Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Wingnutt on May 23, 2008, 11:05:00 AM
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I was wondering about some of the extreme "gamey" manuevers you see on here, for example people rapidly going from pulling a very high positive g to a very high negative G over and over again.
seems like even pretty robust aircraft would suffer rapid and severe structural fatigue from such abuse.. slamming a 109 from +6 g to -5 or within less than 1 second.. seems like alot of stress on the airframe.
thoughts?
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I was wondering about some of the extreme "gamey" manuevers you see on here, for example people rapidly going from pulling a very high positive g to a very high negative G over and over again.
seems like even pretty robust aircraft would suffer rapid and severe structural fatigue from such abuse.. slamming a 109 from +6 g to -5 or within less than 1 second.. seems like alot of stress on the airframe.
thoughts?
and on the pilot too
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I was wondering about some of the extreme "gamey" manuevers you see on here, for example people rapidly going from pulling a very high positive g to a very high negative G over and over again.
seems like even pretty robust aircraft would suffer rapid and severe structural fatigue from such abuse.. slamming a 109 from +6 g to -5 or within less than 1 second.. seems like alot of stress on the airframe.
thoughts?
We talking limit stresses or fatigue? They're two different animals. Besides, even low cycle fatigue occurs over thousands or even tens of thousands of cycles. Since you get a brand new plane everytime you up, no biggie.
Cap1 is right, it's the driver who's taking the real beating.
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I think that in ww2 if you took a real 109 up, pulled back on the stick till you hit 6gs then immediately slammed it all the way forward as hard as you could.. till you pulled g's far beyond red out, then pulled back again to max positive g.. over and over again.. I cant help but think that would damage the aircraft almost immediately.
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Are the stories of P-51's coming back with bent wings an urban myth or are they grounded in some sort of truth?
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Truth. High speed dives could permanently deform the wings. The Mustang had a few problems with structural failures. Due to a variety of reasons, it had a propensity to shed its wings or tail.
I once read that the Mustang was only designed to be in combat for 16 weeks. After that it would be considered war-weary. Aluminum is light, but it isn't the best metal for handling repeated stress. Once aluminum is overstressed, it will be weaker at the point where it was bent. Steel doesn't have this sort of memory.
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Truth. High speed dives could permanently deform the wings. The Mustang had a few problems with structural failures. Due to a variety of reasons, it had a propensity to shed its wings or tail.
I once read that the Mustang was only designed to be in combat for 16 weeks. After that it would be considered war-weary. Aluminum is light, but it isn't the best metal for handling repeated stress. Once aluminum is overstressed, it will be weaker at the point where it was bent. Steel doesn't have this sort of memory.
Source?
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I once read that the Mustang was only designed to be in combat for 16 weeks. After that it would be considered war-weary. Aluminum is light, but it isn't the best metal for handling repeated stress. Once aluminum is overstressed, it will be weaker at the point where it was bent. Steel doesn't have this sort of memory.
I won't be suprised if the American fighters were built for in average 100-200 hours. However, there were plenty of P-51Bs and Cs in service when the hostilities ended.
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Source?
In Robert Johnson's book "Thunderbolt", he talks about how (his?) Thunderbolt had wrinkled wingtips after pulling out of a compression dive.
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If within limits the rapid stick pump to G limit wouldn't break the airplane -- the first time you did it. <G> Everytime you pull G you stress the airframe. With time the structure is weakened -- hence the War Weary status of aircraft. Same reason the aerobatic pilots today "retire" their airplanes after a while -- they're worn out.
Aquashrimp - Minor point about the Mustang: The high speed dive didn't damage the airplane the loads induced in recovery from the dive were the problem. The wing loss problem on the Mustang came from something with the gear. I don't remember the exact details, something about no uplocks on the gear, doors sagging.
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Source?
"P-51 Mustang". I don't have the book here in front of me. However, it was about 350 pages of first hand accounts of Mustang pilots and ground crews. Made in the 70s I believe. Awesome book.
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"P-51 Mustang". I don't have the book here in front of me. However, it was about 350 pages of first hand accounts of Mustang pilots and ground crews. Made in the 70s I believe. Awesome book.
Thanks, see if I can pick it up.
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I know there was an account of a jug having a bomb rack malfunction causing a 500 pounder not to release, he had to pull out of the dive with it still attached and as a result bent the wings, something like 6 inches at the tip.
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I know there was an account of a jug having a bomb rack malfunction causing a 500 pounder not to release, he had to pull out of the dive with it still attached and as a result bent the wings, something like 6 inches at the tip.
Hmmm. I can't see how having a bomb hung would bend the wing. Wings get bent due to the load concentration at the fuselage -- all the weight in the middle type of thing. A bomb at mid span is supported on both sides, to bend at the bomb rack one part of the wing would have to pull harder than the other part it would seem.
I can see how you would become distracted because of the hung bomb, try to pickle it off and get way to low and have to pull really hard to avoid the earth -- now that could easily bend a wing.
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You don't see how having a 500lb bomb under six or seven g's of force could overstress and bend the metal of a wing? The force of the bomb is acting like a fulcrum, bending the wing where it attaches to the fuselage.
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You don't see how having a 500lb bomb under six or seven g's of force could overstress and bend the metal of a wing? The force of the bomb is acting like a fulcrum, bending the wing where it attaches to the fuselage.
I think what he was saying is the wing would bend at the fuselage, NOT at the rack itself as the post would lead you to believe.
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You don't see how having a 500lb bomb under six or seven g's of force could overstress and bend the metal of a wing? The force of the bomb is acting like a fulcrum, bending the wing where it attaches to the fuselage.
No I don't but I'm finding it hard to explain it to you in writing. (I'm a pilot, I use my hands to talk <G>) Google "zero fuel weight". That should explain what I'm getting at.
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Well the airplane would live the pilot would be so confused that he landed in Berlin instead of London on a trip to paris.
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Remember that the wing bends upward. It isn't bent downward by the weight of the bomb.
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You don't see how having a 500lb bomb under six or seven g's of force could overstress and bend the metal of a wing? The force of the bomb is acting like a fulcrum, bending the wing where it attaches to the fuselage.
The pylon the bomb was attached to would let go before the wing failed.
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I think the problem was that the pylon wouldn't let go. IIRC, he landed with it and it finally plopped off on the runway and cause damage to the aircraft as it did so.
Now remember that people aren't actually pulling the kind of maneuvers you're seeing, especially any kind of snap or instant maneuver. What is a quick, within-physics turn gets bent by the lagtime of the internet and the code made to dampen that lagtime into an instant 80 or 90 degree turn. This is where the term "stick stirring" came into effect. With the new dampening code and the old "don't move your controls so rapidly" effect, it's been reduced. Before those measures, you were able to slap your stick around in all directions (like stirring a pot) and you'd see tiny movements on your screen. As the opponent's front end tried to foresee where your plane was headed, your aircraft would rotate and spin in mid-air.
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I think the problem was that the pylon wouldn't let go.
No, like Colombo mentioned, the wing is designed (under +G) to sustain loads that would cause the wing to bend upwards. Having the bomb pylon out at mid-wing actually helps with +G loading. The issue is one regarding the strength of the pylon attach points (the actual hardware that attaches the bomb to the pylon, and the pylon to the wing). The pylon would fail before the wing would fail, unless the pylon was designed to sustain higher limit loads than the wing (which wouldn't make sense from an engineering standpoint). Airspeed limits are designed to ensure the wing doesn't rip itself off as a result of lifting loads that exceed the wings ability to resist the upward bending moment caused by lift. G-limits are the same, as the increased weight of the fuselage would make the wings bend upwards. -G loads are the only loads that would cause the wing to bend down.
If anyone has seen the video of that CDF C-130 crashing while pulling out of a retardent drop run, you'll notice the wings rip off in an upward motion.
That being said, I personally think the airspeed limitations as they pertain to ordnance aren't reflected well in-game. All of the speeds listed below can be exceeded in-game without damaging a P-47N.
(http://i125.photobucket.com/albums/p61/stonewall74/P-47NSpeedLimitations.jpg)
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The pylon the bomb was attached to would let go before the wing failed.
Not always true. One of the few cases I know of where Spit wings folded was doing a high G pullout of a slope bombing run when the 500lb bomb failed to release. It was a Mk IX and the wings folded.
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If memory serves, the problem with the Mustang's wings stemmed from airflow at high speeds causing the wheel well cover to partially deploy. The resulting forces wrenched the wings off.
I remember reading a short article about this several years ago. An American pilot stationed in Italy had seen a number of fatal crashes in which a Mustang had lost its wings while pulling out of a dive. An engineer from North American was sent to his base to investigate. When the pilot explained that the crashes occurred when the P-51 shed its wings, the engineer snorted derisively and stated that, "It was impossible to pull the wings off a Mustang."
No sooner had the words left his mouth, than they heard the twin "thumps" of a Mustang shedding its wings. The engineer asked, "What was that?" The pilot responded, "It just happened again." The wingless wreckage smashed into the ground within the perimeter of the airbase. The pilot was killed.
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I've read that story too Shuckins.
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Not always true. One of the few cases I know of where Spit wings folded was doing a high G pullout of a slope bombing run when the 500lb bomb failed to release. It was a Mk IX and the wings folded.
Doesn't the Spit carry it's bomb under the fuselage? If so, all weight is concentrated at the wing root. Over G is over G
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If memory serves, the problem with the Mustang's wings stemmed from airflow at high speeds causing the wheel well cover to partially deploy. The resulting forces wrenched the wings off.
I remember reading a short article about this several years ago. An American pilot stationed in Italy had seen a number of fatal crashes in which a Mustang had lost its wings while pulling out of a dive. An engineer from North American was sent to his base to investigate. When the pilot explained that the crashes occurred when the P-51 shed its wings, the engineer snorted derisively and stated that, "It was impossible to pull the wings off a Mustang."
No sooner had the words left his mouth, than they heard the twin "thumps" of a Mustang shedding its wings. The engineer asked, "What was that?" The pilot responded, "It just happened again." The wingless wreckage smashed into the ground within the perimeter of the airbase. The pilot was killed.
I met an old Mustang pilot that was involved in some of the testing done in England to troubleshoot the wing shedding problem. In one of his dives the gear sagged but the wings stayed on -- although badly damaged and deformed. They were able to determine cause and a fix was worked up.
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Stick stirring in a Yak 55M:
http://www.vimeo.com/1028164
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Stick stirring in a Yak 55M:
http://www.vimeo.com/1028164
you cant be serious.
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No, like Colombo mentioned, the wing is designed (under +G) to sustain loads that would cause the wing to bend upwards. Having the bomb pylon out at mid-wing actually helps with +G loading. The issue is one regarding the strength of the pylon attach points (the actual hardware that attaches the bomb to the pylon, and the pylon to the wing). The pylon would fail before the wing would fail, unless the pylon was designed to sustain higher limit loads than the wing (which wouldn't make sense from an engineering standpoint). Airspeed limits are designed to ensure the wing doesn't rip itself off as a result of lifting loads that exceed the wings ability to resist the upward bending moment caused by lift. G-limits are the same, as the increased weight of the fuselage would make the wings bend upwards. -G loads are the only loads that would cause the wing to bend down.
If anyone has seen the video of that CDF C-130 crashing while pulling out of a retardent drop run, you'll notice the wings rip off in an upward motion.
That being said, I personally think the airspeed limitations as they pertain to ordnance aren't reflected well in-game. All of the speeds listed below can be exceeded in-game without damaging a P-47N.
(http://i125.photobucket.com/albums/p61/stonewall74/P-47NSpeedLimitations.jpg)
Kudo's Stoney. :aok Somebody actually get's it. Is it safe to say you actually know what a Shear & Moment Diagram is?
You don't see how having a 500lb bomb under six or seven g's of force could overstress and bend the metal of a wing? The force of the bomb is acting like a fulcrum, bending the wing where it attaches to the fuselage.
Wing-mounted stores actually reduce the wing root bending moments during pull-outs. Where stores on the wing become an issue is on recovery, where a hard landing can produce nasty negative bending moments at the wing root (or the wing fold mechanism on carrier planes.
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dont know if its pertinent, but the instance i cited about the jug getting its wings bent upwards, the bomb was on the center rack, not a wing pylon.
at any rate this thread has drifted..
Im talking about a clean aircraft, and the transition from high positive to high negative Gs at a rapid rate.. I.E slamming the aircraft from +6g immediately into perhaps -4G in less than 1 second, and the effects of doing such an extreme maneuver rapidly over and over would realistically have on a real WW2 aircraft.
its a give in the the pilot couldent handle it by a long shot, but I have trouble believing such stresses wouldn't damage the airframe, and immediately so.
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Wingnutt,
I don't think the rate of change would have much effect. Of course R/L someone pumping the stick back and forth as seen online would quite likely exceed limit load factors. The number of cycles and ultimate load certainly would fatigue the airframe.
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Wingnutt,
I don't think the rate of change would have much effect. Of course R/L someone pumping the stick back and forth as seen online would quite likely exceed limit load factors. The number of cycles and ultimate load certainly would fatigue the airframe.
:huh
so it wouldn't have much effect? but it would likely exceed the load limits?
you are has confuse me.
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Wingnutt,
I don't think the rate of change would have much effect. Of course R/L someone pumping the stick back and forth as seen online would quite likely exceed limit load factors. The number of cycles and ultimate load certainly would fatigue the airframe.
I agree. Loading rate can have an effect on ultimate strength for certain materials, but I don't think that the aerodynamic loads on a WWII aircraft could ramp-up quickly enough for this to be an issue. I agree that there would be fatigue due to stick stirring, but as I said earlier, even at elevated loads, low-cycle fatigue can require thousands or tens of thousands of cycles before you reach critical crack size, and you get a "new plane" everytime you land, so no biggie. :)
And just to clarify, ultimate load won't fatigue the airframe, it will destroy it. One cycle, Guaranteed. :D
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Sorry guys, I should have put this in my previous post, but I think some more clarification is needed. So here it is.
Fatigue:
Many cycles of loads < Limit Load = wear out airframe over time (small undetectable cracks get bigger over time until something breaks; usually takes years)
Limit Load:
Limit Load = load at which airframe is permanently deformed (bad). Picture jugs and pony's coming back with wings permanently bent. Airplane is ruined but you survive (usually). :uhoh
Ultimate Load:
Ultimate load = load at which airframe breaks ( worse ). Significantly higher than Limit Load for aluminum and steel. Airplane falls apart and you probably don't make it.:pray
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Just say'n but I think the "plane" can take it. If the pilot don't die in the seat.
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:huh
so it wouldn't have much effect? but it would likely exceed the load limits?
you are has confuse me.
I didn't word that very well I guess. <G>
I don't think the rate that the load is applied would have a great effect on the aircraft structure.
I do think that were a pilot to pump the stick as we see online he would likely exceed the limit load factors.
So, IF a pilot could stick stir without exceeding the limit load factors I don't think it would hurt the airplane. However I do think it is highly likely the pilot would overshoot limit load factors.
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Im talking about a clean aircraft, and the transition from high positive to high negative Gs at a rapid rate.. I.E slamming the aircraft from +6g immediately into perhaps -4G in less than 1 second, and the effects of doing such an extreme maneuver rapidly over and over would realistically have on a real WW2 aircraft.
Wingnutt, I don't think we ever inflict that kind of punishment on a plane. I'm not an engineer or a RL pilot and, despite some notions acquired reading books, I'm not claiming I'm an expert: but I think the point is not on airplane limits, it's another one.
Think about it: how many times you keep pulling when you blacked- or redded(?)- out? In 99% of the instances, you'll release the pressure on the stick before the screen goes totally black or red. Well, black screen happens when you're pulling 6 maybe 6.5 Gs (-2/2.5 for negative), so, while in combat, you almost never reach those values. And they are well within the safe operational limits of our fighters, I presume. I think we normally pull no more than 5/5.5 Gs and -2 G. Add to that that you get a new plane every time you land, and you can see that a structural failure is really unlikely in AH. If you have a .ahf of a very heated fight of yours, run it and check the G-meter: I think you'll find out that my above speculation are reasonable and maybe true. :)
Mind that you can pull more than 6 G or -2 G in the game, when the screen goes black or red. You just don't do it, because it would be of no help, if not for a brief pull (G-loc is quick to come!)
So I think RL planes would take it, just because it's not so much as it seems. A total different question is if the pilots, at time, could take it: I guess we'll be able to speculate about it (and have flame wars on the boards :D) about it when CT comes out and the pilot will be simulated as a "real" man and not only a part of the damage list.
Btw, nice stick stirring on the Yak! :)
EDITed to better clarify what I was trying to say.