Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: moot on July 08, 2009, 05:30:51 AM
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Problem:
The most commonly reported max speed in the Ta 152H literature is ~470 TAS @ ~41kft.
Harmann's book quotes 454 TAS @ 31.1 kft (max MW50 altitude), and 469 TAS @ 41 kft.
The AH 152 does 459 TAS @ 41 kft, and 462 @ 31 kft. That's 10 mph short of its reported speed at 41k, and doesn't fit the curve given on the AH performance comparison page (http://bbs.hitechcreations.com/newscores/planeperf.php?gtype=0&pw=2&p1=40&p2=83&submitButtonName=Generate+Chart) (just one peak at ~31k).
Hypothesies:
There is a chart dated 30th May 1944 in Harmann's book with a speed curve labeled "Ta 152H mit 213E" that would match the AH top speed peak occuring at ~31 kft, but its peak speed is 429 TAS which confirms (152s only were built in late 44-early 45 six months after document's date) it's a performance prediction chart (at this altitude the AH 152 does 462mph, Harmann's H-0 is reported at 446) and rules out that evidence as a clue/explanation for the AH discrepancy.
Is the AH 152 only equipped with MW50? That doesn't add up either, because MW50 isn't supposed to be effective up at 41 kft, where the AH 152 is still only 3 mph slower than 10kft lower at its 462 TAS top speed. So if GM-1 is there, it's somehow not adding up to the 10 extra mph at 41k.
So there's two discrepancies: The historical 41kft top speed is 10mph too low in AH, and the web page performance chart is inconsistent with the game performance: it shows one peak when there's two (or a shallow slope from 462@31k to 459@41k) in the game. Is that chart for a MW50-only Ta152?
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Problem:
The most commonly reported max speed in the Ta 152H literature is ~470 TAS @ ~41kft.
Harmann's book quotes 454 TAS @ 31.1 kft (max MW50 altitude), and 469 TAS @ 41 kft.
The AH 152 does 459 TAS @ 41 kft, and 462 @ 31 kft. That's 10 mph short of its reported speed at 41k, and doesn't fit the curve given on the AH performance comparison page (http://bbs.hitechcreations.com/newscores/planeperf.php?gtype=0&pw=2&p1=40&p2=83&submitButtonName=Generate+Chart) (just one peak at ~31k).
Just to make sure.. you didn't select DT in hangar and dropped it later, I suppose?
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Nope. 25% fuel and 0 fuel burn. Set wind to fly me to altitudes, left it on 127 tail wind + 127 upstream till I passed expected top speed + a dozen mph, then cut all wind and left it auto-leveled for 9min WEP'd at a time till speed settled. When it wasn't settled after 9min, I noted speed and let engine cool off, then accelerated past that noted speed with wind and again resumed normal flight with wep for 9 more minutes of WEP, etc.
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cc.
Just wondered a minute if there might be the DT "rack" contributing to this discrepancy (which hopefully will get fixed in next release)
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Nope and that doesn't shed any light on why there's more speed at 31 than 41 thousand feet.... I really don't get it. I'm hoping it's a simple bug to fix.
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Probably data. We don't know which H variant for th Ta-152 we have. Pyro I'm sure is aware of the quoted figures but my guess is he has more complete flight test data for a different H variant than the one for the oft quoted figures.
Tango
412th FS Braunco Mustangs
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Probably data. We don't know which H variant for th Ta-152 we have.
Hangar & website say: Ta 152H-1
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Hmmm well then assuming it's an H-1 then we could still speculate the difference to be anything. History does show that AH designations could mean anything ergo the Bf-109G-10. My bet is that at the root it's a difference in data issue not an FM "bug".
Tango
412th FS Braunco Mustangs
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Hmmm well then assuming it's an H-1 then we could still speculate the difference to be anything. History does show that AH designations could mean anything ergo the Bf-109G-10. My bet is that at the root it's a difference in data issue not an FM "bug".
Tango
412th FS Braunco Mustangs
Yes but I'm a sucker for investigation :) And it's not clear yet that we can't at least make a bit of head way by eliminating some of the possible explanations.
There was the H-0 and H-1, everything else was prototypes. In those two types the possible combinations were with MW-50 and GM-1. Neither, one, or both (edit - and wing tanks too). Which configs were used is a bit sketchy, but a speed chart ought to make it obvious whether they were used.. Top speed at 32k is consistent with only MW50 being used. Unless the trial was run with less than maximum boost charges - GM1 could be run at three different rates (60, 100, 150 g/sec). Add to that that IIRC the post war tests made in England were without either or both of the boost systems functional (no liquid avail.)... and a report from 9./301's Lt. Hagedorn saying that they broke 510 mph at 43,300ft on Feb 2nd '45 (Monogram 24); also that the same 152 held ~4kft/min rate of climb up to ~10kft.
An official FW document in that same book also lists top speed as 467 @ 40,682 ft, and 457 @ 45,276 ft. So there's a spread of top speed figures, but they're mostly ahead of the AH 152's, and most of them have top speed at ~41k, not ~31k.
One exact match is the take off weight (incl. GM1 fuel) of 11,501 lbs which matches exactly the AH 100% fuel weight. So it's unlikely that the AH 152 isn't with MW50 and GM1. This is from the same Focke-wulf docs dated Jan 12th '45. (BTW same docs say that the H-1's MK108 load was "85-100" rounds - no reference to exact FW doc #, though).
There's enough info in the books I have to make a tentative summary of which boost systems were equipped in production series (e.g. high/low pressure MW50) to try and see if there's a specific variant that could fit with the AH speed curve, but I'll only have time to do that later today/tomorrow.
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I smell an update.
Update Notes:
-Fixed Focke Wulf Ta-152H-1 performance.
-Fixed Focke Wulf Fw-190A-5 performance.
-Added Messerschmitt Bf-109G-10.
-Added Messerschmitt Bf-109G-6 A/S.
-Added Heinkel He-111.
-Removed Supermarine Spitfire Mk16.
-Added Community Vote: Kick Player option.
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It's been that way since it was first introduced. I recall years back 1 or 2 people bringing this up, listing problems with the 152's speed charts. It looks like GM-1 isn't modeled, one person said (this was long ago, don't recall whom).
Overall it could use a once-over by Pyro.
P.S. I thought the H-0 didn't have the GM-1, and had 120 gallons less fuel onboard than the H-1 did. Maybe the power chart is for an H-0 without GM-1? Either way the 152 in-game is rather piggish at those alts. I know. I've taken it up there quite a few times.
EDIT: Going off of Moot's post, I do recall also the allied testing. They got about the climb rates we have now (WEP in-game) but all reports say they didn't have the boost juices while getting those numbers. I've always felt the 152 in AH is severely under-climbing it's real potential.
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Still looking and sorting thru what I find, but apparently this is all very old news.
Letwolf, it's not only that it's too slow at 35k+, it's that AH's max speed IS at 35k while the real one had it's max speed at about 41k.
35k was it's maximum boost altitude for the engine, only GM1 brought it up in speeds of 472 mph above 35k, GM1 definatly seems to be either badly modelled, or not modelled at all.
The H-0 and H-1 both went thru a lot of mods. Add the fact that it's a small population size, and you get no real trends to go by as "standard".
I'm still compiling everything in all the sources I have.
.. What I don't get is how the 152 in the service exceeded 500mph (as high as 515), and yet the AH performance not only falls short but doesn't seem to match any historical speed curve that I've seen (yet!), nor the even official AH charts (chart says clearly less than 457 at ~41, game gives ~459 at ~41) - which hints at it being calculated (not doubting that Pyro doesn't know how to do quality extrapolation from few data points). Could it be that GM1's modeled at its lowest rate (60g/sec)?
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Does anyone know of any reason for a speed curve to be so jagged over such small altitude gradients?
(http://farm3.static.flickr.com/2511/3703893489_a11d7295a2_o.jpg)
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The guys in real life didn't have internet lag :rolleyes:
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Does anyone know of any reason for a speed curve to be so jagged over such small altitude gradients?
(http://farm3.static.flickr.com/2511/3703893489_a11d7295a2_o.jpg)
Honestly, I dont think that part is actually a part of the speed curve...if it was it would mean that there would be multiple top speeds at a given altitude with the same conditions. Could be wrong though.
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Honestly, I dont think that part is actually a part of the speed curve...if it was it would mean that there would be multiple top speeds at a given altitude with the same conditions. Could be wrong though.
Yep, but what does it mean? That they skipped straight to that altitude during the trial? That's my guess but I'm asking in case anyone can think of a better explanation. The AH 152 has a similar cleft in its speed curve.
The jagged curves look as if they'd run at two different GM1 settings, but why would they do that when max speed is the goal? It would make the top GM1 curve peak at 472 TAS, if it was extended to 11.5 km. That does match another quoted top speed ("472 MPH"), but I haven't seen that one in an actual book. And it would equate to a little over 500 TAS at that altitude (11.5 km) if you go by the relative sea level speeds at MIL and 1.92+MW50.
The above Focke-Wulf speed trial (http://farm3.static.flickr.com/2511/3703893489_a11d7295a2_o.jpg) made on Jan. 12th '45 translates as:
(http://farm3.static.flickr.com/2550/3713204119_430d41fb92_o.png)
So this shows a speed trial using a Ta 152H-1 with the same engine as ours, same RPM settings, with MW-50 and GM-1 used, but with the airplane carefully prepared for high speed, and with the engine running at 1.92 ata; except for the GM1 section above 11.5kft where it's at regular MIL power (which'd be consistent with the operational report of 500+ mph top speed by Hagedorn of 9./JG301 in early '45).
This differs from the AH 152: Ours isn't prepped for high speed trial and runs at only 1.8 ata.
Widewing ran the AH 152 (at 25% fuel) and got the below points in blue from the E6B (at 5kft intervals). Getting rid of that fuel difference (50% internal as in the 1945 trial) gives three extra speed points at three altitudes that stand out on the historical chart (9.5, 11.2, 12.5km = 31, 36.7, 41 kft):
(http://farm4.static.flickr.com/3473/3713992376_ac33c9d823.jpg) (http://farm4.static.flickr.com/3473/3713992376_9a4df8c51a_o.png)
There's a dent at 11.2 km. At 9.5 and 12.5 km there's no difference (+-1mph, within error margin) with WW's test. But the dent at 11.2 km does show that it's not just a simple recession after FTH, which kills any hypothesis based on GM1 not being modeled.
So what, then?
1) The official speed chart doesn't match what actually happens in the game. No biggie, but worth pointing out.
2) 32,000 ft is the engine's FTH, but why is that the AH 152's best speed when GM1 is modeled? GM1 could be used at three levels: 60, 100, and 150 grams/second. Is the AH 152 running at less than full GM1? Would that be because it wasn't cleared for 150g/sec (kind of like the K4 running at only 1.8 ata despite documents showing it was later cleared for 1.98)?
3) How is the AH 152, with more drag and less power, out-running the 1.92 ata speed-prep'd 1945 Ta152 at sea level and 32,000 ft? GM1 only comes on above ~37,000 ft.
3b) Was the Ta152H1's WEP ("Sonder Notleistung") 1.8 or 1.92 ata?
4) There's no top speed data (that I know of) for 1.92 ata + GM1, except for the nearest anecdotical data point: Hagedorn's report that a Focke-Wulf engineer confirmed he'd broken 500 TAS (">810kph") at 43,000 ft. It's just an anecdote, but it does get along with all the other historical practical and anecdotical data that doesn't exactly match AH. We can take this lead further but I'm out of time right now.
This is that german drag chart (http://farm4.static.flickr.com/3465/3703845931_f0556c4ac6_o.jpg) with just about everything but some of the symbols translated. If anyone knows what the math symbols mean, please share.
(http://farm3.static.flickr.com/2646/3712672442_11977f41d2_o.png)
Does anyone know good sources for WWII german aircraft engine data?
Oh yeah, and if this gets the 152 FM revised to a lower speed (as if the 152 needed even more handicap), you know who to blame :D
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New idea. The Jumo213E WEP is supposed to be 1.92 ata, not 1.8. Somehow this got by during modeling, maybe because the Jumo 213-A uses 1.8 for WEP.
The speed trial's purpose was max speed. They wouldn't have passed up on an opportunity to run at full GM1 if that allowed for what that top curve at 12.5 would've allowed down at 9.5km (~472 TAS), unless there was a good reason.. Like damaging the engine? Gradual increases in GM1 boost with rising altitude would make sense, as well as reducing power to MIL, to isolate GM1 as the single (engine temperature/stress) variable. This would also be consistent with the 500mph+ report, if Hagedorn had gone ahead and used max MAP and/or full GM1 boost. edit Actually, you couldn't get to such a speed without using both full manifold pressure and full GM1 on the 12/1/'45 trial, much less a non-prepared Ta 152 like the one Hagedorn was flying.
It'd be interesting to see if a sim using the right numbers (prop eff, engine power, exhaust thrust, drag coeff at a couple of different alts, etc) would corelate the focke-wulf and/or AH curve well enough.
And the engine power figures you can find on the internet are all over the place. Seems like finding reliable books is the minimum for credible figures. If only I had time to build a proper engine sim...
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What a mess. Contradictions everywhere.. Even Harmann's book has inaccuracies that Harmann openly pointed out after the book was out. Maybe the AH 152H is as it is to kind of hybridize the whole spectrum of performance of the couple dozen 152H-0s and H-1s that saw action. It'd be better if we had an H-0 and H-1, though. The H-0 would have no boost systems or wing tanks and top out at the engine's natural FTH, and the H-1 would be configured like the last 152H-1s for 470 TAS at 40k+. There has to be a way to prove beyond doubt that a normal 152H-1 with a 213E-1 and GM-1 could easily do at least 470 @ 41k.
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If anyone knows what the math symbols mean, please share.
I'll get my books out and start going through this. I recognize some stuff already.
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Thanks Stoney. I'll post the rest of the figures needed for a bootstrap speed sim when I find em.
... 2.03 ata and ~370+ mph at sea level in this trial.
http://aycu27.webshots.com/image/12946/2005488039815659769_rs.jpg
I guess there's no way to argue for anything to change on the AH 152's MAP without some documentation of operational use, or some concrete mention that these trials were using MAPs allowed operationally.. If nothing else it's useful as a rough cross check on Cd value and power/MAP relationship.
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One thing that jumped out at me was the airfoil profile, which if I'm reading the chart correctly, shows a 20.6% thickness root chord. That is certainly unique among WWII fighters, and a departure from the 15 and 16% thickness profiles used on all of the other designs. I guess they needed that extra thickness to keep the structural strength in the higher aspect ratio wing.
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That shouldn't be accurate, unless the 190A/D models also had the same thickness. If the 152 wing were thicker at the root than the previous versions, you wouldn't see wing root gun hatch bulges, but you do see these (same as the previous models).
Moot may be right about the hybridization of the 152 FM. Maybe that is why they were reluctant to update the 152 along with the 190s, because they wanted to revisit the FM, but decided not to?
I personally think there's not enough difference between the H-0 and H-1 to warrant both their inclusion, especially since the H-0 is a pre-production variant, and there were only 12 or so H-1s that saw service.
The numbers you're providing, contradictory or not, are quite interesting. If it's too fast we should either fix it or change the cockpit dial to read 1.92 ata (if that is the power curve we have modeled in-game)
I'm wondering if your resources provide more than just speed curves. That allied test keeps picking at me, where they achieved climb rate numbers similar to in-game WEP but without any additives to provide the actual WEP. Any better milpow climb charts, test reports, what-have-you?
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I know next to nothing about airfoil trends, but one bit I do remember is that the 152 is supposed to be a NACA 23015.3 at the root and 23009 at the root. I could be wrong, though.
I don't have that allied test documentation. I'd be glad to have a copy if you or anyone else finds one.
I do think it'd be worth having separate H-0 and H-1 because they're different enough. Having a 152 that neither does its top speed (the purpose of the Ta 152H to begin with) as the H-1 did, nor has the light weight to furball at low altitude as the H-0 did.. that's doesn't make as much sense as having two separate historical H models. Not that I'm complaining that the 152 we have isn't fun. I'm just pointing out what the best arrangement would be.
Numbers - don't really matter. At least a few H-0s were brought to H-1 spec. There's no real trends or standard other than factory specifications and most commonly used configurations in the field, because the war's end made things such a mess and because the population size is so tiny in the 152's case.
As far as the numbers I'm reporting go, I think it's worth waiting till I/anyone else stop finding more of them and make any conclusions only once all of them are compiled and made sense of. The 152 isn't really a priority model in the AH planeset. And that Eagle/Monogram book is coming out later this year. And if it's that long before it's a good time to work on the 152, there's that book by "Erich" due sometime in the next 5/10 years. Time's on our side. Better to make a complete and air-tight presentation to HTC than jump the gun.
I think this is actually a great position to do this from. No deadline to figure it out, and it saves Pyro a lot of wading thru paperwork. With some luck we find enough data to back up historical documents and anecdotes with solid calculations setting upper and lower bounds at the very least.
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...supposed to be a NACA 23015.3 at the root and 23009 at the root...
Perhaps I'm wrong. Certainly Dave Lednicer's website says 15/9. Its just that in the first line under Flugel, it appears to have airfoil data and the first column appeared to correspond to the 190 thickness ratios. So, I assumed.
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This one's all in your hands Stoney. It's above my pay grade :D
The xls file. (http://dasmuppets.com/public/moot/0d/FwDragTable_en.xls)
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double post.
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Ok, since we are somehow on the Jumo 213, I have a question you can maybe answer:
Is there actually any power difference between the 190D's 213 and the 152's 213? For instance, are the the power outputs at a given rpm/boost setting similar? I know that the 152's engine has a higher FTH, so it can make more power up high, but does ist also make more power at all?
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It's a different model of 213, like the DB 601, 601A, etc, had different capabilities, I think the same is true of the 190D/152H1 engines.
I haven't actually checked, but as far as I remember, they're different animals.
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The D9's 213A is optimized for lower altitude performance and the 152's 213E seems to have been designed to accomodate MW50 and GM1 boost. The A's a single (or two, can't remember) stage, two speed, while the E's a two stage three speed.
Now that I think about it, I can't recall the exact power outputs for each either. I'm pretty sure the AH 213A is at 2200 and the 213E at 2050, both with wep at 1.8 ata. I think the 213E puts out 1750 PS without wep at 1.6 ata, and the 213A 1900. IIRC the 213A had the same sea level 1.6 ata output, but that engine got some stopgap solution while the expected MW50 systems weren't available yet, giving that extra 150 horsepower... and that's the 213A we have in AH. I could be wrong.
Found these. They're garbled and I'm not sure if they're accurate, but it should be a rought ballpark of what their power/altitude curves look like.
(http://farm3.static.flickr.com/2491/3721804730_001e4959d8.jpg) (http://farm3.static.flickr.com/2491/3721804730_49ea99794f_o.jpg)
(http://farm3.static.flickr.com/2640/3721804812_90887ca640.jpg) (http://farm3.static.flickr.com/2640/3721804812_093b47f52e_o.png)
(http://farm4.static.flickr.com/3098/3720991955_e59925d680.jpg) (http://farm4.static.flickr.com/3098/3720991955_8ec96daf38_o.png)
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That shouldn't be accurate, unless the 190A/D models also had the same thickness. If the 152 wing were thicker at the root than the previous versions, you wouldn't see wing root gun hatch bulges, but you do see these (same as the previous models).
Its certainly not anything I'd use to hamstring the Ta-152 performance. It just appears from Moots document that the airfoil profile was not a 23000 series, as the block shows Fw290, which I would assume is some sort of proprietary design. I could be making stuff up due to the translation, but you could imagine that a longer, shorter-chord wing would need a thicker airfoil simply to maintain, for example, the same spar dimension, if they needed that to maintain the +6 G design load. In designing my own aircraft, I can tell you that high aspect, tapered wings like this create some problems structurally. Ultimately, it doesn't really bear on the topic--just something I thought was interesting, if indeed true.
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SD67 has all the foil data you should need.. He just needs to find the root and tip chord data. Says he can work out as many drag polars as you might want.
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We don't need the drag polars for the airfoil--I can do that myself. Where did he get his information on the Ta-152H airfoil? Originally we were looking for the zero-lift drag coefficient for the Ta-152H when we started looking at this. I was merely making an observation--it won't really bear on anything going forward other than simple trivia...
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The Ta152H airfoil if you need to do in-depth analysis.
152 airfoil (http://www.mediafire.com/?wimzrzywztz)
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Not to be obtuse, but you're sure this is for the H and not a C?
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I don't have complete blueprints yet, so I can't tell myself.
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I suppose ultimately, we'd need a dimensioned drawing of the Ta-152H wing root. The one in the .tif file Vortex sent is a NACA 23000 profile--I can tell without a translation--its a very distinctive shape.
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I'm pretty sure, though not 100%, that it is a H airfoil but can verify with Hermann if you want to be absolutely sure.
Here is some more data. Ta152 airfoil (http://www.mediafire.com/?y3xymny5y5j)
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Is this the wingroot info you are looking for?
I'll remove these links so... wingroot (http://www.mediafire.com/?xuzydjt3onl)
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The FW drag data gives the polar as function of the flat plate area and Cl. As example in the case of the Ta 152H at high speed, the flat plate area is given as 0,502m2 and value of the K as 0,95. These can be converted to dimensionless form by dividing with wing area 14,44m2, thus Cd0=0,021545 and K=0,040773 (=> e=0,87).