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P-47 Maneuverability or Lack Thereof


MrRistro
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6 hours ago, ZachariasX said:

Lifting line theory is good at geting performance figures right, it tells you next to nothing what happens (and how things happen) at the very edge of the enveloppe, where we venture most of the time. The sims based on similar FM logic are prone to producing similar artefacts. It is very hard having control response over the entire speed range right, especially when you don't have access to the real aircraft or have sketchy data.

 

Control response vs. plane weight (inertia) is a particularly tough nut to crack. You can give it a lot of control, and you get a butterfly of a plane like in the ridiculous videos posted above. You can give the controls less bite, but then you get the wobbly, rubberbanding slug that pleages most FM's in some way. They may dampen the oscillations, but then they dampen inputs as well. I have yet to see a real aircraft certified for aerobatics that is lagging stick inputs as the simulated planes in almost all sims do. You find that aircraftin sims  are generally lagging control input. This to varying degrees. This makes precise flying hard. It's like putting a Chevy steering in a Porsche. ("Well, it has the same turn radius, so what's your problem?"

 

Regarding this sim, I see nothing specific to the P-47 that is not how it (reasonably) could be. What the FM may be suffering from, that I find on many aircraft, the Spit XIV being the biggest victim. (I hope she gets an FM revision at some point because that wale is not a Spit yet.) As almost no simulation gets these things really right, I don't expect a simple fix. For any plane.


They've been working on it since 2014. Eagle Dynamics put it on the back burner in favour of aircraft that were easier to model due to lack of data restrictions. This isn't hard proof of anything, but I certainly have more faith in DCS actually standards and saying we aren't going to release something if it cannot be modelled to their standards.

That's an interesting point Zach. I sometimes wonder how much IL2 has catered their flight models to the general shorter stick length of what you can buy on the market. Giving the aircraft an appropriate feel for what the aircraft would fly like as if you had a longer stick. I hate to bring up DCS again, but with their Spitfire IX and P-47 they've clearly stated that you will limited to the lack of length in your flight controls.


I do agree with your statement on how the P-47 performs in this sim. I'm actually not too keen on increasing its manoeuvrability. Possibly they have over done the "Heavy Aircraft" feel. I do believe I have the edge over a Bf-109 at high speeds in terms stick forces. I don't fly the spitfire so, I'm too sure what you are having troubles with.

Edited by DSR_A-24
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3 hours ago, ZachariasX said:

If it has to be done for every plane in the sim and still produce 100 FPS while computing thousands of bullets zipping through the air and entire aircraft systems, then it starts to get difficult. Plus you have to have programmers that can do all of that.

 

I do not mean to run the simulation in real time, take ~10 data points of certain extreme situation, run the sims, observe the results and generate simplified model.

 

2 hours ago, unreasonable said:

Computational simulations are just hypothesis generators - I would like to see the empirical test results that validate the projections, no matter how impressive, particularly for the Dragon Maid. 

 

Yes and no, they are more often correct than not if done properly. Many big bois in industry do 90% of the heavy lifting with computers and validate the stuff with prototypes. 

(That 90% used to be done with real stuff and wind tunnel test and 10% was done using slide-rulers and pencil)

 

And we are not even doing prototypes, we are just testing some of the edge cases, and we can validate the simulation by testing it with known data, like stall data from common air frames. 

 

I am 100% sure you will get better results than the current guesstimates we have in our sim now. 

 

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I wonder if they (complex simulations) really are more often correct than not - after all, how can you tell if they are done properly without real testing?

 

Much modern military machinery fails to work as advertised, leading to expensive refits, upgrades, delays or even occasional cancellations. It is not in the interest of the contractors to do real tests because it is a) expensive and b) they might fail. Of course they prefer simulations. When they are forced to do real tests, they are fixed to give the desired results. Occasionally something useful slips through the system by mistake ;).  That is just how the military-industrial complex works.  

 

That aside, we cannot even agree on what the actual TAS Vmin of the real P-47 was, making it very difficult to validate any model even for a simple edge-of-envelope case.

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14 hours ago, DSR_A-24 said:

I'm too sure what you are having troubles with.

 

TL;DR: Response to pitch input depends on CG/aerodynamic stability, not really plane weight and weight dirstribution.

 

You can reproduce that with most aircraft. The easiest way to do so is taking a plane in QMB and fly just that, nothing else, so you have least overhead for your system. What you do is you trim the aircraft straight, level flight, and then pull up the nose quickly in one swift motion, as fast as you can. In a sense, do the "short stick thing" (That the other sim guys frown upon for now obvious resons). By doing so, the plane wil start to raise his nose progressively faster until it hits the pitch rotation speed corresponding to the deflection of the elevator control. In simulators, heavier aircraft tend to have a significant lag (you have to "turn-accellerate" more mass) and planes with longer noses tend to be "less pitchy" that way.

 

What you are looking for you can easiest meter with a stopwatch when you go (EDIT) 1/4x time aceeleration (you can do that if it's just you on the map). Fly her level, then pull the stick back maybe 1/5th of the travel and as soon as you yank the stick back start timing. Take time until the pitching speed of the corresponding is reached. You will find that planes are drastically different in that. The Spit XIV on average lags stick input by ~1/4 sec., depending on your input of course. The P-47 lags less but it does so, notably, still making it cumbersome for quick snapshots that work so well in the 190 or the 109.

 

This lag. It must not be there.

 

Over the years, the infamous wobble, a consequence of reactions lagging inputs and quick coarse inputs in general were damped out. Quiet to the dismay of some elites, that considered this "making it more difficult" being realistic, because it is difficult. Of course it made most non-elites garbage at hitting anything but sky. But the control lag remained. What can be a consequence of the plane reacting with a lag to stick inputs, Scott Crossfield found flying the X-15 for the first time:

 

Crossfield later wrote in his book “Always Another Dawn”, “My right hand moved to the sidearm control handle, which I had elected to use on this flight.” He had been much involved in the design of the controller, and was itching to try it out. He then notes that almost immediately after launch the plane’s nose unexpectedly pitched up, and he quickly applied nose down control with the side controller. Instead of just leveling off, the nose pitched down, prompting him to apply a nose up control that overshot the mark even more. Subsequent attempts at trying to level off resulted in a pitching oscillation that was getting worse as he was getting closer to the lake bed.

 

This overshooting happens with most planes in this sim and sometimes makes aim harder than it should be. It is the first oscillation of the infamous wobble. The consecutive oscillations now are mostly damped out inmost sims of today. Only slow input can mask entirely that behaviour. This is why you are required to have a long stick to get on average a suitable flight experience. But not when you are really pushing it. Hence what they ask of you is putting a truck steering whell into the Porsche that they can only equip with a Cadillac steering. If the car cannot corner, then you better use a steering wheel that makes it impossible for you to corner, hence no problem.

 

The overshooting is a consequence of making excessive stick inputs as the nose just doesn't want to follow stick input and you are trying to overplay this effect. Hence, e.g. you pull back half way, only to go back to normal again split second later and then pull back slightly to maintain the pitch rate. Same as your LCD monitor overshoots on black to white when you want higher FPS that it actually can deliver, you make too strong of a Voltage input to hopefully catch it once desired signal is reached. It's a crutch and in our case garbage, as it has noithing to do with the aircraft that are simulated.

 

The "nippyness" of your (real) crate does not really depend on weight. At least not while you are traveling at reasonable airspeed. It much rather depends on how stable/neutral/unstable your aircraft is. The F-22 weights as much as two P-47, yet it is one of the most agile aircraft available. And this is becuase it is an unstable aircraft. The whole fly by wire controls could not work if there was not an instant, immediate and robust control by moving the various control surfaces. If the F-22 took a quater of a second to follow commands if would never fly. Never. (Far enough for a write-off does not count.)

 

The readyness of the P-47 to respond to control inputs depends on the loadout, the CG of the plane much more than the weight. The only issue the P-47 may have in this sim is that if anything, it is mosty slightly too stable. This requires you to pull her by the hair the maneuvers. Making the aircraft less stable will make it feel more agaile, yet it will be way easier to make her depart. So if you complain that she is not nimble enough and that she stalls all the time, then you are asking for mutually contradicting properties, essentially a different aircraft than she is. You can make her more nimble by putting weight in the back but then you will stall her very easily with more severe consequences.

 

Again, I see no general performance problems in the P-47. Actually, all aircraft in this sim have a remarkably plausibe flight performance. There are some outliners, but in general at this price point, I have deep respect for the devs for what they deliver.

 

It takes particular aircraft that are unlike others to make them outliners in this (and most other) sim. I mentioned the CG as determinant for instant maneurability. The Spit is a special case there. It is a tailheavy design that actually sits on the elevator in flight. You can see on all pictures of in flight Spitfires that it has an elevator down position. (In this sim, outs doesn't and it shows in the FM.) When you fly the real one, the stick is about 10 cm forward from what is neutral on  the ground. This means, the aircraft will jump at any chance to put her nose up or down. You can pull g's with one finger. The only "mushiness" in control that you might detect is that it is a cable design and not pushrods. This makes her a bit more elastic. But this is almost an academic issue. The elevator is lighter and more effective than any GA aircraft I can think of out there. It may be comparable to that of a CAP 10, but that is already an purposly aerobatic aircraft. (Which in MSFS has the same mushy garbage elevator control that reacts too little around the center and too much towards the extremes.)

 

What is noticeable in simulators, is that the longer and heavyier the nose gets, it progressively affects elevator effectiveness. In the real arcraft this is really only circumstancial. But in this sim there is already a step down from the MkV to the MkIX. This would be tolerable, as the V is the lighter aircraft an should thus tolerate a bit more if you take her for borderline aerobatics (that is what they also found out back then), but how the plane reacts to the pitch input depends on the actual CG. With he MkXIV, something terribe happened in this sim. It became notably nose heavy (250 kg more in front) and you can see that in the sim you fly her usually in an "elevator up" configuration. Having CG that far in front which makes her very stable in flight and she gets progressively reluctant to follow pitch. And this is what we are seeing in the game. It is not a Spit anymore. (This, together with the wobble in yaw made me ditch "the other" Spit and I never used her since.)

 

What should be - and I tried it specifically - is that the real Spit IMMEDIATELY follows pitch input to EXACTLY the extent you give it. There is no lag in nothing. I Tried it. I tried with all my might (on the rudder, that takes a fair bit of force even in normal flight) and the plane doesn't wobble, it doesn't lag. At all times it does EXACTLY what the input is. You push one pedal, she immedaiately yaws and says at the yaw deflection that corresponds to your pedal input. She does that as fast as I am physically able to depress the pedal.

 

The fact that she is neutral in pitch makes required inputs way smaller than intuitively expected, to the extent that in normal bank turns you don't give any elevator input at all, else you'd be again climbing 1000 ftm without any drop in speed. (At least until you are in Heathrow airspace and face other issues.)

 

This trim does affect the P-47 and it makes the plane sluggish, even at speed. I don't think the P-47 was sluggish in control, but that doesn't mean she can fly a Red Bull Racing course.

 

For anyone still arguing for weight, big engine, etc. as a bona fide reason that pitch performance (that is the main issue of the P-47) is impaired, just this: A 3 ton Spitfire is far more responsive on the elevator than a 1 ton Robin DR400.

Edited by ZachariasX
You have to decellerate to better stop lag time of stick input reactions.
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19 minutes ago, ZachariasX said:

 

TL;DR: Response to pitch input depends on CG/aerodynamic stability, not really plane weight and weight dirstribution.

 

You can reproduce that with most aircraft. The easiest way to do so is taking a plane in QMB and fly just that, nothing else, so you have least overhead for your system. What you do is you trim the aircraft straight, level flight, and then pull up the nose quickly in one swift motion, as fast as you can. In a sense, do the "short stick thing" (That the other sim guys frown upon for now obvious resons). By doing so, the plane wil start to raise his nose progressively faster until it hits the pitch rotation speed corresponding to the deflection of the elevator control. In simulators, heavier aircraft tend to have a significant lag (you have to "turn-accellerate" more mass) and planes with longer noses tend to be "less pitchy" that way.

 

What you are looking for you can easiest meter with a stopwatch when you go 4x time aceeleration (you can do that if it's just you on the map). Fly her level, then pull the stick back maybe 1/5th of the travel and as soon as you yank the stick back start timing. Take time until the pitching speed of the corresponding is reached. You will find that planes are drastically different in that. The Spit XIV on average lags stick input by ~1/4 sec., depending on your input of course. The P-47 lags less but it does so, notably, still making it cumbersome for quick snapshots that work so well in the 190 or the 109.

 

This lag. It must not be there.

 

Over the years, the infamous wobble, a consequence of reactions lagging inputs and quick coarse inputs in general were damped out. Quiet to the dismay of some elites, that considered this "making it more difficult" being realistic, because it is difficult. Of course it made most non-elites garbage at hitting anything but sky. But the control lag remained. What can be a consequence of the plane reacting with a lag to stick inputs, Scott Crossfield found flying the X-15 for the first time:

 

Crossfield later wrote in his book “Always Another Dawn”, “My right hand moved to the sidearm control handle, which I had elected to use on this flight.” He had been much involved in the design of the controller, and was itching to try it out. He then notes that almost immediately after launch the plane’s nose unexpectedly pitched up, and he quickly applied nose down control with the side controller. Instead of just leveling off, the nose pitched down, prompting him to apply a nose up control that overshot the mark even more. Subsequent attempts at trying to level off resulted in a pitching oscillation that was getting worse as he was getting closer to the lake bed.

 

This overshooting happens with most planes in this sim and sometimes makes aim harder than it should be. It is the first oscillation of the infamous wobble. The consecutive oscillations now are mostly damped out inmost sims of today. Only slow input can mask entirely that behaviour. This is why you are required to have a long stick to get on average a suitable flight experience. But not when you are really pushing it. Hence what they ask of you is putting a truck steering whell into the Porsche that they can only equip with a Cadillac steering. If the car cannot corner, then you better use a steering wheel that makes it impossible for you to corner, hence no problem.

 

The overshooting is a consequence of making excessive stick inputs as the nose just doesn't want to follow stick input and you are trying to overplay this effect. Hence, e.g. you pull back half way, only to go back to normal again split second later and then pull back slightly to maintain the pitch rate. Same as your LCD monitor overshoots on black to white when you want higher FPS that it actually can deliver, you make too strong of a Voltage input to hopefully catch it once desired signal is reached. It's a crutch and in our case garbage, as it has noithing to do with the aircraft that are simulated.

 

The "nippyness" of your (real) crate does not really depend on weight. At least not while you are traveling at reasonable airspeed. It much rather depends on how stable/neutral/unstable your aircraft is. The F-22 weights as much as two P-47, yet it is one of the most agile aircraft available. And this is becuase it is an unstable aircraft. The whole fly by wire controls could not work if there was not an instant, immediate and robust control by moving the various control surfaces. If the F-22 took a quater of a second to follow commands if would never fly. Never. (Far enough for a write-off does not count.)

 

The readyness of the P-47 to respond to control inputs depends on the loadout, the CG of the plane much more than the weight. The only issue the P-47 may have in this sim is that if anything, it is mosty slightly too stable. This requires you to pull her by the hair the maneuvers. Making the aircraft less stable will make it feel more agaile, yet it will be way easier to make her depart. So if you complain that she is not nimble enough and that she stalls all the time, then you are asking for mutually contradicting properties, essentially a different aircraft than she is. You can make her more nimble by putting weight in the back but then you will stall her very easily with more severe consequences.

 

Again, I see no general performance problems in the P-47. Actually, all aircraft in this sim have a remarkably plausibe flight performance. There are some outliners, but in general at this price point, I have deep respect for the devs for what they deliver.

 

It takes particular aircraft that are unlike others to make them outliners in this (and most other) sim. I mentioned the CG as determinant for instant maneurability. The Spit is a special case there. It is a tailheavy design that actually sits on the elevator in flight. You can see on all pictures of in flight Spitfires that it has an elevator down position. (In this sim, outs doesn't and it shows in the FM.) When you fly the real one, the stick is about 10 cm forward from what is neutral on  the ground. This means, the aircraft will jump at any chance to put her nose up or down. You can pull g's with one finger. The only "mushiness" in control that you might detect is that it is a cable design and not pushrods. This makes her a bit more elastic. But this is almost an academic issue. The elevator is lighter and more effective than any GA aircraft I can think of out there. It may be comparable to that of a CAP 10, but that is already an purposly aerobatic aircraft. (Which in MSFS has the same mushy garbage elevator control that reacts too little around the center and too much towards the extremes.)

 

What is noticeable in simulators, is that the longer and heavyier the nose gets, it progressively affects elevator effectiveness. In the real arcraft this is really only circumstancial. But in this sim there is already a step down from the MkV to the MkIX. This would be tolerable, as the V is the lighter aircraft an should thus tolerate a bit more if you take her for borderline aerobatics (that is what they also found out back then), but how the plane reacts to the pitch input depends on the actual CG. With he MkXIV, something terribe happened in this sim. It became notably nose heavy (250 kg more in front) and you can see that in the sim you fly her usually in an "elevator up" configuration. Having CG that far in front which makes her very stable in flight and she gets progressively reluctant to follow pitch. And this is what we are seeing in the game. It is not a Spit anymore. (This, together with the wobble in yaw made me ditch "the other" Spit and I never used her since.)

 

What should be - and I tried it specifically - is that the real Spit IMMEDIATELY follows pitch input to EXACTLY the extent you give it. There is no lag in nothing. I Tried it. I tried with all my might (on the rudder, that takes a fair bit of force even in normal flight) and the plane doesn't wobble, it doesn't lag. At all times it does EXACTLY what the input is. You push one pedal, she immedaiately yaws and says at the yaw deflection that corresponds to your pedal input. She does that as fast as I am physically able to depress the pedal.

 

The fact that she is neutral in pitch makes required inputs way smaller than intuitively expected, to the extent that in normal bank turns you don't give any elevator input at all, else you'd be again climbing 1000 ftm without any drop in speed. (At least until you are in Heathrow airspace and face other issues.)

 

This trim does affect the P-47 and it makes the plane sluggish, even at speed. I don't think the P-47 was sluggish in control, but that doesn't mean she can fly a Red Bull Racing course.

 

For anyone still arguing for weight, big engine, etc. as a bona fide reason that pitch performance (that is the main issue of the P-47) is impaired, just this: A 3 ton Spitfire is far more responsive on the elevator than a 1 ton Robin DR400.


I'm not going to say I fully understand what you've said but thanks for explaining. I suppose this explains why I find the Bf-109 and Fw-190 such a great gun platforms, as they have no notable lag input.

I'm not sure what the "short stick thing" is.

"In simulators, heavier aircraft tend to have a significant lag (you have to "turn-accellerate" more mass) and planes with longer noses tend to be "less pitchy" that way."

Hence the Fw-190D9 and Ta-152 having progressively longer tails?

So a response in pitch input, or perceived agility, is more responsive in an unstable aircraft? An aircraft longitudinal stability is then defined by not its weight, but its CG and aerodynamic stability. Where my confuse lies now is if the previous Spitfires were tail heavy and the XIV added 250kg to the nose of the aircraft would that make a more stable plane and hence more reluctant to smaller pitch inputs in level flight? Which is the exact phenomenon you are feeling in game. What Spitfire did you actually fly? I'm assuming you're saying that the Spitfire IX had zero notable input lag hence the difference in between the V and the IX in game isn't even supposed to be there, but it is tolerable by the community. However when the XIV came the input lag was very much noticeable from the IX.

Thanks.

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55 minutes ago, ZachariasX said:

The readyness of the P-47 to respond to control inputs depends on the loadout, the CG of the plane much more than the weight. The only issue the P-47 may have in this sim is that if anything, it is mosty slightly too stable. This requires you to pull her by the hair the maneuvers. Making the aircraft less stable will make it feel more agaile, yet it will be way easier to make her depart. So if you complain that she is not nimble enough and that she stalls all the time, then you are asking for mutually contradicting properties, essentially a different aircraft than she is. You can make her more nimble by putting weight in the back but then you will stall her very easily with more severe consequences.

 

Again, I see no general performance problems in the P-47. Actually, all aircraft in this sim have a remarkably plausibe flight performance. There are some outliners, but in general at this price point, I have deep respect for the devs for what they deliver.

Without taking into account the differences in Cl Max that Yakpanther pointed out (whether or not they are truly accurate) and that would help with sustained turn, the fact that the P-47 was a responsive plane is found in one of the article he mentioned (https://ntrs.nasa.gov/citations/20090022749). In a discussion in the other sim about this same item, the main FM programmer indicated that this article actually says that the p-47 was neutral stable in some conditions.

I do not see detrimental in making the p-47 more agile. Obviously, is going to be more prone to depart if you are not careful. But I would say that very much in like with what a fw190 is already doing. You will have to re-learn how to take it to the edge. Benefit being that you would come back to flying a fighter instead of a medium bomber.

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33 minutes ago, DSR_A-24 said:

I'm not sure what the "short stick thing" is.

Making to coarse movements. A longer stick prevents some of the fast angular deflections one can easily make with short sticks.

34 minutes ago, DSR_A-24 said:

Hence the Fw-190D9 and Ta-152 having progressively longer tails?

Sort of. First of all, it was an efficient way getting the CG back after getting a new engine in a longer nose. It also helped for stability in pitch control at altitude.

 

36 minutes ago, DSR_A-24 said:

So a response in pitch input, or perceived agility, is more responsive in an unstable aircraft?

Yes. A stable aircraft needs more deflection of the same elevator than an unstable for the same pitch control movement of the same tail arrangement.

 

32 minutes ago, HR_Zunzun said:

the main FM programmer indicated that this article actually says that the p-47 was neutral stable in some conditions.

Hence it should be pleseant to maneuver. Within reason at least.

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 The lift and drag curves on Foiltools.com  for the Republic S-3 are not reliable. The model lacks enough detail for comparative analysis. There are far too few panels used in their modeling. There are only 37 panels on their S3 airfoil. The result is that the leading edge geometry is far too coarse. 

jxLhuJJVlYBcsu2s-X2hNkpd3Ze8M9a7ebt9_Ptr3QJNhB53xsbMJbxniX8fAm_4qVqHY7qLB9C8OMbLu8NyiJ6u69dBefeRlZG636YpumEcU-_JnBd9ZQfqEmfn9y_90BUf-hZx=s0

 

 The leading edge geometry of the Republic S-3, as presented on AirfoilTools.com, is a result of the software using linear approximation to spline the leading edge together. Which causes the leading edge to be poorly resolved with excessive angles.

 

The result is premature shearing of flow and a nonlinear distribution of pressure along the leading edge. 

 

oqyYIf0bdg-WSzhqrYhWdqURxFvm_kCyhI2oV2v7OdPjnHcuAL5D1CteCzC6RnEY42Eg53rVFrPdeyqDfUKN9aXNFtCingsxw6Sua_NxPhFtoFZxhOlyorZ9BhxWw2NXPvdPWl6x=s0

 

The Airfoil tools Republic S-3, As compared to the real airfoil S-3 at mach .25 AoA 1. Both models are of relatively the same thickness. 11% for the Foiltools.com S-3 model and 10.5% for the NACA L4G12 model. 

.FxPwsaRVvjBBDcx_QIXHnFQMdtbyZc-koJyFBJbHLO1EydVSO2yI_5l3AGHVz4OajK8-muZ-U3k1Ws-dlIwxJVboa5YgnAcRnsRrtHgc1x-1cDM2Ozv0uqZt3bUfeM1MqoMldV-M=s0

https://ntrs.nasa.gov/api/citations/19930092838

 

Due to the coarseness of the FoilTools.com S-3 model, the pressure distribution is both irregular and higher when compared to the NACA model at the same conditions. Therefore performance analysis of P-47 and S-3 airfoil based on Foiltools.com S-3 data and model should be avoided.

 

There are still other numerous sources which can provide us with an idea of the lift coefficient
 

I found the NACA wind tunnel tests of the P-47 prototypes. These tests were cited in the Analysis of the Aerodynamic Design of the P-47.

zykB_AxOeIpDMqcvhYfmg5qeBNA-4MpBaYUjl42SsCJSUBF1BYkdoyRGFKMMogTwkMyblPn780Fm_v0WXiRPpoV9GDrAe8AHMB26YUHIch3zSQ08lyqe-mz62ZKMldjZw0-EH8UB=s0

This report cites a Cl max of 1.63 for P-47 wing on the P-41 fuselage. 

4baavaerLH1Dgc1u-SK5woeYv0kDkdmw64Xaj8MsPqzBCdylejskI4saTNDgnatgGVRhW9LwDrJ7W5Zkm4Vw8-7IgXQW6ZSK1te-aanYNzBxci5M2lJE-BVGX_qvEYMGv1eh_uDt=s0

N7lU5WxXbbj5SBh4qydMWYlXT0Y7bdd-q1QD72W4bCCKD9BS3OJKLnsNSnZ0lf9WIjaHG90asOhEW1ymGhMf9GqLOqWfN46DLoYyNhQmLIep8hv4M23QiCVOQGdxJQd91s2ofEWn=s0

https://ntrs.nasa.gov/api/citations/20150014120/downloads/20150014120_Redacted.pdf9laIrgWsYzGilsnKSkEzah-jLnrCw2pz-_YJ73TeE7Q4BMK1xxZTL4C-p4H_8Er4i-yDMr8GTdU0Er219WwM3r68rYXdlUpuRYiQ-L0JGLLHGDqjgByblOORaQm76hMFE2jyI1K5=s0

The wind tunnel test data of that model. 

 

 

https://ntrs.nasa.gov/citations/19820069268

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Which give a Cl max of 1.6 at ~19 AOA at an Re of 4.8e6

0WvrU78Shj3JSgADZAF7kF8QUjVDXcqhsQ9lPf0bp87n_SEGbggQlwp0y8Y2kzE1SGdS1Ms8RyeJO9NIvTf3i0k6XcNUyqnx9b4ljZy6zqy8UYyos8pEdJhlkd0wowK5cHvT8YsE=s0

There are also the wind tunnel tests of the 1/6 scale model test of the P-47C.

fiy8sCUwKr_V_Ofac-jtcMH75rz2drr3fBJc4eqs7vQepAl16SETR7oMAbPmZwQgTypeBjHrnzhDUgPUQlsCl4B9MsfZFhZKuXncrjBh0u5d0YN7QlEzaoh-IP0S_-2AnYxxaHmZ=s0

 

EHVoUWLsPhCqJ8-bYbYV9JHr0EJcwC7H8b_XxL4czCJbuLt4XIeE-C2RD2D_Doxz6RU_mxpFNGghPe374APjv0a1v8Ya0J8FOGEzevsBGEvhf_sbVbEDZkEl62Jb0jbK11A7QhOJ=s0


 

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https://ntrs.nasa.gov/citations/20150019986

The power on Test Put the Cl max at ~ 1.8
 

The high speed wind tunnel tests of the P-47D model show a similar Cl to AOA relationship. Both models have a Cl of 1.2 at ~ 12 AOA.

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https://ntrs.nasa.gov/citations/20150011311


 

There is however, a primary source data from the manufacturer regarding the P-47's performance. It is in, NACA L5I04 “Analysis of Effect of Rolling Pull-Outs on Wing and Aileron Loads of a Fighter Airplane.”

 

 The NACA was computing the effect of rolling pull outs on wing and aileron loads of the P-47. Republic provided the NACA with a V-N diagram for the P-47.

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Republic says that a 12,000 lbs P-47 is capable of 8g at 271 EAS, at sea level. 

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https://ntrs.nasa.gov/citations/19930092725

Republic states the Cl Max of P-47 is 1.7

 

 

Edited by Yak_Panther
fix citation link, add pic
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5 hours ago, Yak_Panther said:

Republic states the Cl Max of P-47 is 1.7

 

No, they don't.

 

"The wing lift coefficients at the corners of the dlagram were listed by the manufacturer as 1.75, 0.419, -0.206, and -5.~20 at the points A, B, C, and D, respectively."

 

These are wing lift coefficients, not aircraft lift coefficients. 1.75 is totally unreasonable for an aircraft like the P-47. The aircraft at point A in fact has a lift coefficient of 1.3 (8g*12000lb @271 mph with 300 sqft reference area). Which is totally reasonable for an aircraft like the P-47.

 

I'd appreciate if you put the figures you post into the proper context on your own. Otherwise it's a wasted effort to go through NACA reports for information.

 

Anyway, to sum up what you've provided in your posts:

 

The maximum lift coefficient for the P-47 is 1.3 according to the data of the manufacturer. Thanks, now we know.

 

---

 

Edit: Made a typo in the spreadsheet. That chart really does give 1.7. It is related to structural loads, it probably makes sense to check what assumptions are behind these type of curves.

Edited by JtD
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28 minutes ago, JtD said:

 

No, they don't.

 

"The wing lift coefficients at the corners of the dlagram were listed by the manufacturer as 1.75, 0.419, -0.206, and -5.~20 at the points A, B, C, and D, respectively."

 

These are wing lift coefficients, not aircraft lift coefficients. 1.75 is totally unreasonable for an aircraft like the P-47. The aircraft at point A in fact has a lift coefficient of 1.3 (8g*12000lb @271 mph with 300 sqft reference area). Which is totally reasonable for an aircraft like the P-47.

 

I'd appreciate if you put the figures you post into the proper context on your own. Otherwise it's a wasted effort to go through NACA reports for information.

 

Anyway, to sum up what you've provided in your posts:

 

The maximum lift coefficient for the P-47 is 1.3 according to the data of the manufacturer. Thanks, now we know.

 

Where do you get 1.3 from?

 

It’s not the 1/6  scale model test with the propeller off. Those give a Cl max of 1.4

 

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The same model with propeller running gives Cl max of 1.8

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The 30% scale model without propeller effects,  gives a Cl max of 1.4 at 15 alfa.  

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-vqQBCm0733fsGTVmTxCkhXQM834-92qlct1smseGZUzgtHDQ1yayfNIdbqA5clphDd5wr3S3dnN5gxXOlcxp0xfM7YaJy2Dbvrpp0AxQpPuDmnfzT626g4_oOQ1Yth-1RMOks7P=s0

The Vn diagram for the aircraft gives a CL of either 1.5 or 1.7 depending on where you compute it

 

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2 hours ago, JtD said:

Yes it does.

 

Odd that actual flight test 1g stall speeds are typically in the range of 110mph@13000lbs.

Is that range for power on or off? 

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Power off.

 

I just find it odd that Republic would use any other than a static power off cl for wing design purposes. In German engineering rules of the time designers had, among other things, to calculate structural strength for the points A, B, C and D. Typically, clmax was a simplified assumption there, but it would be in the vicinity of what the plane actually was doing statically, power off (i.e. 1.4-1.5).

There are reasons to do it differently, but it's surprising for me and at this point I'd have to speculate, which isn't really useful.

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If chart 5, shown above was "the diagram used in the design of the wing" as the NACA report states, how could the designers have known the plane's actual cl when they drew it? 

 

I mean maybe they hoped/designed to stall (1g) at 100mph, near enough, but it turned out to be closer to 110mph (as flight test data suggests). That is enough to account for the differences in the calculated CLmax.

 

 

edit: For the laymen like me who are puzzled by what that chart 5 shows, this generic version may be helpful.

 

561857591_Vndiagram.thumb.JPG.1fb6db7c23d773fb16cc4d6ca07cc909.JPG

 

 

Edited by unreasonable
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