
US Air Force pauses flights for over a hundred C-130s over ‘atypical’ cracking - Jerry2
https://www.defensenews.com/air/2019/08/08/air-force-pauses-flight-ops-for-more-than-a-hundred-c-130s-after-atypical-cracking-found/
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redis_mlc
Despite the other comments, this is a very serious issue. In fact, it's one of
the most serious that can affect an aircraft, and the serial numbers involved
are really grounded until inspected (8 hours) or fixed (1-2 months - ie.
rebuilt wing.)

Smaller airplanes work around this by having a "massive spar" with no joints
that goes entirely through the fuselage.

In the case of larger planes a "center wing box" can be used, like the newer
C-130 serial numbers that are not affected.

Source: commercially-rated airplane pilot who's familiar with military jet
design.

~~~
na85
Yep, it's a serious issue but as I said in my other comment, managing things
like this is a relatively routine part of aircraft maintenance. I've been
forwarded a preliminary risk assessment that puts the overall risk as
"medium". The severity of the problem is obviously catastrophic but the
probability of a failure occurring is so low ("extremely remote") that the
overall airworthiness risk is not as high as one might think.

Every Hercules has a centre wing box, not just the new ones, and the "rainbow
fitting"[0] is the part that attaches the centre wing box to the outer wing
boxes. There is a rainbow fitting on the upper and lower surfaces of the box.

It looks like in this case the problem affects aircraft with more than 15000
equivalent baseline hours on their CW rainbow fittings, which is what's being
inspected.

Source: am aerospace engineer with Hercules experience

[0] the rainbow fitting is a curved surface designed to transmit loads between
two mating parts. It's called out as 99A in this pic:
[https://ibb.co/tbhcdS9](https://ibb.co/tbhcdS9)

~~~
dsfyu404ed
Here's a picture showing context.

[https://media.defense.gov/2017/Jun/19/2001764865/-1/-1/0/170...](https://media.defense.gov/2017/Jun/19/2001764865/-1/-1/0/170613-F-EI321-0013.JPG)

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dfeojm-zlib
This reminds me of a (possibly unrelated) incident involving a C-130A that
broke up in flight while serving as a fire-fighter water-bomber. It turns out
the original material 7075-T6 wore too quickly and should've been the revised
material 7075-T7531. Even C-130B's through C-130E's weren't fully-upgraded
with the recommended engineering changes.

[http://www.iasa.com.au/folders/Publications/Legal_Issues/Pea...](http://www.iasa.com.au/folders/Publications/Legal_Issues/PearblossomC130.html)

[https://en.wikisource.org/wiki/NTSB_accident_summary_for_N13...](https://en.wikisource.org/wiki/NTSB_accident_summary_for_N130HP)

[https://aviation-
safety.net/database/record.php?id=20020617-...](https://aviation-
safety.net/database/record.php?id=20020617-0)

Here's a structural analysis of the C-130H wing design:

[https://fenix.tecnico.ulisboa.pt/downloadFile/395138005046/C...](https://fenix.tecnico.ulisboa.pt/downloadFile/395138005046/C-130%20Artigo.pdf)

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na85
Ordering inspections such as this is common airworthiness practice - only
noteworthy here because of the number of aircraft involved.

It's a bit misleading to say they've been grounded; typically what you'd issue
is a special/out-of-sequence inspection to be carried out before next flight,
which I suppose to someone outside the industry amounts to the same thing but
there's semantic difference.

These aircraft are being inspected to ensure they are airworthy and conform to
the approved type design; they're not really being "grounded" which would
imply they're _not_ airworthy or not compliant with the type design (which is
the case for e.g. the MAX 8).

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notus
I'm not sure atypical is the correct word here. This was a problem when I was
in the Air Force 13 years ago...

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jessaustin
_The decision to pause operations and conduct inspections was made after a
single C-130 was found with the lower center wing joint cracks, said AMC
spokesman Maj. Jonathan Simmons._

One is less than a hundred. Title doesn't explicitly state that all those
aircraft had cracking, but still seems a bit misleading in a clickbait sort of
way.

~~~
ambicapter
Headline is pretty clear. If one aircraft shows atypical damage, they'll
ground all the others just in case they're similarly affected. This probably
entails inspections and maybe even pre-emptive fixes (depending on the
resolution for the cracked aircraft). So a crack on one of them is just as bad
as a crack on all of them.

~~~
slashink
You’re right. Aviation comes down to being a numbers game. If one aircraft
exhibits variances, the problem needs to be understood and if bad fixed before
it has a chance to cause a real issue.

~~~
salusbury
Think that this is indicative of the state of the US Air Force as a whole?

~~~
xeromal
I think seeing cracks on ONE plane and deciding to review all of them speaks
to a pretty high standard.

~~~
WalterBright
"But the risk posed by the issue — that the wing could become dislodged from
the aircraft — was so serious that the Air Force decided to move forward with
inspections for all planes that could potentially be impacted."

I would think that's a minimum standard, not a pretty high one. Having wings
fall off is embarrassing, expensive, deadly, and nobody wants to testify
before Congress as to why they let that happen.

