109 sustained turn performance

[Floppy_Sock]

10 hours ago, Panthera said:

 

Might have to wait until the K-4's engine power is back Floppy, or you can try the stable version.

 

My results are 3.6-3.7 G's sustained at 200 kts TAS (370 km/h) for the K-4 in DCS (before the cockpit shake/power loss bug), full fuel (400 L), sea level. In IL-2 it was 3.3 G's, same conditions. Also don't forget to test the P-51 in both sims as well.

 

I'll redo my tests once the aircraft bugs have been fixed, which will probably be soon.

 

PS: To keep things simple please stick with 400 L fuel, so we're testing the same weights.

 

 

 

With all due respect @Panthera, did you even parse the data? Maybe you're not familiar with the format?

 

 

I have added a few contours to the curve to illustrate your condition precisely. The curves originating from the top left and curing down to the right are level sets (contours of constant value) of g. I have added a 3.6g contour in light orange and 3.3g in grey. It shows precisely the data point you describe. Furthermore, the bf109 in the same configuration in IL2 has very similar performance at that speed. The difference is within measurement error but we can assume it performs slightly worse. Maybe .1g worse? 

[Aurora_Stealth]

2 hours ago, Panthera said:

 

That is because he is using a similar lift coefficient for both, 1.4 for the P-51 and 1.43 for the 109. 

 

I am of the opinion that the 109 has a higher lift coefficient than this however, albeit the difference should be largest power on and at dogfighting speeds. 

 

If you ask me this also ties best with what Skip Holm, Mark Hanna and Dave Southwood have mentioned when comparing these two aircraft, that is the 109 is a much better turning aircraft at slow speeds. Something that wouldn't make sense to say if they were close in this respect.

 

 

I see, yeah that muddies the water completely - and I do agree. We know the laminar flow wing is poor at creating lift per square metre due to the inherent design principle (its a very thin aerofoil profile by design to minimise drag, which comes at the cost of lift production).

 

As combat will be with power-on, we need the power-on number for calculations to be valid. Not sure where we can get it.

 

36 minutes ago, -=PHX=-SuperEtendard said:

About the atmospheric conditions, a good map to test standard atmosphere is Kuban Autumn, which has 15ºC at sea level, and you can fly at sea level in the Black Sea.

The Summer maps have 25ºC at sea level, and the winter maps around -20ºC

 

Cheers Etendard, good info.

 

31 minutes ago, Floppy_Sock said:

 

With all due respect @Panthera, did you even parse the data? Maybe you're not familiar with the format?

 

 

I have added a few contours to the curve to illustrate your condition precisely. The curves originating from the top left and curing down to the right are level sets (contours of constant value) of g. I have added a 3.6g contour in light orange and 3.3g in grey. It shows precisely the data point you describe. Furthermore, the bf109 in the same configuration in IL2 has very similar performance at that speed. The difference is within measurement error but we can assume it performs slightly worse. Maybe .1g worse? 

 

Thanks for taking the time to make this chart Floppy, sorry to bother you again (at some point) could you do the same with the P-51 D in both games so we can see the differential between the two aircraft? - it looks to me like the Bf 109 K-4 closely aligns when comparing IL2 to DCS from your data but it could just mean that the differential is coming from the '51 FM's end and not the K-4 we're comparing it to.

 

It's once again reassuring to see the data between the two aligns for the K-4 however and I thank you for that.

 

I'm a little concerned about the issue mentioned with the engine performance though, and Panthera was able to get a larger variation in G's.

 

Anyway, thanks to all who are contributing.

[Floppy_Sock]

1 hour ago, Aurora_Stealth said:

 

I see, yeah that muddies the water completely - and I do agree. We know the laminar flow wing is poor at creating lift per square metre due to the inherent design principle (its a very thin aerofoil profile by design to minimise drag, which comes at the cost of lift production).

 

As combat will be with power-on, we need the power-on number for calculations to be valid. Not sure where we can get it.

 

 

Cheers Etendard, good info.

 

 

Thanks for taking the time to make this chart Floppy, sorry to bother you again (at some point) could you do the same with the P-51 D in both games so we can see the differential between the two aircraft? - it looks to me like the Bf 109 K-4 closely aligns when comparing IL2 to DCS from your data but it could just mean that the differential is coming from the '51 FM's end and not the K-4 we're comparing it to.

 

It's once again reassuring to see the data between the two aligns for the K-4 however and I thank you for that.

 

I'm a little concerned about the issue mentioned with the engine performance though, and Panthera was able to get a larger variation in G's.

 

Anyway, thanks to all who are contributing.

 

I think I'm still not being clear enough.

 

Panthera's condition, if I understand him correctly, is approximately 200 knots TAS, 3.6-3.7 G. 

 

If you follow the 370kmh (200 kts) line up until it crosses the 3.6g line (light orange), you will see that in the tests with the DCS 109, there lies a cluster of points at that location indicating that the current DCS bird can achieve said condition. Furthermore, the IL2 109 data is quite close and as I mentioned above, since I cannot be as precise in IL2 since all the telemetry is not available to calculate specific excess power in real time, there will be some measurement error associated with me having to record speeds by hand. 

 

The 370kmh line is indicated in yellow, the POI is circled in black for clarity. 

 

 

 

Please note that the DCS telemetry data is vast and detailed. I am VERY confident in my results from DCS as I can read telemetry from the game at 60hz and then filter it to find the conditions where p_s = 0 +- 0.1. Those are the clusters of points you see in green. 

 

If it is true that the DCS 109 engine is suffering from reduced power in the current beta build, then the 109 should perform better than 3.6g @ 200kts @SL. 

 

When I have some time I will run the same tests with the DCS P51. 

Edited August 24, 2020 by Floppy_Sock

[Holtzauge]

1 hour ago, Aurora_Stealth said:

I see, yeah that muddies the water completely - and I do agree. We know the laminar flow wing is poor at creating lift per square metre due to the inherent design principle (its a very thin aerofoil profile by design to minimise drag, which comes at the cost of lift production).

 

As combat will be with power-on, we need the power-on number for calculations to be valid. Not sure where we can get it.

 

No, what muddies the waters is unsupported speculation and generalizations about how laminar profiles work and Skip Whatsisname quotes and people not reading reports: I can quote Erwin Leykauf for you saying he can out turn Spitfires in his 109 so now the 109 out turns Spitfires as well?

 

I already explained why I use the Clmax data I do for the Mustang: I use two NACA reports to lean on: NACA Report 829 and NACA report TN 1044 that BOTH give a Clmax in the order of 1.4 for the Mustang in service condition which is also what I use.

 

Excuse me a while. I have to go watch the BRIO flic again.

[Panthera]

15 hours ago, Aurora_Stealth said:

I see, yeah that muddies the water completely - and I do agree. We know the laminar flow wing is poor at creating lift per square metre due to the inherent design principle (its a very thin aerofoil profile by design to minimise drag, which comes at the cost of lift production).

 

Well the P-51's wing isn't actually thin, it's pretty normal with a ~16% root thickness, so that's not an issue. But the sharp(er) leading edge does cause some issues with lift production at the normal combat speeds of propeller driven fighters, as is evident in the direct comparison between the F6F & P-51B at high altitude in the TN1044 report. Infact what's striking is that the F6F has a higher Clmax at mach 0.3 at high altitude than the P-51B does at the same mach number down low.

 

In other words a Clmax of 1.4 for the P-51 is not unlikely, esp. not at very low speeds where it's proven. The real difference is at normal dogfighting speeds, esp. around 0.25-0.4 mach where the conventional airfoils have a noticable advantage according to TN1044.

 

 

Quote

As combat will be with power-on, we need the power-on number for calculations to be valid. Not sure where we can get it.

 

Indeed the 109's main advantage should be the slats allowing for a higher overall lift to be produced in the power on condition vs using washout, as with outboard slats the outer wing section is now capable of reaching the same AoA (and more), without stalling, as the inner section energized via propwash. Where'as with washout the AoA of the outer section is instead lowered relative to the inboard section, and usually only by a few degrees, in order to keep it flying and delay its stall, but this lower AoA also means lower lift generated in that region. 

 

Problem is as you say that we don't have any concrete numbers to tell us exactly how big of a difference the slats will make here, as we don't have figures from Messerschmitt on this, and the only Cl figures we have are apparently for a prototype with shorter wings and without slats, where the average Clmax was 1.43. 

 

14 hours ago, Floppy_Sock said:

Panthera's condition, if I understand him correctly, is approximately 200 knots TAS, 3.6-3.7 G. 

 

Yes, 200 kts TAS (370 km/h), at sea level, with 400 L of fuel.

 

In IL2 I am only able to reach 3.3 G's sustained here under the same conditions, using the ingame G meter. Where'as in DCS I was able to achieve 3.6-3.7 G's before the engine bug.

 

 

Edited August 25, 2020 by Panthera

[Aurora_Stealth]

On 8/24/2020 at 8:42 PM, Holtzauge said:

 

No, what muddies the waters is unsupported speculation and generalizations about how laminar profiles work and Skip Whatsisname quotes and people not reading reports: I can quote Erwin Leykauf for you saying he can out turn Spitfires in his 109 so now the 109 out turns Spitfires as well?

 

I already explained why I use the Clmax data I do for the Mustang: I use two NACA reports to lean on: NACA Report 829 and NACA report TN 1044 that BOTH give a Clmax in the order of 1.4 for the Mustang in service condition which is also what I use.

 

Excuse me a while. I have to go watch the BRIO flic again.

 

I apologise, flat profile are the wrong words to use. Sharp on the leading edge, disadvantageous to other conventional aerofoils in lift production and distribution.

 

Well hold on - I haven't said it must be specifically the CLmax of the P-51 that is incorrect, I said that comparatively we'd expect the (not entirely practical) laminar flow wing to be significantly inferior at lift production at slower speeds... considering the Bf 109 has slats to assist. What I said was there could be an issue somewhere with the P-51 D's flight model seeing as the disparity is significant with modern pilot's accounts, and this cannot be seen in the Bf 109's data - which doesn't make sense. I do not write the code for this sim and I'm not claiming to be an aerodynamicist or a technocrat who has every graph and piece of data to hand but I do have enough knowledge to see there is a conflict between what is being said and what is occurring in-game. I have a job, a limited amount of time to dedicate and I'm transparent about that.

 

That first NACA report 829 indicates that a wing using slats would be able to reach a much higher CLmax, in one case shown as high as 1.8... yet you're telling me that the Bf 109 wing is only able to achieve 1.43 CLmax compared versus 1.4 of an aircraft that doesn't? really? where is the effect of the slats on increasing the CLmax in that case, seems a little small considering the differential described in that report. Granted the report is not using the same 2R1 profile of the Bf 109, but still - there should be a significant improvement there.

 

A differential of 0.03 seems suspiciously low considering the differences measured by NACA between a slatted and non-slatted wing.

 

Also, saying 90% of the world's most experienced pilots who have flown these aircraft are speculating when they are the one's who have flown them, implying that you know more about the aircraft, their operation and performance than they do is pretty slanderous. They have first hand experience with these aircraft... with the opportunity to compare them side-by-side and without most of the other variables and factors in 1944 / 1945 e.g. fitting with under-wing gondolas, minimal pilot flying hours and situational disparities being vaguely described.

 

I did mention earlier the Spitfire's performance being superior in a turn but that was conveniently forgotten again it seems - attributable to its much larger wing area and lower wing loading.

 

The Bf 109 G-10 and Buchon which are operated use almost exactly the same wing profile to the K-4. The differences in weight and drag between the K-4 and these models is also comparable, and their conclusions about both of those aircraft is extremely clear. At altitudes where these aircraft are typically operated (below 10,000 feet) the consensus is its very much superior in manoeuvring to the P-51 D at speeds under 300mph.

 

I appreciate I don't have all the answers, that's why we're discussing it... but there is a disparity here... which is why it needs to be looked at deeper.

 

Additionally, I have requested further information from all the known operators of the aircraft including Flugmuseum Messerschmitt which is operated under Airbus, will let you know what I hear back.

 

Cheers,

Edited August 25, 2020 by Aurora_Stealth

[ZachariasX]

7 hours ago, Aurora_Stealth said:

What I said was there could be an issue somewhere with the P-51 D's flight model seeing as the disparity is significant with modern pilot's accounts

Don't you ever take pilot accounts from then and now at face value according to the same standards. Those accounts reflect an impression of what people actually did with those aircraft and this in context to what they were used to as alternatives. Back then, they flew Miles Magister, not a Cirrus. Today is a very, very different world and those planes are flown in a very, very different way according to very, very different standards.

 

Those warbirds are fine and sound aircraft, but according to todays standards, they are grotesquely dangerous to operate, as they do have some unforgiving characteristics that people didn't much care for back then. Your life was really cheap back then. Also, If you can't really imagine how it should be, why would you ground your aircraft/air force until they behave "as they should"? The very little total hours of peacetime operation of these aircraft produced a lot of dead and injured people, all of which were far above average pilots. Mark Hanna died flying the 109. That is how much lift you get there if push comes to shove.

 

Anyone telling you the Spitfire/109/etc. is a fine aircraft is right. I say that as well. BUT. It is simply an unacceptable proposition for today, even if you got a new build, including new engine. If people are having a lot of fun with that aircraft - boy, you can! - then they will give glowing reports about it. But if it is the tool to just go out every day and put your life on the line, killing for not getting killed, that tune changes. An airshow pilot telling you how happy he is with his ride just goofing around tells you NOTHING that you can use in hard numbers regarding the potential of the aircraft back then. It's just another dude having fun with a vastly overpowered aircraft. Until he dies in that aircraft. But then you will not get more than an accident report in lieu of a "modern pilot's account". Read them too and put them on the stack of "modern pilot reports" to even out your perspective.

[Aurora_Stealth]

I've read the report several times and that is a poor argument, especially as I've personally witnessed two P-51's crashing and conducting emergency landings due to mechanical failure in recent years during the same airshow at Duxford. There's also the incident where I watched a P-51 pilot bail out after colliding with another aircraft. You can also have a look through the extensive list of incidents and accidents involving P-51's, there's a long list and plenty of pilots have died in them as well.

 

Neither of these aircraft have modern day standards of reliability and control systems and all people are subject to making errors which is why mistakes are made with all these warbirds. We're not discussing that in this thread however, we're discussing sustained turning performance.

 

Please stay on-topic.

Edited August 26, 2020 by Aurora_Stealth

[ZachariasX]

1 minute ago, Aurora_Stealth said:

I've read the report several times and that is a poor argument, especially as [words]

Wot? You just made my argument that these birds are dangerous to operate. There are  many more flyable P-51 today than 109, hence they will produce more bent metal. The few 109 that are flyable crash a great many times, enough for not being considered airworthy according to todays standards.

 

This is not a question of reliability. It is a question of handling. Sure, if something is broken, there's problems. But you don't need broken things to die in such an aircraft.

 

4 minutes ago, Aurora_Stealth said:

Please stay on-topic.

There is absolutely no topic to this discussion besides the BRIO engine. We have seen that people who can fly these sim aircraft basically get identical performance figures as Panthera initially speculated when I asked him where he wants to see the performance differences. They even closely match what you get in the other sim. Now it might be the case that you do not reach these performance figures. Well, keep trying.

 

That some here constantly keep ad-hoc inflating their great expectations about "the slats" keep the thread going. Nothing of substance that has been posted so far disputes the originally assumed ~1 sec lead of the 109 in best turn time. But what is clear is that it is much harder in the 109 to reach these figures, this is why you can't get them, but you can do good times in the Mustang. It is probably realistic too, making these aircraft very evenly matched in the real world.

 

The only thing that is left is wild ad-hoc speculation about "slats" that do wonders. Well, they don't keep you from dying in that aircraft. Ask Mark Hanna.

[Holtzauge]

12 hours ago, Aurora_Stealth said:

 

I apologise, flat profile are the wrong words to use. Sharp on the leading edge, disadvantageous to other conventional aerofoils in lift production and distribution.

 

Well hold on - I haven't said it must be specifically the CLmax of the P-51 that is incorrect, I said that comparatively we'd expect the (not entirely practical) laminar flow wing to be significantly inferior at lift production at slower speeds... considering the Bf 109 has slats to assist. What I said was there could be an issue somewhere with the P-51 D's flight model seeing as the disparity is significant with modern pilot's accounts, and this cannot be seen in the Bf 109's data - which doesn't make sense. I do not write the code for this sim and I'm not claiming to be an aerodynamicist or a technocrat who has every graph and piece of data to hand but I do have enough knowledge to see there is a conflict between what is being said and what is occurring in-game. I have a job, a limited amount of time to dedicate and I'm transparent about that.

 

That first NACA report 829 indicates that a wing using slats would be able to reach a much higher CLmax, in one case shown as high as 1.8... yet you're telling me that the Bf 109 wing is only able to achieve 1.43 CLmax compared versus 1.4 of an aircraft that doesn't? really? where is the effect of the slats on increasing the CLmax in that case, seems a little small considering the differential described in that report. Granted the report is not using the same 2R1 profile of the Bf 109, but still - there should be a significant improvement there.

 

A differential of 0.03 seems suspiciously low considering the differences measured by NACA between a slatted and non-slatted wing.

 

Also, saying 90% of the world's most experienced pilots who have flown these aircraft are speculating when they are the one's who have flown them, implying that you know more about the aircraft, their operation and performance than they do is pretty slanderous. They have first hand experience with these aircraft... with the opportunity to compare them side-by-side and without most of the other variables and factors in 1944 / 1945 e.g. fitting with under-wing gondolas, minimal pilot flying hours and situational disparities being vaguely described.

 

I did mention earlier the Spitfire's performance being superior in a turn but that was conveniently forgotten again it seems - attributable to its much larger wing area and lower wing loading.

 

The Bf 109 G-10 and Buchon which are operated use almost exactly the same wing profile to the K-4. The differences in weight and drag between the K-4 and these models is also comparable, and their conclusions about both of those aircraft is extremely clear. At altitudes where these aircraft are typically operated (below 10,000 feet) the consensus is its very much superior in manoeuvring to the P-51 D at speeds under 300mph.

 

I appreciate I don't have all the answers, that's why we're discussing it... but there is a disparity here... which is why it needs to be looked at deeper.

 

Additionally, I have requested further information from all the known operators of the aircraft including Flugmuseum Messerschmitt which is operated under Airbus, will let you know what I hear back.

 

Cheers,

Never put someone on ignore before but since you via PM added clear malicious intent to discredit on top of the slander accusation you've earned it.

[Panthera]

2 hours ago, ZachariasX said:

here is absolutely no topic to this discussion besides the BRIO engine. We have seen that people who can fly these sim aircraft basically get identical performance figures as Panthera initially speculated when I asked him where he wants to see the performance differences. They even closely match what you get in the other sim. Now it might be the case that you do not reach these performance figures. Well, keep trying.

 

That's not true however as the conditions weren't the same.

 

But if you are able to sustain 3.6-3.7 G's @ 370 km/h TAS, with full fuel (400 L), then please post a video showing it, because I can't nomatter how hard I try and this is not a drill which is difficult to perform. The best I can get under those conditions is 3.3 G's using the ingame G meter, which is some 0.3 to 0.4 G's lower than in DCS.

 

Also worthy of note is that the P-51 achieves 3.0 G's sustained under those very same conditions in DCS. Compare that with IL2.

[Aurora_Stealth]

For the record... and for full transparency on my end, Holtzauge - sending a PM to me to tell me of your credentials and expecting that it entitles you a greater position of authority than the actual pilots and engineers who operate these aircraft is not acceptable to me. You and others here have implied this several times and tried to dismiss their point of view. Neither do I expect anyone to be taken at face value without a form of verification - but if the majority of operators and pilots all agree then this adds significant weight to their position.

 

If this is the first time someone has held you accountable, then let's hope it's not going to be the last for the sake of other people. I am equally not just going to take (your) data at face value just because you have a degree - you said yourself you made mistakes in the calculations (we all do and I recognised this in my response). Many people have accreditation (including myself) but that doesn't entitle me or anyone to a special unaccountable status.

 

As I said, denying fair representation from the pilots who fly and operate the aircraft is a very devaluing point of view to hold, for example DCS spends time to understand and verify information from pilots to inform their flight modelling. I find it hard to believe IL-2 doesn't. I understand and respect the development priorities of IL-2 and this is a slightly different product. That shouldn't mean we dismiss insightful information. We need their insight to complete the picture where data on this particular Bf 109 variant (K-4) is lacking or insufficient.

 

The reason I am very strongly protecting this important source of information, is because we do not have many documents left in existence available for the Bf 109 K including on its turning performance and we need a basis on which to verify information and data claims - especially as the current FM is contradicted by real pilots in very comparable airframes.

-----

 

On 8/26/2020 at 12:17 PM, ZachariasX said:

Wot? You just made my argument that these birds are dangerous to operate. There are  many more flyable P-51 today than 109, hence they will produce more bent metal. The few 109 that are flyable crash a great many times, enough for not being considered airworthy according to todays standards.

 

This is not a question of reliability. It is a question of handling. Sure, if something is broken, there's problems. But you don't need broken things to die in such an aircraft.

 

There is absolutely no topic to this discussion besides the BRIO engine. We have seen that people who can fly these sim aircraft basically get identical performance figures as Panthera initially speculated when I asked him where he wants to see the performance differences. They even closely match what you get in the other sim. Now it might be the case that you do not reach these performance figures. Well, keep trying.

 

That some here constantly keep ad-hoc inflating their great expectations about "the slats" keep the thread going. Nothing of substance that has been posted so far disputes the originally assumed ~1 sec lead of the 109 in best turn time. But what is clear is that it is much harder in the 109 to reach these figures, this is why you can't get them, but you can do good times in the Mustang. It is probably realistic too, making these aircraft very evenly matched in the real world.

 

The only thing that is left is wild ad-hoc speculation about "slats" that do wonders. Well, they don't keep you from dying in that aircraft. Ask Mark Hanna.

 

ZachariasX, no one has said that leading edge slats are magical devices; but they have been proven in NACA reports like the one Holtzauge referenced earlier to greatly increase CLmax by a very large proportion which has a definite improvement to the low speed characteristics of the aircraft and in various conditions including takeoff, landing and in turns. No one is claiming it is a delightful and easy aircraft to fly in handling terms per modern standards.

 

Yes, the Bf 109 is a demanding aircraft to fly - no question there - I'm not sure what that is meant to prove in this discussion on turning performance. Using the death of a pilot to justify your point of view is a pretty vulgar way of making a point. I'm not going to stoop to your level by listing all the deaths of P-51 pilots in the last ten years - I have more respect and they are good people lost forever.

 

Moving back to the topic of sustained turning performance...

 

22 hours ago, HomicideHank said:

Felt like I could get more out of the P-51 so I did some more testing. Turns out K-4 and P-51 are more evenly matched than I initially thought. Also added Spitfire IX +18 lbs.

P-51 67" 400L @280 km/h

SL:    18.8s | 2.6-2.8 G's sustained

1km: 20.1s | 2.6-2.7 G's sustained

 

Bf-109K-4 1.8ata 400L @280 km/h

SL:    18.7s | 2.7-2.8 G's sustained

1km: 20.5s | 2.6-2.7 G's sustained

 

Spitfire IX +18 lbs 386L @280 km/h

SL:    16.4s | 3.1-3.3 G's sustained

1km: 17.7s | 2.8-3.0 G's sustained

 

@HomicideHank, thank you very much for your efforts.

 

I do appreciate it, especially as we're in the middle of the working week.

 

That is an interesting result, if you come across anything else let us know.

 

We're all learning here... and people say there is nothing of substance to show or discuss lol.

 

Cheers again,

Edited August 27, 2020 by Aurora_Stealth

[Panthera]

 

Good stuff @HomicideHank, seems more inline with my results in IL2, albeit I get a little more out of the stang than you, and it confirms something is indeed off.

 

Now since the engine bug has just been fixed in DCS I did some more testing in there as well:

 

Sea level, 300 km/h TAS, 400 L fuel:

K-4 = 3.1-3.2 G's

P-51 = 2.7-2.8 G's

 

Sea level, 370 km/h TAS, 400 L fuel:

K-4 = 3.6 G's

P-51 = 3.0 G's

 

 

Also worthy of note, the engine torque experienced in DCS is much more pronounced than in IL2, making proper use of rudder in the turn at 300 km/h essential. 

 

 

Edited August 27, 2020 by Panthera

[Cpt_Siddy]

The data trends on turn times from this thread shows that the wing loading has non linear effect on performance in 109 series. Now bear in mind that i have no clue on whether it should be so or not. 

What i am stating is that in this sim, a modest weight increase worsens the 109's turn time despite large horsepower increase also trends up with weight. 

From 109-E to 109-K, weight increased less in percentages compared to available horsepower. Yet many say that E model was better turner. 

4 hours ago, HomicideHank said:

Added SL turn times for P-51 75", K-4DC, G-14, Tempest at +9 and +11 lbs.

 

Out of curiosity, can you also do Spit V?

 

It has different weight but similar wing to Spit IX, but less horsepower, how does it stack up against its more powerful sibling? 

[JtD]

On 8/26/2020 at 4:32 PM, HomicideHank said:

 

Bf-109K-4 1.8ata 400L @ 280 km/h

SL:    18.7s | 2.7-2.8 G's sustained

1km: 20.5s | 2.6-2.7 G's sustained

 

Bf-109K-4 1.98ata 400L @ 280 km/h

SL:    18.7s | 2.7-2.8 G's sustained 

If the Bf109K-4 does indeed not gain anything from the extra power, it is worth looking into airscrew efficiency, as suggested earlier. Unless it stalls at this speed.

 

Thank you for doing these tests and sharing your findings.

Edited August 27, 2020 by JtD

[LColony_Kong]

3 hours ago, JtD said:

If the Bf109K-4 does indeed not gain anything from the extra power, it is worth looking into airscrew efficiency, as suggested earlier. Unless it stalls at this speed.

 

Thank you for doing these tests and sharing your findings.

Its not gaining anything because the tests are at the same speed. That is the reason the results are different, and the reason the K-4 DC engine isn't getting anything from its extra power. Not sure why people keep doing sustained turn tests at the same speed between planes and different configurations, its completely pointless and meaningless.

[LColony_Kong]

3 hours ago, HomicideHank said:

Yeah I thought about doing more testing at different speeds but my hand hurts :(. You can continue from here

Dont do different speeds. Your turn on the edge of a stall until the plane settles to a sustained velocity and doesnt change. Randomly picking speeds gets us nowhere.

 

I just tested the K-4 50% fuel 1.98 ata.

 

19.9 degress per second for an 18.09 second turn. This is vs 18.65 seconds for the 1.8ata k4. 2.7G @265kph.

[Roland_HUNter]

Information about slats

- The 109 included the leading edge slats starting with the very first versions which were powered by Kestrel engines, and it is quite funny that the very first version was equipped with a Rolls-Royce engine. It is fascinating that these slats were built under licence of the British Handley-Page. Up to the start of the war Germans paid license fees for every Messerschmitt to H-P. Also the oval wing employed in the Spitfire was originally conceived by Heinkel. Heinkel and Supermarine had a lot of co-operation before the war. Heinkel tried to buy a licence for the Merlin engine in Germany.
- Lower wingloading does not automatically equals better turn rate, it is more a factor of actual liftloading. Depending on the wing`s design, it may develop more or less lift. As it stands, the P-51D had laminar flow wings, which lowered the drag, but this came at the cost of lower lift, especially under high G loads. The 109 had a conventional wing and was equipped with automatic leading edge slats. These opened out at low speed or at high speed under high G loads, and restored to airflow (=lift) which would have been long separated otherwise due to turbulance. That`s why it become so common on modern jets. This seems to be supported by the AFDU`s test, where they pitted the higher wingloading FW 190A vs. P-51B, yet they found their turning performance basically identical. I`d like to add that 109s were generally found to be the better turning machines in all German and Soviet tests vs. 190s. Also, stall characteristics of the 109 were very gentle and forgiving with plenty of warning, as opposed to the P-51. This also helped the pilots to push their aircraft to the limits of stall.


- At least in case of a Gustaf (which is the same as F-4, including the slat mechanism) the slats tend to droop out of the leading edge when the plane stands on ground. They however move in by pressing the leading edge with one finger, extremely easily. After having been pushed in, they either stay in or slowly glide out again. This is very sensitive to the plane's actual angle on ground, and may be affected even by the relative tire pressures of main and tail landing gear wheels. But in flight they bang in and out driven by the aerodynamic forces. There are no springs or such, both the movement out and movement in are totally driven by aerodynamic forces. Those forces are controlled by the wing AoA, and there is no "deadband" in the function at any AoA. The operating function has very narrow transfer from stable position to an another. This means that in normal flight it should be almost impossible to control the AoA with such precision that the slats would slowly slide in or out. I have talked about this with several Bf 109 veterans and none of them has claimed gradual operation, they all explain their working as slamming in and out. On the other hand none of them has descibed the slat extension to be associated with any sudden increase of drag either. Which is as it should operate also theoretically. Slats extend up the range of AoA where the airflow stays attached to the wing. Withouth slats the wing would stall at certain AoA, the airflow turning turbulent at the same moment with sudden enormous increase in drag. With slats the airflow stays non-turbulent for some extra amount of AoA, and there should not be any "stepped" increase in drag when the slats deploy, only at the point where even the slats cannot prevent the wing entering a stall. - Pentti Kurkunen, enthusiast

Pilot comments

Me 109 E:
"I was particularly interested in the operation of the slats, the action of which gave rise to aileron snatching in any high-G manoeuvres such as loops or tigh turns so I did a series of stalls to check their functioning more accurately. The stall with the aircraft clean, with half fuel load and the engine throttled right back occurred at 105 MPH (168 km/h). This was preceded by elevator buffet and opening the slats about 20 mph (30 km/h) above the stall, these being accompanied by the unpleasant aileron snatching as the slats opened unevenly. The stall itself was fairly gentle with the nose dropping and the port wing simultaneously dropping about 10 degrees."
- Eric Brown
- The author writes about an "unpleasant" event. Nothing catastrophic! Surely all of the planes of that time had features, that were unpleasant, just as well as many planes today have. Curtiss Hawk 75 was surely unpleasant to fly with the rear fuselage fuel tank filled, as flying acrobatics could get you killed. P-51 was at least unpleasant with fuselage tanks filled.

Me 109 E:
"The Bf 109s also had leading edge slats. When the 109 was flown, advertently or inadvertently, too slow, the slats shot forward out of the wing, sometimes with a loud bang which could be heard above the noise of the engine. Many times the slats coming out frightenened young pilots when they flew the Bf 109 for the first time in combat. One often flew near the stalling speed in combat, not only when flying straight and level but especially when turning and climbing. Sometimes the slats would suddenly fly out with a bang as if one had been hit, especially when one had throttled back to bank steeply. Indeed many fresh young pilots thought they were pulling very tight turns even when the slats were still closed against the wing. For us, the more experienced pilots, real manoeuvring only started when the slats were out. For this reason it is possible to find pilots from that period (1940) who will tell you that the Spitfire turned better than the Bf 109. That is not true. I myself had many dogfights with Spitfires and I could always out-turn them.
One had to enter the turn correctly, then open up the engine. It was a matter of feel. When one noticed the speed becoming critical - the aircraft vibrated - one had to ease up a bit, then pull back again, so that in plan the best turn would have looked like an egg or a horizontal ellipse rather than a circle. In this way one could out-turn the Spitfire - and I shot down six of them doing it. This advantage to the Bf 109 soon changed when improved Spitfires were delivered."
- Erwin Leykauf, German fighter pilot, 33 victories. Source: Messerschmitt Bf109 ja Saksan Sotatalous by Hannu Valtonen; Hurricane & Messerschmitt, Chaz Bowyer and Armand Van Ishoven.

Me 109 E:
"And there I discovered the first thing you have to consider in a 109. The 109 had slots. The slot had a purpose to increase the lift during takeoff and landing. In the air automatically it's pressed to the main wing. And if you turn very roughly you got a chance, it's just by power, the wing, the forewing, comes out a little bit, and you snap. This happened to me. I released the stick immediately and it was ok then. "
- Major Gunther Rall in April 1943. German fighter ace, NATO general, Commander of the German Air Force. 275 victories. Source: Lecture by general Rall.

Me 109 E/F/G: - The plane had these wing slats and you mentioned they pop open uneven?
"Two meter slots on fore wings.  The reason was to increase the lift during low speed take off and landing.  To reduce the length of runway you need.  In the air, if you make rough turns, just by gravity, the outer slot might get out.  You can correct it immediately by release of stick, you know? Only little bit, psssssssht, its in, then its gone.  You have to know that.  And if you know it, you prevent it."
- Major Gunther Rall. German fighter ace, NATO general, Commander of the German Air Force. 275 victories. Source: Lecture by general Rall.

Me 109 G:
"- How often did the slats in the leading edge of the wing slam open without warning?
They were exteneded always suddenly but not unexpectedly. They did not operate in high speed but in low speed. One could make them go out and in by moving the stick back and forth. When turning one slat functioned ahead of the other one, but that did not affect the steering. In a battle situation one could pull a little more if the slats had come out. They had a positive effect of the slow speed handling characteristics of the Messerschmitt.
- Could the pilot control the leading edge slats?
No. The slats were extended when the speed decreased enough, you could feel when they were extended. "
- Kyösti Karhila, Finnish fighter ace. 32 victories. Source: Interview by Finnish Virtual Pilots Association.

Me 109 G:
"- In a battle, which was the case: did the pilot endure more than the Messerschmitt could do or vice versa?
 The fact is that when you pulled hard enough the wing leading edge slats slammed open. After that the pilot could not tighten the turn. The plane would have stalled. I don't know, I never tried to find out what the plane would do after that. I never heard anybody else saying that he would have banked so hard that the slats came out. I did that a few times, for example once over the Isthmus I tried to turn after an enemy, banking so hard that both slats came out, but I had to give up.
- How did the slats behave in such a situation, did they go in and out ?
 It depended on speed, if you pulled more,they came out, then back in
The slats came out completely, never half-way?
 I never came to watch them so intensely. You just knew they had come out, you could see them and feel that the lift increased pretty much.
- So the plane warned that now you are on the edge.
Yes, you knew the plane is about to spin."
- Antti Tani, Finnish fighter ace. 21,5 victories. Source: Interview by Finnish Virtual Pilots Association.

Me 109 F/G:
"- Did pilots like the slats on the wings of the 109?
Yes, pilots did like them, since it allowed them better positions in dogfights along with using the flaps. These slats would also deploy slightly when the a/c was reaching stall at higher altitudes showing the pilot how close they were to stalling.....this was also useful when you were drunk "
- Franz Stigler, German fighter ace. 28 victories. Interview of Franz Stigler.

Me 109 G:
"As CL max is reached the leading edge slats deploy - together if the ball is in the middle, slightly asymmetrically if you have any slip on. The aircraft delights in being pulled into hard manuevering turns at these slower speeds. As the slats pop out you feel a slight "notching" on the stick and you can pull more until the whole airframe is buffeting quite hard. A little more and you will drop a wing, but you have to be crass to do it unintentionally."
- Mark Hanna of the Old Flying Machine Company flying the OFMC Messerschmitt Bf 109 G (Spanish version).

Me 109 G:
"There was nothing special in landing the plane. It was heavy but the wing slats opened up when speed slowed down and helped flying in slow speed."
-Kullervo Joutseno, Finnish fighter pilot. Source: Hannu Valtonen, "Me 109 ja Saksan sotatalous" (Messerschmitt Bf 109 and the German war economy), ISBN 951-95688-7-5.

Me 109 G:
"It was beneficial to keep the throttle a little open when landing. This made the landings softer and almost all three-point landings were successful with this technique. During landings the leading edge slats were fully open. But there was no troubles in landing even with throttle at idle."
-Mikko Lallukka, Finnish fighter pilot. Source: Hannu Valtonen, "Me 109 ja Saksan sotatalous" (Messerschmitt Bf 109 and the German war economy), ISBN 951-95688-7-5.Source: Hannu Valtonen, "Messerschmitt Bf 109 and the German war economy"

Me 109 G:
"We didn't have time for acrobatics but we weren't forbidden from doing them, though. Snap roll was fast and easy, and the engine didn't cough as in older planes. Immelman turn was splendid when you tightened the stick a bit on the top. The automatic wing slats did their trick and you didn't need ailerons at all for straightening the plane."
-Otso Leskinen, Finnish fighter pilot. Source: Hannu Valtonen, "Me 109 ja Saksan sotatalous" (Messerschmitt Bf 109 and the German war economy), ISBN 951-95688-7-5.

"Unexperienced pilots hesitated to turn tight, bacause the plane shook violently when the slats deployed. I realised, though, that because of the slats the plane's stalling characteristics were much better than in comparable Allied planes that I got to fly. Even though you may doubt it, I knew it [Bf109] could manouver better in turnfight than LaGG, Yak or even Spitfire."
- Walter Wolfrum, German fighter ace. 137 victories.

Source:http://www.virtualpilots.fi/feature/articles/109myths/#slats

 

 

I don't want take part in the debate(I don't have enought knowledge in aerodynamics), just I copied the infos what I found.

[Cpt_Siddy]

1 hour ago, HomicideHank said:

Added

 

So the less powerful but no doubt lighter spit out turns is more powerful counterpart?  

This seems to point out the important role of a non linearity of wing loading. The added horsepower for the weight don't seem to be enough to offset the added weight for that extra horsepower, at least not for sustain turns.

 

I am sure the maximum speed and climb are another matter and benefit fore more horsies. 

[JtD]

9 hours ago, [TLC]MasterPooner said:

Its not gaining anything because the tests are at the same speed. That is the reason the results are different, and the reason the K-4 DC engine isn't getting anything from its extra power. Not sure why people keep doing sustained turn tests at the same speed between planes and different configurations, its completely pointless and meaningless.

 

An aircraft with more power will turn faster at the same speed, unless it is turning at stall speed with the low power configuration already. It may sound like rocket science around here, but it's really basic physics. 

[LColony_Kong]

3 hours ago, JtD said:

 

An aircraft with more power will turn faster at the same speed, unless it is turning at stall speed with the low power configuration already. It may sound like rocket science around here, but it's really basic physics. 

No it will not.

 

Two Bf-109s with different engines have identical lift drag etc. A plane with more power will turn tighter because it can increase G without losing speed. If they are turning at the same speed, at least one of the two planes is not max performing itself. And picking random sustained turn speeds is completely pointless in testing their relative max sustained turn rate.

 

 

 

Since two planes are identical in every respect except thrust, at any given speed they will have the same bank angle angle of attack etc. This means that unless the radial acceleration is changed, no change in turn radius or turn rate will occur. The plane with more power could afford to increase radial acceleration without losing speed, and thus turn radius would go down and turn rate go up by extension. So if both planes are turning at the speed with the same rate/radius/g, one or both is not performing at max.

 

and lo and behold:

 

"rocket science" indeed.

Edited August 28, 2020 by [TLC]MasterPooner

[JtD]

Ok, do the best sustained turn you can do in whatever plane you like, then reduce the throttle to say 80% and try to maintain it, while keeping speed constant. Good luck!

 

[nighthawk2174]

This is kind of a ridiculous argument this isn't even that hard of a concept... if you maintain the same speed between two of the exact same planes even with one having more power it will still get the same G-loading.   The difference is that the plane with more power has to reduce throttle to match the power output of the plane with less thrust should it want to match speeds and not continue to accelerate.   With more thrust you can pull harder while maintaining the same speed getting a higher G-loading and thus getting a better rate.

Edited August 28, 2020 by nighthawk2174

[LColony_Kong]

4 hours ago, JtD said:

Ok, do the best sustained turn you can do in whatever plane you like, then reduce the throttle to say 80% and try to maintain it, while keeping speed constant. Good luck!

Right so this is just dodging what I said.

 

4 hours ago, JtD said:

while keeping speed constant.

Lol.

[Holtzauge]

My understanding of how this works: For any plane keeping all other things the same the speed for best turn rate will increase if you add more power moving the right hand (power limited) curve of the doghouse chart up to the right. Conversely, if you keep the power the same and add wing area or increase Clmax this will move the left hand part of the doghouse chart curve up to the left, decreasing the speed for best turn rate.

 

In my simulations the speed for best turn rate for the Me-109K4 goes up by about 13 km/h when going from 1.8 ata to 1.98 ata.

 

[Aurora_Stealth]

9 hours ago, Holtzauge said:

My understanding of how this works: For any plane keeping all other things the same the speed for best turn rate will increase if you add more power moving the right hand (power limited) curve of the doghouse chart up to the right. Conversely, if you keep the power the same and add wing area or increase Clmax this will move the left hand part of the doghouse chart curve up to the left, decreasing the speed for best turn rate.

 

In my simulations the speed for best turn rate for the Me-109K4 goes up by about 13 km/h when going from 1.8 ata to 1.98 ata.

 

 

Spot on, completely agree. This is a very simple and elegant way of explaining it.

 

The Bf 109 has its CLmax extended to the left when the slats open during turns and high AoA's, its reasonable to suggest that it would out turn the P-51 at slower speeds considering power outputs are either similar or slightly superior to the Bf 109 (G-14 and K-4) at lower to medium altitudes.

 

At higher speeds and higher altitudes (above 25,000 feet) - where the P-51 can utilise its low drag design to best effect (at high speeds / mach no's) or its superior engine power from its two stage supercharger, it can over come the Bf 109.

 

This directly aligns with Bud Anderson and most of the other pilot accounts.

 

This is what we've essentially been trying to get at.

Edited August 28, 2020 by Aurora_Stealth

[LColony_Kong]

3 hours ago, Aurora_Stealth said:

The Bf 109 has its CLmax extended to the left when the slats open during turns and high AoA's, its reasonable to suggest that it would out turn the P-51 at slower speeds

Except its Clmax is virtually the same.

3 hours ago, Aurora_Stealth said:

This is what we've essentially been trying to get at.

This is an unusual statement to make, considering that not a single person in this thread has said the P-51 should out turn the 109. The debate has been regarding by how much, with both the game and @Holtzauge simulations showing that it isn't by all the much.

[Panthera]

24 minutes ago, [TLC]MasterPooner said:

Except its Clmax is virtually the same.

 

According to what source exactly? Do you have a source for the Clmax of the 109 & P-51 at dogfighting speeds, under G load, and power on? If so please share it.

 

Remember that a Clmax of 1.4 for the P-51 is at very low speeds and power off, where'as the advantage of conventional airfoils is in lift production under load at the typical flying speeds of prop jobs. It's two very different scenarios.

 

On the contrary available evidence suggests the Clmax of the 109 should be noticably higher than that of the P-51, power on, at the typical dogfighting speeds, and this is only further backed up by pilot testimony in regards to how these two aircraft compare under those conditions.

[LColony_Kong]

3 hours ago, Panthera said:

According to what source exactly? Do you have a source for the Clmax of the 109 & P-51 at dogfighting speeds, under G load, and power on? If so please share it.

 

Remember that a Clmax of 1.4 for the P-51 is at very low speeds and power off, where'as the advantage of conventional airfoils is in lift production under load at the typical flying speeds of prop jobs. It's two very different scenarios.

 

On the contrary available evidence suggests the Clmax of the 109 should be noticably higher than that of the P-51, power on, at the typical dogfighting speeds, and this is only further backed up by pilot testimony in regards to how these two aircraft compare under those conditions.

Lol we have literally gone over this in this thread and others like a dozen times now.

[Panthera]

40 minutes ago, [TLC]MasterPooner said:

Lol we have literally gone over this in this thread and others like a dozen times now.

 

No, no evidence to support you claim has been presented.

 

Even Holtzauge's graphs, using a similar Clmax (which I disagree with), show a 1+ sec advantage in the K-4's favour with 1.8ata vs 75" Hg and same fuel load. Which is the exact reverse of the representation in IL2. So I honestly don't know why it is you keep believing he is endorsing your misled views.

[LColony_Kong]

3 hours ago, Panthera said:

No, no evidence to support you claim has been presented.

So this is just flat out false. All of the documentation we have agrees with at value of 1.4 for the mustang and 1.4ish for the 109.

 

3 hours ago, Panthera said:

Even Holtzauge's graphs, using a similar Clmax (which I disagree with), show a 1+ sec advantage in the K-4's favour with 1.8ata vs 75" Hg and same fuel load. Which is the exact reverse of the representation in IL2. So I honestly don't know why it is you keep believing he is endorsing your misled views.

You mean the +1 second I've been saying this entire time? And this is exactly what we find in il2 as I have demonstrated multiple times now. Posting turn rate tests at an random arbitrary speeds is just absurd and demonstrates nothing.

3 hours ago, Panthera said:

show a 1+ sec advantage in the K-4's favour with 1.8ata vs 75" Hg and same fuel load.

This is without altering fuel loads to be equivalent.

[Panthera]

10 hours ago, [TLC]MasterPooner said:

No it will not.

 

It will.

 

If you increase specific excess power (Ps) then you also increase the turn rate at the same speed up until you become lift limited. JtD is completely right about this.

 

If you take a look at the below dog house plots you'll see the curves listed Ps = x.

Ps = 0 is specific excess thrust equal to the drag generated in a level turn with no loss in altitude (refered to as max sustained turn rate) 

Ps = -400 is specific excess thrust PLUS gravity's help in a 400 ft/s diving turn (same effect as increasing thrust)

Ps = +400 is specific excess thrust MINUS gravity's help in a 400 ft/s climbing turn (same effect as decreasing thrust)

 

F-15

A-10

 

 

 

In short these charts allows you to directly observe how an increase (or decrease) in thrust affects the sustained turn rate of an aircraft, and as you can see an increase in thrust will heighten the Ps curve, allowing for a higher G to be sustained at the same speeds up until the lift limit (Clmax, max instantaneous rate) is reached. If you in turn increase the Clmax, then you move the lift limit curve to the left. Now if you instead increase wing area, you move the whole doghouse plot to the left. (Hence why aircraft size matters)

 

 

45 minutes ago, [TLC]MasterPooner said:

So this is just flat out false. All of the documentation we have agrees with at value of 1.4 for the mustang and 1.4ish for the 109.

 

No, it doesn't. I already told you under what condition the 1.4 figure applies, and it isn't the scenario we're discussing in this thread = dogfighting speeds & loads.

 

Similarly the 1.4'ish figure for the 109 is for a prototype with a completely different wing and no slats, and again at wind tunnel speed and 1 G.

 

45 minutes ago, [TLC]MasterPooner said:

This is without altering fuel loads to be equivalent.

 

No it's actually with the 109 carrying 12 liters more (400 vs 388 L).

Edited August 28, 2020 by Panthera

[Holtzauge]

Honestly, I think von Helsing should have driven a stake through this thread long ago but just let me add this: You can't use a jet chart to argue propeller plane turn characteristics: While not totally true as a first order approximation this holds true: One is a constant power producer the other a constant thrust producer which means an apples and pears comparison.

 

Finally: As far as I can see most here seem to agree that there is nothing wrong in IL2 at the moment: The P-51D's best sustained turn rate is a tad slower with the same fuel load as the Me-109K4 just as expected. Now if someone thinks what we have is wrong the onus is on THEM to prove their case not the other way around. As far as I can tell some here are trying to make it sound like we have to prove that part span slats (Yes, apparently the word PART SPAN needs to be highlighted in red) are not some kind of Wunderwaffe and that the P-51 doesn't have a terribly low Clmax. That is not how it works and I'm sure that by now the developers are either running out of popcorn, have dozed off in boredom, or simply switched channel.

[LColony_Kong]

3 hours ago, Panthera said:

f you increase specific excess power (Ps) then you also increase the turn rate at the same speed up until you become lift limited. JtD is completely right about this.

 

If you take a look at the below dog house plots you'll see the curves listed Ps = x.

Ps = 0 is specific excess thrust equal to the drag generated in a level turn with no loss in altitude (refered to as max sustained turn rate) 

Ps = -400 is specific excess thrust PLUS gravity's help in a 400 ft/s diving turn (same effect as increasing thrust)

Ps = +400 is specific excess thrust MINUS gravity's help in a 400 ft/s climbing turn (same effect as decreasing thrust)

If you increase PS you get more turn rate at that speed IF you also increase G load. At this point I am starting to think the lot of you cannot read or understand and equation. My response to JtD was to him looking at the 1.8 and 1.98ata 109s at the same speed with the same G load getting the same rate. Mathematically, its impossible for them to get different turn rates if these factors are the same. Read your own EM charts, you can see this happen.

 

3 hours ago, Panthera said:

No, it doesn't. I already told you under what condition the 1.4 figure applies, and it isn't the scenario we're discussing in this thread = dogfighting speeds & loads.

You need to read documents more carefully. TN1044 shows a mach number of .2 for the CL of 1.4 The P-51 in this chart is turning at a mach number of .23. We are in the right ballpark here. What is more, the P-51 tested at 25% fuel as in my tests unsurprisingly has a sustained turn speed at around 0.208 mach. Sustained turn speeds are "dog fighting" speeds.

 

4 hours ago, Panthera said:

Similarly the 1.4'ish figure for the 109 is for a prototype with a completely different wing and no slats, and again at wind tunnel speed and 1 G.

They are not full span slats. This had been gone over about a billion times. And the irony of claiming the mach number is wrong on the P-51 wing tunnel tests but then pointing out the that 109 is also at wind tunnel speeds...

 

4 hours ago, Panthera said:

No it's actually with the 109 carrying 12 liters more (400 vs 388 L).

You really have a hard time reading a document. That says 388KG not LITERS. The P-51 is carrying 524 liters of fuel compared to the 109s 400. (388/ 0.74)

[Aurora_Stealth]

 

Spoiler

(Click image to enlarge)

 

fyi - the thread makes it through in the end.

Edited August 28, 2020 by Aurora_Stealth

[Panthera]

The physics of what happens when you add thrust are always the same: Increase thrust and the Ps curve, within the lift limit, goes up. You can argue against this till your head goes blue, but you'd be arguing against the basic laws of physics.

 

In short the only difference between a jet and a prop job in this case is that the shape of the Ps curve looks different as a prop loses efficiency with speed, hence the Ps curve starts off high from the lift limit curve and then falls off more sharply with speed as thrust actually decreases for the prop job. Where'as with a jet thrust often increases with speed due to ram effect.

 

Calculated doghouse plot for a P-38 (green line is lift limit with flaps):

 

Notice how the Ps=0 curve moves up (within the lift limit) with increases in power/thrust.

 

 

 

Edited August 28, 2020 by Panthera

[LColony_Kong]

3 hours ago, Panthera said:

The physics of what happens when you add thrust are always the same: Increase thrust and the Ps curve, within the lift limit, goes up. You can argue against this till your head goes blue, but you'd be arguing against the basic laws of physics.

 

In short the only difference between a jet and a prop job in this case is that the shape of the Ps curve looks different as a prop loses efficiency with speed, hence the Ps curve starts off high from the lift limit curve and then falls off with speed as thrust actually decreases for the prop job. Where'as with a jet thrust often increases with speed due to ram effect.

 

 

 

 

Dude, at least try to understand what is being said.

 

If you have two 109 K-4s at the same turn speed and same g load, they will not turn better than each other regardless of the thrust. Because you are not USING THE THRUST.

 

Look at your own chart:

 

As Ps goes negative, either the G load or the velocity has to change to get a change in rate. In other words, you are either pulling the same or less G at a lower speed, more G at the same speed, etc.

 

 

 

 

 

Edited August 28, 2020 by [TLC]MasterPooner

[Panthera]

4 minutes ago, [TLC]MasterPooner said:

If you have two 109 K-4s at the same turn speed and same g load, they will not turn better than each other regardless of the thrust.

 

Except the G load won't be the same, as the higher thrust allows a higher G load (and thus rate) to be sustained at the same speed (!!)

 

You need to understand the difference between Ps & lift limit, sustained & instantaneous rate.

Edited August 28, 2020 by Panthera

[LColony_Kong]

3 hours ago, Panthera said:

 

Except the G load won't be the same, as the higher thrust allows a higher G load (and thus rate) to be sustained at the same speed (!!)

OH MY GOD.

 

The entire point Panthera was that the rates JtD quoted HAD THE SAME G LOAD at the SAME SPEED.

Edited August 28, 2020 by [TLC]MasterPooner

[Panthera]

1 minute ago, [TLC]MasterPooner said:

OH MY GOD.

 

The entire point Panthera was that the rates JtD quoted HAD THE SAME G LOAD.

 

Which is what he pointed out is a flaw in the simulation (!), and he is correct.

Edited August 28, 2020 by Panthera