is normal is really wide of the facts. This part was engineered to withstand the forces it experiences for a certain timespan, and the fact that some now appear to be failing in less than one-third of the lifespan the materials engineers expected it to calls into question whether Boeing or a subcontractor is failing to engineer these components to spec.

dhimes• 7 years ago

Then why are they grounding the planes? Are they fools?

tyingq6• 7 years ago

No. An individual airline or two didn't handle things right. Boeing didn't screw up, and it's completely unrelated to the whole MAX thing. Similar issues exist for Airbus. Aluminum cracks.

rkangel• 7 years ago

Metal fatigue is a reasonably well understood phenomenon, that is managed by the aircraft inspection cycle.

The actual crack appearance rate diverging from the modelled appearance rate at design time is a potential worry and indicates an issue somewhere along the line. How bad that issue actually is requires more investigation. It's a complex situation because metal fatigue is a statistical process, so you don't know if the cracks you've found are the best case or worst case.

runeb• 7 years ago

You are assuming they are relatively normal hairline cracks. They are grounding planes, so the cracks reported here might be different from that. There does not seem to be enough information to conclude sensationalist news.

tyingq6• 7 years ago

Airlines with many more 737's handled it correctly. Not saying it isn't a crisis. Just saying it's an airline specific crisis, not a Boeing crisis. That's the piling on bit.

tooop• 7 years ago

Except for the fact that the these cracks are in the "pickle fork" - a part that is supposed to last the lifetime of the plane without cracking.

mumblemumble• 7 years ago

Or perhaps it's news that's just missing a few details.

Cracking and wear and tear on the structure might be normal, but it sounds like the issue here is that the 737NG airframes are showing signs of wear and tear much faster than expected.

inferiorhuman4• 7 years ago

Not excusing anything about MCAS, but the "cracks in an aluminum airframe" thing is a VERY normal and established cycle/process.

Cracks can be a normal and expected thing. These parts were designed to last the lifetime of the airframe (around 90,000 cycles) and are failing in under 30,000 cycles.

This raises eyebrows for two specific reasons: 1.) Boeing was already installing subpar parts (edit: not pickle forks) from Ducommon in the 737 NG 2.) The wings fall off if the pickle forks fail completely.

This news piece is just journalistic piling on to hot news.

MCAS isn't the only fire Boeing is fighting right now (they're also battling poor quality control with their KC-46 and 787 lines among other things). Some guy on PPRuNe is claiming that the pickle fork problem was just improper manufacturing[1], which when put in context would make it appear as if Boeing has some major structural problems with its organization.

1: https://www.pprune.org/showpost.php?p=10595986&postcount=258

chopin• 7 years ago

These parts were designed to last the lifetime of the airframe

Can these be replaced? If they have the expected lifetime of the airframe they might not be serviceable. Out of curiosity: can these cracks be repaired other than replacing the part?

throwaway57522• 7 years ago

Yes, but it's very long cycle failures at low frequency, and people suspect it's because of additional stress caused by winglets. Winglets reduce drag and save fuel, it's an important change. It may have been very difficult to predict and test this failure. And most importantly, the FAA and Boeing are handling it properly.

notfromhere2• 7 years ago

That's because when they merged with McDonnell Douglas, MD executives got the top spots in Boeing, so their shitty culture transferred over to the new company.

The long-standing joke is that MD took over Boeing with Boeing's money

samastur• 7 years ago

Yes and I am sure all these airlines know this too and yet they are grounding them even though it costs them real money. It seems these airlines are less comfortable with the kind of cracks they noticed or the speed of their growth, but maybe you have a first hand knowledge why they are just wrong.

jseliger• 7 years ago

https://www.perell.com/blog/boeing-737-max

also HN discussion https://news.ycombinator.com/item?id=21304277

Engineers seem to have lost control of the company.

mikece• 7 years ago

I have to wonder how seriously Southwest and Alaska Air are reconsidering their relationship with the Boeing and the 737. Rumor is that SWA might be considering a switch to Airbus.

https://www.chicagotribune.com/business/ct-biz-boeing-737-ma...

amq• 7 years ago

If only they could quickly get high quantities immediately, I'm sure they would switch in a heartbeat.

cptskippy• 7 years ago

Part of Southwest's competitive advantage has been that the vast majority of their aircraft use the same platform which simplifies training of crew and maintenance of aircraft.

Switching to Airbus would necessitate complete retraining of thousands of people and would increase costs at least in the short term substantially.

hourislate• 7 years ago

I just want to let you know that there are concerns with Airbus also. Article in the Oct/19 issue of Flight International Magazine the following:

It is worthwhile mentioning that the Airbus A320 wing was designed 35 years ago for a 70t platform, and has remained the same on all versions, from the A318 through to the A321.

While unchanged, the wing has seen a steady loading increase: to 83t on the first A321, then 89t and 93.5t, and is finally expected to go up to 101t on the A321XLR. This increased wing loading has meant higher take-off speeds, reaching close to the maximum tyre speed limits, and a lower safety margin at altitude – in other words, a tighter “coffin corner”, and lower stability protection.

Where and when would the civil aviation authorities stop manufacturers from creeping ever so closer to the performance limits of a product?

JKCalhoun• 7 years ago

Where and when would the civil aviation authorities stop manufacturers from creeping ever so closer to the performance limits of a product?

You hit the nail on the head. These manufacturers and the airlines are compromising safety for dollars: trying to put more people on a plane than it was designed for.

alexis_fr• 7 years ago

You are saying that Airbus is close to the limits. It is immensely different than Boeing being the certifier of its own planes, and having two major failures already on record with hundreds dead (the Duncommon airframes and the MAX).

Merrill• 7 years ago

It’s the rear spar pickle forks which crack The cracks form in the outer chord of the rear pickle forks (Figure 1) and the behind lying safety straps, just where they pass from the rear spar of the center wingbox to the fuselage side of the aircraft, Figure 2.
This is also the area where the fuselage side has a cutout to let the main landing gear strut fold in with its attached wheel.
The combination of a wing center-wingbox pushing wing and landing gear forces into the fuselage in an area where the fuselage has a large cutout for the folded main landing gear makes this area complex regarding forces and how these work the parts during flights.
The stress spectrum in the area can also have been affected by the later fitting of winglets on the NG, not foreseen in the original design of this area.
Winglets change the pressure distribution of the wing to a distribution spreading further outboard, by it increasing the wing root bending moment.

https://leehamnews.com/2019/10/08/boeings-737-in-another-pic...

So Boeing also made changes from the 737 to the 737 NG without complete reanalysis of how the changes affected all the parts?

throwaway57522• 7 years ago

I don't think that's the case, and I don't think that's what the link you provided says. 5% of the pickle forks are showing cracks, after a minimum of 20k flights.

It's probably an incorrect analysis (maybe the didn't account for enough cycles in fatigue/failure testing given the extra load from the winglets, maybe the extra load is not well understood and they had bad assumptions). I am very harsh on Boening on how they handled the MAX development and crashes. The pickle fork situation is unfortunate but seems like it is likely an honest error that was caught in the right way and is being dealt with in the right way. I fly 737s frequently, too.

the_duke• 7 years ago

Reportedly a replacement costs 250_000$ and takes two to three weeks.

Far from ideal, and potentially very expensive for Boeing if they are liable, but considering a unit cost of 100M not that dramatic.

How the Max development continues seems much more important.

Enginerrrd• 7 years ago

And bragged about how they increased production, yes.

ozi• 7 years ago

Data on this is already out, as the FAA only gave planes with > 30000 cycles 7 days to inspect and 3 days to report findings after inspection.

810 planes were inspected; 38 of them have cracks (4.6%) and have been grounded until fixed. They are not airworthy. Only two of these were in the US.

The other 772 planes will have to undergo inspection after each additional 3500 cycles.

https://www.youtube.com/watch?v=HprNMrjK6_I

Boeing is facing fresh crisis after another airline found cracks in a 737 plane

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