Energy Maneuverability Theory

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FutureFlyer06

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Unread post03 Dec 2004, 01:43

Hi everyone. I'm currently a high school in sophomore and I am looking to write a report as extra credit for my physics class since I might need it to make an A for the semester. In the summer I began to read <a href="aviation_books_book3117.html">Boyd: The Fighter Pilot Who Changed the Art of War</a> by Robert Coram.

It was very interesting, but I never got the chance to finish the book before the school year began. Once it did, factors such as academics and athletics did not grant me the time to finish reading it. I read just a little bit about his "Energy Maneuverability Theory" which I have often heard as changing the art of air combat.

The thing is I really don't know what this "theory" is about. I know it has something to do with thermodynamics so I think it could be applicable to my report. I would really appreciate it if anyone with a knowledge of aerodynamics could explain this theory to me and why it is so pivotal to air combat or if anyone could provide me with links that do explain it thoroughly.

Your help would be greatly appreciated. Thank You.
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Dammerung

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Unread post03 Dec 2004, 01:48

Code: Select all
Ps = [u][T-D][/u]V
               W
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habu2

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Unread post03 Dec 2004, 05:57

Can't write the report for ya, best go read that book all the way through.
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Gums

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Unread post03 Dec 2004, 18:55

Salute, young man!

First, thermo is prolly your first semester or two for the aero degree. All kindsa stuff about entropy, gas laws, etc. Only then do you get to lift, drag, motors, stability, etc.

Second, STBYGAIN and Cylon can explain the energy doofer better than most of us as they use it all the time. I'll give it a try.

Basically, Boyd figured out that in the new jets with swept wings that the old turn and burn stuff didn't work. The new planes could turn like hell - ONCE! Thren they were wounded ducks. The drag increased dramatically during hard turns compared with the previous generation like Mustangs, Zeros, FW-190's, etc. Those planes would stall before the energy bled off too much. The swept wings would 'mush' before you lost complete control.

So one of the the secrets was to use the energy you had and trade any excess energy for altitude, then cash it in when coming back down. If you started the fight low on E, then you had to get some..... duhhhhh? Hence we see the famous egg-shaped flight pattern. Zoom up and then as you lose speed and energy, you can have a tighter turn radius. Plus, you can use God's gee if you are pulling down inverted. At the bottom of the egg, you are scooting along and can't turn as tightly.

Boyd and others figured out that we could quantify the areas of the envelope that provided a jet with the best energy level versus turn radius, then exploit that knowledge. So we came up with the Rotowski climb that maintained energy as we climbed. We came up with better definitions of corner velocity and quickest-tightest turn. We learned not to pull too hard unless it was the absolute final maneuver in the end game. We learned to maintain energy by making giant barrel rolls to maintain the six o'clock position versus just pointing the nose. All those things and more were what allowed Boyd to make his standard bet with the less-experienced dweebs.

The result of the 'fighter mafia' was the addition of the Eagle, Tomcat, Hornet and Viper to the inventory. Plenty of engine power to gain or maintain energy, low wing-loading to help maintain E in a hard turn, use of the leading edge extensions on the wing to help keep the air going where it should be going, leading edge flaps, strakes and other doofers to keep the pointy end forward, etc. Other things helped, as well. Visibility was dramatically increased versus the F-4 and other jets. The armament systems were light years ahead of the planes we flew in the 60's.

There must be some neat books someplace you can read about aero, and Boyd's ilk. Hit the liberry one mo' time and search the net.

later,
Gums
Viper pilot '79
"God in your guts, good men at your back, wings that stay on - and Tally Ho!"
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avon1944

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Unread post04 Dec 2004, 02:05

FutureFlyer06 wrote:I have often heard as changing the art of air combat. The thing is I really don't know what this "theory" is about.

John Boyd was the first person who looked at aerial maneuvers from an engineering/"mathematical modelling" stand point. If an aircraft has a drag coefficient of "X", T/W of "Y", entry airspeed, G-load and, a lot of other knowns (or given) for a particular situation/maneuver -say the Emmelman, it can be calculated what the altitude & airspeed, for which the aircraft entered the maneuver..... what the exit speed, altitude and, G-load for the duration of the maneuver. A set of math equations can be set up for any aircraft in any situation.

Now, this allows a pilot attacking another pilot to know the options available to the pilot on the defensive. Knowing what options he has, you can be prepared to counter his first move as he first starts the maneuver. This will go on for each move you make you will know his best and second best counter move. After several maneuvers the pilot on the defensive sees everything he does is of no usage. That you appear to be inside his head or "OODA Loop."

Now, in designing an aircraft such as the F-16, using the theory of energy maneuvering means designing an aircraft that takes advantage of power to help in the maneuvering of the aircraft. The F-14 & F/A-18 maneuver well due to their low drag and areodynamics. The F-15 & F-16 maneuver well due to their high thrust to weight (T/W). This allows high T/W fighters to power through verticle maneuvers as well as maneuvers in the horizontal plane. Aircraft that have lower T/W and depend on low drag are good in the horizontal but have more problems in the verticle plane.

There are more exact and more elaborate explainations but, I think this gives you the essence of what Col. John Boyd was trying to do. Col. Boyd's was not recieve well by the USAF even though they now use it, his brash behavior had a lot to do with that. Strangely the service that found usage for one of his next theories "Maneuver Warfare" was the USMC!
When he died only two USAF officers showed up at his funeral. There were over a dozen USMC officers that showed up!

Adrian
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allenperos

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Unread post12 Aug 2005, 18:51

Dammerung - Nice equation, Ps=Energy State?, u=Fc? W=mass? This equation I need. Could you quailitively explain in essay, although I know, for everyone else's sake? It is going to make a nice addition to my notes on Aeronautics. Thanks, no hard feelings about previous issues, ok?

Gums - Nice explanation on energy depletion/conservation. I appreciate it. So, I hear you have flown the VooDoo. Can you explain your experiences in this jet, sir?
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LWF

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Unread post13 Aug 2005, 00:38

The E-M theory basically means that energy is required to maneuver. The equation is used to quantify how much potential energy is available to maneuver with. When you go into a hard turn, you use energy, and it takes time to regain that energy to maneuver with, and in that time maneuver is more or less impossible. Some planes lose energy quicker or regain it quicker. Hence the phrase 'turn and burn'
It takes a fighter with a gun to kill a MiG-21!
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allenperos

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Unread post13 Aug 2005, 01:59

Of course. Wrong term, not maneuver, you mean performance. There was a thread by Roscoe about maneuvering!!! It is not applicable in ACM, has a totally different meaning.
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LWF

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Unread post16 Aug 2005, 02:51

So maneuverability has nothing to do with Air Combat Maneuvering? I'm confused.
And the full equation is P sub S =Thrust - Drag / Weight * Velocity.
It takes a fighter with a gun to kill a MiG-21!
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allenperos

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Unread post23 Aug 2005, 07:27

It is expressed in the wrong context, it should state, peformance, rather than the colloquial "maneuvering" definition which means quality, ease, ability to withstand stress, imposed by performance. The equation, which is written is more than likely correct, haven't read the book, feel it's a big propaganda bomb. It sounds like performance to me.
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Roscoe

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Unread post23 Aug 2005, 14:01

Roscoe

"It's time to get medieval, I'm goin' in for guns" - Dos Gringos
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allenperos

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Unread post24 Aug 2005, 04:12

Thank you Roscoe, read the article, sounds like quite a guy, very respectful of him now that I am familiar. Reminds me alittle of Chuck Yeager.
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F16VIPER

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Unread post24 Aug 2005, 04:26

I read the Mind of War and Boyd non stop and life will never be the same again.It was the biggest eye openner you could possibly imagine.
It allows me to understand issues better and not to be so naive.
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Dammerung

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Unread post24 Aug 2005, 04:31

Indeed, Awesome books!
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Roscoe

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Unread post24 Aug 2005, 18:22

IMHO, Mind of War was over the top in it's hero-worship of Boyd, perhaps because Boyd was available to be interviewed for that book, and he had a way of aweing his audience.

When Boyd was written, JB had already passed so the author was able to remain more objective and less awe-struck. As a result I found the latter to be a more enjoyable read.

But as was said, both were eye-openers.

I would also suggest reading The Pentagon Wars by Col Jim Burton. ( http://www.amazon.com/exec/obidos/ASIN/ ... 89-8132803 )

It was used as the basis for an HBO black comedy, but the book is anything but a comedy. The author was a member of Boyd's inner circle and paid a deep personal and professional price for that, which is discussed in the book. Unfortunately, the book reflects a great deal of bitterness and as a result is very biased. That said, if you can get past that it's an amazing read. One guy (Burton) created a job that evolved into a congressionaly mandated Live Fire test office within the Operational Test Directorate within OSD.
Roscoe

"It's time to get medieval, I'm goin' in for guns" - Dos Gringos
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