Aces High Bulletin Board
General Forums => Wishlist => Topic started by: Simaril on November 20, 2005, 08:05:52 AM
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Level bombers didnt dive bomb for a simple reason: they couldnt.
Not just because the pilots wanted to get home, but because the planes couldnt stand the forces inherent in the bomb run. I dont have access to pilot manuals, design data, and engineering tests for the buffs (I'm not even an engineer), but I understand at least one thing clearly about aircraft design: every decision is a trade off.
If you clip the wings to help roll rate, you cut into sustained turn. If you decrease wing loading to help turning, you cut into max speed. If you add fuel capacity to help range, you reduce maneuverability and climb. If you try to add every feature and capacity, you end up with a plane that does nothing well. So when you design an aircraft, you design it FOR A SPECIFIC PURPOSE.
Level bombers were designed for long range bombing from altitude . (Yes, I know they were used at low alt, but that wasnt the design specification.) Because of the goal, decisions made pointed to maximizing the features that helped the aircraft succeed at the task. And, for the purposes of this discussion, consider just the effect of increasing wing G-tolerance on the mission.
Wings on heavy bombers needed to be strong enough to carry the load of the aircraft, its fuel, and its ORDNANCE (thanks, Leviathan). They had to be designed with a safety margin that allowed for stresses expected in performing the design mission, which would include altitude changes and banking (60 degree bank doubles the force on wing spars, even without applying G). Diving stresses those structures even more. With increased air speed the airframe gets increased friction forces, vibration (and the risk of resonance induced force multiplication) --- and INERTIA.
Any effort to change direction while at speeds above design parameters requires applying further stress to the airframe and control surfaces, almost certainly causing structural failure. While extra margin was built in, it wasnt allowed to unnecessaily compromise the primary mission. Building spars strong enough to dive costs WEIGHT. Allowing a B-24 enough strength to withstand, much less pull out of, a 310mph dive would have REQUIRED a reduction in bombload or range. Any designer who seriously wanted to make that compromise wouldnt be smart enough to hold a job.
I have tried to research for design documents on the net, and have come up short of the definitive data I want. I have found original pilot documentation that, for example, instructed them to keep airspeed below 275mph when descending. I've also dicumented that speeds above 305 would set up catastrophic vibrations in the de-icer boots along the leading edge, causing structual wing failure. Application of control forces can also cause catastrophic failure:
In the higher speed range, the elevators become "heavy". This is desirable inasmuch as it helps to prevent sudden extreme application of the elevators, which might prove damaging to the structure. When maneuvering the airplane, as in a dive, always keep the airplane trimmed by use of the trim tabs. If the pilot attempts to hold the full stick load, his sudden relaxing can apply a destructive force to the airplane
b-24 pilots notes, 1942 http://www.gaspartorriero.it/HTML/B24%20Pilot%20Notes.htm. All emphasis mine.
Note that even RELAXING controls at speed, much less yanking on them, could cause structural failure.
From the same site, speed limits are clearly outlined for various loads:
DIVE - The limiting diving speeds for various gross weights are:
_____________________MPH KmPH Knots
41,000 lbs (18,144 Kg) 355 570 300
47,174 lbs (21,398 Kg) 325 520 280
56,000 lbs (25,401 Kg) 275 440 240
Air loads build up rapidly on any large airplane in a dive, therefore, avoid abrupt movements of the controls.
Control trim should be maintained with the idea of keeping tail surface forces to a minimum. It is better to trim the airplane to slightly nose heavy rather than tail heavy. If it were trimmed tail heavy, in a dive the inherent tendency to pull up would make the application of up-elevator easier and more abrupt, creating higher load factors of "g's".
It is my impression (and PLEASE correct me if I'm wrong, HT) that these structural limits are not well modelled in AH2. I'm fairly sure I've taken full ordnance loads faster than that, though full fuel loads arent needed in the game.
I'm also suspicious that the very "heavy" controls described at speed arent well modelled. The manual notes that EVEN AT LANDING SPEED OF ABOUT 100mph
When flying a heavy airplane remember that a heavy body in motion resists effort to change the motion. Therefore, if a steep glide is being made with accompanying high rate of descent, it takes some time and a considerable force to flare out this rate of descent and change the direction to one parallel to the ground. It cannot reasonably be expected with a rate of descent of over 500 ft./min. (152 meters/min.) to start to level off 5 to 10 feet (1.5 to 3 meters) above the ground and succeed in doing anything but "flying in".
_____________________________ ___
The current use of heavy bombers in the MA has significant game impact. Discussion of "whats good for the game" has been inconclusive; however, correct flight models are a priority at HTC. I beleive that the above information would both result in more accurate modelling and improved game play.
For those with better research skills (or access) than mine, there are several avenues that may produce even more useful results.
1. Bomb dropping restrictions. There is a tantalizing comment in the pilots notes: Bomb Clearance Instructions
When releasing bombs in a glide or climb, observe the restrictions shown in "Armament Manual".
If anybody can track down a copy of this document, it would likely describe the design limitations for non- horizontal bombing -- and thus resolve another discussion with fact rather than opinion.
2. During engineering tests, it was contemporary practice to test the functional (as opposed to design) strength of aircraft by simply loading weights on the wing until the thing failed. Delving into archival records of Consolidated or Boeing through successor corporations or historical archives might yeild us hard numbers that would tell how much "cushion" was included in the above speed and load restrictions.
With Regards,
Simaril
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Just restrict them to dropping bombs from the F6 view and everything is solved.
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Not really, grits. As others have said, all a lancstuka would need to do is to nose down, establish dive, hit F6, drop ord, back to 1 position.
The F6 rule isnt optimal for two reasons: it wouldnt work to change dive bombing; and it is a "game" solution to what is essentially a simulation modelling problem.
EDIT: Also, realize that in essence HTC has spoken on the F6 issue. The idea has been around the block more than once, and HTC has neither commented nor shown any sign of adopting it. By inference, the F6 solution isnt popular in the corporate office....so dont hold your breath. I suspect that if this issue is addressed, it will be addressed for different reasons and in different ways.
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When you switch to F6 view autotrim on level turn on automatically. But i agree "F6 restrict" will not completely solve problem. As well as "G-load limits".
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I think banking 60 degrees would increase the load factor, the amount of lift the wings have to produce to prevent stalling, not the Gs on the wing (unless it starts trying a coordinated turn at that bank). If high angles of bank created Gs, woluldn't all planes have their wings come off at the 90 degree point?
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Not all bombers are B24. Ju-88 could do 800 km/h in dive and was used in dive bombing missions. It even had dive brake and automatic dive recovery.
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Read simarils 1st sentence in his 1st post JAWS. Ju88's are fine and can dive bomb, no ones debating that.
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"41,000 lbs (18,144 Kg) 355 570 300
47,174 lbs (21,398 Kg) 325 520 280
56,000 lbs (25,401 Kg) 275 440 240"
Imagine the weight the wings have to endure in a 2G pull-out...
The problem is not the forward speed as the wing is very large in that plane but very thin in that other plane and G's do build up rapidly in a pull-out...
-C+
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Originally posted by Debonair
I think banking 60 degrees would increase the load factor, the amount of lift the wings have to produce to prevent stalling, not the Gs on the wing (unless it starts trying a coordinated turn at that bank). If high angles of bank created Gs, woluldn't all planes have their wings come off at the 90 degree point?
Thanks for the clarification. Like I said, I'm not an aeronautical engineer by any stretch. I found a document showing "load factors" at various degrees of bank, and made a mistaken assumption about the definition.
Oleg,
While autotrim does turn on in the f6 view, I doubt it would have any effect on the targeting ability of dive bombing B24s in the game. Set salvo to 12, and I bet you could hit the 2 necessary keys in under a half second (F6, fire) with minimal flight path disruption.
And to all,
The bomber stress tolerance modelling issue has been in the back of my mind for a long while. I'd hoped that someone in the community had access to documents that would be definitive, but no ones stepped forward with them so far.
So, even though I'm a novice at this stuff, I'm starting down the archival research path through the National Archives, NASM, and Library of Congress. Wish me luck, adn I'll keep you posted.
Regards,
Simaril
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I dont dive bomb but I have done an immelman in an empty B17 and thought that it was a bit much to have been able to pull it off
Why did I pull an immelman in a b17, I was trying to escape a fighter, yep I know it was impossable but... GO DOWN FIGHTING I SAY
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In real life, a bomber pilot would not risk their life or the crews life by diving on a target. However the pilot could dive on a target and tell the bombardier when to release if this was a last act of defiance, if ya gonna die go out in a blaze of glory!
The real glitch here is even if you can't pull out of the dive or your plane's wings get torn off and you get killed your back in the air in less than a minute. In real life your really dead!
So I guess this is the part where we say "Don't try this at home in a real bomber even if you have adult supervision."
Thanks for the tip, maybe I'll try dive bombing next time I'm flying the friendly skies in my Boeing
DWaves
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Originally posted by Simaril
Also, realize that in essence HTC has spoken on the F6 issue. The idea has been around the block more than once, and HTC has neither commented nor shown any sign of adopting it. By inference, the F6 solution isnt popular in the corporate office....so dont hold your breath. I suspect that if this issue is addressed, it will be addressed for different reasons and in different ways.
I agree with you completely on this whole thing, don't get me wrong, but you just mooted yourself; have you ever seen them reply to this topic, much less any OTHER change to an existing model (other than a graphical error or engine setting type of thing) or any real change in the first place?
HTC doesn't reply(unless you're completely wrong and HT needs his monthly pwn :D), but they do read. Seen a couple posts that were new problems or ideas that weren't that big with no replies at all and in the next update list, there it was.
Yeah, that second "paragraph" got choppy. I'm going to bed now, seeing as it's three-freakin-thirty. *thump*
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In "Wings of Morning" the auther spends a fair amount of time covering the training of the Black Cat"'s crew. From what I read there the B24 was very very rugged overall but the design of the wing made it very suscepible to any type of torque or excessive G's. It was actually a difficult plane just to fly when "heavy" and alot of them were lost in training missions simply because pilots let the bird get away from them (often alone and in daylight)...
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If you can find some detail data on max forces on any buffs we would be glad to take a look at them. But you might be suprised how low the g limits already are.
HiTech
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Pff, just moot me too HT. :D
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Clearly bombers are gamed in a way very inconsistent to real usage. How about using f6 for bomb release only as asked HT? Is there any intent to deal with this issue or is it a non issue to HTC? It would be nice to have a thread deal with this issue in a fair and appropiate manner. I think it falls under "I like realism as long as it enhances gameply" dictum.
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simarli U R WRONG SIR WRONG WRONG WRONG. B17s could stand a dive. how in the world do u think they put out engine fires??? they dove to the maximum speed that the plane would alow to put out fires that the extinquisher couldnt put out. Plus there isnt really any desing flaws to tell you that it cannot dive with bombs. EVERY PLANE CAN DIVE BOMB TO A CERTAINT EXTENT!!!! The B17 can dive for 5000 feet before the pilot has trouble keeping the nose down. If you think about it the plane can dive with bombs its just the pull up after that you get ur tips broken off. I have read in some articles off the internet that some 17s did dive (although not very steep or steep) on there targets when they were low alt. And this goes for all bombers!!!! So in a short summary These planes can handle dives and ur just going to have to live with it.
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Of course they can dive. But how much, How Fast and How hard can they pull out.....
Oh and I am a toolsheading Furballer so dont think I am anti tool shedder.
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rabbidrabbit: Every plane or vehicle is, So going to be realy difficult to use that as an argument for changing that piece of the bomber .
HiTech
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Originally posted by Lan784
simarli U R WRONG SIR WRONG WRONG WRONG. B17s could stand a dive. how in the world do u think they put out engine fires??? they dove to the maximum speed that the plane would alow to put out fires that the extinquisher couldnt put out. Plus there isnt really any desing flaws to tell you that it cannot dive with bombs. EVERY PLANE CAN DIVE BOMB TO A CERTAINT EXTENT!!!! The B17 can dive for 5000 feet before the pilot has trouble keeping the nose down. If you think about it the plane can dive with bombs its just the pull up after that you get ur tips broken off. I have read in some articles off the internet that some 17s did dive (although not very steep or steep) on there targets when they were low alt. And this goes for all bombers!!!! So in a short summary These planes can handle dives and ur just going to have to live with it.
Lan you may have read all sorts of interesting things, but your manner displays more ignorance than wisdom. Allow me to quote from the B-17 technical orders:
The structural factors limiting the dive speed to 305 mph are the engine ring cowl strength, the wing leading edge de-icer boot strength, the pilot compartment winshield and enclosure strength, and the critical flutter speed. The engine ring cowl has been designed to wthstand 420 mph. Windshield and pilot compartment have ample margin at 305 mph. The wing leading edge de-icer boots begin to rise slightly form the wing at 305 mph, and any excessive additional speed would probably lift the upper portion of the boot well above the wing surface and allow it to flap severely against the leading edge, thus causing a structural failure.
This is just one area of inquiry that cahllenges current MA usage of the buffs, Lan. YOU need to realize that when the war stories talk about "diving to put out fires" they're not talking about diving the way you mean it. The cruise speeds of B17s, at which the fires started, are much lower than the firewalled speeds most use here. Diving meant dropping altitude to pick up speed, not nosing down to dive bomb. If you start at full power and dive for 5000 feet in a b17, the wings would rip off long before you dropped ord.
And, to quote you, you're just going to have to live with it.
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Originally posted by hitech
If you can find some detail data on max forces on any buffs we would be glad to take a look at them. But you might be suprised how low the g limits already are.
HiTech
Thanks for the consideration, HT.
My intention is purely to gather data, not to start a whine fest. I know you guys take your modelling very seriously, and I know my ideas are now conceptual rather than documented. I'm chasing down some leads, but I realize that archival digging is slow and painstaking -- so I dont expect to be coming back to the board with evidence for a while.
Simaril