Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: Goombah on December 24, 1999, 04:53:00 PM
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To jmccaul, Pyro, and all
You, jmccaul, ask>>"Out of curiosity what are your opinions on the physics model? Not the numbers for the 51 are off etc but more along the lines of shakers comment"
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The nose of the aircraft should NOT pitch down when the flaps are applied. Flaps create increased lift the result of this should be obvious.
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and >>>"P.S on that point I remember reading the nose pitched down (as in aces high) due to airflow over the wings i.e. They are acting like a secondary elevator in the down position which will pitch the nose down as in aces high. Is this incorrect?" <<<<
GOOMBAH's REPLY:
No, this is not correct.The causes and effects are being confused, possibly because those people who have observed the change in pitch attitude following the change in flap setting are not pilots.
Here is the complete sequence of causes and effects in the example for flaps deploying down...
1.The flap comes down.
2.As Shacker stated, the lift of the wing increases and the plane attempts to "Balloon" up in altitude.
3.The EXPERIENCED pilot,anticipating this, and wishing to maintain the same altitude, will feed in forward stick pressure, as required, to pitch the nose down, in order to hold the same altitude; rolling in forward trim as required to reduce or neutralize the forward control pressure.
So you see, while the EVENTUAL result of "flaps down" IS a pitch down of the nose; the flaps only caused that indirectly...
The PILOT not the flaps, pitched the nose down.
If the pilot had not done so, the plane would have increased altitude, and the nose
(I THINK,) would possibly have pitched up if the pilot had been "hands off" of the elevator control and trim, while the flaps deployed.
(I say "I THINK", because it is second nature for pilots to do as described above, so I have no memory of what happens if the anticipatory action is not taken...Indeed, pilots who fly the same type of aircraft regularly,often roll in the correct forward trim in advance of dropping the flaps;and hold opposing (back) control pressure,... relaxing it gradually, as required, as the flaps come down.
The actual impression the pilot has, as flaps are dropped, is that the seat of his pants feels the plane trying to come up beneath him, so he dumps the stick to stop that feeling, which gives him the impression that the tail is flying up as the flaps come down.! (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif) This is POSSIBLY what led to the impression among the uninitiated, that as the flaps come down, the nose drops.
Shacker, an experienced pilot, only knew that the "flaps were acting backward", for the control he had to put in, to maintain his same traffic altitude, was just backwards to what he was accustomed to.
For Pyro, and others refining FMS...
It is reasonable to assume that you know what your market is...Children who go ZOOM ZOOM with their mouths and Uh-Uh-Uh-UH when they shoot-em-up; Ex-combat pilots; or some level of cyber pilot in between.
The above flap example shows how glaring a descrepancy can be to a knowlegeable cyber pilot, for a large group of them have owned and flown several High End simulations with reasonably accurate flight models and correct flight physics.
Aces High is ostensibly a combat flight simulation, where aircraft with varying flight characteristics are pitted against each other.
Small mismatches of FM between planes are just as glaringly incorrect in this type of simulation as they are in the reversed flap example. It can create "Uber" planes where none existed in the real world.
HTC,If you believe that the arcade player is your PERMANENT market, ignore people like Shacker, who are trying to help. If you believe that the permanent market is the cyber pilot, who is attracted to Flight simulations because he truly would like to fly, rather than make noises with his mouth, then it would behoove you to encourage Shacker to continue to contribute (possibly privately, if you fear public disagreement with your arcade players.)
To the arcade player who has confused lengthy checklists with correct flight modelling...that isn't what we are talking about. That sort of thing is another form of eye candy.
What we are talking about is the correct reaction of a flight model to the flight conditions and flight environment.
And sufficient instrumentation to detect what is occuring and sufficient controls to take the proper corrective action.
The programmers can give you option switches which you arcaders can agree to turn off to "dumb down" the simulation when you fly together on line.
This allows the more knowlegeable cyber pilot to fly against his peers in a more intricate game that demands such things as monitoring power settings, staying within the flight envelope, etc.
The two types of "game", while similar, are as different in skill level as checkers and chess. In Aces High, Chess and checker players cannot play against each other...the rules are different.
Checker players do not need or even recognise the nuances that correct flight modelling bring to the game.
They should not try to correct or censure or argue with the Chess players about FM. There is no need, for a simple option switch can determine whether it is "chess or checkers" on that server.
But if Aces High can ONLY BE a checker game, the chess players will certainly not pay a regular fee to play checkers.
Goombah
[This message has been edited by Goombah (edited 12-24-1999).]
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>The nose of the aircraft should NOT pitch
>down when the flaps are applied. Flaps
>create increased lift the result of this
>should be obvious.
Well, I'm no expert, in fact I'm no pilot, but I would like to suggest an expanation for this that I'd be interested on hearing you views on.
I am currently reading the book "Stick and Rudder" by Wolfgang Langewifsche. In it he talks about an aircrafts inate tendency to try and maintain its current speed. So if you are cruising level and suddenly increase the throttle, rather than accelerate the first tendency is to begin to climb, thus absorbing the increased thrust in climb rather than acceleration. As well, if you are cruising level and suddenly chop throttle the first tendency is to drop nose thus regaining speed through diving rather than decelerating.
In this view could it be possible that the first effect of the flaps being deployed would be to suddenly decrease speed thus causing the aircraft to have a tendency to "momentarily" want to drop its nose in a attempt to maintain its current speed.
Am I completely off the mark here?
Always willing to learn,
Wab
[This message has been edited by AKWabbit (edited 12-24-1999).]
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Ok if it is an error people pointing it out can only be helpful to HTC.
Goombah I will ask again though as I am intrested what are your opinions on the flight model, i am not talking about the comparison to flying a real plane more about how the plane flys do you feel the planes act very unrealistically and hence your comments about aces high being aimed at an arcade market. Also what prop sims do you think have a very good flight model?
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AK WABBIT...
First I agree with the speed versus pitch statements.
YOU ASK:>>"In this view could it be possible that the first effect of the flaps being deployed would be to suddenly decrease speed thus causing the aircraft to have a tendency to "momentarily" want to drop its nose in a attempt to maintain its current speed."<<
No, the first effect of flap deploymrnt is increased lift, it is not until the latter part of flap travel that the majority of the effect is drag.
Therefore the speed does not suddenly decrease, it would eventually decrease *If power were not applied, and if the pilot had not already lowered the nose.
In a "hands off" situation however, it would EVENTUALLY lose speed and the nose would drop.
Shacker stated that the effect of dropping the flaps was backwards because he was taking the proper corrective action to maintain desired traffic altitude and achieve his desired pattern speed for that flap setting.
Experience has shown him that the IMMEDIATE response to dropping flaps is a need for down elevator. the AH B17 required an immediate UP elevator response to maintain the desired flight comditions, ergo it is "backwards" and the FM is faulty.
Goombah
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To jmccaul...
My comments have all been about the validity of Shacker's postings about the FM.
Both he and I recognise that the FM is still beta thus in need of improvement. His quiery was concerned with if HTC Intends to improve it, for his first posting about it was about six months ago, and the answer at that time and the subdsequent lack of change in those areas of the FM gives rise to a reasonable doubt in Shacker's mind.
It would be counter productive for me to compare Aces High to other flight simulation games at this time for it is still in the development stage.
I did not mean to infer that Aces High is aimed at the arcade market, I only recognised that it is their perogative to choose their market and develop their product to match it.
The apparent emphasis on other areas over the past six months has given the impression that the FM does not enjoy the priority that is normal for a high end flight simulation.
I personally want to see Aces High succeed, thus my concern.I believe that is also Shackers's concern, though I have never met him.
I defend him because he brings a kowledgeable approach to FM testing and has been pilloried for it by theorists and others with no practical flying experience.
>>Also what prop sims do you think have a very good flight model? <<
Sorry,Sir, It is contrary to my policy to publicly open that can of worms and get involved in unproductive debates in that area. (http://bbs.hitechcreations.com/smf/Smileys/default/wink.gif)
Season's Greetings!
Goombah.
[This message has been edited by Goombah (edited 12-24-1999).]
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Goombah is correct, so far as all the A/C I have flown. The nose generally tries to rise, a response that is stronger in some types than others. The automatic response is to push the nose down to maintain altitude or speed.
org
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Great choice of book AKWabbit. Stick & Rudder is the BEST book ever written on the art of flying. It dispells many of the myths & misconceptions that have developed over time about how an aeroplane flies.
I strongly suggest that RL pilots and cyber pilots check it out. You'll be doing yourself a big favour!
Cheers
Bradburger
[This message has been edited by Bradburger (edited 12-24-1999).]
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Goombah,
It has been said and restated that these details have not been worked on and what is currently there has only been put into place to make the beta playable for now. Harping on flight model minutia despite these proclamations is accomplishing what? The B-17 doesn't even have bomb bay doors right now. Put it in perspective. There's no need to take on a condescending tone about it. That contributes nothing.
As to trim changes caused by the flaps, I haven't even done anything with that yet. I've only just started putting in real airfoil data on the different airplanes.
Now I'm no pilot, but I have flown and even soloed before I had a drivers license. Solely based on my limited flying experience, I too would say that the flaps should induce a nose up trim change. However, I've never flown any of the planes in this game and probably never will so I have to rely on various sources regarding these matters. This is an old argument btw, because it is counter to many people's experiences in whatever planes they pilot in real life.
Let's look at some various pilot manuals and notes and see what they say. The British always seem to make a note of this so most of my citings will come from those because I don't want to go digging right now.
A-20 Change of Trim
Undercarriage down- Nose down
Flaps Down- No change
P-51 Change of Trim
Undercarriage down- Nose down
Flaps down- Nose down
Hurricane Change of Trim
Undercarriage down- Nose slightly down
Flaps down- Nose down
Sea Fury
Undercarriage down- Nose slightly down
Flaps down- Nose down
B-25
Undercarriage down- Nose down
Flaps down- Nose up
P-47
Lowering landing gear- No change.
Lowering flaps- Becomes slightly nose heavy.
F6F
Lowering of the landing gear tends to make the airplane slightly nose-heavy.
Lowering of the wing flaps tends to make the airplane nose-heavy.
As you can see it's not the same for all aircraft. FWIW, I do believe that the 17 does pitch up when flaps are deployed and when the time comes to get into that, I'll certainly look it up.
Merry Christmas. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
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Doug "Pyro" Balmos
HiTech Creations
"The side with the fanciest uniforms loses."
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Pyro have you considered trying to track down pilots who have flown these birds and get thier opinions on the flight models? Just wondering
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Pyro
You say...
>>It has been said and restated that these details have not been worked on and what is currently there has only been put into place to make the beta playable for now.<<
Until you called that to my attention earlier today I was not aware of that... I got into this discussion a few days ago in defense of a knowledgeable person who was attempting to provide useable information to you and was being pilloried by people less qualified.
Also his natural puzzlement at lack of even rudimentary tools for assessing the FM was being ignored by you.
>>" Harping on flight model minutia despite these proclamations is accomplishing what? The B-17 doesn't even have bomb bay doors right now. Put it in perspective. There's no need to take on a condescending tone about it. That contributes nothing.<<<
I answered a question asked me directly by one of the members of this forum. "Harping" hardly falls into that category.
With no provision for accurately checking the performance of the B17, Shacker was forced to use the flaps anomaly as an example.
>>>As to trim changes caused by the flaps, I haven't even done anything with that yet. I've only just started putting in real airfoil data on the different airplanes.<<<
If you had stated the areas you wanted feedback on in the first place, instead of using the broad term "beta", Shacker in all liklihood would not have attempted to assess the flight model for you.
>>Now I'm no pilot, but I have flown and even soloed before I had a drivers license. Solely based on my limited flying experience, I too would say that the flaps should induce a nose up trim change. However, I've never flown any of the planes in this game and probably never will so I have to rely on various sources regarding these matters. This is an old argument btw, because it is counter to many people's experiences in whatever planes they pilot in real life.<<
As part of his defense to his detractors, Shacker stated that he had recently flown the B17 for several hours, including pattern time. I too have time in the B17 as well as several other multi-engine prop driven aircraft and some jets.All I have flown required nose down trim when the flaps were being extended.
>>Let's look at some various pilot manuals and notes and see what they say.<<
At least Shacker can now be assured that you intend to do some research when the time comes for you to start working on the FM's.
After this feedback from you, I am less concerned about the ultimate form this simulation will take.
You see I earnestly hope that I will want to sign up for regular sessions when it has ceased to be a free"Beta". I wish you all success with this enterprise.
I feel sure that when Shacker reads your feedback to me, he will understand that this phase of your testing is not concerned with the FM and he will no longer be so disturbed.
This whole misunderstanding grew out of the assumption that feedback was needed in the FM area of the testing.
TO ALL...
I feel no need to post further on this subject...
Thank you for your interest.
And a Merry Christmas to you as well, Pyro!
Goombah
[This message has been edited by Goombah (edited 12-24-1999).]
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There's more to it than just 'lift'. The things that must be considered are as follows:
1. How does the camber of the airfoil change? This directly affects the pitching moment coefficient of the airfoil. It will always be a nose down effect based on this alone. A symmetrical type airfoil (B-17) will change more than an already heavily cambered airfoil (P-38).
2. What is the aspect ratio of the wing? A higher aspect ratio with a narrower chord is less sensitive to factor #1 (more nose up or less nose down tendency). So a P-38 would tend to nose up more (or down less) than an F4u say...My R/C model (f4u) is neutral in this regards...R/C twin otter pitches up like crazy..R/C B-24 and Typhoon are also very close to neutral. CG and tail surface area has a lot to do with it as well.
3. CG position: A CG that is on or forward of the center of lift will cause a nose down pitching moment...opposite if the CG is behind the center of lift (which in most cases it is somewhat...at least on fighter types)
4. Downwash on the stab: The downwash adds negative angle of attack to the stab, tending to raise the nose. Depending on the surface area of the tail and how it balances with all other factors will determine if the plane pitches up or down with flaps.
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Re: Stick & Rudder...
It's not entirely correct. The ends are correct, but not the means.
That's similar to ancient scientists seeing a rock move and saying "It is trying to find it's place", when in fact it is inertia. The end results are similar, but the means are not the same.
The reason you climb with you increase thrust is becuase of Bernouli's principle applied to the airflow over the wings. the faster the speed, the more lift a wing produces. The slower the speed, the less lift a wing produces. That is why when you speed up, you climb, and when you slow down you dive. (steeply or shallowly, it varies)
Also, The elevators do not control climbing and diving. They control speed. Elevators control pitch of the wing, which controls speed. You angle down, you speed up. You angle up, you slow down. It has to do with the AoA, lift, and the wing, etc...
Mind you, the speed-affects-lift example is with an unchanged elevator. And the elevators-affects-speed example is with an unchanged throttle.
-Freelancer
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Goombah
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>>Also what prop sims do you think have a very good flight model? <<
Sorry,Sir, It is contrary to my policy to publicly open that can of worms and get involved in unproductive debates in that area.
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In the words of Mrs. Doyle, ahhhhh go on, go on go on go on go on go on.
and if you've never seen father ted (shame on you) in my own words: spill the beans.
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Well's Nice post except you forgot CP change effectivly moveing your center of lift.
Freelancer:
Sorry but lift and climb are 2 completly different things. Infact in a steady state climb you are generating less lift than in level flight. Easyest way to visualize it is picture a plane with more thrust than weight flying straight up. If the wing's were generating any lift at all in that state the plane would be continueing in a loop. In a steady state climb lift needed is related to the COS of the climb angle, The other force apposing gravity is thrust which is based on the SIN of the climb angle.
Btw Freelance after a 2nd reading of your post you might be refering to a simple vel vector change i.e. pitch up /pitching down do to speed changes. In which case you are 100% correct for normal cl / cg setups. But it is also posible to configure a plane that does not change pitch with speed. And thus requires no trim changes with speed.
HiTech
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Question to pyro or hitech,
Pyro mentioned how different planes reacted differently to flaps, I was wondering weather, once the flaps part of the FM is in place, the pitch response to flaps for each individual plane will fall out the model or if this sort of detail has to be added manually?
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214,
I have talked to some vets, but that only gives you one person's perspective. We like to think of these things as being black and white, but the problem is that everybody perceives those things differently. An excellent book to get an insight to this is the transcripts of the Joint Fighter Conference. A bunch of different pilots got together in 1944 and flew-off different planes and gave their reports on them. Some pilots might rank a certain plane excellent in a particular category while another pilot ranks it poor in the same category. The range in reported stall speeds may be 20 mph. It's a good text to show how subjective all this is even when it's trying to be objective.
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Doug "Pyro" Balmos
HiTech Creations
"The side with the fanciest uniforms loses."
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Oh lord... I really shouldn't do this. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
I've spent most of my adult life building and flying airplanes. I'm also a soaring fanatic.. and I eat, live, sleep and breathe airfoils. Without pointing any fingers; allow me to shed some light.. if I can.
When the airfoil is flapped; its inherent AoA is changed. Try this.. draw a typical airfoil on a piece of paper. Draw a straight line thru the leading edge to the trailing edge. For simplicity, and without using techincal lingo so all the boys and girls out there can get the picture we'll call this the 'waterline' of the wing. An aircraft always trys to 'fly' the 'waterline' level.
Next; flap the airfoil. Draw a line from the leading edge to the trailing edge. Guess what.. the 'waterline' of the wing changed.. and the nose just pitched DOWN.
Why do HP aircraft have slats? So when they deploy flap; the slats lower; preserving the mean chord level; killing pitchdown; and the additional undercamber on the airfoil develops more lift at low speed without massive trim changes being required.. in short it keeps that fast airfoil controllable and producing lift at very low speeds. As I recall the first combat AC to have these were the Me262.
Flaps produce additional lift only at small deflection angles. Spill a hair too much flap; and yah just get a massive amount of drag.. no additional lift because the airflow over the airfoil has become 'unattached'. With flap as an added help to turn radius only SMALL amounts are benefical and even small deployments will affect trim IMMEDIATELY resulting in some pitch down... full flap deployment is futile for the purpose of improving turn radius.
My competition sailplanes always mix some up elev trim in with flap.. getting the porportions right depends a lot on AC speed at deployment. The faster the plane is traveling; the more noticeable the pitchdown. Note that the pitchdown effect can be moderated somewhat by tailplane design.. T-tails help some with pitchdown due to the stabs placement well above the center of effort of the pitch radius; dampening pitchown.. but NOT eliminating it.
Hang
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PALE HORSES
"I looked, and behold; a Pale Horse, and it's riders name was Death, and Hell followed with him" Rev 6.8
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Hang,
The 109 and the George both had slats.
--ra--
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So did the Bf110, Swordfish, Avenger(oops slots not slats) Helldiver, Me163B had slots too, etc...
I think he must mean full-length slats, ie: the other plane's slats are only near the wingtip, not covering the inner "flapped" area of the wing(actually, the ailerons on the Bf109 and 110 are used as flaps too). The Me262 slats are part of the entire leading edge of the wing.
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Juzz!! thank you.. that is correct. The slots were fairly common.. and intended to reduce tipstall, and increase low speed stability at high AoA. Slots are un-articulated as opposed to slats which are articulated; just like flaps.
The Germans really were VERY much into soaring and refined and advanced the art by lightyears all thru the twenties and thirties; for the most part government sponsored and funded. Most of the better airfoils in use today have their roots in this era or german dominance in wing efficiency. And slats coupled with transitional airfoils as a means to control camber were first used in this enviornment.
Further, almost all of the best early war LW pilots learned to fly in gliders.. (http://bbs.hitechcreations.com/smf/Smileys/default/smile.gif)
The full length slats used on the 262 were nothing short of brilliant. They were not even controlled by the pilot.. they were actuated by a negative air pressure 'air-dam' that levered them out as airflow became unattached. An absolutly astounding development at the time. Without them, the 262 would not have been able to get airborne at all... at least not from the runways available at the time.
The concept created quite a stir in the US after the war and as the depth of engineering utilized by the 262 was examined in detail, testing at Langley's wind tunnel was done on the slat system and the entire 262's wing camber changing system was quickly adopted by development engineers here. With the advent of the swept wing (another German idea) and as materials and construction capabilites improved, the camber control system found its way on to the F86 Sabre used in Korea. And we all know how fine a job that plane did in it's role as air superioty fighter in a sea of lighter and more nimble adverarys.
Hang
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PALE HORSES
"I looked, and behold; a Pale Horse, and it's riders name was Death, and Hell followed with him" Rev 6.8
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low wing airplanes will pitch down (e.g. require nose up trim ) and high wing airplanes will pitch up (e.g. nose down trim required) These are my observations as a pilot -> gliders, and General Aviation light aircraft up to 2 tons (bout 20 types all in all)
AMEN
DW6