Ta 152H speed discrepancy

[moot]

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 made on Jan. 12th '45 translates as:

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):

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 with just about everything but some of the symbols translated.  If anyone knows what the math symbols mean, please share.


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

[moot]

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...

[moot]

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.

[Stoney]

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.

[moot]

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.

[Stoney]

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.

[Krusty]

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?

[moot]

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.

[Stoney]

...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.

[moot]

This one's all in your hands Stoney. It's above my pay grade

The xls file.

[moot]

double post.

[Boozeman]

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?     

[Krusty]

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.

[moot]

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.

[Stoney]

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.