Yak3 speed

[Vinkman]

The speed in the MA of the YAK3 seems higher than it should be. Too often at equal speeds, when chasing a YAK3 in a 109K-4 on WEP I will start to close only to find the YAK3 starts to pull away. The chart below shows that according to the Aces High Plane performance page there is no altitude where the YAK3 is faster than K4. In fact the closest speed is on the deck where the K4 is 15mph faster and by 5K that difference is 30mph, increasing to 40 mph by 10k.   I've chased YAKS for a whole sector on the deck and am never able to close on them.  This is also inconsistent with all the accounts from Galland, and Rall's memoirs who recount that the only Russian plane they could not overtake was the late war Lavochkins. 

Doing the math: With a lead of 1500 yrds it should only take 3.4min to run down a YAK3 at full speed, which is 19 miles, or less that 1 sector.

Does this indicate the speed of the Yak in the MA is faster than it should be? 


https://www.hitechcreations.com/component/ahplaneperf/?Itemid=139

[Wildin]

You may have misread chart, it appears to show Yak faster below about 7000 ft unless you have a lot of wep left in your 109K.

[Badboy]

Does this indicate the speed of the Yak in the MA is faster than it should be? 

Hi Vinkman

No it doesn't mean that, there are other factors that may be influencing what you see in the MA.

Before I explain what those factors are though, I'd just like to say that I believe those charts are generated from the AH flight model so the charts should always agree exactly with what you see in the game. However, the speeds can easily be checked with simple flight tests. The K4 sea level top speeds are 368mph and 338mph for WEP and MIL respectively, the top top speed of the Yak3 at sea level is 351mph. I've confirmed it myself. If you want me to explain how to carry out the flight test so you can verify those figures yourself let me know.

Ok, so why are you seeing something different in the MA? As I mentioned, there are other factors that have a big influence on what speeds you will see in the MA, and it comes down to the aircraft's performance relating to energy. Where the Yak3 stands out in the MA is in its ability to accelerate quickly and both retain and regain energy due to specific excess power and specific excess thrust. The Yak3 isn't really faster, but it just seems to be because those factors have a big indirect impact on what speeds can be achieved and retained and for how long.

What does that mean? Well we have all seen it for ourselves, so I'll explain with a scenario that everyone will recognize.

The Yak3 gets itself into trouble at altitude and dives away for separation. Because it accelerates quickly it can reach its top speed before you can reach yours and it gets enough separation to stay safe and continue to extend. However, the Yak3 doesn't just reach its top speed, it exceeds it and has to trade less energy for that speed than you will. Here is the catch, because it accelerates quickly and bleeds its energy slowly it gains a larger speed margin above top speed than you do and pays for it with less energy/altitude than you did. Of course no aircraft can stay above top speed indefinitely so when that speed begins to decay back towards top speed it does so more slowly than you. That means it stays above its top speed longer. Also if maneuvering is required while extending, the Yak3 dissipates less energy doing so. That's a powerful factor in a tail chase.

Then the Yak3 can climb again and regain energy and it will also regain that energy more quickly than you can, on top of having having already lost less than you did when you followed him through the same evolution. If necessary the Yak3 can reverse and have sufficient energy to reengage, get himself into trouble again and rinse and repeat the process. Brief fights followed by protracted extensions is what gets the Yak3 their bad name. It's why we all hate it so much

The Yak3 is able to turn hard holding energy well and then break off and accelerate quickly enough to get out of trouble. It is not that its faster, but it gets to its top speed faster, exceeds it by more than you can, then holds onto it longer than you can, and eventually regains more of it more quickly than you can.

It isn't really about speed, but it certainly seems like it.

It seems as though the Yak3 is faster, but its not... As I said before, everything feels like its all about speed but its really about energy and the way the Yak3 retains energy and regains energy. It can trade energy for speed, hold onto it longer and trade back again more quickly than you and with fewer losses, it has high energy agility.

It makes the Yak3 only seem to be faster and it makes the Yak3 pilot only seem to be good.

Hope that help.

Badboy

[Vinkman]

You may have misread chart, it appears to show Yak faster below about 7000 ft unless you have a lot of wep left in your 109K.

I didn’t misread it. I used the wep numbers.

[Vinkman]

No it doesn't mean that, there are other factors that may be influencing what you see in the MA.

Badboy

I understand the factors. 

The K4 in game has a combat weight of 7500lbs and a HP of 1824 (1850PS) = Power/Weight ratio of .243
The Yak3 in game has a combat weight of 5900 lbs and a HP or 1290. = Power/Weight ratio of .218

So there is no reason for a Yak3 to out accelerate a K4. In fact the opposite should be true. The K4 has a P/W ration 11% higher than the yak3. These numbers also indicate the Yak must be a lower drag plane at top speed. But That difference can't over come the K4's power advantage (40%). The K4 would out accelerate and be faster than the Yak3 at every altitude, with higher alts being a bigger advantage for the 109 because it's engine retains more of it's max HP rating. Eliminating the scenarios where E states are different because that's obvious, and focusing on situations when the two planes are on or near the deck at equal speeds, a Yak3 shouldn't be able to walk away from the K4 or run one down. 

We should do some tests with two planes at the same time. 

[trogdor]

I have a film of a yak3 on the deck doing a steady 375mph for 15miles......with half of one wing blown off.
To be clear, this is faster than the top speed of an undamaged yak3's top speed at sea level.
Again, this was a sustained level speed, not a decaying speed attained from a dive.
To those out there who aren't already aware, large asymmetrical damage to an aircraft dramatically increases both the form drag and induced drag. Losing parts does not reduce drag.
I'll see if i can find that film and post it.

[Vinkman]

I have a film of a yak3 on the deck doing a steady 375mph for 15miles......with half of one wing blown off.
To be clear, this is faster than the top speed of an undamaged yak3's top speed at sea level.
Again, this was a sustained level speed, not a decaying speed attained from a dive.
To those out there who aren't already aware, large asymmetrical damage to an aircraft dramatically increases both the form drag and induced drag. Losing parts does not reduce drag.
I'll see if i can find that film and post it.

You mention asymmetric and induced drag. I also feel these may be overly low for YAK3 which “seems” to retain much more of its speed while maneuvering than it’s power to weight would imply.  That’s a much harder thing to measure. But you think overtaking one in a straight line is tough, it’s nearly impossible one they start jinking and making slight changes in direction. 

Trog. if you have time maybe we can go to one of the arenas and make some films with both planes during a set of maneuvers that would test the theory to help Dale out.

hit me up on 200 or send me an email and we can pick a date and time.

[Badboy]

The K4 in game has a combat weight of 7500lbs and a HP of 1824 (1850PS) = Power/Weight ratio of .243
The Yak3 in game has a combat weight of 5900 lbs and a HP or 1290. = Power/Weight ratio of .218

If only it were that simple. However, acceleration is not a function of the power to weight ratio. Remember Newton's law, it is a function of excess thrust to weight. The  catch is that while the power and weight of an aircraft stay pretty much constant during a level acceleration, the thrust varies with airspeed. Also, to get excess thrust (acceleration depends on net thrust) you need to take drag into account and that will also vary with the speed and weight. Because total drag is involved, acceleration not only changes as the speed changes it depends on the G loading, so pushing over for speed and pulling out and/or making heading adjustments can result in wide variations in load factor and lift dependent drag. So there isn't a constant excess thrust to weight ratio number you can easily use for comparison.

So there is no reason for a Yak3 to out accelerate a K4. In fact the opposite should be true. The K4 has a P/W ration 11% higher than the yak3.

I can think of four reasons.

But before I list them, I just want to say that the K4 does out accelerate the Yak3 in a side by side drag test... but not always. Give the Yak3 25% fuel and the K4 100% and the situation is reversed. In the MA it is normal for one or more of the following factors to be in play to some extent.

1) Loadout: In a level 150mph to 200mph drag test the Yak3 can out accelerate the K4 just by changing the fuel loads.
2) Initial altitude: One aircraft starting higher or lower than the other. God's G can be a big acceleration bonus.
3) Initial airspeed: One aircraft starting faster or slower than the other.
4) Differences in position or heading, one aircraft needs to maneuver, execute a turn, or dive for example.

Expanding on the fourth point, if you are chasing a Yak3 and are forced to follow its maneuvers it costs it less energy due to it's lower lift related drag and that translates straight back to more speed. That's how they wear you down. You notice how the Yak3 pilots can break off extend and come back to reengage and still have enough energy to do it all again until they bleed your energy away bit by bit.

Obviously, I have no idea if any of those reasons were a factor in your example, but my experience is that when something surprises me in the MA it is almost always a factor I was unaware of at the time. Some pilots are good at hiding their initial energy state, and we can only guess about the fuel loading etc. It's very rare for any fight in the MA to begin Co-E and I think that may be the main cause of most of the things that surprise us

Eliminating the scenarios where E states are different because that's obvious, and focusing on situations when the two planes are on or near the deck at equal speeds, a Yak3 shouldn't be able to walk away from the K4 or run one down.

I agree, the top speed of the K4 should eventually prevail, but when conditions favor the Yak3 perhaps it just takes a lot longer than expected

We should do some tests with two planes at the same time.

That's a good idea. I'm up for it anytime you see me online. 

Regards

Badboy

[Badboy]

Hi Trogdor

To those out there who aren't already aware, large asymmetrical damage to an aircraft dramatically increases both the form drag and induced drag. Losing parts does not reduce drag.

Agreed, that's how it works in real life but I think I recall a previous discussion on these boards where the consensus reached was that when you lose a part of your aircraft in AH you lose the weight, lift, drag etc associated with that part, but no new drag is added to account for changes caused by that damage. Obviously you may need to use other surfaces more to stay in the air, but it does appear to be that when you lose part of your aircraft, depending on the aircraft, the part and what you need to do to stay in the air, it may be possible to experience a small net reduction in drag. I think I've survived a tail chase or two that way myself.

Kind regards

Badboy

[Vinkman]

If only it were that simple. However, acceleration is not a function of the power to weight ratio.
...the thrust varies with airspeed.

Equally for both air craft at equal speeds. so that is a non factor.

...you need to take drag into account and that will also vary with the ... weight.

Yes that's why I mentioned it. But total drag as a percent is less than the HP offset.

... if you are chasing a Yak3 and are forced to follow its maneuvers it costs it less energy due to it's lower lift related drag..

Need to understand how the induced drag varies with weight. That might make it a weight squared problem.  Never studied Aero.

I agree, the top speed of the K4 should eventually prevail, but when conditions favor the Yak3 perhaps it just takes a lot longer than expected

That's a good idea. I'm up for it anytime you see me online. 

Regards

Badboy

Ok I'll keep an eye out. 

[save]

That must have been from direct hit from a battleship main gun.
Yak3 wings are more sturdy than the front armor of a Tiger II

I have a film of a yak3 on the deck doing a steady 375mph for 15miles......with half of one wing blown off.
To be clear, this is faster than the top speed of an undamaged yak3's top speed at sea level.
Again, this was a sustained level speed, not a decaying speed attained from a dive.
To those out there who aren't already aware, large asymmetrical damage to an aircraft dramatically increases both the form drag and induced drag. Losing parts does not reduce drag.
I'll see if i can find that film and post it.

[Badboy]

Equally for both air craft at equal speeds. so that is a non factor.

It varies in a similar way, but is far from equal for both aircraft. I think the Me109s used the Hamilton Standard prop design, not sure about the Yak3, I'd have to check, but even if they are the same prop design, how well it absorbs the engines power and converts it into thrust at any specific airspeed will be quite different and varies with its diameter, the number of blades, the activity factor, the rpm and pitch control etc. The fact that the K4 is different in that respect can be seen by the way it can pull its nose up and hangs on its prop at very low airspeed. It does it so much better than so many other aircraft it is almost unbeatable in a rolling scissors, even against aircraft that would beat it easily in a turn. That excess thrust at low speed is the K4s super power, it is clearly not equal to other aircraft at equal speeds    

Need to understand how the induced drag varies with weight.

A heavier aircraft requires more lift. More lift causes more lift induced drag. That's a relatively small factor in a 1G tail chase, but still significant even with the K4s powerful engine because with 100% fuel it can still be out accelerated from 150mph to 250mph by a lighter Yak3 with a much less powerful engine. It is (T-D)/W not P/W that matters. It is even more of a factor if maneuvers occur during a chase because as the load factor increases the lighter aircraft will bleed energy and speed less quickly than a heavier one even if they are otherwise identical, say two 109K4s one with 100% fuel and one with 25%. The light K4 will not only turn better it will accelerate better and may be able to extend from or catch the heavier one. In air combat any additional weight is a curse.

Ok I'll keep an eye out.

Yep, if I see you on, I'll give you a shout. I'm looking forward to it 

Kind regards

Badboy

[Vinkman]

It varies in a similar way, but is far from equal for both aircraft. I think the Me109s used the Hamilton Standard prop design, not sure about the Yak3, I'd have to check, but even if they are the same prop design, how well it absorbs the engines power and converts it into thrust at any specific airspeed will be quite different and varies with its diameter, the number of blades, the activity factor, the rpm and pitch control etc.
Badboy

I know how it could be different. But I'm guess that the Germans didn't make inferior props, and mis-match them to engines and airframes. So I don't expect the 109 prop to have significantly lower prop efficiency than a Yak. In game with auto prop control both planes walk the max efficiency line so I don't expect it would be a big factor in the performance differences between the planes.

I know that weight affects the induced drag. What I don't have is a mathematical understanding, precisely. If a plane weighs 27% more, what percent higher is it's induced drag? Then, what percent of the 40% Thrust advantage is consumed to overcome the increased drag. Because that thrust difference still needs to accelerate a 27% heavier plane.   

I'll do some reading. 

[TyFoo]

With regard to Total drag whether Induced or Parasitic, Wing Planform design is important and explains a couple of the issues being discussed  - more specifically Straight Wing vs the Elliptical Wing planform. One is way more efficient than the other.

[Slade]

Gents,

I LOVE the Yak-3.  It should be perked though.

Yep you can compare this against that ad nauseam. BF-109's at one part of the war were directed NOT to engage it.

I'll engage it. I'll fly it. It should be perked.


Thank you,

X15