Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Stoney on October 28, 2009, 05:03:43 PM
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Why is it everyone thinks Fowler flaps, as a flap design type, are more efficient than all other flaps? For what its worth, you could design a Fowler Flap that was less efficient than a Split Flap, depending on how its designed. The type of flap, taken by itself, has no bearing on how efficient a flap system is on a particular airplane.
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Probably because in this game they're modeled as anti-gravity repulsor lifts.
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I can't speak for everyone but I believe it's because they increase the wing area and lower the wing loading.
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Probably because in this game they're modeled as anti-gravity repulsor lifts.
Evidence?
Thought so.
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Why is it everyone thinks Fowler flaps, as a flap design type, are more efficient than all other flaps? For what its worth, you could design a Fowler Flap that was less efficient than a Split Flap, depending on how its designed. The type of flap, taken by itself, has no bearing on how efficient a flap system is on a particular airplane.
Because the Book of Kelly Johnson tell us so? :D
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Probably because in this game they're modeled as anti-gravity repulsor lifts.
If Krusty says so, it has to be true.
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Why is it everyone thinks Fowler flaps, as a flap design type, are more efficient than all other flaps? For what its worth, you could design a Fowler Flap that was less efficient than a Split Flap, depending on how its designed. The type of flap, taken by itself, has no bearing on how efficient a flap system is on a particular airplane.
I'm sure you could design a screwed up Fowler flap that wasn't efficient. If you tried. If you had the desire. Although I don't know why anyone would want to.
And what I've read over the years does not agree with the text in bold above.
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Your starting to baffle me Stoney because you usually think things through better than you are today. :headscratch:
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The reason folks say "Oh, Fowler flaps? They're super!" is because of their experience with this game.
Regardless of how correct this game is (that's another issue), it models them so lovingly and so beneficial to use that folks just chime in "Oh they're efficient!" -- meaning they base their opinions off the game.
That's what my post meant. Sorry that 2 of you can't get my point.
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This image is coming in very handy lately...
(http://www.cheffers.co.uk/flaps1.GIF)
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This image is coming in very handy lately...
(http://www.cheffers.co.uk/flaps1.GIF)
I'm familiar with this. All things being equal the same flapped area, using a Fowler design can be more efficient. But, there are considerations beyond simply the aerodynamic function of the things. The mechanism is a lot more complicated and usually, much heavier. It is conceivable that there could be Fowler designs that, while aerodynamic marvels, create such a weight penalty that they lose their efficiency to simpler designs. There are other situations where the designer has a limited flapped area to use for the system, and chooses a fowler design to maximize the limited space. The disclaimer at the bottom of that chart states as much.
My point in beginning this thread was to express my dismay when I hear people say "its flaps are more efficient because they're fowlers". For the P-38, the most oft used example, the flaps may be more efficient, but its because its a more efficient design overall, not merely because its a fowler design.
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Flaps usage in AH seem to be calculated from theoretical formulas but... all I have is anecdotal evidence and evidence from Warren Philips that indicates about a 20% error in effectiveness... but I want the evidence to be there so maybe Im just not doing it right. Im still trying to work this stuff out in between other projects.
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i've seen a diagram posted that the poster claims shows different conclusions from that chart on another board,
unfortunately the discussion is old and the original has been removed, the remaining thumbnail is too small to make out.
the data sheet chase can be very disappointing ...
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t
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Even if my work varifies my suspicions it will not in any way support your assertions.
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I'm familiar with this. All things being equal the same flapped area, using a Fowler design can be more efficient. But, there are considerations beyond simply the aerodynamic function of the things. The mechanism is a lot more complicated and usually, much heavier. It is conceivable that there could be Fowler designs that, while aerodynamic marvels, create such a weight penalty that they lose their efficiency to simpler designs. There are other situations where the designer has a limited flapped area to use for the system, and chooses a fowler design to maximize the limited space. The disclaimer at the bottom of that chart states as much.
My point in beginning this thread was to express my dismay when I hear people say "its flaps are more efficient because they're fowlers". For the P-38, the most oft used example, the flaps may be more efficient, but its because its a more efficient design overall, not merely because its a fowler design.
Ok I have a better comprehension of what you are getting at now. It would be interesting to see what a fowler design would have on say a spitfire. I still feel as if it would be an enhancement over a split design or a plain flap.. Take the ki-84 for example, it has a very similar flap design on a very different wing, yet it has a much increased turn performance with the use of flaps.
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"It would be interesting to see what a fowler design would have on say a spitfire. I still feel as if it would be an enhancement over a split design or a plain flap.."
While I do not agree fully with Stoney this quote seems to verify his assumption.
having a Fowler flap in a Spit could be problematic since if you consider the drag that big wing causes, say, at 13 deg AoA if you add the drag effect of Fowler to that the plane could run out of engine power to benefit from increased wing area in anything but landing situation. And even without Fowler the Spit has a tendency the flare quite long so a Fowler would probably not add anything but weight to the design.
Why it works in Ki84 then? Smaller wing area and less weight from wing structure and less drag with AoA so that with Fowler depolyed the drag does not become overwhelming while the lift is increased.
Maybe it would be more interesting what a Fowler flap design could give to a high wing loaded designs, e.g. to FW190s.
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Might be moot, but here's some food for discussion on fowler flaps....from the summary:
"Of the three flaps tested, the Fowler flap had the lowest drag coefficient at high lift coefficients."
I'm not aeronautics geek, but low drag with high lift sounds good to me. :)
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930085051_1993085051.pdf
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See Rule #4
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i think it would depends on what you want from your flaps. the spitfire for example always was a good turning aircraft so why add the weight and the drag (assuming the wing would need to be thicker to allow for the mechanism) of adding a fowler flap system to improve the turn rate of a plane that already turned as well or better than all it's primary adversaries.
also the part of the turning process where it may have suffered vs. it's opponents was in its roll rate which is why the wings were clipped in some models.
in the case of the bigger or higher wing loaded planes, i suspect the designers foresaw the need to possibly close up a turn a bit vs. a projected opponent and since the weight battle was already lost they may have figured the cost/benefit was in favor of having a device to improve the turn.
i.e. sitting over the design table looking at the spit you would be thinking "iffin it ain't broke ... don't break it"
sitting over the design table looking at the 38 you might be thinking "wow this thing is gonna need a little turn assistance" because you had a good idea it's adversaries would be able to turn better.
i know that is all projection but it's fun to think about.
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t
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Might be moot, but here's some food for discussion on fowler flaps....from the summary:
"Of the three flaps tested, the Fowler flap had the lowest drag coefficient at high lift coefficients."
I'm not aeronautics geek, but low drag with high lift sounds good to me. :)
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930085051_1993085051.pdf
There is no doubt in my mind that a Fowler system is the most beneficial design of the different flap families, taken by itself. However, it is not helpful for anything aerodynamic to be considered a panacea. Saying that the flaps on an aircraft are "the most efficient" is like saying that elliptical wings are the most efficient, or that laminar flow airfoils are the most efficient, or that water cooled engines are the most efficient, or that high aspect ratio wings are most efficient. When you isolate any one component of the aircraft, and compare it out of context to another component on another aircraft, you run the risk of making some false comparisons. For aircraft, the flap system is a means to reduce landing speed--one of the reasons the Corsair has such a monstrously efficient flap system--big heavy plane that needs to fly extremely slow to land on a carrier. Why didn't it use Fowler flaps? Surely it had more need than a USAAF P-38? Perhaps the designer decided the tradeoff wasn't worth it, or that he had enough flapped area that a slotted flap was going to be sufficient for him to hit his design criteria. Perhaps the P-38 has the most efficient flaps in the game, but its because the flap system is most efficient, and not simply because the flap design uses a Fowler system.
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There is no doubt in my mind that a Fowler system is the most beneficial design of the different flap families, taken by itself. However, it is not helpful for anything aerodynamic to be considered a panacea. Saying that the flaps on an aircraft are "the most efficient" is like saying that elliptical wings are the most efficient, or that laminar flow airfoils are the most efficient, or that water cooled engines are the most efficient, or that high aspect ratio wings are most efficient. When you isolate any one component of the aircraft, and compare it out of context to another component on another aircraft, you run the risk of making some false comparisons. For aircraft, the flap system is a means to reduce landing speed--one of the reasons the Corsair has such a monstrously efficient flap system--big heavy plane that needs to fly extremely slow to land on a carrier. Why didn't it use Fowler flaps? Surely it had more need than a USAAF P-38? Perhaps the designer decided the tradeoff wasn't worth it, or that he had enough flapped area that a slotted flap was going to be sufficient for him to hit his design criteria. Perhaps the P-38 has the most efficient flaps in the game, but its because the flap system is most efficient, and not simply because the flap design uses a Fowler system.
i think you touched on it in the purposes stoney, as you pointed out the hog being an aircraft carrier intended plane a lot of drag in the flap system was i am pretty sure seen as a desired effect.
the 38s needs were different obviously, so increasing lift without reducing speed was the priority.
i wonder if in a lot of the planes the flaps were explored for turn improvement as sort of a "byproduct" of the ability to adjust the wing for better landing speeds.
as in that report i posted it sort of seemed like they were really looking for the reasoning for dropping flaps to improve turn performance, almost like that was not the design intent of the flaps at all.
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i think you touched on it in the purposes stoney, as you pointed out the hog being an aircraft carrier intended plane a lot of drag in the flap system was i am pretty sure seen as a desired effect.
the 38s needs were different obviously, so increasing lift without reducing speed was the priority.
i wonder if in a lot of the planes the flaps were explored for turn improvement as sort of a "byproduct" of the ability to adjust the wing for better landing speeds.
as in that report i posted it sort of seemed like they were really looking for the reasoning for dropping flaps to improve turn performance, almost like that was not the design intent of the flaps at all.
Well, like you said in another post, the P-38 was a very heavy aircraft as well. I don't know what the design requirement for landing distance and landing speed issued by the USAAC was, but given the engine/boom positions, the amount of flapped area was going to be small, relative to the entire wingspan. Perhaps the Fowler design was chosen purely to maximize that limited area. Whereas the Corsair had the benefit of the bent wings providing more flapped area, and the ability to use more of the overall wingspan for flaps. I don't know, just spit-balling... One thing to remember though is that flaps are used to increase the camber of the wing, and therefore increase lift. A higher Cl created by the flap extension is what lowers the landing speed, not the drag. The heavier the airplane, the higher the required Cl to hit a target landing speed. Lower landing speeds mean shorter runways and less need for extremely rugged and heavier landing gear. The drag that results from flap extension is a by-product of flap use, not a primary purpose. Spoilers are used to purposefully create drag, for example.
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Nakajima seems to have chosen Fowler flaps for its fighter products so as to enable an effective combat flap. Mitsubishi did not, though its fighters were, like the F4U, the carrier based fighters, excepting the J2M series.
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It really depends on what you want to gain from the flaps and you overall plane design.
Flaps first function is landing. This has two faces: drag and lift. Drag is GOOD for landing in most planes. If you plane has low drag for its mass you need an air brake or you will run out of runway. For this purpose, there is no reason to use a complicated flap. Lift is important if your plane is very high wingloaded - it helps to reduce the stall speed, hence the landing speed. Lower landing speed need less added drag to stop you in time. P-38 which is fairly heavy and has no torque, hence can safely fly with high power near stall speed, is a prime candidate to have one.
Then there is the overall plane design. Surprisingly, planes are not built to have the "best" possible performance. There are many other considerations that have nothing to do with how the plane flies that end up having greater effect on the air-war. Making the plane cheaper, easier & quicker to manufacture, easier to maintain, more reliable and safer, can have far reaching consequences - much more than improving an insignificant corner of the flight envelope. Could the mosquito be "better" had it had more metal and less wood? Perhaps yes, but it would be much more expensive and could not be built by the piano makers when no one was buying pianos. Likely it would not have been built at all. The P-38 was a great fighter, but it was very expensive and required almost twice the maintenance that a single engine plane needed. You could use these engines to get two mustangs instead. The F4U had a more advanced design and many performance tweaks over the F6F. However, the F6F was more reliable, faster to manufacture, cheaper and safer on the flight deck. The F6F was fighting all the decisive battles when the F4U was fighting technical problems and deck qualifications.
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Nakajima seems to have chosen Fowler flaps for its fighter products so as to enable an effective combat flap. Mitsubishi did not, though its fighters were, like the F4U, the carrier based fighters, excepting the J2M series.
Zeros didn't weight 12,000 lbs when they landed either. I don't know this, merely guessing, but I'd bet that Nakajima didn't choose the Fowler design for combat--they chose it for landing, or, perhaps to acheive a certain landing speed. If you need the plane to "turn" better in combat, you'd design the wing differently in the first place. By that, I mean to say that if I'm the designer and the requirement is for the plane to have a turn radius of X, I'm not going to design the plane to give me a radius of Y and then let the flaps get me the rest of the way to X. I'm going to build the plane to hit X without flaps from the start. I don't think period aircraft had those types of design requirements--wingloading perhaps, but not radius--but hopefully you understand what I'm getting at.
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Dbl post
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Maybe, but as I understand it all the Nakajima fighters have a "combat" setting for their flaps.
Personally I think the deployment speed for the combat setting has simply been lost to time and what we have in AH are the landing speeds for the combat setting and the landing setting.
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I'm familiar with this. All things being equal the same flapped area, using a Fowler design can be more efficient. But, there are considerations beyond simply the aerodynamic function of the things. The mechanism is a lot more complicated and usually, much heavier. It is conceivable that there could be Fowler designs that, while aerodynamic marvels, create such a weight penalty that they lose their efficiency to simpler designs. There are other situations where the designer has a limited flapped area to use for the system, and chooses a fowler design to maximize the limited space. The disclaimer at the bottom of that chart states as much.
My point in beginning this thread was to express my dismay when I hear people say "its flaps are more efficient because they're fowlers". For the P-38, the most oft used example, the flaps may be more efficient, but its because its a more efficient design overall, not merely because its a fowler design.
The P-38 actually uses a hybrid flap system, Fowler Flaps and the conventional hinged flap system.
ack-ack
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The bold print above is just typical Krusty BS. Another bogus assumption with little basis in fact. Another attempt by Krusty to justify a Krusty whine.
People who have never played this game, but are well versed in aircraft design know Fowler flaps are efficient, possibly even the most efficient flap design.
Nice attempt at flamebaiting, Hilts, but you fail.
Posted on an AH forum, where a lot of folks seem to chime in with "Oh, the plane is such a great performer because of the fowler flaps!" comments, my post was a commentary on the AH populace.
It's directly applicable to the original post:
Why is it everyone thinks Fowler flaps, as a flap design type, are more efficient than all other flaps? For what its worth, you could design a Fowler Flap that was less efficient than a Split Flap, depending on how its designed. The type of flap, taken by itself, has no bearing on how efficient a flap system is on a particular airplane.
90% of the so-called elite will go on giving tips and hints on how to out-turn anything with flaps in this game, including on this sub-forum. Most of the discussions helping new pilots involve "Use this plane's flaps, they're fowlers, and will make you turn super tight!"
Quite relevant, and on-topic.
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90% of the so-called elite will go on giving tips and hints on how to out-turn anything with flaps in this game, including on this sub-forum. Most of the discussions helping new pilots involve "Use this plane's flaps, they're fowlers, and will make you turn super tight!"
Quite relevant, and on-topic.
Same thing comes up with the Corsairs. "Dump speed and get the flaps out immediately!" (personally, I think the rudder is just as if not MORE important).
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Same thing comes up with the Corsairs. "Dump speed and get the flaps out immediately!" (personally, I think the rudder is just as if not MORE important).
i feel the same way about the rons ...
but i fly the a8 so dumping speed happens when you think about turning ...
:D
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90% of the so-called elite will go on giving tips and hints on how to out-turn anything with flaps in this game, including on this sub-forum. Most of the discussions helping new pilots involve "Use this plane's flaps, they're fowlers, and will make you turn super tight!"
I am not really one of the elite, but I have never recommended a new player use flaps. I always point them towards fundamentals first. They can learn about flaps on their own, once they have some idea how to fight.
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Nice attempt at flamebaiting, Hilts, but you fail.
No attempt at flame baiting. Not at all. Merely a statement of fact well proven by your posting history.
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Well, I asked this question in some P-38 thread not long ago, but no replies. Hopefully on this more focused thread, i`ll be luckier.
Raptor's diagram attributes a distinct "nose down pitch" to pretty much all the flap types when deployed.
In AH, all flap types generate a distinct "nose up pitch" when deployed.
So, which is right?
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Well, I asked this question in some P-38 thread not long ago, but no replies. Hopefully on this more focused thread, i`ll be luckier.
Raptor's diagram attributes a distinct "nose down pitch" to pretty much all the flap types when deployed.
In AH, all flap types generate a distinct "nose up pitch" when deployed.
So, which is right?
It depends on the aircraft design. Some go up, some go down.
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Probably because in this game they're modeled as anti-gravity repulsor lifts.
Krusty, going by Dokgonzo's listed turn radii, I once got these figures:
A. Full deflection of the P-38's Fowler flaps reduces turn radius, as compared to non-flap radius, by about 26%.
B. Full deflection of the P-47D-40s's slotted flaps reduces turn radius by 25%.
C. Full deflection of the of the Fw-190s *split* flaps reduce turn radius by 24%.
D. Full deflection of the P-51D's plain maneuvering flaps reduce turn radius by 19%
E. Full deflection of the F4U-1D's flaps reduce turn radii by by 40%.
B, C, D, and E all seem a whole lot more worthy of questioning comment than A, IMO. As you can see, the the P-38s flaps cannot be superflaps, since they do not reduce the turn radius by degree remarkable in comparison to other aircraft. That the P-51D's plain flap comes out worse than the 190s split flap and that these flaps are right up there with some inherently better maneuvering flaps also seems odds.
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E. Full deflection of the F4U-1D's flaps reduce turn radii by by 40%.
That is a lot. It's no wonder good F4U pilots give me fits if I'm not in something with good powerloading.
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It depends on the aircraft design. Some go up, some go down.
In AH, all go up. Regarding the AC design, can you give a little more detail? Thanks!
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Krusty, going by Dokgonzo's listed turn radii, I once got these figures:
A. Full deflection of the P-38's Fowler flaps reduces turn radius, as compared to non-flap radius, by about 26%.
B. Full deflection of the P-47D-40s's slotted flaps reduces turn radius by 25%.
C. Full deflection of the of the Fw-190s *split* flaps reduce turn radius by 24%.
D. Full deflection of the P-51D's plain maneuvering flaps reduce turn radius by 19%
E. Full deflection of the F4U-1D's flaps reduce turn radii by by 40%.
B, C, D, and E all seem a whole lot more worthy of questioning comment than A, IMO. As you can see, the the P-38s flaps cannot be superflaps, since they do not reduce the turn radius by degree remarkable in comparison to other aircraft. That the P-51D's plain flap comes out worse than the 190s split flap and that these flaps are right up there with some inherently better maneuvering flaps also seems odds.
Keep in mind that per its own operator's manual the F4U already gets a SIGNIFICANT reduction in stall speed at power-on and full flaps as opposed to power-on clean. It's been a while since I've looked at it but it may have been as high as 40% stall speed reduction, so these flaps are generating a TON of additional lift. Which also only makes sense for a carrier aircraft that needs to make abnormally slow landing approaches. I want to think that the P-51's stall speed reduction is in line with this as well, about 19% speed reduction at full flaps power-on, so HTC may have it modeled that % turn radius reduction is roughly equivalent to the % stall speed reduction.
Now SHOULD it be like this? That I don't know enough physics to answer, but it sounds ludicrous to me that that much additional lift wouldn't have a significant effect on turn radius.
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The smallest possible radius is equivalent to turn-rate at stall speed. If you can keep the same turn-rate but fly slower, your radius will decrease. In the F4U, dropping flaps not only reduces the stall speed, but even increases the turn-rate. So, yes, the flaps are clearly increasing the lift. For the rest of our aircraft, there is usually a turn-rate penalty that comes with the smallest possible radius vs. the no flap radius.
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In AH, all go up. Regarding the AC design, can you give a little more detail? Thanks!
In general the movement of the lift and drag forces when you add flaps and any change in airflow over the tail determines the direction of the pitch moment. In a particular aircraft the amount of flaps added can change the direction also.
I don't know that the pitch moment from flaps is modeled Aces High. Adding flaps will have the effect of increasing the wing incidence so you'll have more lift for the same pitch attitude. You may just be seeing the increased lift.
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The smallest possible radius is equivalent to turn-rate at stall speed.
If stall speed is defined as the slowed speed one can fly without loosing altitude, than it is impossible to turn at that speed without loosing alt.
It is meaningless to compare "full flaps" state between planes as full means different things on different planes, even on planes that had the same type of flaps. Flaps produce both lift and drag. The drag is needed for landings but is bad for sustained turning. The so called "maneuvering" setting is supposed to strike a balance between the added lift, drag and the available power of the plane and as far as I know is never the "full" setting, intended for landing.
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Good point, "at stall speed" isn't very precise. It would be an airspeed a little bit faster than stall speed, and even that's not precise. ;)
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In the F4U, dropping flaps not only reduces the stall speed, but even increases the turn-rate.
Don't forget Hammer's graphic. The F4U only increases turn rate up to the third increment of flaps. Any more than that and turn rate decreases.
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Don't forget Hammer's graphic. The F4U only increases turn rate up to the third increment of flaps. Any more than that and turn rate decreases.
However, often there are situations where a significantly smaller turn radius in the short term, may actually provide the most important critical advantage over maintaing a better turn rate in the long run. Having a better turn rate doesn't amount up to much when the plane behind you gains a smaller turn radius just long enough to blow you out of the sky.
- just a reminder, ofcourse.
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Don't forget Hammer's graphic. The F4U only increases turn rate up to the third increment of flaps. Any more than that and turn rate decreases.
my apologies for chiming in, but could you re-post or link to Hammer's graphic? I have not seen that one yet......
The F4U-1D will start losing turnrate but gain turn radius with any notch of flaps past the 2nd notch
The F4U-1C will start losing turnrate but gain turn radius with any notch of flaps past the 2nd notch
The F4U-1A will start losing turnrate but gain turn radius with any notch of flaps past the 2nd notch
The F4U-4 will start losing turnrate but gain turn radius with any notch of flaps past the 2nd notch ( <--- have to go double check this )
The F4U-1 will continue to gain turnrate/radius all the way to full flaps, or shall I say once the 1st notch of flaps goes out in the F4U-1 it remains constant all the way thru full flaps......
remember to find the best sustained turnrate includes both turn rate & turn radius combined....... you might be turning a tighter circle yet it is taking you longer to complete that turn......... the F4U-1 is the only one that does not get worst past the 2nd notch being deployed............although I am not advocating for people to always go "full flaps" either...
fly your plane to your strengths, and capitalize on your enemy's weaknesses......... going to full flaps in most cases means you got in over your head to begin with and are pulling out all stops to change the tide back to your favor......
YMMV.....
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Raptor's diagram attributes a distinct "nose down pitch" to pretty much all the flap types when deployed.
In AH, all flap types generate a distinct "nose up pitch" when deployed.
So, which is right?
In AH, I would have to say that people flying with CT turned on or flying their plane out of trim, is what pitches the nose up when they drop a notch of flaps......... on the other hand, in my experience, I could drop 1, 2, 3, 4 notches and do not see a notable difference of nose-up pitch when dropping the flaps......
so again, I would relate that to how you are flying with no trim / manual trim or in most cases CT ( Combat Trim )
YMMV.......
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TC I think Boozeman is referring to the common tendency of low wing monoplanes to pitch down when adding flaps and the fact that it seems this isn't the case in AH. Specifically he asked why certain flap types were noted to have a pitch down moment while AH aircraft all pitch up. If you look at the RAF POH for the Tempest or the Mustang III for example, they specifically state that the flap effect on trim is nose down. The POH for the F4U states that the flap effect on trim is "tail heavy at small flap angles, and nose-heavy at large flap angles." i.e. nose up for small, nose down for large.
Using auto trim of any sort would mask this. If you manually trim for level flight and drop flaps you see the nose go up for all 3 aircraft in AH. This is correct for the F4U for small angles of flaps but it pitches up for all flap settings.
Maybe it's modeled and I just don't see it. I believe that the pitch up is from the flap effect of increasing the AOA and consequently the lift. If the pitch moment of the flaps isn't modeled I don't know that it's worth complicating the flight equations further to add it. This isn't a training simulator for vintage warbirds. Maybe HiTech will chime in and clear it up for us.
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Yes, FLS..... I basically was saying that CT does not take in to account the use of flaps....this is why most people see the nose pitch up ( in all AH planes )........
that is how I understand it being, although my understanding could be completely wrong...( I do not think it is though, and I am stubborn :devil )
edit: where I said:
on the other hand, in my experience, I could drop 1, 2, 3, 4 notches and do not see a notable difference of nose-up pitch when dropping the flaps......
I trim at a level speed of 325 to 340 IAS, in the F4U series AH planes, and then leave it there........... however right or wrong that is, does not matter to me, that is how /where I myself feel I gain the best performance from the AH F4U........also why I do not see a Nose Pitch-Up when I drop flaps...again my own personal experience.......however right or wrong it is...
got to get up and wing with you ole muskies sometime, would be fun :aok
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I'll look forward to it TC. Look for us on Saturday nights and we'll tune. :old:
I never use CT so I can't comment on it. The pitch up occurs with manual trim for level flight so even if Boozeman uses CT it doesn't change his question. I took it as a flight model question rather than a best performance in AH type question. Now that I'm thinking about it I'm curious. Some of the things that are modeled are very hard to notice since so many forces are working together or in opposition.
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my apologies for chiming in, but could you re-post or link to Hammer's graphic? I have not seen that one yet......
I misspoke... It was Badboy's graphic. Its buried in that threadnaught discussion that Gaston started about turning circles...
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The CT does not have a noticable effect on this. The pitch-up is the same.
There is a very simple test everyone can do:
Take a P-38, take off, trim for level flight, accelerate to just shy of 250 on WEP, and then dial in flaps all the time. one stage will pop after another as the speed goes down and watch the P-38 do a beautiful looping without the slightest control input. With a bit of throttle management on the way down, you can essentially loop a 38 this way until it rus of of fuel, without control input. If that is no indication for a very distinct nose-up pitch, I dont know what is.
You can do the same with an F4U too, you just have to trim out the engine tourqe.
And dont let me start what a distinct advantage the 2 factors (nose-up pitch + high flap deployment speed) have in a stall fight. The question is, is it legitimate?
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According to the P-38 POH adding flaps makes the control wheel nose heavy (pitch down) and increases lift ( pitch up). Adding flaps has the effect of increasing AOA so why wouldn't your nose go up the same as if you'd pulled your stick back?
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I would be stunned to see a real WW2 era monoplane loop continuously just from dropping flaps. :eek:
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I would be stunned to see a real WW2 era monoplane loop continuously just from dropping flaps. :eek:
So what do you suppose would happen if you were trimmed for level flight within your loop entry speed and dropped flaps? Given that flaps have the effect of increasing AOA and lowering stall speed.
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i thought flaps usually decreased the AOA ...
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Since extending flaps increases your lift for the same speed and pitch, you have to trim nose down to continue flying level. You might think this means you decreased your AOA instead of thinking that you effectively increased the incidence of the wing so you adjust for that by lowering your nose.
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According to the P-38 POH adding flaps makes the control wheel nose heavy (pitch down) and increases lift ( pitch up). Adding flaps has the effect of increasing AOA so why wouldn't your nose go up the same as if you'd pulled your stick back?
Increasing lift is not what makes a pitch-up moment on the aircraft. Dropping flaps on most aircraft in-game does induce a nose-up pitching moment--very important to understand the difference. HTC has mentioned that flap-induced pitching moments are not necessarily modelled correctly in-game. I'm not sure what the issue is, but he hinted in another thread that they were looking at a method to correct it.
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Please explain the difference. :headscratch:
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Given that flaps have the effect of increasing AOA and lowering stall speed.
Flaps increase camber, not AOA.
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Since extending flaps increases your lift for the same speed and pitch, you have to trim nose down to continue flying level. You might think this means you decreased your AOA instead of thinking that you effectively increased the incidence of the wing so you adjust for that by lowering your nose.
You do not climb because of extra lift, you climb as a result of excess power. If the airplane maintained the same speed after flap extension you would have to reduce power to maintain level flight. Any power change will requires a trim adjustment.
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You do not climb because of extra lift, you climb as a result of excess power. If the airplane maintained the same speed after flap extension you would have to reduce power to maintain level flight. Any power change will requires a trim adjustment.
Why do you suddenly have excess power?
Flaps increase camber, not AOA.
How is the effect of more camber different from the effect of increased AOA?
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Increasing lift is not what makes a pitch-up moment on the aircraft. Dropping flaps on most aircraft in-game does induce a nose-up pitching moment--very important to understand the difference. HTC has mentioned that flap-induced pitching moments are not necessarily modelled correctly in-game. I'm not sure what the issue is, but he hinted in another thread that they were looking at a method to correct it.
link?
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Increasing lift is not what makes a pitch-up moment on the aircraft. Dropping flaps on most aircraft in-game does induce a nose-up pitching moment--very important to understand the difference. HTC has mentioned that flap-induced pitching moments are not necessarily modelled correctly in-game. I'm not sure what the issue is, but he hinted in another thread that they were looking at a method to correct it.
Just to clarify my question, I understand that the pitch down moment from flap extension is not caused from the increase in lift. I don't know if HTC models the change in location of the center of pressure from flap extension on a cambered airfoil but I assume that the pitch up in Aces High is caused by increased lift.
What I don't understand is the interaction of a pitch down moment and the increased lift when extending flaps. The P-38 POH mentions both and I don't expect it would drop it's nose and climb.
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link?
I'm trying to find it. It was in the thread where we went around and around over whether or not the elevators provided an up trim force or a down trim force.
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Just to clarify my question, I understand that the pitch down moment from flap extension is not caused from the increase in lift. I don't know if HTC models the change in location of the center of pressure from flap extension on a cambered airfoil but I assume that the pitch up in Aces High is caused by increased lift.
What I don't understand is the interaction of a pitch down moment and the increased lift when extending flaps. The P-38 POH mentions both and I don't expect it would drop it's nose and climb.
Well, this is where things start to get complicated. You are correct in identifying the discrepancy between the P-38 POH and what happens in-game. The P-47 does the same thing--there may be others that should but don't--I don't know. Not all aircraft will experience a nose-down pitching moment from flap deployment. I'll go ahead and profess I won't be able to describe the entirety of issues within a short post. The best thing I can recommend is to do some reading online. Even Wiki has some decent aerodynamics pages. Ultimately the net pitching moment of the aircraft includes a lot of variables, but read about both the center of pressure, aerodynamic center, and pitching moments. What happens in the P-38 POH is that using the flaps creates a negative (nose down) net pitching moment, whereas what happens in-game is a positive (nose up) net pitching moment.
To answer your last question though, Like Colombo said, flaps increase camber, not AoA. Generally speaking, camber increases lift at the same angle of attack, so that at an even lower angle of attack, the wing could produce the same lift, theoretically. So, you could have a lower angle of attack without sacrificing lift generation, and ultimately, this is another benefit of flaps for landing, as a steeper approach can be made (increasing the pilots view of the runway environment) without sacrificing lift generation.
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Why do you suddenly have excess power?
Since extending flaps increases your lift for the same speed and pitch, you have to trim nose down to continue flying level.
You don't have excess power in your example, therefore no climb.
Excess power is that above what is needed to maintain altitude at a specific speed. You can slow the airplane and get a sustained climb at a lower airspeed without increasing power. If you increase power and maintain airspeed you will climb. And, of course, if you reduce power and maintain airspeed you descend. Climb comes from power, not lift. Lift equals weight in unaccelerated flight.
How is the effect of more camber different from the effect of increased AOA?
Camber is the shape of the wing, AOA is the angle of the chord line to the relative wind.
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To answer your last question though, Like Colombo said, flaps increase camber, not AoA. Generally speaking, camber increases lift at the same angle of attack, so that at an even lower angle of attack, the wing could produce the same lift, theoretically. So, you could have a lower angle of attack without sacrificing lift generation, and ultimately, this is another benefit of flaps for landing, as a steeper approach can be made (increasing the pilots view of the runway environment) without sacrificing lift generation.
You're partially right. Extending flaps does increase camber but it also increases AoA. AoA is determined by the angle between the wing chord line and relative wind. The chord line is an imaginary line drawn from the leading to trail edge. As the flaps are lowered, the trailing edge is lowered changing the angle between the chord line and relative wind, i.e., AoA. As flaps are lowered this increase in AoA and C/L will usually cause an airplane to "balloon" upwards during the deployment (especially if you're relatively fast when you drop the flaps) so the nose needs to come down to counteract this and lower the AoA. Essentially, flaps change the angle of incidence of the wing (angle between the chord line and aircraft centerline) so it changes the pitch attitude required for a specific AoA. This is why a properly trimmed aircraft will have a lower pitch attitude with flaps down then it has with them up.
Also to answer the question of the difference on the effect of increased camber vs increased AoA...well they both are means to increase C/L. The question is how much lift do you need and at what speed? A thin, relatively flat wing cannot generate a C/L as high as an equivalent highly cambered wing. The problem is that a highly cambered wing is "fat' and you've got to push that through the air which is easier with a thin wing. Flaps let you have both, a thin low drag wing for speed and a thick high C/L wing at low speeds.
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A tendency to pitch nose-down rather than up would be a benefit to flap-using planes. The nose up pitching tendency is quite awkward to fight against when trying to fly/gain a guns solution, the nose down tendency is not in my experience.
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does it not also effect the efficiency of the flap? or efficiency using the flap
as your wing camber changes so does your angle off your most efficient chord line(in most planes the line of the wing re the horizontal stab (i am thinking) ...
so would not your efficiency suffer more in climbing and turning here as you are "pulling" up even more against your new nose down "natural" state of flight.
obviously the lift improves but here is another reason for drag as most planes can't change the angle of attack of it's horizontal stab so it would be in a skid.
don't the flaps and assumed associated lower speeds adversely effect the achievable and or sustainable AOA?
errr does it make pulling the nose up and or keeping the nose up more difficult?
t
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Horizontal stab and a skid?
It will mean a different A.o.A. which makes a different lift, so some difference to the elevators.
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... I'll go ahead and profess I won't be able to describe the entirety of issues within a short post...
Ya I don't know either. :headscratch: Do you think the P-38 climbs while pitching down? The POH suggests that there is a small pitch down within the greater lifting force but maybe I'm misunderstanding it. Hard to imagine adding lift and losing altitude although I know the flap extension requires a trim change. I'm wondering if the effective change in incidence can change the pitch attitude down while increasing the AOA.
I still see no reason to think the P-38 looping behavior is incorrect even if it's not the proper way to fly a loop.
Colmbo you consistently miss the point and define basic concepts that we already know. I'll try to be easier to understand.
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You're partially right...Essentially, flaps change the angle of incidence of the wing (angle between the chord line and aircraft centerline) so it changes the pitch attitude required for a specific AoA.
Thanks for the clarification vis a vis AoA. I have a tendency to think of the chord line and angle of incidence as "fixed". Still, the "balloon" effect is not common to all aircraft. Like we've discussed before, introducing flaps in the P-38 and P-47 as two examples, should introduce a noticeable nose-down pitchiing moment, per their respective POH's. Yet, in-game, there is a conspicuous nose-up pitching moment.
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Stoney:
HTC has mentioned that flap-induced pitching moments are not necessarily modelled correctly in-game.
Center pressure,Cl,Cd,Zero Lift angle, Max AOA are all accounted for with change of flap settings.
We currently do not account for the change in the Cm curve.
HiTech
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Stoney:
Center pressure,Cl,Cd,Zero Lift angle, Max AOA are all accounted for with change of flap settings.
We currently do not account for the change in the Cm curve.
HiTech
Do you use the Cl curve for the tailplane instead of the Cm curve?
...I have a tendency to think of the chord line and angle of incidence as "fixed". Still, the "balloon" effect is not common to all aircraft. Like we've discussed before, introducing flaps in the P-38 and P-47 as two examples, should introduce a noticeable nose-down pitchiing moment, per their respective POH's. Yet, in-game, there is a conspicuous nose-up pitching moment.
Another interesting thing that happens when extending flaps and increasing the incidence of the flapped section is that the washout increases so the flapped section of wing stalls first. This lets the ailerons remain effective further into the stall.
So if the P-38 pitches down with flap extension it's setting a higher trim speed with a higher coefficient of lift and if left alone it will nose up when it exceeds that trim speed? I can see where that might be a problem in a loop if it pitched down for every flap setting. Aircraft like the F4U that pitch up with larger flap angles would do better.
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How the flaps are changing the wing airfoil effective AoA and plane attitude.
(http://fdm4bge.1g.fi/kuvat/pics/Flaps_AOAs.jpg/full)
Edit
I made another render with yellow effective AoA angle line and hopefully with more descriptive texts.
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A tendency to pitch nose-down rather than up would be a benefit to flap-using planes. The nose up pitching tendency is quite awkward to fight against when trying to fly/gain a guns solution, the nose down tendency is not in my experience.
Actually, I find the nose up pitching moment to be beneficial in this scenario. Say you need just a few more degrees of lead for your shot, dropping another notch of flaps can pitch the nose up nicely. Also, the nose up pitching moment helps in coming over the top inverted. If you are a little too slow the nose can kind of "park" just a little nose high, dropping flaps can help you get the nose around nicely.
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Horizontal stab and a skid?
It will mean a different A.o.A. which makes a different lift, so some difference to the elevators.
yes assuming the stab and wing are into the airflow at the same angle when the flaps are not deployed,
and the deployment of the flaps pitches the plane (up or down) in level flight then the stab in most planes being fixed would then not be inline with the airflow (skid)
no?
t
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Stoney:
Center pressure,Cl,Cd,Zero Lift angle, Max AOA are all accounted for with change of flap settings.
We currently do not account for the change in the Cm curve.
HiTech
Oh come on, am I the only one who doesn't know what this means? :joystick:
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Oh come on, am I the only one who doesn't know what this means? :joystick:
As the flaps get lowered, the pitching moment of the flapped area increases--in some cases, rather large changes occur. HTC is saying that they don't account for this change like they do the other aerodynamic forces that change as the flaps are deployed, if I understand him correctly.
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Actually, I find the nose up pitching moment to be beneficial in this scenario. Say you need just a few more degrees of lead for your shot, dropping another notch of flaps can pitch the nose up nicely. Also, the nose up pitching moment helps in coming over the top inverted. If you are a little too slow the nose can kind of "park" just a little nose high, dropping flaps can help you get the nose around nicely.
Yeah, but if you are doing more than pulling a few degrees of lead for a moment, its awkward. Say it's a crossing snapshot instead of a tracking shot. Or say you've worked your way more to the opponents six and they are at least somewhat "flopping"/abusing Neg-Gs like is typical in game. Pushing forward on the stick to fight that all the time is very awkward to me. I always plug in lots of nose-down trim as soon as it becomes apparent that I'm going to be turning with some flap out, but that's an extra step and button, and the trim works rather slowly.
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Do you use the Cl curve for the tailplane instead of the Cm curve?
Another interesting thing that happens when extending flaps and increasing the incidence of the flapped section is that the washout increases so the flapped section of wing stalls first. This lets the ailerons remain effective further into the stall.
So if the P-38 pitches down with flap extension it's setting a higher trim speed with a higher coefficient of lift and if left alone it will nose up when it exceeds that trim speed? I can see where that might be a problem in a loop if it pitched down for every flap setting. Aircraft like the F4U that pitch up with larger flap angles would do better.
When I refer to a Cm curve, I am referring to the Cm curve of the airfoil section only. Not the net moments of force of the entire plane.
HiTech
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Hitech
I posted in haste I should have rephrased my question. I thought I was asking if you modeled the tail plane forces without the effect of the down wash from the main wing.
Edit: Slightly off topic. I believe you model spiral slipstream on the tail, is it possible when slow at a high AOA to drop the tail out of the slipstream?
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It's just RC of course, but every RC plane I've flown that had flaps actually pitched nose-up when they were deployed, and needed some down elevator trim to compensate. Especially if the plane was moving a bit fast.
All of them have been low-wing planes, mostly WWII fighter types, and a Piper Cherokee.
I actually wrecked an F4U due to a stall that occurred because the plane "ballooned", stalled, and spun on me when I dropped the flaps, and wasn't ready for the nose-up pitch.
Of course the airfoils are different, and thicker...
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My Grumman AA-1B would pitch down hard when I put the flaps down, and it has horribly small flaps. I had to snatch the yoke into my lap hard and use about 3 full turns of the pitch trim to relieve the yoke pressure. Of course, the 64415 airfoil has a pretty high pitching moment relative to other airfoils.
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yes assuming the stab and wing are into the airflow at the same angle when the flaps are not deployed,
and the deployment of the flaps pitches the plane (up or down) in level flight then the stab in most planes being fixed would then not be inline with the airflow (skid)
Not a skid, a skid is when the airplane is in uncoordinated flight in a turn but your point is getting there.
First, the wing always produces a nose-down pitching moment whenever it produces lift because the center of lift is behind the Center of Gravity. Remember that an airplane wants to rotate around its CG. This is nose-down moment balanced by the horizontal stab which provides a nose-up pitching moment, basically, it pushes down to counteract the upward push of the wing (how's that for a non aero description?). In stable flight, these two forces are balanced.
So, now lets say you're stabilized (not accelerating or decelerating, not climbing or descending) and trimmed for level flight with flaps up. You then drop your flaps. All flaps will always produce additional nose-down pitching moment. It's the way they work. I can actually expand that statement. All lift from the wing creates a nose-down moment regardless of whether is caused by camber or AOA because the center of lift is behind the CG. The airplane rotates around the CG and the additional lift behind the CG will want to pitch the nose down. OK, so much for the wing and flaps but what about the rest of the plane, i.e., the tail surfaces? Remember that the horizontal stab was providing a nose-up pitching moment which balanced the moment caused by the lift from the wing with flaps up but now the wing lift has increased so the nose wants to pitch down more. But what happens to the horizontal stab as the nose pitches down? It pitches up which increases the horizontal stab's AOA and increases it's lift (remember its lift acts downward) and nose up pitching moment. In other words, you can think of it as automatically trying to oppose the increased pitching moment from the wing. So, you have a nose-up pitching moment which is opposite of the nose-down moment created by the flaps. You can see that whether the plane pitches up or down is a direct result of these two relationships. If the moment from the flaps is greater than the moment from the tail then the nose will pitch down. If this is reversed, and the tail has a greater moment the airplane will pitch up.
Now, this is greatly simplified as there are several other things going on though including the effect of downwash on the tail surface. Also, this is much clearer with a diagram but I still can't upload it. I hope the verbal description hasn't confused anyone.
Mace
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Nice description Mace. Sometimes when thinking about the different forces I forget that they're combined and applied to the CG.
I would just add that, as you know, the tail is a much longer lever arm from the CG than the lever arm of the center of lift so it's in a position to be the main force in determining pitch.
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mace
First, the wing always produces a nose-down pitching moment whenever it produces lift because the center of lift is behind the Center of Gravity.
This is not a accurate statement when you are only considering the primary wing. Changing camber and hence adding lift can be done ahead of the CG. And is on most of AH's planes But life is not even close as so simple as this.
You also have a wing above or below the cg and hence any change in drag also creates a pitching moment.
Also with the change in camber the Cm, I.E. the torque created that does not have any tendency to move the airfoil, only rotate it also changes.
The sum of all these will determine the direction of pitch.
HiTech
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mace
This is not a accurate statement when you are only considering the primary wing. Changing camber and hence adding lift can be done ahead of the CG. And is on most of AH's planes But life is not even close as so simple as this.
You also have a wing above or below the cg and hence any change in drag also creates a pitching moment.
Also with the change in camber the Cm, I.E. the torque created that does not have any tendency to move the airfoil, only rotate it also changes.
The sum of all these will determine the direction of pitch.
HiTech
Just keeping it simple HT for those that aren't grasping the relationships. The fact that there are exceptions and additional complexities is why I mentioned that there is much more going on then just this simple explanation. I know you need to get into precise details like power-on/power-off, thrust line, gear extension, external stores, horizontal stab position (high, mid, low), downwash effect, twist, etc., for accurate computer modeling but it doesn't change the essential concept.
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The CT does not have a noticable effect on this. The pitch-up is the same.
There is a very simple test everyone can do:
Take a P-38, take off, trim for level flight, accelerate to just shy of 250 on WEP, and then dial in flaps all the time. one stage will pop after another as the speed goes down and watch the P-38 do a beautiful looping without the slightest control input. With a bit of throttle management on the way down, you can essentially loop a 38 this way until it rus of of fuel, without control input. If that is no indication for a very distinct nose-up pitch, I dont know what is.
I just tried this with Il-2 1946. Took out a P-38J, 50% fuel, trimmed for level flight at 250mph. First notch of flaps the nose pitches up, added more notches until they were completely out (Il-2 1946 only has 4 flap settings for P-38), and the aircraft began to loop. The first time around there was not quite enough speed to get over the top, and it nearly entered a spin, but a little aileron input prevented that. The flaps jammed in the extended position when airspeed was too great, but the aircraft continued to loop with no elevator input.
So, interesting that two sims have the same pitch-up effect for flaps on the P-38, and maybe others, too.
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Hitech
I posted in haste I should have rephrased my question. I thought I was asking if you modeled the tail plane forces without the effect of the down wash from the main wing.
Edit: Slightly off topic. I believe you model spiral slipstream on the tail, is it possible when slow at a high AOA to drop the tail out of the slipstream?
We do model wing blanking FLS.
HiTech
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We do model wing blanking FLS.
HiTech
That's cool to know...another feather, so to speak... :)
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pretty sure WB pitches down ...
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<snip>"effect of the down wash from the main wing."<snip>
How the wing down wash is effecting to the tail (elevator) during the turning?
The tail AoA is increasing/decreasing? :uhoh
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That's cool to know...another feather, so to speak... :)
We also model the change in The LCO do to the speed of an AOA change. I.E. basically increasing camber do to a changing AOA.
HiTEch
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Whenever I try to read these threads about flight modeling and principles of aerodynamics, especially when terms like CL and CM curves, AoA, LCO, and Camber start getting tossed around I'm reminded of the following bit, it's right around the 1:15 minute mark.
http://www.youtube.com/watch?v=3mJoHqmtFcQ&feature=related (http://www.youtube.com/watch?v=3mJoHqmtFcQ&feature=related)
:)