Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Stoney on April 09, 2008, 07:21:21 PM
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Karnak brought this up in another thread, and its something I've been wondering about for a while--thought I'd go ahead and start a new thread.
The issue started with the idea of everyone in the MA bomb-trucking the U.S. rides with maximum ordnance, i.e. P-47 carrying 2500 lbs of bombs and 10X5" HVAR. I know most tactical aircraft have restrictions based on loading or speeds with respect to the design limits of ordnance attach points. The idea is that you shouldn't be able to load up, and make 2-3 dive bomb runs carrying all that ordnance, while indicating 400+ mph and 4-5 G's on pullout, with remaining ordnance on the rails. In my experience in game, the A20 is about the only aircraft I fly that I have to pay attention to my speeds/loading during attack runs.
So, does anyone know of a resource for loading or speed restrictions for the P-51, P-47, F4U, F6F, etc.
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I don't have it in front of me and as I just moved it may take some time to find it, but the Mosquito's pilot manual lists pretty strict speed and dive angle limits for firing the rockets. The speed limit was less than 300mph.
The impression I got from the manual was that it was for aiming purposes, not structural limits though.
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About a month ago, I talked to an attack pilot who flew Corsairs in WWII and Korea. He said that their preferred method of divebombing was to drop gear, dive vertically (even up to terminal velocity in that configuration), drop bombs or sometimes one bomb from among many if they were going after multiple targets, then pull up hard. It didn't sound like he was concerned about any g limits on pullout, even in the case of Korea where the Corsair was loaded up sometimes with 4000 lbs of bombs and pulling out of the divebombing attack with many bombs still undropped.
This is anecdotal, in that I don't know how many g's he was pulling on pullout, how many bombs he'd have on pullout, etc.
Some planes did have g limits when loaded, where if you pulled too many g's with too much load, the wings would fail. The P-51's wings might not be sturdy enough for large g's with load. It's possible some had attach points that would fail. But then there are others (like the Hellcat) that routinely got into dogfights with fuel tanks attached, P-38's that (inintentionally or because they were hung) got into dogfights with 500 lb bombs attached, and the above story about Corsairs.
Given that, lacking any hard evidence to the contrary, I'd go with most fighters being able to AH's blackout g's with bombs attached.
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Brooke, keep in mind the Corsair carried the bombs in under-fuselage racks, so when pulling G-s most of the stress would go to the fuselage itself (which usually is strong enough to handle the load)
The problem-as I perceive it- resides in those planes with bombs on the wing. When pulling Gs, those bombs stressed the wings, and those could not stand as much as the fuselage.
Said that, I have no idea about real numbers or real life data about speed/Gload limits on loaded planes...so what do I know :)
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Ironically, a several-thousand-dollar college scholarship just came out to be awarded to someone who writes an essay on this very topic...
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About a month ago, I talked to an attack pilot who flew Corsairs in WWII and Korea. He said that their preferred method of divebombing was to drop gear, dive vertically (even up to terminal velocity in that configuration), drop bombs or sometimes one bomb from among many if they were going after multiple targets, then pull up hard. It didn't sound like he was concerned about any g limits on pullout, even in the case of Korea where the Corsair was loaded up sometimes with 4000 lbs of bombs and pulling out of the divebombing attack with many bombs still undropped.
This is anecdotal, in that I don't know how many g's he was pulling on pullout, how many bombs he'd have on pullout, etc.
Some planes did have g limits when loaded, where if you pulled too many g's with too much load, the wings would fail. The P-51's wings might not be sturdy enough for large g's with load. It's possible some had attach points that would fail. But then there are others (like the Hellcat) that routinely got into dogfights with fuel tanks attached, P-38's that (inintentionally or because they were hung) got into dogfights with 500 lb bombs attached, and the above story about Corsairs.
Given that, lacking any hard evidence to the contrary, I'd go with most fighters being able to AH's blackout g's with bombs attached.
Well, that's good anecdotal information--certainly a starting point. I'm not worried so much about the wing structure as a failure area. I'm simply talking about the attach points for the bombs and rockets. You hang a 1,000 lb bomb on an attach point and pull 6 G's (blackout), that bomb weighs 6,000 lbs. That's some serious weight on the attach points. Even a HVAR that weighs 150lbs or so becomes a 900 lb load. Perhaps 6 G's are an extreme example. I'll play around offline and see what I can come up with.
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Well, that's good anecdotal information--certainly a starting point. I'm not worried so much about the wing structure as a failure area. I'm simply talking about the attach points for the bombs and rockets. You hang a 1,000 lb bomb on an attach point and pull 6 G's (blackout), that bomb weighs 6,000 lbs. That's some serious weight on the attach points. Even a HVAR that weighs 150lbs or so becomes a 900 lb load. Perhaps 6 G's are an extreme example. I'll play around offline and see what I can come up with.
Indeed, but they guy I talked to gave no indication that it was of any concern whatsoever.
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Brooke, keep in mind the Corsair carried the bombs in under-fuselage racks, so when pulling G-s most of the stress would go to the fuselage itself (which usually is strong enough to handle the load)
The problem-as I perceive it- resides in those planes with bombs on the wing. When pulling Gs, those bombs stressed the wings, and those could not stand as much as the fuselage.
Said that, I have no idea about real numbers or real life data about speed/Gload limits on loaded planes...so what do I know :)
Bombs slung under the fuselage would put a higher stress on the wing than if the bombs were under the wings. With the weight concentrated at the fuselage all the stress is placed at the wing fuselage joint. If the bomb is slung under the wing that stress is spread over the entire wing. This is why many large aircraft have what is known as a "zero fuel weight". You can load the airplane up to the zero fuel weight, any additional load must be fuel (because its located in tanks in the wing). As I recall the C130 Fire fighting aircraft that had the wing failure a couple of years ago was attributed to this problem.
Quite often the Load Limit associated with bombs on the airplane is a limit on the attach points and associated structure.
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Brooke, keep in mind the Corsair carried the bombs in under-fuselage racks, so when pulling G-s most of the stress would go to the fuselage itself (which usually is strong enough to handle the load)
The problem-as I perceive it- resides in those planes with bombs on the wing. When pulling Gs, those bombs stressed the wings, and those could not stand as much as the fuselage.
Said that, I have no idea about real numbers or real life data about speed/Gload limits on loaded planes...so what do I know :)
I think that carrying bombs on fuselage would, under g's, provide more stress on wings than carrying them under the wing. The wings are what is providing the lift, not the fuselage. Loading the fuselage seems like it would put a larger bending moment on the wings than distributing the load along the underside of the wing (like wing attach points). For example, consider a board supported on each end. Take just enough weight to break the board if you suspend the weight at the middle of the span. Then divide the weight into two halves and put one at the 1/3 point and one at the 2/3 point of an identical board. The board will now be able to support that weight.
[edit: Ah, two posts on the same topic at the same time. :) ]
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See?. I was talking just out of what I 'thought' I knew and it turns out I knew nothing at all! :D
Thank you both colmbo and Brooke for correcting me :)
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I have read of a Spitfire Mk IX's 500lb bomb failing to detach and the Spitfire's wings failing on the high G pull out. The shackle didn't fail, the wing spar failed.
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I can tell you this. I use the F6F as my primary attack platform and if I pull out to hard at the bottom with ord attached I can easily snap one or both wings. The less ord, the less likely this becomes until, with no ord there is almost no chance of a wing failure.
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Brooke, keep in mind the Corsair carried the bombs in under-fuselage racks, so when pulling G-s most of the stress would go to the fuselage itself (which usually is strong enough to handle the load)
The problem-as I perceive it- resides in those planes with bombs on the wing. When pulling Gs, those bombs stressed the wings, and those could not stand as much as the fuselage.
Said that, I have no idea about real numbers or real life data about speed/Gload limits on loaded planes...so what do I know :)
FYI,
The attach points on the -4 are directly attached to the main spar (which makes the Hellcat's spar look weak) and to castings that extend back from the main spar all enclosed by major stress panels.
The fuselage attach points are not really fuselage when you consider they attach at the front to the main spar through the "fuselage".
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FYI,
The attach points on the -4 are directly attached to the main spar (which makes the Hellcat's spar look weak) and to castings that extend back from the main spar all enclosed by major stress panels.
The fuselage attach points are not really fuselage when you consider they attach at the front to the main spar through the "fuselage".
My assumption as always been that ordnance hardpoints are always attached to the aircraft's spar, other than bomb bays on bombers. Anything else seemed untenable.
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I'm not at all sure about the following, but it seems to make sense:
Could you mathematically work out the inertia of the extra bombs/rockets, and then calculate how much this adds to the wing loading during a high-G manoeuvre? If you knew the maximum tolerance of the wing, surely you could then determine whether your pull-out would cause the wings to fail?
I don't know how much (if any) of the above can be done, but it might answer your original question.
<S>
Yossarian
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I have read of a Spitfire Mk IX's 500lb bomb failing to detach and the Spitfire's wings failing on the high G pull out. The shackle didn't fail, the wing spar failed.
And boom, we got the E wing with two hard points and strengthened.
The key though was it failed because of the stress on the wing because the bomb didn't come off and the pilot was pulling out. Can't imagine HTC is going to take the time to model in random bomb hang ups.
I suppose I could post the story of the 370th FG P38J pilot who got into the turn fight with the 109 on the deck and out turned him. He RTB'd to find that his 500 pounders hadn't come off when he tried to jettison them and had fought the 109 and won despite that extra weight and stress on the wings :)
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Wasn't quite my point, Dan. ;)
I was mainly pointing out that the shackles were designed to very high tolerances.
I actually think Spit wings come off too easily in AH as I have never heard of a Spit shedding its wings except a) before the elevators had been given extra resistance to prevent massive G spikes, b) A 500lb bomb got hungup and stayed on for a high G pullout, and c) Spitfire Mk XIVs that were incorrectly reassembled in India.
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In RL, a P-47 on a divebombing sortie had a 500lb bomb hang up on the wing during its attack dive. The pilot pulled out, but it bent the wing and he had to RTB.
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What angle of dive was used? For example the Spit could be dived up to a 60* angle.
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I couldn't remember where I saw this before, but I went back and re-read the P-47N POH. This is what I'm talking about:
(http://i125.photobucket.com/albums/p61/stonewall74/P-47NSpeedLimitations.jpg)
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all good and well guys but when the simulation interferes with the game you are going to find much resistence from HTC. They are most interested in the middle ground. Realistic stress physics under maximum loading are performance characteristics outside the scope of good gameplay. Imagine all the wings popping off of dive bombing lancasters and you will get my drift :aok
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My assumption as always been that ordnance hardpoints are always attached to the aircraft's spar, other than bomb bays on bombers. Anything else seemed untenable.
You're partially correct Karnak. It's really more critical that the ordinance rack attach to a rib (if wing-mounted) or to a longeron (if fuselage-mounted). This will allow you to shear the fore & aft loads into the skins. Typically the rack will also span between front and rear spars in order to "beam" the vertical loads and ordinance pitching moments to the main spars.
A rolling-pullout is typically the critical load case for wing-mounted stores. The combination of vertical forces, pitching moment, and side-loads on the store can produce some viscious loads on the attachment lugs and rack structure. Flight restrictions (limit g's) will be dictated by whatever part has the lowest margin of safety.
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all good and well guys but when the simulation interferes with the game you are going to find much resistence from HTC. They are most interested in the middle ground. Realistic stress physics under maximum loading are performance characteristics outside the scope of good gameplay. Imagine all the wings popping off of dive bombing lancasters and you will get my drift :aok
First I want to find out about accuracy, then we'll deal with gameplay issues.