Spit/109 sea level speed comparisons in 1.08 beta patch

[Holtzauge]

Originally Posted by ACE-OF-ACES

Very cool! I just joined the All About Warfare.. First thing I noticed was butch2k is there! I was wondering where he had gone! Al, did he ever finish that book he was working on? Or do I have him confused with someone else?

I don't know about any book but the site as such contains some nice info and HoHun has posted a lot of interesting speed and climb analysis for a number of aircraft so the site is well worth a visit.

To the best of my knowledge we use different ways to calculate performance but from what I have seen so far we seem to arrive at quite similar conclusions. My C++ simulation also allows incremental integration of data so I can model transient flight conditions like dive and zoom and instantaneous turn etc.

[ACE-OF-ACES]

Originally Posted by Holtzauge

I don't know about any book but the site as such contains some nice info and HoHun has posted a lot of interesting speed and climb analysis for a number of aircraft so the site is well worth a visit.

Ok, I just remembered butch2k's names from years ago.. He was a very informative and level heading logical guy from what I remember.. There was another guy with a name similar to his.. B something, maybe he was the guy writing the book?

Originally Posted by Holtzauge

To the best of my knowledge we use different ways to calculate performance but from what I have seen so far we seem to arrive at quite similar conclusions. My C++ simulation also allows incremental integration of data so I can model transient flight conditions like dive and zoom and instantaneous turn etc.

By the way your name rings a bell too.. I seem to recall seeing your C++ stuff a few years back.. Very neat stuff! I have some of Henning Rush's stuff posted at my website.. i.e. www.flightsimtesting.com and would love to post some of yours too! What format is your output files? Simple text I assume? Could I get a copy?

Originally Posted by Holtzauge

I see you added some Spitfire data now. I assume it's safe to bet that this is the absolute rock bottom worst data you were able to find on the Spit, right?

I see you have 'experience' with Kurfurst too!

[Holtzauge]

Originally Posted by ACE-OF-ACES

By the way your name rings a bell too.. I seem to recall seeing your C++ stuff a few years back.. Very neat stuff! I have some of Henning Rush's stuff posted at my website.. i.e. www.flightsimtesting.com and would love to post some of yours too! What format is your output files? Simple text I assume? Could I get a copy?

Had a look at your site and it looks promising! Will be even more interesting when you add some more aircraft. I can certainly do some simulations if there are some particular scenarios you would like to see and yes, the output is in text format that I copy to Excel to produce the charts.

I did post some simultion results a few years back about Fw190 dive and compressibility effects which unfortunately came to the attention of a certain Herr Crumpp whom I believe is a mutual aquaintence?

[ACE-OF-ACES]

Originally Posted by Holtzauge

Had a look at your site and it looks promising! Will be even more interesting when you add some more aircraft.

Thanks!

The IL-2 section only shows about 10 planes now, but I have the data for the 600+ planes.. I just have not bothered to upload it for now while working on the CoD portion. The biggest difference being in the CoD portion I will have the real world data plotable right along side the in game data that will allow all to see just how well the in game data matches the real world data.

Originally Posted by Holtzauge

I can certainly do some simulations if there are some particular scenarios you would like to see and yes, the output is in text format that I copy to Excel to produce the charts.

Cool!

In that as you well know, there are a lot of real world data sheets missing for specific planes! Would be nice to have your results as another sanity check

Originally Posted by Holtzauge

I did post some simulation results a few years back about Fw190 dive and compressibility effects which unfortunately came to the attention of a certain Herr Crumpp whom I believe is a mutual aquaintence?

Acquaintance may be too strong of a word?

[camber]

After reading through this thread and the last big thread on this issue:

http://forum.1cpublishing.eu/showthread.php?t=32259

I am still in the camp of the typical 109E doing around 475kmh at SL and 560kmh TAS top speed. IMO it is too much argument work to make the available flight tests match the 500kmh deck speed for series 109Es, as opposed to allowing that the aircraft were actually around the pass/fail level at SL (but OK at alt).

One thing that was brought up in the last thread, that the aircraft would be "failed" and sent back to Messerschmitt if they did <475kmh at SL. However, the 109G acceptance plot posted in this thread shows testing at a single altitude that varies but is closer to FTH than SL. It makes sense to me that acceptance tests would not be based on a full speed vs alt test regime, and especially not an actual test of the 109 belting along at sea level (a bit difficult to arrange except in CloD). So a 109 doing 470kmh at SL could still pass.

The other thing is considering 1.3ata vs 1.35ata. If the actual limit was 5 mins 1.3ata without the takeoff boost, I don't see that the fact the CloD 109s show 1.35ata suggests they should be made faster than historical (although we are getting toward hair splitting). Instead the CloD boost indication should be fixed or ignored. In the same way if the CloD Spit boost gauge showed +14psi, I wouldn't expect it to be made faster than historical to match the gauge.

One thing I really find interesting for 109s is combat use of the 1 minute takeoff boost. Whether or not it actually works except close to SL really depends on how it is designed...similarly to difference between the actual Spit II gated takeoff boost (will decay quickly with alt) and red tab combat boost (will work at any alt the supercharger is capable of delivering it).

Right now the 1.45ata works even up to FTH (odd), which seems very unlikely. But in real life it should certainly work if you are chasing or being chased low over the channel, but I have not seen a combat report or memoir that confirms this.

With that all said, I would be happy with 500kmh SL 109s if that gave the best and most fulfilling online CloD for both red and blue (with red FM fixed too)

camber

[Holtzauge]

Originally Posted by camber

After reading through this thread and the last big thread on this issue:

http://forum.1cpublishing.eu/showthread.php?t=32259

I am still in the camp of the typical 109E doing around 475kmh at SL and 560kmh TAS top speed. IMO it is too much argument work to make the available flight tests match the 500kmh deck speed for series 109Es, as opposed to allowing that the aircraft were actually around the pass/fail level at SL (but OK at alt).

One thing that was brought up in the last thread, that the aircraft would be "failed" and sent back to Messerschmitt if they did <475kmh at SL. However, the 109G acceptance plot posted in this thread shows testing at a single altitude that varies but is closer to FTH than SL. It makes sense to me that acceptance tests would not be based on a full speed vs alt test regime, and especially not an actual test of the 109 belting along at sea level (a bit difficult to arrange except in CloD). So a 109 doing 470kmh at SL could still pass.

The other thing is considering 1.3ata vs 1.35ata. If the actual limit was 5 mins 1.3ata without the takeoff boost, I don't see that the fact the CloD 109s show 1.35ata suggests they should be made faster than historical (although we are getting toward hair splitting). Instead the CloD boost indication should be fixed or ignored. In the same way if the CloD Spit boost gauge showed +14psi, I wouldn't expect it to be made faster than historical to match the gauge.

One thing I really find interesting for 109s is combat use of the 1 minute takeoff boost. Whether or not it actually works except close to SL really depends on how it is designed...similarly to difference between the actual Spit II gated takeoff boost (will decay quickly with alt) and red tab combat boost (will work at any alt the supercharger is capable of delivering it).

Right now the 1.45ata works even up to FTH (odd), which seems very unlikely. But in real life it should certainly work if you are chasing or being chased low over the channel, but I have not seen a combat report or memoir that confirms this.

With that all said, I would be happy with 500kmh SL 109s if that gave the best and most fulfilling online CloD for both red and blue (with red FM fixed too)

camber

Did not read your excellent compilation in post#1 until now but I think it does a good job of summing up the situation so thanks for the info!

Some additional thoughts on the Me109E speed issue: First of all that 1.35 and not 1.3 ata was displayed in the CloD was news and also that take-off boost as high as 1.45 ata was usable at altitude. Wonder why they modelled it like that? Is there some data indicating that this was the case? Most data I have seen list Dauerleistung 1.15 ata, Steig und Kampffleistung 1.23 ata and then the 1.3 and 1.4 ata Startleistung boosts. Anyway, it just struck me that there is an alternative way of accessing Me109E sea level speed at 1.3 ata boost:

If one assumes that the Steig und Kampffleistung figure of 460 Km/h according to datenblatt L. Dv 556/3 at 1.23 ata boost is correct then one can use this to estimate the ballpark figure for 1.3 ata. Assuming that the prop efficiency is about the same and that the drag coefficients are fairly constant ( I think this is reasonable given that the induced drag is not a major factor at top speed and that if anything, the Cdo should go up somewhat due to compressibility effects) one could calculate this:

Assuming 910 Ps at 1.23 ata and 990 Ps at 1.3 ata (From datenblatt L.Dv 556/3)

Solving for speed at 1.3 ata:

v=460 x (990/910)^(1/3)= 473 Km/h

So if we assume that the speed figure of 460 Km/h at Steig und Kampffleistung is correct then this would lend further credence to the 475 Km/h figure at 1.3 ata.

Interestingly, using the same principle for the Spitfire Mk1 at +6.25 and +12 boost is spot on compared to the chart figure of 314 mph at +12 boost:

Assuming 885 hp and a top speed of 283 mph at +6.25 boost this then gives for +12 boost assuming 1201 hp:

v=283 x (1201/885)^(1/3)= 313 mph

[TomcatViP]

The 1/3 coeff i s good (came from dEc/dt=SUM(P)). Seems at least this went trough the mind of the bloggers.

However at high speed (and we will talk abt what is high speed), drag does nit increase linearly, but rather as a square function at the rate of the maximum local speed on the extrados of the wing (I am taking into account wing drag only) which is already significantly higher than the plane frwd speed.

To be rigorous also, at speed higher than Mach0.3, you'll need to make the conversion btw local press, ro and speed. The relation btw the Power and the speed is not true anymore if you don't add a term in ^2 to reflect the wet surface and the viscous drag effect.

So there is no linear relation btw speed and power, hence no guess work on the estimate gain in speed. A close look at a pressure plot of any airfoil will give you a hint. Usually an honest guy will use this equation in reverse, to have an idea of what is the ABSOLUTE MINIMUM of POWER you'll need for any increase of speed.

[Kurfürst]

Originally Posted by camber

I am still in the camp of the typical 109E doing around 475kmh at SL and 560kmh TAS top speed. IMO it is too much argument work to make the available flight tests match the 500kmh deck speed for series 109Es, as opposed to allowing that the aircraft were actually around the pass/fail level at SL (but OK at alt).

My view is that other POV, which simply wants to ignore the official specs and ignore test results in favour of uncorrected (engine powers not corrected) tests with very little detail (only very rough and extrapolated figures), with a differing engine fitting running at less boost and less power makes much less sense.

While there's a simply and logical explanation as to why how the V15a/official specs relate to the other tests, which is supported by the results themselves, the other way is simply to ignore a few tests in favour for the lowest possible values anyone can find.

Curiously, the most loud supporters of this agenda are the same people who want RAF planes modelled after the highest possible results, and ignore all but the most favourable data.

One thing that was brought up in the last thread, that the aircraft would be "failed" and sent back to Messerschmitt if they did <475kmh at SL. However, the 109G acceptance plot posted in this thread shows testing at a single altitude that varies but is closer to FTH than SL. It makes sense to me that acceptance tests would not be based on a full speed vs alt test regime, and especially not an actual test of the 109 belting along at sea level (a bit difficult to arrange except in CloD). So a 109 doing 470kmh at SL could still pass.

Yes of course there were a lot of 109E's that just passed the minimum specs and were still accepted into service. So were Spitfires and Hurricanes. So why should be 109Es modelled after the worst possible specs instead of the nominal/guaranteed/tested and confirmed specs, while Spitfires and Hurricanes get special treatment and are modelled in optimistic conditions? Especially as the CLOD engine models wear of the airframe, so worn/badly manufactured planes and the scatter in performance can be easily modelled...?

The other thing is considering 1.3ata vs 1.35ata. If the actual limit was 5 mins 1.3ata without the takeoff boost, I don't see that the fact the CloD 109s show 1.35ata suggests they should be made faster than historical (although we are getting toward hair splitting). Instead the CloD boost indication should be fixed or ignored. In the same way if the CloD Spit boost gauge showed +14psi, I wouldn't expect it to be made faster than historical to match the gauge.

The Spitfire II analouge is limping, since it essentially says that if the performance doesn't match the engine outputs, decrease the engine output until it matches the wrong speed. It's akin to say that if Spitfire speeds do not match the +12 performance levels, but they match the + 6 1/4 boost, simple set the gauge to show 6 1/4 (which is unfortunately the current situation in the sim). Moreover the Spitfire I / II had only one type of engine fitted (M III or XII).

The Me 109E in contrast had at least four fitting and used during the Battle of Britain, with different boost and outputs.

The DB 601A-1 with the old type supercharger, 1.30 ata for five min and 990 PS, and 1.40 ata for 1 min and 1100 PS. Rated altitude being 4000m.

The DB 601A-1 with the new type supercharger, 1.30 ata for five min and 990 PS, and 1.40 ata for 1 min and 1100 PS. Rated altitude being 4500m.

The DB 601Aa with the old type supercharger, 1.35 ata for five min and 1045 PS, and 1.45 ata for 1 min and 1175 PS. Rated altitude being 3700m (altitude output was otherwise very much like the DB 601A-1 / old s/c, though it is an open question wheter the new s/c was fitted to the Aa as well. So far no evidence to that though.)
This is the type we have in the sim.

The DB 601N, 1.35 ata for five min and 1175 PS. Rated altitude being 4800m. (there was a second type of 601N, mounted in one in the 109F had better supercharger and IIRC 5200 m rated altitude)

Therefore, it is pointless to compare our 601Aa equipped Emils performance (1.35ata) to real life tests of DB 601A-1 equipped Emils at 1.3ata. It should of course match the real life DB 601Aa at 1.35ata (V-15a, Baubeschreibung "5%" specs, Swiss trials of serial no. 2404)

One thing I really find interesting for 109s is combat use of the 1 minute takeoff boost. Whether or not it actually works except close to SL really depends on how it is designed...similarly to difference between the actual Spit II gated takeoff boost (will decay quickly with alt) and red tab combat boost (will work at any alt the supercharger is capable of delivering it).

Right now the 1.45ata works even up to FTH (odd), which seems very unlikely. But in real life it should certainly work if you are chasing or being chased low over the channel, but I have not seen a combat report or memoir that confirms this.

The 109's 1-min Startleistung of 1.45ata worked different from the Spit II gated boost: like the Spitfire I, it had an automatic boost control which maintained 1.45ata up to near rated altitude. The primary difference was, evidenced from the DB 601Aa power curves is that just above the 1st supercharger speed, the power output with the 1 min rating suddenly dropped quickly, and although it still brought some very marginal power increase.

This, along with the description of device makes it clear that the system employed a sort of fixed charge enrichment, providing a very rich mixture ratio to boost power for takeoff and low level. It was probably fixed for an optimum at supercharging ratio in the 1st gear of the engine, which became unsuitable as altitude increased to provide reasonable increase and there was no automatic mixture compensation for the 1-min rating. It could still be used up to near FTH, up to where the supercharger was phyisically capable delivering 1.45ata (I would guess - ca 3400-3500m in case of the 601Aa)but the decription notes that it only leads to increased fuel consumption and strain with very little increase in output. The manuals prescribe it's use only for takeoff, but its also evident from the warnings that there is no physical difficulty in using it any other time.

So there's not much wrong with the 1-min rating being usable up to FTH, what is wrong is how it's modelled. At low altitudes, it should bring a MUCH more noticable boost in power than currently, given that it boosts the engine by 110-130 HP, but above ca. 1.5 km it should amount next to nothing (with fuel consumption still being sky high).

Hope this helps.

[camber]

Thank you Kurfurst for the helpful reply and Holzauge for the extra calculation info.

Originally Posted by Kurfürst

Yes of course there were a lot of 109E's that just passed the minimum specs and were still accepted into service. So were Spitfires and Hurricanes. So why should be 109Es modelled after the worst possible specs instead of the nominal/guaranteed/tested and confirmed specs, while Spitfires and Hurricanes get special treatment and are modelled in optimistic conditions? Especially as the CLOD engine models wear of the airframe, so worn/badly manufactured planes and the scatter in performance can be easily modelled...?

This is a good point, made critical by the fact of having a single aircraft cloned exactly across the whole battle theatre is rather unhistorical really. My position is that the (may he exist) CloD FM czar should make a good faith attempt to find an "average" performing variant (which will always incorporate some subjective calls), then fiddle within plausible historical performance ranges to make CloD work best.

With the 109E, my position is that based on what flight testing/ etc. information is available, at 1.3ata the SL performance was around 475kmh. This close pass/fail performance on the Messerschmitt chart was however not an issue because the acceptance was based on an altitude performance test, where the typical 109E was close to the guaranteed average spec. I think we maybe overstate how important SL top speed was to the Luftwaffe of the time, as they were overwhelmingly interested in altitude performance, where the 109 performed inspiringly. In CloD however we like to chase each other just above the deck a lot more, I suspect.

Originally Posted by Kurfürst

The Spitfire II analouge is limping, since it essentially says that if the performance doesn't match the engine outputs, decrease the engine output until it matches the wrong speed. It's akin to say that if Spitfire speeds do not match the +12 performance levels, but they match the + 6 1/4 boost, simple set the gauge to show 6 1/4 (which is unfortunately the current situation in the sim). Moreover the Spitfire I / II had only one type of engine fitted (M III or XII).

I agree, the situation is a bit theoretical anyway because FM fine-tuning may not occur anyway in CloD. I do think (if we had to choose what was fixed) that it is better to have the aircraft end performance historical with wrong boost indications, rather than correct performance but for an unhistorical boost. Which brings us to the next point, about what boost the 109E SHOULD have:

Originally Posted by Kurfürst

The Me 109E in contrast had at least four fitting and used during the Battle of Britain, with different boost and outputs.

The DB 601A-1 with the old type supercharger, 1.30 ata for five min and 990 PS, and 1.40 ata for 1 min and 1100 PS. Rated altitude being 4000m.

The DB 601A-1 with the new type supercharger, 1.30 ata for five min and 990 PS, and 1.40 ata for 1 min and 1100 PS. Rated altitude being 4500m.

The DB 601Aa with the old type supercharger, 1.35 ata for five min and 1045 PS, and 1.45 ata for 1 min and 1175 PS. Rated altitude being 3700m (altitude output was otherwise very much like the DB 601A-1 / old s/c, though it is an open question wheter the new s/c was fitted to the Aa as well. So far no evidence to that though.)
This is the type we have in the sim.

The DB 601N, 1.35 ata for five min and 1175 PS. Rated altitude being 4800m. (there was a second type of 601N, mounted in one in the 109F had better supercharger and IIRC 5200 m rated altitude)

Therefore, it is pointless to compare our 601Aa equipped Emils performance (1.35ata) to real life tests of DB 601A-1 equipped Emils at 1.3ata. It should of course match the real life DB 601Aa at 1.35ata (V-15a, Baubeschreibung "5%" specs, Swiss trials of serial no. 2404)

This is a really interesting point. Googling back, I see the DB601Aa is a bit controversial in discussions going back a long way, in that is it just only an export version, or was it widely used in Luftwaffe 109s. As you say, CloD seems to have put a DB601Aa in every 109E on the channel coast, which seems an odd choice but not a demonstrably wrong one (like a Me262 Jumo jet engine would be ). If I was CloD FM czar, I would consider re-engining all 109s to one of the DB601 A-1 variants and giving it 1.3 ata 475kmh/560kmh performance. If I stuck with the 1.35ata DB601Aa, I would increase speeds by an appropriate theoretically derived increment from the extra 0.05ata (e.g. using the formulae Holzauge provided), thus using the 1.3ata 109 data as a baseline.

Going on to the extra boost:

Originally Posted by Kurfürst

The 109's 1-min Startleistung of 1.45ata worked different from the Spit II gated boost: like the Spitfire I, it had an automatic boost control which maintained 1.45ata up to near rated altitude. The primary difference was, evidenced from the DB 601Aa power curves is that just above the 1st supercharger speed, the power output with the 1 min rating suddenly dropped quickly, and although it still brought some very marginal power increase.

(snip)

So there's not much wrong with the 1-min rating being usable up to FTH, what is wrong is how it's modelled. At low altitudes, it should bring a MUCH more noticable boost in power than currently, given that it boosts the engine by 110-130 HP, but above ca. 1.5 km it should amount next to nothing (with fuel consumption still being sky high).

That seems reasonable to me, provided the 1.45ata FTH is reduced to the correct level (below 1.35ata FTH) for the supercharger capability. Right now in CloD the 1.45ata seems to be still working when around the 1.35ata FTH (without changing rpm). The one thing that concerns me is that I haven't read reports of 109 drivers reaching first for their clockwork boost buttons when in a sticky situation, in the same way RAF drivers went straight for the boost lever or tit.

Cheers,
camber