Ta 152H speed discrepancy

[moot]

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 (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?

[Lusche]

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 (just one peak at ~31k).

Just to make sure.. you didn't select DT in hangar and dropped it later, I suppose?

[moot]

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.

[Lusche]

cc.

Just wondered a minute  if there might be the DT "rack" contributing to this discrepancy (which hopefully will get fixed in next release)

[moot]

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.

[dtango]

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

[Lusche]

Probably data.  We don't know which H variant for th Ta-152 we have. 

Hangar & website say: Ta 152H-1

[dtango]

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

[moot]

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.

[Saurdaukar]

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.

[Krusty]

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.

[moot]

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)?

[moot]

Does anyone know of any reason for a speed curve to be so jagged over such small altitude gradients?

[uptown]

The guys in real life didn't have internet lag 

[Boozeman]

Does anyone know of any reason for a speed curve to be so jagged over such small altitude gradients?
(Image removed from quote.)

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.