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FM ANALYSIS of the HSFX 4.1 P-47Ds - Printable Version

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FM ANALYSIS of the HSFX 4.1 P-47Ds - ACE-OF-ACES - 03.04.2010

FM ANALYSIS of the HSFX 4.1 P-47Ds

SUMMARY
[Image: ALL_ROC_P47.png]

[Image: ALL_TSPA_P47.png]

INDIVIDUAL TESTS
P-47D-10
P-47D-22
P-47D-27
P-47D-27 LATE

I am still working on the wirte up for the F-51D-30 REALISM RATING, but, I decided to take a break today! Wink

- armydan - 03.04.2010

I see these charts posted a lot, but i don't get how to actually read them can someone please explain?

- vtrelut - 04.04.2010

These FMs should be just identical to stock aircraft in the original game... :wink:

- BillSwagger - 04.04.2010

Actually, the stock sim climb rate is not as good as this for the late war P-47s, so i have to wonder what map you tested this on. Winter maps tend to be much more optimistic for some reason.

In any event, it is interesting to know that the sustained climb performance of the late war plane was actually pretty decent. I do think it would be tough to substantiate a 4000+ fpm climb, however, there is a test out there that validates a 5000 fpm climb for a short interval utilizing a zoom from 1500ft.
http://www.wwiiaircraftperformance.org/ ... n-zoom.pdf

It was done to compare zoom climb rates of the late D and N model.
There are two tests, one that zooms from 220IAS into a climb from 1500ft, and another that they start from 220 and zoom to 320 in level flight and then climb.
They timed the climbs at 5000, 8000, and 10,000ft.

The difficult thing about making such comparisons in Il2 is that indicated air speeds are universal in game, where in reality they are all not exactly the same.




Bill

- ACE-OF-ACES - 04.04.2010

vtrelut Wrote:These FMs should be just identical to stock aircraft in the original game... :wink:
And they are..

But there are new P-47s in the works

And when they are released I will add them to this list

- ACE-OF-ACES - 04.04.2010

armydan Wrote:I see these charts posted a lot, but i don't get how to actually read them can someone please explain?
Well say you want to know what the top speed is at 15kft..

Place your finger on the LHS where it says 1.5 (that is 15,000ft), ie the Y axis (Altitude)

Than drag your finger to the RIGHT until it intesects one of the lines

For example the green one (P-47D-27)

Once your finger intersects the green line

Start moving your finger DOWN until you hit the X axis (TAS)

Under your finger is the SPEED at that alt, ie 15kft

Which looking at the graph is ~395mph

- ACE-OF-ACES - 04.04.2010

BillSwagger Wrote:Actually, the stock sim climb rate is not as good as this for the late war P-47s,so i have to wonder what map you tested this on.
No need to wonder

Just need to read Wink

Section 2.1 FLIGHT SIMULATION where it states the MAP used is the 'Flight Test Map (BBury)'

The 'Flight Test Map (BBury)' is a map that is set to STD ATM conditions, which is the conditions that all real world flight test data is converted to unless otherwise stated on/in the test data

BillSwagger Wrote:Winter maps tend to be much more optimistic for some reason.
Colder is better, which is why they allways convert the test reslts to std atm conditions

BillSwagger Wrote:In any event, it is interesting to know that the sustained climb performance of the late war plane was actually pretty decent. I do think it would be tough to substantiate a 4000+ fpm climb, however, there is a test out there that validates a 5000 fpm climb for a short interval utilizing a zoom from 1500ft.
http://www.wwiiaircraftperformance.org/ ... n-zoom.pdf
It was done to compare zoom climb rates of the late D and N model.
There are two tests, one that zooms from 220IAS into a climb from 1500ft, and another that they start from 220 and zoom to 320 in level flight and then climb.
They timed the climbs at 5000, 8000, and 10,000ft.
ZOOM testing is a whole other type of testing

It is not part of the standard test methods where a constant climb speed is maintained during the climb

BillSwagger Wrote:The difficult thing about making such comparisons in Il2 is that indicated air speeds are universal in game, where in reality they are all not exactly the same.
The real difficulty is trying to find ZOOM testing that is detailed enough to reproduce the test in the game, that and only a few planes were ever ZOOM tested.

- armydan - 04.04.2010

Oh ok, thanks a bunch ACE-OF-ACES.

- ACE-OF-ACES - 04.04.2010

armydan Wrote:Oh ok, thanks a bunch ACE-OF-ACES.
No prob!

The reverse works too

That is to say you want to know what altitude you can do 395mph at

Just this time start at the X axis, move your finger up until it reachs the green line, than move it left until you hit the Y axis, under your finger will be the altitude

Also note on some graphs there may be more than one altitude where you can reach that speed

- BillSwagger - 05.04.2010

I guess its just a point of fact, for example 320 indicated in game at 1500ft is pretty close to the planes top speed, where the actual plane may have indicated more than that at its top speed.

Also, the plane used in the test is more indicative of the D-27 than the D-27late, operating at a full fuel load and 64" manifold pressure and the N used 70 inches with nearly 2000lbs more weight.

Basically, its just a matter of how far down the rabbit hole you want to go before you realize that Oleg may have been pretty close, in fact, in some ways may have undermodelled it so it wasn't such an uber plane.


Bill Smile

- ACE-OF-ACES - 05.04.2010

BillSwagger Wrote:I guess its just a point of fact, for example 320 indicated in game at 1500ft is pretty close to the planes top speed, where the actual plane may have indicated more than that at its top speed.
Not sure what your saying, but just so you know I do plot the inidcated air speed per altitude in the summary reports. I also use the same equation that IL2 uses (got it from the Java code) to calcualate it

BillSwagger Wrote:Also, the plane used in the test is more indicative of the D-27 than the D-27late, operating at a full fuel load and 64" manifold pressure and the N used 70 inches with nearly 2000lbs more weight.

Basically, its just a matter of how far down the rabbit hole you want to go before you realize that Oleg may have been pretty close, in fact, in some ways may have undermodelled it so it wasn't such an uber plane.
Maybe?

I am not a P-47 expert by any means

My only point is there is not enough info in that report to reproduce it in the game

For example, it says they 'pull into a zoom climb'..

Ok..

What angle is it that they are climbing at during the zoom?

Without that info, you can not reproduce the test

Oh sure you could try it at a few different angles

But unless you do it at all angles you wont know if the 'difference' you seeing between your test results and the real world test results is due to you not ZOOMING at the same angle they did.

All we know is that it was a fair test for the two planes, in that they were flying side by side, thus both had the same ZOOM angle, we just dont know what that angle was.

- BillSwagger - 05.04.2010

My point about the indicated airspeed is that the game uses a standard calculation that the actual instruments of an aircraft may not show. Its been discussed on another forum that the indicated readings we see in game more closely correspond with EAS. That's a whole nother topic.

what i'm saying is that if the plane in the test reaches 320 in a zoom prior to climb, that may not equate to the same speed in game. It may be faster or slower than that number, who knows. The TAS of the P-47 at that height was 345mph (at 65") but there are no indicated records. You could probably see where the D-27 top speed is in relation to indicated speed, and its probably pretty close but i'm not sure i can duplicate this climb (with the Late model, maybe)

As for the angle of climb, it doesn't need to specify, it explains they were pulled into a climb until 165ias was reached. 165 happens to be the speed at which the P-47 reaches its best angle of climb. So my guess, and logical assumption is that they climbed at the best angle of climb for the duration of the climb (Vx)

- ACE-OF-ACES - 05.04.2010

BillSwagger Wrote:My point about the indicated airspeed is that the game uses a standard calculation that the actual instruments of an aircraft may not show. Its been discussed on another forum that the indicated readings we see in game more closely correspond with EAS. That's a whole nother topic.
Basically the IAS in IL2 has no instument error, thus in IL2 IAS is equal to CAS

BillSwagger Wrote:what i'm saying is that if the plane in the test reaches 320 in a zoom prior to climb, that may not equate to the same speed in game. It may be faster or slower than that number, who knows. The TAS of the P-47 at that height was 345mph (at 65") but there are no indicated records. You could probably see where the D-27 top speed is in relation to indicated speed, and its probably pretty close but i'm not sure i can duplicate this climb (with the Late model, maybe)
Roger without knowing the angle they settled at in the ZOOM you will be very hard pressed to recreate this real world test in IL2

BillSwagger Wrote:As for the angle of climb, it doesn't need to specify, it explains they were pulled into a climb until 165ias was reached. 165 happens to be the speed at which the P-47 reaches its best angle of climb. So my guess, and logical assumption is that they climbed at the best angle of climb for the duration of the climb (Vx)
Actully it does need to be specified

If you were planing on trying to reproduce the test in IL2

In that it is most likly the angle was changing during the ZOOM

That is to say due to the extra 'e' due to the higher starting speed they could climb at a larger/steeper angle

That is to say they ZOOMED until the speed was reduced to the best climb speed

But during the ZOOM they were most likly climbing at a higher angle than the angle they would have at the best climb speed

Why?

Because they could! Wink

Keep in mind the goal here was to see how a ZOOM climb improved the time to climb (TTC) number from a standard constant speed (best climb speed) climb

At least until the speed slowed down to the 'best climb speed' of the plane

At which point they carried on as if it was a normal constant speed (best climb speed) climb test.

In short

Once they used up all the extra 'e' they were force to climb at the best climb speed

- BillSwagger - 06.04.2010

ACE-OF-ACES Wrote:But during the ZOOM they were most likly climbing at a higher angle than the angle they would have at the best climb speed

Why?

Because they could! Wink

I disagree, although the angle used is likely to have a small margin of error through out the climb but the pilot is going to aim for the angle at which the plane climbs best.

Every plane has an optimum angle of climb, and its based on a number of factors. I can't follow the logic that they climbed at steeper angles because they could, when by design the plane climbs more efficiently at its best climb angle. An experienced pilot doesn't blow all his energy trying to get the most height in the shortest time, he does it so he can get the most height for the energy he has. That's going to be at the best climb angle which coincides with the 165 IAS speed at a WEP setting, in this case.

Its also a rather uniform test, with two planes climbing at the same angles and duplicated twice to determine the results of a climb from a fast cruise, and a climb from a zoom.

Bill

- ACE-OF-ACES - 06.04.2010

BillSwagger Wrote:I disagree, although the angle used is likely to have a small margin of error through out the climb but the pilot is going to aim for the angle at which the plane climbs best. Every plane has an optimum angle of climb, and its based on a number of factors. I can't follow the logic that they climbed at steeper angles because they could, when by design the plane climbs more efficiently at its best climb angle.
I think you might be confusing 'best clmib speed' with 'best climb angle'?

Props tend to have a best climb speed that does not change much if any during a standard rate of climb test

That is to say the speed remains constant during the climb from sea level to max altitude

What does change..

And must change!

If the speed is constant is the climb angle

For example

At lower altitudes the best climb speed for the 38 is around 165mph

At higher altitudes the best climb speed for the 38 is around 165mph

What changes from sea level to 30kft is the pitch angle (and yes AoA angle)

You start of climbing at a steep angle at lower altitudes and end up climbing at a very shallow angle at higher altitudes.

Thus pilots were very use to the idea of changing the climb angel as they climbed

BillSwagger Wrote:An experienced pilot doesn't blow all his energy trying to get the most height in the shortest time, he does it so he can get the most height for the energy he has. That's going to be at the best climb angle which coincides with the 165 IAS speed at a WEP setting, in this case.
It depends

If your goal is to try an improve the time to clmib values than you would convert your excess energy in such a way as to minimise the time to alt

If that is not your goal than you are wanting to keep some excess energy in reserve for some 'other' reason.

In short you and I could come up with dozens of combat reason to keep some in reserve, but if your goal is that of that test than they were trying to see how they could improve the time to clmib values by zooming as high as they could in the least amount of time.

BillSwagger Wrote:Its also a rather uniform test, with two planes climbing at the same angles and duplicated twice to determine the results of a climb from a fast cruise, and a climb from a zoom.
The same 'unknown' angle to be more accurate Wink