energy

[df54]

how is energy retention defined and how is it determined, ? also in energy fighting i have big problems bleeding the other guys energy
without bleeding mine i fly a yak 9u almost exclusively.

[Spatula]

Energy is short for any combination of both Potential and kinetic energies. Potential  = stored energy. In the case of aircraft this means altitude.
Kinetic = motional energy. This means the energy it possesses due to its speed.

An aircraft has a finite amount of energy at any given point in time. Some as kinetic, some as potential (unless you're parked on the runway/hangar). One can be traded for the other. Speed will carry you upwards (zoom climb) and you are converting kinetic for potential. Altitude can be traded for speed - eg dive. If you run out of altitude and speed (eg wallowing on the deck) you are all but out of energy - and options.

Energy fighting is a bit of a black-art, and is considered the hardest of the 3 main styles: turn n burn, boom n zoom, energy fighting. The funny thing is we all energy fight to a degree but often without realising it. The real key to proper and deliberate energy fighting is knowing how to judge your own energy levels, and more importantly, how to judge your opponents E level. As most fights tend to be over in the first few maneuvers, its often very difficult to gauge your enemies energy level as you dont always know how much they had to start with. This is where a good level of SA (situational awareness) is critical to predictable energy fights. SA is a difficult thing to learn and takes time. So therefore deliberate and well-executed energy fighting is also difficult and takes time to master. Once you can read enemies E levels accurately, you will stand the best chance of prevailing in E fighting.

The basic premise is to maneuver in such a way as to conserve your energy, while forcing your opponent to waste theirs, and then converting your net accumulated E advantage to a kill, often by performing a maneuver which your opponent will try and fail at and thus put themselves a risk to your counter attack. Its a bit like chess, planning several moves ahead and knowing if your opponent falls into your trap or not and adjust on the fly (excuse the pun). Sounds easier than it really is and like i said it is a real black art.

Its something that is best shown than talked about. Get into the TA with a trainer and i'm sure they can help you out and give you a good grounder on which you can learn on. I run open off-peak training times Monday 5pm US Eastern. Im actually in New Zealand and its my Tues night at 9pm. If that time doesnt suit then try emailing another trainer - http://trainers.hitechcreations.com/

[Mace2004]

Spatula hits the nail on the head.  As far as bleeding the other guy's e you have to do as Spatula says and learn to recognize how much e your opponent actually has.  

There are several ways to do this starting with knowing something about his aircraft.  Spits for instance are very efficient and tend to maintain e well so they can be harder to beat down than some others.  

Take a look at the overall tactical situation when you come across a bad guy.  Did you spot him low in the vicinity of an airfield?  Probably pretty low e.  Did you pick him up in the distance with a few thousand feet of altitude advantage and he then descends below you for the merge?  Probably high e.  

These situations vary quite a bit though if you're fighting a smart guy.  That 190 on the deck may actually be doing 400 mph and can zoom climb to meet your dive head on.  The Pony you spotted in the distance may not actually be going as fast as you think at the merge and instead of zooming up after the merge hits you with a small radius early turn while you arc around at high speed.

As far as beating someone's e down, the biggest mistake I see is that attackers tend to be far to tentative in their attacks.  A B&Z followed by a 4k extension gives the target a lot of time to climb and or regain speed lost in his defensive maneuver.  I've been in many battles with "superior" aircraft where I start out in the hole only to eventually reverse the situation and end up with an altitude advantage because they failed to keep the pressure on.  The worst cast for the target is the guy that gives him no break.  Boom, Zoom for a few seconds and then get right back down on them.  

When it comes to recognizing their e in the middle of the fight take what you know about your turn performance vs his.  Lets say your planes are similar and you keep meeting each other 180 out (nose to nose).  That means both of you have about the same e.  On the other hand lets say you're maintaining your e and he starts to get inside your turn.  He may be gaining angles on you but those angles have to come from somewhere and most likely he's used his best instantaneous turn and bled down some (maybe alot) doing it.  He's thinking "sweet, I'm gaining on him"   Now might be a good time to work more and more in the vertical using your excess e to gain an altitude advantage as he starts to realize he can't get his nose up because he's bled his e for angles.  Look for him to start predominently nose-low turns or to go oblique instead of pure vertical....look for his flaps to come down (the further the better).  Angles, attitude and configuration are probably the best overall indicators of his e.

These are just a few examples and, as Spatula mentions, e is a bit of a "black art".  Do some study (there are several references on the Trainer's page) and meet up with one of us in the TA.

[DoLbY]

I think both gave good answers on this

[Fianna]

Originally posted by df54
how is energy retention defined and how is it determined, ? also in energy fighting i have big problems bleeding the other guys energy
without bleeding mine i fly a yak 9u almost exclusively.

Let me qualify what I'm going to say by first saying that I'm not that familiar with the Yak, but...


The Yak, to me, is a lot like the Ponies. It's great at high speed, but it bleeds E very easily and is at a disadvantage at slow speed. When I fight either one, I try to get them to manuever with me, and if they do, the fight is over. If they stay fast and stick to BnZ/slashing attacks (which is what I believe they are good at), then I have a much smaller chance of killing them.

[Spatula]

Just a quick edit on my last paragraph above (as i cant edit it anymore). My training slot is 5am US Eastern. Not pm as i posted.

[Murdr]

Originally posted by df54
how is energy retention defined and how is it determined, ?

Total drag and excess power are going to be the limiting factors for how well you can retain energy.  As mentioned there are two forms of energy, and likewise there are two forms of drag, parasitic, and induced.  Parasitic drag is the drag inherent in your airframes design when flying straight.  Note that deploying flaps will add to your parasitic drag.  Induced drag is the extra drag caused by maneuvering.

Excess power can be compaired simply by looking at climb rates or acceleration data.  While it has not been tested that I know of, one could quantify relative parasitic drag by timing decelleration from highest speed to top maintainable speed in level flight after a dive.  

Induced drag, while its inherent quanity is also determined by the airframe design, is the factor that is controlled by the pilot.  This is also the factor that is most easy to observe in combat to help judge relative E states.

One other factor that can effectively limit E retention at extreme end of kinetic energy (speed) is compressability, or high speed handling characteristics.  If one plane can maintain full power while the other has to throttle back to maintain controlled flight, then the first plane was able to retain more energy.

While all of these factors can be defined mathmatically, and could be demonstrated with comparitive data, the easiest way to get a handle on the subject is through simple observation.  For instance, in my P-38 I can expect to initally dive away from a co-e spit5, n1k2, or your yak.  Once I continue to extend in level flight, I can expect to leave the spit5 and n1k in the dust because both will bleed off excess E quciker than me.  However, I can expect your yak to slowly equalize speed and start to gain on me because your parasitic drag and excess power characteristics should be slightly better than mine.

Decelleration in level flight after a dive are where E retention characteristics are mosth pronounced, but you can also use a general knowledge of what one can expect in that situation to help determine relative E states in other situations.

Ok, so with all that covered, the answer to you second question is that you need to force the other plane to induce drag (maneuver), and then follow up with another attack before they have a chance to recover much E.  At the same time, you have to manage your separation from the opponent to prevent them from gaining a guns solution before you egress out of range and set up for the next attack (that can be the tricky part aginst an experienced player).  As Mace touched on, a good tactic is to "beat them down" to the deck where diving to gain speed and retian E is no longer an option.

[Widewing]

Energy management is almost an art form. There are many factors involved and knowing your aircraft thoroughly is one of them.

Each aircraft has its own unique drag profile and there's two distinctly different drag profiles to each aircraft; power-off and power-on.

Let's look at these in order.

Power-off drag is almost random because HTC has not modeled propeller drag at idle. I've tested this extensively and found that the aircraft with the lowest drag coefficient (the P-51) has more power-off drag than some radial powered fighters with a much greater drag coefficients.

Thus, you have to develop a feel for overall drag rather than expect it to correlate to real world drag data.

Power-on drag is vastly different, but hard to measure because speed varies considerably from aircraft to aircraft. In this regard, the P-51 bleeds speed very slowly.

Another factor is acceleration. The ability to gain E is a critical factor. If you are flying a fighter that accelerates poorly, E management becomes more important. The P-51's acceleration is only average.

Climb rate is yet another important factor. The ability to gain altitude rapidly means being able to store potential energy rapidly. The P-51's climb rate is only average.

Therefore, the P-51 is a fighter that benefits a great deal by careful E management.

So what is E management? It's a lot of things combined into a basic strategy for combat.

Avoid loading the airframe more than is required, which limits induced drag, and therefore conserves your E. This means don't pull excessive G while maneuvering.

Stay off the rudder pedals. Anything that induces yaw, increases drag. You can use rudder to speed up roll rate, but only do so if you have gained position behind the enemy's 3/9 line.

Don't throw away your altitude carelessly.

Don't use flaps unless absolutely required, and then get them back up as soon as possible.

Avoid throttling back to gain angles... If you don't get the angle, you have burned off precious E for no gain.

Don't follow enemy fighters into a prolonged vertical climb if you are at an E deficit.

E management includes working at equalizing E states with your enemy.

There are exceptions to these rules, such as when you are on the enemy's six and are trying to avoid overshooting (flying past him). However, you will not likely get on their six without good E management prior to that.

My regards,

Widewing

[SkyGnome]

Originally posted by Widewing

Power-off drag is almost random because HTC has not modeled propeller drag at idle. I've tested this extensively and found that the aircraft with the lowest drag coefficient (the P-51) has more power-off drag than some radial powered fighters with a much greater drag coefficients.
 

I find this statement curious.  Idle drag does seem to be implemented - changing  prop RPM at idle clearly reduces drag, as does having an engine stopped fully on auto-feathering planes (P38 for example.)  This makes deadstick landing some heavy, low-drag aircraft a bit of a trick, and makes a P38 with one engine out require significant rudder (or a touch of throttle) to land straight.

Your comparison against "some radial powered fighters" may be affected by said fighters' enormous mass.  Even though they have much higher total drag (the drag coefficient is meaningless without the frontal area), they also have much greater mass.  Measuring power-off drag by measuring the decelleration of the aircraft is really measuring the mass/drag ratio, not just drag.  So a lightweight aircraft with low drag may decellerate the same as a heavy aircraft with higher drag.  And so despite its greatly higher drag, a P47 may decellerate much slower than a P51 - as at any given speed, its great weight allows it to carry much greater kinetic energy which it can spend overcoming its greater drag.

[Lusche]

Originally posted by SkyGnome
Your comparison against "some radial powered fighters" may be affected by said fighters' enormous mass.  

I think Widewing may have had the La-7 in mind, which has much less mass than a P51, yet seems to hold E at least as well as a Pony (if not even better) with power off.

[SkyGnome]

Ok, at 2k alt, a coast from 300 to 200mph indicated:

LA@7390lbs
Throttle off                   21:32
Throttle off & min rpm  37:59

P51@8981lbs
Throttle off                    19:31
Throttle off & min rpm   38:09

So with min rpm, the mustang does retain speed a bit better.  I'm not really sure why one would presume that the difference between a radial engine and an inline would neccessarilly be the determining factor between two aircraft's drag profile.  The La is lighter, but also has smaller wings, no guns sticking out of the wings, etc.  And the P51's fancy radiator is going to be pure drag when it's not belching out heat, too.  Without some hard data on the specifics of their drag profiles, I think it's a bit much to say that prop drag is not modeled or random.  It is clearly modeled, and the relationship between these two aircraft at least is within the realm of reason, and demonstrates that other factors (like prop behavior) have a huge influence on the results of testing like this.

EDIT:
Just for fun, here's a P47:
P47@14951lbs
Throttle off                     28:28
Throttle off & min rpm    43:75

Makes sense to me.  All that time and energy spent accellerating that mass has no problem muscling against the prop for an equally long time - and without so much prop to muscle, just pulling the beast through the air is a cakewalk for that ocean of accumulated energy.

Yak9u@7050lbs
Throttle off                     15:31
Throttle off & min rpm    32:15

A little stranger here, but in line with its lower speed than a P51, even given similar horsepower and the Yak's smaller wings.  Poor coeficient of drag for the poor yak, it would seem.

[Widewing]

Originally posted by SkyGnome
Ok, at 2k alt, a coast from 300 to 200mph indicated:

LA@7390lbs
Throttle off                   21:32
Throttle off & min rpm  37:59

P51@8981lbs
Throttle off                    19:31
Throttle off & min rpm   38:09

So with min rpm, the mustang does retain speed a bit better.  I'm not really sure why one would presume that the difference between a radial engine and an inline would neccessarilly be the determining factor between two aircraft's drag profile.  The La is lighter, but also has smaller wings, no guns sticking out of the wings, etc.  And the P51's fancy radiator is going to be pure drag when it's not belching out heat, too.  Without some hard data on the specifics of their drag profiles, I think it's a bit much to say that prop drag is not modeled or random.  It is clearly modeled, and the relationship between these two aircraft at least is within the realm of reason, and demonstrates that other factors (like prop behavior) have a huge influence on the results of testing like this.

HiTech previously stated that max RPM prop drag is not modeled.....

Power-off testing is not done with prop pitch set at min RPM. It's tested with the prop pitch at max RPM. No one pulls back pitch in combat.

Nonetheless, there is some information to be garnered by testing at minimum RPM as I will show you later. You need a larger population to make any determinations.

As to drag, the CDo of the La-7 is greater than that of the P-51D. As best as I can determine, the CDo of the La-7 is .0233 as opposed to the Mustang's well known figure of .0176.  

Physics disagrees with in game test data as well. We have a lower drag aircraft of greater mass bleeding speed faster than the higher drag, lighter fighter... Should not happen.

Here's some test data for to chew on, using the same speeds as you did, and at 3,000 feet ASL. Time to bleed speed from 300 mph TAS to 200 mph TAS.

Type / Power off max RPM / Power off min RPM

P-51D: 19.75 sec / 38.84 sec
La-7: 20.62 sec / 34.18 sec
P-40E: 16.03 sec / 24.90 sec
F4U-1A: 24.09 sec / 41.34 sec
Yak-9U: 14.16 sec / 31.28 sec
109K-4: 18.47 sec / 32.63 sec
Tempest: 16.19 sec / 27.35 sec

Note that there is no rhyme or reason to the numbers. The split between the min and max RPM on the P-51 is 19 seconds. On the P-40E it's less than 9 seconds. The Tempest's split is 11 seconds, with the Yak at 17 seconds. The Tempest has one of the greatest speed bleeds at max RPM, and still poor at min RPM. Yet, it has a CDo less than the P-40 and weighs as much as the F4U-1A. Low drag, lots of mass... Should be much better than it is.

Like I said, prop drag is not modeled, at least not in a way that makes the least amount of sense.

My regards,

Widewing

[SkyGnome]

Originally posted by Widewing

Like I said, prop drag is not modeled, at least not in a way that makes the least amount of sense.
 

Prop drag is modeled, or rpm changes wouldn't affect the speeds.  Your problem is with how that model jives with your perception of what you should see.

The reason that you find so little correlation to the difference when using min rpm, is that min rpm varies with the aircraft.  Some have wide rpm ranges, others smaller.  This affects the drag generated by the prop hugely, but without some pretty hardcore data, it isn't going to be predictable.  The Temp goes from 1800-3800RPM, the P51 1100-2900, so the pony's RPM reduction ability is 53% vs. 62% for the Temp.  You'd also need to know the closed-throttle pumping losses of the engine in question at that rpm.

Another illustration of this is that the P38, with its fancy feathering props, takes 35:06 to decellerate 300-200 at min RPM and closed manifold, but a whopping 50:44 with the engines off and the props stopped.  (Be careful measuring this, that you start fast enough to let the engines fully stop before 300mph.)  Min RPM drag is not min drag for a given prop, just for that particular engine, prop, and rpm setting.

And prop drag is exactly why the Tempest doesn't coast well at idle.  Its HUGE frickin' prop (now windmill) attached to a massive engine (now air compressor) gives it the ability to burn energy (speed) in whopping dollops through its propeller.  That same prop that can efficiently transform well over 2000hp into thrust can do the same in reverse.  Bigger windmill, bigger air pump, more power lost.

And you are still treating drag coefficients as total drag.  They are drag per unit area.  The LA7 has less of those units of area than the P51.  Its total drag is less.  It's total drag per unit mass is very similar (including propellor losses), thus the similar decelleration performances.  The reason that coeficients are used when talking about drag is so that you can compare aircraft of dissimilar size.  For this discussion however, we need to focus on total drag.  Total drag per unit mass, including propeller losses.

An example...

The question:
You have two planes, of exactly equal weight, with the same engine and propellor.  One has a Cd0 of .01, the other .05.  Which will decellerate faster with throttle closed?

The answer:
You can't tell from the information given.  You must know the drag area to tell.  The worse drag aircraft could be very small, but ineficiently designed.

And finally, the way we're measuring here isn't measuring zero lift drag - the number you're throwing around.  Flying level induces considerable drag.  I also doubt that zero-lift drag numbers include the prop, or it would be a useless measure from an engineering perspective and be an ill reflection on the airframe design.

I'm glad I spent the time on this, as it was amusing.  All the data that I see points at a pretty respectably modeled system, at least to the limits of our measurement capabilities and certainly the limits of combat relevance.

[Widewing]

Originally posted by SkyGnome
Prop drag is modeled, or rpm changes wouldn't affect the speeds.  Your problem is with how that model jives with your perception of what you should see.

The reason that you find so little correlation to the difference when using min rpm, is that min rpm varies with the aircraft.  Some have wide rpm ranges, others smaller.  This affects the drag generated by the prop hugely, but without some pretty hardcore data, it isn't going to be predictable.  The Temp goes from 1800-3800RPM, the P51 1100-2900, so the pony's RPM reduction ability is 53% vs. 62% for the Temp.  You'd also need to know the closed-throttle pumping losses of the engine in question at that rpm.

Another illustration of this is that the P38, with its fancy feathering props, takes 35:06 to decellerate 300-200 at min RPM and closed manifold, but a whopping 50:44 with the engines off and the props stopped.  (Be careful measuring this, that you start fast enough to let the engines fully stop before 300mph.)  Min RPM drag is not min drag for a given prop, just for that particular engine, prop, and rpm setting.

And prop drag is exactly why the Tempest doesn't coast well at idle.  Its HUGE frickin' prop (now windmill) attached to a massive engine (now air compressor) gives it the ability to burn energy (speed) in whopping dollops through its propeller.  That same prop that can efficiently transform well over 2000hp into thrust can do the same in reverse.  Bigger windmill, bigger air pump, more power lost.

And you are still treating drag coefficients as total drag.  They are drag per unit area.  The LA7 has less of those units of area than the P51.  Its total drag is less.  It's total drag per unit mass is very similar (including propellor losses), thus the similar decelleration performances.  The reason that coeficients are used when talking about drag is so that you can compare aircraft of dissimilar size.  For this discussion however, we need to focus on total drag.  Total drag per unit mass, including propeller losses.

An example...

The question:
You have two planes, of exactly equal weight, with the same engine and propellor.  One has a Cd0 of .01, the other .05.  Which will decellerate faster with throttle closed?

The answer:
You can't tell from the information given.  You must know the drag area to tell.  The worse drag aircraft could be very small, but ineficiently designed.

And finally, the way we're measuring here isn't measuring zero lift drag - the number you're throwing around.  Flying level induces considerable drag.  I also doubt that zero-lift drag numbers include the prop, or it would be a useless measure from an engineering perspective and be an ill reflection on the airframe design.

I'm glad I spent the time on this, as it was amusing.  All the data that I see points at a pretty respectably modeled system, at least to the limits of our measurement capabilities and certainly the limits of combat relevance.

So, you are saying that HTC has modeled "closed-throttle pumping losses of the engine"? I don't think so...

Using your approach, the F4U-4 should be among the worst. Huge prop, huge engine, large flat plate area, relatively high CDo.... Yet, it's just about the best at speed bleed.... How do you explain that?

Also, the flat plate area of the P-51D is 4.10 sq/ft, with the La-7 coming in at 4.89 sq/ft. So, the P-51 is heavier, a lower Cdo and less flat plate area... Yet it bleeds speed faster anyway... Moreover, the P-51B, with a lower CDo than the P-51D (same flat plate area) bleeds speed faster than the D model. Why is that? Another mystery?

And yes, I am using zero lift drag figures... That's what CDo represents. CDo = CD − CDi where CD is total drag coefficient for a given power, speed, and altitude minus lift induced drag. CDo for the P-51B is 0.169. Lift induced drag is accounted for.

I'll repeat again that HiTech has stated that they have not modeled prop drag. Modeling means that they made a best effort to determine what it is and plug it into the code. What they probably did was plug in an arbitrary number that they figured was adequate. What you see when you change pitch is the difference between that arbitrary number and the resulting change. I doubt if HTC has any idea what the prop drag is for any individual fighter.

Unfortunately, your argument does not explain the speed bleed characteristics in Aces High.

My regards,

Widewing

[SkyGnome]

Originally posted by Widewing
So, you are saying that HTC has modeled "closed-throttle pumping losses of the engine"? I don't think so...

As a general concept, absolutely.  The thing that makes a prop spinning at higher RPM slow an aircraft down more than a prop spinning at low RPM is closed throttle pumping losses (and some friction.)  This is very clearly modeled.  It is probably not calculated per piston or anything.... or even necessarilly different for various aircraft.

Using your approach, the F4U-4 should be among the worst. Huge prop, huge engine, large flat plate area, relatively high CDo.... Yet, it's just about the best at speed bleed.... How do you explain that?

The F4U-4 is outrageously heavy, much more so heavy than it has large flat plate area and high Cd0, I think.  I have no numbers to back this up.  Perhaps you can point me to your sources...  The F4U-4 is still a pretty slow-accellerating aircraft relative to late-war monsters, evidence of a modest power/weight ratio (indicating the decelerating effect of the prop will be modest relative to its weight.)

Also, the flat plate area of the P-51D is 4.10 sq/ft, with the La-7 coming in at 4.89 sq/ft. So, the P-51 is heavier, a lower Cdo and less flat plate area... Yet it bleeds speed faster anyway... Moreover, the P-51B, with a lower CDo than the P-51D (same flat plate area) bleeds speed faster than the D model. Why is that? Another mystery?

For the La, if what you are providing as measures for flat plate area are the same as what HTC is using for their drag model, then it would seem that something may be off.  (Oh, and once you start talking flat plate area, the relative Cd0s are no longer really relevant, as that's part of flate plate area.)  But if those flat plate areas are what HTC is modelling, the LA should be a bunch slower, I think.  What's your source for that LA number.. I'm really curious, as hard russian numbers seem as hen's teeth.  (And I don't mean the XXX girls... those are easy to find..)

As to the P51s, they are quite close, B: 20.97, D:21.12 in my measure (at2k).  And I'd say my margin of error is ~1/2 sec (so by my measure, you could call it either way.)  They are darn close, the B might be a hair slipperier, but it's lighter by ~90lbs.  What exactly is the difference in Cd0 between B and D?  They have slightly different engine setups, too.  Regardless, they are very much the same airframe, and very much the same in performance.

And yes, I am using zero lift drag figures... That's what CDo represents. CDo = CD − CDi where CD is total drag coefficient for a given power, speed, and altitude minus lift induced drag. CDo for the P-51B is 0.169. Lift induced drag is accounted for.

Um.. You just said that Cd0 is "... minus lift induced drag".  What we are measuring by flying the planes level _includes_ lift induced drag, and thus won't follow Cd0 exactly.  And what we can measure includes the prop, which these numbers should not, I don't think.

I'll repeat again that HiTech has stated that they have not modeled prop drag. Modeling means that they made a best effort to determine what it is and plug it into the code. What they probably did was plug in an arbitrary number that they figured was adequate. What you see when you change pitch is the difference between that arbitrary number and the resulting change. I doubt if HTC has any idea what the prop drag is for any individual fighter.

I'd need to see the statement by Hitech to understand the meaning of that.  You first said, "HiTech previously stated that max RPM prop drag is not modeled.....", which could mean that drag induced by the prop at max RPM in a dive (beyond the max level speed), when the prop would otherwise be holding the airplane back (and over-reving the engine) is not modeled.  This would not be relevant in what we're currently measuring, and while being really interesting, would be very hard to measure.

But to say that prop drag is not modeled is absurd considering the overwhelming evidence to the contrary.  Perhaps it is one really huge bug that makes our planes slow down quicker when the props are spinning?

Unfortunately, your argument does not explain the speed bleed characteristics in Aces High.

Ehh.. perhaps not, but it's pretty close.  I don't think your numbers support the La's speed, either, so perhaps it's a matter of different numbers instead of different concepts.  The La is only inexplicable given your flat plate number.