Aces High Bulletin Board
Help and Support Forums => Help and Training => Topic started by: humble on June 08, 2009, 09:30:17 AM
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Thought that this might be worth throwing up here for those interested. I spent a bit of time flying the A-20 in the LWA last night. Normally from 108 to 110 on the map in question. While some attention was being paid to a VB en route most enemy activity was headed to a contested base away from my approach. This allowed me to normally arrive at a flight level of 12k or so with some measure of altitude superiority. Given the weight of the A-20 the problem here is actually scrubbing momentum not keeping E. Obviously each fight the A-20 E state does wear down over time but a few players complained in some form about it. So.....
E state is not a function of speed alone. A lot of variables come into play but E=MC2 will give U a basic idea of the true energy each plane has at a given speed. As an example a 400 mph TAS 20,000 lb A-20 has an "E state" as measured in Joules of roughly 648MM. A 9,000 lb Nikki at the same speed has a total of 291.6MM Joules. Now if we drop the A-20's speed to 350 TAS we find that it still has over 490MM Joules....
Now a lot of factors come into play and Murder/WW or some of the other trainers might want to elaborate or correct this but the reality is that your not going to climb up into a heavier plane with a lot of success vs a situationally aware pilot. Further if you have engaged and "dove out" thinking that you can just go up once you get some separation is not always true. Using the reference above a 400 mph nikki the pulls to the vertical will get run down by a 350 mph A-20....especially if the A-20 driver unloads the airframe and the nikki driver pulls even low G's in the zoom.
Now the flip side is in the low speed on the deck fight.
At 130 TAS a 20,000 lb A-20 has 68.4MM joules, a 9000 fighter has 30.8MM. At 170 the 9,000 fighter has 52.7MM Joules ....less then the 130 mph A-20 which has 117MM at 170 (for reference). So a 150 mph fighter "chasing" a 130 mph A-20 in a flat turn in energy deficient as it relates to zoom even though he is faster. Now if the A-20 is using the verticals (high/low yoyo) to drop down and then back up and gets to 170 he can easily pop up into a zoom climb that gives only a fleeting (if any) guns solution to the fighter.
Drag, sustained power and a lot more come into play but its important to understand the difference between speed and E state when engaged with a dissimilar plane.
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a 400 mph nikki the pulls to the vertical will get run down by a 350 mph A-20....especially if the A-20 driver unloads the airframe
?
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I see a lot of folks continue to pull G's in a curving climb vs establishing a zoom and relaxing stick input. The added control surface drag has an effect vs having the plane trimmed out and minimizing stick input. Basically if you establish your rate of climb and release the stick you've unloaded the airframe. A trimmed out A-20 in this condition will trundle up till airspeed falls well under 80TAS....with minimal input other then minor trim adjustment...
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It wasn't totally clear, thanks Humble.
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I pulled this out of one of the clips, it shows both the low speed zoom and kind of illustrates what I mean. This is after I've worn the energizer bunny down. I'm trying to extend out a bit away from the field with the ki in tow. I see the hog in my scan but am in a kill what you can type of a mode. Engage the ki hoping to score some quick hits (I miss my shot). The Hog drops on me while I'm chasing the Ki....as soon as I acquire him I kind of sit in lag. You can see both the ability of the A-20 to store E even at low speed and how the hogs constant G input bleeds speed. Basically I'm in what I call unloaded lag...then pull to unloaded lead and wait for the hog to pull into the shot...the A-20 has so much E that I can float it and even pull a bit for the 3rd shot when needed while still holding the ki off. He never did get a shot in the zoom and eventually another plane finished me off with me still chasing the Ki-84...
http://www.az-dsl.com/snaphook/lowspeedzoom.ahf (http://www.az-dsl.com/snaphook/lowspeedzoom.ahf)
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Good example. The F4U not only slows down faster after starting the zoom with more speed but also curves its path, reducing the distance between you two.
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It's that low G "pull" that kills most people, vs "floating" the plane when you can. Here is the immediate aftermath, I can float the A-20 enough to work a kind of vertical climbing scissor with the Ki. again I cant quite get the shot right but get a semi stabilized rear aspect out of it. I cant ever convert with the other traffic but it gives an idea of how you can use relative E state vs other attributes.
http://www.az-dsl.com/snaphook/afterthe%20zoom.ahf (http://www.az-dsl.com/snaphook/afterthe%20zoom.ahf)
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Great stuff Snap :aok
And you laughed at me carrying my "balast"!!
:noid
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:)
I wonder if there is ever a point where the extra mass overcomes the drag to provide a difference in zoom performance. I doubt it but if I did the math right 150 gal US equals 1290 lbs so that would give just over 42MM joules at 400mph - the drag.
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Am I correct in thinking that the larger the mass of an aircraft, the more energy is required to move it? I mean, a B17 has more mass than the A20 and therefore more joules to play with yet even without the effects of gravity/drag being factored in the flying fortress still needs more joules to produce the same potential energy.
An A20 at 350 TAS has 490MM, you say. So at 350 TAS the B17 must have alot more. My question is how much does this effect potential energy? Clearly a B17 at 350 TAS has less potential energy than an A20 at 350 TAS even though the value in joules is higher for the B17.
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I know I cant catch a buff that drops and then zooms....you end up hanging behind the tail gun.
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But starting equally both at 350 TAS the A20 will far out zoom the b17?
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In a vacuum, they will both zoom the same. Both have the same acceleration due to gravity.
In an atmosphere, only the drag and thrust is different. Zoom ability should be based directly on speed, drag, and thrust. And indirectly on low speed handling.
I'm not a physicist, so I might be wrong.
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Ok thank you. To humble's point, in an atmosphere. I geuss my question is:
Is there a mass 'sweet spot' where increasing the mass further would have a negative effect on potential energy (rather than a positive as in the nik2j/A-20 example)?
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:)
I wonder if there is ever a point where the extra mass overcomes the drag to provide a difference in zoom performance. I doubt it but if I did the math right 150 gal US equals 1290 lbs so that would give just over 42MM joules at 400mph - the drag.
I think you're correct about then mass not overcomming the drag! However what if the mass doesnt incur drag?
Batty,I'd say the A20 has the "potential" to use it's energy more than the B17.All A/C have a limit... :lol
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Does that not also mean the Nik2j has more potential to use it's energy than the A20, in turn? Or is there a 'sweet spot' for an aircrafts mass thats combines the best of both worlds?
Man, i hated physics class, I suck at it. Nevermind, im going to go get high! (flying for rooks)
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A couple of thoughts here.
First, not meaning to be critical, but Newton is far more applicable to the physics of aircraft flight than Einstein. Actually, I'm not even sure how you plugged aircraft speed into E=MC2 to arrive at your numbers. I think that what you're getting at, i.e., an understanding of total energy as being the result of Kinetic and Potential energy is very valid; however, the theory of relativity is more useful when you're considering the transformation of mass into energy and back, speed near the speed of light, and subatomic partical behavior but Newton rules the aviation world. The problem with the simplification of E as you've done is that it fails to take into account the physical world of aircraft including Ps and aerodynamic factors such as drag. This is done using Newton's laws plus throwing in Bernoulli, a bit of Boyle (and a quite a few others) and calculus, not Einstein.
As far as "zoom" is concerned, if you take two identical aircraft, one with full fuel (i.e., "ballast") and the other almost empty, the lighter plane will outzoom the heavier one every single time. It's a common misperception that a heavier airplane can zoom better (usually a point made by Jug pilots) but it's unfortunently just not true. The heavier weight for the same thrust means a lower Ps (thrust minus drag) and also higher induced drag. The drag can be reduced if both are unloaded to zero G in the zoom but it still doesn't make up for the differrence in Ps.
Also, if you compare a larger airplane with a smaller airplane, both with the same thrust to weight (something unlikely when comparing a bomber to a fighter), the smaller plane will outzoom the larger one because of the larger plane's greater drag.
Extra weight on an aircraft is always a detrement, it is never a positive. It always degrades Ps, turn performance, climb performance and energy retention. Extra weight = bad juju.
Let me add another note. Look at my avatar. It's a fully loaded F-14D with four AIM-54C, two AIM-7M, two AIM-9L and two external fuel tanks. I took the picture from an F-14A with just the external tanks. Even given the D's much greater thrust to weight ratio (much greater than 1:1 without stores) I easily outzoomed the D with it's extra weight.
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Mace,
I've got no problem at all with you or anyone being critical. I think "zoom" is the hardest concept for many sim pilots to grasp. The formula itself is perfectly applicable. Mass is weight and velocity speed. I converted the mph to m/s (tmes .45) but now to think of it I left the mass in lbs...should convert to grams I think to get actual joules. But the ratios should be the same....
How this stored E is tranfered to motion and specifically zoom goes beyond a pure measurement. Not only due you have the relative efficiency of the airframe but also the contribution of the engine(s) etc. The physics that the heavier the object the more "stored E" it has at a given speed should be correct. Again certainly open to correction or refinement....
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Sorry, maybe I'm being dense (a good possibility since math was never my strong suit) but I'm still not seeing where you plug aircraft speed into the equation. E is energy in Joules. M is mass (usually Kilograms) and C is a constant (the speed of light). Where did you plug in aircraft speed?
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i always thought joules was a measurement of heat energy
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for the theory of relativity yes, but Energy can be viewed as mass x velocity. I think that the formula is correct. A joule is a measure of energy:
It is the energy exerted by a force of one newton acting to move an object through a distance of one metre. So at a minimum I needed to convert pounds to Kg's. I do think that doing that the formula would be accurate.
So much more comes into play but the thought behind the post was to try and explain why a heavy plane like the A-20 appears to have inexhaustible E vs fighters. If you fly "flat" then its very inefficient and scrubs E much faster then a fighter will (which lets you pull lead at higher speeds). However if your flying it "on the X" then apparently minimal yoyo's offer tremendous conversation of E from potential to kinetic.
I know WW has covered it better and in more depth here and in the TA, but the concept of weight and its application in the zoom is tough to grasp for even good pilots. It happened to come up repeatedly last night so I thought i'd try to explain it within the limits of my capabilities.
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i always thought joules was a measurement of heat energy
The Joule is a unit of energy. Energy is energy; it doesn't matter what form that energy is in.
We could use calories if we wanted to... it'd sound a little weird, though.
... but Energy can be viewed as mass x velocity. I think that the formula is correct. ...
I think kinetic energy is 0.5 * mass * velocity^2.
Potential energy is mass * height * g.
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Mech:
In an unloaded zoom, both starting at say 400mph, an airplane with for example a lot more internal fuel would indeed out-zoom an identical airplane without the ballast.
But that extra weight would hurt every other area of aircraft performance....instantaneous and sustained turn rate and radius, acceleration, climb, and energy retention while pulling Gs,
That is why, all things considered, the guy who brings 25% fuel to a duel has an advantage over the guy with 100% onboard, despite the fact that the latter will probably have some advantage in a zoom starting co-speed.
EDIT: Mech, the "best of all possible worlds" would be an airframe that had low-drag, a light wing-loading, good power-loading, AND was just a plain massive besides...
(http://www.btinternet.com/~lee_mail/F4U-4.jpg)
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Hi Guys :)
Been awhile since I've posted here but I thought I would weigh in on the topic. Mace is absolutely right about the issue. Increased weight / mass in the grand scheme of things is a detriment to performance. If you're looking for a simple explanation for this, I haven't found an easy way to sum the relationship up. It's embedded in the complexity of the interdependent relationships between thrust, weight, lift, and drag.
If I find the time I'll post some basic modeling to demonstrate.
Cheers!
Tango, XO
412th FS Braunco Mustangs
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Again this is not "performance" per se, simply an attempt to explain how mass effects zoom. The simple unalterable reality is that no fighter in the game traveling at equal speed can outzoom an A-20....none. This in no way makes the A-20 "uber" but it is a factor that needs to be recognized when fighting one.
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I include zooms in the performance category :). And yes increased weight is a detriment to zoom, just as Mace points out. I realize the A-20 is the airplane you're wanting to address. Try zooming between a B-17 or B-24 vs. a the A-20 and you'll see. It's not weight that gives the A-20 it's zoom capability.
Sorry, I can't explain it any other way because I can't think of any other way to show it without requiring presenting some basic modeling of the physics to demonstrate why. I'd have to dust off some old spreadsheets and monkey with them to present the data and not sure I want to find the time to do that at the moment :)!
Tango, XO
412th FS Braunco Mustangs
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If only I had read this before my cry on 200 last night...oh well.. I always knew but seeing it in plan English helps me understand how these things happen. Nice post
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No question that drag and other factors enter the equation as well. I can tell you flat out that a B-17 will out zoom an A-20 from an even start....at least at higher alts. Obviously zoom is a relatively short lived event and a lot of factors come into play. Any type of a spiral climb will force a pursuer quickly out of zoom and into sustained performance. This applies to mossie, 110, p-38, jug or any other heavy plane, obviously results will vary but if your going vertical vs anything with zoom you need to be careful in how much you load the airframe....
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out of curiousity took a up a 100% + 2000 lb (internal) and a clean 25% A-20 off line. Very little difference in zoom (only did 1 of each) {level at 500 pull up at 300 true}. The heavy one held more speed but fell of at higher speed, while the light one topped out at the same alt but was significantly slower. Alt was within 100 ft. I'd say I could wring another 400 ft or so (about 10%) out of the heavy based on airspeed differential...but no question the heavier one was more susceptible to poor piloting. I got it just sightly cockeyed and the control inputs scrubbed speed and it fell off at about double the speed of the "light" A-20.
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Just did a test.
Took up P-47N, 8 guns, 425rpg, 100% internal. Tested zoom climb in my normal way, dive to 100 feet above sea level, autolevel until speed bleeds down to 400, 3g pull up until straight vertical, shift+x to hold it there until it falls off. Got back up to 5,800 feet.
Then I tried with a P-47N with 6 guns, 267rpg, and 25% internal. The result this time was a zoom back up to 6,100 feet before falling off.
So light appears to out-zoom heavy.
Now, in the world of ballistics everyone knows that a heavier bullet of the same diameter and drag coefficient, accelerated to the same muzzle velocity, will retain that velocity better. I had assumed similar principals would apply to two airplanes that are identical except for internal weight when both airplanes are in the unloaded condition. Is the increased E-bleed caused by the extra weight during the pull up to vertical what cost the heavier Jug airspeed and allowed the lighter one to out-zoom it?
And a hypothetical. You have two single engine prop airplanes. They have the same wing-loading. They have the same mass/horsepower ratio. They have the same drag/horsepower ratio (identical top speeds.). One, however, is a bigger and heavier airplane. Will it out-perform the lighter airplane in the vertical?
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I think your testing is wrong BnZs. The speeds you can build in the dives are a factor in this, not how well each loadout zoom climbs from 400mph exactly in level flight.
A correct test would be irrelavent to speed. Start at 10,000ft and dive full power till you cross 1000ft ASL then do a smooth 3G pull to shift x climb. See what happens then. I dont know what will.
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I think that there is something different going on when fighting an A20 against a more nimble fighter and, while it's related to E it isn't that the A20 has an inherent energy advantage.
Most guys who fight in the A20 (or at least fight in it well) know that they don't have a turn fighter so they will always fight an energy fight. Most fighters, when going against an A20 will almost immediately go to an angles fight thus scrubbing off much of their E giving the impression that the A20 is in some way different. It isn't, it's just that it's being flow correctly given it's capabilities. I do agree that as a bomber it's certainly unique, especially given it's flaps and ability to fight slow when necessary but within AH but it's still just an airplane that follows the same rules as the others. I've learned, when running up against good A20 guys like Humble and Cobia that an E fight works the best against them.
Just an anecdote here: I met up with a good A20 pilot a few months ago, co-alt and pretty close to co-speed. I was in a 109F and decided to go for the E fight. Over the course of a great fight I consistently gained altitude on him without getting slow and then just stayed slightly above him until I could convert my advantage to angles. Another way to look at this is that the A20 HAD to turn nose low and trade altitude for E while the 109 didn't. If the A20 retains E better than the smaller fighter then I should not have been able to do this.
When you take into consideration the advantages that the A20 does have, a saws'all gun package, good flaps, good power to weight (for a bomber) and good slow speed handling, it can certainly be a potent package and a very fun fight but more to the point guys who fly them know about E and how to use it otherwise they're just another target.
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BnZs your zoom test is actually testing zoom and climb, to test just zoom alone you need to kill the engine as you go vertical (feathering the prop too will amplify the difference). P=mv so the heavier aircraft will top out higher as it has more momentum. the lighter aircraft will top out higher in a climb test as F=ma. in a zoom-climb, the higher the thrust/weight ratio, the more significant climb is relative to zoom.
as for the hypothetical, the heavier aircraft will zoom-climb better. the have the same thrust/weight and drag so the climbrate component will be the same, the heavier aircraft has more momentum so will zoom better. :)
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I think your testing is wrong BnZs. The speeds you can build in the dives are a factor in this, not how well each loadout zoom climbs from 400mph exactly in level flight.
A correct test would be irrelavent to speed. Start at 10,000ft and dive full power till you cross 1000ft ASL then do a smooth 3G pull to shift x climb. See what happens then. I dont know what will.
Mech:
I'm trying to see how well each airplane retain converts excess speed into height. Therefore, starting with equal speeds is logical. The way I test is the closest approximation I can come up with to how zoom actually ends up being used in combat and still be a side-by-side comparison.
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BnZs your zoom test is actually testing zoom and climb, to test just zoom alone you need to kill the engine as you go vertical (feathering the prop too will amplify the difference). P=mv so the heavier aircraft will top out higher as it has more momentum. the lighter aircraft will top out higher in a climb test as F=ma. in a zoom-climb, the higher the thrust/weight ratio, the more significant climb is relative to zoom.
as for the hypothetical, the heavier aircraft will zoom-climb better. the have the same thrust/weight and drag so the climbrate component will be the same, the heavier aircraft has more momentum so will zoom better. :)
No, I do not need to kill the engine when testing zoom climb unless you expect that glide-mode combat will become common in the MA. Trying to see how well these airplanes perform in the vertical as actually used in combat you see.
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I've got no idea how you separate the "zoom" from the climb. The A-20 has very poor sustained climb performance but exceptional zoom. The P-47 is the same way. If you view pony vs jug, the pony really has to E fight the jug (especially the D11) unless the pony driver has exceptional T&B skills a jug will eat a pony up in an angles fight. I agree with Mace 100%, you never go angles with an A-20...always suck the E out then pick it apart...
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Did my JugN vs. JugN over and over, as already described.
Basically things were very close, I was always able to wring a little more out of the light Jug though. Got to be the extra E loss during the pull into vertical with the heavy jug that is doing it. When dealing with identical airplanes, I think we can safely say carrying ballast has no advantages that are worth it, but y'all already knew that. :devil
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Mech:
I'm trying to see how well each airplane retain converts excess speed into height. Therefore, starting with equal speeds is logical. The way I test is the closest approximation I can come up with to how zoom actually ends up being used in combat and still be a side-by-side comparison.
Indeed, yet the initial idea was how mass contributes to Boom and Zoom. The boom part being a diving attack where mass and momentum play a part. Does the heavier loadout provide more momentum in the dive which then translates to zoom? That is the question at stake here. Not a vertical climb test from equal starting.
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well there are 2 components to the zoom-climb, momentum and climbrate. if you want to separate and quantify the relative effects my suggestion will let you do that. if you just want the net result of both, then your method is fine.
Does the heavier loadout provide more momentum in the dive which then translates to zoom?
yes it does. whether it results in a better zoom-climb will depend on the thrust/weight of the aircraft. low thrust/weight means the heavier aircraft will zoom-climb better, high thrust/weight will mean the lighter aircraft will zoom-climb better :)
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ah good i thought it sounded right, thanks holmes. Hold fast, im doing some testing in the DA, back in 10 mins.
ok, my results are a bit boring.
In this order for the test film
1 - P47N - 8 guns full ammo - 50% fuel - min prop - max 4G on initial pull
2 - P47N - 6 guns full ammo - 50% fuel - min prop - max 4G on initial pull
3 - P47N - 8 guns full ammo - 100% fuel - min prop - max 4G on initial pull
4 - P47N - 8 guns full ammo - 100% fuel - Max power + wep - max 2G zoom climb
5 - P47N - 6 guns light ammo - 100%fuel - Max power + wep - max 2G zoom climb
http://www.freeroleentertainment.com/P47.ahf
The results to me said more weight is better for the bnz flyer, especialy in the non-powered tests. The difference in final altitude is minimal here, but so is the weight difference. I'm now off to test larger weight difs.
edit 2:
2 - P47N - 6 guns full ammo - 50% fuel - min prop - max 4G on initial pull
3 - P47N - 8 guns full ammo - 100% fuel - min prop - max 4G on initial pull
These two tests both reached 12.7k. Proving without doubt that more weight aids momentum in a zoom climb.
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BnZs your zoom test is actually testing zoom and climb, to test just zoom alone you need to kill the engine as you go vertical (feathering the prop too will amplify the difference). P=mv so the heavier aircraft will top out higher as it has more momentum. the lighter aircraft will top out higher in a climb test as F=ma. in a zoom-climb, the higher the thrust/weight ratio, the more significant climb is relative to zoom.
as for the hypothetical, the heavier aircraft will zoom-climb better. the have the same thrust/weight and drag so the climbrate component will be the same, the heavier aircraft has more momentum so will zoom better. :)
Cutting out thrust and chopping throttle, mass becomes a significant factor. But that would be an incorrect result because thrust plays a big part in the equation. As BnZ's pointed out in the world of ballistics yes greater mass will retain energy longer. But aircraft don't operate in a ballistic only regime. That's why BnZ's original test showed what it showed with the lighter aircraft topping out higher.
In the end the aircraft with the greatest average value of PS will always zoom higher. Given the same aircraft, the one with greater weight has a lowever average PS value which means the lighter aircraft will zoom higher.
Like I said, I don't know of any other way to show this without having to do some modelling to demonstrate. But of course you have the AH FM to test it out :).
Tango, XO
412th FS Braunco Mustangs
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:huh All this sounds Greek to me. Never been good at understanding physics anyways. So, here's my question...I have seen "zoom climb" referenced all over the place in the forum posts and have never really seen a good explanation or example of what a "zoom-climb" is. Is there a specific G pull for a zoom or is it a just a high speed pull into pure vertical or is there an area of AoA degree that meets the criteria for a zoom climb.
My idea of a zoom climb, for example, is a Pony dropping in on say a Jug at 450 TAS, take your shot and pull immediately into the pure vertical to gain as much alt for separation and re-attack as possible. Is this a reasonable example of a "zoom-climb"? Or would an egress of say 45 - 50 degree climb out at full power be more of a reasonable example? Call me ignorant, I just don't really get it.
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In the end the aircraft with the greatest average value of PS will always zoom higher. Given the same aircraft, the one with greater weight has a lowever average PS value which means the lighter aircraft will zoom higher.
Well my test shows otherwise. The non powered part we agree on. The full powered flight tests still produced a greater conversion of 15,000ft into a zoom climb by the havier aircraft.
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:huh All this sounds Greek to me. Never been good at understanding physics anyways. So, here's my question...I have seen "zoom climb" referenced all over the place in the forum posts and have never really seen a good explanation or example of what a "zoom-climb" is.
A Zoom Climb is basically any climb with a rate of climb is greater than your sustained climb rate (the one you can see on the charts in hangar). You are using your kinetic energy (speed) to go up, it's basically a conversion of kinetic energy into potential energy (altitude).
Of course, you will get slower and slower, and at one point this kinetic energy (speed) is exausted. Then your engine alone is responsible for taking you higher, you are now in a sustained climb.
It's like in a roller coaster: At the beginning, your car is pulled up the 1st hill by cable (=engine), until it reaches the peak. This part is a sustained climb
When the car goes over the top, dives down, and goes up again on the next hill without any cable, just by it's own momentum - that's zoom climb.
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I love these discussions. My first CO always liked to pose questions like these during All Officer Meetings and it's surpising the wide variety of interpretations and misinterpretations. One of his favorites was to ask, "assuming an F14 can fly at the speed of light and it turns its landing light on...what happens to the light? A...the light goes forward at twice the speed of light. B...the light doesn't shine at all. or C...the light goes backwards like a shock wave. I, being practical kinda guy, chose D....you rip your landing gear off.
Anyway....in these discussions you have to realize that in the real world you cannot isolate one single factor, such as momentum, and achieve much insight for the pilot into the total picture of what an airplane will do. That's why concepts and formulas such as Ps become important because they take the total of the equation including mass, thrust, drag, gravity, etc., into account to tell you what all the individual factors taken together really mean to a guy in the cockpit.
Also, a zoom climb without power is meaningless unless you're low, your engine quits and you need to bailout/eject. Overall though, other individual forces are combined in the significance of Ps. That goes to my original comment regarding Humble's suggestion regarding E=MC2. In isolation, total E doesn't really mean much, it's only when it's put to use within the context of the rest of the aerodynamic and physics equations that much meaningful information is gained. Even the idea of Energy Height is only useful as an academic means to compare two aircraft (in a relatively inaccurate comparison at that) or to use as basic instruction regarding the transformation between potential and kinetic energy but is otherwise meaningless to the guy in the cockpit because it assumes no losses and no atmosphere.
As far as the discussion regarding a dive then climb, some are missing other, more important, details while focusing on momentum. Let's take the extremes for illustration to prove the point. We start again with two identical aircraft but of different mass. For simplicity we'll assume zero thrust and drag. Both dive and then pull 4g across the bottom into a zoom. The conclusion that some have reached is that the additional weight aides the downward acceleration and this "stored" momentum helps the heavier aircraft outzoom the other.
First, the idea of "extra" acceleration in the dive is just wrong but we'll define the question as "in a pure vertical maneuver (dive or zoom), which airplane outperforms the other?" Here's a very basic point of view we should all be familiar with even without having taken physics and calculus. Acceleration in the dive and deceleration in the zoom due to gravity is identical for both, and it is completely independant on their relative weights/mass. Both planes will reach the same speeds and distance traveled in either a dive or zoom at the same time. For reference see: "Pisa, Leaning Tower Of" and "Galileo Galilli". Specifically regarding momentum (P=mV), we hold mass constant (I figure that at these speeds the conversion of mass to energy per Einstein is rather small) and the only variable is velocity and, since Galileo proved the velocity for both airplanes will be the same at each point in the curve, then momentum of the dive and climb cancel out.
More relevant to the real world and as others have pointed out, there's that "identical" 4g pull which isn't really the same for both aircraft weights. The heavier one has to pull a higher AOA to achieve the same 4G pull and creates much greater drag and E loss in the pull.
So, the dive/climb question comes out to this. Assuming identical aircraft except for weight the heavier aircraft will not zoom as high as the lighter aircraft because of losses due to drag during the pull and higher drag during any portion in which lift is being generated. That leaves us with a negative energy aspect (drag) which can only be offset by a positive energy aspect (thrust) and the heavier aircraft has inferior Ps.
For those trying to test this, the problem is most likely in technique vice physics. Pilot technique is essential when coming up with repeatable data. Small factors such as an acceleration or deceleration prior to a dive. The consistency and smoothness of a pull. Trim, finding pure vertical, etc., all makes flight test the challenge that it is.
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A guy makes a post purporting Energy as it pertains to air combat maneuvering can be expressed using Einstein's mass-energy equivalence equation and a serious discussion develops?
There must be a hidden camera around here somewhere.
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A guy makes a post purporting Energy as it pertains to air combat maneuvering can be expressed using Einstein's mass-energy equivalence equation and a serious discussion develops?
There must be a hidden camera around here somewhere.
Nothing wrong with a cordial discussion. The basic concept that the OP was getting at is correct and the transformation of kinetic into potential and back again is fundamental to maneuvering performance. Compared to multiple ongoing threads on ho's, ack hugging, and gang banging, etc., etc., I think this is an overall good thing. :D
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Guys,
I'd like to inject a little science into this discussion. The result may be surprising to some, and will demonstrate the truth of Mace's and dtango's excellent posts, and also explains Humble's contention in the original post that the much heavier A20 can outzoom a much lighter aircraft like the NIK2.
The first thing I hear you asking, is how can Mace, dtango, and humble all be right at the same time, they seem to be saying different things?
Just bear with me, I can show how they can all be right, and to do that I'm going to start with Newtons second law. f = ma. and we must resort to a little math, just to maintain clarity and credibility.
The expression f = ma is read as, force equals mass times acceleration. So if you want to figure out how an aircraft will slow down when subject to various forces, Newton's law applied to the aircraft's body axis could be written like this:
T - D - W x Sin(theta) = m a
where T = Thrust, D = total drag, W = Weight of the aircraft, m = the mass of the aircraft, a = acceleration and theta = angle of climb.
If you rearrange this equation you get:
a = g(T-D-W x Sin(theta))/W ft/s^2
So you can work out the acceleration (or deceleration) given the thrust, the drag and the weight of an aircraft for any given angle of climb.
Now assume you zoom climb two similar aircraft at the same angle we can work out how they will decelerate as follows.
Firstly let’s assume a zoom climb at about 64 degrees so that Sine(theta) = 0.9 and also assume that g = 32 ft/s^2 Also for a single engine fighter beginning the zoom at 250mph I’m going to assume a thrust of 2000lbs and drag of 1000lbs
For a 7000lb aircraft
a = 32(2000-1000-7000x0.9)/7000 = - 24 ft/s^2
Which would mean an initial loss of 16mph every second.
Now do the same calculation for the same aircraft at 9000lbs Because this is the same aircraft, the thrust and drag will be similar (drag may be a little higher) the main difference will be the increase in weight, so:
a = 32(2000-1000- 9000x0.9)/9000 = - 25 ft/s^2
Which would mean an initial loss of 17mph every second
This shows very clearly that the heavier aircraft loses speed more quickly in a zoom climb. In practice the situation will be worse for the heavier aircraft, because even if they both pull into the zoom at the same g load, the heavier aircraft will still need to produce more lift to achieve that g and its lift induced drag will therefore be greater and its deceleration will be more than the calculation above indicates, because it ignores that stage of the zoom.
So, heavier aircraft is bad? In that case, yes, but weight isn’t the only factor at play here, so let’s look at what happens if we consider a much heavier twin engine aircraft like the A20.
We now have 20,000lbs of weight, but we also have two engines, two props, and twice as much thrust! We will also have more drag, and in level flight a large chunk of the extra drag would be caused by all the extra lift needed to generate the 1g required to keep that 20,000lbs in the air. However, in a steep zoom at less than 1g, that becomes less important. For example, in a vertical zoom at zero g the induced drag for both aircraft would be zero, so I’m going to assume that the thrust for the twin engine aircraft doubles, while the drag remains the same, just for the sake of illustration. Of course that is far from the case in level flight, and profile drag would be greater, but if you disagree with my assumptions, just re-run the calculations with your own figures.
So, for the A20 we get:
a = 32(4000-1000-20000*0.9)/20000 = - 24 ft/s^2
Which is just as good as the 7000lb fighter and better than the 9000lb fighter.
That demonstrates why, for similar aircraft extra weight is always bad, but if you take the differences in thrust and drag for dissimilar aircraft into account you can sometimes get surprising results.
Hope that helps.
Badboy
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Well my test shows otherwise. The non powered part we agree on. The full powered flight tests still produced a greater conversion of 15,000ft into a zoom climb by the havier aircraft.
That's because as you were pointing out to BnZs you did your tests independent of airspeed. If you don't start at the same initial airspeed (and same altitude) then you've violated the rationale to be able to compare apples to apples. For basic equations of motion initial velocity makes a big difference in determining what your final physical position will be. Another way to put it as Mace says - differences in pilot technique :). That's why BnZ's test's and your tests are different.
I actually had the same conception regarding mass (greater mass = lower energy loss) awhile back but after being contradicted by other very reliable sources of flight performance and physics and doing some further analytical study showed me a clearer understanding of why that premise isn't quite true.
Tango, XO
412th FS Braunco Mustangs
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Thanks Badboy for the excellent post as usual sir. Badboy demonstrates as I was trying to point out originally which is we need to take the complete relationships between thrust, weight, lift, and drag into account.
He hit the nail on the head regarding the A-20 without having to resort to more exhaustive calcs to demonstrate which I was hinting at regarding not disregarding thrust ;). Very very important to include all the variables into consideration as his simple calcs demonstrate. Those two props on th A-20 make a lot more difference then what we may intuitively understand.
Tango, XO
412th FS Braunco Mustangs
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I'm not "a guy", I've got an identifiable name you can use. 2nd i'm using a formula in a generically correct manner to try and quantify a concept that is tough for many to grasp. I also made it clear in the original post that I was inviting discussion and correction as appropriate...
Now a lot of factors come into play and Murder/WW or some of the other trainers might want to elaborate or correct this
It's a very valid topic overall and i have no problems at all with my thoughts being reviewed and corrected as appropriate. To date I haven't seen anything from you here of any real value.
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Badboy,
thanks a lot, I knew we get a "sliderule" guy involved (recognizing both Mace and Dtango were on the same track). So When we look at more similiar planes like the nikki and jug or jug vs 109 how real is the "zoom" in my mind these planes have real demonstrated advantages both in game ans IRL....how large is the edge?
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Hmm, a very interesting and very informative thread!
A side topic that seems relevant here is the difference in "technique" used in the various zoom-tests. This I think also accounts for a lot of the difference in perceived performance in the game. In short, don't expect two pilots with identical planes to squeeze the same performance out of their rides, even when they both make a conscious effort to do so. One may consistantly get different results due to a consistantly different technique.
When we see that one plane zooms better in the game, it's entirely possible that one pilot simply has better technique. He's therefore able to get a plane to appear better than it really is when compared to another, at least in certain aspects. Pilot "A" may get better zoom out of a 75% fuel P47 than pilot "B" gets out of a 50% fuel P47, due to technique.
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Hmm, a very interesting and very informative thread!
+1 :aok
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Some very informative answers, thanks to the experts for correting the geuss-perts like me.
S!
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Thanks Badboy, Tango...I'd like to repeat my question though.
You have two airplanes that are similar in all of the "ratio" stuff (wing-loading, power-loading, thrust-drag). They'd have almost identical turn, climb, acceleration, and top speed right? But one is just plain bigger and heavier than the other. Would the heavier one possibly have some sort of advantage in zoom climb?
See, you hear about big, aerodynamically clean aircraft having an advantage in zoom all the time, even against smaller aircraft that may even have superior power-loading, the best example probably being the mock dogfight with a Spit described in Thunderbolt!. Is this hogwash? Now it has been demonstrated that adding dead weight to a Jug wouldn't make a better Jug, but stacking a Jug up against a Spit, it ain't just a Spit with 8,000 lbs of weight added...is the ratio of mass to total drag a significant positive factor in vertical performance at all?
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Wow,is all I can say,it's been way too long since a civil,imformative thread as this has been posted!
Mace, Humble, Tango and BB thx for the imformation provided,this has cleared up some misconseptions that I had and I'm sure others had. :aok
And snap,I'll still fly with "ballast" cuz they only get better lighter..... :rofl
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If you don't start at the same initial airspeed (and same altitude) then you've violated the rationale to be able to compare apples to apples.
Hey tango, sorry to cut this sentance out and pick at it! I have a another question. Seeing as the title states 'Weight and E state and it's role in ACMs'; Are my tests not a more accurate depiction of 'weight and E state' than an equal speed climb test?
Here is my understanding of the theory.
1) The two P47s in BnZs' test started at equal altitude and equal speed. Thus the heavier loadout has less E as the only part that counts is climb rate and power/weight ratio.
2) If both P47s are at 15,000ft at equal speed, the heavier loadout has more E.
So applied to aces high, with regard to the boom and zoom tactic (almost always involving a diving attack) the heavier loadout on two identical aircraft performs better? If the two aircraft start at equal altitude and equal speed then the control is still present in the experiment. Apples to apples, so to speak.
edit: Also, if you watch the speeds in the test I posted, they are very similar at the zenith of the dive. The difference seems to be in momentum carried into the zoom?
On the powered tests I even made the lighter loadout a slightly less G intensive pull out and it still topped out slightly before the heavy.
I'm not arguing, just trying to get my very basic understanding fine tuned by you guys.
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Nice shot.
I'm still impressed.
HONK!
Gooss
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The A-20 has the easiest gun view in the game IMO, somehow that center bar just makes things so intuitive. Add in the ammo load and center mounting and its pretty deadly out at 800 or farther. I still get surprised by it when I'm on the other side of the equation. Cobia kit me up at almost 1.0 the other week.... :salute
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Thanks Badboy, Tango...I'd like to repeat my question though.
You have two airplanes that are similar in all of the "ratio" stuff (wing-loading, power-loading, thrust-drag). They'd have almost identical turn, climb, acceleration, and top speed right? But one is just plain bigger and heavier than the other. Would the heavier one possibly have some sort of advantage in zoom climb?
Let's just for grins use Badboy's example.
His first fighter had 2000 lbs of thrust, 1000 lbs of drag, 7000 lbs of weight.
T/W = .286
T/D = 2
W/D = 7
a = 32(2000-1000-7000x0.9)/7000 = - 24 ft/s^2
Now let's take a fighter with 4000 lbs of thrust, 2000 lbs of drag, 14,000 lbs of weight.
T/W = .286
T/D = 2
W/D = 7
So ratio wise it's the same as the 1st plane but absolute weight-wise it's heavier.
a = 32(4000-2000-14,000x0.9)/14,000 = -24 ft/s^2
So no advantage (or disadvantage) due to the absolute differences in weight between the aircraft.
We must be careful here though. These are point calculations to be illustrative. Badboy picked a point flight regime that helps to explain particular concepts. I'm doing the same with the hypothetical "2nd airplane" here. In reality it gets even more complicated because thrust and drag vary with airspeed (and lift of course) which means that the ratios are dissimilar across the flight envelope and it would take more to fully evaluate the differences. 2ndly across the envelope there is actually a portion where greater mass helps but it doesn't make enough of a difference before we enter the region where greater mass is a detriment. That's why I struggle to fully explain the concepts without the use of some broader modeling.
To me the easiest way to compare the impact of weight is to isolate weight by fixing everything else which we can do by comparing essentially the same aircraft/airframe with only weight being the difference.
See, you hear about big, aerodynamically clean aircraft having an advantage in zoom all the time, even against smaller aircraft that may even have superior power-loading, the best example probably being the mock dogfight with a Spit described in Thunderbolt!. Is this hogwash? Now it has been demonstrated that adding dead weight to a Jug wouldn't make a better Jug, but stacking a Jug up against a Spit, it ain't just a Spit with 8,000 lbs of weight added...is the ratio of mass to total drag a significant positive factor in vertical performance at all?
Yes, that is an example some folks sight but I don't know if that is just misquoted context or misconstrued understanding. I don't have Thunderbolt! myself and so have no idea what the actual quote is. Of course we've just shown that if folks are attributing the zoom ability to primarily a function of weight/mass differential then it's definitely a flawed conclusion. It just doesn't come down to that or mass/drag ratio because you have to include thrust in the equation as well. Ignoring thrust would well, make this ballistics and not aeronautics ;).
Tango, XO
412th FS Braunco Mustangs
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Hey tango, sorry to cut this sentance out and pick at it! I have a another question. Seeing as the title states 'Weight and E state and it's role in ACMs'; Are my tests not a more accurate depiction of 'weight and E state' than an equal speed climb test?
Here is my understanding of the theory.
1) The two P47s in BnZs' test started at equal altitude and equal speed. Thus the heavier loadout has less E as the only part that counts is climb rate and power/weight ratio.
2) If both P47s are at 15,000ft at equal speed, the heavier loadout has more E.
So applied to aces high, with regard to the boom and zoom tactic (almost always involving a diving attack) the heavier loadout on two identical aircraft performs better? If the two aircraft start at equal altitude and equal speed then the control is still present in the experiment. Apples to apples, so to speak.
edit: Also, if you watch the speeds in the test I posted, they are very similar at the zenith of the dive. The difference seems to be in momentum carried into the zoom?
On the powered tests I even made the lighter loadout a slightly less G intensive pull out and it still topped out slightly before the heavy.
I'm not arguing, just trying to get my very basic understanding fine tuned by you guys.
Sorry batfink, I didn't look at your films (was at work :) ) so assumed the parameters of your flight tests. I assumed you were at different airspeeds basis what you said to BnZ. My bad.
Not sure what to say about the results of your tests except perhaps variations in technique that make a difference.
Here's a particular point to note however which I think is a source for part of the confusion.
2) If both P47s are at 15,000ft at equal speed, the heavier loadout has more E.
Yes this is absolutely correct. The heavier P-47 in this case has the greater TOTAL energy. However if we stop there we can end up with wrong conclusions. As former fighter pilot Dr. Ed Tomme says..
"Total energy includes mass, so it is not an accurate indicator of maneuverability [or zoom performance in our case]. (The C-5A has the most total energy!) It is energy per pound of aircraft weight, or Specific Energy (ES) which indicates an aircraft's capability to maneuver."
More relevant to our discussion is Specific Excess Power, PS that is of interest to us which represents the change of energy with respect to time. In other words though a pilot can decide to re-arrange an airplane’s total energy, the rate at which the energy exchanged is limited and determined by the PS relationship.
See this thread for more:
http://bbs.hitechcreations.com/smf/index.php/topic,209163.msg2488778.html#msg2488778
And it's this energy rate of change that we're really trying to understand which tells us the rate of energy bleed or gain. And it's this very relationship that also tells us that given the same aircraft, that apples to apples the lighter aircraft has the greater average PS vs. the heavier which means the lighter aircraft will zoom higher.
Tango, XO
412th FS Braunco Mustangs
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Thank you for that explanation sir, you make it easy to understand. The difference in technique sounds very likely. I had not even considered that the heavier/lighter aircraft would get to 4G differently due to the mass.
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Ignoring thrust would well, make this ballistics and not aeronautics ;).
Tango, XO
412th FS Braunco Mustangs
So, to make it short, any advantage that an aircraft might have when considered as a projectile is not likely to be a significant factor in vertical performance?
Second, what IS the explanation for being able to get nearly identical zoom climbs out of airplanes with widely varying power-loading, I.E, SpitXVI and F4U-1 for example?
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I watched the P47 test again and noticed something else interesting.
The second -50% 6guns non-powered test topped out at almost exactly the same altitude as the third -100% 8guns non-powered test. both were almost exactly 12.7k
- lighter aircraft stalled out and turned over at 30mph
- double the fuel load and another pair of guns, the heavy stalled and almost lost control at 55mph but a few feet higher.
That would lead us to believe that in virtual combat the lighter aircraft is still the better choice as you would need to be agile at the top to convert to an advantage, not wallowing over 20mph faster at the same altitude. This is what the experts here are making clear with math and great explanations.
The first -50% 8guns non powered test stomped the other two right up to 12.9k and dropped over neatly at 32mph.
So in moderation the extra weight may be of value. Is it fair to assume if you intend to BnZ your prey in a p47N you would be not helping yourself much taking the six gun loadout?
again though, my test was very basic and lacking multiple results for some kind of average.
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So, to make it short, any advantage that an aircraft might have when considered as a projectile is not likely to be a significant factor in vertical performance?
Not exactly but when you account for thrust in the equation it makes a significant contribution which overshadows the ballistics only way of looking at it. That's why batfink's engine idle tests show the heavier airplane zooming higher. That's what you would expect. Throw thrust into the equation and things change. For the range of thrust we're talking about for WW2 aircraft, it has a big impact.
Second, what IS the explanation for being able to get nearly identical zoom climbs out of airplanes with widely varying power-loading, I.E, SpitXVI and F4U-1 for example?
Hehe, too many factors here to make any general statements that would be correct. In other words there isn't an easy explanation I can think of that explains it for these variety of cases.
Tango, XO
412th FS Braunco Mustangs
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Just read the whole thread.
FREAKEN AWSOME!!! :aok
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So in moderation the extra weight may be of value. Is it fair to assume if you intend to BnZ your prey in a p47N you would be not helping yourself much taking the six gun loadout?
Heh, well you ought to take the guns for reasons having nothing to do with performance...their weight doesn't help near as much as the extra killing capacity helps. I suppose you could reach some point where extra .50s weren't worth the weight...maybe around 25 or so...
Anyway though, even if ballast did give some small edge in a pure zoom, as you know actually fighting with the airplane, even in a so-called "bnz" or energy fighting style isn't going to consist solely of a series of max-speed dives and unloaded zooms, not by a long shot. One will have to put loads on the airplane often during maneuvers (increased weight=increased wingloading), climb, accelerate, reduce throttle in dives to keep your speed reasonable, make use of turn performance, etc.
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So, to make it short, any advantage that an aircraft might have when considered as a projectile is not likely to be a significant factor in vertical performance?
Second, what IS the explanation for being able to get nearly identical zoom climbs out of airplanes with widely varying power-loading, I.E, SpitXVI and F4U-1 for example?
Starting with the second, the differences in power-loading are just not that big to be significant as all WWII planes have low absolute power/mass ratio. In addition, power/mass is a deceiving number. It is not the same as thrust/mass=acceleration. Your engine may be producing 2000HP, but that does not mean you will be able to put it into kinetic energy. Consider that P=F*v=m*a*v. It means that if power P is constant and you could get all this power into kinetic energy, at v~0 you get infinite acceleration, or thrust. Basically, at very low speeds your 2000HP go to kinetic energy of the AIR that goes through the prop - your HP are literally blowing in the wind. How does this translate into actual THRUST depend on the prop diameter and aerodynamics. If there is some advantage to being light and having high power/mass it is at the low speeds, but it is not as significant as one might expect.
On the other side of the scale, at high speed, the combined weight and high parasitic drag overwhelm the thrust. At these speeds, the excess power left after overcoming the drag is very low and the plane behaves more like a projectile. This gives a small advantage of low drag/mass (likely the heavy) plane, but the deceleration in this part of the zoom is highest so it passes quickly.
So now lets think in terms of absolute energy and altitude the planes will reach. When they stall at the top, all the energy is in potential energy - this total energy at the end of the zoom is what we are after. For specific energy this is proportional to the hight of the zoom.
why is it not much larger for the higher power loaded plane?
Remember that the energy gain from the engine is power*time - so two things happen here: first, the fraction of raw engine power that your airframe gains vs. the part that goes to create wind, gets smaller at low speeds. The other is that the time is short. Because the thrust/weight<<1 for all WWII planes, the time it takes for the speed to drop to zero is not very different and in any case - short, a few seconds. In this short time, even with a little better engine-power/mass you don't get to build a lot more energy/mass, or altitude, using the small fraction of engine power that goes to propelling the plane and not creating wind.
Now the first, following the discussion above. Higher mass may be advantageous in a certain range of parameters. For high enough initial speeds and low enough thrust/weight planes, it may actually work - but not likely in real life. The matter of fact is that planes are not set vertically and released and same velocities. A heavy, high wing-loaded plane will loose a lot more energy just to go from level into vertical in a maneuver that will be sharp enough not to resemble a climb through most of it.
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So basically any WWII prop plane zooming almost exactly the same from a given speed is to be expected?
Starting with the second, the differences in power-loading are just not that big to be significant as all WWII planes have low absolute power/mass ratio. In addition, power/mass is a deceiving number. It is not the same as thrust/mass=acceleration. Your engine may be producing 2000HP, but that does not mean you will be able to put it into kinetic energy. Consider that P=F*v=m*a*v. It means that if power P is constant and you could get all this power into kinetic energy, at v~0 you get infinite acceleration, or thrust. Basically, at very low speeds your 2000HP go to kinetic energy of the AIR that goes through the prop - your HP are literally blowing in the wind. How does this translate into actual THRUST depend on the prop diameter and aerodynamics. If there is some advantage to being light and having high power/mass it is at the low speeds, but it is not as significant as one might expect.
On the other side of the scale, at high speed, the combined weight and high parasitic drag overwhelm the thrust. At these speeds, the excess power left after overcoming the drag is very low and the plane behaves more like a projectile. This gives a small advantage of low drag/mass (likely the heavy) plane, but the deceleration in this part of the zoom is highest so it passes quickly.
So now lets think in terms of absolute energy and altitude the planes will reach. When they stall at the top, all the energy is in potential energy - this total energy at the end of the zoom is what we are after. For specific energy this is proportional to the hight of the zoom.
why is it not much larger for the higher power loaded plane?
Remember that the energy gain from the engine is power*time - so two things happen here: first, the fraction of raw engine power that your airframe gains vs. the part that goes to create wind, gets smaller at low speeds. The other is that the time is short. Because the thrust/weight<<1 for all WWII planes, the time it takes for the speed to drop to zero is not very different and in any case - short, a few seconds. In this short time, even with a little better engine-power/mass you don't get to build a lot more energy/mass, or altitude, using the small fraction of engine power that goes to propelling the plane and not creating wind.
Now the first, following the discussion above. Higher mass may be advantageous in a certain range of parameters. For high enough initial speeds and low enough thrust/weight planes, it may actually work - but not likely in real life. The matter of fact is that planes are not set vertically and released and same velocities. A heavy, high wing-loaded plane will loose a lot more energy just to go from level into vertical in a maneuver that will be sharp enough not to resemble a climb through most of it.
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So basically any WWII prop plane zooming almost exactly the same from a given speed is to be expected?
There will be differences of course, but look at the plane statistics. The range of power/mass, drag/mass values is not very big and as long as all the planes are underpowered, the differences are reduced even more. It is not like one will zoom twice as high as the other and disappear into the great blue yonder. We are talking about scale of 100ft or slightly more differences.
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A Zoom Climb is basically any climb with a rate of climb is greater than your sustained climb rate (the one you can see on the charts in hangar). You are using your kinetic energy (speed) to go up, it's basically a conversion of kinetic energy into potential energy (altitude).
Of course, you will get slower and slower, and at one point this kinetic energy (speed) is exausted. Then your engine alone is responsible for taking you higher, you are now in a sustained climb.
It's like in a roller coaster: At the beginning, your car is pulled up the 1st hill by cable (=engine), until it reaches the peak. This part is a sustained climb
When the car goes over the top, dives down, and goes up again on the next hill without any cable, just by it's own momentum - that's zoom climb.
Thank you sir, that explains it perfectly. :salute
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Nothing wrong with a cordial discussion. The basic concept that the OP was getting at is correct and the transformation of kinetic into potential and back again is fundamental to maneuvering performance. Compared to multiple ongoing threads on ho's, ack hugging, and gang banging, etc., etc., I think this is an overall good thing. :D
While the resulting discussion might have some value, if false information is not clearly repudiated it taints further discussion.
This is a glaringly obvious posting of bad information so it is very easy to spot.
In many other discussions it is very difficult for a beginner to differentiate between good and bad information.
I see horribly bad information posted on this forum daily that is praised as good advice.
I don't think it serves the game well for that to occur. It would be fine if this was not a venue for beginners seeking help but it is.
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It would be fine if this was not a venue for beginners seeking help but it is.
Fankly, I highly doubt that a beginner seeking help is here to learn the finer points of weight, thrust and drag as they relate to zoom climbs. More likely; what's the best plane, how do I land or how do I shake a guy off my tail.
Even though the opening premise was incorrect, or at least based on incorrect mathematics, this has developed into a great thread. If false information is posted in this forum, which, as you point out it often is, then it's the responsibility of those who have the correct answers to correct it. It seems to me that's exactly what's been done here so, no harm done and, in fact, Humble invited correction in his OP.
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While the resulting discussion might have some value, if false information is not clearly repudiated it taints further discussion.
This is a glaringly obvious posting of bad information so it is very easy to spot.
In many other discussions it is very difficult for a beginner to differentiate between good and bad information.
I see horribly bad information posted on this forum daily that is praised as good advice.
I don't think it serves the game well for that to occur. It would be fine if this was not a venue for beginners seeking help but it is.
Kiss my grits you pompous little .....
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OK....
1st and formost I greatly appreciated all the input here, now I'm trying to refine my understanding and relate the "math" to what I see as the practical application...especially in short duration "low speed" applications of mass related "E". As Mace stated early on the best way to engage an A-20 is to E fight it. When you get locked into an angles fight vs an A-20 that is not totally stripped of E it seems to be very adaptable if the pilot works his stability at high AoA...at least in my experience with it.
I can sort thru and find some more specific clips but I think the 2nd one I posted illustrates enough for discussion here. Again any/all (meaningful) comment/correction is appreciated.
At the end of the "zoom" I need to turn my attention to the Ki (I dont think my SA ever registered the 109). As the plane falls off I get lucky in that he's naturally in my initial view back since I'm falling off to the left. Initially my focus is on falling off and squaring up in a way that avoids getting shot, so I'm looking for space inside his arc...as soon as I get that angle off I'm looking to take the fight back up.
This is where I need a better grasp of both what the realities are and how I explain it. To me intuitively at the 16 second mark I'm golden. He's pulled for a shot that he cant hit and I'm going for a vertical scissor type thingie.
So at :09 on the clip i'm about topped out and in "rotate" at alt 3.0 speed 52, airframe is basically unloaded and falling of naturally with minimal inputs. At :16 he's taken his shot and we are engaged, film shows both planes at 2.5 with my speed at 145 and the Ki at 136. Now at :23 we're both showing 2.5 even though fight is going up with my speed at 125 and his at 150. At :29 as I roll back over to establish a position behind him at .2.9/85 and he is at 2.7 119...
So to me as an A-20 driver I went down, chopped throttle a bit at one point to make things "fit" angularly and popped back up while under modest G loading/control input while maintaining roughly equivalent E to my starting point while converting an angular gain of roughly 120 degrees and actually (IMO) bleeding a bit of E off the other guy. From my perspective a lot of this is due to the mass (and stability) of the a-20 in the low speed semi verticals. The flip side is that a lot of folks have commented over the years I can be a very "smooth" stick in this type of move.
So how much of this is the "zoom" (I think 80%) and how much is "smooth"?
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so...er.... where are all the threads you started to help newbies? :D
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so...er.... where are all the threads you started to help newbies? :D
Bat I could care less about what he does or doesn't do here. My "issue" is that he's basically an opportunist with minimal ACM skills. You want to fly around and pick people great, its your dime...but don't come in here and bash on stuff you've got no demonstrated ability with. I'm trying to explain something I've got some demonstrated ability with and put it in somewhat mathematical terms (no question incorrectly).
Now having sorted out a better understanding of the math, how do you break down the components. What I have gathered thanks to Mace, Badboy and dtango is that all the other factors cancel out the "zoom" very quickly. At the same time I can tell you from 1st hand experience that you can "cycle" the A-20 in the verts very efficiently if allowed. Mace and others I've run into do a very good job of making me go "the long way" as much as practical and no question the A-20 scrubs E badly in that situation. Were I can work a climbing cut back type of fight like linked the A-20 can gain both angles and E at the same time in relation to an opponent.
So...
Is this the mass, the low speed stability that allows more minimal control inputs, efficiency at those intermediate speeds compared to fighters or a combination + other factors I'm overlooking. The initial post refers to comments from others specific to sustained relatively low alt/low speed "dog fighting". I've found that if my SA holds up and i'm not forced to scrub massive E avoiding a B&Z/E attack from above I can "cycle" the A-20 for prolonged periods vs even multiple cons in a roughly co-e state. Normally either a higher inbound or a more cagey vet will loosely engage and draw the fight up via sustained climbing turn performance where I cant follow....but as long as guys are willing to furball the a-20 it just keeps chugging along.
What I'm gathering is that i have very efficient "short term" exchange within the initial flight parameters....meaning I can pop down and up within the alt band determined by initial height and some mid speed level unloaded dive that allows a very efficient recycling....but when i'm forced beyond that all the other variables offset and overwhelm that bit of "zoom" my mass generates...
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I’ve dusted off some old flight modeling spreadsheets to expound more on what Mace, Badboy, Bozon, and myself have been stating about zoom climb performance.
Specifically what we are seeing with the A-20’s energy retention in the vertical is primarily a function of it’s thrust, not it’s weight (mass).
Let’s analyze this through some basic modeling of a couple of aircraft.
P-47 @ weight = 14,500 lbs
A-20 @ weight = 16,000 lbs
A-20 @ weight = 22,000 lbs
Unpowered Zoom Climb
First let’s examine the unpowered zoom climb. The following is a graph showing a time-altitude history of our aircraft in an unpowered zoom climb where:
BHP~0 (thrust~0),
climb angle=63 degrees
g-load= 1g
initial airspeed = 400 mph,
initial altitude = 1000 ft.
(http://thetongsweb.net/images/zoom1.jpg)
The concept that many folks have in their mind is that mass (thus weight) effects energy retention. We’re taught that the greater the mass, the more it takes to accelerate or decelerate it, thus the greater the mass the slower the energy bleed. If we compare the two A-20’s, we see this at work where the heavier A-20 out zooms the lighter A-20. So far we have no surprises.
However if we over generalize the concept of greater mass = slower energy bleed we start to run into problems. We can see that even in an unpowered zoom climb that the P-47 (lighter by 8,000 lbs!) out zooms the heavier A-20. What gives? Since we have more analysis ahead, I’ll simply point out that this occurs because despite the greater weight (mass) of the A-20, the P-47 has a lower drag and drag/mass ratio compared to the A-20’s in our model.
The variance in drag-to-mass ratio should serve to remind us that we need to beware over generalization which leaves out other variables in the equation – in this case the impact of drag.
Accounting for ALL variables is important and we’ll continue to demonstrate that by now adding in thrust.
Powered Zoom Climbs
What happens when we add thrust to the equation? The following is a graph showing a time-altitude history of our aircraft in a powered zoom climb where:
BHP= (P-47: 2600hp, A-20: 2 x 1600hp)
climb angle=63 degrees
g-load= 1g
initial airspeed = 400 mph,
initial altitude = 1000 ft.
(http://thetongsweb.net/images/zoom2.jpg)
Factoring in thrust, the P-47 continues to out zoom both A-20’s. Comparing the A-20’s, the lighter A-20 now out zooms the heavier A-20. Of course on the surface this graph doesn’t tell us anything particularly interesting. After all thrust should make a difference to the zoom capabilities of our aircraft.
However let’s take a look at a time-velocity history of our powered zoom climb.
(http://thetongsweb.net/images/zoom3.jpg)
Things start to get more interesting when we compare the change in airspeeds over the course of our powered zoom climb. Comparing the A-20’s, the heavier A-20 initially bleeds airspeed just a hair slower than the lighter A-20. At some point however the heavier A-20 bleeds airspeed faster and more pronounced than the lighter A-20.
Even more interesting is that though the lighter A-20 bleeds airspeed faster than the P-47 for most of the zoom climb, there’s a cross-over point where the lighter A-20’s airspeed becomes greater than the P-47 as they near the peak of the powered-zoom climb.
Looking at the time-velocity graph we can obviously observe non-linear behavior which gives us a hint there are more complex things happening under the hood. Let’s put our propeller-head hats on, give them a spin and dive a bit deeper shall we?
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Anatomy of a Zoom Climb
What we are really interested in is analyzing the different variables in the powered zoom climb and how they impact zoom performance. To do so we first should breakdown the basic equation of motion. As Badboy points out a basic equation for forces in the axis of an airplane’s direction of flight is:
F = m*a = Thrust – Drag – Weight * sin (climb_angle)
If we solve for net acceleration of the aircraft we can re-arrange the equation to the following (similar to Badboy’s equation for acceleration):
a = Thrust/m – Drag/m – gravity * sin (climb_angle)
It’s the non-linear variation of this acceleration over time that results in the velocity curves in time-airspeed history of our powered zoom climb. Four variables influence acceleration: thrust, drag, mass, and climb angle.
Since clearing up the impact of mass on zoom climbs is a focus here let’s spend some time discussing it. As we can see in the equation the greater the mass we have, the lower the drag-to-mass ratio. This means greater mass reduces the impact of energy bleed due to drag. We can’t stop there however. At the same time, greater mass also results in a lower thrust-to-mass ratio meaning that it also reduces the ability to gain energy through thrust. We have to account for the impact of mass on all variables.
Let’s take a look at thrust/mass and drag/mass [in other words acceleration (due-to-thrust) and deceleration (due-to-drag)] over the course of the zoom climb.
(http://thetongsweb.net/images/zoom4.jpg)
This is a graph of accel(thrust) [thrust/mass] and accel(drag) [drag/mass] over the zoom climb for our aircraft. Drag/mass is plotted as a positive acceleration values for easier comparison with thrust/mass acceleration. Comparing the A-20’s we can see that increased mass (heavier A-20) lowers drag deceleration vs. the lighter A-20, but it also lowers thrust acceleration as well compared to the lighter A-20.
If we examine just the curves for a single airplane (either A-20) we make the following observations.
First, drag deceleration is a greater factor at the start of the zoom climb but quickly diminishes. This is phase of a zoom climb where greater mass helps energy retention. But it doesn’t last long.
Second, the cross-over point where thrust and drag acceleration are equal is less than 5 seconds into the zoom. The significance of this convergence point is where the impact of greater mass starts to dwindle for energy retention. Beyond this point greater mass becomes more and more of a detriment to energy retention.
Third, over the majority of the zoom climb thrust acceleration is the dominant factor in overall acceleration as evidenced by the time-history. Greater mass is a detriment during this phase and thus the majority of our zoom climb.
These component acceleration graphs give us a glimpse to individual relative contribution of variables to zoom climb performance and some of the underlying complexities. However what we want is to also better understand how these variables interact with each other IN COMBINATION between thrust, drag, mass, and climb angle and their combined effect on zoom climb performance.
As stated previously Specific Excess Power (PS) is a measure of the rate of energy change of an aircraft. It tells us the rate at which energy is gained or bled and defined as:
PS = (T – D) * V / W = change_in_alt + change_in_velocity
This is a key relationship to understand. Energy retention is a combination of these variables interacting with each other.
When PS > 0 the aircraft is gaining energy. When PS < 0 the aircraft is bleeding energy. As the PS equation demonstrates it gives a combined interaction of thrust, drag, weight (mass), airspeed, and indirectly climb angle on the rate of energy change and thus a measure of the zoom climb performance of an aircraft and it’s ability to convert speed into altitude.
The following is a graph of the PS of our aircraft in our powered zoom climbs.
(http://thetongsweb.net/images/zoom5.jpg)
Analyzing the graph we can make some observations. First at the early phases of the zoom climb we see that the heavier A-20 bleeds energy less than the lighter A-20. No doubt this reflects the contribution of greater mass. However as seen that’s short-lived and soon the lighter A-20 retains energy better than heavier A-20. This difference in energy retention dominates for the rest of the zoom climb between the A-20’s with the lighter A-20 retaining more energy. This is reflective of the significant impact of thrust on a zoom climb but also the combined effect of how greater mass limits PS of the heavier A-20 for most of the zoom climb.
A second interesting observation can be made. As can be seen the P-47 has higher PS value compared to the A-20’s until about 10 seconds into the zoom climb. An interesting thing occurs. The lighter A-20 actually begins to retain energy better than the P-47 throughout the remainder of the zoom climb. As we noted in the component breakdown, this is not due to the greater mass of the A-20 but the impact of thrust on the majority of the powered zoom climb. That being said the P-47 still has the highest average PS of all three aircraft and therefore is able to reach a higher altitude at the peak though it reaches the peak a few seconds sooner than the lighter A-20.
The lighter A-20’s PS margin in the later phases of a zoom climb I believe is the secret to it’s performance in the vertical. In our comparison we see that though it doesn’t zoom as high as the P-47, it will stay in the zoom just a bit longer.
This has a couple of potentials in air combat. First, if the P-47 was behind the A-20 and trying to follow the A-20 up, the P-47 has to solve the problem of closure and possible overshoot because it will zoom higher than the A-20. One obvious response is to chop throttle of the P-47. But now we’ve seen that this could be a bad response because thrust is a big factor of determining zoom performance for most of a zoom climb.
Second, if the A-20 is behind the P-47 instead and following the P-47 up, though the P-47 would peak higher it would peak and be on the way down while the A-20 would still be on the way up which presents all various positioning and eventual angles problems for the P-47.
So there we have it. Analyzing the PS of the aircraft in a zoom climb gives us insight into the A-20’s ability in a vertical fight. It’s not greater mass that allows it to retain energy better, but rather it’s thrust. I believe this is the secret to the success of the A-20 in the vertical.
Tango, XO
412th FS Braunco Mustangs
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Thank you. I knew there was something fundamentally wrong with using off-power zooms as a metric for E retention and zoom ability.
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excellent stuff tango, clearly shows the slight advantage of extra mass in unpowered zoom, and that the extra mass is the greater factor for the first 8s of the A20's ~24s zoom-climb, untill the thrust/mass effect overwhelms it, as predicted :aok
edit: the jug is a pretty hefty airframe though, it would be interesting to see how a much lighter fighter compares (as the thrust/mass effect will be more pronounced.) can the A20 use its mass to reel in any of our fighters in the initial phase of the zoom-climb?
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excellent stuff tango, clearly shows the slight advantage of extra mass in unpowered zoom, and that the extra mass is the greater factor for the first 8s of the A20's ~24s zoom-climb, untill the thrust/mass effect overwhelms it, as predicted :aok
edit: the jug is a pretty hefty airframe though, it would be interesting to see how a much lighter fighter compares (as the thrust/mass effect will be more pronounced.) can the A20 use its mass to reel in any of our fighters in the initial phase of the zoom-climb?
Sorry RTHolmes you're missing my point. You want to bring it back to mass for some reason. Mass only plays a small part to powered zoom climb performance and what advantage it plays early on is of little consequence. You can see that in the velocity time history between the A-20's that there is little difference in airspeed in the early parts of the powered zoom climb. You can't even see the separation distance advantage because it's only in mere feet, not even tens of feet. This all gives way very quickly and dramatically with the plane with the greater (T-D)/W ratio retaining loads more energy because greater mass has a magnifying effect of reducing zoom climb performance since thrust grows very rapidly.
More completely thrust and drag factor into the equation and it's thrust that provides most of the "energy" in a zoom climb not mass. Zoom climb performance is determined by PS of which thrust plays the dominant part in a powered zoom climb. You can see it in the PS comparisons. The difference in weight between the P-47 and the lighter A-20 is ~2000 lbs while the difference between the Jug and the heavier A-20 is a whopping ~8000 lbs. The P-47 easily out zooms the heavier A-20 by a significant margin. I don't have key data plate points needed for modeling lighter aircraft with strong thrust/weight ratios like the N1K2-J, Spit 8, Spit 16, or Bf109-K4. If I get that sorted out I'll model and demonstrate.
Tango, XO
412th FS Braunco Mustangs
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I understand your post, and we both agree that mass is the reason the heavier A20 zooms better for the first 1/3 of the zoom-climb, although the advantage as you say is slim, 1/3 of the zoom is significant. like I said, a slight advantage in the first 1/3 of the zoom, due to the extra mass, after which thrust becomes the more important factor.
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Kiss my grits you pompous little .....
:aok
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Excellent post Dtango, nice work <S>.
If there's one take-away at all from this is to put to bed the myth that heavier weight helps zoom.
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I understand your post, and we both agree that mass is the reason the heavier A20 zooms better for the first 1/3 of the zoom-climb, although the advantage as you say is slim, 1/3 of the zoom is significant. like I said, a slight advantage in the first 1/3 of the zoom, due to the extra mass, after which thrust becomes the more important factor.
Actually I quite disagree :). For our example mass gives an advantage 1/5 of the zoom climb. The PS convergence point between the A-20's is less than 5 seconds into the zoom climb. This is the point where the impact of mass being a disadvantage is noticed. After this point the (T-D)/W ratio favors the lighter A-20 and greater mass grows in greater detriment the more into the zoom climb we go.
Tango, XO
412th FS Braunco Mustangs
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indeed the PS convergence is at 5s, but it takes some extra time to negate the previous effect of mass in terms of speed/alt. on the velocity-time graph the heavier A20 has the speed advantage up to about 8s when the lines intersect (about 1/3 of the zoom-climb). on the altitude-time graph the heavier A20 has the alt advantage up to about 14s (about 1/2 the zoom-climb). your posted theory is sound and I concur with the graphed results, so we must agree :)
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There will be differences of course, but look at the plane statistics. The range of power/mass, drag/mass values is not very big and as long as all the planes are underpowered, the differences are reduced even more. It is not like one will zoom twice as high as the other and disappear into the great blue yonder. We are talking about scale of 100ft or slightly more differences.
People expect larger differences that there really were. I recall reading the US tests of the A6M as it compared to several US fighters and the rate at which our fighters pulled away in a dive or zoom climb was not nearly the "1-2 seconds of dive and I am out of gun range" a lot of people seem to think it was.
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indeed the PS convergence is at 5s, but it takes some extra time to negate the previous effect of mass in terms of speed/alt. on the velocity-time graph the heavier A20 has the speed advantage up to about 8s when the lines intersect (about 1/3 of the zoom-climb). on the altitude-time graph the heavier A20 has the alt advantage up to about 14s (about 1/2 the zoom-climb). your posted theory is sound and I concur with the graphed results, so we must agree :)
This is exactly what I mean about the dangers of over-generalization. Looking at the velocity history you can't conclude the impact of mass. The reason the velocity graphs cross at 1/3 is because the increasing thrust of both aircraft play a factor. Thrust just doesn't kick all of a sudden even for the heavier A-20 but it's impact grows at some exponential rate. What you're seeing with velocity history is also the interaction of the thrust of even the heavier A-20 that contributes. The PS curve uncovers what's going on and tells exactly when the effects of mass are negated. The velocity curve doesn't. Nor does the altitude-time history.
So we totally disagree :).
Tango, XO
412th FS Braunco Mustangs
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This is exactly what I mean about the dangers of over-generalization. Looking at the velocity history you can't conclude the impact of mass. The reason the velocity graphs cross at 1/3 is because the increasing thrust of both aircraft play a factor. Thrust just doesn't kick all of a sudden even for the heavier A-20 but it's impact grows at some exponential rate. What you're seeing with velocity history is also the interaction of the thrust of even the heavier A-20 that contributes. The PS curve uncovers what's going on and tells exactly when the effects of mass are negated. The velocity curve doesn't. Nor does the altitude-time history.
This is why you'll never find charts of velocity history in aircraft performance manuals....however; you will find Ps.
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Thank you very much for the clarification, didn't mean to run you thru all the math :D
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Wow. Just wow. dtango you know WAY too much.
Thanks for the post.
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Guys,
I'd like to inject a little science into this discussion. The result may be surprising to some, and will demonstrate the truth of Mace's and dtango's excellent posts, and also explains Humble's contention in the original post that the much heavier A20 can outzoom a much lighter aircraft like the NIK2.
The first thing I hear you asking, is how can Mace, dtango, and humble all be right at the same time, they seem to be saying different things?
Just bear with me, I can show how they can all be right, and to do that I'm going to start with Newtons second law. f = ma. and we must resort to a little math, just to maintain clarity and credibility.
Hope that helps.
Badboy
I think this post proves no misinformation was given by the OP........and it helps clear it up and clarify different methods of retrieving the nearly same outcome.....
another question, if it even has any part of the overall picture ? would be how much does a prop planes ability to generate the most thrust it can muster the slower it gets plays into the scheme of things when talking "Zoom ability"?
btw......I truly enjoyed reading this thread.......
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I think this post proves no misinformation was given by the OP
Not quite, the conclusion regarding the A20s zoom performance was generally good, but the reasoning leading to it was not, as explained earlier in this thread by Mace.
Badboy
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From this day forth let us recognise the creation of a new dweeb.
The Ps dweeb
eg: "Oh yeah, great cherry pick you Ps dweeb. Try fighting me on equal Ps and you will die!"
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another question, if it even has any part of the overall picture ? would be how much does a prop planes ability to generate the most thrust it can muster the slower it gets plays into the scheme of things when talking "Zoom ability"?
TC:
The variation of thrust with velocity is a big reason thrust is a significant factor in zoom climb performance. As you probably know one basic equation for thrust is:
Thrust = Engine BHP * propeller_efficiency / Velocity
Looks simple but there's a lot going on even with this equation. First thrust is a function of airspeed. Thrust INCREASES as airpseed DECREASES.
Second thrust is also a function of propeller efficiency. Propeller efficiency is a non-linear curve. It is a function of propeller and blade geometry and also varies with airspeed. In my basic model I've used a generalized prop efficiency equation. For our purposes propeller efficiency varies directly with airspeed (increases or decreases with increasing or decreasing airpseed).
So how does all this play out in a zoom climb? As speed decreases, thrust overall increases. We can see this in our acceleration component breakdown graph.
(http://thetongsweb.net/images/zoom4.jpg)
The acceleration-due-to-thrust curves (solid lines) are nothing more than thrust divided by mass (thrust/mass) and is representative of the thrust curves. As you can see thrust increases over the time history because in our zoom climb we are decreasing in speed. As we get slower and slower, thrust's contribution grows. Of course it's hard to visualize what this means in terms of aircraft energy by isolating thrust like this. That's where the PS graph comes into play because it gives us a combination view of how thrust, drag, weight, and airspeed interact.
(http://thetongsweb.net/images/zoom5.jpg)
So from my basic model the answer to your question is embedded because we've factored in thrust variation with airspeed and propeller efficiency.
One caveat I should point out here: engine BHP also varies with altitude as well because of variation in air density. Super-charging and turbo-charging play a role in engine BHP output and it's variation with various gearing etc. I assume constant engine BHP in my basic model vs. trying to model engine power output variation with altitude.
Tango, XO
412th FS Braunco Mustangs
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I've got no issues at all with any of my initial statement/comments being corrected. It was in fact invited and is appreciated. What I do find interesting is the feeling that the overall thread and math do validate that within a certain band of parameters the A-20 does enjoy a superiority over most fighters in short sprint type of zooms. Obviously the actual physics and math are beyond my understanding and previous exposure but what I tend to get is that the A-20 in a powered dive to zoom has a window where the combination of mass and thrust act together to create a benefit before the mass begins to counteract the thrust. I tend to use a lot of "pop up" verticals or porpoising to generate climbing rolling scissors and have found the A-20 very effective in that regard. I'm trying to better understand an observed set of events. I know that if I put the a-20 under load in the verticals it wears down quickly. However if I can "cycle" the plane in a largely unloaded state it does a tremendous job of retaining E vs other planes.
What i'm finding is that my evolution of tactics via trial and error matches up pretty well with what I'm reading here....
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you never go angles with an A-20...always suck the E out then pick it apart...
A lesson that Cobia taught me the HARD way ... :D
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Not quite, the conclusion regarding the A20s zoom performance was generally good, but the reasoning leading to it was not, as explained earlier in this thread by Mace.
Badboy
my Bad..... guess I was 1/2 right..thank you for fixing my post, BB <S>
and thanks for your detailed reply, dtango <S>
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I've got no issues at all with any of my initial statement/comments being corrected. It was in fact invited and is appreciated. What I do find interesting is the feeling that the overall thread and math do validate that within a certain band of parameters the A-20 does enjoy a superiority over most fighters in short sprint type of zooms. Obviously the actual physics and math are beyond my understanding and previous exposure but what I tend to get is that the A-20 in a powered dive to zoom has a window where the combination of mass and thrust act together to create a benefit before the mass begins to counteract the thrust. I tend to use a lot of "pop up" verticals or porpoising to generate climbing rolling scissors and have found the A-20 very effective in that regard. I'm trying to better understand an observed set of events. I know that if I put the a-20 under load in the verticals it wears down quickly. However if I can "cycle" the plane in a largely unloaded state it does a tremendous job of retaining E vs other planes.
What i'm finding is that my evolution of tactics via trial and error matches up pretty well with what I'm reading here....
I have read this thread with much interest.
The math proves the increased mass does not help in a zoom.
But in regards to the A20 having a zoom advantage in certain slices of the equation is only fleeting. I think this is all related to the "impression" of energy.
Looking at the whole of it all it is very apparent that there is NO WAY an A20 has ANY advantage over a more nimble fighter. It all comes down to angles.
Although the A20 can create angles based on the aforementioned zoom advantages that is easily neutralized by the lighter and more nimble fighter.
In my opinion the only advantage the A20 vs any fighter is the "greed" factor. If one chooses to go for guns on the A20 at the WRONG time then you will be in guns on the next maneuver.
However, if the fighter recognizes the E state of the A20 it is a very simple matter of maneuvering into the correct angle or just bleeding the A20's energy. Its not like the A20 is going to "exit" any close fight. The A20 isn't going anywhere. He is screwed once the dance begins.
The only pilots falling for the A20 "zoom moves" are ones who don't know much...new players...etc. Now I will admit I was suckered by some A20 moves a few times myself....Cobia is the one I remember shooting my arse down.
As long as the A20 can maintain an excessive energy state it can pull the vertical. But as I said that is only fleeting.
Beware of the fighter who pulls up and exits in the vertical for it is only a matter of two turns before the A20 is caught.
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Good point, Agent.
Would you say that the rare 'masters of the A20' are the one's who best make use of that fleeting advantage before reality sets in? Similar for me in a mosquito, or indeed maybe for you in a 109K4 vs something like a Spitfire MkIX. You will stand a chance defending that fight if and only if you make use of the fleeting advantages that can be forced into the fight. Missing with that 30mm shot can then spell disaster even for the most experienced. At the top of your game, almost every fleeting advantage will be a decisive one. Only a well versed spitfire mkIX flyer will deny those advantages completely.
Not sure if i even have a point here, just thinking outloud. What I think I'm trying to say is that the theory of any combat is a simple and obvious scientific study whereas the actual practice, even simulated, is a much more hit and miss procedure with no real way to predict an outcome before the fight. One of the strongest factors envolved in the actual practical experiement will be who can turn fleeting advantage into decisive.
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Intetresting thread!
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I've always felt cobia does a masterful job of using the drag, not the "zoom". He has a tremendous feel for the nose low turn and the ability to control the wing tip stalls exceptionally low. Basically he'll force the overshoot in a nose low configuration, use the controlled stall to set the nose and the inherent stability of the A-20 to saw you apart at almost any range. You cant ever really get as good a feel for your own style as someone else's but I always feel I fly the A-20 much more as an in/out of plane vs overshoot. I look for ways to gain angles up hill and then recoup E while keeping the angles on the downhill runs.
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Good point, Agent.
Would you say that the rare 'masters of the A20' are the one's who best make use of that fleeting advantage before reality sets in? Similar for me in a mosquito, or indeed maybe for you in a 109K4 vs something like a Spitfire MkIX. You will stand a chance defending that fight if and only if you make use of the fleeting advantages that can be forced into the fight. Missing with that 30mm shot can then spell disaster even for the most experienced. At the top of your game, almost every fleeting advantage will be a decisive one. Only a well versed spitfire mkIX flyer will deny those advantages completely.
Not sure if i even have a point here, just thinking outloud. What I think I'm trying to say is that the theory of any combat is a simple and obvious scientific study whereas the actual practice, even simulated, is a much more hit and miss procedure with no real way to predict an outcome before the fight. One of the strongest factors envolved in the actual practical experiement will be who can turn fleeting advantage into decisive.
What you say here is true. I agree 100% :aok