Could the Bf 109 E really out-turn the Spitfire Mk I? (9 Viewers)

[Holtzauge]

How would the radius be 20% smaller the load-factor is the same, the turn time is the same, and at any one point in the circle we are going the same speed? It seems that 20% value is quite high and beyond what I would expect.

Can't remember saying the load factor was the same? When we were talking about the Bf 109 K-4's sustained turn performance, we were only comparing turn rate in deg/s and radius in meters. And we concluded that the turn rate was close, but that the turn radius in the C++ simulation was 20% larger than what it was in War Thunder. For arguments sake, let's assume both have approximately the same turn rate. This then simply means that the speed for best turn rate is 20% larger in the C++ simulations.

 

[Squish]

Can't remember saying the load factor was the same? When we were talking about the Bf 109 K-4's sustained turn performance, we were only comparing turn rate in deg/s and radius in meters. And we concluded that the turn rate was close, but that the turn radius in the C++ simulation was 20% larger than what it was in War Thunder. For arguments sake, let's assume both have approximately the same turn rate. This then simply means that the speed for best turn rate is 20% larger in the C++ simulations.

I am comparing the radius in the instant turn rate test because that is what I have the most data for. At any one point in the turn both of the planes are in similar positions.

What I suspect is that the way the turn radius is calculated via Starshark or WTRTI (the HUD program you see in the video) might be erroneous. I will check later since I think I have a method.

 

[Squish]

I am comparing the radius in the instant turn rate test because that is what I have the most data for. At any one point in the turn both of the planes are in similar positions.

What I suspect is that the way the turn radius is calculated via Starshark or WTRTI (the HUD program you see in the video) might be erroneous. I will check later since I think I have a method.

Holtzauge the radius in the game is 480m - 500m using manual testing.

Do you have any data on P-51 radius that we can compare against?

 

[Holtzauge]

S Squish : When I did the earlier C++ simulations for the instantaneous turns, we were comparing to Messerschmitt's estimate which is capped at a Clmax of 1.13. And while this is quite appropriate for the initial parts of the high speed instantaneous scenario due to Mach limitations, it is far too conservative for the sustained turn estimate. Unfortunately, I forgot to remove this cap when I did the the earlier C++ sustained turn estimates, and while at this speed there will still be a slight reduction of the low speed Clmax of a bit over 1.4, it will by my simulation estimate still allow the Bf 109 K-4 to reduce its turn radius to around 465 m, which is then not that far off from the 440 m figure you mentioned earlier. And in summary, any difference at around 5% has got to be said to be quite satisfactory, given that both my C++ simulations and War Thunder's flight models are both based on calculations and estimates.

Then about the P-51 D: Unfortunately, I do not have any similar calculations or estimates as we have for the Bf 109 K-4's instantaneous turn. And if anyone has some data here, that would of course be most welcome.

 

[Squish]

S Squish : When I did the earlier C++ simulations for the instantaneous turns, we were comparing to Messerschmitt's estimate which is capped at a Clmax of 1.13. And while this is quite appropriate for the initial parts of the high speed instantaneous scenario due to Mach limitations, it is far too conservative for the sustained turn estimate. Unfortunately, I forgot to remove this cap when I did the the earlier C++ sustained turn estimates, and while at this speed there will still be a slight reduction of the low speed Clmax of a bit over 1.4, it will by my simulation estimate still allow the Bf 109 K-4 to reduce its turn radius to around 465 m, which is then not that far off from the 440 m figure you mentioned earlier. And in summary, any difference at around 5% has got to be said to be quite satisfactory, given that both my C++ simulations and War Thunder's flight models are both based on calculations and estimates.

Then about the P-51 D: Unfortunately, I do not have any similar calculations or estimates as we have for the Bf 109 K-4's instantaneous turn. And if anyone has some data here, that would of course be most welcome.

The 440m figure was slightly inaccurate. Doing manual testing showed a radius of around 480m which is about in line with the level of variation I expect from Starshark.

All in all I think it's one of the better representations out there as far as the major video games are concerned. Certainly better than most would expect.

 

[bada]

I assume that the "Il-2 Sturmovik" mentioned earlier was the so-called "Great Battles" edition, not the older (2001) original.

Just for info, the old game (nowadays called Il-2 Sturmovik 1946) has a cool utility called IL2 Compare. Among other parameters, it contains turn times and speeds with/without flaps. The utility was developed for several game versions, including modded versions such as HSFX, Ultrapack and BAT. There is even an Android app.

In 2008 (somewhere around that year) a guy having extracted the FM part did notice that il2-compare wasn't actually accurate, it didn't took all the FM params into account.
The guy build a mod to extract the FM params and the data to make new Graphs using directly the full FM calculations. (still got it on my drive, for 4,09 with "sound-mod" )
This allowed to make much more precise FM's.
Anyway, All Tabular FM's have limitations, you can get one parameter exactly like the doc (like turn), but other parts won't be precise (like climb for example).
It's very hard to build a tabular fm's with less than 5% difference everywhere. There will be always one aspect that is screwed.
Tabulars FM's (il2-46/Box/CoD/WT) are always approximations. You simply can't get all the flight aspects right.

 

[Gilder]

The Germans did use captured British stocks of fuels. However, the 100 Octane fuel was mostly re-blended to suit the German requirements, ie mixed with lower grade stocks to get a larger quantity of medium grade.
There might have been some local misappropriation of the 100 Octane by someone but, it would not improve engine performance unless the engines were modified. If you have proof of this please show. Most likely, some was used without modification of aircraft or re-blending and made no difference, but the tale of using British fuel was started.
The uprated DB 601 N with higher compression, rpm and using C2 or C3 fuel (different original references say both) was coming into Bf 109 E4/N service in July 1940. The 601N engine appears to have had various modifications and standards during tho period 1940/1941and is tricky to tie down details. However, it was more powerful than the DB 601 A and it did use higher specification fuel. It is definitely known that the DB 601 A and N were allowed to use increased 2600 and 2800 U/min respectively in later 1940.
All Luftwaffe aircraft had fuel type triangle logo's by the refueling points.
German fuel blends changed many times during WW2.

Eng

Well I haven't found the reports which I mentioned (they are out there somewhere) but I did find something I wasn't looking for.

ME109E-3 c/n 1190, was operated by 4/JG26 based at Marquise-Est and normally flown by Hauptmann Karl Ebbighausen and carried the markings of his five kills. On 30th Sept it was flown by Horst Perez of when it was damaged in combat with Hurricanes and belly landed with minimal damage. It was taken to the RAE then Canada and the USA

I mention this as it had a fuel octane triangle showing 100 octane by the filler cap, not 87 or 95. The theory being that this would indicate that it had been modified to an E-6 tactical reconnaissance version.

This would make sense as most, if not all airforces, did almost anything they could to improve the performance of recce aircraft.

 

[Greg Boeser]

Well I haven't found the reports which I mentioned (they are out there somewhere) but I did find something I wasn't looking for.

ME109E-3 c/n 1190, was operated by 4/JG26 based at Marquise-Est and normally flown by Hauptmann Karl Ebbighausen and carried the markings of his five kills. On 30th Sept it was flown by Horst Perez of when it was damaged in combat with Hurricanes and belly landed with minimal damage. It was taken to the RAE then Canada and the USA

I mention this as it had a fuel octane triangle showing 100 octane by the filler cap, not 87 or 95. The theory being that this would indicate that it had been modified to an E-6 tactical reconnaissance version.

This would make sense as most, if not all airforces, did almost anything they could to improve the performance of recce aircraft.

Was that added after it was captured?

 

[Greyman]

Was that added after it was captured?

Seems like this is it (British Air Intelligence crash survey dated 4 Oct 1940)

(Report No.3/81)

Me.109E3.

Crashed on the 30.9.40. at East Dean. Map reference R.0115.

Markings 4+-. Marking had previously been <+. Crest; tiger's head in natural colours on the port side of fuselage. White shield with black F in addition. Yellow nose and fin.

Airframe built by Erla. Parts by Weser Flugzeugbau Works No.1190 date 18.9.39. Engine DB.601A made by Daimler Benz No.11954.

Armament; 2 20mm. cannons, 2 M.G.17's. Armour; normal cross bulkhead and pilot's head shield and canopy.

100 octane mark in triangle marked on fuselage.

Aircraft said to have been shot down by ground defences, a few strikes at angle of 45° in aircraft through cooling system. Pilot forced landed - prisoner.​

EDIT: just now looking at photos of both the museum paint job and photos of the actual crash site (which clearly shows a white shield with black S), I wanted to confirm the report does in fact say "white shield with black F". I wonder if the letter was misheard during dictation.

 

[Gilder]

Seems like this is it (British Air Intelligence crash survey dated 4 Oct 1940)

(Report No.3/81)

Me.109E3.

Crashed on the 30.9.40. at East Dean. Map reference R.0115.

Markings 4+-. Marking had previously been <+. Crest; tiger's head in natural colours on the port side of fuselage. White shield with black F in addition. Yellow nose and fin.

Airframe built by Erla. Parts by Weser Flugzeugbau Works No.1190 date 18.9.39. Engine DB.601A made by Daimler Benz No.11954.

Armament; 2 20mm. cannons, 2 M.G.17's. Armour; normal cross bulkhead and pilot's head shield and canopy.

100 octane mark in triangle marked on fuselage.

Aircraft said to have been shot down by ground defences, a few strikes at angle of 45° in aircraft through cooling system. Pilot forced landed - prisoner.​

EDIT: just now looking at photos of both the museum paint job and photos of the actual crash site (which clearly shows a white shield with black S), I wanted to confirm the report does in fact say "white shield with black F". I wonder if the letter was misheard during dictation.

That is the same one.

 

[Shortround6]

I do think that the patented Handley-Page Slat was originally a low-speed safety design, but the advantages of having wing performance aids have grown from that.

Well, there are number of British Biplanes that used Handley-Page Slats/slots before they were put on mono-planes so we can say it was a low speed safety device.
Another thing to be careful in how much of the wing had the slats, as in what percentage of the span was covered and then what area of the wing was affected.
Some planes used just enough slat to affect the wing where the ailerons were. Other planes put slats on a considerable portion of the wing but then we have to look at the amount of wing span the ailerons used.
Since Handley-Page held the patent they used slats on everything.
First 50(?) Halifaxes used slats.
Hampdens used slats.

The Ailerons on the Hamden stop just about where the Slats do.
Slats only affect the coefficient of lift of the wing behind the slats. On Hampden I have no idea if slats change the coefficient of lift over the entire cord the same or if it varies.

 

[Engineman]

Well I haven't found the reports which I mentioned (they are out there somewhere) but I did find something I wasn't looking for.

ME109E-3 c/n 1190, was operated by 4/JG26 based at Marquise-Est and normally flown by Hauptmann Karl Ebbighausen and carried the markings of his five kills. On 30th Sept it was flown by Horst Perez of when it was damaged in combat with Hurricanes and belly landed with minimal damage. It was taken to the RAE then Canada and the USA

I mention this as it had a fuel octane triangle showing 100 octane by the filler cap, not 87 or 95. The theory being that this would indicate that it had been modified to an E-6 tactical reconnaissance version.

This would make sense as most, if not all airforces, did almost anything they could to improve the performance of recce aircraft.

Hi,

There is no doubt that the Luftwaffe fuel triangle marking carried several different markings from photographs around the BoB, including the 100 mark. However, the presumption that this indicates the aircraft used British 100 Octane fuel and was modified for higher performance is speculative. Furthermore, the DB 601A engine is listed as fitted and this was rated to use the B4 87 Octane standard fuel. The Luftwaffe were quite strict in there adherence to the regulations and operation of their aircraft, and standard fuels were strictly controlled.
If the only evidence on this point you present is the 100 marking, then the detail of the why it is marked 100 is unknown. However, if you have other information to support your point, then it would be interesting to see.
As regards the possible use of higher octane fuel in the DB 601 engine in 1940, you will be aware that the Luftwaffe did this and the DB 601 A engine was not suitable for the simple
use of C2/C3 "100" Octane type fuels and higher Manifold pressure as the RR Merlin used with British 100 Octane. Daimler Benz had to modify the DB 601 A engine quite extensively
to run higher rpm and higher compression, they could not simply increase the Manifold pressure on the DB 601 A engine using their own high-Octane fuels and had to introduce the DB 601 N which came into service starting June 1940. So, what makes you think that a Luftwaffe unit in the field in September 1940 would be messing about with their own engine/fuel modifications to a DB 601 A that had been done by the Germans themselves at the factories and was available in Service as the DB 601 N? If you want to speculate, I think it is more likely that this aircraft had been fitted/uprated with a DB 601 N and either, it was mis-recorded as a 601 A by the British, or the 601 N engine had been changed back to a 601 A and the fuel triangle was still painted for the "100" (C2/C3). However, if you have more info, please post it.

Cheers

Eng

 

[Holtzauge]

In 2008 (somewhere around that year) a guy having extracted the FM part did notice that il2-compare wasn't actually accurate, it didn't took all the FM params into account.
The guy build a mod to extract the FM params and the data to make new Graphs using directly the full FM calculations. (still got it on my drive, for 4,09 with "sound-mod" )
This allowed to make much more precise FM's.
Anyway, All Tabular FM's have limitations, you can get one parameter exactly like the doc (like turn), but other parts won't be precise (like climb for example).
It's very hard to build a tabular fm's with less than 5% difference everywhere. There will be always one aspect that is screwed.
Tabulars FM's (il2-46/Box/CoD/WT) are always approximations. You simply can't get all the flight aspects right.

In connection to a discussion about how Il-2 did their FM modeling in their forums a few years back, one of the developers, confirmed that Il-2 as a base used a so-called polar diagram, i.e. a Cl versus Cd plot, and that this was then used to define the panels used in the in-game FM. And if you get the polar diagram right, then this will actually yield correct results for both, speed, climb and turn, i.e. all aspects if you will. However, as I understand it, in IL-2 the big issue was that it was troublesome to get all of this right when mapping to the panels, and that this could lead to the problems you describe. But other flight simulators like DCS and War Thunder etc, may have other methods to do this mapping thus avoiding the problems you describe.

And an even bigger problem is of course if the flight simulator developer already uses polar diagrams which are questionable from the beginning. And unfortunately, one of the bigger flight simulation developers seems to have introduced faults already in the simulation model as early as at the polar diagram stage, with some aircraft being close, and others far removed, and thus compounding the problems even more.

 

[Holtzauge]

Well, there are number of British Biplanes that used Handley-Page Slats/slots before they were put on mono-planes so we can say it was a low speed safety device.
Another thing to be careful in how much of the wing had the slats, as in what percentage of the span was covered and then what area of the wing was affected.
Some planes used just enough slat to affect the wing where the ailerons were. Other planes put slats on a considerable portion of the wing but then we have to look at the amount of wing span the ailerons used.
Since Handley-Page held the patent they used slats on everything.
First 50(?) Halifaxes used slats.
Hampdens used slats.

The Ailerons on the Hamden stop just about where the Slats do.
Slats only affect the coefficient of lift of the wing behind the slats. On Hampden I have no idea if slats change the coefficient of lift over the entire cord the same or if it varies.

Sure, Handley-Page style slats were probably initially put there on most aircraft to improve low speed handling and control close to stall.

And in connection to the Bf 109, as I pointed out before, this was to a large extent influenced by the sporting plane the Bf 108, which had about the same wing arrangement as the Bf 109, including the slats.

But the the point I was attempting to make earlier on, was not trying to say that the slats themselves improved turn performance as such, but that it looks like a lot of pilots when flying the Bf 109 did not in turns fly the aircraft aggressively enough to make the slats deploy. And if one was to speculate, many probably felt that the aircraft was about to stall when they started to come out, and were therefore reluctant to press the turn any harder.

And again, if you are making a turn in a Bf 109 only at the point at which the slats are just about to come out, then you are at a Cl of about 0.8, while the aircraft can go all the way up to about 1.4.

So the point was that some pilots seem to have been reluctant to do turns with the slats out, and thus not extracting all that the aircraft had to give.

 

[Gilder]

Hi,

There is no doubt that the Luftwaffe fuel triangle marking carried several different markings from photographs around the BoB, including the 100 mark. However, the presumption that this indicates the aircraft used British 100 Octane fuel and was modified for higher performance is speculative. Furthermore, the DB 601A engine is listed as fitted and this was rated to use the B4 87 Octane standard fuel. The Luftwaffe were quite strict in there adherence to the regulations and operation of their aircraft, and standard fuels were strictly controlled.
If the only evidence on this point you present is the 100 marking, then the detail of the why it is marked 100 is unknown. However, if you have other information to support your point, then it would be interesting to see.
As regards the possible use of higher octane fuel in the DB 601 engine in 1940, you will be aware that the Luftwaffe did this and the DB 601 A engine was not suitable for the simple
use of C2/C3 "100" Octane type fuels and higher Manifold pressure as the RR Merlin used with British 100 Octane. Daimler Benz had to modify the DB 601 A engine quite extensively
to run higher rpm and higher compression, they could not simply increase the Manifold pressure on the DB 601 A engine using their own high-Octane fuels and had to introduce the DB 601 N which came into service starting June 1940. So, what makes you think that a Luftwaffe unit in the field in September 1940 would be messing about with their own engine/fuel modifications to a DB 601 A that had been done by the Germans themselves at the factories and was available in Service as the DB 601 N? If you want to speculate, I think it is more likely that this aircraft had been fitted/uprated with a DB 601 N and either, it was mis-recorded as a 601 A by the British, or the 601 N engine had been changed back to a 601 A and the fuel triangle was still painted for the "100" (C2/C3). However, if you have more info, please post it.

Cheers

Eng

I can only present what I have found. The question which I would ask you is why Germany would put a 100 octane indicator on the fuel cap, if this aircraft wasn't able to use 100 Octane.

 

[Shortround6]

I can only present what I have found. The question which I would ask you is why Germany would put a 100 octane indicator on the fuel cap, if this aircraft wasn't able to use 100 Octane.

the question, to me anyway, is how did the 109 use the fuel?
The easiest way is to just use higher boost pressure which is fairly easy to do. Problem is that requires extra supercharger capacity. Which the DB 601 does not have a lot of.
DB 601 is making 4.4lbs of boost at 14,765ft. It can't make any more boost at that altitude or higher. It can make more boost lower but making 6lbs (1.4ata?) at 13,125 is not much help. you can get more the lower you go but that may require altering the supercharger drive.
In Nov 1940 they were approving the increased RPM but that was only for above the rated altitude, it was not for making more power at less than 4500 meters. This really puts the idea of using 100 octane fuel in trouble. Was the limit due to fuel (knocking/detonation) or was it the engine was not strong enough to last? If was engine strength then using 1.6 ATA or 1.8 ata( 12lbs boost) could mean a short flight.

 

[Engineman]

I can only present what I have found. The question which I would ask you is why Germany would put a 100 octane indicator on the fuel cap, if this aircraft wasn't able to use 100 Octane.

Hi,

Unfortunately, there was a whole host of fuel problems with the DB 601 N engine that first started being seen in about May 1940 due to the C3 fuel at that time being resistant to boiling off from the engine oil and continually diluting the oil. This caused serious reliability problems with the DB 601 N. So, there were huge issues with engine reliability at that time.
I feel that from what has "been found" in open sources till now is, that there are no known orders that specify the use and settings for adjustment of the DB 601 A or N engines to use captured British stocks of 100 Octane fuel. Further, the validity and specification by the RLM for a "100" fuel triangle indication is something that perhaps a specialist of that sub-topic might be able to shed some light?
In the meantime, I feel that it is purely speculative to claim that the 100 triangle indicates the use of British 100 Octane fuel, even less correct to speculate that this use was to achieve an undefined power increase in the engines, for which there is no known documentation.

Eng

 

[Engineman]

the question, to me anyway, is how did the 109 use the fuel?
The easiest way is to just use higher boost pressure which is fairly easy to do. Problem is that requires extra supercharger capacity. Which the DB 601 does not have a lot of.
DB 601 is making 4.4lbs of boost at 14,765ft. It can't make any more boost at that altitude or higher. It can make more boost lower but making 6lbs (1.4ata?) at 13,125 is not much help. you can get more the lower you go but that may require altering the supercharger drive.
In Nov 1940 they were approving the increased RPM but that was only for above the rated altitude, it was not for making more power at less than 4500 meters. This really puts the idea of using 100 octane fuel in trouble. Was the limit due to fuel (knocking/detonation) or was it the engine was not strong enough to last? If was engine strength then using 1.6 ATA or 1.8 ata( 12lbs boost) could mean a short flight.

The restriction of increasing the rpm was only above 5.5 km, not 4.5 km. The DB 601 A could increase from max 2400 to 2600, the DB 601 N could increase 2600 to 2800, only for the shortest time required, above 5.5km. The reason for not increasing at lower altitudes was that the superchargers at that time were relatively inefficient and there was excessive heating of the inlet charge at the higher supercharger speeds, pressures and ambient temperatures at lower altitudes. This is different to your description of the problem, it was not just a lack of Geblaseluftdruckdruck, it was that the extra heating would cause detonation problems.
Note, there is no mention of fuels used (which would be B4 for the 601 A and C3 for the 601 N) or the possibility of using British 100 Octane fuel or adjusting the engine controls.

Eng

 

[Gilder]

All, I have found the articles that I was looking for.

a) Document file number 043697, in the BP Archive at Warwick University, and specifically to 'Petroleum Board Enemy Oils Fuels Committee. A Survey of the Results Obtained to Date in the Examination of Enemy Fuel Samples', by D. A. Howes, dated 4 November 1940. This used fuel samples taken from 29 crashed Luftwaffe aircraft between November 1939 and September 1940, and, exclusive of one sample of captured British 100-octane, revealed octane ratings which varied between 87.5 and 92.2 octane. The results were summarised by H. E. Snow to Sir William Fraser on 13 November 1940 as follows (and I quote from the original document):

'No general indication [of] iso-octane or other synthetics. The only 100 octane fuel identified was definitely captured British.'

b) The Narrow Margin of Criticality: The Question of the Supply of 100-Octane Fuel in the Battle of Britain by Gavin Bailey

http://ehr.oxfordjournals.org/cgi/content/abstract/cen007

This paper concentrates of the origin, supply and distribution of 100 Octane fuel. Included in that is the distribution to the RAF in France and the capture of that fuel.

Note 1 - Gavin Bailey was a member of this Forum and gave us a considerable insight into this subject
Note 2 - There was a second paper which covered the analysis for the period after September 1940 which I cannot find. But that was less relevant anyway.

General point
I think we know which German aircraft had the 100 octane in it, the one that crash landed at East Dean. As you are aware, I believe that you put the warning sign on the fuel to ensure that the right fuel goes into the right aircraft.
You may consider it speculative for me to say that, but unless you can come up with a reason as to why you would put a 100 Octane warning on a plane that can only use a different fuel I would consider my position to be a strong working assumption.
I do not pretend to know what technical changes would be needed to make a DB601 run on 100 octane, all I do know, is that the changes to make the Merlin run on 100 Octane were fairly minor and done at squadron level.

I hope the above helps

 

[Squish]

But other flight simulators like DCS and War Thunder etc, may have other methods to do this mapping thus avoiding the problems you describe.

War Thunder and il2 light models are going to be very similar in so far that they use drag pullers to create them. War Thunder can trace its lineage directly back to some of the original il2 games. The War Thunder developer was originally subcontracted to develop an il2 title for the Xbox 360.

The lead developers for both games went to the same University in Moscow.

Once again you do run into the issues of it is not simply finding the correct drag puller and copy and pasting it into their flight model programming. Doing so will oftentimes give you erroneous results that do not match real world data. This becomes especially problematic when they are using publicly available. Clcd diagrams that are derived from computational studies. Find three different computational studies of a modern jet fighter clcd diagram and you will have three very different results depending on who ran the simulation and how it was built.

The Dynamics in il2 for the 109 versus p51 r fairly similar to the Dynamics between the p51 and 109 in War Thunder. However, in War Thunder, I feel that the p51 has an easier time accelerating away from and resetting a position against the bf109.