Author Topic: Vy vs Best Energy Airspeed  (Read 7869 times)

Offline hitech

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Vy vs Best Energy Airspeed
« Reply #30 on: December 16, 2004, 02:56:23 PM »
HoHun: Isn't close to constant thrust cool.

HiTech

Offline Badboy

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Vy vs Best Energy Airspeed
« Reply #31 on: December 16, 2004, 03:18:06 PM »
Quote
Originally posted by HoHun
Hi Badboy,

After re-reading Shaw, I'd say the speed of best energy transfer is only relevant for supersonic jets that have a superior climb ability above Mach 1 than below in parts of their envelope. Wow! :-)

Regards,

Henning (HoHun)

I can see how you could get that impression if you only read Shaw, and he actually says about subsonic aircraft, that only slightly faster speeds result. However, the theory works, and the equations posted earlier are equally applicable, regardless of the aircraft’s top speed. It just becomes more important as the speed range increases. There are other sources from 1944 onwards that apply the techniques to high performance prop fighters, and it is relatively easy to develop the details of the theory, apply it to curves generated for WWII fighters and confirm it for  yourself. If you need more mathematical or aerodynamic detail, check this source: http://aerade.cranfield.ac.uk/subject-listing/esdu/ES161.html most of those documents are available in their entirety from any good university library, providing they have an aeronautics department. However, these documents, have been written in the context of modern jet aircraft, but the methods are easily adapted. Good luck with that :)

Badboy
« Last Edit: December 16, 2004, 03:29:16 PM by Badboy »
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Offline Shaw

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Vy vs Best Energy Airspeed
« Reply #32 on: December 16, 2004, 04:22:44 PM »
Muerto et al,

Sounds like to me most of you are in violent agreement on this topic.  Let me try to clear it up...since apparently I started it.  ;)

The best speed for "long-term" energy addition is Vy, best climb rate speed, best energy-addition rate speed...whatever you want to call it...it's the same thing.  I think one thing that's confusing some folks is that Vy is not a single number, but varies with altitude for a given aircraft (also weight, configuration, etc.).  The dotted line from points B to C in Badboy's Ps chart is actually Vy for this aircraft.

So if you want to gain total energy as fast as possible over a long period of time (we're not talking seconds here, necessarily), get to Vy as quickly as possible (dive if you're slower, zoom if you're faster), then climb at Vy until it becomes more important to do something else (rather than gain energy), like shooting somebody.

Hope this helps rather than making things worse.

cheers,

Robert Shaw (Mouse)...no, you haven't seen me online  

Offline MOSQ

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Vy vs Best Energy Airspeed
« Reply #33 on: December 16, 2004, 04:34:20 PM »
For those of us non-pilots who haven't a clue what 98% of this thread is all about, I found this webpage to be very helpful!
 

http://www.av8n.com/how/htm/energy.html#sec-energy-strategy

Offline Badboy

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« Reply #34 on: December 16, 2004, 05:03:49 PM »
Quote
Originally posted by Shaw
Hope this helps rather than making things worse.


Welcome to the boards!  

Make yourself at home, the beer is free here :)

Badboy
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Offline Badboy

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Vy vs Best Energy Airspeed
« Reply #35 on: December 16, 2004, 05:06:08 PM »
Quote
Originally posted by MOSQ
For those of us non-pilots who haven't a clue what 98% of this thread is all about, I found this webpage to be very helpful!
 


Hi MOSQ,

Link doesn't work for me.

Badboy

Edit (Ahh it's John Denker's "See How It Flies" perhaps he's moved it?)
« Last Edit: December 16, 2004, 05:24:53 PM by Badboy »
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Offline JG14_Josf

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Vy vs Best Energy Airspeed
« Reply #36 on: December 16, 2004, 05:47:51 PM »
The Author of the Bible?

Rejoice!

I wish to take this opportunity to express my gratitude for such a valuable resource of information and entertainment.

"Fighter Combat" is awesome.

Thank you very much for a fine literary work, Robert L. Shaw.

I have found the sustained turn technique to be especially useful and enlightening.

Is it possible that you are inclined to converse on the finer points of Air Combat? Will you entertain a few questions?

Joe

Offline muerto

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« Reply #37 on: December 16, 2004, 05:51:23 PM »
Quote
Sounds like to me most of you are in violent agreement on this topic. Let me try to clear it up...since apparently I started it.


Thank you for the clarification; nothing like getting it direct from the source.

Loved the book!

Offline Badboy

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« Reply #38 on: December 16, 2004, 05:59:09 PM »
Quote
Originally posted by Shaw

Hope this helps rather than making things worse.



Just to round it off with an example then, suppose you want to get from some speed and altitude at point A, and enter an engagement at a higher speed, say your corner velocity, at a higher altitude, say point D in this diagram.



And you want to do it as quickly as possible…You would dive to point B, climb to point C gaining speed on the way, then dive again to point D.

The initial dive, followed by a climb in which you gain speed, followed by a diving entry into the fight, is what I’ve been describing all along.

Hope that helps…

Badboy
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Offline MOSQ

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Vy vs Best Energy Airspeed
« Reply #39 on: December 16, 2004, 06:28:52 PM »
Hmmm, it works when I click it, try: http://www.av8n.com

Offline Badboy

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« Reply #40 on: December 16, 2004, 07:06:24 PM »
Quote
Originally posted by JG14_Josf


I have found the sustained turn technique to be especially useful and enlightening.

Joe


Be careful though Joe, the best sustained turns are very different things in Jet and Propeller driven aircraft. In a Jet the maximum sustained turn rate is generally well above the stall speed, and often closer to the corner velocity, while on a prop’ the best sustained turn occurs on the edge of the stall. This diagram shows why…      



You can see here, the reason is the shape of the Ps = 0 curve is very different between Jets and propeller driven aircraft. Even the mighty F-16 that can sustain 9g, has a Ps = 0 curve that drops dramatically below corner speed, while most prop’ fighters have a zero Ps curve that rises all the way to the stall. If you fly a jet at its best sustained turn rate, you need to stay above the stall, often close to corner velocity, when you want to get the best sustained turn out of a prop’ fighter, you fly it right on the edge of the stall.

Hope that helps…

Badboy
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Offline JG14_Josf

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Vy vs Best Energy Airspeed
« Reply #41 on: December 16, 2004, 09:51:02 PM »
Badboy,

I'm not sure where you are going with the Jet vs Prop comparison but the sustained turn technique described in "Fighter Combat" serves me quite well in WWII combat simulation.



The reason why the sustained turn technique works so well has to do with preying on other player’s weaknesses, particularly their overconfidence. When fighting against opponents with an obvious turn advantage the tendency is for them to go for the angles and burn up their energy.
The sustained turn technique is excellent for developing a sense for relative energy states too.
Also the sustained turn technique is a staple in team tactics allowing the dragging plane to set up his wingman for a good shot without too much risk.

After a successful application of the sustained turn technique the relative energy gains may not be enough to afford a reverse yet have plenty of room to invite the target in for a chase. Being well out of range the game is really on, if the victim takes a bite.

Some times my energy margin is enough to afford plenty of room to pitch back on top of the target but the set-up is so well done it is more fun to just watch the target hang there as my wingman picks him off like a fish in a barrel.

What really interests me about this technique concerns relative energy modeling in the games. Just how much energy loss is accurate during high g turns relative to less aggressive turning?
Which planes were better at unloaded acceleration and are these planes being modeled correctly?

The other game has moved from a condition of relative modeling where acceleration was a generic factor. During those days the energy fight was relatively non-existent. The game was hit and run for those planes that were modeled with inferior turn performance and that was about it. What surprised me was that the sustained turn technique did work then if the other pilot really took the bait and pulled on the stick. Then it was a real trick however to end up with enough energy to zoom and pitch back. Now things are much different, even the P-47s are sticking around to fight it out.

I don’t really know how accurate all this is, but my guess is that if the tactics worked in the real world and they work in the simulation then things are pretty close.

So the question is: How did things work in the real world?

Well...?

I can read "Fighter Combat"
or
Boyd, Galland, Buchner, Stienhoff, Brown, Lipfert, Knoke, etc.

Which book will give me the best picture of how Air Combat was conducted in real life during WWII?

How about this one:

“Actual combat accounts of the successful use of energy tactics are rather rare, but the following example is a beauty. Here John Godfrey's P-51B Mustang has probably 20 percent lower wing loading than the German Focke-Wulf 190D-9 opponent, and Godfrey increases his turn advantage further by skillful use of flaps. The Focke-Wulf, however, may have 20 percent better power loading. Here are two masters at work.

“A plane was approaching, and because of its long nose I thought it was a Mustang. Turning into it I received a shock; it was neither a Mustang nor an ME-109, but a new Focke-Wulf; its long nose was the latest improvement of the famed FW. These planes with the longer noses were rumored to have more horsepower than their predecessors, and were capable of giving a Mustang a rough time. We met practically head-on and both of us banked our planes in preparation for a dogfight.
Around and around we went. Sometimes the FW got in close, and other times, when I'd drop my flap to tighten my turn, I was in a position to fire - but the German, sensing my superior position, kept swinging down in his turn, gaining speed and quickly pulling up, and with the advantage in height he would then pour down on my tail. Time was in his favor, he could fight that way for an hour and still have enough fuel to land anywhere below him. I still had 400 miles of enemy territory to fly over before I could land. Something had to be done. Throwing caution to the wind I lifted a flap, dove and pulled up in a steep turn, at the same time dropping a little flap. The G was terrific, but it worked, and I had the Jerry nailed for sure. Pressing the tit I waited, but nothing happened, not a damned thing. My guns weren't firing."
"By taking this last gamble I had lost altitude but had been able to bring my guns to bear while flying below the FW. With his advantage of height he came down, pulled up sharp, and was smack-dab on my tail again. The 20mm. cannons belched and I could see what looked like golf balls streaming by me. A little less deflection and those seemingly harmless golf balls would have exploded instantly upon contact with my plane. "Never turn your back on an enemy" was a byword with us, but I had no choice. Turning the plane over on its back I yanked the stick to my gut. My throttle was wide open and I left it there as I dove. The needle stopped at 600 miles per-that was as far as it could go on the dial. Pulling out I expected at any minute to have the wings rip off, the plane was bucking so much. The last part of my pull-up brought me up into clouds. I was thankful to have evaded the long-nose FW. for that pilot was undoubtedly the best that I had ever met." (Fighter Combat, Robert Shaw)

Note how the tactics are explained with specific examples.

Where are you going to find this type of instruction, this type of historical documentation made relative to specific tactics and maneuvering for WWII fighter planes no less!?

It doesn’t stop there in “Fighter Combat”.

How about the Split, Half Split, Sandwich, Brackett?

What about the Bogie Cloud? No that sounds familiar in WWII combat simulation.

OK, enough with the sales pitch. I am a fan. I am curious too.

Joe

Offline Crumpp

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Vy vs Best Energy Airspeed
« Reply #42 on: December 16, 2004, 10:06:07 PM »
Quote
Here John Godfrey's P-51B Mustang has probably 20 percent lower wing loading than the German Focke-Wulf 190D-9 opponent, and Godfrey increases his turn advantage further by skillful use of flaps. The Focke-Wulf, however, may have 20 percent better power loading. Here are two masters at work.


Pretty sure that was NOT a Dora.  None were inservice at the time and it is very unlikely Godfrey ran into a prototype from Rechlin on a test flight.  Allied intelligence knew about the Dora and had been hyping it up for about a year before it was deployed.

Most likely he just ran into a skilled pilot in an FW-190A.

Crumpp
« Last Edit: December 16, 2004, 10:09:14 PM by Crumpp »

Offline JG14_Josf

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Vy vs Best Energy Airspeed
« Reply #43 on: December 17, 2004, 08:28:54 AM »
Crumpp,

Unless more information is identified concerning that particular historical account then my question is: who is going to be the best one to guess which planes were involved?

My money is on the guy who actual saw the enemy plane and who actually flew the plane involved in the fight, the same guy who probably has better vision than 90 percent of the population.

That however is a minor point when compared to the message found within the text.

Here is where I am beginning to find a problem with your messages. Do you have anything to say?

Chances are that I will eagerly buy your book. I am currently able to afford investments in literature. Here is a real gem: “The Gulag Archipelago” by Aleksander Solzhenitsyn.

Now there is a guy with a message.

If the subject matter that one wishes to digest concerns a more specific realm of human activity then there is my all time favorite ‘airplane’ book: “Boyd” by Robert Coram.

If you don’t find “Boyd” to be entertaining, insightful, and inspiring then perhaps there is little value for you in literature, perhaps it is just my awkward sense of value.

The message in “Fighter Combat” is specific. The questions answered are specific:
”How to” fight air combat. Which specific performance attributes lend themselves toward specific tactics and specific maneuvers?

X percentage of Y performance advantage can be applied like so…

The message is valuable to some because the information, the instruction, and the knowledge works in simulated air combat. If you read the bacl cover of “Fighter Combat”, if anyone is to believe the words coming out of the mouths of WWII fighter pilots (I know this is not a popular opinion among the players of games i.e. Who is so stupid as to believe pilot anecdotes. What a joke!) then the message found in “Fighter Combat” is useful in real life too.

The message, if found, is a common understanding of stuff. How can one put this into words? I guess that is the problem isn’t it?

Communication is finding what is common between the one telling the message and the one listening to the message.

Note: two things have to occur; the one telling must tell and then another one must listen.

What an incredible task! No only does one have to form a message in a way that can be heard but another one has to open their minds and allow the message to enter. I guess ignorance is a virtuous sort of thing.

If you get a chance to read about Solzhenitsyn’s Gulag then perhaps you will understand my outburst here and forgive me some. I do hope to find a message within your upcoming book. I wish only to communicate and my abilites are lacking. I have these damn chips on my shoulders and it is not easy to ignore them.

Joe

Offline Crumpp

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Vy vs Best Energy Airspeed
« Reply #44 on: December 17, 2004, 08:41:24 AM »
Jesof,

Fighter pilots make ID mistakes all the time.  It's a fact of life.

When did Godfrey's unit give up it's P51B's?

When did the FW-190D9 enter service with the Luftwaffe?

What is more likely?  The Luftwaffe had a lone FW-190D9 in service that happenend to encounter Godfrey's P51B or that he misidentified the aircraft?

Quote
That however is a minor point when compared to the message found within the text.


Exactly.  Was I supposed to explain that?

Sorry!!

Crumpp