Thoughts on the K-4 Manouverability

[JtD]

8 hours ago, Aurora_Stealth said:

What kind of claim is this?

 

Based on real life data, available on wwiiperformance.org. You can either go there and read it now or wait until some youtube dude turns this into a video. Charts in question would be

http://www.wwiiaircraftperformance.org/mustang/P-51B_24777_Climb.jpg

http://www.wwiiaircraftperformance.org/mustang/p-51b-24771-climb-blue.jpg

http://www.wwiiaircraftperformance.org/mustang/na-p51b-150grade-climb.jpg

 

http://www.wwiiaircraftperformance.org/me109/Me_109K-4_DB605DB_Climb.jpg

 

It's 75"/25lb and 1.8ata.

 

8 hours ago, Aurora_Stealth said:

If you think that a Mustang out climbs a Bf 109 K-4 at WEP at sea level

 

I'm not thinking anything, I'm quoting data. Feel free to present better data, in particular for the 109K-4 (it falls in line with http://kurfurst.org/Performance_tests/109G14_PBLeistungen/files/PBG14_ROC_SNplusMW50.jpg ,but still is just calculated not tested).

 

Hope that clarifies it sufficiently.

 

On 5/10/2021 at 2:17 PM, JtD said:

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

 

I do now, about 10" for the Hamilton, about 12" for the VDM. So the VDM has an about 35% higher load. Interesting. Time to crunch some numbers.

[JV69badatflyski]

12 hours ago, ZachariasX said:

 

 

.

 

Hi!
sorry to jump into your great discussion (really, no sarc here) but i was triggered by  ZachariasX 's post with Holtzauge Graph.
Could someone explain what good it is to compare planes with the same amount of fuel?
In this Case (Graph) we're in a Sci-Fi Harry potter magical situation:
The K4 sit on the ground, fully loaded, engine cut
The D9 just took off without an enough warmed up engine and it's bounced just after take off.
The 51 is at it's best situation having used about just more than 50% of it's fuel.

Even if i do like Holtzauge graph's, this one looks like number grinding  and maybe it's purpose wasn't to prove a certain turn rate, as the situation depicted in the graph is impossible, so using this graph to show that  "X" airplane had the adge in turn over "Y" airplane is simply wrong.
If you want to compare something, it has to be realistic, you'll never have fully loaded aircrafts in the air, warmup, taxi, takeoff, formation, climb takes times...and fuel...and oil 
 

4 hours ago, JtD said:

I do now, about 10" for the Hamilton, about 12" for the VDM. So the VDM has an about 35% higher load. Interesting. Time to crunch some numbers.

If you have VDM data, it would be very nice of you if you could share, i'd like to learn a little in OpenVSP, but the data required is hardcore to fill...and to find....
To give you an idea:
http://openvsp.org/wiki/lib/exe/fetch.php?media=workshop20:propeller.pdf

[JtD]

33 minutes ago, JV69badatflyski said:

If you have VDM data

 

Well, not really, I was basically looking for the blade width of a K-4 prop in order to make assumption about the prop loading and the resulting efficiency. I found the K-4 uses a 9-12159.10 prop blade with a 10.2% width and a 7% thickness. The 10.2% is what I was looking for and I stopped looking once I found it. (Width (i.e. chord) is 10.2% of the diameter (i.e. span) and thickness is 7% of the width/chord.)

 

Anyway, looking into what this would do to relative prop efficiencies, it looks to me as if the K-4 is indeed somewhat handicapped at low speed, but not catastrophically so. My unvalidated quick guess spreadsheet suggests an efficiency of maybe 5% lower, if that much, in the turning/climbing speed range than what the lighter loaded Hamilton on the P-51 achieves. Not a game changer, so for now it appears hardly worth further investigation.

[ZachariasX]

2 hours ago, JV69badatflyski said:

If you want to compare something, it has to be realistic, you'll never have fully loaded aircrafts in the air, warmup, taxi, takeoff, formation, climb takes times...and fuel...and oil 

That is not the point of the graph.

 

2 hours ago, JV69badatflyski said:

Could someone explain what good it is to compare planes with the same amount of fuel?

What the graph shows is an aerodynamic analysis of the three airframes in regards of their maximum sustained turn rate at said ratings. Nothing else.

 

2 hours ago, JV69badatflyski said:

, so using this graph to show that  "X" airplane had the adge in turn over "Y" airplane is simply wrong.

It is simply true, as this graph only wants to comare the airframes. If you loaded the airframes differently, you'd be comparing the effect of the different loadouts and you get an arbitrary result that is good for nothing. In this example, a plausible and resonable loadout was chosen that is possible for all three planes evenly.

 

If you want to make a meaningful (scientific) analysis, you have to forget all your "stories", your "contexts", your "gaming experience". That graph has nothing to do with that. It even doesn't have anything to do with this game, although AnP and his team achieved the remarkable feat of providing us a simulator, that in real time approximates these values rather well. What we have here are three almost equal airframes, about the same size and about 3.5 tons and twice 4.5 tons in weight respectively. The idea of this graph is how the airframes perform under equal conditions. Loadout is one of these conditions. It is pointless to add one ton to one plane and only half a ton to the other, because then you don't have to do any calculations, you know the result.

 

But knowing this graph, you know that if you are in either a 109K4 or a 190D9 and you go after a Mustang with a full fueltank, you'll win on him in any given circumstance. But if the Mustang is already on 50% internal fuel, you know you can't get greedy on the stick to gain angles on him for long, as he WILL catch you then.

 

The graph actually depicts nicely why Lufties here cry about über-Mustangs. They are just too often too greedy in getting angles. The Mustang can get greedy as well, but even though his turn performance drops, the silly 109 that goes slow will lose more. Under 300 km/h is a bad place to be for the 109K4 and no unicorn engine can help it there.

 

The graph also explains why the 109F4 is probably the most popular 109 in MP. When you lighten the aircraft, the whole plot shifts to the left. Conversely, when you just add more power, the peak shift upwards along the Clmax/stall line, see here:

 

 

@Holtzauge was kind enough to draw that one out for us, there.

 

Here, you can see actually how close the left part of the graphs are between the 109K4 and the Mustang:

 

The Fw190 is shifted to the right, but the 109K and the Mustang are really very close. If you ditch half a ton of weight from the 109, even though you also ditch some power, the black graph will move to the left due to the loss of weight (it would sort of act like a bigger wing in the hand drawing above) and it will move the apex downward due to the lack of power (also shown as in the drawing). This means that the 109F4 is a very competitive turner up to best turn with most aircraft.

 

If the 109F4 is (usually) flown too slow (as any other aircraft) in a close in turnfight, it still retains an upper hand on most other aircraft that ALSO are flown to slow. Spitfires and Hurricane being prominent exceptions. This means, if everybody and you are doing it wrong, you will still be competititive in the 109F4. This is the normal case in fast food MP. The 109K4 on the other hand punishes you for flying too slow, as on the wrong side of the graph, lesser aircraft get the upper hand.

 

The whisdom here is:

 

If everybody (this includes you!) is doing it wrong, you can win in the 109F4.

If everybody (this includes you!) is doing it wrong, you will lose in the 109K4.

 

Test question: Why does everybody like the 109F4?

 

Funny enough, this applied also to the pilots back then. The Friedrich was the popular 109 "because it always flys well". Despite the fact that the 109K4 is a far superior aircraft. The F4 doesn't kick you over the cliff in terms of competitiveness when going too slow as the heavy 109's do. This also made the Spit such a reliable and popular ride in a dogfight. That is the aircraft that, if you end up in the dump, will put everyone messing with you in that dump even deeper in than you already are. Of all the pilots going down the sewer, the Spit pilot has the "get me outta here CLEAN!" wildcard. And pilots loved the Spit just for that, despite it being largely outdated later in the war.

 

Edited May 13, 2021 by ZachariasX

[Holtzauge]

I think @ZachariasX already gave a good explanation above about the weights used in the chart I did and that the intention was to compare aircraft at similar conditions. One could of course argue that full or 50% fuel would be "fair" but I think an even fairer comparison was to compare the aircraft with the same fuel load implying the same endurance. This is of course also a simplification since they don't have the same fuel burn but it's anyway much fairer than penalizing the P-51 for its outstanding range.

 

Another way to compare the planes would be for me to knock of another 50 Kg in weight to assume that the K4 had taken off and climbed to the chart altitude. However, this will just translate all the curves in the chart up a few tenths of a mm and it certainly won't change the relative relationship. However, I just thought of that the chart I drew is actually very fair even given that the K4 has a full fuel load: The K4 has just been bounced and dropped its external fuel tank @JV69badatflyski!

[LColony_Kong]

Its also worth noting that in Holtzauges excellent graph the P-51 and 190 are at 388kg and the 109 is at 400L. 299kg would be 400L for the Mustang or 190. Were it compensated for the Mustang would be alot closer to the 109. Even with the 109 having a lighter load here the P-51 is less than 1 second behind.

[JV69badatflyski]

3 hours ago, ZachariasX said:

That is not the point of the graph....

 

 

It wasn't the goal to dispute the results, it's just the context of the numbers that triggered me.
It had nothing to do with stories or game experience or whatever, but because i found the situation, the context of the fuel weight, abnormal.
I actually never flew the 109 in BoX...not enough free time so when able to boot the game, i use my favorite plane, the Anton.
But will try the F4, as i have some experience with it in CoD, just to compare.
 

2 hours ago, Holtzauge said:

.....The K4 has just been bounced and dropped its external fuel tank @JV69badatflyski!

Even if i still find the context slightly hair-stretched, i see your point and understand now what you ment with the calculation.
 

17 minutes ago, LColony_Red_Comet said:

Its also worth noting that in Holtzauges excellent graph the P-51 and 190 are at 388kg and the 109 is at 400L. 299kg would be 400L for the Mustang or 190. Were it compensated for the Mustang would be alot closer to the 109. Even with the 109 having a lighter load here the P-51 is less than 1 second behind.

388Kg for the 190 is just 22kg under the max fill of the tanks. so it was bounced on the take off just at the end of the runway 
Again, i don't dispute the numbers at all, i just find the situation(the context for the numbers) non representative of most aerial combats in 44/45.
So we can agree on desagree but agree on the result numbers.

i've enough derailed this topic, back to the discussion.

 

[Holtzauge]

8 minutes ago, JV69badatflyski said:

i've enough derailed this topic, back to the discussion.

 

NP, and I now think I recall where the 388 Kg came from: It was to compare the P-51 with the Fw-190D9 at full fuel load. Finally about weights used : It's actually not uncommon to compare turn rates at full T/O weight. It's  a theoretical number for sure but you have to use something as a base and full internal fuel load is not uncommon.

 

41 minutes ago, LColony_Red_Comet said:

Its also worth noting that in Holtzauges excellent graph the P-51 and 190 are at 388kg and the 109 is at 400L. 299kg would be 400L for the Mustang or 190. Were it compensated for the Mustang would be alot closer to the 109. Even with the 109 having a lighter load here the P-51 is less than 1 second behind.

 

Good that you caught this! When I did a quick simulation run just now with 400 l fuel in the P-51 just like in the K4 the apex of the P-51 curve with 75" boost for me goes up to slightly over 18 deg/s @ 295 Km/h TAS in the chart so basically on par with the K4. No way the simulations are accurate to within a few tenths of a deg/s so for me they are with same fuel load equal in sustained turn rate. Interesting. Without the simulation result I would have said that the K4 beats the P-51 but apparently with the same fuel load they are on par.

[LColony_Kong]

2 hours ago, Holtzauge said:

 

Good that you caught this! When I did a quick simulation run just now with 400 l fuel in the P-51 just like in the K4 the apex of the P-51 curve with 75" boost for me goes up to slightly over 18 deg/s @ 295 Km/h TAS in the chart so basically on par with the K4. No way the simulations are accurate to within a few tenths of a deg/s so for me they are with same fuel load equal in sustained turn rate. Interesting. Without the simulation result I would have said that the K4 beats the P-51 but apparently with the same fuel load they are on par.

Thanks for running that extra simulation, I think this pretty much puts the final nail in the coffin. The 75 inch mustang in il2 is also so close to k4 it might as well not matter, k4 has a small and hard to measure advantage in game. So that lines up il2 with your simulation pretty much exactly.

 

 

And that may also contribute to some users perceptions between this game in DCS, since the 150 octane gas that was the only gas used by 51s in the eighth air force from June 44 to the end of the war, does not exist in DCS. The il2 devs are the first sim as far as I know to ever actually get this right and include the 150 grade mustang.

 

So when a 109 pilot encounters a P-51 in IL2 they may come away thinking the Mustang more agile than it is due to the fact that:

 

-the K4s torque makes it harder to fly. 

-The Mustang has usable flaps.

-The Mustang has g-suit

-And they might be fighting a 1980bhp 150 grade mustang whose turn performance is tenths of a second different.

Edited May 13, 2021 by LColony_Red_Comet

[Holtzauge]

A thought just struck me: If we assume 150 octane for the P-51 then in all fairness why not assume C3 fuel for the K4?

 

In that case the K4's curve assuming 1.98 ata is pushed up to the right giving 19 deg/s at 325 Km/h TAS again making the K4 the top dog.

 

Maybe in-game the problem is like @ZachariasX pointed out earlier: People are slowing down to much? Maybe the tech specs saying turn rate at 280 Km/h makes people target that instead of 309 Km/h IAS (325 Km/h TAS) at 1 Km?

[Aurora_Stealth]

14 hours ago, JtD said:

Based on real life data, available on wwiiperformance.org. You can either go there and read it now or wait until some youtube dude turns this into a video. Charts in question would be

http://www.wwiiaircraftperformance.org/mustang/P-51B_24777_Climb.jpg

http://www.wwiiaircraftperformance.org/mustang/p-51b-24771-climb-blue.jpg

http://www.wwiiaircraftperformance.org/mustang/na-p51b-150grade-climb.jpg

 

http://www.wwiiaircraftperformance.org/me109/Me_109K-4_DB605DB_Climb.jpg

 

It's 75"/25lb and 1.8ata.

 

I'm not thinking anything, I'm quoting data. Feel free to present better data, in particular for the 109K-4 (it falls in line with http://kurfurst.org/Performance_tests/109G14_PBLeistungen/files/PBG14_ROC_SNplusMW50.jpg ,but still is just calculated not tested).

 

Hope that clarifies it sufficiently.

 

I do now, about 10" for the Hamilton, about 12" for the VDM. So the VDM has an about 35% higher load. Interesting. Time to crunch some numbers.

 

Thanks for providing the data (and to all). I appreciate that, will spend some decent time reading through it as I've not had a chance properly today.

 

I would like to mention one thing off the bat - that climbing data is for a P-51 B, not the D (as we have in-game) they are slightly different - the B model would in practice be somewhat lighter.

 

But as for engine data, yeah that's really interesting @150 octane - thanks for the info.

 

I'm not surprised that it is close in turning performance between the K-4 and P-51 however it does seem very, very strange that it would cross over at such low speeds below 300 km/h and I do remain very skeptical about that... which is why I mentioned getting a second opinion on it. Please don't take offence at that.

 

The information provided also doesn't seem to explain why a Bf 109 G-14 would be out-turned by the P-51. It should be lighter to a K-4, and I find it interesting that the quoted weight on that given chart provided appears to note around 3,400 - 3,500 kg. That sounds a lot like the weight of a G-14 with underwing gondolas to me.

 

Anyway, cheers.

[LColony_Kong]

21 minutes ago, Holtzauge said:

Maybe in-game the problem is like @ZachariasX pointed out earlier: People are slowing down to much? Maybe the tech specs saying turn rate at 280 Km/h makes people target that instead of 309 Km/h IAS (325 Km/h TAS) at 1 Km?

If you havent seen it check the video I linked above from DCS. Different game, but the 109 behavior you see is exactly what happens with il2 pilots as well. They do get too slow, but I dont think this is about trying to hit a particular turn speed. Best sustained turn speed is going to be hit anyhow if the pilot pulls to the lift limit and lets the speed bleed off, at least in these ww2 birds. Modern jets are a different story. The problem is that most of them are too greedy on the stick and they end up either constantly bucking the stall and having to correct (which hurts their average turn rate) or they end up in a nose high condition like in the video, which results from fighting the turn improperly. As you can see in that video (and this happens the same way in il2) they end up practically fighting to keep the plane in the air. It is all entirely avoidable it he pilots stops trying to give themselves a hernia with their control stick.

 

Edited May 13, 2021 by LColony_Red_Comet

[Holtzauge]

7 minutes ago, LColony_Red_Comet said:

If you havent seen it check the video I linked above from DCS. Different game, but the 109 behavior you see is exactly what happens with il2 pilots as well. They do get too slow, but I dont think this is about trying to hit a particular turn speed. Best sustained turn speed is going to be hit anyhow if the pilot pulls to the lift limit and lets the speed bleed off, at least in these ww2 birds. Modern jets are a different story. The problem is that most of them are too greedy on the stick and they end up either constantly bucking the stall and having to correct (which hurts their average turn rate) or they end up in a nose high condition like in the video, which results from fighting the turn improperly. As you can see in that video (and this happens the same way in il2) they end up practically fighting to keep the plane in the air. It is all entirely avoidable it he pilots stops trying to give themselves a hernia with their control stick.

 

Yes, but even if you start off at high speed and bleed off speed from the instantaneous turn you need to know when you have "hit" the speed for best turn rate and at this point in time unload slightly to stay there. It's very tempting to keep up the back pressure on the stick to keep up the unsustainable turn rate sacrificing speed for turn rate and getting "behind the curve" which is a temptation that I think many are falling for. However, some may have that discipline but maybe still don't understand that the apex of the curve is not as low as the speed the tech specs mention.

[LColony_Kong]

8 minutes ago, Holtzauge said:

 

Yes, but even if you start off at high speed and bleed off speed from the instantaneous turn you need to know when you have "hit" the speed for best turn rate and at this point in time unload slightly to stay there. It's very tempting to keep up the back pressure on the stick to keep up the unsustainable turn rate sacrificing speed for turn rate and getting "behind the curve" which is a temptation that I think many are falling for. However, some may have that discipline but maybe still don't understand that the apex of the curve is not as low as the speed the tech specs mention.

That's one method of doing it but personally I just pull till I get either audio or visual cues that I'm on the edge, then unload slightly. There is little time too look at the speed guage and keep eyes on bandit etc.

 

But I agree totally that stick greed is the ultimate issue.

[JtD]

Having spend a good portion of yesterday turning the 109K and the P-51 at sea level, I've come to the conclusion that their performance matches pretty well with what the first to charts YakPanther posted here     show. I've got slightly different performance, but this is explained with a slightly different fuel load. I also got better turns out of the P-51 than I initially got, which makes the gap between the two smaller than expected.

 

Anyway, point to make is that the Bf109K-4 doesn't really perform a lot different between say 280 and 310, and since flying it at the minimum edge of that range is quite hard already, I suppose if you really do a sustained turn fight in one, you won't be flying it directly at the lift limit. It's hard to fly a mostly stalled aircraft, even in Il-2, and I'm guessing those who do and lose, aren't really complaining about the sustained turn performance.

 

Which leads us to a few more observations on relative performance. One - the P-51 is really fast, even down low. This means it has a lot of speed to bleed in the not sustained part of the fight. Two - the P-51 is quite heavy, which means it carries more energy than a Bf109K at the same speed and altitude. Three - the P-51 is aerodynamically extremely clean, which means it does not bleed speed and energy as quickly as a Bf109K. Four - the P-51 comes with a g-suit, and entering a turning contest at medium to high speed, blackout is bothering me quite a bit. Five - subjectively, I find the P-51 easier to fly smoothly, saving energy and getting closes to the limit.

 

All these points add up to the result that if I started at medium or higher speeds or maybe not at sea level altitude, in a P-51D I'd always effectively outturn me in a Bf109K way before sustained turn performance truly starts to matter. The only way to counter this would be to keep climbing in the 109K (spiral climb), but doing this comes with its own set of risks.

 

[ZachariasX]

11 hours ago, Holtzauge said:

Maybe in-game the problem is like @ZachariasX pointed out earlier: People are slowing down to much? Maybe the tech specs saying turn rate at 280 Km/h makes people target that instead of 309 Km/h IAS (325 Km/h TAS) at 1 Km?

I think @JtD gave a good explanation why in game it is easier to get most from the Mustang than the same from the 109. i tend to agree on these points.

 

Another factor that I see that is working against the 109 is (in game) it's remarkable ability to pull a lot of alpha for a snapshot. This might be subjective (and I thus treat the following as mere personal impression), but to me it is like that "if I really need to take that shot" I can pull the 109's nose to a very high angle, seemingly way past its stalling angle and take a snapshot. But you do this, the aircraft will slow down very quickly. It would also be an explanation why people feel that in the 109 they feel less g effects than in other planes, notably the Spit with a relatively low max. AoA. Going above the stalling angle will give you nose up but less added g. But you surely slam the brakes doing so. Doing this in the Spit will send you to sleep quickly as high alpha means very high g. Or you'd flick out and don't have a firing solution.

[Bremspropeller]

@JtD Did you spot a difference in terms of sustainable g concerning the g-suit in the Mustang and the 109 onlce slowed down to that speed-range?

 

I feel my pilot is turning into a vegetable a little too easily when spending some time in the 2-3g realm. I'm wondering if the g-suit is making a diiference there as well, or if it will only help at higher g-levels. Also wondering how they made the g-suit work, but that's a different topic altogether.

[von_Tom]

 

Just a general comment to throw into the mix - if I get stuck in a turn fight I always try to climb nose up so I can utilise the 109's climb ability at slow speeds.  The idea is of course to force the other pilot/aircraft to lose energy to the point where they have to move to more horizontal flight whilst I keep climbing.  The 109 has exceptional slow speed control.

 

If I know I can out-turn horizontally then I will (but you don't actually know the other pilot's aircraft setup so this can be a lottery) but as a rule I really don't like horizontal turn fights because all you do is end up in a descending turn and you end up low, slow and vulnerable. 

 

Never turn to death.

 

von Tom

[JtD]

Zach, you're making an excellent point which should be number 6 on the my list, or maybe even number 1. I couldn't resist, and went into the game and using Tacview I checked out what difference I actually pull if I enter the turn with a P-51 and a K-4. Turns out (no pun intended), in the P-51 I'd typically pull around 24°/s which causes me to slow down from 330mph to 200mph within about 25s. In the K-4, I naturally pull the stick a lot harder (I use nose up trim a lot) and end up with 27°/s, but I drop from 530 km/h to 320km/h (same range as the P-51) within about 10s. I will have gained a little (30°), but now the P-51 is a lot faster and will gain on me, until we both enter sustained turn fighting. If I pull slightly less in the K-4, I can match the P-51, and if I pull even less, I can maintain about 22°/s for 35s. Which reverses the situation, the P-51 will initially gain on me, then I'll gain on it. Essentially, flying the Bf109K-4 a little bit more like the P-51 does the trick for me, and the planes are pretty much even.

 

(For reference: ballpark 19°/s is about sustainable.)

 

Bremspropeller, can't say I'm noticing a distinct difference between the K-4 and the P-51, but I've blacked out in the K-4 while I did not in the P-51 doing these turning tests. Can be because I'm a bit more gentle with the P-51, but can also be because of slightly higher tolerances. It definitely matters when entering the turns from higher speeds.

[LColony_Kong]

There is also the P-51s use of flaps and trim. Both can be a huge factor. Flaps in unsustained fighters and trim in either.

[Aurora_Stealth]

On 5/14/2021 at 7:24 AM, JtD said:

Having spend a good portion of yesterday turning the 109K and the P-51 at sea level, I've come to the conclusion that their performance matches pretty well with what the first to charts YakPanther posted here     show. I've got slightly different performance, but this is explained with a slightly different fuel load. I also got better turns out of the P-51 than I initially got, which makes the gap between the two smaller than expected.

 

Anyway, point to make is that the Bf109K-4 doesn't really perform a lot different between say 280 and 310, and since flying it at the minimum edge of that range is quite hard already, I suppose if you really do a sustained turn fight in one, you won't be flying it directly at the lift limit. It's hard to fly a mostly stalled aircraft, even in Il-2, and I'm guessing those who do and lose, aren't really complaining about the sustained turn performance.

 

Which leads us to a few more observations on relative performance. One - the P-51 is really fast, even down low. This means it has a lot of speed to bleed in the not sustained part of the fight. Two - the P-51 is quite heavy, which means it carries more energy than a Bf109K at the same speed and altitude. Three - the P-51 is aerodynamically extremely clean, which means it does not bleed speed and energy as quickly as a Bf109K. Four - the P-51 comes with a g-suit, and entering a turning contest at medium to high speed, blackout is bothering me quite a bit. Five - subjectively, I find the P-51 easier to fly smoothly, saving energy and getting closes to the limit.

 

All these points add up to the result that if I started at medium or higher speeds or maybe not at sea level altitude, in a P-51D I'd always effectively outturn me in a Bf109K way before sustained turn performance truly starts to matter. The only way to counter this would be to keep climbing in the 109K (spiral climb), but doing this comes with its own set of risks.

 

Well I'd expect the P-51 to be able to get a good snapshot coming in from a higher speed (especially when diving in); this is playing to its strengths and as you say it has more energy to "dump".

 

What I'm not so convinced of... is that (in a flat turn) the P-51 appears to be achieving similar angles while bleeding speed at a slower rate, its higher weight would imply a disproportionate rate of deceleration and it should be risky sustaining this as you go well below 300mph (480 km/h).

 

One consistently made point about the P-51 in real life, is it bleeds speed very quickly when pulling these high AoA's compared to other fighters (including the Bf 109) which may be advantageous for instantaneous turning and catching fighters out in snap shots... but once this speed drops below a point, the P-51 should be in a risky position. The higher acceleration and low speed handling should favour the Bf 109 here and it doesn't seem that apparent. Even with the slats out and the aircraft on the edge of a stall, the aircraft is still considered to be quite controllable. That's why you hear pilots say when the slats open they can pull more into the turn.

 

I guess the question now becomes... is that additional G being pulled sustainable? perhaps not... maybe that's why releasing pressure off the stick, recovering some speed up to 350 - 400 km/h and then repeating this is the key.

 

That sounds fairly consistent with what Erwin Leykauf was trying to get at in his explanations (just an an observation).

 

Using flaps in that situation may also just serve to decelerate the aircraft at a faster rate which may not be that beneficial in this case.

 

More food for thought.

[ZachariasX]

15 hours ago, Aurora_Stealth said:

That sounds fairly consistent with what Erwin Leykauf was trying to get at in his explanations (just an an observation).

What we have are two remarkably similar airframes. In normal flight regimes, there isn‘t much to choose between them given equal fuel weight. They give you the same for practical purposes.

 

I seriously doubt that, especially given the above, that you can read much into first hand accounts of that era regarding aerodynamics. Pilots back then had only a very dim understanding of aerodynamics at best, but they sure knew what works for them in battle. Hence any science derived from such accounts are highly circumstancial.

 

The topic about how much AoA you can pull and how fast a plane decellerates from doing so reflects only our sim and nothing else. But if it came to maintaining momentum in a high speed pullout, I‘d always go with the aerodynamically cleaner design, and the P-51 is head and shoulders above the competition in that deparment. Holtzauges graph above even shows that the P-51 tends to bleed less energy at a high speed pullout.

[Holtzauge]

I just did a C++ simulation comparing P-51D and Me-109K4 both at same fuel load 400 liters: Instantaneous turn at 3 Km altitude entry speed 168 m/s (605 Km/h) both maintaining 5 g for as long as possible.

 

How long will they be able to hold 5 g? Who can hold 5 g the longest? Who will be fastest when they cannot maintain 5 g anymore?

 

I have to say the results were not what I expected but when I did some ballpark estimates with pen and paper I understood why.

 

Anyone care to take a guess which plane won and why? 

[ZachariasX]

Mustang @75 inches: 25 sec @ 5 g

Bf-109K4, 1.8 ata: 20 sec @ 5 g

 

Mustang wins. Why? MURICA More efficient wing profile at high speeds.

 

There's nothing like to (knowingly) throw wrong guesses.

Edited May 16, 2021 by ZachariasX

[Holtzauge]

Sorry: Forgot to add that K4 is at 1.98 ata and P-51 at 75". Means you get another go @ZachariasX!

[ZachariasX]

9 minutes ago, Holtzauge said:

Sorry: Forgot to add that K4 is at 1.98 ata and P-51 at 75". Means you get another go @ZachariasX!

Then I see them evenly. Or maybe... just to pick a winner:

 

Mustang: 25 sec.

109K4: 24 sec.

[JtD]

If your Mustang comes with the V1650-7, this is getting a little above full throttle height for even 67" boost as speed goes down, so it's not more than 1700hp. The 1.98ata should still produce near 2000hp. Now 5g are not going to last forever, but I'd wager the 300 extra ponies will pull this contest to the K-4 side, no matter aerodynamic qualities. It can maintain the 5g longer. The K-4 will probably stall out at a higher speed than the P-51, though.

[ZachariasX]

1 hour ago, JtD said:

I'd wager the 300 extra ponies will pull this contest to the K-4 side, no matter aerodynamic qualities.

You are most likely right. However, my eyes were on this:

The P-51 foil gets more efficient at high speeds. Now as drag grows to the cube, feeble engine power however only linear, I should like to see that the entering of the turn braking the 109 that much faster than the P-51, that the higher power loading cannot offset this below 500 km/h. As the kinetic energy grows to the square vs airspeed, this should hurt the aircrafts momentum even further as disproportionally more energy is lost faster, hence my speculation that all is lost for the 109 above 500 km/h.

 

All this mainly because I sense a Swedish trick question in @Holtzauge's challenge, I wouldn't be so bold otherwise. Then again, gut feeling is bad advice.

 

[Holtzauge]

@ZachariasX and @JtD pls check inbox: Based on the forum level of interest I have moved this question to PM’s.

Edited May 17, 2021 by Holtzauge

[Aurora_Stealth]

18 hours ago, ZachariasX said:

You are most likely right. However, my eyes were on this:

The P-51 foil gets more efficient at high speeds. Now as drag grows to the cube, feeble engine power however only linear, I should like to see that the entering of the turn braking the 109 that much faster than the P-51, that the higher power loading cannot offset this below 500 km/h. As the kinetic energy grows to the square vs airspeed, this should hurt the aircrafts momentum even further as disproportionally more energy is lost faster, hence my speculation that all is lost for the 109 above 500 km/h.

 

All this mainly because I sense a Swedish trick question in @Holtzauge's challenge, I wouldn't be so bold otherwise. Then again, gut feeling is bad advice.

 

Just speaking my mind here about what I'm seeing, while you discuss between yourselves via PM...

 

That graph assumes 1.8 ATA, we know the equivalent of 75" boost (P-51) is 1.98 ATA for the Bf 109 K-4.

 

If we assume Holtzauge's statement around the increased power moving the line to the right, then I'd assume it to have an even bigger advantage than shown on this chart when using 1.98 ATA.

 

I'm referring to speeds roughly below 300mph (what I was trying to get at)... which is around where the P-51 on that graph begins to lose out (even comparatively when Bf 109 is using the lower 1.8 ATA).

 

I agree though, at higher speeds the aerodynamics plays a bigger part... helping the P-51 to claw back the advantage.

 

Please correct me if I'm missing something here.

 

Cheers,

[ZachariasX]

1 hour ago, Aurora_Stealth said:

If we assume Holtzauge's statement around the increased power moving the line to the right, then I'd assume it to have an even bigger advantage than shown on this chart when using 1.98 ATA.

Yes, absolutely. 2000 hp come handy by all means.

[HR_Zunzun]

2 hours ago, Holtzauge said:

@ZachariasX and @JtD pls check inbox: Based on the forum level of interest I have moved this question to PM’s.

 

Why move this to a private forum?

I do not have enough understanding level to participate in this particular conversation but sure enough like to read you all and learn more about flight dynamics.

[ZachariasX]

9 minutes ago, HR_Zunzun said:

Why move this to a private forum?

I'm sure he'll tall his results at some point soon, that I'm sure. It is for us to throw some numbers and have fun.

 

I mean you can try the experiment in the sim and see what you get. Always do the autumn maps for such, they have standard atmosphere.

[HR_Zunzun]

4 minutes ago, ZachariasX said:

I'm sure he'll tall his results at some point soon, that I'm sure. It is for us to throw some numbers and have fun.

 

I mean you can try the experiment in the sim and see what you get. Always do the autumn maps for such, they have standard atmosphere.

Ah, ok then. Thanks.

[Bremspropeller]

[Puts on salesman attire]

 

Ladies and gentlemen, meet the best turning fighter of the three:

 

The Fw 190D-9!*

 

___

*Instantaneous turn between 475 and 575kph - mileage may vary.

 

======================================================================================================================

 

 

Holtzauge, would you mind doing the chart for a slightly more realistic setting? Say 400l for the P-51 and 50% fuel for the german fighters. And then again for the analgoue amount of fuel (50% in german fighters) in the P-51?

 

That should give us a range of overall pictures. I would be surprised if it's grossly different, though.

Edited May 18, 2021 by Bremspropeller

[ZachariasX]

59 minutes ago, Bremspropeller said:

meet the best turning fighter of the three:

Pah. It will never be the "best turning fighter of hearts".

[Holtzauge]

5 hours ago, Bremspropeller said:

[Puts on salesman attire]

 

Ladies and gentlemen, meet the best turning fighter of the three:

 

The Fw 190D-9!*

 

___

*Instantaneous turn between 475 and 575kph - mileage may vary.

 

======================================================================================================================

 

 

Holtzauge, would you mind doing the chart for a slightly more realistic setting? Say 400l for the P-51 and 50% fuel for the german fighters. And then again for the analgoue amount of fuel (50% in german fighters) in the P-51?

 

That should give us a range of overall pictures. I would be surprised if it's grossly different, though.

 

SAAB should have hired you to sell the Viggen fighter @Bremspropeller: Ladies and gentlemen, meet the world's shortest landing jet fighter! Turn rate? Top speed? Range? Who cares about that when you can land in your own backyard!

 

On a more serious note: The idea behind the 400 l in both aircraft is to compare for roughly the same radius of action. OTOH they may have significantly different cruise speeds as well so what would be fair? I do know the German direct injection is probably a bit more fuel efficient so you could perhaps knock of a few liters in the German fighters but penalizing one plane for good range? Not on my watch!

[Bremspropeller]

The 400l figure is fine, but as badatflyski pointed out, it would be a little more realistic to compare all aircraft at a comparable mission fuel-state.

 

That would be roughly 50% fuel for all of them - with the P-51 having a longer commute.

And hence in order not to penalize the P-51, run the same equation again for a P-51 at comparable fuel remaining to the Fw 190 and Bf 109 at 50% fuel - let's say 190kg.

 

19 minutes ago, Holtzauge said:

SAAB should have hired you to sell the Viggen fighter

 

Unfortunately, I don't think I can quite compare with Tony Scott...

[Requiem]

For what it's worth, I've tested the P-51 at 150 Octane and the Bf 109 K-4 DB (I didn't think the DC is used often enough to justify testing that version) extensively in Il-2 by pulling the flight data directly from Il-2's telemetry export feature while doing the in-flight testing, but I combined this data against separate opponents which I also tested for my EM videos. After seeing this thread I've combined the P-51 and Bf 109 data together to show here if you wanted a look. My charts are generated by plugging that data into a Excel spreadsheet I created, so just keep in mind my charts are not generated with a computer simulation like Holtzauge's would be.

 

If you wanted results at 15,000 and 25,000ft it would take a hot minute as I have the data but need to reconfigure the graphing.

 

[Holtzauge]

41 minutes ago, Requiem said:

For what it's worth, I've tested the P-51 at 150 Octane and the Bf 109 K-4 DB (I didn't think the DC is used often enough to justify testing that version) extensively in Il-2 by pulling the flight data directly from Il-2's telemetry export feature while doing the in-flight testing, but I combined this data against separate opponents which I also tested for my EM videos. After seeing this thread I've combined the P-51 and Bf 109 data together to show here if you wanted a look. My charts are generated by plugging that data into a Excel spreadsheet I created, so just keep in mind my charts are not generated with a computer simulation like Holtzauge's would be.

 

If you wanted results at 15,000 and 25,000ft it would take a hot minute as I have the data but need to reconfigure the graphing.

 

 

Great, thanks for collecting this data @Requiem! As I understand it this testing was done in-game with 50% fuel for both meaning the P-51 is carrying roughly 327 l and the K4 200 l ?

 

If I run that in the simulations with those resulting weights and assuming the P-51 at 75" boost and the K4 with B4 fuel and MW50 at 1.8 ata at SL 15 deg C I get:

 

Me-109 K4 best sustained turn rate 20.5 deg/s at 305 Km/h

 

P-51D best sustained turn rate 19.5 deg/s at 285 Km/h

 

So basically the same results as in-game. Also nice that both in-game and in the simulations the relative performance is maintained, i.e. the K4 being slightly better.

 

Finally, the difference between the results are within any reasonable margin of error and again shows what a great simulator BoX is: I mean, I have the luxury of waiting a few seconds while the simulation converges while BoX is doing all this in real time with basically no delay.