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Thoughts on the K-4 Manouverability


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I am aware that the 109 charts are largely extrapolation and may be wrong in parts, but they are based off measurements. It actually does not matter which one - but the calculations must be done in TAS or you get complete nonsense like your previous post. 

 

Whatever ASI velocity measurements people take in testing to derive Cl (or vice versa), or what you put on the scale of a graph, the velocity in the lift equations is TAS. That is why you have to have a PEC and specify a height.

 

"If you compute the 2g stall speed at the conditions provided in the chart with the corrected CAS converted to TAS, 161 mph. The CL max comes to ~1.4. Which shows good agreement with the earlier stall tests in the report, Table 4."

 

It only comes to 1.42 if you insist, wrongly, on reading the intersection of stall boundary and 2g line as 160mph TAS, when it is right on the vertical scale line for 150mph. There is even a nice round point - it is nowhere near 160 mph. The stall test report in Table 4 is at 1g, power off (probably low enough not to worry about CAS/TAS conversion): why would it show good agreement with a 2g stall, power on, at 12,000ft? 

 

At 150mph it comes to ~1.62, close enough to the assumed number. 

 

The chart is assuming Clmax of 1.95 at 1g power on - so we can solve for V, which is 43.2 m/s TAS, = 97 mph, at 12,000ft = 81 mph CAS : which is all pretty close to the chart position.

 

If you think the charts are wrong, please show us the corrected versions.

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3 hours ago, Yak_Panther said:

sqrt of .7 = .8

 

It's 0.83. It puts the minimum radius turns at 154 mph TAS for the Bf109 and at 160 mph TAS for the Spitfire. Both points agree as well with the charts as resolution permits.

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1 hour ago, unreasonable said:

I am aware that the 109 charts are largely extrapolation and may be empirically wrong in parts, but they are based off a measured 1g power off stall Cl max

 

 

Fig 17 is not based on table 4. It's Kludged from table 6.

 

1 hour ago, unreasonable said:

There is even a nice round point - it is nowhere near 160 mph.

The point is at 150mph because, they took ASI in chart 6, 118 mph:

image.png.707ac07fcbe7ae2fa19ae5951f9b2be9.png

, and using the equation at the bottom of the chart.

image.png.449a3e0a7fdbc90521cf5970fc88f899.png

 

converted it to TAS 147:

image.png.8854de1429853ce3b744231701690ccc.png

 

Then, based on weight and wing area computed the Cl Max at  2g, 1.6

 

image.png.30bebf31dcdd03037f4a042ffef86449.png

The Rest of the CL's were computed by taking the approximate Delta in Cl due G  of Spit and applying it to 109. Which is how you get a 109 with a 1g Cl max of 1.95

image.png.11bd7be91cd9db76418f260e08f4b120.png

The only flight test conducted to devise these charts were a 2 g min turn radius turn. The author used the ASI and converted it to TAS. They didn't even bother to apply PEC corrections for the 109's Static probe.

1 hour ago, unreasonable said:

It only comes to 1.42 if you insist, wrongly, on reading the intersection of stall boundary and 2g line as 160mph TAS,

To get to 1.42. We use the CAS from the trailing edge probe in figure 6., 129mph. Then convert to TAS ~ 161 and derive a Cl max of ~ 1.4.

image.png.483892b908b6284ea858a6c73a2d08c4.png

1 hour ago, unreasonable said:

why would it show good agreement with a 2g stall, power on, at 12,000ft? 

Per table 6. They took the 109 and flew a minimum radius turn at 2g. Minimum radius occurs at the lowest airspeed.

Radius min = Stall Speed Vs^2/ g

To fly a minimum radius turn, the power setting would have to be low. Therefor thrust effects are negligible.  Which is why it would have good agreement with 1 g Cl max at engine idle. 

 

 

 

Edited by Yak_Panther
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34 minutes ago, Yak_Panther said:

To fly a minimum radius turn, the power setting would have to be low.

 

You're 24 days late for such a statement...

 

A minimum radius turn (sustained, as it is) requires as much power as possible. It occurs at the highest air speed the aircraft can maintain without loss of altitude while riding the stall. In the diagrams it's the point where angle-of-straight-climb line and stall line intersect.

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26 minutes ago, JtD said:

 

You're 24 days late for such a statement...

 

A minimum radius turn (sustained, as it is) requires as much power as possible. It occurs at the highest air speed the aircraft can maintain without loss of altitude while riding the stall. In the diagrams it's the point where angle-of-straight-climb line and stall line intersect.

Max rate sustained is power limited. Min radius sustained is load factor limited.

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But then not even the charts you've posted agree with that. Just read the radius from the charts as stated.

 

An unsustained turn, both in terms of minimum radius and maximum turn rate, is limited by the permissible load factor of the air frame. In the diagrams it would be the point where the (roundabout) 10g line and the stall line intersect (in this case muddied by the reduced cl at higher speeds). It's just not on them.

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Does the aircraft have excess power in the 2 G min sustained rate speed?, yes other wise this would be the corner speed.  Would Going slower or faster cause the radius to shrink? What is limiting factor of low speed flight?

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2 hours ago, JtD said:

 

It's 0.83. It puts the minimum radius turns at 154 mph TAS for the Bf109 and at 160 mph TAS for the Spitfire. Both points agree as well with the charts as resolution permits.

 

Especially when you take into account that the 109 turn numbers are at 2.1g not 2.0g - you are getting exactly the intersection of climb line and stall boundary with a fractionally lower CL than the 150/2.0g mark: all completely consistent.  

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13 minutes ago, Yak_Panther said:

Does the aircraft have excess power in the 2 G min sustained rate speed?, yes other wise this would be the corner speed.  Would Going slower or faster cause the radius to shrink? What is limiting factor of low speed flight?

 

A 2g turn would be sustained at a speed of about 275 mph TAS with a radius in excess of 3000 feet.

 

A stall turn at a lift coefficient of 1.60 at 2g would not be sustained, because the aircraft would be climbing with about 1m/s (a bit less than 1° times TAS) according to the chart. It would have excess power. There is no information on a sustained stall turn at 2g in the chart, it is a 1200hp/2400rpm power chart (see top right corner), where excess/lack of power is a result and expressed in climb/descent angle. It is not a sustained turn chart, where required power is the result. They may be similar, but once you modify the cl boundry by power based propwash, they are not the same.

 

The best sustained turn is about 2.1g, 155mph TAS, 885feet radius, 25 seconds, as seen both in the chart and listed in table 6. It's faster and slightly tighter than a climbing turn at 2g.

 

For those who are interested and do not have access to the report, again the chart for the 109 plus a description about how to read it. Just follow the instructions for point P.

 

image.thumb.png.ec22cd38ebcd727893d467d4b828ce0d.png

image.png.d3487705ab954a5d684d79a8432f9196.png

 

They are also available here:

 

http://www.spitfireperformance.com/spit109turn.gif

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2 hours ago, Yak_Panther said:

 

image.png.483892b908b6284ea858a6c73a2d08c4.png

Per table 6. They took the 109 and flew a minimum radius turn at 2g. Minimum radius occurs at the lowest airspeed.

Radius min = Stall Speed Vs^2/ g

To fly a minimum radius turn, the power setting would have to be low. Therefor thrust effects are negligible.  Which is why it would have good agreement with 1 g Cl max at engine idle. 

 

 

Table 6 says "Both aircraft at full throttle" right there in the title.

 

And then I am moving on.... 

 

 

 

 

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58 minutes ago, unreasonable said:

 

Table 6 says "Both aircraft at full throttle" right there in the title.

 

And then I am moving on.... 

 

 

 

 

 

That's not the minum turn radius at 2 g. That was a Test of the 2 g sustained turn at 12k feet.  If you wanted to test the minimum radius, you would pull 2 g and reduce the throttle until you could you could no longer fly at 2g. 

1 hour ago, unreasonable said:

 

 

 climb line and stall boundary

 

I showed how those were computed.

Gates gives the Stall Boundary line as: n (load factor) = N

Where N is  (V/Vs)^2

At the 2g where the TAS is 150mph the equation looks like this.

2= (150/Vs)^2

All they did was Solve Vs

as Vs = 75 * Sqrt2

Vs = 106.07 TAS.

Then the went and plotted the radius and the rest of points according.

for 4g it looks likes this

4 = (X/106.07)^2

Therefor 4= 212.14TAS

And where does the 4g stall boundary fall on the chart?

image.thumb.png.a5f499b6f3bf1364ee96a056b70efaaf.png

The problem is your assuming some of the points on that chart are from flight test. The only data point used to compute that chart was the ASI during the 2 g turn. All the other gates equations are derived from that data point. 

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1 hour ago, JtD said:

There is no information on a sustained stall turn at 2g in the chart,

Any turn made below the zero angle of straight climb line, is sustained. Turns above the line require the craft lose alt. See gates paper or the notes at the bottom of the test.

 

image.thumb.jpeg.dceb3e252f2794f64fcf1a044e2dbef5.jpeg

Guess where the 2 g point is?

 

image.png

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Gates uses a constant clmax in his equations, while the charts presented use different clmax with different g's, which are the ones stated on the charts. Your calculated 212 are in fact 220, which would be easier to see if you had drawn your line parallel to the grid. This is a result of the lower lift coefficient of 1.49 at 4g instead of 1.60 at 2g, which were used for the calculations.

The clmaxes listed are assumptions and are based on a flight measured power off maximum lift coefficient for both aircraft and, in case of the Spitfire, on a flight measured power on maximum lift coefficient. In case of the Bf109, power on maximum lift coefficients were estimated based on the Spitfire results. It's stated that clearly in the report.

 

There's no 2g measured clmax for the Bf109.

 

Table 6 gives the minimum radius turns based on the calculations these charts. The sustainable performance is also being presented in a simpler chart in figure 18, http://www.spitfireperformance.com/spit109turn18.gif.

 

Gaining altitude is not a sustained turn, it is a climbing turn. In a sustained turn nothing changes. Not altitude, not speed, not g load, not bank angle, not turn rate, not turn time, not thrust.  Nothing.

 

 

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On 4/25/2021 at 3:11 AM, JtD said:

Gaining altitude is not a sustained turn, it is a climbing turn. In a sustained turn nothing changes. Not altitude, not speed, not g load, not bank angle, not turn rate, not turn time, not thrust.  Nothing.

The definition of a sustained turn is; a turn that does not require the energy state of the aircraft to change for the given turn rate / load factor to be maintained indefinitely. The energy state being defined by the speed, and altitude of the aircraft, Pe, ke. If the aircraft has to descend to maintain a given turn rate / load factor, Then that turn is not sustainable. If the aircraft is capable of climbing during a given turn, That indicates, that the aircraft has excess power and is capable of sustaining that turn.

 

In Gates's chart, turns at load factors and airspeed below the "angle of straight climb" line are by definition sustainable. 

image.thumb.png.0650fa1adeeb2094439aca3830d6247d.png

 

The speed for the sustained minimum turn radius at 2g, occurs at the lift limit, not the power limit.  ~ 150 TAS

The minimum radius of a turn, occurs at the stalling speed for the given load factor of that turn.

 2 g turns from the stall limit, 150 TAS,  are sustainable until ~275 TAS. As the 2g line is below the "angle of straight climb".

The chart quantifies the amount of excess thrust in terms of climb angle.

At 200 mph TAS the chart shows a 2g turn can be sustained with a climb angle of ~4 degrees.

image.thumb.png.1558bd0f2c87e89db0f0d2993e66ea11.png

 

 

The line of "angle of straight climb" is a derivative of the  drag equation. From Gates:

The drag coeffiecent is Cd0 +kCl^2

Angle of straight climb (0) = (1/Pi*A + k) * n^2 -1/ N * Cl Max  

Which is why 2 g turns above 275 are thrust limited.  Given the thrust and drag at that load factor, to accelerate you would have to dive.

 

The sustained turn chart, Fig 18., is just another way of plotting the "angle of straight climb" line.

 

Fig 18's uses the same Cl's as Fig 17. for the Turns at stall line. Which are lift limited.

image.thumb.png.538e1a992f9feeccef52b7b1cc07ae5e.png

 

 

The chart can also be put in terms of excess thrust.

image.thumb.png.81d1f606cf54cd3afd0a7ec1ea416c5e.png

The max sustained load factor is ~ 2.4g

 

 

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There's a difference between sustainable and sustained. You'd be right that all turns below the line are sustainable, if clmax did not change with power. Like I said previously, this is a maximum power turn chart. You reduce power, clmax goes down, and the stall line moves right. Therefore, the only point on the stall line that truly is a sustained turn, is with the intersection of the angle of straight climb line, at 2.1g, 155mph TAS.

 

Anyway, while I think it was good you brought the chart up, as the discussion should be on the 109 and we were deep in P-51 country, I also think that clarifying details of the charts is getting us off topic again.

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4 hours ago, ZachariasX said:

image.thumb.png.1558bd0f2c87e89db0f0d2993e66ea11.png.3a1642f1df986e8a4ae64c728d7a8a6b.png

 

Running the numbers on this example from Fig.7 posted above, I get a Clmax of ~1.35 for the Bf-109.

Using a weight of 5600 lbs*3, a wing area of 174 ft^2, a density = 12k ft, .84 kg/m^3, at 192 mph, I get a Cl of 1.494. 

 

What variables are you using? 

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8 hours ago, Yak_Panther said:

Using a weight of 5600 lbs*3, a wing area of 174 ft^2, a density = 12k ft, .84 kg/m^3, at 192 mph, I get a Cl of 1.494. 

 

What variables are you using? 

Too high of an air density obviously, I just scaled down mass to .9 to compensate for 25% drop in air pressure. Thanks for your numbers! Looking at some tables „out there“, it seems your .84 are the sensible choice for standard atmosphere and a Clmax then of about 1.5 does makes more sense.

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On 4/27/2021 at 6:45 AM, LColony_Red_Comet said:

 

The K-4 in DCS just absolutely blows away he P-51 in terms of sustained turn rate. Its so much more maneuverable than the K4 in il2.

 

Not really very objective of you to take an incident from an online match. For all you know he could've been fighting without MW50 (some DCS WW2 servers don't allow MW50 for the 109), or maybe he was still new to the aircraft or propjobs in general. Were you using flaps? Was he using flaps? Too many outside factors to tell wether that was a fair match up or not.

 

If you want to know the actual difference, I suggest you create a mission, give both aircraft 400 L of fuel (means a full 109), and then try your luck in a sustained turning contest against an experienced 109 pilot in DCS. You will lose, I guarantee it. 

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2 hours ago, Panthera said:

 

Not really very objective of you to take an incident from an online match. For all you know he could've been fighting without MW50 (some DCS WW2 servers don't allow MW50 for the 109), or maybe he was still new to the aircraft or propjobs in general. Were you using flaps? Was he using flaps? Too many outside factors to tell wether that was a fair match up or not.

 

If you want to know the actual difference, I suggest you create a mission, give both aircraft 400 L of fuel (means a full 109), and then try your luck in a sustained turning contest against an experienced 109 pilot in DCS. You will lose, I guarantee it. 

Thanks for making my point for me will simultaneously letting it fly over your head.

 

Obviously...there are numerous factors in a actual game that matter. That is the entire point of this video. The 109K4 in DCS out turns the P-51. It also out turns the P-51 in Il2. Any turn performance advantage that is greater than about 1-1.5 seconds cannot really be made up for except if we introduce some extremely unlikely and absurd offsets that wont occur very frequently. Put another way, I would not be able to do this if the performance were not close. If the 109 was really 1 billion percent better in DCS you like it is, I would be losing even to inexperienced pilots 9 times out of 10.  I can do what I just did in this video to most 109 pilots in either of these games. I couldnt pull this off in a P-47 or a 190D. And I certainly could not do it vs a spitfire, even if I showed up with 10 percent fuel. The other person would have to be a very unlikely level of bad. Additionally I chose this video because he starts in the control position and I still managed to beat him in a two circle at sea level. You can see that he makes the same mistake that allows myself and others to win this fight in a 51 vs 109 all the time, he pulls too much and the torque gets the better of him, which is why he is nose high the entire time. This happens to 109s in il2 turn fights more the half of the time. The 109 is simply hard to max perform, and this is what leads to the impression that it is worse, even when people are trying to test in ideal conditions.

 

As for experienced pilots, I practice dog fighting all the time with a few people who are of very close skill level to my self. That isnt a claim that were the best, simply that we are similar. We all know enough to max perform either of these planes in il2 or DCS. Our 109 vs 51 fights with exactly even fuel loads almost always result in drawn out turn contests if it ends up devolving into a sea level two circle rate fight. It generally takes a very long time for the 109 to come around, and its close enough that even with similar pilots the 51 can win if the 109 makes some small errors. This is either game.

 

Multiple people aside from myself have confirms several times now that the planes perform about the same in both games. Some people even went to great lengths making fancy doghouse plots. This entire thread is about a problem that doesn't really exist in DCS or Il2. Yet you keep posting your supposedly accurate turn tests where you tests the planes at a randomly selected speed that has nothing to do with the actually max sustained rate speed of either plane. Picking the same speed and measuring the G at that speed is meaningless. Above the best sustained corner speed for either plane, as you can see from comparing various doghouses for various planes including these ones, a plane with the better sustained rate at best speed may not have the advantage a higher speed or the advantage may be so small that its hard to measure. Im not going to bother converting the numbers again, but you picked a speed thats something like 220mph for both planes. Both planes hit their best sustained turn below 180mph.

 

Quite frankly this is all much ado about nothing.

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Sorry but in IL2 the K4 will not outturn the P-51 sustained like it should, whilst in DCS it will do it with apparent ease. Already posted the tested load factors to illustrate this, and I've made double sure they're accurate, so I'm not in doubt:

 

IL2 @ 370 km/h sea level:

P-51D, 400 L, 67" Hg: 3.4 G's sustained

109K-4, 400 L, 1.8ata: 3.3 G's sustained

109G14, 400 L, 1.8ata: 3.3 G's sustained

 

DCS @ 370 km/h sea level:

P-51D, 400 L, 67" Hg: 3.0-3.1 G's sustained 

109K-4, 400 L, 1.8ata: 3.6-3.7 G's sustained

 

Also in both sims there's an auto rudder feature you can enable to rule out that as a factor during testing.

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2 hours ago, Panthera said:

in IL2 the K4 will not outturn the P-51 sustained like it should

 

Actually, it does. If I am flying both of them, using your aircraft setup, I get the K-4 to outturn the P-51 no problem at sea level. No flaps used.

 

Turn time as flown (right hand turns), tech specs as given by the devs. Other figures calculated using physics. The only thing the P-51 is better at in game is being aerodynamically more clean - which it is.

 

Aircraft Time Speed Weight Wing span Wing area Power Turn radius Load factor CL Induced drag Thrust Efficiency
P-51D15 19,8 260 4134 11,29 22,30 1650 228 2,5 1,45 8302 16792 49%
Bf109K4 19,1 270 3361 9,97 16,10 1850 228 2,7 1,61 7402 18130 41%

 

Outturning is not about sustaining some g's at a specific speed, it is about turning as fast as possible at whatever speed suits your aircraft best.

 

I also fail at maintaining 3.4g in the P-51 at 370 km/h, at an IAs of 230 mph I manage 21.1s sustained which results in 3.3g sustained.

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9 hours ago, JtD said:

 

Actually, it does. If I am flying both of them, using your aircraft setup, I get the K-4 to outturn the P-51 no problem at sea level. No flaps used.

 

Turn time as flown (right hand turns), tech specs as given by the devs. Other figures calculated using physics. The only thing the P-51 is better at in game is being aerodynamically more clean - which it is.

 

Aircraft Time Speed Weight Wing span Wing area Power Turn radius Load factor CL Induced drag Thrust Efficiency
P-51D15 19,8 260 4134 11,29 22,30 1650 228 2,5 1,45 8302 16792 49%
Bf109K4 19,1 270 3361 9,97 16,10 1850 228 2,7 1,61 7402 18130 41%

 

Outturning is not about sustaining some g's at a specific speed, it is about turning as fast as possible at whatever speed suits your aircraft best.

 

I also fail at maintaining 3.4g in the P-51 at 370 km/h, at an IAs of 230 mph I manage 21.1s sustained which results in 3.3g sustained.

 

Not sure why wing area is listed as 22.3 sq.m. for the P-51, the wing area should be 21.83 sq.m..

 

Anyway I did the testing numerous times, with and without auto rudder, to be sure. And the P-51 can maintain a higher load factor all the way for me in IL2, not by much, but enough that the K4 wont beat it around the circle. This is dramatically opposite in DCS.

 

Also I don't understand why you're not simply using the G meter the game provides you with? Avoids any mistakes calculating based off of IAS.

 

Finally keep in mind that the difference between the K4 & P51 in DCS is a whole 0.5 G's in sustainable load factor at 370 km/h, whilst in IL2 the difference is 0-0.1 G.  In short they're quite far from each other.

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36 minutes ago, Panthera said:

Also I don't understand why you're not simply using the G meter the game provides you with? Avoids any mistakes calculating based off of IAS.

 

I'm using a clock and a compass for determining turn times. The compass to determine the turn, the clock to determine the time. As a result, I get what aircraft outturns the other, very accurately. Involves no calculations with IAS.

 

What do I need a g meter for (a reading that's unsuitable for accurately measuring sustained turn performance, in addition to being superfluous), and what's so difficult about IAS, in particular at sea level in standard atmosphere?

 

36 minutes ago, Panthera said:

Finally keep in mind that the difference between the K4 & P51 in DCS is a whole 0.5 G's in sustainable load factor at 370 km/h, whilst in IL2 the difference is 0-0.1 G.  In short they're quite far from each other.

 

I honestly don't care what it is like in DCS. I'm sure in Secret Weapons of the Luftwaffe the relative performance between a G-10 and a P-51 was different again. It's just as irrelevant for Il-2.

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Ok, well let me put it like this then:

 

A 0-0.1 G difference in sustainable load factor is too small a difference based on the physical data of the aircraft. DCS is much more in line with expected performance difference here. If you don't care about this, well then I don't know what to tell you.

 

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Just to contextualize this thread and to remind certain individuals once again, here was the data extracted from the previous '109 sustained turn performance' thread from late last year. Data tested by HomicideHank under agreed comparable conditions (back-to-back tests, 400L fuel, autumn map conditions). This was the data set we got:

 

1205615680_mmhmm.thumb.jpg.bb94035ba10f3af6e693fffc02fab47f.jpg.6078bf51aca75c8b4e6c8cb6f70093ee.jpg

 

Putting into context Yak Panther's analysis of the RAE chart... giving a CL of 1.494 and having re-read through some of the data provided in that previous thread, notably Holtzauge who made statements that the CLmax was 1.4 for the P-51 and 1.43 for the Bf 109... I can see where misunderstanding and a significant discrepancy could set in. I'm curious to know if this is why the P-51 is able to match or outperform certain models (in-game) of the Bf 109 G/K at low speed and co-energy.

 

I'll obviously wait and see what Greg comes up with in his future video... which may shine more light, but the fact is the P-51 (in-game) is capable of outperforming the Bf 109 G-14/K-4 co-energy in the turn at comparative fuel loads... the point being this is happening at speeds where it would be expected to be at a disadvantage.

 

Think this concern is self explanatory frankly, but if you want to argue how the two aerofoils used are "close enough" in lift production and are negligible in difference at such low speed go ahead. I'm not buying it.

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Hank turns his P-51 a good second faster than I do, guess I'll have to double check. It would give the P-51 an extremely good overall efficiency and a cl of around 1.5.

 

Does anyone happen to know the blade width of the Hamilton Standard and the VDM props?

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1 hour ago, Aurora_Stealth said:


Putting into context Yak Panther's analysis of the RAE chart... giving a CL of 1.494 and having re-read through some of the data provided in that previous thread, notably Holtzauge who made statements that the CLmax was 1.4 for the P-51 and 1.43 for the Bf 109... I can see where misunderstanding and a significant discrepancy could set in. I'm curious to know if this is why the P-51 is able to match or outperform certain models (in-game) of the Bf 109 G/K at low speed and co-energy.


No comment on the experimental turn times, but just to clarify in case of misunderstanding:

 

The Yak Panther's analysis of the RAE chart is at 3g power on: he is simply showing that the input numbers he used from the chart, come to much the same thing as the assumption in the key to the chart, which is 1.49  

 

It would have been surprising if it was anything else, since the chart was drawn using the assumption that the Clmax at 3g was 1.49 ie he was simply confirming, in the end, that the RAE can, in fact, do simple calculations without elementary errors.

 

"Using a weight of 5600 lbs*3, a wing area of 174 ft^2, a density = 12k ft, .84 kg/m^3, at 192 mph, I get a Cl of 1.494." 

 

(I would have calculated it as 1.478, but that may simply mean that while the US standard day air density at 12,000ft I use from a calculator was 0.8491, the number the RAE used may have been slightly different again. This is all just a ~1% difference, ie within rounding error.) 

 

RAE

1.49 at 3G power on was extrapolated figure. 

1.4 is the RAE experimentally determined, power off 1g figure given in their table. (Using their inputs, at SL, I make it 1.39: again they probably thought that specious accuracy here was futile given the difficulty of accurate speed measurement).

 

Game

1.39 is K-4 in the game. (Same at both ends of the speed/weight scale).

1.34 is P-51D in the game at min weight and speed - at max weight and stall speed, 1.37 (do not ask me why: possibly external stores mess with the results).

 

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1 hour ago, unreasonable said:


No comment on the experimental turn times, but just to clarify in case of misunderstanding:

 

The Yak Panther's analysis of the RAE chart is at 3g power on: he is simply showing that the input numbers he used from the chart, come to much the same thing as the assumption in the key to the chart, which is 1.49  

 

It would have been surprising if it was anything else, since the chart was drawn using the assumption that the Clmax at 3g was 1.49 ie he was simply confirming, in the end, that the RAE can, in fact, do simple calculations without elementary errors.

 

"Using a weight of 5600 lbs*3, a wing area of 174 ft^2, a density = 12k ft, .84 kg/m^3, at 192 mph, I get a Cl of 1.494." 

 

(I would have calculated it as 1.478, but that may simply mean that while the US standard day air density at 12,000ft I use from a calculator was 0.8491, the number the RAE used may have been slightly different again. This is all just a ~1% difference, ie within rounding error.) 

 

RAE

1.49 at 3G power on was extrapolated figure. 

1.4 is the RAE experimentally determined, power off 1g figure given in their table. (Using their inputs, at SL, I make it 1.39: again they probably thought that specious accuracy here was futile given the difficulty of accurate speed measurement).

 

Game

1.39 is K-4 in the game. (Same at both ends of the speed/weight scale).

1.34 is P-51D in the game at min weight and speed - at max weight and stall speed, 1.37 (do not ask me why: possibly external stores mess with the results).

 

 

Sure, I accept what your saying regarding the RAE. Although it should be said the RAE was analysing and testing a Bf 109 Emil and probably not in an ideal condition, also considering the work done to redesign the wing and improve aerodynamics later on in the series (some drag was also added for sure especially in the late G series but I digress); I'd still consider it a minimum/conservative number when regarding discussion of the K-4.

 

Sorry, just so I'm comparing apples with apples regarding the K-4 - to clarify you've calculated the Cl as 1.39 (in-game) for power-on @1g or @3g?

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Just now, Aurora_Stealth said:

 

Sure, I accept what your saying regarding the RAE. Although it should be said the RAE was testing a Bf 109 Emil and probably not in an ideal condition, also considering the work done to redesign the wing and improve aerodynamics later on in the series (drag was also added for sure); I'd still consider it a minimum/conservative number when regarding discussion of the K-4.

 

Just so I'm comparing apples with apples regarding the K-4 - to clarify you've calculated the Cl as 1.39 (in-game) for power-on @1g or 3g?

 

I take the data from the specifications page, pairing minimum stall speed with minimum operating weight and maximum stall speed with maximum take off weight. Always at sea level density.  I suspect the min-min number is more reliable: usually they are very close, (within 1-2%) but occasionally there is a big gap, which may be an issue with external stores on the max-max number.

 

It is power at idle at 1g (based on looking at the speeds) - so directly comparable to the RAE experiment.

 

The game speeds are CAS (=TAS at SL) so the tech specs numbers and the manual's  ASI often conflict, which is why the RAE test with special pitot-static equipment was so interesting and unfortunately for us, almost unique.    

 

 

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2 minutes ago, unreasonable said:

 

I take the data from the specifications page, pairing minimum stall speed with minimum operating weight and maximum stall speed with maximum take off weight. Always at sea level density.  I suspect the min-min number is more reliable: usually they are very close, (within 1-2%) but occasionally there is a big gap, which may be an issue with external stores on the max-max number.

 

It is power at idle at 1g (based on looking at the speeds) - so directly comparable to the RAE experiment.

 

It is also CAS (=TAS at SL) so the tech specs numbers and the manual's often conflict, which is why the RAE test with special pitot-static equipment was so interesting and unfortunately for us, almost unique.    

 

 

Ah I see, interesting - thanks for explaining that.

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On 5/10/2021 at 8:17 AM, JtD said:

Hank turns his P-51 a good second faster than I do, guess I'll have to double check. It would give the P-51 an extremely good overall efficiency and a cl of around 1.5.

 

Does anyone happen to know the blade width of the Hamilton Standard and the VDM props?

You got it right. Hanks tests are all at the same arbitrary speed of 280kph. He also measured about the same, but somewhat inconsistent G at the same speed. Which explains why all this numbers hover around the same number with small variations.

 

I posted these last year. They are in close agreement with your tests.

 

This subject has come up about 3 times now, always by the same people, or at least supported by the same people. I generally despise "git gud" being response to a in game complaint but this seems to be actually going on here. Entire reason I posted the DCS video. 109 pilots in both games exhibit the same behavior in turn duels, generally getting stuck nose high retarding their turn etc. And these complaint posts have been full of people posting turn tests at random arbitrary speeds. To me that hints strongly that the sources of complaint are basing their complaint on anecdotal in game experience since none of them seem to know how to even do a sustained turn test.

 

This is, and always had been, a bunch of people who dont know what a sustained turn is claiming one plane out turns the other.

 

 

 

 

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10 hours ago, LColony_Red_Comet said:

You got it right. Hanks tests are all at the same arbitrary speed of 280kph. He also measured about the same, but somewhat inconsistent G at the same speed. Which explains why all this numbers hover around the same number with small variations.

 

I posted these last year. They are in close agreement with your tests.

 

This subject has come up about 3 times now, always by the same people, or at least supported by the same people. I generally despise "git gud" being response to a in game complaint but this seems to be actually going on here. Entire reason I posted the DCS video. 109 pilots in both games exhibit the same behavior in turn duels, generally getting stuck nose high retarding their turn etc. And these complaint posts have been full of people posting turn tests at random arbitrary speeds. To me that hints strongly that the sources of complaint are basing their complaint on anecdotal in game experience since none of them seem to know how to even do a sustained turn test.

 

This is, and always had been, a bunch of people who dont know what a sustained turn is claiming one plane out turns the other.

 

 

 

 

Haven't really been following the topic but I'm curious. Is there a difference between maximum performance turn vs max sustained turn? In-game stats give a longer time time than you posted.

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35 minutes ago, Legioneod said:

Haven't really been following the topic but I'm curious. Is there a difference between maximum performance turn vs max sustained turn? In-game stats give a longer time time than you posted.

Generally when someone refers to the maximum performance turn it means the best turn that can be obtained if the maximum amount of G available is commanded starting at the corner velocity of the aircraft, which is where the lift limit and the structural limit coincide. This can only be done once generally because the fighter does not have enough thrust available to maintain its corner speed.

 

In the bottom diagram you can see a sustained curve, this is where PS (specific excess power) is zero. When PS is zero the aircraft is performing a sustained maneuver that it can support without yielding either altitude or speed. If PS is less than zero, the aircraft must sacrifice either speed or altitude to maintain the given performance. Note that the peak sustained turn is on the left side of the graph, and occurs where the ratio of G to speed is greatest. The highest sustainable G with lowest possible  sustainable speed. This is why the turn tests people are doing at random speeds mean nothing. An aircraft can sustain turns all along the sustained turn curve, but it only hits its best sustained turn at one speed. Note that in the last image the advantage of two planes actually shifts at different speeds, so that the plane which actually has better sustained turn performance (peak) might not at a higher speed. If two planes are fairly close, such as the ones being discussed in this thread, picking turn test speeds way above the best sustained corner speed will result in either the results being flip flopped, even, or closer than reality. Especially when human error is taken into account.

 

The turn times given in the game are for fuel loads we have not been using here. For example the P-51 is loaded at 68% fuel as per game stats.

 

image.png.1df30c5ebb607a33e3f9cb712370a19b.png

image.png.195dd0e39dfa423532a13a2dbf1f5f81.png

 

 

 

http://2.bp.blogspot.com/-zFFKxVV4HAk/VcdzaJj8puI/AAAAAAAAAQQ/5060rBaej5A/s1600/Slide3%2B-%2BE-M%2BDiagram.JPG

 

F 15 Em Diagram

 

 

 

Energy Maneuverability Graphs - Aircraft Discussion - War Thunder -  Official Forum

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18 hours ago, LColony_Red_Comet said:

You got it right. Hanks tests are all at the same arbitrary speed of 280kph. He also measured about the same, but somewhat inconsistent G at the same speed. Which explains why all this numbers hover around the same number with small variations.

 

I posted these last year. They are in close agreement with your tests.

 

This subject has come up about 3 times now, always by the same people, or at least supported by the same people. I generally despise "git gud" being response to a in game complaint but this seems to be actually going on here. Entire reason I posted the DCS video. 109 pilots in both games exhibit the same behavior in turn duels, generally getting stuck nose high retarding their turn etc. And these complaint posts have been full of people posting turn tests at random arbitrary speeds. To me that hints strongly that the sources of complaint are basing their complaint on anecdotal in game experience since none of them seem to know how to even do a sustained turn test.

 

This is, and always had been, a bunch of people who dont know what a sustained turn is claiming one plane out turns the other.

 

 

 

Look you can call it "peak sustained turn" instead - great, the tests showed that at a constant speed and altitude, and at slow speeds which are meant to be clearly favourable to the Bf 109 G-14/K-4 - nothing of the sort translated in-game. This was quite obviously not a test of instantaneous turning ability.

 

We were proved correct. I'm not interested in whether or not the P-51 "could" achieve improved turn times at its best turning speed or at higher speeds, I'm interested why its performing better where it would not.

 

Comparatively... at co-energy and at slow speed there is an advantage shown consistently for the P-51.


It's also notable why the Bf 109 K-4 does not benefit here from increased boost @ 1.98 ata, where the P-51 does @ 75" - are you going to tell me the Bf 109 is lift limited here compared to the P-51 at slow speed? please do not bother attempting to do that.

 

Its been repeatedly pointed out that this is not the case in real life; even four days ago the below article was released with quotes and photographs of Mark Hanna explaining and showing how the G-10 had a comfortable advantage over the P-51 at slow speeds. The G-10 is just a somewhat lighter version of the identically engined and outwardly similar K-4. While it benefits from a slightly lower weight, they are not exactly going to be miles apart - are they.

 

https://vintageaviationecho.com/mark-hanna-pt-4/

 

"Particularly in a close, hard turning, slow speed dog-fight. It will definitely out-maneuver a P-51 in this type of flight, the roll rate and slow speed characteristics being much better"

 

"The roll rate is very good and very positive below about 400 km/h and the amount of effort needed to produce the relevant nose movement seems exactly right."

 

Again, that's never enough... (yes I know) - you want everything detailed black and white in a report and spelled out letter for letter... well like I said... wait for Greg then to release his video so he can explain the detail.

 

Your previous comments:

 

I generally despise "git gud" being response to a in game complaint but this seems to be actually going on here.

- So why say this.

 

Entire reason I posted the DCS video. 109 pilots in both games exhibit the same behavior in turn duels, generally getting stuck nose high retarding their turn etc.

- Do you conduct your turns with nose down?

 

And these complaint posts have been full of people posting turn tests at random arbitrary speeds.

- Constant speed @280 km/h at a tolerance of +/- 5% is not random. This was explained, if you read the information on the previous thread. Which you haven't.

 

To me that hints strongly that the sources of complaint are basing their complaint on anecdotal in game experience since none of them seem to know how to even do a sustained turn test.

- Really, so how come we accurately defined the test parameters and flew them precisely as agreed and back to back for accuracy?

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A P-51 @ 4300kg @ 1900hp climbs with a Bf109K-4 @ 3400kg @ 1850hp in the real world. Both at around 22m/s, if the charts are to be believed. If this was done in a game, folks would light their pitchforks and sharpen their torches in face of such a blatant violation of physics, but never bother to find out why.

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8 hours ago, Aurora_Stealth said:

I generally despise "git gud" being response to a in game complaint but this seems to be actually going on here.

- So why say this.

 

Because you guys are complaining about a problem that does not exist. It has become abundantly clear over the course of several different threads that none of persons doing the complaining seem to know how to actually do a sustained turn test. Moreover, I see 109s in il2 and dcs get out turned all the time, despite the fact that the 109 turns better in both games. So the only way any of you came to the conclusion that the 109 turns worse is either by not flying it well enough in game and therefore gaining the perception that it was worse, or you "tested" it after joining these threads and determined it was worse. But since your test methodology doesn't even test the thing you think is wrong, it clear that something is lacking either in in game flying abilities, or knowledge of aircraft performance. Or Both.

 

8 hours ago, Aurora_Stealth said:

- Do you conduct your turns with nose down?

I turn with the nose as level as possible. Nose down if the altitude permits it. Watch the DCS turning video I posted. Look how high that 109s nose gets. You really want to argue that his nose should be that high? I see this exact thing in il2 as well. It happens because the 109 is a small plane with a ton of torque. People try to push it too hard and they end up with their nose high because they lose speed etc.

 

8 hours ago, Aurora_Stealth said:

- Constant speed @280 km/h at a tolerance of +/- 5% is not random. This was explained, if you read the information on the previous thread. Which you haven't.

I was literally in that thread where you did that test. I know why you did it. Its random because you cant just pick a speed, especially not the same one for both planes, and test for best sustained turn. Thats not how it works. Its also very hard to test, which is why several of you posted contradictory and inconsistent data.

 

8 hours ago, Aurora_Stealth said:

- Really, so how come we accurately defined the test parameters and flew them precisely as agreed and back to back for accuracy?

Because you didnt.

 

 

Read my post with the charts.

 

Edited by LColony_Red_Comet
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40 minutes ago, LColony_Red_Comet said:

Because you guys are complaining about a problem that does not exist. It has become abundantly clear over the course of several different threads that none of persons doing the complaining seem to know how to actually do a sustained turn test. Moreover, I see 109s in il2 and dcs get out turned all the time, despite the fact that the 109 turns better in both games. So the only way any of you came to the conclusion that the 109 turns worse is either by not flying it well enough in game and therefore gaining the perception that it was worse, or you "tested" it after joining these threads and determined it was worse. But since your test methodology doesn't even test the thing you think is wrong, it clear that something is lacking either in in game flying abilities, or knowledge of aircraft performance. Or Both.

 

I turn with the nose as level as possible. Nose down if the altitude permits it. Watch the DCS turning video I posted. Look how high that 109s nose gets. You really want to argue that his nose should be that high? I see this exact thing in il2 as well. It happens because the 109 is a small plane with a ton of torque. People try to push it too hard and they end up with their nose high because they lose speed etc.

 

I was literally in that thread where you did that test. I know why you did it. Its random because you cant just pick a speed, especially not the same one for both planes, and test for best sustained turn. Thats not how it works. Its also very hard to test, which is why several of you posted contradictory and inconsistent data.

 

Because you didnt.

 

Read my post with the charts.

 

The whole point of keeping a constant altitude within a test to a 5% tolerance is that... the aircraft does in fact have to be kept nose level to stay within that limit. Otherwise... the altitude changes and breaks the parameters...

 

If the nose is anything other than level... then it is no longer a flat or constant altitude/speed turn. That is then a climbing/diving turn which is modifying the turning circle/rate. Also to use flaps would be modifying this also, which FYI is not what we're discussing here. We wanted a direct comparison at given parameters to test a hypothesis. Comparing two aircraft at their best turning speeds may seem appropriate for a combat situation (don't deny it) but this is about what happens under conditions that are meant to favour the Bf 109.. and it still doesn't happen...

 

Why would people complain about the problem so strongly in the first place if it is so obvious that the problem does not exist? why do you think people had to end up testing it so thoroughly and with such personal time spent  in the first place?

 

If you have a better test methodology... please go ahead if you're that accurate (within 5% speed and 5% altitude throughout) during the recorded test... then please come up with the test data and repeat it 10 times over for each aircraft... under directly the same parameters in a repeatable way so we can compare it like for like.

 

Otherwise, you're just telling us your opinion from in-game experience, which is fine; but it doesn't compare apples to apples.

 

Yes you can pick that speed and for very good reason, it is relevant because its the optimal sustained turning speed for that aircraft (and realistically) we tried to get to 270 km/h but the risk of stall makes it very difficult so we accepted 280 km/h - I'm trying to focus on the Bf 109's best turning speed as written in the specifications and provided in IL-2 in the briefing screen for your information. There are optimal turning speeds for all aircraft and these are given alongside an altitude and a set of weights and conditions (parameters).

 

Yes its very hard to test it, but the results were consistently showing an advantage to the P-51, so regardless of what you're trying to say - the net outcome when factoring altitude between different tests was considered comparable.

 

9 hours ago, JtD said:

A P-51 @ 4300kg @ 1900hp climbs with a Bf109K-4 @ 3400kg @ 1850hp in the real world. Both at around 22m/s, if the charts are to be believed. If this was done in a game, folks would light their pitchforks and sharpen their torches in face of such a blatant violation of physics, but never bother to find out why.

 

What kind of claim is this? you're being opaque about the details of what you are actually saying and comparing, 1,850 hp is with 1.8 ATA and it doesn't appear to be apples with apples.

 

The Packard Merlin V1650-7 is rated @ 1,720 hp (1,650 @ sea level) - perhaps you may be able to argue that exhaust gases are helping output for the P-51 but then again the Bf 109 would also benefit but to a lesser extent. If you think that a Mustang out climbs a Bf 109 K-4 at WEP at sea level then frankly... a very serious error has been made.

 

Even the earlier G series can comfortably out-climb the Mustang at best climbing speeds, and quite easily at most altitudes. So this is a very strange point to be making frankly, and I'm not sure what your figures / point here is based on. Can you be a bit more transparent about how you're getting to these figures please so we can have an honest conversation.

 

Thanks,

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22 minutes ago, Aurora_Stealth said:

I'm trying to focus on the Bf 109's best turning speed as written in the specifications and provided in IL-2 in the briefing screen for your information.

And this is probably your mistake. 280 km/h is a speed where the Mustang wins on the 109 in sustained turn.

 

See here:

P51D Fw190D9 Me109K4 stationary turn rate PAF PA49.JPG

 

At 270 km/h or 280 km/h, the 109 loses about half a second on the Mustang. Having the DC engine won’t help you there. You need to go faster with the stronger engine to further gain on turn. You need to go at least almost 300 km/h to start winning on the Mustang, until you lose again on excess energy around 550 km/h. But there you will not notice less turning, but you will bleed more energy in maneuvering. Flying both aircraft at 280 km/h is indeed good for nothing except seeing the 109 lose, when in fact there are speeds where it can win on the Mustang. The 109K4 really can even reach higher absolute turn. But if you are not in that speed range, bad for you. If people were less greedy on the stick, the Mustang would have a much harder time.

 

I doubt that the devs would state ideal turn times of their FM for various reasons. But they state reasonable setups.

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