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US Air Force pauses flights for over a hundred C-130s over ‘atypical’ cracking

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Re: US Air Force pauses flights for over a hundred C-130s over ‘atypical’ cracking

#11

Post by WalterBright »

xeromal wrote: post #9
salusbury wrote: post #7

Earlier quoted context omitted.

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

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

"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.

Re: US Air Force pauses flights for over a hundred C-130s over ‘atypical’ cracking

#13

Post by 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.

Re: US Air Force pauses flights for over a hundred C-130s over ‘atypical’ cracking

#14

Post by 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...

https://en.wikisource.org/wiki/NTSB_accident_summary_for_N13...

https://aviation-safety.net/database/record.php?id=20020617-...

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

https://fenix.tecnico.ulisboa.pt/downloadFile/395138005046/C...

Re: US Air Force pauses flights for over a hundred C-130s over ‘atypical’ cracking

#15

Post by HeWhoLurksLate »

xeromal wrote: post #9
salusbury wrote: post #7

Earlier quoted context omitted.

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

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

One of the mechanics on an aircraft carrier I was on (briefly, I'm not military) said that if they find even one nut on the ground, they'll isolate and ground every single plane they think might be affected.

Re: US Air Force pauses flights for over a hundred C-130s over ‘atypical’ cracking

#16

Post by na85 »

redis_mlc wrote: post #13

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 u…

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

Re: US Air Force pauses flights for over a hundred C-130s over ‘atypical’ cracking

#17

Post by dsfyu404ed »

na85 wrote: post #16
redis_mlc wrote: post #13

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 u…

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 mig…

Here's a picture showing context.

https://media.defense.gov/2017/Jun/19/2001764865/-1/-1/0/170...

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