Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: gatt on November 16, 2001, 03:15:00 AM
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Take a look at climb times and max speed at altitude (from "Close-Up" series by Thomas H. Hitchcock):
(http://www.cpacetti.supereva.it/109Gtable.jpg)
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Hi Gatt,
thanks for the post!
There seems to be a typo in the "maximum emergency speed at maximum altitude" column for the Bf 109G-6/R2, it probably should read 666 km/h instead of 566 km/h.
Too bad there's no climb chart provided for WEP! From a quick calculation, I'd estimate the Me 109G-6/R2 climb rate with MW50 injection at about 28 m/s at sea level.
Regards,
Henning (HoHun)
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Hi again,
>From a quick calculation, I'd estimate the Me 109G-6/R2 climb rate with MW50 injection at about 28 m/s at sea level.
Talk about typos! My estimate is 25 m/s.
Regards,
Henning (HoHun)
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Well, Hitchcock's data is quite questionable. Just look those speed and climb curves, the DB605 had variable speed supercharger so why there are those steps in the curve? ;)
gripen
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I noticed that too gripen, looks more like Spitfire curves.
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Hitchcock's data comes from official Luftwaffe charts, as mentioned on the top of the image.
Other german charts (captured documents now stored at IWM) show similar "steps" in speed.
[ 11-16-2001: Message edited by: phantasma ]
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Originally posted by gatt:
Take a look at climb times and max speed at altitude
I just did some rough climb tests:
Climb time to 20k 25% fuel
109F-4: 5'53 / WEP: 5'05 (average ft/min: 3399/3934)
109G-2: 5'41 / WEP: 5'01 (average ft/min: 3519/3987)
109G-6: 5'53 / WEP: 5'11 (avegare ft/min: 3399/3859)
109G-10: 5'36 / WEP: 4'27 (average ft/min: 3571/4494)
seems to be similar to that data, with more fuel, it'd be over 6 mins.
Note: considering my ablility to do math, above numbers are prolly BS :)
vector
[ 11-16-2001: Message edited by: vector ]
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phantasma,
well, It does not matter where from that data is. There is no such steps if the supercharger is variable speed system. That data is clearly wrong.
gripen
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Yep those are curves for an engine with a 2-speed supercharger --> Not a DB 605.
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NM
[ 11-16-2001: Message edited by: funkedup ]
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Looks like that climb/speed chart is from a FW190A.
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The gear ratio for the supercharger in the DB605 was 10.07:1. How is that variable speed?
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Wells, they used a clutch to control blower speed. Clutch slip was controlled barometrically. Below rated altitude the clutch slipped, reducing the blower speed. At rated altitude and above the clutch was fully engaged and there was no slip.
If they quote a gear ratio for this mechanism then it is based on tooth counts and would only apply at or above rated altitude.
[ 11-16-2001: Message edited by: funkedup ]
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This data is definitely wrong, it fits better a 190 or a Spit than a 109. The data i have on various 109 versions is definitely diferent from this one.
here is one for the K4, notice the difference, other 109 speed graphs are similar in shape.
(http://www.allaboutwarfare.com/files/pictures/aviation/ww2/russia/data/Aircraft-evaluation-6.jpg)
and one for the G.
(http://allaboutwarfare.com/files/pictures/aviation/ww2/russia/data/Aircraft-evaluation-15.jpg)
(http://allaboutwarfare.com/files/pictures/aviation/ww2/russia/data/Aircraft-evaluation-19.jpg)
[ 11-16-2001: Message edited by: butch2k ]
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Boy those Rooskies sure captured a crappy Fw 190A-5! ;)
Hey Waffles you guys want HTC to use this "authoritative" Rooskie data instead of the "biased" USAAF data they have now? :D
[ 11-16-2001: Message edited by: funkedup ]
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russkies say 190 a5 is slower than a yak-t? i wish i had some of the hashish they have been smoking
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Zig how many times do I have to tell you that wartime test data was HIGHLY VARIABLE. :)
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*wonders what happend to those soviet research personel who rated german fighter better than soviet fighter*
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LOL Fishu :D
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But their 109 rolled better then a 190...
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Hi everyone,
the suggestion that the data presented in Hitchcock's book is not realistic (or even from a Focke-Wulf) is not that far off, since the data presented isn't entirely conclusive.
However, the key data points of the graph match the key points given in the textual description, which is specific enough to be credible.
The low-altitude corner that looks exactly like a pressure drop of the first speed of a 2 speed blower is unrealistic, but it re-appears in the Russian graph for the Me 109G-4 where it's smoothly rounded out however.
(If you look closely, the Russian Me 109K-4 graph actually has a slight corner, too.)
Another thing that isn't quite conclusive is that the speed difference between climb and combat power and special war emergency power is more or less independend of altitude. In reality, MW50 injection would improve performance dramatically up to some way below full pressure altitude, and only slightly above that.
(Low, it would primarily act as anti-detonant, while high, only the secondary charge-cooling aspect would help performance. The Russian graph for the Me 109K-4 shows the former, but not the latter - in other words, it's simplified, too.)
Comparing Hitchcock's version of the Me 109F-2 graph (that hasn't been posted here) with a copy of the original Luftzeugmeister's one, I'd come to the conclusion that it was slightly inaccurately redrawn for Hitchcock's book, and includes some errors in labeling, too.
Though the above Me 109G graphs have a slightly different outlook, I'm confident that they are based on the originals as well, and I'd speculate that the German originals might have been simplified, too, indicating the unrealistic corner in the graphs.
However, it certainly would be better to have a look at the original document, especially since if the translation went wrong, we might be looking at graphs for different power settings than Hitchcock states.
(I actually like Hitchcock book on the Me 109F very well, and would love to own his work on the Gustav, too. Still, I admit graphs are not one of his strengths :-)
Regards,
Henning (HoHun)
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wish I had a scanner. I have some F-2 climb speed and climb rate curves... none witch show steps like the first G-6 curves. There are steps but nothing like above.
// fats
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Here we go:
(http://www.cpacetti.supereva.it/109Ftable.jpg)
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Some curves for the E3 and F1
(http://allaboutwarfare.com/files/pictures/aviation/ww2/russia/data/Aircraft-evaluation-16.jpg)
(http://allaboutwarfare.com/files/pictures/aviation/ww2/russia/data/Aircraft-evaluation-17.jpg)
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Hi everyone,
Great charts! :-)
But don't get me wrong, what I'm saying is not that the Me 109G top speed curve should look like the Me 109F top speed curve. What I'm saying is that there are inaccuracies in Hitchcock's reproduction of the original graphs.
Here's the original Me 109F graph for comparison (wish we'd have the Me 109G graph, too):
http://members.aol.com/wbhohun/109f1_kennblatt_7.gif (http://members.aol.com/wbhohun/109f1_kennblatt_7.gif)
Hitchcock screwed up the true/indicated air speed labeling and failed to explain that the dotted line is emergency power. We're going to have to expect similar problems with the Me 109G graph.
Don't get me wrong about the "corners" in the Me 109G curves either: I'm not saying there should be corners. What I'm saying is they the curve did not run straight from sea level speed to best altitude speed.
The Russian curve for the Me 109G-4 posted above shows a forward "bulge" in the top speed graph that's attributable to the variable speed supercharger.
Here are 2 more graphs displaying such a bulge:
http://members.aol.com/wbhohun/109ts.jpg (http://members.aol.com/wbhohun/109ts.jpg)
(The Finnish Messerschmitts had the emergency power setting disabled to increase engine life. The graph is for climb and combat power.)
http://members.aol.com/wbhohun/109speed.jpg (http://members.aol.com/wbhohun/109speed.jpg)
(Unknown Russian source :-) I suspect the Me 109F-4 curve is bogus.)
It's my impression that the subject is more complicated by the nature of emergency power: With MW50 injection, the DB605 provides higher power, and the "bulge" in the speed graph moves to an altitude just above sea level so it's no longer recognizable. The Russian Me 109K-4 graph above shows that.
In short, I believe that Hitchnoodles curves are for a Me 109G with DB605 engine, but they are a simplified depiction, and that they are not "climb and combat power" and special emergency power with MW50, as stated in the caption.
Regards,
Henning (HoHun)
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Hmm Hitchnoodles data is really strange BUT they show also some nice details. I assume that he was very glad to get some data together for his book, but didnīt look carefully enough to the data to interpret them correctly.
Good information is f.e that he gives 1475hp for takeoff power (first row), and later for max. emergency speed at ground level 1440hp (530-1440-0) - here you can see the RAM effect which reduces the power below critical altitude a bit. The same can be observed for the BMW 801, 1800hp takeoff power, and 1730 for high speed low level flight.
Iīm only wondering myself why the G6-R2 is listed as a reconaissance fighter. Afaik the R2 is equipped with a bombrack to carry 4*50kg bombs. Reconaissance aircraft usually were equipped with GM-1 and not with MW-50.
The given chart has also similarities with the chart of a 190, but it isnīt from the 190. But if you look at the F1/F2 table and compare it to the chart of the F-Model, you can easily see that his charts not always have to represent exactly the table. Just compare the climbrate (20.5 <> 18. ) or the power (1175 <> 1250 (dotted line in the original))
Or why does the climbrate of the F4 does drop down to 17.0 compared to 20.5 of the F1 and F2 according to the table?? It had 150hp more power, and was only slightly heavier.
In the G6-R2-table he mentions 6.6km as critical altitude for combat speed, but in the Graph the critical altitude is 6.0km
I have the impression he didnīt even know about the supercharger system of the DB605 and tried to bring the collected data into a form he was used to from allied engines.
In my eyes he is the typcial historian: Very good in collecting data, in digging in achives, but whenever they have to interpret technical data correctly they fail quite often. Nowarra is such an example on german side.
Anyway, itīs the first time iīve seen a speed number for a G6 with MW-50. If it was really a R2 with a bombrack, then 560km/h seems to be realistic. When it it official geramn data, then at least noone can claim that german exagerrated their aircraft performace claims ;). Iīve also read statements that pilots reached 590km/h near ground with ASM engines (factory fresh aircraft)
Remarkable is imo the different trend of the G4 curves (climb and speed). Wheras in the speed chart the bulge is near ground, and the straight increase near critical altitude, the style of the climb rate curve is inversed. Straight increase near ground, above the (inverted) bulge. The finnsih top speed charts corresponds much nicer with the G4-climb rate chart. But this maybe depends only on the artist who draws a continious line through few test data points.
A certain bias is definitly existent in the russian charts. Itīs interesting to see that the combat power curves of the russian aircraft most often hit EXACTLY the emergency power curves above critical altitude, or after switching into the 2nd. gear (La-series). This is for flight test data very unlikly and imo a good indication that the data is based on theoretical calculations with ideal engine power charts.
And of course most pictures have a russian fighter as fastest fighter near ground included. Most pictures publish only combat power for the german planes. Most pictures neglect MW-50 (190D, too!). And when a P-51 and K-4 would be as fast as the La-7 from other charts (where it does 615km/h), they throw in a La-7 what does suddenly 630km/h near ground... (The 206 prototype ehh?)
Iīm also wondering myself why they publish the 109E-3 speed data though the climbdata makes it evident that it suffered from engine troubles near ground (climb and combat power, supercharger not working correctly?).
With MW50 injection, the DB605 provides higher power, and the "bulge" in the speed graph moves to an altitude just above sea level so it's no longer recognizable. The Russian Me 109K-4 graph above shows that.
Exactly Hohun. With 1800hp, the clutch slip disappeared already in 0,9km, with 2000hp in 0,4km. And this is the proof that the G-10 reached the often claimed 685km/h WITHOUT Mw-50, only with 1550hp. butch2k, maybe you can post the picture with the speed of the G-10 too? (btw butch2k, i havenīt seen pic 1-2, 9-15 and over 17 so far, but iīm very interested to see them - can you scan them and publish them too somewhere? thx).
About the A-5, here is an official source (The A-5 was actually faster than a A-8)
(http://people.freenet.de/nik_mc/fw190_A5_s.gif)
If you compare it to the russian test data, you can come to the conclusion that they used only continuous power. The poor climbrate is also indicating this.
niklas
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Hi Niklas,
thanks for the Fw 190A-5 chart!
I can't quite read the caption - is it correct that of each pair of curves, the left one indicates true airspeed?
If so, I'd say the charts match the RAE tests of the Fw 190A-4 and the USN tests of the Fw 190G-3 (re-configured to A-5 status) quite well. The Focke-Wulf chart indicates a somewhat more speed down low and a bit less up high, but both western allies seem to have tested fairly accurately.
From what I've read about the Russian charts, they were prepared by a group of Russian aviation experts in the 1970s and based on all information that was available then. I don't think they were interested in making German aircraft look bad, I think it's rather an artifact of different engine rating conventions.
I'd speculate Russian aircraft had continuous power and emergency power, and nothing in between. It would seem fair from a Russian point of view to use the corresponding ratings of German aircraft, but yield a misleading picture if the German continuous ratings were optimized for engine longevity and not for power output.
>here you can see the RAM effect which reduces the power below critical altitude a bit.
From what I've read, ram effect should always be beneficial, but I've seen power curves with a drop, too. Do you have any explanation? After all, ram could have been avoided by drawing in air with static pressure.
>Iīm only wondering myself why the G6-R2 is listed as a reconaissance fighter.
According to Griehl, the R2 designation was used twice (which happened more than once ;-). One R2 indicated a GM-1 equipped reconnaissance plane, but Hitchcock actually lists the R2 fighter bomber.
>I have the impression he didnīt even know about the supercharger system of the DB605 and tried to bring the collected data into a form he was used to from allied engines.
I'd say he attempted to copy the Luftzeugmeister's charts - look at the graph paper, it has divisions based on 5 as typical for German graphs, not on powers of 2 as typical for US curves. And he'd sure have used imperial measurements if he hadn't tried to recreate a German original :-)
>Nowarra is such an example on german side.
I'm going to have to defend Hitchcock against that comparison! He's much more thorough than Nowarra, whose book on the Me 109 indicates really poor research.
>If it was really a R2 with a bombrack, then 560km/h seems to be realistic.
If you're referring to optimum altitude, the 566 km/h must be a typo - I can't imagine that MW50 slowed the aircraft down from the 590 km/h it did at cruise power ;-)
>Remarkable is imo the different trend of the G4 curves (climb and speed).
The trend indicates that full speed flight benefits from air pressure (and accordingly drag) decreasing with altitude quicker than engine power. In a climb, most of the power is spent lifting the aircraft, so that you directly see the engine power decrease in the climb chart.
>Exactly Hohun. With 1800hp, the clutch slip disappeared already in 0,9km, with 2000hp in 0,4km. And this is the proof that the G-10 reached the often claimed 685km/h WITHOUT Mw-50, only with 1550hp.
Hey, that was a bit quick! :-) We didn't have a G-10 curve in this thread yet, did we?
Regards,
Henning (HoHun)
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Niklas...
first of all.190A5, 565km/h at SL?. In AH we have 335mph at SL! that is almost 15mph slower than what it should be!
I'd say that those charts are the most reliable information on factory-produced planes. So then, why is 190A5 15mph slower than what it should be?
BTW I'd LOVE to have those Focke-wulf charts!, if you can share them, that is. Could you email the ones you have to me? :)
In fact, I'd be thankful to receive ANYTHING :D you have :).
Thanks in advance :)
[ 11-17-2001: Message edited by: R4M ]
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Hi Hohun
the left one is corrected for the error of the speed indicator due to the macheffect, the right one is not. So the left one is indeed TAS, the right one is the value a pilot gets when he uses standard conversion factors from IAS to TAS without mach-correction.
This means, if a pilot reads IAS and uses the standard conversion factor for TAS, the error due to mach effect is ~15MPH in 600m@650km/h.
If this effect is neglected... well, maybe one of many a reason for several high speed claims from pilots, especially when they flew in high altitudes at high mach numbers (or the mach0,93 speed claim for a spit reached in a dive) ;)
The only explanation for the power decrease due to RAM effect i have is that the additional compression below critical altitude heats the air a little bit up. So maybe you get a slighlty worse cylinder filling.
With 560km/h i refer to ground speed.
Now the G-10 enters the stage ;)
Those are the charts from buch2kīs webpage which shows a G-10 (Note also the critical altitude. With over 7000m it would be pretty high for a 1,8x or 1,9x boost)
(http://allaboutwarfare.com/files/pictures/aviation/ww2/russia/data/max-speed.jpg)
This chart from butch2k page shows the climb performance of a A-8. Well, when the A-8 climbs better than a A-5 then itīs again a good hint that the published performance of the A-5 is for continuous power.
(http://allaboutwarfare.com/files/pictures/aviation/ww2/russia/data/climb-rate.jpg)
niklas
[ 11-17-2001: Message edited by: niklas ]
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Niklas the famous Spitfire Mach .9+ figure came from timing a dive. They took (start_altitude - final_altitude ) / dive_time and made a speed estimate.
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Hi Niklas,
>Those are the charts from buch2kīs webpage which shows a G-10 (Note also the critical altitude. With over 7000m it would be pretty high for a 1,8x or 1,9x boost)
You're right. The shape of the curve isn't idicating MW50 use, either.
What's more, I'd say that the Me 109K-4 in the above graph with its critical altitude of close to 9 km must be equipped with a DB605AS engine, while the Me 109G-10 probably has a regular DB605D engine. Griehl metions that the Me 109G-10/AS was produced before the DB605D became available, while the Me 109G-10 with the DB605D was fitted with MW50 injection as standard.
The late Messerschmitts were so much faster than the early ones that it was considered to redesign the plane for a lower angle of incidence. This was never carried out though.
By the way, do you happen to know the angle of incidence (Einstellwinkel) for the Focke-Wulf fighters? I've been looking for that one with no success so far.
Regards,
Henning (HoHun)
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Here ya go HoHun: http://www.raf303.org/funked/cfd/page239.htm (http://www.raf303.org/funked/cfd/page239.htm)
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Hi Funked,
Thanks a lot! :-)
Just to make sure I understand it correctly: The angle of incidence at the wing root is 2 degrees, right?
Regards,
Henning (HoHun)
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Sure looks like 2 degrees to me! ;)