Author Topic: A fundemental view on Weight and E state and its role in ACM  (Read 7433 times)

Offline humble

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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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Offline moot

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #1 on: June 08, 2009, 09:40:26 AM »
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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Offline humble

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #2 on: June 08, 2009, 09:46:14 AM »
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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Offline moot

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #3 on: June 08, 2009, 09:56:58 AM »
It wasn't totally clear, thanks Humble.
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Offline humble

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #4 on: June 08, 2009, 10:07:20 AM »
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   

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Offline moot

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #5 on: June 08, 2009, 10:30:10 AM »
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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Offline humble

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #6 on: June 08, 2009, 10:53:19 AM »
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

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Offline morfiend

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #7 on: June 08, 2009, 04:08:12 PM »
Great stuff Snap :aok


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Offline humble

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #8 on: June 08, 2009, 04:26:48 PM »
 :)

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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Offline mechanic

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #9 on: June 08, 2009, 04:28:15 PM »
 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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Offline humble

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #10 on: June 08, 2009, 04:42:31 PM »
I know I cant catch a buff that drops and then zooms....you end up hanging behind the tail gun.

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Offline mechanic

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #11 on: June 08, 2009, 04:50:27 PM »
But starting equally both at 350 TAS the A20 will far out zoom the b17?

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Offline Wedge1126

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #12 on: June 08, 2009, 05:18:09 PM »
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.
« Last Edit: June 08, 2009, 05:24:26 PM by Wedge1126 »
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Offline mechanic

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #13 on: June 08, 2009, 05:33:36 PM »
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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Offline morfiend

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Re: A fundemental view on Weight and E state and its role in ACM
« Reply #14 on: June 08, 2009, 05:40:42 PM »
:)

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