Aces High Bulletin Board
Help and Support Forums => Help and Training => Topic started by: df54 on July 01, 2007, 05:19:41 PM
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how is energy retention defined and how is it determined, ? also in energy fighting i have big problems bleeding the other guys energy
without bleeding mine i fly a yak 9u almost exclusively.
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Energy is short for any combination of both Potential and kinetic energies. Potential = stored energy. In the case of aircraft this means altitude.
Kinetic = motional energy. This means the energy it possesses due to its speed.
An aircraft has a finite amount of energy at any given point in time. Some as kinetic, some as potential (unless you're parked on the runway/hangar). One can be traded for the other. Speed will carry you upwards (zoom climb) and you are converting kinetic for potential. Altitude can be traded for speed - eg dive. If you run out of altitude and speed (eg wallowing on the deck) you are all but out of energy - and options.
Energy fighting is a bit of a black-art, and is considered the hardest of the 3 main styles: turn n burn, boom n zoom, energy fighting. The funny thing is we all energy fight to a degree but often without realising it. The real key to proper and deliberate energy fighting is knowing how to judge your own energy levels, and more importantly, how to judge your opponents E level. As most fights tend to be over in the first few maneuvers, its often very difficult to gauge your enemies energy level as you dont always know how much they had to start with. This is where a good level of SA (situational awareness) is critical to predictable energy fights. SA is a difficult thing to learn and takes time. So therefore deliberate and well-executed energy fighting is also difficult and takes time to master. Once you can read enemies E levels accurately, you will stand the best chance of prevailing in E fighting.
The basic premise is to maneuver in such a way as to conserve your energy, while forcing your opponent to waste theirs, and then converting your net accumulated E advantage to a kill, often by performing a maneuver which your opponent will try and fail at and thus put themselves a risk to your counter attack. Its a bit like chess, planning several moves ahead and knowing if your opponent falls into your trap or not and adjust on the fly (excuse the pun). Sounds easier than it really is and like i said it is a real black art.
Its something that is best shown than talked about. Get into the TA with a trainer and i'm sure they can help you out and give you a good grounder on which you can learn on. I run open off-peak training times Monday 5pm US Eastern. Im actually in New Zealand and its my Tues night at 9pm. If that time doesnt suit then try emailing another trainer - http://trainers.hitechcreations.com/
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Spatula hits the nail on the head. As far as bleeding the other guy's e you have to do as Spatula says and learn to recognize how much e your opponent actually has.
There are several ways to do this starting with knowing something about his aircraft. Spits for instance are very efficient and tend to maintain e well so they can be harder to beat down than some others.
Take a look at the overall tactical situation when you come across a bad guy. Did you spot him low in the vicinity of an airfield? Probably pretty low e. Did you pick him up in the distance with a few thousand feet of altitude advantage and he then descends below you for the merge? Probably high e.
These situations vary quite a bit though if you're fighting a smart guy. That 190 on the deck may actually be doing 400 mph and can zoom climb to meet your dive head on. The Pony you spotted in the distance may not actually be going as fast as you think at the merge and instead of zooming up after the merge hits you with a small radius early turn while you arc around at high speed.
As far as beating someone's e down, the biggest mistake I see is that attackers tend to be far to tentative in their attacks. A B&Z followed by a 4k extension gives the target a lot of time to climb and or regain speed lost in his defensive maneuver. I've been in many battles with "superior" aircraft where I start out in the hole only to eventually reverse the situation and end up with an altitude advantage because they failed to keep the pressure on. The worst cast for the target is the guy that gives him no break. Boom, Zoom for a few seconds and then get right back down on them.
When it comes to recognizing their e in the middle of the fight take what you know about your turn performance vs his. Lets say your planes are similar and you keep meeting each other 180 out (nose to nose). That means both of you have about the same e. On the other hand lets say you're maintaining your e and he starts to get inside your turn. He may be gaining angles on you but those angles have to come from somewhere and most likely he's used his best instantaneous turn and bled down some (maybe alot) doing it. He's thinking "sweet, I'm gaining on him" Now might be a good time to work more and more in the vertical using your excess e to gain an altitude advantage as he starts to realize he can't get his nose up because he's bled his e for angles. Look for him to start predominently nose-low turns or to go oblique instead of pure vertical....look for his flaps to come down (the further the better). Angles, attitude and configuration are probably the best overall indicators of his e.
These are just a few examples and, as Spatula mentions, e is a bit of a "black art". Do some study (there are several references on the Trainer's page) and meet up with one of us in the TA.
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I think both gave good answers on this :)
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Originally posted by df54
how is energy retention defined and how is it determined, ? also in energy fighting i have big problems bleeding the other guys energy
without bleeding mine i fly a yak 9u almost exclusively.
Let me qualify what I'm going to say by first saying that I'm not that familiar with the Yak, but...
The Yak, to me, is a lot like the Ponies. It's great at high speed, but it bleeds E very easily and is at a disadvantage at slow speed. When I fight either one, I try to get them to manuever with me, and if they do, the fight is over. If they stay fast and stick to BnZ/slashing attacks (which is what I believe they are good at), then I have a much smaller chance of killing them.
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Just a quick edit on my last paragraph above (as i cant edit it anymore). My training slot is 5am US Eastern. Not pm as i posted.
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Originally posted by df54
how is energy retention defined and how is it determined, ?
Total drag and excess power are going to be the limiting factors for how well you can retain energy. As mentioned there are two forms of energy, and likewise there are two forms of drag, parasitic, and induced. Parasitic drag is the drag inherent in your airframes design when flying straight. Note that deploying flaps will add to your parasitic drag. Induced drag is the extra drag caused by maneuvering.
Excess power can be compaired simply by looking at climb rates or acceleration data. While it has not been tested that I know of, one could quantify relative parasitic drag by timing decelleration from highest speed to top maintainable speed in level flight after a dive.
Induced drag, while its inherent quanity is also determined by the airframe design, is the factor that is controlled by the pilot. This is also the factor that is most easy to observe in combat to help judge relative E states.
One other factor that can effectively limit E retention at extreme end of kinetic energy (speed) is compressability, or high speed handling characteristics. If one plane can maintain full power while the other has to throttle back to maintain controlled flight, then the first plane was able to retain more energy.
While all of these factors can be defined mathmatically, and could be demonstrated with comparitive data, the easiest way to get a handle on the subject is through simple observation. For instance, in my P-38 I can expect to initally dive away from a co-e spit5, n1k2, or your yak. Once I continue to extend in level flight, I can expect to leave the spit5 and n1k in the dust because both will bleed off excess E quciker than me. However, I can expect your yak to slowly equalize speed and start to gain on me because your parasitic drag and excess power characteristics should be slightly better than mine.
Decelleration in level flight after a dive are where E retention characteristics are mosth pronounced, but you can also use a general knowledge of what one can expect in that situation to help determine relative E states in other situations.
Ok, so with all that covered, the answer to you second question is that you need to force the other plane to induce drag (maneuver), and then follow up with another attack before they have a chance to recover much E. At the same time, you have to manage your separation from the opponent to prevent them from gaining a guns solution before you egress out of range and set up for the next attack (that can be the tricky part aginst an experienced player). As Mace touched on, a good tactic is to "beat them down" to the deck where diving to gain speed and retian E is no longer an option.
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Energy management is almost an art form. There are many factors involved and knowing your aircraft thoroughly is one of them.
Each aircraft has its own unique drag profile and there's two distinctly different drag profiles to each aircraft; power-off and power-on.
Let's look at these in order.
Power-off drag is almost random because HTC has not modeled propeller drag at idle. I've tested this extensively and found that the aircraft with the lowest drag coefficient (the P-51) has more power-off drag than some radial powered fighters with a much greater drag coefficients.
Thus, you have to develop a feel for overall drag rather than expect it to correlate to real world drag data.
Power-on drag is vastly different, but hard to measure because speed varies considerably from aircraft to aircraft. In this regard, the P-51 bleeds speed very slowly.
Another factor is acceleration. The ability to gain E is a critical factor. If you are flying a fighter that accelerates poorly, E management becomes more important. The P-51's acceleration is only average.
Climb rate is yet another important factor. The ability to gain altitude rapidly means being able to store potential energy rapidly. The P-51's climb rate is only average.
Therefore, the P-51 is a fighter that benefits a great deal by careful E management.
So what is E management? It's a lot of things combined into a basic strategy for combat.
Avoid loading the airframe more than is required, which limits induced drag, and therefore conserves your E. This means don't pull excessive G while maneuvering.
Stay off the rudder pedals. Anything that induces yaw, increases drag. You can use rudder to speed up roll rate, but only do so if you have gained position behind the enemy's 3/9 line.
Don't throw away your altitude carelessly.
Don't use flaps unless absolutely required, and then get them back up as soon as possible.
Avoid throttling back to gain angles... If you don't get the angle, you have burned off precious E for no gain.
Don't follow enemy fighters into a prolonged vertical climb if you are at an E deficit.
E management includes working at equalizing E states with your enemy.
There are exceptions to these rules, such as when you are on the enemy's six and are trying to avoid overshooting (flying past him). However, you will not likely get on their six without good E management prior to that.
My regards,
Widewing
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Originally posted by Widewing
Power-off drag is almost random because HTC has not modeled propeller drag at idle. I've tested this extensively and found that the aircraft with the lowest drag coefficient (the P-51) has more power-off drag than some radial powered fighters with a much greater drag coefficients.
I find this statement curious. Idle drag does seem to be implemented - changing prop RPM at idle clearly reduces drag, as does having an engine stopped fully on auto-feathering planes (P38 for example.) This makes deadstick landing some heavy, low-drag aircraft a bit of a trick, and makes a P38 with one engine out require significant rudder (or a touch of throttle) to land straight.
Your comparison against "some radial powered fighters" may be affected by said fighters' enormous mass. Even though they have much higher total drag (the drag coefficient is meaningless without the frontal area), they also have much greater mass. Measuring power-off drag by measuring the decelleration of the aircraft is really measuring the mass/drag ratio, not just drag. So a lightweight aircraft with low drag may decellerate the same as a heavy aircraft with higher drag. And so despite its greatly higher drag, a P47 may decellerate much slower than a P51 - as at any given speed, its great weight allows it to carry much greater kinetic energy which it can spend overcoming its greater drag.
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Originally posted by SkyGnome
Your comparison against "some radial powered fighters" may be affected by said fighters' enormous mass.
I think Widewing may have had the La-7 in mind, which has much less mass than a P51, yet seems to hold E at least as well as a Pony (if not even better) with power off.
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Ok, at 2k alt, a coast from 300 to 200mph indicated:
LA@7390lbs
Throttle off 21:32
Throttle off & min rpm 37:59
P51@8981lbs
Throttle off 19:31
Throttle off & min rpm 38:09
So with min rpm, the mustang does retain speed a bit better. I'm not really sure why one would presume that the difference between a radial engine and an inline would neccessarilly be the determining factor between two aircraft's drag profile. The La is lighter, but also has smaller wings, no guns sticking out of the wings, etc. And the P51's fancy radiator is going to be pure drag when it's not belching out heat, too. Without some hard data on the specifics of their drag profiles, I think it's a bit much to say that prop drag is not modeled or random. It is clearly modeled, and the relationship between these two aircraft at least is within the realm of reason, and demonstrates that other factors (like prop behavior) have a huge influence on the results of testing like this.
EDIT:
Just for fun, here's a P47:
P47@14951lbs
Throttle off 28:28
Throttle off & min rpm 43:75
Makes sense to me. All that time and energy spent accellerating that mass has no problem muscling against the prop for an equally long time - and without so much prop to muscle, just pulling the beast through the air is a cakewalk for that ocean of accumulated energy.
Yak9u@7050lbs
Throttle off 15:31
Throttle off & min rpm 32:15
A little stranger here, but in line with its lower speed than a P51, even given similar horsepower and the Yak's smaller wings. Poor coeficient of drag for the poor yak, it would seem.
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Originally posted by SkyGnome
Ok, at 2k alt, a coast from 300 to 200mph indicated:
LA@7390lbs
Throttle off 21:32
Throttle off & min rpm 37:59
P51@8981lbs
Throttle off 19:31
Throttle off & min rpm 38:09
So with min rpm, the mustang does retain speed a bit better. I'm not really sure why one would presume that the difference between a radial engine and an inline would neccessarilly be the determining factor between two aircraft's drag profile. The La is lighter, but also has smaller wings, no guns sticking out of the wings, etc. And the P51's fancy radiator is going to be pure drag when it's not belching out heat, too. Without some hard data on the specifics of their drag profiles, I think it's a bit much to say that prop drag is not modeled or random. It is clearly modeled, and the relationship between these two aircraft at least is within the realm of reason, and demonstrates that other factors (like prop behavior) have a huge influence on the results of testing like this.
HiTech previously stated that max RPM prop drag is not modeled.....
Power-off testing is not done with prop pitch set at min RPM. It's tested with the prop pitch at max RPM. No one pulls back pitch in combat.
Nonetheless, there is some information to be garnered by testing at minimum RPM as I will show you later. You need a larger population to make any determinations.
As to drag, the CDo of the La-7 is greater than that of the P-51D. As best as I can determine, the CDo of the La-7 is .0233 as opposed to the Mustang's well known figure of .0176.
Physics disagrees with in game test data as well. We have a lower drag aircraft of greater mass bleeding speed faster than the higher drag, lighter fighter... Should not happen.
Here's some test data for to chew on, using the same speeds as you did, and at 3,000 feet ASL. Time to bleed speed from 300 mph TAS to 200 mph TAS.
Type / Power off max RPM / Power off min RPM
P-51D: 19.75 sec / 38.84 sec
La-7: 20.62 sec / 34.18 sec
P-40E: 16.03 sec / 24.90 sec
F4U-1A: 24.09 sec / 41.34 sec
Yak-9U: 14.16 sec / 31.28 sec
109K-4: 18.47 sec / 32.63 sec
Tempest: 16.19 sec / 27.35 sec
Note that there is no rhyme or reason to the numbers. The split between the min and max RPM on the P-51 is 19 seconds. On the P-40E it's less than 9 seconds. The Tempest's split is 11 seconds, with the Yak at 17 seconds. The Tempest has one of the greatest speed bleeds at max RPM, and still poor at min RPM. Yet, it has a CDo less than the P-40 and weighs as much as the F4U-1A. Low drag, lots of mass... Should be much better than it is.
Like I said, prop drag is not modeled, at least not in a way that makes the least amount of sense.
My regards,
Widewing
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Originally posted by Widewing
Like I said, prop drag is not modeled, at least not in a way that makes the least amount of sense.
Prop drag is modeled, or rpm changes wouldn't affect the speeds. Your problem is with how that model jives with your perception of what you should see.
The reason that you find so little correlation to the difference when using min rpm, is that min rpm varies with the aircraft. Some have wide rpm ranges, others smaller. This affects the drag generated by the prop hugely, but without some pretty hardcore data, it isn't going to be predictable. The Temp goes from 1800-3800RPM, the P51 1100-2900, so the pony's RPM reduction ability is 53% vs. 62% for the Temp. You'd also need to know the closed-throttle pumping losses of the engine in question at that rpm.
Another illustration of this is that the P38, with its fancy feathering props, takes 35:06 to decellerate 300-200 at min RPM and closed manifold, but a whopping 50:44 with the engines off and the props stopped. (Be careful measuring this, that you start fast enough to let the engines fully stop before 300mph.) Min RPM drag is not min drag for a given prop, just for that particular engine, prop, and rpm setting.
And prop drag is exactly why the Tempest doesn't coast well at idle. Its HUGE frickin' prop (now windmill) attached to a massive engine (now air compressor) gives it the ability to burn energy (speed) in whopping dollops through its propeller. That same prop that can efficiently transform well over 2000hp into thrust can do the same in reverse. Bigger windmill, bigger air pump, more power lost.
And you are still treating drag coefficients as total drag. They are drag per unit area. The LA7 has less of those units of area than the P51. Its total drag is less. It's total drag per unit mass is very similar (including propellor losses), thus the similar decelleration performances. The reason that coeficients are used when talking about drag is so that you can compare aircraft of dissimilar size. For this discussion however, we need to focus on total drag. Total drag per unit mass, including propeller losses.
An example...
The question:
You have two planes, of exactly equal weight, with the same engine and propellor. One has a Cd0 of .01, the other .05. Which will decellerate faster with throttle closed?
The answer:
You can't tell from the information given. You must know the drag area to tell. The worse drag aircraft could be very small, but ineficiently designed.
And finally, the way we're measuring here isn't measuring zero lift drag - the number you're throwing around. Flying level induces considerable drag. I also doubt that zero-lift drag numbers include the prop, or it would be a useless measure from an engineering perspective and be an ill reflection on the airframe design.
I'm glad I spent the time on this, as it was amusing. All the data that I see points at a pretty respectably modeled system, at least to the limits of our measurement capabilities and certainly the limits of combat relevance.
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Originally posted by SkyGnome
Prop drag is modeled, or rpm changes wouldn't affect the speeds. Your problem is with how that model jives with your perception of what you should see.
The reason that you find so little correlation to the difference when using min rpm, is that min rpm varies with the aircraft. Some have wide rpm ranges, others smaller. This affects the drag generated by the prop hugely, but without some pretty hardcore data, it isn't going to be predictable. The Temp goes from 1800-3800RPM, the P51 1100-2900, so the pony's RPM reduction ability is 53% vs. 62% for the Temp. You'd also need to know the closed-throttle pumping losses of the engine in question at that rpm.
Another illustration of this is that the P38, with its fancy feathering props, takes 35:06 to decellerate 300-200 at min RPM and closed manifold, but a whopping 50:44 with the engines off and the props stopped. (Be careful measuring this, that you start fast enough to let the engines fully stop before 300mph.) Min RPM drag is not min drag for a given prop, just for that particular engine, prop, and rpm setting.
And prop drag is exactly why the Tempest doesn't coast well at idle. Its HUGE frickin' prop (now windmill) attached to a massive engine (now air compressor) gives it the ability to burn energy (speed) in whopping dollops through its propeller. That same prop that can efficiently transform well over 2000hp into thrust can do the same in reverse. Bigger windmill, bigger air pump, more power lost.
And you are still treating drag coefficients as total drag. They are drag per unit area. The LA7 has less of those units of area than the P51. Its total drag is less. It's total drag per unit mass is very similar (including propellor losses), thus the similar decelleration performances. The reason that coeficients are used when talking about drag is so that you can compare aircraft of dissimilar size. For this discussion however, we need to focus on total drag. Total drag per unit mass, including propeller losses.
An example...
The question:
You have two planes, of exactly equal weight, with the same engine and propellor. One has a Cd0 of .01, the other .05. Which will decellerate faster with throttle closed?
The answer:
You can't tell from the information given. You must know the drag area to tell. The worse drag aircraft could be very small, but ineficiently designed.
And finally, the way we're measuring here isn't measuring zero lift drag - the number you're throwing around. Flying level induces considerable drag. I also doubt that zero-lift drag numbers include the prop, or it would be a useless measure from an engineering perspective and be an ill reflection on the airframe design.
I'm glad I spent the time on this, as it was amusing. All the data that I see points at a pretty respectably modeled system, at least to the limits of our measurement capabilities and certainly the limits of combat relevance.
So, you are saying that HTC has modeled "closed-throttle pumping losses of the engine"? I don't think so...
Using your approach, the F4U-4 should be among the worst. Huge prop, huge engine, large flat plate area, relatively high CDo.... Yet, it's just about the best at speed bleed.... How do you explain that?
Also, the flat plate area of the P-51D is 4.10 sq/ft, with the La-7 coming in at 4.89 sq/ft. So, the P-51 is heavier, a lower Cdo and less flat plate area... Yet it bleeds speed faster anyway... Moreover, the P-51B, with a lower CDo than the P-51D (same flat plate area) bleeds speed faster than the D model. Why is that? Another mystery?
And yes, I am using zero lift drag figures... That's what CDo represents. CDo = CD − CDi where CD is total drag coefficient for a given power, speed, and altitude minus lift induced drag. CDo for the P-51B is 0.169. Lift induced drag is accounted for.
I'll repeat again that HiTech has stated that they have not modeled prop drag. Modeling means that they made a best effort to determine what it is and plug it into the code. What they probably did was plug in an arbitrary number that they figured was adequate. What you see when you change pitch is the difference between that arbitrary number and the resulting change. I doubt if HTC has any idea what the prop drag is for any individual fighter.
Unfortunately, your argument does not explain the speed bleed characteristics in Aces High.
My regards,
Widewing
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Originally posted by Widewing
So, you are saying that HTC has modeled "closed-throttle pumping losses of the engine"? I don't think so...
As a general concept, absolutely. The thing that makes a prop spinning at higher RPM slow an aircraft down more than a prop spinning at low RPM is closed throttle pumping losses (and some friction.) This is very clearly modeled. It is probably not calculated per piston or anything.... or even necessarilly different for various aircraft. ;)
Using your approach, the F4U-4 should be among the worst. Huge prop, huge engine, large flat plate area, relatively high CDo.... Yet, it's just about the best at speed bleed.... How do you explain that?
The F4U-4 is outrageously heavy, much more so heavy than it has large flat plate area and high Cd0, I think. I have no numbers to back this up. Perhaps you can point me to your sources... ;) The F4U-4 is still a pretty slow-accellerating aircraft relative to late-war monsters, evidence of a modest power/weight ratio (indicating the decelerating effect of the prop will be modest relative to its weight.)
Also, the flat plate area of the P-51D is 4.10 sq/ft, with the La-7 coming in at 4.89 sq/ft. So, the P-51 is heavier, a lower Cdo and less flat plate area... Yet it bleeds speed faster anyway... Moreover, the P-51B, with a lower CDo than the P-51D (same flat plate area) bleeds speed faster than the D model. Why is that? Another mystery?
For the La, if what you are providing as measures for flat plate area are the same as what HTC is using for their drag model, then it would seem that something may be off. (Oh, and once you start talking flat plate area, the relative Cd0s are no longer really relevant, as that's part of flate plate area.) But if those flat plate areas are what HTC is modelling, the LA should be a bunch slower, I think. ;) What's your source for that LA number.. I'm really curious, as hard russian numbers seem as hen's teeth. (And I don't mean the XXX girls... those are easy to find..) ;)
As to the P51s, they are quite close, B: 20.97, D:21.12 in my measure (at2k). And I'd say my margin of error is ~1/2 sec (so by my measure, you could call it either way.) They are darn close, the B might be a hair slipperier, but it's lighter by ~90lbs. What exactly is the difference in Cd0 between B and D? They have slightly different engine setups, too. Regardless, they are very much the same airframe, and very much the same in performance.
And yes, I am using zero lift drag figures... That's what CDo represents. CDo = CD − CDi where CD is total drag coefficient for a given power, speed, and altitude minus lift induced drag. CDo for the P-51B is 0.169. Lift induced drag is accounted for.
Um.. You just said that Cd0 is "... minus lift induced drag". What we are measuring by flying the planes level _includes_ lift induced drag, and thus won't follow Cd0 exactly. And what we can measure includes the prop, which these numbers should not, I don't think.
I'll repeat again that HiTech has stated that they have not modeled prop drag. Modeling means that they made a best effort to determine what it is and plug it into the code. What they probably did was plug in an arbitrary number that they figured was adequate. What you see when you change pitch is the difference between that arbitrary number and the resulting change. I doubt if HTC has any idea what the prop drag is for any individual fighter.
I'd need to see the statement by Hitech to understand the meaning of that. You first said, "HiTech previously stated that max RPM prop drag is not modeled.....", which could mean that drag induced by the prop at max RPM in a dive (beyond the max level speed), when the prop would otherwise be holding the airplane back (and over-reving the engine) is not modeled. This would not be relevant in what we're currently measuring, and while being really interesting, would be very hard to measure.
But to say that prop drag is not modeled is absurd considering the overwhelming evidence to the contrary. Perhaps it is one really huge bug that makes our planes slow down quicker when the props are spinning? ;)
Unfortunately, your argument does not explain the speed bleed characteristics in Aces High.
Ehh.. perhaps not, but it's pretty close. I don't think your numbers support the La's speed, either, so perhaps it's a matter of different numbers instead of different concepts. The La is only inexplicable given your flat plate number.
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Originally posted by SkyGnome
As a general concept, absolutely. The thing that makes a prop spinning at higher RPM slow an aircraft down more than a prop spinning at low RPM is closed throttle pumping losses (and some friction.) This is very clearly modeled. It is probably not calculated per piston or anything.... or even necessarilly different for various aircraft. ;)
The F4U-4 is outrageously heavy, much more so heavy than it has large flat plate area and high Cd0, I think. I have no numbers to back this up. Perhaps you can point me to your sources... ;) The F4U-4 is still a pretty slow-accellerating aircraft relative to late-war monsters, evidence of a modest power/weight ratio (indicating the decelerating effect of the prop will be modest relative to its weight.)
For the La, if what you are providing as measures for flat plate area are the same as what HTC is using for their drag model, then it would seem that something may be off. (Oh, and once you start talking flat plate area, the relative Cd0s are no longer really relevant, as that's part of flate plate area.) But if those flat plate areas are what HTC is modelling, the LA should be a bunch slower, I think. ;) What's your source for that LA number.. I'm really curious, as hard russian numbers seem as hen's teeth. (And I don't mean the XXX girls... those are easy to find..) ;)
As to the P51s, they are quite close, B: 20.97, D:21.12 in my measure (at2k). And I'd say my margin of error is ~1/2 sec (so by my measure, you could call it either way.) They are darn close, the B might be a hair slipperier, but it's lighter by ~90lbs. What exactly is the difference in Cd0 between B and D? They have slightly different engine setups, too. Regardless, they are very much the same airframe, and very much the same in performance.
Um.. You just said that Cd0 is "... minus lift induced drag". What we are measuring by flying the planes level _includes_ lift induced drag, and thus won't follow Cd0 exactly. And what we can measure includes the prop, which these numbers should not, I don't think.
I'd need to see the statement by Hitech to understand the meaning of that. You first said, "HiTech previously stated that max RPM prop drag is not modeled.....", which could mean that drag induced by the prop at max RPM in a dive (beyond the max level speed), when the prop would otherwise be holding the airplane back (and over-reving the engine) is not modeled. This would not be relevant in what we're currently measuring, and while being really interesting, would be very hard to measure.
But to say that prop drag is not modeled is absurd considering the overwhelming evidence to the contrary. Perhaps it is one really huge bug that makes our planes slow down quicker when the props are spinning? ;)
Ehh.. perhaps not, but it's pretty close. I don't think your numbers support the La's speed, either, so perhaps it's a matter of different numbers instead of different concepts. The La is only inexplicable given your flat plate number.
I have had issues with propeller performance in Aces High for years. Let's look at the La-5FN/La-7 types. They have narrow chord, relatively small diameter props (about 10'5"). Typically a prop designed for high speed. We then look at the Bf 109K-4 with a high activity, broad chord prop of slightly greater diameter. The power loading of the 109k is better than that of the La-7. Yet, the La-7 accelerates nearly as fast (less than 0.2 seconds slower from 150 mph to 250 mph).
As to airframe drag, I have no issues with this as it certainly shows greater speed bleed than the P-51 at minimum RPM. It's deceleration at max RPM is baffling. It's lighter, and has greater drag, yet it bleeds speed slower than the ultra-slick P-51.
F4Us are equally interesting. Among the entire plane set, the F4U-4 ranks 9th in sea level acceleration. As altitude increases, it moves towards the top. So, acceleration is very strong being situated between the La-5FN and the 190D-9. The F4U-1 series occupy the middle of the plane set. Flat plate area differences between the F4U-1D and and F4U-4 are next to nothing. However, the -4 is heavier by a few hundred pounds and bleeds speed a bit faster than the -1D model. I'm not sure that this makes sense.
Despite all of the this, there is one test that shows how different drag modeling can be. Full power, high speed testing.
I took an La-7 off from a 10k field, dived down to 2k and (using manual trim as combat trim induces a climb at high speeds) 500 mph in WEP. I recorded the time needed to bleed down to 450 mph.
For the La-7, it required just 8.36 seconds to bleed off the 50 mph. In contrast, the P-51D required 19.25 seconds to slow down to 450 mph. For comparison, I also tested the P-40E @ 7.28 seconds and the 109K-4 @ 15.73 seconds. While these numbers for drag at high speed seem reasonable and in proportion based upon CDo and flat plate area, I don't see how they can be reconciled to power off drag numbers, even over the same speed range.
For example, under the same flight perimeters, but with power back to idle at max RPM, the P-51D required 5.56 seconds to scrub off from 500 mph to 450 mph. This was little different from the La-7 which required 5.48 seconds to do the same.
This odd drag behavior can be isolated to the propellers and I not sure that anyone can explain why it exists.
My regards,
Widewing
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I'll check out some high speed testing. Those results do indeed seem odd. Do you have a bomb on the La? ;)
Before your post actually, I tried F4u1D vs F4u-4, since it's the closest thing to two exact planes with a different prop, and at least in the 300-200 test, they are very close: (Oh.. this is with an F4u-4 with fuel drained to match the 11109lb weight of a 1D with 1/4 tank.)
At 2k, full rpm, throttle off
-4 22.22 -D 23.06
At 15k
-4 26.94 -D 27.69
Pretty close on both tests, with the -D holding E a hair better, if at all. Both a bit too close to the margin of error to really make any broad statement, but it looks fine to me.
I guess if there is a huge problem, it's at speed greater than max level speed. I'll play some more, though the high-speed stuff gets into a realm where the physics are complicated and poorly documented by free sources. ;)
Thanks for yet more info. :)
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As many have stated here E fighting is as much "art" as anything else. So the real "problem" lies in interpretation. All the "rules" are involite (dont break them) right up till the moment you need to. Recognizing up front that my perspective on E fighting does "break the rules" do a degree here you go...
1) E fighting differs from the other 2 "artforms" in that it is enemy dependent. In a true T&B {turn and burn} angles fight both sides are bleeding E and fighting for angular advantage. In a B&Z attack the aggressor is making highspeed passes from an energy advantage. In each case while your reading and reacting your "mission goal" is based on your actions. In an E fight your actions are primarily based on the other guy (hence all the talk on judging E state). What often is left out (IMO) is that E fighting is based on relative E state...you can "E fight" from the negative just as easily from the positive.
The primary goal of E fighting (again my opinion) is the exploitation of differential energy state. If he's "fast" you use that against him, if he's slow you use that against him. The good E fighter does both.
2) On the "offensive" work on flying from over to even, never under (unless of course you need to (again the art form part). The key is to force the other guy to evade by breaking flat or down. Never extend horizontally more the 1.5 or 2.0 from the boigie...always up...never more then 2.5 over the con. Fly the vertical "obliques" (imagine a big X)...but you really want a V with the con at the bottom.
3) on defense your goal is maintain vertical "capability and work toward creating a marginal shot window. To win you need to "lure" the other guy into a shot solution that 1) he misses and 2) forces him to expend energy inefficently while your defensive manuevering stores energy thru its natural application. So in effect over time you've "worked" the other guy to a more even E state.
Alot depends on plane capabilities etc and you need to work with one of the trainers to learn a number of things.
1) your current skill level and understanding of ACM
2) your planes strengths & weaknesses
3) the value and use of flying "lag"
As a general rule I dont worry about E state beyond the following. If he's got alot of E then he's B&Zing....threat is marginal. If he simply goes all angles then if He's positive E (to me) I'll T&B (since he's giving me the edge). If he's negative E then I'll E fight (dney the T&B and take the high ground)...
Now the time to get worried is when the other guy....comes screaming thru and gives you the "under" (or takes the under then blows on thru)...into a lazy climbing chandelle that suddenly tops on out at 2.5k or so above then rolls on in off our 8 or 4 and goes back up to position himself 1.2-1.5 just over your high 10 or 2. At this point you know the chef is in the building and the fillet knife is out and that the "other guy" is running the carving station. This is where WW or murder or another of the trainers can give you the basic fundementals you need to have a chance at turning the tables. They can also show you how to execute a reasonable E attack where the other guy never gets a break or a chance to "breath"...
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Originally posted by Widewing
This odd drag behavior can be isolated to the propellers and I not sure that anyone can explain why it exists.
Played with this a bit more. It would seem to me that the drag created by a prop at greater than max level speed would be determined by the level of pitch control available to the prop (note this is not related to the RPM range available.) Basically, one would want one's prop to be at an absurdly high pitch in this circumstance to maintain constant RPM.
This data is available for some birds (printed on the props of some American planes,) but I couldn't find enough photos to do anything meaningful.
It would certainly apear that this is modeled, and would be a pretty reasonable explaination as to why the Hamilton Standard high-activity club does so well at breakneck speeds.
What would apear to not be modeled is the RPM increase that one would expect in the props that cannot set that high of pitch - though the net affect on combat would be the same as what is modeled. Basically, you'd have to close your throttle in an effort to keep your engine from blowing up, but it seems that the game just does this automatically for you - creating the big energy sink that you see in the La7 at uber-speed. This would also explain why when you do throttle-off decelleration, things even out considerably - it's just that the La appears to be automatically closing your throttle for you in overspeed conditions (saving newbs countless engine failures).
If anyone has some prop pitch data, that'd be darn interesting to look at and compare to the game's modelling, but barring that, it's certainly valuable info that the Hamiltons are killers at very high speed.
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Originally posted by humble
As many have stated here E fighting is as much "art" as anything else. So the real "problem" lies in interpretation. All the "rules" are involite (dont break them) right up till the moment you need to. Recognizing up front that my perspective on E fighting does "break the rules" do a degree here you go...
1) E fighting differs from the other 2 "artforms" in that it is enemy dependent. In a true T&B {turn and burn} angles fight both sides are bleeding E and fighting for angular advantage. In a B&Z attack the aggressor is making highspeed passes from an energy advantage. In each case while your reading and reacting your "mission goal" is based on your actions. In an E fight your actions are primarily based on the other guy (hence all the talk on judging E state). What often is left out (IMO) is that E fighting is based on relative E state...you can "E fight" from the negative just as easily from the positive.
The primary goal of E fighting (again my opinion) is the exploitation of differential energy state. If he's "fast" you use that against him, if he's slow you use that against him. The good E fighter does both.
2) On the "offensive" work on flying from over to even, never under (unless of course you need to (again the art form part). The key is to force the other guy to evade by breaking flat or down. Never extend horizontally more the 1.5 or 2.0 from the boigie...always up...never more then 2.5 over the con. Fly the vertical "obliques" (imagine a big X)...but you really want a V with the con at the bottom.
3) on defense your goal is maintain vertical "capability and work toward creating a marginal shot window. To win you need to "lure" the other guy into a shot solution that 1) he misses and 2) forces him to expend energy inefficently while your defensive manuevering stores energy thru its natural application. So in effect over time you've "worked" the other guy to a more even E state.
Alot depends on plane capabilities etc and you need to work with one of the trainers to learn a number of things.
1) your current skill level and understanding of ACM
2) your planes strengths & weaknesses
3) the value and use of flying "lag"
As a general rule I dont worry about E state beyond the following. If he's got alot of E then he's B&Zing....threat is marginal. If he simply goes all angles then if He's positive E (to me) I'll T&B (since he's giving me the edge). If he's negative E then I'll E fight (dney the T&B and take the high ground)...
Now the time to get worried is when the other guy....comes screaming thru and gives you the "under" (or takes the under then blows on thru)...into a lazy climbing chandelle that suddenly tops on out at 2.5k or so above then rolls on in off our 8 or 4 and goes back up to position himself 1.2-1.5 just over your high 10 or 2. At this point you know the chef is in the building and the fillet knife is out and that the "other guy" is running the carving station. This is where WW or murder or another of the trainers can give you the basic fundementals you need to have a chance at turning the tables. They can also show you how to execute a reasonable E attack where the other guy never gets a break or a chance to "breath"...
Enjoyed the sub-thread on the physics end of it all, but thanks for getting back to the main subject humble :aok
SkyGnome....you would probably get alot more opinions if you took the physics part of E rentention & drag coefficients to the "Aircraft & Vehicles forum"
not that I am against it, I have enjoyed your & Widewings debates/discussion but it is getting off track of the orginal thread starters question....
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Originally posted by TequilaChaser
Enjoyed the sub-thread on the physics end of it all, but thanks for getting back to the main subject humble :aok
SkyGnome....you would probably get alot more opinions if you took the physics part of E rentention & drag coefficients to the "Aircraft & Vehicles forum"
not that I am against it, I have enjoyed your & Widewings debates/discussion but it is getting off track of the orginal thread starters question....
Heh. I figured the original question had been beaten into the ground well enough to not feel back about the hijack. ;)
And besides, it's a lot easier to discuss something with one informed and articulate person who's willing to spend a bit of time backing his conclusions rather than opening the whole thing up to 10,000 weenies to flail about. ;)
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All this controversy emanating from a thread on energy :). Before we digress to much with discussions regarding the flight model here’s my post on the original topic!
How is energy retention defined and how is it determined?[/i] Of course the answer is:
Ps = (T – D) * V / W
For in that equation derived from Newtonian physics lies the secret to the energy puzzle. Thanks to the likes of the infamous Col. John Boyd and Thomas Christie, his partner in stealing computer time for running thrust and drag calculations or the lesser-known E.S. Rutowski, fighter designers and pilots alike now grasp the importance of this simple but elegant equation. Take the following image for instance:
(http://www.tonyrogers.com/news/images/0104viper5.jpg)
Source: http://www.tonyrogers.com/news/viper_revolution.htm
The photo compares the turn rate and radius of the F-16 vs. the F-4E. The designers of the F-16 achieved this incredible turning ability as a result of comprehending this elegant equation.
So let’s unravel the mystery behind this equation! Doing so enables even us virtual pilots flying in our pixilated cockpits to extract the most out of the energy of our digital aircraft. To answer how energy retention is defined, we need to first answer the question, “what is energy?”, as well as it’s cousins work and power.
WORK:
Let’s first discuss work. Not the work that describes the Dibert-esque existence that some of us know. No, I mean what Sir Isaac called work. In physics work is the action of a force upon an object that displaces it some distance. In our world, when the aerodynamic forces of thrust, drag, lift, and weight act upon an airplane causing it to move through the air, well the airplane literally works (pun absolutely intended)!
ENERGY:
Well, for work to be performed, energy is required. Energy is the ability to perform work. It is the capacity to generate aerodynamic forces on an airplane to move it through the air. No energy, then no work. No work, then no airplane moving through the air.
Three sources of energy exist to generate aerodynamic forces that move an airplane: chemical, potential, and kinetic. An aircraft exchanges these energy types to maneuver. The following diagram represents the exchange relationship between these energy types.
(http://www.boeing.com/commercial/aeromagazine/aero_03/textonly/art/fig2.gif)
Source: http://www.boeing.com/commercial/aeromagazine/aero_03/textonly/fo01txt.html
Chemical energy (fuel) can be converted into potential (altitude) or kinetic (speed) energy. Potential energy can be traded with kinetic energy and vice versa. Ultimately to maneuver, an aircraft needs kinetic energy to do so.
There’s actually a fourth category of energy that is important to understand for airplanes as well. That is the energy left behind in the air when an airplane passes through it, which displaces the air as well as heats it up. For simplicity we’ll call this drag energy. The following diagram puts it all together:
(http://www.av8n.com/how/img48/energy-con.png)
Source: http://www.av8n.com/how/img48/energy-con.png
ENERGY RETENTION:
So what do we mean by energy retention? Energy retention is the aircraft’s ability to preserve its potential (altitude) and kinetic (speed) energy (transferred from its chemical energy) vs. the amount of energy transferred into the air as it moves through it. As depicted in the diagram above the energy imparted into the air by drag cannot be exchanged back into potential or kinetic energy, therefore this transfer of energy “bleeds” the mechanical energy (altitude and speed) of the aircraft. The greater the drag, the greater the mechanical energy bleed.
POWER:
Though a pilot can decide to re-arrange an airplane’s energy, the rate at which this energy exchanges remains finite or limited. This brings us to the concept of power. Power is the rate at which work can be done. Stated differently power is the rate of change of energy with respect to time. If we monkey around with the math related to the power concept, for an aircraft we end up with:
SPECIFIC EXCESS POWER:
Ps = (T – D) * V / W
Ah, our old friend! This happens to be the equation for the Specific Excess Power (Ps) of an airplane. Simply put specific excess power tells us the rate at which the airplane can exchange energy. It represents the difference between the rate of energy transferred to the plane from the engine (thrust) and the energy transferred (dissipated) to the air from the plane due to drag. In other words specific excess power (Ps) gives us a measure of the rate at which an airplane is gaining or bleeding energy. It is a measure of the energy balance of the combined engine/airframe for a given velocity, altitude and G-load.
When Ps > 0 the aircraft is gaining energy. The excess power can be converted into additional altitude, airspeed, or both. When Ps < 0 the aircraft is losing energy. The negative excess power will result in either loss in altitude, airspeed, or both. The larger the value of Ps above or below 0, the greater the energy gain or loss of the aircraft. Specific excess power is also a measure known as energy maneuverability.
With the right data we can plot energy maneuverability (E-M) diagrams, which tell us Ps for given flight conditions and begin to understand specific aircraft energy maneuverability characteristics. Badboy has put together many E-M charts for AH aircraft. You can do a search for postings by him to find them. He also has an informative article at SimHQ as well posted here:
http://www.simhq.com/_air/air_011a.html
I won’t belabor the topic that he’s done such a fantastic job covering.
RETAINING ENERGY:
Here are a few other tips on retaining energy:
[list=num]
- Simply put fly your aircraft in the envelope where Ps is equal to or greater than zero. This implies that there is a part of the flight envelope where you can maneuver your aircraft without bleeding any energy. Yes I said maneuver. Here’s where planes like the N1K2-J or Spitfire VIII surprise people sometimes. They assume if the plane is in a sustained turn that it’s automatically bleeding energy. This is simply untrue. If the opposing aircraft has a greater Ps rating then the one I’m flying it’s likely that in a sustained turn it can actually out-turn mine even without losing any energy. Worse yet it may even out-turn me and actually be gaining energy itself in the process.
At an absence of an EM chart to reference, you can do some simple flight tests to figure out where the Ps=0 envelope is for your aircraft. Simply fly a sustained level turn at a given configuration (weight & flaps) for a given velocity and altitude. Apply elevator (stick) input until you either bleed airspeed or lose altitude. At Ps=0 your altitude and airspeed should remain constant for a given g-load. Above or below this point you will gain or lose altitude, airspeed, or both. It should be noted that this is only good for a given altitude. Also you'll need to test this for various airspeeds because the G-load for Ps=0 changes with airspeed.
- Use 2-circle or nose-to-tail turns. This has the effect of creating more distance to travel in a turn before either aircraft is pointed at the other again. If the other plane is hellbent on gaining angles then using a nose-to-tail turn is a good way of inducing the bandit into blowing energy because they are holding as much of a maximum performance turn possible to get those angles but the longer turn results in more energy bleed in the process. On the other hand make that turn at Ps equal to or greater than zero and you’ll be maintaining or gaining energy in the process. Essentially this is one way to trade giving angles to the other guy for gaining a possible energy advantage.
- Make your maneuvers with your nose up vs. nose down. Trade in that speed for higher altitude as much as you can to store energy vs. bleeding it away to drag. You’ll be surprised at how many people don’t do this and you’ll find that you end up more on top of the fight than not.
Of course much more could be said but alas I'm out of energy writing this "novel"! ;)
Tango, XO
412th FS Braunco Mustangs
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Good thread. Did you find the answer you were seeking df54?
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So. Spitfires seem to be good E-fighters after what'Ive read so far. They (especially the Spit16) accelerate very well in addition to climbing well.
While most posts I've read elsewhere say the F4U is the one of the best (if not, THE best) E-fighters around. So how would that statement be proven if it doesn't accel. as well as the Spitfire nor climb as well?
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E fighting is a funny thing. you have a combination of raw "total energy potential" {not sure how you'd actually calculate that}....but lets say it represents the maximum potential energy a plane generates. Then you have maximum sustainable energy, then you have quickest energy augmentation, slowest Energy bleed etc....so in the end the gifted E fighter is balancing his planes capability vs the potential of the plane(s) he/she is fighting.
The hog is a tremendoud bird because it easily "converts" from B&Z to E to angles and back almost flawlessly. So the great hog driver is like a pitcher who has a 95mph fastball, a great slider and a 70 mph changeup. While he can beat you with any single pitch his real strength is his ability to get in your head.
I've actually found the A-20 to be a great E fighting trainer. I've got a couple clips that might help since they show a variety of scenarios. I'll post the 1st one here. Basically this is me tooling toward an enemy base and finding what appears to be a small mission. I think I'd already flown one bounce when it looked like things would heat up so I rolled film. The A-20 cant function as either a B&Z (you lose stuff you need) or pure T&B....so by default it has to be flown as an E fighter. If not for a bit of poor gunnery i'd have had a clean sweep in the end I think. If you go back to my earlier comments you can see the application of "neg e" e fighting. While I often have one or more cons on my 6 (inside 800 or so) the only real shot landed is basically a front QTR shot the A-20 simply cant avoid...
"prowling A-20" (http://www.az-dsl.com/snaphook/A-20/prowling A-20.ahf)
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This implies that there is a part of the flight envelope where you can maneuver your aircraft without bleeding any energy. Yes I said maneuver. Here’s where planes like the N1K2-J or Spitfire VIII surprise people sometimes. They assume if the plane is in a sustained turn that it’s automatically bleeding energy. This is simply untrue. If the opposing aircraft has a greater Ps rating then the one I’m flying it’s likely that in a sustained turn it can actually out-turn mine even without losing any energy. Worse yet it may even out-turn me and actually be gaining energy itself in the process.
This is the real key in learning to fly the "lesser" planes. Often you'll find that anytime your "in plane" your losing....even if you think your winning. This is where you get closer and closer and "stall" right as you try to comvert to lead for a shot only to see the bogie effortlessly convert to a spiral climb or just suddenly eat up your gains and fly up your tail....
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Thanks for the video humble! I can see how your E-fighting skills dwarf mine. It's amazing how you almost always kept your speed above 200 mph except during the scissors. I'll be sure to attempt the A-20 dogfights as well.
The spitfire XVI's can be very annoying to my Hog though, if they know how to use flaps properly.
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Hosenose. Acceleration and excess power are only part of the equation of retaining E. Inertia can play to the advantage of a sleak, relatively heavy weight fighter. In other words, when you dive, your a/c will have a higher terminal velocity, and when you zoom, it will take longer for drag to assist gravity in slowing it's momentum. While it takes more energy to get a heavier object in motion, it also takes more force to slow it. That, along with the fine examples dtango gave may give some insight into your spit vs f4u comparison.
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Ah yes I see. I may be flying too much like a Spitfire in my F4U then as it seems I'm too reliant on my flaps and ability to shove my plane into tight turns. I notice I'm draining a lot of speed in the process and I end up going head to head with the spit.
If I get a film (and learn how to post it here :D ) I'll show you my relatively smelly skills.
P.S. What's with the ugly looking F4U-1C we have? Not only is it weird but it seems to turn MUCH tighter than the other Hogs for the first 2 notches of flaps.
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This thread is great. It should be sticky.
Any other advice on reading enemy's E state?