Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Batz on April 18, 2003, 03:25:10 PM
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Sonder - Notleistung mit A Lader als Bodenmotor
I know this is some sort of "Special Emergency power "
Its in reference the 190d9. Is this a special low altitude compressor gear? or something else?
Also does anyone have any info on a low pressure Mw50 system referred to as the "Oldenburg system"?
There was also a system referred to as "Ladedruckssteigerungs-Rüstatz". Apparently it increased the power of Jumo 213A from 1750 to 1900 without MW50 or GM-1.
TIA
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Hi Batz,
>Sonder - Notleistung mit A Lader als Bodenmotor
Water-methanol injection ("Sonder-Notleistung") for a Jumo 213 with the 213A supercharger ("A-Lader") using high-altitude gear at low altitude ("Bodenmotor"). Yields 2140 HP at sea level.
Regards,
Henning (HoHun)
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Originally posted by Batz
Sonder - Notleistung mit A Lader als Bodenmotor
I know this is some sort of "Special Emergency power "
Its in reference the 190d9. Is this a special low altitude compressor gear? or something else?
TIA
I tend to believe it`s kind of a cropped Supercharger gear like on the cropped SpitV LFs... I think they were running the SC less hard which meant they were using less power to drive the SC from the engine, and this would also explain why the high alt. performance suffered in this configuration.
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Hi Isegrim,
>I tend to believe it`s kind of a cropped Supercharger gear like on the cropped SpitV LFs... I think they were running the SC less hard which meant they were using less power to drive the SC from the engine, and this would also explain why the high alt. performance suffered in this configuration.
If the supercharger wheel was cropped, an entirely new power curve would result, but from the speed curve you can see that it smoothly approaches the normal speed curve above full throttle height so it's definitely not that.
But you've pointed out an important aspect: Maybe the (very) slight reduction in altitude power we're seeing is the result of a lower compression ratio implemented by using shorter piston tops?
This would allow the use of slightly higher boost pressures at low altitude at a slight reduction of high altitude power. At least the latter is evident from the graph, the former is hidden by the much larger increase gained from MW50 use.
Regards,
Henning (HoHun)
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Originally posted by HoHun
Hi Isegrim,
If the supercharger wheel was cropped, an entirely new power curve would result, but from the speed curve you can see that it smoothly approaches the normal speed curve above full throttle height so it's definitely not that.
But you've pointed out an important aspect: Maybe the (very) slight reduction in altitude power we're seeing is the result of a lower compression ratio implemented by using shorter piston tops?
This would allow the use of slightly higher boost pressures at low altitude at a slight reduction of high altitude power. At least the latter is evident from the graph, the former is hidden by the much larger increase gained from MW50 use.
Regards,
Henning (HoHun)
Hi HoHun!
First I must clarify what I wanted to mean. I belive they have reduced the 2ns SC speed gear ratio to a lower level, which meant the supercharger was running on a lower RPM compared to the previous configuration. This is what is called "cropped SC" in English, right? Maybe I used wrong term.
This would result in lower power drain from the engine towards the SC. At low altitudes where less supercharging is needed to keep constant boost, this increases power in a way by conserving more power to the engine.
At higher altitudes this reduced supercharging capacity isn`t enough to keep up power.
I am fairly sure that they did something to the supercharger.. Otherwise why would they refer to a the "A"-Supercharger [configured] as a low altitude supercharger? (If my translation is correct.
In any case it`s clear from the curve that there is only ONE supercharger speed. The Bodenlader-speed curve has no stops or breaks, it`s a straight line, unlike the others, indicating contstant power (up to 3500m).
I think it`s is likely to be that they probably disabled the 1st supercharger speed (which saved some power drain already), and changed the 2nd SC gear to a lower RPM (less power drain again).
So the additional speed is due to the power saved at lower altitudes with reduced supercharging. That seems a simple enough explanation, without too much complication. But it`s maybe possible that additional or other ways were used... it`s hard to say for sure w/o having some hard evidence, we can only speculate.
As for your idea, would it be technically possible to increase powers with B-4 fuel, with reducing the CR, without premature detionation?
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Originally posted by VO101_Isegrim
First I must clarify what I wanted to mean. I belive they have reduced the 2ns SC speed gear ratio to a lower level, which meant the supercharger was running on a lower RPM compared to the previous configuration. This is what is called "cropped SC" in English, right? Maybe I used wrong term.
Yes, very much so the 'wrong term'.
"Cropped" does not mean a different SC gear ratio but that the diameter of the SC impellor was reduced.
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Hi Isegrim,
>I belive they have reduced the 2ns SC speed gear ratio to a lower level, which meant the supercharger was running on a lower RPM compared to the previous configuration.
This is entirely impossible as above 9 km altitude, the speed of the Bodenmotor-equipped D-9 equals that of the standard D-9 with B4 and MW50. The Bodenmotor D-9 is just a few km/h slower than the standard D-9, and this difference is just too subtle for anything like a different supercharger.
(After looking at that curve again, I don't believe in different compression either.)
>Otherwise why would they refer to a the "A"-Supercharger [configured] as a low altitude supercharger? (If my translation is correct.
Actually, "Bodenmotor" merely means that the engine's full-throttle height is equivalent to sea level. "A"-type supercharger means it's the supercharger of the Jumo 213A.
>This is what is called "cropped SC" in English, right? Maybe I used wrong term.
The term "cropped supercharger" was coined for the Spitfire LF V. Not only did it use a smaller supercharger wheel, it was actually just the standard wheel machined down to a smaller diameter. I'd imagine a wheel designed from the outset for the smaller diameter would have been more efficient, so "cropped" had a slightly negative connotation.
>In any case it`s clear from the curve that there is only ONE supercharger speed.
We certainly agree on this point! :-)
>As for your idea, would it be technically possible to increase powers with B-4 fuel, with reducing the CR, without premature detionation?
Even without reducing the compression ratio :-)
The Jumo 213A-1 power chart shows that special emergency power (with MW50, yielding 2140 HP at sea level) drops to the same level as take-off and emergency power (1900 HP at sea level) at 5.2 km altitude. That's just the altitude at which the speed curves intersect.
For some reason, the 1900 HP D-9 has a 300 m higher full-throttle height so that it's 12 km/h faster at 5.5 km. Without this difference, both speed curves obviously would be equal above 5.2 km.
Regards,
Henning (HoHun)
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The "Bodenmotor" horsepower output is definitly around 2400, maybe even 2600. the 2140hp output is for the ~615km/h curve. I really can´t understand why you (Hohun) bring up over and over again that the Bodenmotor is for the standard 213A engine with mw50. You know that it isnt true
niklas
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Wasn`t that 2240 HP at SL with MW-50+B-4? At least that`s what my power curve shows. Do you have a different one?
I did some calculations with my emprical formula, if everything else is the same, you need 2525 HP to go 640km/h instead of the 615 km/h at 2240HP with C-3.
BTW, another question about that curve: if B4+MW50 yields the same power as C3 alone, why is the C-3 curve a little faster at the whole altitude range? Maybe the bombrack is present only on B4+mw50?
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Hi Niklas,
>The "Bodenmotor" horsepower output is definitly around 2400, maybe even 2600. the 2140hp output is for the ~615km/h curve. I really can´t understand why you (Hohun) bring up over and over again that the Bodenmotor is for the standard 213A engine with mw50. You know that it isnt true
Since I know you're usually well informed, how about contributing some information to prove your point? :-)
Regards,
Henning (HoHun)
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Hi Isegrim,
>Wasn`t that 2240 HP at SL with MW-50+B-4? At least that`s what my power curve shows. Do you have a different one?
No, I'm using the same curve. But remember that we're using only high gear for the supercharger - 2240 HP are the result of using low gear, while the high gear branch only yields 2140 HP at sea level.
>I did some calculations with my emprical formula, if everything else is the same, you need 2525 HP to go 640km/h instead of the 615 km/h at 2240HP with C-3.
Your assumption is that the Fw 190D-9 actually needs 2240 HP to get 615 km/h.
However, the Fw 190A-5 according to US tests needs only 1660 HP to get 549 km/h. With 2240 HP, it would get to 608 km/h despite its much larger frontal area which has a large impact on speed at sea level.
Accordingly, the Fw 190D-9 with its much smaller frontal area doesn't need 2000+ HP to get to 600+ km/h.
And it shouldn't be forgotten is that the Jumo 213 yielded considerable amounts of exhaust thrust. I'd estimate the Jumo 213A gave (at least) 125 kp at 2140 HP. These 125 kp are worth around 370 HP in additional shaft horsepower at 620 km/h, so we're actually talking about a 2510 HP aircraft.
>BTW, another question about that curve: if B4+MW50 yields the same power as C3 alone, why is the C-3 curve a little faster at the whole altitude range? Maybe the bombrack is present only on B4+mw50?
Does B4 + MW50 yield the same power as C3 alone? I know this was said for the DB605 series engines, but I'm not so sure it's true for the Jumo 213 as well.
Regards,
Henning (HoHun)
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Originally posted by HoHun
Hi Niklas,
Since I know you're usually well informed, how about contributing some information to prove your point? :-)
Regards,
Henning (HoHun)
Isegrim understood. You not. We have gone through this over and over again. Don´t come with pixel counting. Just calculate like Isegrim. Again, he understood. And start from the well known 1750ps curve. Or get the pressure from the reduced critical altiutude.
niklas
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Hi Niklas,
>We have gone through this over and over again.
By coincidence, I just found one of your posts on my hard disk that's two years old - you shared my opinion about the D-9 power back then.
Obviously, something caused you to change your mind since then. If you'd explain what that was, you might be able to convince me :-)
>Just calculate like Isegrim. Again, he understood. And start from the well known 1750ps curve.
If you have a speed curve that's labeled "1750 PS", please post it :-)
If "well-known" means that you guess it's 1750 PS, you might be falling into the same trap as Isegrim: If your guess is wrong, your conclusion is wrong, too.
>Or get the pressure from the reduced critical altiutude.
Could you provide an example for that?
Regards,
Henning (HoHun)
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Hohun, the 1750/1780PS curve is the one labelled 1 on the chart, this one match exactly with the other data i have for 1750PS.
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Hi Butch,
>Hohun, the 1750/1780PS curve is the one labelled 1 on the chart, this one match exactly with the other data i have for 1750PS.
Could you post the other data then so we could verify the absolute power requirement?
Bbury's data from Focke-Wulf performance calculations shows that the Fw 190D-9 with Jumo 213A-1 achieves 611 km/h at sea level at 1925 HP power:
http://jagdhund.freeyellow.com/FW190D-9/D9speedWeb_01.jpg
http://jagdhund.freeyellow.com/FW190D-9/D9speedWeb_02.jpg
http://jagdhund.freeyellow.com/FW190D-9/D9speedWeb_03.jpg
Regards,
Henning (HoHun)
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Originally posted by butch2k
Hohun, the 1750/1780PS curve is the one labelled 1 on the chart, this one match exactly with the other data i have for 1750PS.
It also goes along with the test report of the D9 with DB603 engine (the first D9), which also reached 570km/h with 1700-1750PS
And there´s no way to gain 70km/h with just 450ps. Your prop efficiency is already dropping, you´re in a speed region where the air in local parts reach Mach1. You need a lot more power.
niklas
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In those charts no power setting is given that describes the Sondernotleistung.
What is given is the speed (indicated) for Notleistung on the first chart. Again, aroung 570km/h. So the 2nd chart shows the power setting for mw-50, which is ~2100-2200PS.
Those docs are the background for the speed chart going around, and they confirm my opinion that the speed chart is mainly a calculated one, which may base on real flight data and experience values, but is not the direct result of a flight test. Anyway the values are not optimistic.
The speed chart nevertheless is dated April45 and at this time no 1900ps power setting was used anymore except for AG engines up to 500m (emergency)
Please understand finally that the speed chart and those table do NOT show a 1900PS power curve. Or try to convince me how you want to gain 45km/h (from 570 to 615) with just 200PS-300PS more output.(1700-1900). Unpossible....
niklas
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Hi Niklas,
>In those charts no power setting is given that describes the Sondernotleistung.
On page 1, a combination of speed and power is given: 611 km/h at 1925 HP.
If these 1925 HP are "Sondernotleistung" or some other power rating is irrelevant - it shows that the Fw 190D-9 reaches more than 600 km/h on less than 2000 HP.
>Please understand finally that the speed chart and those table do NOT show a 1900PS power curve.
It's in the Focke-Wulf documents: 611 km/h - 1925 HP. Do you have any other explanation than "1900 HP power curve"? :-)
>Or try to convince me how you want to gain 45km/h (from 570 to 615) with just 200PS-300PS more output.(1700-1900). Unpossible....
Two mistakes: You keep using a reference point that you don't have any absolute values for, and you keep forgetting the exhaust thrust that becomes more and more important at higher speeds.
>The speed chart nevertheless is dated April45 and at this time no 1900ps power setting was used anymore except for AG engines up to 500m (emergency)
The speed chart I have is dated 11.3.1945, the same as page 1 of the speed calculations showing the 1925 HP for 611 km/h combination.
There are two speed curves in the chart with near that speed, "Sondernotleistung mit Ladedruckerhöhung, MW50 und 1,8 ata" (606 km/h) and "Sondernotleistung" (615 km/h). These are curves 2 and 4.
Regards,
Henning (HoHun)
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This is indeed calculated and quite optimistic data...
I have some real test data of WkNr 210043 taken at 4250Kg @1900PS/1.50ata/3250rpm showing a speed of 560km/h @SL and 660km/h @6500m.
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Butch, any guesses on what the heck this Bodenlader thing could be? Do you know anything on it`s operational service (if there is such)? Or it is just plain mistery?
Totally OFF: Can you tell me what`s the radiator position in the K-4 test with 24.5m/sec climb rate ? I guess it`s half-open, can you confirm that?
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Hi Butch,
>I have some real test data of WkNr 210043 taken at 4250Kg @1900PS/1.50ata/3250rpm showing a speed of 560km/h @SL and 660km/h @6500m.
That's awfully slow, considering the radial-engined Fw 190A-5 achieved 549 km/h @ sea level and 668 km/h @ 7200 m/661 km/h @ 6500 m (data from US tests).
Since the radial engine has an obvious drag disadvantage, less power (1660 HP) and less exhaust thrust (ca. 65 kp), the D-9 with 1900 HP and ca. 110 kp should obviously be quite a bit faster unless something else is wrong with it.
Could it be that your test is from the initial stage of introducing the Fw 190D-9 into service? At that time, there were complaints that the aircraft didn't perform any better than the A-series, but as far as I know, these had been solved by 1945. Accordingly the question is: Can you tell us more about this source (or better yet, post the report somewhere :-)?
One discrepancy that can't be explained by a possible date difference is that 1900 HP are reached at 1.50 ata in your report, while according to Bbury's report, it takes "Ladedruckerhöhung mit MW50 und 1.80 ata" to reach a speed in the 1900 HP range.
Regards,
Henning (HoHun)
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Es ist mir ganz egalwas mit dem bodenmotor loss ist.
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The 1900PS setting was achieved with B4 w/o MW-50, and the 190D-9 was tested in combat condition meaning no polish/no fill.
The 4th curves on Bryan's report is not for 1900PS !!! it's the one for 2100/2150PS@1.78ata@3250rpm@SL (Sonder Notleistung).
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Hi Butch,
>The 1900PS setting was achieved with B4 w/o MW-50, and the 190D-9 was tested in combat condition meaning no polish/no fill.
The effect of filling/polishing was maybe 10 km/h, that's not enough to explain the difference.
>The 4th curves on Bryan's report is not for 1900PS !!! it's the one for 2100/2150PS@1.78ata@3250rpm@SL (Sonder Notleistung).
Actually, if you look at page 1 of the speed calculations:
http://jagdhund.freeyellow.com/FW190D-9/D9speedWeb_01.jpg
you'll see that the necessary power for 611 km/h is listed as 1925 HP. (First line of the table "Horizontalgeschwindigkeiten - Schwebeleistung im Schnellflug" - 'horizontal speeds - equilibrium power for high-speed flight').
Regards,
Henning (HoHun)
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Henning, the numbers Butch mentions fit well into the picture.
Also if you compare them to the flight test of Kurt Tank in the FW190D9.
Tank gives 580km/h SL and 686 km/h at 6,6km.
And i am pretty sure Tank flew a 1900PS D9 that was polished to a high glose.
Also Pilots of JG54 mentioned that high polish increased speed by about 20 km/h.
This would fill the gap.
Even if it were only 10 km/h as you mentioned, the differences between WK-Nr. 210043 and Tanks D9 could well come from series production variation.
I have read through the entire thread now.
I would like to add the following, according to my researches i have to share the opinion of both Niklas and Butch2K.
640 km/h need more power that 2240PS.
The chart Fw5232 has no speedcurve for 2240PS.
I am pretty sure the different D9 version would have performances compared to this short summarization.
Early D9 (or 1750PS D9)
Speed:
~550km/h SL
~650km/h 6.6km
Climb
~17 m/s SL
Mid D9 (or 1900 PS D9)
Speed
~570km/h SL
~685km/h 6.6km
Climb
~ 21 m/s SL
Late D9 (2100PS D9)
~600km/h SL
~690km/h 5.5km
Climb
greater 21m/s,
i assume something like 24m/s cause increased horsepower has much more
effect on climbrate than on topsspeed
This would mean between early D9s, which are just slighty better than the
A8, and late D9s there is such a great performance difference as i.e. between
Spit IX and Spit XIV.
I am not completely sure about the climb rates, as i don't have the knowledge to calculate anything in aerodynamics.
Climbrate for 1900PS might well be just 19-20 m/s and for 2100PS something like 21-22m/s.
Also a look to the JUMO213 development history might bring some light on which poweroutput the curve of speedchart Fw5232 are based:
Designation Take off/Emergency power KW(PS) Comments
A-1 1285(1750) Zweiganglader
AG 1395(1900) Sonderausführung
B-0 1470(2000) C3-Kraftstoff
C-0 1285(1750) für Motorkanoneneinbau
C-1 1285(1750) Serie Sep. 1944
E-0 1375(1870) Höhenmotor, C3-Kraftstoff
E-1 1285(1750) Höhenmotor, Serie 1944
EB 1470(2000) Sonderausführung
F 1505(2050) Höhenmotor
J 1645(2240) Projekt mit 4 Ventilen
T 1285(1750) Projekt mit Abgasturbolader
S 1665(2400) Projekt für niedrige Volldruckhöhen
After finding this i think we can finally assign all 5 speedcurves of the
Fw5232 speedchart to a certain JUMO213 Version.
I think it will be like this:
Curve #1,#4 & #5 are for a JUMO213AG with MW50
Curve #2 is for the "Sondernotleistungs" setting of a JUMO213B-0
Curve #3 is for the projected JUMO213S, were the comment roughly translated
means "project for low full boost pressure altitude"
As document Fw5232 is a calculated chart, it would be logical to included
projected developement stages of the JUMO213, to show which performances can be
expected in the future.
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You've just said it Hohun, it's a calculated power.
Carefully look at the document, the power required is calculated according to the known aircraft parameters and speeds. That means that the speed curve have been drawn before the necessary power have been calculated. The curves probably comes from other test data.
The document probably served as a preliminary analysis to determine the delta between actual required power and calculated power.
I have seen the complete Jumo curves with power at height vs ata and fuel, and i can assure you that B4+MW-50 @ 1.78ata produce 2100/2150PS @SL not 1925.
Here is part of what i'm authorized to post here :
(http://www.allaboutwarfare.com/files/pictures/aviation/ww2/germany/fw190/d9/fw190d9-db603-04.jpg)
(http://www.allaboutwarfare.com/files/pictures/aviation/ww2/germany/fw190/d9/fw190d9-db603-05.jpg)
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Hi Lutz,
>I would like to add the following, according to my researches i have to share the opinion of both Niklas and Butch2K.
I can see how you arrive at the belief. However, the problem is, you don't have any hard numbers.
1925 HP for 611 km/h is a hard number.
>S 1665(2400) Projekt für niedrige Volldruckhöhen
Actually, the "Bodenmotor" is labeled "mit A Lader", so it's clear it has the Jumo 213A supercharger. If you look at the speed curves, it shows no loss in power above 8 km compared to the standard Jumo 213A with B4.
If the full throttle height of the Bodenmotor appears low, it's just because the boost is very high - at lower boost, its full throttle height is that of a normal 213A at the same boost.
>the Fw5232 speedchart
Fw 5232 is just the graph paper's ID :-)
Regards,
Henning (HoHun)
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Hi Butch,
Your charts are interesting because they put an absolute power number on the speed graph.
However, it would be important to know the date of the report - as I mentioned, the Fw 190D-9 didn't perform as expected initially, and the Werknummer quoted in the report seems to be an early one if I remember correctly.
>Carefully look at the document, the power required is calculated according to the known aircraft parameters and speeds.
By 1945, the aircraft parameters were known pretty well :-)
>The document probably served as a preliminary analysis to determine the delta between actual required power and calculated power.
Actually, the document served to calculate level top speeds and climb rates. The speeds are the results of the calculations, not the input.
>I have seen the complete Jumo curves with power at height vs ata and fuel, and i can assure you that B4+MW-50 @ 1.78ata produce 2100/2150PS @SL not 1925.
Are you sure that boost is in these curves? I have the Jumo 213A and E curves, too, and they don't specify any boost pressures - as Jumo didn't control boost but charge mass, it made sense to omit the (misleading) boost figures.
But as I said, I consider these values contradictory, too.
Regards,
Henning (HoHun)
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@Henning: We don't know which modifications the JUMO213S would have compared to the JUMO213A. It might well be that it just was that "Bodenmotor mit A-Lader". As it was a project for low alts, it would make sense to use the A-Lader instead of the E-Lader for high altittude. Lets simply say it this way. We both can't be sure what is right, as a few parts of the puzzle are still missing.
And i tend to be a little cautious not to overestiminate the performance.
Btw this seems to be the same method Rechlin used, i.e. in flightest of WK-NR. 006 they achieved topsspeeds that varied by 10km/h and for the display of speed/climb graphs the lowest attained topsspeed was used, not the highest.
@Butch: Am i right if i think, that the little dots and crosses are the data from flight tests and the lines are than drawn over them?
Edit: About Fw5232, i know its the paper ID, but its easier to type Fw5232 than always "the speedchart from Bryans Website ;)
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Originally posted by HoHun
1925 HP for 611 km/h is a hard number.
And it isn´t unrealistic too. But you forget that this is the power that is necessary to pull the aircraft through the air and not the engine output
Just multiply engine power * prop efficiency
2240 * 0.8 = ~1800Ps
OR assuming that at those speed prop efficiency is already lower.
2240*0.7 = 1570 PS
adding exhaust thrust power, around 150kg
150kg*9.81*611/3.6 = 250kw = 300PS
1570+300 = ~1900PS
Not bad for a rough calcualtion eh? :)
Here you are....
niklas
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Yes you are right Naudet, it's taken from actual flight data and it isn't calculated data.
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@Niklas: Is it possible that you contact me at naudet@jg301-wildesau.de , i would have a few questions regarding calculations.
@Butch: Did you get my email?
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Originally posted by butch2k
Yes you are right Naudet, it's taken from actual flight data and it isn't calculated data.
Hmm the effect of polishing and filling is pretty high accoding to your charts isn´t it? I mean the clean 190 is 20km/h faster with COMBAT power (2500rpm) compared to the dirty with EMERGENCY power (2700).
I remember a statement from a mechanic that was published over at the luftarchiv forum. It´s definitly deleted now unfortunatly due to this #&%?~!! I remember that he wrote that they were ordered to polish the Doras they were responsible for all day long. They must have looked like mirrors.
niklas
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Yes Naudet i got it, i'll send the requested data tonite. Niklas could you email me please, i have some goodies for you as well.
I'm not that much surprised buy the effect of polishing/filling, i have seen reports where aircraft under that conditions were 40km/h faster than ones in usual combat conditions.
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Yes i am pretty sure polishing had a consideralbe effect on a planes performance.
I also tend to believe that most USAAF/RAF planes did not match the factory specs, once they were a couple of days in action.
Especially a P51 would have to suffer from bad combat conditions with its laminar wings.
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Hi Niklas,
>Just multiply engine power * prop efficiency
Hm, you may be right about that ... let's see - assumed propeller efficiency 0.75:
1925 HP/0.75 = 2570 HP
The result is shaft-equivalent power, so if we've got 2240 HP at the propeller shaft, we'd have to get 330 HP from thrust - that's about 150 kp.
I can check that using the climb chart:
(Pclimb + Plevel)/0.75 = Peq
(1253 HP + 460 HP)/0.75 = 2325 HP
That leaves only 85 HP from thrust, and as one would expect thrust power to halve at half the speed (300 km/h), that sounds about right.
So maybe you've found the solution, and the D-9 really gets only 611 km/h from 2240 HP.
That would indicate a serious deterioration in aerodynamic quality from the Fw 190A-5, though. Some of it may be attributed to carrying a bomb rack - the Fw 190A-8 seems to have lost 12 km/h at 544 km/h at sea level, and the D-9 speed chart assumes that a bomb rack is carried. However, the figures still make it seem as if the D-9 wasn't much of an improvement over the A series aerodynamically.
Regards,
Henning (HoHun)
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Having seen some German prop efficiency curves, consider efficiency as toping at 125m/sec @ SL with a value of 0.83, and at 160 m/sec @VH with a value of 0.78.
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Hi Butch,
>I'm not that much surprised buy the effect of polishing/filling, i have seen reports where aircraft under that conditions were 40km/h faster than ones in usual combat conditions.
That seems like too much to stem from filling/polishing alone.
This is from a US Navy F4U test:
"The principal changes in drag included sealing and fairing the wing fold hinge line, removal of the tail hook, carefully fitted cowling, and a faired and smoothed, but not polished skin.
The total speed gain, as a result of drag reduction alone, in this airplane is estimated to be 8 MPH at the airplane upper critical altitude."
As NACA Report 824 indicates that polishing has little effect on an aerodynamically smooth surface - though it helps to maintain a (filled and sanded) smooth surface - I'd say that you won't get much more than these 8 MPH in total, and not all of this is due to surface finish.
It was compared to another F4U (with a different propeller so conclusions aren't perfectly safe), but the smoothed-skin Corsair displayed a speed advantage of hardly 4 MPH above upper critical altitude to the other Corsair "with a surface finish in rather poor condition but with the tail hook removed." The "rather poor" surface finish was considered typical for aircraft "after moderate service".
I've read several anecdotes about surface polishing, which is usually attributed with much greater effect than this, but one episode told by a German crewman pointed out that after all the work they had spent on the aircraft, they were quite disappointed that the results fell far short of their expectations.
Maybe the 40 km/h were the difference between a factory-fresh aircraft and a combat veteran? If aerodynamic shape is the determining factor, one over-G pullout might suffice to distort the skin enough for such a large difference even if the surface still appears smooth to the unarmed eye.
Regards,
Henning (HoHun)
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on a 109 polishing/filling decreased Cw by 0.004, as a comparison adding MG151 gondolas added 0.001 to Cw.
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Hi Butch,
>on a 109 polishing/filling decreased Cw by 0.004, as a comparison adding MG151 gondolas added 0.001 to Cw.
Hm, that's difficult to evaluate because the addition of gondolas not only increased the Cw, but also added frontal area (which filling/polishing didn't).
Do you have an absolute value for the Me 109's Cw?
Regards,
Henning (HoHun)
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cw for aircraft is always based on wing area, not frontal area. Frontal area is for cars afaik
niklas
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Henning,
honestly i think the US numbers are a bit high.
Even in Kurt Tanks personal memory the A5 managed only speeds of 530-540km@SL and around 640 km/h@6,6.
Do you have a copy of that US report?
I would be interested to look into it.
Maybe the weapons were removed prior to the tests, which would reduce weight and might explain the "extra" boost that A5 seemed to have.
About Cw numbers, i have a some for the FW190, but none for the Bf109.
But they are on the other PC. I will post them later.
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Hi Niklas,
>cw for aircraft is always based on wing area, not frontal area. Frontal area is for cars afaik
Wouldn't that mean filling/polishing would have four times the impact of gun gondolas? As the gondolas subtracted at least 15 km/h at full throttle height, that would suggest a 60 km/h loss due to failure to fill/polish, which certainly is too high.
If filling/polishing would have had these extreme effect, there'd been no matte camouflage paint in WW2. From what I know, just this type of paint was pretty much the standard though.
Regards,
Henning (HoHun)
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Hi Lutz,
>Maybe the weapons were removed prior to the tests, which would reduce weight and might explain the "extra" boost that A5 seemed to have.
The weapons were removed, but the aircraft was ballasted to get it to the correct weight. Compared to the D-9, the drag of the wing root guns was absent, and the A-5 didn't carry a bomb rack either.
A four-cannon A-5 would have lost some more speed - any disturbance in the wing's leading edge is a bad thing. (I'd imagine the wing root guns weren't as critical as they were in the interference drag region anyway.) The altered cowl lines for the Fw 190D-9's MG131 guns are another source of drag not present on the A-5.
Other than that, I'd say the A-5 numbers are realistic. I think I've seen British figures for the A-4 posted on this board that agreed quite well, though unfortunately I've been unable to find the report in question on the internet or in my books.
(Early prototypes of the Fw 190 series actually passed the 700 km/h speed mark - guns, armour, more weight, a bigger wing, operational equipment, etc. had a big impact on speed! Or maybe these prototypes were the only Fw 190s ever to be filled/polished ;-)
Regards,
Henning (HoHun)
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Sorry Henning, but i think there is no evidence that supports this:
>Early prototypes of the Fw 190 series actually passed the 700 km/h speed mark - guns, armour, more weight, a bigger wing, operational equipment, etc. had a big impact on speed!
I have now studied many books and sources, memories of Kurt Tank and Pilots but an early FW190 prototype that passed 700 km/h i never heard of.
The V1 was astonishing fast on its 1st appearance, passing 500 km/h at SL and 600 km/h at full boost altitude.
But the 700 km/h mark was way beyond the capabilities of the early prototypes.
I have looked into my dragchart for the FW190 Series, its bad but its starts with the FW190A8.
But i believe the cowl gun will not make such a big difference.
I assume that the US-tested A5 was a "clean" A5 fighter, meaning it had just the inner wing guns and the cowl guns and no ETC racks.
Than the plane would be something like 250-300kg lighter than a D9 with a takeoff weight of 4250-4300kgs.
That might explain why it comes so close.
Btw has anyone managed to get a hand on the D9 evaluation of the USAAF or the RAE?
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Hi Lutz,
>But the 700 km/h mark was way beyond the capabilities of the early prototypes.
I've got a page from Arado here that quotes 714 km/h for a BMW801-engined prototype with small wing and just 3200 kg take-off weight. The same information is repeated in the shape of a Flugzeug-Kennblatt for the Fw 190V5k in Hermann et al.'s "Fw 190 A".
Since Arado tested the A-2 and arrived at a 650 km/h top speed with 3778 kg and the big wing, the prototype speed doesn't strike me as exaggerated, regardless of whether it's calculated or flight test performance. The 3200 kg small-wing prototype has more of a record plane than of a fighter, so its speed is mostly irrelevant anyway.
(For perspective: Gollob's test of an operational A-2 versus a Me 109F-4 resulted in a superiority of the latter above 4500 m. That means the A-2 lost roughly 30 - 40 km/h compared to the Arado report. The BMW801C gave a lot of problems in frontline service, and obviously it had to be run at reduced power.)
>I assume that the US-tested A5 was a "clean" A5 fighter, meaning it had just the inner wing guns and the cowl guns and no ETC racks.
Than the plane would be something like 250-300kg lighter than a D9 with a takeoff weight of 4250-4300kgs.
The A-5 had no guns or bomb racks at all, but weight was adjusted to 3875 kg which seems correct for a 2-cannon A-5. Focke-Wulf gave the weight of a 4-cannon A-5 (with 90 rounds per MG FF) as 4000 kg and the top speed as 656 km/h. (The Focke-Wulf speed chart isn't that accurate - it's the one meant as example for the compressiblity error of the airspeed indicator. It has been discussed on this board before.)
Regards,
Henning (HoHun)
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Hi again,
>honestly i think the US numbers are a bit high.
The USN did a comparative trial of the same Fw 190A-5 against the F6F and the F4U, and the numbers match the detailed report pretty good.
They were flying the A-5 abreast with the F6F-3 and the F4U-1D, and the F6F-3 was slower at all altitudes except at sea level (where it was equal). The F4U-1D was faster below 15000 ft and slower above.
The USN reports says they weren't interested in absolute speeds but only in the speed difference and accelerated for just 2 min (which isn't enough to reach top-end speed). I'd rather trust the detailed report, but the USN report matches it quite well anyway.
Regards,
Henning (HoHun)
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If weight of the A5 was just around 3900kg i agree that the number seem to be correct.
And those charts about the protoypes seem to be very interesting.
If V5k managed 714km/h even V5g will pass the 700 km/h mark, as the speedloss in topsspeed was only 10km/h compared to the smaller wing.
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From "The Warplanes of the Third Reich" by william green;
T.O. Power 1750 Hp = 237 lbs
Combat S.L. 1636 Hp = 222 lbs
Combat 6km 1440 Hp = 266 lbs
I know there is a rating at 2240 Hp with ADi but I can't seem to locate it....