Fox has a video link off of the home page that shows the crash as filmed by a local news crew. Not sure how to properly post that link, though.
The guys on the C-130 never had a chance.
The video shows the aircraft finishing a run over the fire. It appears to bank from slightly right to level, then both wings seem to simultaneously fold up at the point where they blend into the fuselage.
The aircraft sheds its wings and becomes a lawn dart.
No fire is apparent until after the wings separate and that is only a flash. The fuselage and empennage stay intact all the way down.
I don’t think I’ve ever heard of wings coming off in what should have been a moderate, low speed manuever, especially in such a tested and much used aircraft type.
Pilots, C-130 types, any idea what might have happened? Could turbulance from the fires be severe enough to snap a main spar?
Fire-suppressant drops can involve deceptively hard manuevers, diving into, and sharply climbing out of, canyons and narrow valleys. Combine that with a heavy load of suppressant, and sharp up (and down) drafts from both the ridges and the fires themselves, and you have an enviroment guaranteed to be hard on an airframe. I suspect that the aircraft in question was also fairly old.
Speculation:
I suspect that the main spar was already begining to fail before or during pull-out, and even though they’d dropped their load of suppressant, the wings were already begining to fail… It just didn’t become apparant to the remote observer until after the drop.
I have no idea about this as I am not an aeronautic engineer but is it in any way odd that both fell off at the same time? I could see one or the other wing going but both simultaneously seems weird. Of course, there may be nothing weird about it whatsoever. Just curious…
That was very bizarre. I know C130 wings are replaced due to fatigue, and the rainbow fittings as well, but I’m not exactly sure what the interval is. But like W-a-M said, both simultaneously seemed very unusual.They’re actually “bolt on” wings, and it looks like that’s where they came off. I’ve chopped up a few 130’s in the past, and they’re built like tanks, so for them to come unglued like that is really strange.
From my understanding, the C-130 in question was an old KC-130 refitted for the job. Structural4 stress seems to be the culprit here, as even ‘moderate’ stress on a fractured spar could cause a catastrophic failure on such a ‘heavy’ plane.
It did happen after the plane dropped its load, maybe the wing-loading change caused a small fracture to go critical?
Makes me wonder about the older P-3s that have been mod’ed for firebomber duty. I’d think they have a higher (per sq/ft) wing loading than a firebomber C-130, but don’t know if they’ve had fwd and aft wing box bulkheads (I know that’s probably not the right term, but I’m an AW) replaced.
WAG here but has a wind sheer (sp?) been overlooked? If you follow the way that the wings fly off and the decent of the debris and the fuselage it “twists”. My assumption is that wind went up on one side and down on the other.
What Tranquilis said. Forest fires have huge masses of rising and falling air around them from the unequal heating. Flying through them is hellaciously turbulent. Plus, these aircraft are often flying at very high gross weights with their slurry loads, and there’s a pretty violent pitch-up when the load is dropped. All of this puts continual stress on the airplane.
Why both wings at once? Two possibilities. The first is that the spar failed right at the center section, which carries the heaviest load. The second is that the failure of one wing induced a failure of the other one. You see that a lot with tail failures - the failure of the horizontal stab often results in the immediate failure of the wings as the plane pitches forward violently.
My guess is that the spar failed in the center, and this failure will result in an airworthiness directive mandating the inspection of spars on other C-130’s in similar service.
The YC-130 first flew in 1954. The KC-130F first flew in 1960. It’s been around a long time. I wouldn’t know for sure, but I believe that all of the C-130s in civilian hands are “surplus”. That is, they were probably flown until the military decided they weren’t worth fixing. Many of the C-130s flying probably saw service in Vietnam in the 1960s.
In short, civilian C-130s are probably old and tired.
But airplanes are not like cars. Old airplanes have a tendency to be modernized and improved. Most of the Cessnas and Pipers you see flying around were built in the 1970s, but they’re still quite serviceable. So the Navy or Air Force decides to send the airframe to the boneyard. Someone buys it at an auction and spends more than the military would to make it airworthy. When things break, they’re fixed. When components are worn out, they’re replaced. But of course the basic airframe is pretty much original. This is the same airframe that has been subjected to a hard military life and, in the case of the fire supression aircraft, continue to lead strenuous lives in the violent air currents Sam Stone mentioned.
Aircraft are inspected every 100 flying hours when they are used commercially, and every year whether they are flown frivately or for profit. The inspections are intended to keep things like catastophic structural failure from happening. But stresses can build up rapidly in an aircraft flying this kind of mission. It’s possible that metal fatigue occurred that was not detected – may not have been detectable – between inspections.
In such a case, a catastrophic structual failure may occur.
And again, this is pure speculation. But I think Tranquilis and Sam Stone may be on the right track.
The crash aircraft was a C-130A. I don’t know when production stopped on the -A model, but I’ll bet it was built in the early 1960s and I wouldn’t be surprised if it saw combat.
The local news also reported that the crash aircraft had recently undergone repairs to a “crack in the wing”. I assume they mean a crack in the wing spar, attachment, or carry-through structure.
None the less, I also think the proposed failure modes are pretty plausible. I will also put forward a couple other items that crossed my mind.
Taking into account that these planes are built specifically for this type of extreme service and (to my knowledge) there have been no other incidents like this in their history, the repair and inspection history needs to be looked at very closely.
I suspect that their are some critical fasteners/bolts/pins that tie the wing halves together. I would be looking closely at these. If they were improperly tightened, safety wired, or otherwise reinstalled incorrectly, things could get ugly really fast. Also, if any of these were replaced with items that were not the correct grade of metal it could be bad. Many times fasteners are available in different grades (hardness and/or tensile strength) that are otherwise identical. It should be easy to identify problems in this area by looking at the wreckage.
Also, the footage I saw did not show the entire pass over the fire. It could be there was nothing at all wrong with the plane. The pilots could have made a mistake on entry. If they came in too steep and/or too fast they might have simply exceeded the safe loading specs of the plane pulling up to level on the drop run. Cutting it close to the edge coupled with a strong updraft at the wrong time could make it pretty easy to overstress the airframe. I don’t suppose there are flight data recorders on these fire planes? It would be nice to be able to see the last few minutes of g- loading on the airframe. Of course, a mistake that could have done the damage to the plane could have been made several (or less likely) many flights ago.
One last thing I noticed in the video. With the short clip I had to look at it, it was hard to discern, but… it appeared the plane had not really started a pull up manuever after the drop run when the wings left. The pilots could have known by this point they were in trouble already. Going along with what I said above about doing the damage on entry to the drop pass, they might have heard/felt something give coming in and were trying to baby the craft back to field. Something giving that would be very obvious to the pilots would not necessarily be noticable on video at all.
I suspect this will be figured out pretty quickly though. The video should really help investigators know what to examine first in the wreckage. I will be extremely suprised if the examination uncovers some until now hidden flaw in the design of an aircraft that has performed so well for so many years.