
Boeing is facing fresh crisis after another airline found cracks in a 737 plane - hourislate
https://www.businessinsider.com/boeing-737-ng-qantas-finds-crack-airlines-inspect-fleets-reports-2019-10
======
Merrill
>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...](https://leehamnews.com/2019/10/08/boeings-737-in-another-pickle-
part-2/)

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

~~~
throwaway5752
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
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.

------
tyingq
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.

~~~
inferiorhuman
_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](https://www.pprune.org/showpost.php?p=10595986&postcount=258)

~~~
throwaway5752
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.

~~~
inferiorhuman
_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. _

Cracks have been found in NGs both with and without winglets, so that is
almost certainly not the issue at hand.

------
mikece
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...](https://www.chicagotribune.com/business/ct-biz-
boeing-737-max-southwest-earnings-20191024-avtvpfzm4rahrd5kms63jybdpe-
story.html)

~~~
hourislate
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
> 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.

------
ozi
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](https://www.youtube.com/watch?v=HprNMrjK6_I)

