P-47: bad at boom and zoom?

[ICDP]

4 minutes ago, Raven109 said:

If you believe that the D-25 chart from AHT is true, then you should cap the max speed to the aircraft to 425mph after 25000ft, although the 65" can reach up to 437mph accoring to the tests at 25000ft.

 

Could the difference be explained by the fact the AHT tests shows 14,500lb weight for the P47D.  While the other tests are at a weight of 12,730lb for the P47D?  1,770lb is a substantial difference.

Edited June 10, 2020 by ICDP

[CountZero]

I putt the numbers in that il-2 compare and if P-47D behaved like proposed by Legioneod then its chart should look like red line, blue is how its in game now from my tests.

[Legioneod]

3 minutes ago, ICDP said:

 

Could the difference be explained by the fact the AHT tests shows 14,500lb weight for the P47D.  While the other tests are at a weight of 12,730lb for the P47D?  1,770lb is a substantial difference.

This pretty much. Look at my last post and you'll see the D-25 at around 1,500+ lighter weight.

[ICDP]

16 minutes ago, Legioneod said:

This pretty much. Look at my last post and you'll see the D-25 at around 1,500+ lighter weight.

 

I did two quick tests.  1 at 100% fuel and 1 at 25% fuel.  Both at 29,522ft (9,000m).  Kuban Autumn map.

 

100% fuel.  Top speed 254 mph IAS - 411 mph TAS

25% fuel.  Top speed 260 mph IAS - 421 mph TAS

 

So if we compensate for the higher weight and add a similar 10mph to TAS numbers from the AHT test it would be ~435mph.  I appreciate the input and the way we are conducting this conversation by just looking for factual information and being open to a change of position.

Edited June 10, 2020 by ICDP

[Legioneod]

Just now, ICDP said:

 

I did two quick tests.  1 at 100% fuel and 1 at 25% fuel.  Both at 29,522ft (9,000m).  Kuban Autumn map.

 

100% fuel.  Top speed 254 mph IAS - 411 mph TAS

25% fuel.  Top speed 260 mph IAS - 421 mph TAS

 

So if we compensate for the higher weight and add a similar 10mph to TAS numbers from the AHT test it would be ~435mph.  I appreciate the input and the way we are conducting this conversation by just looking for factual information and being open to a change of position.

Agreed. I feel like I've been going crazy looking through all this. At first I didn't think I was correct either and figured it was a regulator or turbo difference but as I started to do research it all began to make alot more sense.

Honestly the AHT chart really helped imo, at least shows I'm not the only one who noticed this quirk. Makes me feel an bit more confidant that there should be a constant speed curve above 64" critical altitude even if it doesn't outright prove it.

[Raven109]

1 hour ago, Legioneod said:

I'm not confusing things dude, I've checked this over and over again. The D-26 I listed above uses a power of 56" not 64" and an A-23 regulator.

You can keeps saying I'm wrong but the speed curve should be pretty much straight between 64" critical alt to 56" critical alt.

 

The reason the D-25 was slower in that chart is because it was 14,500 lbs. At lighter weights it is faster.

 

 

 

 

1 hour ago, Legioneod said:

I'm not confusing things dude, I've checked this over and over again.

 

Apologies, I didn't mean to come of as rude, as it seems I might have.

 

So many questions:

What does "P-47D-26 only" mean? Why is the P47D-26 singled out? What does the * next to the speed mean?

 

Also, why is the D-25 manual listing a 52" military power setting from 26000ft up to 34000ft @ 2700RPM?

 

Why aren't any of the official tests showing the speed for D-22 (65", 2600HP) as being >425mph above 29000ft? Could it be that the 26 is an outlier and that it's using the A-17 regulator? Why isn't it boosted to 64"? Could it be that it can't be boosted because of the A-17 regulator? Could it be that it's using a more efficient propeller, which uses more of the available engine power?

 

I'm sorry, without having more information I cannot draw a conclusion. The conclusion I have is that there are two types of engine setup. One for high altitude one for medium to high. The one for medium to high altitude can reach at the 65"Hg 2700 RPM + H2O throttle setting a speed of 417mph @ 29500ft. (this is important - this throttle setting can produce 2200HP at 29500ft, while the 56" can only do 2000HP).

 

The weaker power setting cannot produce more power (and consequently more speed) than the stronger one everything else being equal (i.e same airframe, same engine, same turbo, same propeller). 

 

According to your screen shot, the D-26 is doing at least 436mph at that altitude. This to me is contradicting information, which tells me that I'm missing some information about how the power systems were setup for each D model. (I know that the manual states how they were setup, but to me it doesn't add up).

 

Btw, even from what you've posted you can see the trend that the 56" models can always do better up high, while the higher boost cannot do the same... something must be different between the two, don't you think?

 

If you look at the speed trials for the D-10, you can see that a different propeller can add ~10mph to the speed. Do the manuals say which propeller was used on the D26 when doing 436mph?

Edited June 10, 2020 by Raven109

[Legioneod]

27 minutes ago, Raven109 said:

 

 

Apologies, I didn't mean to come of as rude, as it seems I might have.

No problem man, you're not being rude and I completely understand your confusion because I was the same way when I first started looking into it. I'll try to break it all down in a way thats kinda less confusing hopefully.

 

Quote

 

So many questions:

What does "P-47D-26 only" mean? Why is the P47D-26 singled out? What does the * next to the speed mean?

Basically this just means that those figures are for that specific P-47 block, every block has slight changes in configuration that can give it more or less weight than the previous block, this is why they had to test each major block individually to get the speed figures.

The * next to the speed is just saying that in ideal atmospheric conditions the P-47 at the specified weight and power setting will reach that speed at that altitude, it could be slightly higher or lower depending on the conditions.

 

Quote

 

Also, why is the D-25 manual listing a 52" military power setting from 26000ft up to 34000ft @ 2700RPM?

All P-47s used the same exact military power settings of 52" @ 2700rpms. I can't say the reason it listed those altitudes but my guess is that it's just the critical altitude for 52".

If you look back at the D-25 manual you posted you'll notice that 52" is available from sea level all the way to 34,000ft.

Spoiler

 

Quote

 

Why aren't any of the official tests showing the speed for D-22 (65", 2600HP) as being >425mph above 29000ft? Could it be that the 26 is an outlier and that it's using the A-17 regulator? Why isn't it boosted to 64"? Could it be that it can't be boosted because of the A-17 regulator? Could it be that it's using a more efficient propeller, which uses more of the available engine power?

So the main reason for the D-26 using 56" is because the boost weren't increased for the aircraft at that time, later on nearly all P-47s including the D-26 got higher boost settings.

Just for comparison here is a D-22 with 56" boost settings at 29,000ft. 

 

Later on the D-22 was boosted to 64" WEP, this dropped the critical altitude to 24,500ft but the P-47 could still attain 56" at 29,000ft like it could previously because the engine, turbo and regulator remained the same.

 

Quote

 

I'm sorry, without having more information I cannot draw a conclusion. The conclusion I have is that there are two types of engine setup. One for high altitude one for medium to high. The one for medium to high altitude can reach at the 65"Hg 2700 RPM + H2O throttle setting a speed of 417mph @ 29500ft. (this is important - this throttle setting can produce 2200HP at 29500ft, wile the 56" can only do 2000HP).

 

The weaker power setting cannot produce more power (and consequently more speed) than the stronger one everything else being equal (i.e same airframe, same engine, same turbo, same propeller). 

 

According to your screen shot of the D-26 is doing at least 430mph at that altitude. This to me is contradicting information.

 

So the main reason for this is that the power required for high speeds at 29,000ft is less than the power required to achieve the same speed at 24,000ft.

 

So at 29,000ft the P-47 only needs 2,300 HP (56" WI) to get 430+ mph but at 24,000 ft it would need 2,600hp so they had to increase the boost to 64" to achieve this.

Since the turbo, engine, and turbo regulator remained the same when they upgraded to 64" WEP it dropped the critical altitude to 24,500ft.

So even though the critical altitude dropped (due to the turbo not being able to achieve 64" above 24,000ft) the P-47 could still achieve the older setting of 56" WI at 29,000ft.

 

Hopefully this all makes sense but if not I'll try to go into more detail.

Edited June 10, 2020 by Legioneod

[Raven109]

1 hour ago, Legioneod said:

So at 29,000ft the P-47 only needs 2,300 HP (56" WI) to get 430+ mph

 

This is where the contradiction is.

Why can't the D-22 at a higher boost reach the same speed as the D-26. Same engine, same propeller, same turbo.

 

The D-22 test, at 13230lbs can do 423mph @ 2250HP @ 19500ft. I'd expect the D-22 to have the same speed at that height, same engine, same power, same everything. Let's assume that the difference is because of weight, and the D-22 is heavier (which probably means increased drag). Equalizing the weight would just shift the speed curve of the D-22 to the right, it will not make it go straight up. We just established that a heavy D-25 exhibits a plateau on its power curve, and that if we remove the weight the plateau will just shift to the right. Then the same thing must happen for the D-22 test, if we assume it's overweight.

 

All the speed curves (which come from official tests) for the P-47 have just one inflection point. None have a plateau, there is no reason to believe that there is a plateau based on official data. None of the power settings tested produce a plateau.

 

Why is the speed of the D-22 falling so abruptly after the FTH max speed point, since it can also maintain the 56"+H2O setting, yet the D-26 higher up than D-22s FTH can do more speed?

 

The 65"+H2O speed curve starts dropping off at 25000ft. If you extrapolate the 56" speed curve to meet the 65"+H2O speed curve, you can see that it's not 436mph, it's only ~423mph at that height, and it doesn't form a plateau with the max speed at FTH. Why not derive the data for our D-28 from this graph, for a plane that can actually do 65" boost, and for which we have the official test data, instead of assuming that we should be creating a plateau out of nowhere? From my point of view, changing the 65" speed curve to fit the 56" speed curve is a much more bigger leap in faith, than just getting the speed value off the curve that we already have.

 

What I'm saying is, you can't get more power from 56"+H2O than 65"+H2O at the same height from the same engine. Since the speed curve shows that the speed at 29500ft is 423mph, it doesn't add up to the D26 speed, unless they are somehow different?

 

So, either shift the whole D22 curve to the right, to match the D26 speed at 29000ft, or accept that the D22 curve is more precise, since it's a 65" boost airplane just like the 28, and go with this. Combining data from the D-10 with the D-22 and D-26 to obtain the final result for the D-28 doesn't sound like something realiable.

 

 

 

Actually, I'm not even sure why we're deriving data for the D-28, by looking at other models. Aren't there specs for the D-28?

 

Edited June 10, 2020 by Raven109

[Legioneod]

42 minutes ago, Raven109 said:

 

This is where the contradiction is.

Why can't the D-22 at a higher boost reach the same speed as the D-26. Same engine, same propeller, same turbo.

No contradiction at all. I've shown you the power needed for 435+mph at 29,000ft for the D-26 and the D-22. Power needed is 2,300 hp which is 56" with water injection.

 

Main reason for the D-22 in that test not reaching the same speeds is because it didnt use WEP above critical altitude for all I know.

I've even shown you a D-22 that was running 56" WEP at 29,000ft with a top speed of 443mph. Thats only 2,300hp needed for that speed.

 

I honestly don't know how to explain this better.

[Raven109]

The same power is needed for both aircraft, yet the test shows different speeds at the same alt, and the same power setting.

 

The document shows that it's using WEP. I'm not talking about the 56"+H2O setting, but the 65"+H2O, which probably at that altitude is close to 56"+H2O in output power or greater than.

 

BTW, the D-10 tests were also using water, to get to 56". All tests were using water.

 

Ok, so the manual is showing 443, while the test 423.  Probably different set-up for the test, but something which is not obvious, at least to me.

 

 

13 minutes ago, Legioneod said:

I honestly don't know how to explain this better.

 

You really don't have to... the questions are not only for you, it's a public forum.

 

The tests don't add up with the figures you've posted.

Edited June 10, 2020 by Raven109

[Legioneod]

28 minutes ago, Raven109 said:

The same power is needed for both aircraft, yet the test shows different speeds at the same alt, and the same power setting.

 

The document shows that it's using WEP. I'm not talking about the 56"+H2O setting, but the 65"+H2O, which probably at that altitude is close to 56"+H2O in output power or greater than.

 

BTW, the D-10 tests were also using water, to get to 56". All tests were using water.

 

Ok, so the manual is showing 443, while the test 423.  Probably different set-up for the test, but something which is not obvious, at least to me.

 

 

 

You really don't have to... the questions are not only for you, it's a public forum.

 

The tests don't add up with the figures you've posted.

The reason they show two different speeds is because the one in the test wasn't producing 2,300hp at 29,000ft because it wasn't using water injection at that altitude.

56" with water is similar in power (not exact) to 65" without water. The 56" curve you see in the D-22 test is without water injection.

 

Example. Both aircraft below share the same exact engine, turbo, and turbo regulator.

P-47 #1 has a boost setting of 56" WI 2300hp at 29000ft

P-47#2 has an increased boost setting of 64" 2600hp at 24,500ft.

Why can't P-47 #2 use the same power as #1? They both share the same engine setup so why can't the higher boosted P-47 achieve the lesser power.

 

There is simply no reason for a P-47 with the same engine, turbo, and turbo regulator to not be able to produce a lesser power at a higher altitude just because it got a boost increase.

[RedKestrel]

6 minutes ago, Legioneod said:

 

56" with water is similar in power (not exact) to 65" without water. The 56" curve you see in the D-22 test is without water injection.

 

Looking at this, I have to think that maybe my understanding of water injection has been flawed for a long time.

I always thought that water injection just made the engine able to deliver higher manifold pressure without causing detonation to occur. So 64" of MP produces the same amount of power regardless of whether water injection is occurring or not, but without injection detonation occurs and basically blows up your engine.

But what you're saying is, on any given MP setting, if water injection is occurring, the plane is producing more power. Do I have this right?

[Legioneod]

3 minutes ago, RedKestrel said:

Looking at this, I have to think that maybe my understanding of water injection has been flawed for a long time.

I always thought that water injection just made the engine able to deliver higher manifold pressure without causing detonation to occur. So 64" of MP produces the same amount of power regardless of whether water injection is occurring or not, but without injection detonation occurs and basically blows up your engine.

But what you're saying is, on any given MP setting, if water injection is occurring, the plane is producing more power. Do I have this right?

Yes. Water injection does increase power to some degree, you can see this in the chart below. Notice 65" with and without water. The HP difference is noticeable.  

~2400HP vs ~2600HP

Edited June 10, 2020 by Legioneod

[Raven109]

16 minutes ago, Legioneod said:

The reason they show two different speeds is because the one in the test wasn't producing 2,300hp at 29,000ft because it wasn't using water injection at that altitude.

56" with water is similar in power (not exact) to 65" without water. The 56" curve you see in the D-22 test is without water injection.

 

Example. Both aircraft below share the same exact engine, turbo, and turbo regulator.

P-47 #1 has a boost setting of 56" WI 2300hp at 29000ft

P-47#2 has an increased boost setting of 64" 2600hp at 24,500ft.

Why can't P-47 #2 use the same power as #1? They both share the same engine setup so why can't the higher boosted P-47 achieve the lesser power.

 

There is simply no reason for a P-47 with the same engine, turbo, and turbo regulator to not be able to produce a lesser power at a higher altitude just because it got a boost increase.

 

The speed graph shows a speed curve for 65"+H2O (it says on the actual curve). At 29500ft that curve shows a speed of only 423mph.

 

I'm not talking about different alts. Only about 29500ft, at 65"+H20. I marked the point on the last pic I posted. The power obtained there is bigger than what 56"+H2O would produce, or at least equal.

 

Please have a look at the power curves below (there is a power curve for 65"+H20) - at 29500ft the 65"+H2O curve is at 2200HP. 56"+H20 cannot produce more power than 65"+H2O at the same alt.

 

Edited June 10, 2020 by Raven109

[Legioneod]

2 minutes ago, Raven109 said:

 

The speed graph shows a speed curve for 65"+H2O (it says on the actual curve). At 29500ft that curve shows a speed of only 423mph.

 

I'm not talking about different alts. Only about 29500ft, at 65"+H20. I marked the point on the last pic I posted. The power obtained there is bigger than what 56"+H2O would produce, or at least equal.

 

Please have a look at the power curves below (there is a power curve for 65"+H20) - at 29500ft the 65"+H2O is at 2200HP. 56"+H20 cannot produce more power than 65"+H2O.

 

56" With water injection will absolutley produce 2,300HP. 2300HP is all that is needed at 29000ft for 430+ speeds.

 

Also, 64" can only be produced up to 24/25K ft with the turbo that is being used, after that the manifold and power will start to drop off. At 29000ft you cannot produce 64" manifold pressure but you can produce 56". If H2O is used with 56" it will produce at least 2300HP.

[Raven109]

5 minutes ago, Legioneod said:

56" With water injection will absolutley produce 2,300HP. 2300HP is all that is needed at 29000ft for 430+ speeds.

 

Also, 64" can only be produced up to 24/25K ft with the turbo that is being used, after that the manifold and power will start to drop off. At 29000ft you cannot produce 64" manifold pressure but you can produce 56". If H2O is used with 56" it will produce at least 2300HP.

 

Then what do you think the 65"+H2O line is, if not a power setting bigger or equal to 56"+H2O. I know the turbo cannot maintain 65", just assume that the throttle is pushed fully forward, for max power at that altitude.

Edited June 10, 2020 by Raven109

[Legioneod]

Just now, Raven109 said:

 

Then what do you think the 65"+H2O line is, if not a power setting bigger or equal to 56"+H2O. I know the turbo cannot maintain it, just assume that the throttle is pushed fully forward.

The throttle is pushed forward of course, P-47 FTH is really only 3,000-7,000ft iirc after that you need the turbo to produce full power. What matters is the turbo setting.

[Raven109]

10 minutes ago, Legioneod said:

The throttle is pushed forward of course, P-47 FTH is really only 3,000-7,000ft iirc after that you need the turbo to produce full power. What matters is the turbo setting.

 

Ok, I simplified, since I didn't think it deserves more attention.

 

Let me rephrase: assuming that everything is configured in the cockpit to get the max possible power out of the aircraft at that altitude, what do you think the 65"+H2O power curve at 29500ft is, if not a setting that produces equal or more power than the 56"+H2O @ 29500ft?

 

Yes, according to the figures you've pasted the engine should produce 2300HP @ 56"+H2O. What do you think is the reason that the 65"+H2O power curve is showing less power at 29500ft?

 

 

Edited June 10, 2020 by Raven109

[Legioneod]

4 minutes ago, Raven109 said:

 

Ok, I simplified, since I didn't think it deserves more attention.

 

Let me rephrase: assuming that everything is configured in the cockpit to get the max possible power out of the aircraft at that altitude, what do you think the 65"+H2O power curve at 29500ft is, if not a setting that produces equal or more power than the 56"+H2O @ 29500ft?

 

Yes, according to the figures you've pasted the engine should produce 2300HP @ 56"+H2O. What do you think is the reason that the 65"+H2O power curve is showing less power at 29500ft?

 

 

Simply put it wasn't using water injection above 65" critical altitude. If it was then it would produce 2300hp. From the looks of it they tested to critical alt probably above as well but the power drop is so sharp that it's unlikley that they tested water injection above the critical altitudes, if they did then they just didnt record it.

If you follow the curve it doesnt just drop back sharpley.

With a turbosupercharged system the power drop is much more gradual and not so sharp like shown in the test. You can see this by looking at the curve up until the critical altitude, just continue on that curve pattern and you'll see it's much more gradual of a drop off.

 

Imo this simply shows that water injection wasnt used above a certain altitude in these test because if it was then the curve would be much more sublte and wouldnt cut so sharp.

[Raven109]

If it wasn't using water at that alt it should be the same power as the 65" power curve. Also, I'd expect the power curve to not be called 65"+H2O if it's not 65" and H2O. At any height.

 

 

Edited June 10, 2020 by Raven109

[Legioneod]

2 minutes ago, Raven109 said:

If it wasn't using water it should be the same power as the 65" power curve.

I didnt say it wasnt using water, I said it wasnt using water above it's 65" critical altitude. You can see this in the test by how sharp the cutoff it on the curve at 65" critical altitude of 25,000ft.

What I'm saying is that if it was using water at 29,000ft it would produce 2300hp, at least it should. Only explanation is that the test is using a different turbo, it's using a different engine than the production D-22 so it's possible.

 

This chart is a clear representation of what the curve would look like, the speeds might be different but the curve would be similar.

At the very least the below chart shows that what I'm saying has some historical basis, he didnt just make the chart up himself or pull it out of thin air.

[Raven109]

3 minutes ago, Legioneod said:

What I'm saying is that if it was using water at 29,000ft it would produce 2300hp, at least it should. Only explanation is that the test is using a different turbo, it's using a different engine than the production D-22 so it's possible.

Well, yes, this is why I said that there is a discrepancy between the figures you posted and the test data, probably took me longer to get here than I'd like, but at least we seem to be on the same page.

 

I am still assuming that the D-22 test was run with H2O for the 65" throttle/turbo setting, even at 29500ft (there is no information to indicate otherwise). Which produces a single point of inflection along the speed curve. This is why I can't reconcile the data you posted with the data from the test, and this is why I don't like the idea of combining the speed from the manual you posted with the speed from the D-22 test. To me they seem to be different machines and/or different test conditions.

 

Regarding the book, it seems to be the single source to post that type of speed curve, why does that have to be correct? Does it have any reference to its sources? I'm not saying it's a bad book, but errors do happen.

 

 

[Legioneod]

4 minutes ago, Raven109 said:

Well, yes, this is why I said that there is a discrepancy between the figures you posted and the test data, probably took me longer to get here than I'd like, but at least we seem to be on the same page.

 

I am still assuming that the D-22 test was run with H2O for the 65" throttle/turbo setting, even at 29500ft (there is no information to indicate otherwise). Which produces a single point of inflection along the speed curve. This is why I can't reconcile the data you posted with the data from the test, and this is why I don't like the idea of combining the speed from the manual you posted with the speed from the D-22 test. To me they seem to be different machines and/or different test conditions.

 

Regarding the book, it seems to be the single source to post that type of speed curve, why does that have to be correct? Does it have any reference to its sources? I'm not saying it's a bad book, but errors do happen.

 

 

The only difference between the D-22 I posted and the D-22 in that test is that it's using a different engine, (possibly a different turbo as well)

The D-22 that I posted is the standard production D-22, it's using 56" H2O and achieves 443mph at 29,000ft, one it was uprated to 64" it would achieve that speed at a lower altitude and show the curve I'm talking about.

 

As far as the book goes I'm sure the sources are listed the author was an aeronautical engineer so I'm guessing he was pretty thorough with his research. Always possible that there could be some errors but from what I've seen it's accurate.

[Raven109]

13 minutes ago, Legioneod said:

The only difference between the D-22 I posted and the D-22 in that test is that it's using a different engine, (possibly a different turbo as well)

The D-22 that I posted is the standard production D-22, it's using 56" H2O and achieves 443mph at 29,000ft, one it was uprated to 64" it would achieve that speed at a lower altitude and show the curve I'm talking about.

 

As far as the book goes I'm sure the sources are listed the author was an aeronautical engineer so I'm guessing he was pretty thorough with his research. Always possible that there could be some errors but from what I've seen it's accurate.

 

Does the manual say what's the max speed at 64" for the D-22?

 

Or are we just left to use one speed from one source and another speed from another source for max @ 56" + H2O and max @ 64" + H2O?

Edited June 10, 2020 by Raven109

[Legioneod]

11 minutes ago, Raven109 said:

 

Does the manual say what's the max speed at 64" for the D-22?

 

Or are we just left to use one speed from one source and another speed from another source for max @ 56" + H2O and max @ 64" + H2O?

Nearly all P-47s were identical in speeds, the main thing was the power used.

 

For instance a D-25 and D-27 were identical in prop, engine, turbo, and turbo regulator configuration,  only difference is that one ran at 56" and the other ran at 64", later on they both ran at 64".

What I'm trying to explain is that the D-27 could produce the same power as the D-25. Just because the D-27 has a higher boost does not mean it can't produce a lower boost at higher altitudes. Increasing boost wont change the previous performance capabilities, it will just allow better performance at lower altitudes.

[Raven109]

I understand what you're saying. I don't think I said anywhere that the D-27 @ 64" cannot also operate @ 56". 

 

My point is that we're trying to use speed samples which were collected from two different D-22s under different test conditions:

a. the speed which you posted for 29000ft @ 56"H2O;

b. the speed from wwiiaircraftperformance for 25000ft @ 64"H2O; (Since for this test there is a deviation at 29500ft from your posted value, I would expect to see deviations at 25000ft @ 64"H2O as well)

 

So, what I was wondering in my previous post is whether there is another source for the speed at 64"H2O @ 25000ft, other than the one from wwiiaircraftperformance? Otherwise we're using different sources for the D-22 to infer the speed curve for the D-28.

 

At the risk of repeating myself, we're mixing up data sources to come up with the values for D-28, that's all... 

[Legioneod]

1 hour ago, Raven109 said:

I understand what you're saying. I don't think I said anywhere that the D-27 @ 64" cannot also operate @ 56". 

 

My point is that we're trying to use speed samples which were collected from two different D-22s under different test conditions:

a. the speed which you posted for 29000ft @ 56"H2O;

b. the speed from wwiiaircraftperformance for 25000ft @ 64"H2O; (Since for this test there is a deviation at 29500ft from your posted value, I would expect to see deviations at 25000ft @ 64"H2O as well)

 

So, what I was wondering in my previous post is whether there is another source for the speed at 64"H2O @ 25000ft, other than the one from wwiiaircraftperformance? Otherwise we're using different sources for the D-22 to infer the speed curve for the D-28.

 

At the risk of repeating myself, we're mixing up data sources to come up with the values for D-28, that's all... 

No there are no other sources that I know of. imo it's not that big of an issue since all of the P-47 blocks share similar speeds when operating at the same boost setting. They also all share the same engine, turbo, and turbo regulator, so the power available would be identical.

 

As you can see top speeds aren't much different between the blocks. Only difference is critical altitude due to boost. D-22 is being added to the game so it's relevant imo.

56" MAP

 

64" MAP

Edited June 10, 2020 by Legioneod

[Raven109]

Kuban, autumn, 12PM

 

P-47D-28, 50% fuel, 54"@2700RPM + H2O, 29000ft (29.919") -> 262 IAS 

 

 

Is the ingame dashboard gauge showing CAS or IAS?

[ICDP]

It's IAS because the number on the HUD dashboard is identical to the cockpit panel IAS gauge.  258 mph on both here.

 

 

Edited June 10, 2020 by ICDP

[Legioneod]

35 minutes ago, Raven109 said:

Kuban, autumn, 12PM

 

P-47D-28, 50% fuel, 54"@2700RPM + H2O, 29000ft (29.919") -> 262 IAS 

 

 

Is the ingame dashboard gauge showing CAS or IAS?

IAS

421mph TAS.

 

EDIT:

So I went ahead and mapped a few D-22 points the the chart posted above. The D-22 is operating at 56" WEP 2300HP.

Notice the curve.

Speeds

5000' - 358mph

15,000' - 395mph

29,000' - 443mph

Edited June 10, 2020 by Legioneod

[Raven109]

Does the game implement CAS? If it does then IAS must be converted to CAS before going to TAS, according to the correction table from the P-47 manual

[ICDP]

Then the same would apply to all planes and other planes would be overperforming at that alt.  I must read the sources of the AHT chart showing the speed curve being almost straight from 24,500 - ~20,000ft.

[Raven109]

Well each plane has it's own correction table for IAS to CAS, so it doesn't have to be as different as it is for the 47.

[CountZero]

49 minutes ago, ICDP said:

It's IAS because the number on the HUD dashboard is identical to the cockpit panel IAS gauge.  258 mph on both here.

 

 

if inlet cowling is open to 60-70% insted 50% you can go 260mph, for some reason abow around 7km having it at 50% is not best position as it was up to that alt. But its still just few mph differance.

 

For me its not big deal as i can just go to manual rpm rais it to 2900 and its still in combat mode, and it will do 270. Even if they fined what is corect, what we have now or what is proposed, at high alts few min of flying at that settings will not make P-47 any sugnificantly better then other airplanes, you basicly fly at continuous settings all the time in it.

2 minutes ago, Raven109 said:

Well each plane has it's own correction table for IAS to CAS, so it doesn't have to be as different as it is for the 47.

Then P-47 would be overperforming at low alt if thats the case

[Raven109]

1 hour ago, Legioneod said:

IAS

421mph TAS.

 

EDIT:

So I went ahead and mapped a few D-22 points the the chart posted above. The D-22 is operating at 56" WEP 2300HP.

Notice the curve.

Speeds

5000' - 358mph

15,000' - 395mph

29,000' - 443mph

 

I'm not sure I understand, your dots are over the 65" speed curve, which means 2400HP. Are you saying that the D-22 report doesn't seem to make sense when compared to the manuals?

[Legioneod]

55 minutes ago, Raven109 said:

Does the game implement CAS? If it does then IAS must be converted to CAS before going to TAS, according to the correction table from the P-47 manual

You don't need to convert to CAS first, the conversion works fine from IAS to TAS.

 

39 minutes ago, CountZero said:

if inlet cowling is open to 60-70% insted 50% you can go 260mph, for some reason abow around 7km having it at 50% is not best position as it was up to that alt. But its still just few mph differance.

 

For me its not big deal as i can just go to manual rpm rais it to 2900 and its still in combat mode, and it will do 270. Even if they fined what is corect, what we have now or what is proposed, at high alts few min of flying at that settings will not make P-47 any sugnificantly better then other airplanes, you basicly fly at continuous settings all the time in it.

Then P-47 would be overperforming at low alt if thats the case

For me I don't really care about it being better, I just want it to be correct. Whether or not you believe what I said about the speed curve it still has the wrong manifold pressure at 29,000ft. At the very least that needs to be corrected.

Just now, Raven109 said:

 

I'm not sure I understand, your dots are over the 65" speed curve, which means 2400HP. Are you saying that the D-22 report doesn't seem to make sense when compared to the manuals?

No, I'm just saying that at 56" WEP the P-47 produces similar power/speed as it does at 65" dry.

[JtD]

Both the HUD and the indicator show CAS in game. Glad to see someone here who knows there's a difference.

 

If you look at the figures of the D 44-1 fuel report, you have to consider that it is performing pretty poorly. In particular its high altitude performance is off compared to most other tests, with a low full throttle altitude. You don't need more power for better performance, you need a better aircraft (condition). Maybe a bare metal polished one instead of one painted in standard camo. Or one fitted with a Hamilton 6507A2 prop instead of the Curtiss one, giving 5-8 extra mph. A small plus might be that it is a razorback D. They also don't say what turbo rpm they used. Not sure if you mentioned all that, because I only skimmed this last page.

Edited June 11, 2020 by JtD

[CountZero]

8 hours ago, JtD said:

Both the HUD and the indicator show CAS in game. Glad to see someone here who knows there's a difference.

 

If you look at the figures of the D 44-1 fuel report, you have to consider that it is performing pretty poorly. In particular its high altitude performance is off compared to most other tests, with a low full throttle altitude. You don't need more power for better performance, you need a better aircraft (condition). Maybe a bare metal polished one instead of one painted in standard camo. Or one fitted with a Hamilton 6507A2 prop instead of the Curtiss one, giving 5-8 extra mph. A small plus might be that it is a razorback D. They also don't say what turbo rpm they used. Not sure if you mentioned all that, because I only skimmed this last page.

So if they show CAS why devs placed wrong speeds in specs ? if you go by that its CAS then all airplanes in game are to fast.

[Raven109]

2 hours ago, CountZero said:

So if they show CAS why devs placed wrong speeds in specs ? if you go by that its CAS then all airplanes in game are to fast.

 

I haven't checked, but I suspect that the stats are showing CAS as well, they just named it IAS to avoid complicating things.

 

Because the game doesn't model errors introduced by airspeed measuring "equipment", IAS = CAS.

 

Edited June 11, 2020 by Raven109

[CountZero]

40 minutes ago, Raven109 said:

 

I haven't checked, but I suspect that the stats are showing CAS as well, they just named it IAS to avoid complicating things.

 

Because the game doesn't model errors introduced by airspeed measuring "equipment", IAS = CAS.

 

But again then how we get same numbers then when we go by logic that game shows you ias, then speeds would be wrong, but they are not if game shows you ias what we get in game is correct to what specs say when converted in tas. If your right and its cas,  what speeds you get at 300ft, 5000ft 15000ft and 24500ft for P-47 in tas ?