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P-47 Flight Model Discussion

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Posted (edited)

Thanks for clarifying Holzauge!

I remain sceptical about dismissing the wartime reports based on the fact that two simulations (i.e. yours and the game) show the P-47 to be extremely close to the Spitfire in dive performance.

 

The wartime reports were made by combat pilots who had the reality of WWII air combat in their mind when they assessed both planes. I don't think they would have rated the P-47 as they did if it's performance was anywhere near to what we see in our simulations.

 

In addition, we have several lines of evidence indicating that the Spitfire's dive performance is too good in-game: it's on par in diving performance not only to the P-47, but to the FW-190A series as well. Both planes were reported to perform better in dives.

 

And we know that the Spitfire had clear aerodynamic flaws: the steep windshield alone cost it 12 mph at Mach 0.79 compared to the same plane equipped with a better windshield. And it's radiators ingested the slow boundary layer, which resulted in a sharp increase in drag.

Both factors would hurt the Spit most in high speed dives.

Here's a fragment of David Lednicer's "World War II Fighter Aerodynamics", a very interesting read on the topic.

Screenshot_2019-04-27-15-25-30-327.thumb.jpeg.a790459de20cf339184a79ddce880ae7.jpeg

 

Edited by JG27_PapaFly

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Are there any wartime sources that quantify the dive performance in a way we can compare? A report that says the p47 outdives a spitfire helps us very little because it is so vague. Wha kind of dive? What entry conditions? Without numbers to compare it to we are grasping in the dark. Right now we have two simulations largely agreeing with each other, which tells us that many of the assumptions made i the simulations are similar. It tells us that neither sim is completely off the wall crazy and if there is a problem it may be consistent between the models. Its certainly possible that both sims fail to account properly for diveperformance but if they do, that may mean that modeling dive performance accurately like this is very difficult and involves a departure from standard modeling assumptions.

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3 hours ago, unreasonable said:

Interesting: in this latter test the point where the P-47's speed exceeds the Spitfire's is 24 seconds!  Accepting the physics of this, and going back to thinking about the tactical consequences, reinforces for me that the lesson from this is not the idea that heavy planes should be able to dive away from a slow turning fight when they find themselves at a disadvantage, which I suspect many players expect, but that they (the high m/D plane) should dive at high speed at a target, take a shot - if they can - and then keep diving away without slowing down significantly, either to the relative safety of your AA zone or with enough separation that you can climb back to altitude.   If they do that there is no way a lower m/D  plane can catch them. 

 

Of course to do that you have to have significant altitude advantage, room below the target, and be prepared to make a fairly low percentage pass, so do not expect to see this done in the game very often.

 

Just as a matter of interest, @Holtzauge , P-47 vs Spitfire is not going to happen in the game, but what happens if you replace the Spitfire with a 109 G or K?  

 

Yes, I think there is an expectation that diving is a "get out of jail free card" and that was the theme in the Yak/Fw190 simulation Superetendard linked to earlier which showed that it can take an agonizingly long time to build separation if you get suckered into going slow in a better diving plane before disengaging.

Regarding the 109 sure, I have both the K and G2 modeled so maybe the K at 1.8 ata would be good to compare to the Mk9 at +18 boost?

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Sounds good: at least P-47 vs 109 K is a match up which people might get in the game world.  If you have time....

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Posted (edited)
3 hours ago, JG27_PapaFly said:

Thanks for clarifying Holzauge!

I remain sceptical about dismissing the wartime reports based on the fact that two simulations (i.e. yours and the game) show the P-47 to be extremely close to the Spitfire in dive performance.

 

The wartime reports were made by combat pilots who had the reality of WWII air combat in their mind when they assessed both planes. I don't think they would have rated the P-47 as they did if it's performance was anywhere near to what we see in our simulations.

 

In addition, we have several lines of evidence indicating that the Spitfire's dive performance is too good in-game: it's on par in diving performance not only to the P-47, but to the FW-190A series as well. Both planes were reported to perform better in dives.

 

And we know that the Spitfire had clear aerodynamic flaws: the steep windshield alone cost it 12 mph at Mach 0.79 compared to the same plane equipped with a better windshield. And it's radiators ingested the slow boundary layer, which resulted in a sharp increase in drag.

Both factors would hurt the Spit most in high speed dives.

Here's a fragment of David Lednicer's "World War II Fighter Aerodynamics", a very interesting read on the topic.

Screenshot_2019-04-27-15-25-30-327.thumb.jpeg.a790459de20cf339184a79ddce880ae7.jpeg

 

 

1 hour ago, RedKestrel said:

Are there any wartime sources that quantify the dive performance in a way we can compare? A report that says the p47 outdives a spitfire helps us very little because it is so vague. Wha kind of dive? What entry conditions? Without numbers to compare it to we are grasping in the dark. Right now we have two simulations largely agreeing with each other, which tells us that many of the assumptions made i the simulations are similar. It tells us that neither sim is completely off the wall crazy and if there is a problem it may be consistent between the models. Its certainly possible that both sims fail to account properly for diveperformance but if they do, that may mean that modeling dive performance accurately like this is very difficult and involves a departure from standard modeling assumptions.

 

 

Believe me: I have been trying to figure this out as well: Why is the difference not bigger? Either it's as simple as the pilots thinking a difference of 250-350 m is a big difference and if you think about it from the pilots viewpoint it's all relative: So even if you cover 14 Km in the dive you don't perceive that, what you perceive is the other plane pulling away, i.e. diving better and getting that amount of separation in a 60 s dive is not negligible.

 

If the difference actually should be bigger I'm more leaning towards the thrust modeling (prop efficiency loss due to supersonic tip speeds) at high subsonic speeds being at fault: The Spitfire's is actually quite good in the high speed drag department, with a late and low addition due to compressibility to a large extent due to the thin wing and clean design. Funnily enough most major fighters (the 109, Mustang and Fw190) had profiles (NACA 2R1, Laminar profile and NACA 230 series respectively) which were all actually quite good at high subsonic speeds although none had had that as a design criteria and was purely a fortuitous side effect of other design considerations such as aiming for a low drag and/or low pitching moment coefficient.

 

Edited by Holtzauge
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20 minutes ago, unreasonable said:

Sounds good: at least P-47 vs 109 K is a match up which people might get in the game world.  If you have time....

 

HAHAHAHHAHAHHAHAHAHAHHAHAHAH

 

no.

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11 minutes ago, [3./J88]PikAss said:

 

HAHAHAHHAHAHHAHAHAHAHHAHAHAH

 

no.

 

You have a comprehension problem. I did not say that it would be an even match up - merely that on occasion people flying P-47s would be in fights with 109-Ks, while they would not be in fights with Spitfires. 

 

ASS is right, though.

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38 minutes ago, unreasonable said:

Sounds good: at least P-47 vs 109 K is a match up which people might get in the game world.  If you have time....

 

OK, so here is the same dive scenario (from 6 to 1 Km in a 20 deg dive starting at 500 Km/h TAS) for both the 109K4 at 1.8 ata and G6 at 1.3 ata: The K4 is quite good: It dives the distance in the same time as the P-47 razorback but does so due to accelerating faster in the beginning while the P-47 is faster in the end.

 

The poor G6 gets left hopelessly behind and one can only sympathize with late war "Nachwuchs" climbing up to meet Thunderbolts bearing down on them while stuck in a "Beule"....:joy:

 

Me109K418ataMe109G613ata20deg.thumb.png.9b763b47da71b26fb1421efb39507958.png

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Yes a comparison between P-47D and Fw 190A-8 would be great, thx Holtzauge btw !

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Maybe Monday! Right now I'm nursing a good Tempranillo and tomorrow I'm gonna go flying!

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3 hours ago, RedKestrel said:

Are there any wartime sources that quantify the dive performance in a way we can compare? A report that says the p47 outdives a spitfire helps us very little because it is so vague. Wha kind of dive? What entry conditions? Without numbers to compare it to we are grasping in the dark. Right now we have two simulations largely agreeing with each other, which tells us that many of the assumptions made i the simulations are similar. It tells us that neither sim is completely off the wall crazy and if there is a problem it may be consistent between the models. Its certainly possible that both sims fail to account properly for diveperformance but if they do, that may mean that modeling dive performance accurately like this is very difficult and involves a departure from standard modeling assumptions.

 

I posted some conditions actually used in a report and the results of that report.

While this isn't the best it still gives us some starting conditions to go on, even if the final result isn't exact.

 

Fw-190A vs P-47

Altitude 10,000ft

250 mph when entering dive 

65 deg dive angle

Don't touch throttle in the dive but keep it at the same setting.

Fw190 should be a bit faster in the beginning but the P-47 should overtake it at around 3000 ft with much greater speed.

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Some pretty serious study going on here. All I know is that the P-47 simply doesn't feel right. The Spitfire feels, to me, the way I'd expect one to fly. The Thunderbolt just feels wrong. I'm sure that the speed is off. I CANNOT catch German fighters with it. When I'm playing with the labels on I can see the distance growing even with my boost on! I'm a bit dissapointed in it, frankly. 

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Posted (edited)
38 minutes ago, Poochnboo said:

Some pretty serious study going on here. All I know is that the P-47 simply doesn't feel right. The Spitfire feels, to me, the way I'd expect one to fly. The Thunderbolt just feels wrong. I'm sure that the speed is off. I CANNOT catch German fighters with it. When I'm playing with the labels on I can see the distance growing even with my boost on! I'm a bit dissapointed in it, frankly. 

I still have to test the speeds at different power/fuel levels. It does feel a bit too slow with full fuel though.

 

Another thing I'm curious about is the performance of the AO Smith propeller and how it differs from the Curtis electric paddle blade. I'm curious if the AO Smith results in a few mph speed difference, I know the Hamilton was slightly faster than the Curtis by a few mph.

Edited by Legioneod

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Posted (edited)
13 hours ago, Legioneod said:

I posted some conditions actually used in a report and the results of that report.

 

Additionally, I already posted dive comparisons between the A6M and several US fighters. The A6M, being light and rather slow by 1944 standards, certainly is one of the worst dive performance fighter aircraft and can thus be used to gauge top end expectations WRT to separation gained in a dive. In particular as it is compared to top dive performance fighter aircraft.

 

The relevant reports are available here:

 

http://www.wwiiaircraftperformance.org/japan/ptr-1111.pdf

 

and here

 

http://www.wwiiaircraftperformance.org/japan/zeke52-taic38.pdf

 

Also of interest a specific line in this report, even if not related to dive performance. Apparently Spitfires only carried fuel for five minutes of full power. :ph34r:

 

http://www.wwiiaircraftperformance.org/japan/spit-v-zero-wawn.jpg

Edited by JtD
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4 hours ago, JtD said:

Apparently Spitfires only carried fuel for five minutes of full power. :ph34r:

 

 

I see what you did there)))))

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7 hours ago, JtD said:

 

Additionally, I already posted dive comparisons between the A6M and several US fighters. The A6M, being light and rather slow by 1944 standards, certainly is one of the worst dive performance fighter aircraft and can thus be used to gauge top end expectations WRT to separation gained in a dive. In particular as it is compared to top dive performance fighter aircraft.

 

The relevant reports are available here:

 

http://www.wwiiaircraftperformance.org/japan/ptr-1111.pdf

 

and here

 

http://www.wwiiaircraftperformance.org/japan/zeke52-taic38.pdf

 

Also of interest a specific line in this report, even if not related to dive performance. Apparently Spitfires only carried fuel for five minutes of full power. :ph34r:

 

http://www.wwiiaircraftperformance.org/japan/spit-v-zero-wawn.jpg

 

image.png.4d8dfb00e7552de497354c37e13e275b.png

 

I am not an expert, but 100 yards seperation after 30 seconds doesn't seem like a huge advantage? If a target is on your tail and in shooting range, I don't think that would save you

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11 hours ago, =621=Samikatz said:

 

image.png.4d8dfb00e7552de497354c37e13e275b.png

 

I am not an expert, but 100 yards seperation after 30 seconds doesn't seem like a huge advantage? If a target is on your tail and in shooting range, I don't think that would save you

It’s definitely not a huge advantage. It’s marginal. But it does mean that if you have the enemy in gun range already they can’t get away. And it means that if you dive away before the enemy gets into gun range on you you are more likely to be able to escape. The world of the fighter pilot is built on tiny advantages magnified by tactics and skill.

So the real life comparisons that have actual numbers associated with them show that the dive advantage the p47 got against even a relatively poor diving zero in imperfect condition to be pretty marginal. In that light, it seems that what we see in game is not so different from what we would expect from real life. Reports say there was clear superiority, but at least in the case of the tests against the zero noted above, what is meant by that is a few hundred yards at the end of thirty seconds of diving. Expecting more from that against the late war planes we face in game doesn’t appear supported by the evidence.

 

 

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I totally agree, it's enough to stay out of guns you're already safe from, but the implication I get from some posters in this thread is they expect to nose down out of any situation

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4 hours ago, =621=Samikatz said:

I totally agree, it's enough to stay out of guns you're already safe from, but the implication I get from some posters in this thread is they expect to nose down out of any situation

This is the impression that the anecdotal evidence often gives - the war stories from pilot's memoirs, the comparative reports with no numbers, etc. Because there is no quantification in them, all we have is our subjective impression of their subjective description. And that kind of thing is very nearly useless in correcting a flight model. it may point to there being an issue, but without quantitative data any issue that does exist can't be corrected. 

I honestly expected, from what I'd read in pilot accounts, that the P-47 would outdive its opponents by a much larger margin. Especially something like the zero. Reading that wartime report, we have the Jug diving against a lightweight, poor diving aircraft with aerodynamic issues (gear covers aren't closing fully at high speeds, for example). It does dive better but not by huge margins. I think that has to set our expectations to be a bit more modest.

Whatever flaws there may be with how the P-47 is modeled, I'm not convinced that relative dive performance in the P-47 is off by a large degree, considering everything put into this thread. The issues with flaps, some stall behaviour and break-up speed are worth more investigation though.

 

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One piece of data we really need for the planes is the equivalent flat plate area drag, which can then be compared to weight. It's self-evident that a Jug is heavier than a 109, it is also evident that the Jug has a larger frontal area, but what is the ratio in each case?

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Flat plate area drag would not be helpful in any way. As has already been mentioned by Holtzauge, transsonic and supersonic behaviour becomes a large factor in dives, due to a) local airflow going transsonic and b) propeller tips going supersonic.

A P-47 13" prop at 2700 engine rpm has prop tip speeds of 280m/s, so even at sea level temperatures they go supersonic at true air speeds of about 650 km/h, less up high. A fast spinning prop in a dive essentially becomes one large air brake, while it still is the source of thrust in high speed level flight (obviously). Supersonic/transsonic drag is a lot larger than you'd get from extrapolating subsonic flat plate drag. It is the main reason why claims by some WW2 fighter aircraft pilots of going supersonic in a dive are considered to be wrong - physics don't add up.

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On 4/28/2019 at 8:40 AM, JtD said:

 

Additionally, I already posted dive comparisons between the A6M and several US fighters. The A6M, being light and rather slow by 1944 standards, certainly is one of the worst dive performance fighter aircraft and can thus be used to gauge top end expectations WRT to separation gained in a dive. In particular as it is compared to top dive performance fighter aircraft.

 

The relevant reports are available here:

 

http://www.wwiiaircraftperformance.org/japan/ptr-1111.pdf

 

and here

 

http://www.wwiiaircraftperformance.org/japan/zeke52-taic38.pdf

 

Also of interest a specific line in this report, even if not related to dive performance. Apparently Spitfires only carried fuel for five minutes of full power. :ph34r:

 

http://www.wwiiaircraftperformance.org/japan/spit-v-zero-wawn.jpg

 

Anytime anyone posts a pilot accounts with something like "our p-47 just outdives everything with ease", we should post those links instead of countless charts.  30 seconds and only 100 yards, or 91 metres is appalling separation from the dive king Jug compared to a Zero.  The Zero could literally give you all his ammo in that time :)

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1 hour ago, ICDP said:

Anytime anyone posts a pilot accounts with something like "our p-47 just outdives everything with ease", we should post those links instead of countless charts.  30 seconds and only 100 yards, or 91 metres is appalling separation from the dive king Jug compared to a Zero.  The Zero could literally give you all his ammo in that time :)

 

If the IRL P-47D would be similar to the one from this game you wouldn't need to out-dive the Zero - you would out-turn the Zero instead.... That's really enough to infer "something" about the current state of Thunderbolt modelling in this game. If only that would be only one "weird" thing but no.

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50 minutes ago, Ehret said:

If the IRL P-47D would be similar to the one from this game you wouldn't need to out-dive the Zero - you would out-turn the Zero instead.... 

 

I am laugh......😄

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58 minutes ago, ICDP said:

 

Anytime anyone posts a pilot accounts with something like "our p-47 just outdives everything with ease", we should post those links instead of countless charts.  30 seconds and only 100 yards, or 91 metres is appalling separation from the dive king Jug compared to a Zero.  The Zero could literally give you all his ammo in that time :)

I think a lot of the pilot accounts are from the escorting P-47s, who were flying at high altitude where their planes performed best, and when they attacked the enemy it was often with an altitude advantage. So we're talking about a P-47 entering a dive from a couple thousand feet above an enemy, at a high speed, at high altitude where drag is lower, and if its a razorback with lower overall drag. In this context, the likelihood of a 109 or even 190 being able to escape is very small. The P-47's marginal advantage in a dive is magnified by the situation. It quickly becomes true that the enemy cannot dive away from the Jug unless they do so with enough separation. If the enemy starts diving only after seeing the P-47 diving on them, and the P-47 is within 1000 yards or so, they're screwed. There is no situation in combat where a P-47 is going to pull up alongside a 109 and then both enter the dive at the same time. 

Conversely, if the 109 is diving on the P-47, and the P-47 dives away, that slightly marginal advantage can keep the 109 from closing to guns range long enough for a wingman to help him out.

I mean, we talk all the time about 109F4 being much faster than Yak-1 in level flight. But we see that often that advantage is 20 km/h or less, especially at lower altitudes. In a straight chase, this will either result in the 109F4 closing on a Yak by about 5 m/s, or the 109F4 running away by the same amount. That means it takes 20 seconds for the 109 to gain 100 m on a Yak! In that time the Yak can empty all of his ammo into the F4. And we see the same arguments about the Yaks being too fast sometimes (not so much anymore) because the Yaks sometimes catch the 109s, and this should be impossible because pilot accounts say that the plane is much faster and they can simply fly away from the Russians! No one will reasonably argue that the 109 doesn't have a significant advantage because of this though, its just not going to be the massive difference people expect from stories, and it may disappear entirely in the right or wrong situations.

Marginal advantages make big differences in combat, which is why we have attempts to squeeze more and more out of airplanes, engines, and equipment. Basic rule of thumb: if you're in gun range, running alone will probably not save you, even if your plane is faster overall.

 

44 minutes ago, Ehret said:

 

If the IRL P-47D would be similar to the one from this game you wouldn't need to out-dive the Zero - you would out-turn the Zero instead.... That's really enough to infer "something" about the current state of Thunderbolt modelling in this game. If only that would be only one "weird" thing but no.

I still think the flaps behaviour is a global issue with how flaps and deployment are done in-game, we see other weirdness with flaps in the Yak and the Spit sometimes. We have no idea how 'combat flaps' would work on a P-47 since it was basically impossible to use them IRL due to assymmetric deployment. And frankly I've seen more people online in P-47s using flaps get killed than I've seen survive because of them, even with the weird behaviour you wind up low and slow and the G-14s, K-4s and D9s eat you for breakfast anyway.

The three areas I've seen complaints are the flaps (possibly global problem IMO) the dive (highlighted here, and I'm mostly convinced this is a perception issue rather than a accuracy issue) and the engine management (the way the timers work are inconsistent between different planes, at the very least that should be looked at and made consistent, at best we would see a bit of an overhaul on engine management, but once again this appear to be a global issue with how engines are modeled). 


 

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Posted (edited)

I'm not sure if you are agreeing or not, but your post kinda proves the point.  Pilot account without context and conditions mean absolutely nothing in comparative plane performance.  Some virtual pilots read these vague pilot accounts and conclude, "dive in P-47 = instant escape ALWAYS" and when it doesn't happen they come to the forum to complain about LW UFOs.  The same happens when a 109 or 190 pilot gets caught in a dive by a Yak or LaGG.

 

That is the crux of the problem, these dive tests were done at co alt and co speed and as such having only a few hundred metres (at best) separation after 30-60 seconds of a dive is shows that in this regard the sim has got it right.

 

So my point is once again that these real WWII tests can be used to stop these kind of complaints dead.

Edited by ICDP
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10 hours ago, ICDP said:

I'm not sure if you are agreeing or not, but your post kinda proves the point.  Pilot account without context and conditions mean absolutely nothing in comparative plane performance.  Some virtual pilots read these vague pilot accounts and conclude, "dive in P-47 = instant escape ALWAYS" and when it doesn't happen they come to the forum to complain about LW UFOs.  The same happens when a 109 or 190 pilot gets caught in a dive by a Yak or LaGG.

 

That is the crux of the problem, these dive tests were done at co alt and co speed and as such having only a few hundred metres (at best) separation after 30-60 seconds of a dive is shows that in this regard the sim has got it right.

 

So my point is once again that these real WWII tests can be used to stop these kind of complaints dead.

 

The biggest problem imho is correcting the wrong impression that linger in the sim community. I for example also thought there was something wrong with the dive accelleration in the P47. Now, after reading Holtzauges sims and the other boffin number crunching, I stand corrected. I accept that I had a wrong believe. Others, I have a niggling feeling, are not so readily convinced. So you have to repeat the stuff in this thread over and over. And it takes only one or two lines to give the wrong idea: "P47 could outdive anything! P47 ace Jugster McThundybolter said so himself!", but it takes a complete thread to show why that is not correct given most situations.

 

So thanks to Holtzauge and the others for their time writing this stuff up. 

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Posted (edited)

Thanks @Holtzauge

 

This should clear some doubts.

We are stupid if we think the devs released a porked P47. The plane flies by its numbers like every other one in the sim. It might be more or less accurate but that doesn't have anything to do with pilot records.

Science never lies, only the fools that don't trust it

 

Edited by LF_Gallahad
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There is that one quote from I don't quite recall who again that says : 'the tempest with throttle shut would overtake a Fw190 in a dive'.

 

So be prepared to get a similar thread concerning tempest dive performance when this happens not to be the case....

 

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18 hours ago, ICDP said:

I'm not sure if you are agreeing or not, but your post kinda proves the point.  Pilot account without context and conditions mean absolutely nothing in comparative plane performance.  Some virtual pilots read these vague pilot accounts and conclude, "dive in P-47 = instant escape ALWAYS" and when it doesn't happen they come to the forum to complain about LW UFOs.  The same happens when a 109 or 190 pilot gets caught in a dive by a Yak or LaGG.

 

That is the crux of the problem, these dive tests were done at co alt and co speed and as such having only a few hundred metres (at best) separation after 30-60 seconds of a dive is shows that in this regard the sim has got it right.

 

So my point is once again that these real WWII tests can be used to stop these kind of complaints dead.

I'm agreeing with you 100%, I just get ranty sometimes lol.

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Posted (edited)

Dive accelerations seems to be close or acceptable imo.

 

The main problem when it comes to dives is the structural limit of the P-47 which is incorrect in-game, and the way compressability is modeled.

Also the elevator authority seems lacking from all accounts but I need more research on the subject.

Edited by Legioneod

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On 5/3/2019 at 5:27 AM, ICDP said:

So my point is once again that these real WWII tests can be used to stop these kind of complaints dead.

 

They do but it is only temporary. There are always new people coming along so the misconceptions have to addressed over and over again and each time it can take a while to overcome inbuilt assumptions.  Those of us who have seen the same problems hashed over several times just have to accept that in a forum people do not search for every thread that might possibly be related - hardly surprising given how much the threads tend to ramble and divert.

 

And that is just fine: we all come here from different backgrounds with varying knowledge about basic physics, advanced engineering, actual WW1/2 tactics, how military organizations actually work, the reliability of sources, statistics, game engine and modelling limitations: the list is long, and everyone has gaps in their knowledge. 

 

The great thing about this forum is the number of people who are willing to fill in the gaps. The number of people willing to have their gaps filled in is a little smaller, ;), but most do, and appreciate the discussion as an educational process. 

 

 

 

   

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1 hour ago, unreasonable said:

 

 

They do but it is only temporary. There are always new people coming along so the misconceptions have to addressed over and over again and each time it can take a while to overcome inbuilt assumptions.  Those of us who have seen the same problems hashed over several times just have to accept that in a forum people do not search for every thread that might possibly be related - hardly surprising given how much the threads tend to ramble and divert.

 

And that is just fine: we all come here from different backgrounds with varying knowledge about basic physics, advanced engineering, actual WW1/2 tactics, how military organizations actually work, the reliability of sources, statistics, game engine and modelling limitations: the list is long, and everyone has gaps in their knowledge. 

 

The great thing about this forum is the number of people who are willing to fill in the gaps. The number of people willing to have their gaps filled in is a little smaller, ;), but most do, and appreciate the discussion as an educational process. 

 

 

 

   

 

I totally agree about your point that people will continue to ask these questions and will need educated.  I always find FM threads interesting and educational.

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10 hours ago, Legioneod said:

The main problem when it comes to dives is the structural limit of the P-47 which is incorrect in-game, and the way compressability is modeled.

Also the elevator authority seems lacking from all accounts but I need more research on the subject.

 

I think the structure-issue is a major drawback on the P-47. The ailerons coming off just isn't right.

The key might be the high-speed aerodynamics modelling, which hopefully will be improved with the 262.

 

Got any specifics WRT elevator authority?

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12 hours ago, Bremspropeller said:

 

I think the structure-issue is a major drawback on the P-47. The ailerons coming off just isn't right.

The key might be the high-speed aerodynamics modelling, which hopefully will be improved with the 262.

 

Got any specifics WRT elevator authority?


It would be an galactic scale irony if 262 ailerons fell of in nominal, level straight, flight at high altitude at full throttle . :crazy:

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15 hours ago, Bremspropeller said:

 

I think the structure-issue is a major drawback on the P-47. The ailerons coming off just isn't right.

The key might be the high-speed aerodynamics modelling, which hopefully will be improved with the 262.

 

Got any specifics WRT elevator authority?

 

Especially since the manual states that the problem past 500 mph is compressibility forcing the nose down and making it almost impossible to pull out until lower alt is reached. Countermeasures listed are to INCREASE power, which is not something you'd do if you were afraid of shedding control surfaces. 

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40 minutes ago, ACG_Kai_Lae said:

 

Especially since the manual states that the problem past 500 mph is compressibility forcing the nose down and making it almost impossible to pull out until lower alt is reached. Countermeasures listed are to INCREASE power, which is not something you'd do if you were afraid of shedding control surfaces. 

 

Yep, structurally the P-47 was very sound and unlikely to break up due to high speed, especially at 500 mph, which actually wasn't the speed the P-47 hit compressability.

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In my experience none of BoX, IL2 original, or WW2 fighters in DCS model dive performance correctly.    Which is a disappointing trend, but not surprising - given 'a scientific level' of data for aerodynamics associated with dive performance is not available, as it is for easily measurable things like:  Level speed performance, climb performance, and turn performance, total drag in level flight in a wind tunnel, etc.

 

I think at some point in this thread various people have already made these points, but IMO these are the most important factors missing in dive mechanics that would result in more variability between aircraft types:

 

1. Cross sectional drag vice mass in a vertical dive:   less drag / unit of mass will affect vertical acceleration positively, and immediately upon a entering a dive - just not much at the beginning when IAS is relatively low along with associated drag.

 

2. Induced drag needed in level flight is virtually not a factor when in a vertical dive -  a P47 is heavy; with heavy comes a lot of induced drag that reduces low speed acceleration and top speed in level flight.   Given equivalent level flight performance to some P47 contemporaries like a Spit 9 or G6,  the P47 is dumping a lot more induced drag in a vertical dive - to it's advantage.  It seems that sim aero modeling retains the same induced drag penalty incurred in a level flight calculation in a dive - which would be incorrect.

 

3. High speed "trim" drag. - How balanced is the airframe, wing, and tail unit at high speed?   Varies by aircraft design - for instance, a design exercise on improving late war 109 performance included changing the angle of incidence of the wing to improve high speed drag.

 

4.  Ballistic 'efficiency' - I believe the reason the P47 is such a good energy fighter - it accelerates more quickly in a dive than most of it's contemporaries due to the above factors, and due to an efficient airframe, wing, mass, and high power, can quickly translate a dive into good vertical ballistic performance.    By 'wing' efficiency I mean the aircraft retains lift at moderate g and moderate aoa without 'mushing' as a 190 did in a comparative test.      There's that problematic word, 'comparative' again :)

 

Just one pilot and long time simmer's opinion... 

 

 

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My point WRT aileron flutter is that the P-47 actually had a quoted aileron-reversal speed, which means this speed is attainable from a structural and aeroelastical standpoint.

 

 

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