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Information on C-130 wing stress needed

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Information on C-130 wing stress needed

Old 4th Sep 2002, 02:26
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Information on C-130 wing stress needed

As many of you readers know, the aerial firefighting in the USA is and will be making some changes prior to the next fire season. Aircraft wing stress and adverse loads, at low level, has been identified as a problem. One of the cures we are looking at is the use of stress monitoring equipment on many of the aircraft used. In the forum on the C-130 crash in California, there were several post on the use of a computer in Canadian and Royal Air Corps C-130 to record stress. I am gathering information, of any sort to include in a report on this subject. If you have any information, contacts, stories, suggestions, please send to me.
Thanks in advance
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Old 4th Sep 2002, 03:31
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Having flown it for about 2000hrs and that was a while ago, it was imperative that the flight manual limitations be followed. What was it...186 KIAS in turbulance?..and further...a 'g' limitation. I'm getting old and can't remember all the numbers.
It seems to me that inflight stress analysis is giving present data..what is required more is, how can we guard against future wing shed problems...at a predicited flight path.

Unfortunately, equipment like that can't tell what the flight crew are going to do to the aircraft 30 seconds in advance.

An aircraft loaded with retardant or water is perfectly set up for an 'over g' load, if not handled properly. To transition from a 10,000 lb. payoad to an aircraft this is now loaded with just fuel, is a huge weight and load change. Even selective dump door operation, where partial loads are 'pickled-off', are significant in nature.

The major player will be handling technique and following the procedures. The biggest asset is speed control to conserve wing loading in situations like this. And that has to come from flight crew. A device as such won't prevent an overload, although a strain guage that can monitor stress is handy to have.

We were always careful, especially around thunderstorms with our aircraft. A herc driver's eyes would become wide as saucers at the sight of one! There were major wing ADs that made the spar and root area look like reinforced battlefield tank armor.

All the best in your research.
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Old 4th Sep 2002, 06:23
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Well said, 777AV8R:
Your experience matches completely my own one with all the specs for and of electronic supervising/monitoring systems for complex technical systems. These systems are good to analyse the behaviour of systems under specific operational conditions (and to calculate the results "ahead").
But to prevent the above mentioned complex systems from reaching destructive forces there are needed systems like those who are working behind "fly by wire"-systems, programmed with the limits calculated in advance.
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Old 4th Sep 2002, 07:35
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Thanks for the input fellows. I realize a system to prevent the overstressing would be cost prohibitive. What we are looking for, mainly, is a way to monitor the stresses on the wings as an indicator for maintenance. In making drops, in rough air, it is hard to tell how much stress the plane absorbed. In an earlier post on the crash of the C-130 in Calif. it was mentioned that Canada uses about 7:1 flight hours on low level ops. I was under the impression that this information was stored and could be downloaded for analysis of the stresses put on the wings.
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Old 4th Sep 2002, 12:15
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I used to work at Marshalls on the C-130's in the early 80's; now I don't specifically remember seeing anything installed on the aircraft, but I assume that the RAF birds had a simple fatigue meter that would record vertical loads - I know we had them in the little Bulldog trainers, and we had to record what the meter showed and report it back to the a central maintenance information unit, who would then use the data to calculate the airframe life.

It might be worth your while to speak with someone at Marshall Aerospace, as they have built up a substantial amount of data on RAF C-130's over the years - can't guarantee that they would be forthcoming with info or that it would be free of charge, but it could be worth a phone call. Sorry but I don't have any names to point you towards, I've been gone from there a long time.
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Old 4th Sep 2002, 17:56
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The cost effective and I believe most useful way would be to use the stress data to create accurate simulations of what you can and cant do and then train people to get a feel for those limits.
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Old 4th Sep 2002, 22:56
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It would be easy enough to install a strain guage in the critical wing areas on this airplane....the wing root just inboard of the inboard engines and at the wing join just outboard of the outboard engines.
You could feed the data in to a logging device for later download, however; the loading is still a function of 'g' loading on the airplane, so..if my old memory serves me...the 'g' meter is located on the upper corner of the F/O's instrument panel.

The fact of the matter remains in it all...if the drop run is fast, down the side of a hill and the aircraft is acellerating and the load is dropped...there is a huge change in stress.

Another consideration is that in a fire area, the turbulance is awful. The heat generated by the fires, combined with any wind gives you quite a ride. So, there are natural problems aside from induced stresses for this airplane as well.

Remember that LAPES (Low Level Parachute Extraction System) is a low level, steady state scenario. The aircraft is kept at a low constant speed....the altitiude is constant and the load is then extracted. All you need to do is watch the pitch change and altitiude change as the load goes out the door, to see what kind of a difference weight change makes in this aircraft.
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Old 5th Sep 2002, 00:28
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I doubt that strain guages or other "stress monitoring" techniques could identify fatigue cracks. One nasty fatigue crack running 12 inches in length had been found of what was left of the center wing box. This crack was masked by a doubler and would not have been visible during ordinary "stress inspections."

I'm sure that future Airworthiness Directives will mandate the removal of doublers to check for wing box structural integrity and corrosion more frequently. The problem is that it's difficult to quantify inspection intervals; how to correlate "fatigue cycles" into flight hours, given the extreme performance environment of fire fighting operations.
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Old 5th Sep 2002, 00:49
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Well then...maybe the poor ole Hercy bird should just do what it was designed to do....haul medium weight outsized cargo out of shorter unimproved strips, and be flown for what it was originally designed for.
Forest fire supression wasn't in the original plan.
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Old 5th Sep 2002, 01:03
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The B model P3 Orions had a cumulative counting accelerometer fitted in the main electrical load centre just about over the main spar. As I recall, it recorded g counts in .5 increments up to about 4.5 or 5g. After each flight maintenance recorded the new numbers and they were used to monitor the life of the aircraft. No doubt there are better systems out there but maybe Lockheed could help out based on that old system? It was simple and it worked.
cheers
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Old 5th Sep 2002, 10:01
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ExNeptuneDriver

There is a dedicated Hercules web site that C130 aviators frequent. Suggest you post your request there and you may get some more information.

This is the link...... http://pub33.ezboard.com/bc130herculesheadquarters

Cheers

Trash Hauler
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Old 6th Sep 2002, 08:38
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ExNeptuneDriver, I've sent you an email with contact details for the Engineers responsible for the C-130 fatigue program at Marshall's of Cambridge. I spoke to the Head of Test there this morning and he said he would be pleased to discuss the program with you.

Hope this helps.
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