Could the Bf 109 E really out-turn the Spitfire Mk I?

[Holtzauge]

It made sense, but probably didn't apply to most Hartmann's opponents since he entered combat when VVS largely transferred to newer equipment.

Edit: I was wrong. Quickly checked - there were many early Yaks and LaGG-3s in his early records. M-105 engine with a float carburettor.

Actually, I don't know how often he actually used it?: AFAIK, as a rule, he did everything he could to avoid dogfights, but that this was supposedly his last ditch defense if he ever got an enemy on his tail. I may be wrong, but IIRC then he used this when he was attacked by a bunch of Mustangs late in the war? And in that case, the aim was probably not to try to cause the pursuers engines to cut out, but simply to provide an "unattractive" target.

 

[Engineman]

When you mention automatic flaps on the Bf 109 E, I'm assuming you mean slats right? First of all properly adjusted slats come out gradually (the slat control risers are aligned so that they do this) and are hardly perceptible for the pilot. I am familiar with what Eric Brown said about them, and that they came out with a "bang", but those were most likely poorly adjusted and maintained. In fact, this is also described in German literature: Gaps and linkage/rollers need to be properly adjusted or they do not function as intended. In addition, I've seen a 360 deg cockpit video of Sywell's Buchon, and in which you can study both the stick and slats, and there is basically no impact at all on the stick when they come out.

Then about the stall properties of the Bf 109 E as compared to the Spitfire: Different sources say different things about this, but the slats were a definite advantage in roll control at and post stall in the Bf 109. Finally, yes, as a rule, the Spitfire and Hurricane Mk I's turned much better than the Bf 109 E. And which is why I point out that my video is about the exception to the rule.

About which armament is best I'll take a pass on that. And I think that such a complex analysis warrants a thread on its own actually.

Agree about the slats. The Bf 109 E type were mounted on paired swinging arms at each end and were linked by a coupling tube that made both the ends move together. The set up requires care for free movement.
The Bf 109 F onwards had the slats mounted on rollers moving in tracks. Each end could move independently and they could, if the airflow required it, move fully out at either end with the other end still in without jamming if set-up correctly.
Modern experience is that if set-up correctly, the slats deploy smoothly and proportionally to Alpha.
I think the armament discussion is mostly a pov thing. There are pro's and con's. However, I note that the Germans had more experience of modern combat by 1940 and chose
the heavier cannon over the MG. Personally, I would prefer the cannon.

Eng

 

[Gilder]

When you mention automatic flaps on the Bf 109 E, I'm assuming you mean slats right? First of all properly adjusted slats come out gradually (the slat control risers are aligned so that they do this) and are hardly perceptible for the pilot. I am familiar with what Eric Brown said about them, and that they came out with a "bang", but those were most likely poorly adjusted and maintained. In fact, this is also described in German literature: Gaps and linkage/rollers need to be properly adjusted or they do not function as intended. In addition, I've seen a 360 deg cockpit video of Sywell's Buchon, and in which you can study both the stick and slats, and there is basically no impact at all on the stick when they come out.

Then about the stall properties of the Bf 109 E as compared to the Spitfire: Different sources say different things about this, but the slats were a definite advantage in roll control at and post stall in the Bf 109. Finally, yes, as a rule, the Spitfire and Hurricane Mk I's turned much better than the Bf 109 E. And which is why I point out that my video is about the exception to the rule.

About which armament is best I'll take a pass on that. And I think that such a complex analysis warrants a thread on its own actually.

Apologies you are correct, I was referring to the slats.

I am also aware of the comments of Eric Brown but these are supported by the observations made in the Official Handling and Manoeuvrability tests made in Sept 1940 on an Me109E. The Summary I have copied below.

Aileron snatching is specifically highlighted although its my belief that this was addressed to some degree with later versions of the Me109. It wasn't a problem with adjustment or maintanence of the plane in question.

The heaviness on the controls was always a problem until the end

Messerschmitt Me. 109 Handling and Manoeuvrability Tests
BY
M. B. MORGAN, M.A. and D. E. MORRIS, B.SC.

Summary. – Reasons for Enquiry. – Comprehensive handling and manceuvrability tests were required on the Me. 109, for comparison with similar tests already made on other modem single-seater ghter6,7,8,9. The performance of a captured Me. 109 was measured in France, and the aircraft then flown to England for these further tests.
Range of Investigation. – The handling tests covered the following ground : – ease of take-off and landing ; trim and stability ; " one control " tests, flat turns and sideslips ; stalling tests, including a determination of CLmax ; high-speed dive ; harmony and " feel " of the controls.
An investigation of the fighting qualities of the Me. 109 included dog fights with Hurricanes and Spitfires, measurement of aileron forces and times to bank at speeds up to 400 m.p.h., and an analysis of the turning performance of the aircraft.
Pilots' views on cockpit layout, comfort and view are given in an Appendix to the report.
Conclusions. – (i) Take-off is fairly straightforward. Landing is difficult until the pilot gets used to the aircraft.
Longitudinally the aircraft is too stable for a fighter. There is a large change of directional trim with speed. No rudder trimmer is fitted ; lack of this is severely felt at high speeds, and limits a pilot's ability to turn left when diving.
Fin area and dihedral are adequate. The stall is not violent, and there is no subsequent tendency to spin. CLmax is 1.4, flaps up and 1.9, flaps down. No vibration or " snaking " develop in a high-speed dive.
Aileron snatching occurs as the slots open. All three controls are far too heavy at high speeds. Aerobatics are difficult.
(ii) The Me. 109 is inferior as a fighter to the Hurricane or Spitfire. Its manoeuvrability at high airspeeds is seriously curtailed by the heaviness of the controls, while its high wing loading causes it to stall readily under high normal accelerations and results in a poor turning circle.
At 400 m.p.h. a pilot, exerting all his strength, can only apply 115 aileron, thereby banking 45 deg. in about 4 secs. From the results Kb, for the Me. 109 ailerons was estimated to be - 0.145.
The minimum radius of turn without height loss at 12,000 ft., full throttle, is calculated as 885 ft. on the Me. 109 compared with 696 ft. on the Spitfire.
The cockpit is too cramped for comfort.

I also found the following

Spitfire and Me.109 Turns at minimum radius without height loss. Both aeroplanes at full throttle at 12,000 ft.

	Spitfire​	Me.109​
Minimum radius of turn without loss of height. ft.	696​	885​
Cooresponding time to turn through 360 deg. sec.	19​	25​
Indicated airspeed Vi m.p.h.	133​	129​
A.S.I.R. approx m.p.h.	126​	118​
"g"	2.65​	2.1​
Angle of bank	68 deg.​	62 deg.​

 

[Squish]

S Squish : While interesting to watch, the Warthunder clips you posted are a bit optimistic as well aren't they? While in IL-2 the low speed handling with flaps out may be a bit optimistic, I would suspect that that half loop ( 7-10 g's?) you started off with from about 700 km/h on the deck and which took just a couple of seconds is not what most WW2 pilots would have done either.

But other than that, it is difficult to judge how well the energy retention and speed loss in the turns you both do in those clips is modeled. But that I think is key: This needs to be close in a simulator, or else you are just playing a game.

I attach an instantaneous turn history that I used myself for validation of my simulation model.

Could you perhaps do tests flights in-game in Warthunder and see how well it replicates?

Since this particular scenario is something Messerschmitt themselves assumed, it would be interesting to see how well it replicates in Il-2 and Warthunder (and DCS for that matter).

View attachment 886465

What is the reference weight / fuel state for the Messerschmitt test? What is the ATA setting?

Just at a glance I can tell you that the turn time in WarThunder will probably be in the ballpark depending on the weight it's taken at. Turn performance at 5000-6000m is much worse than at sea level. That will be doubly true for higher fuel state.

 

[Engineman]

Reading the RAE report they mention the Bf 109 E aileron droop I have previously noted:
"When the flaps are up the ailerons have a droop of 1.2 deg. and a 2:l differential (maximum angles 13.5 deg. down and 25 deg. up). As the flaps are lowered both ailerons come down progressively, and when the flaps are fully lowered (42.5 deg.) both ailerons come down 11 deg.; the differential is now slightly less. Fig. 9 shows the aileron-stick gearings for three flap settings (0 deg., 20 deg. and 420 5 deg.)."

Further into the report there are some "tactical" trials. Reading these, it would seem that there was little to fear for Spitfire and Hurricane pilots!
"The Me.109 pilot summed up his general impressions of the aircraft as a fighter in the following manner. "From all this dog-fighting I am certain that if the pilot of a Hurricane or Spitfire finds himself attacked by a Me.109 he can easily out-turn it, and can lose it straight away by doing any violent manoeuvre,; the Me.109 just cannot be made to do a really quick manoeuvre because at high speeds the controls are much too heavy, and at low speeds the slats come out, causing the ailerons to snatch, followed by the aircraft stalling if the manoeuvre is done more rapidly. "

Eng

 

[drgondog]

Reading the RAE report they mention the Bf 109 E aileron droop I have previously noted:
"When the flaps are up the ailerons have a droop of 1.2 deg. and a 2:l differential (maximum angles 13.5 deg. down and 25 deg. up). As the flaps are lowered both ailerons come down progressively, and when the flaps are fully lowered (42.5 deg.) both ailerons come down 11 deg.; the differential is now slightly less. Fig. 9 shows the aileron-stick gearings for three flap settings (0 deg., 20 deg. and 420 5 deg.)."

Further into the report there are some "tactical" trials. Reading these, it would seem that there was little to fear for Spitfire and Hurricane pilots!
"The Me.109 pilot summed up his general impressions of the aircraft as a fighter in the following manner. "From all this dog-fighting I am certain that if the pilot of a Hurricane or Spitfire finds himself attacked by a Me.109 he can easily out-turn it, and can lose it straight away by doing any violent manoeuvre,; the Me.109 just cannot be made to do a really quick manoeuvre because at high speeds the controls are much too heavy, and at low speeds the slats come out, causing the ailerons to snatch, followed by the aircraft stalling if the manoeuvre is done more rapidly. "

Eng

and somehow many Spits and Hurricanes were lost dogfighting the Bf 109E, Te report also fails to mention that few fights engaged with and sustained high speeds.

 

[Gilder]

For a different perspective, here are what I have for the German comparison tests. There is one observation I would make before reading it. There are a number of comments about the Hurricane and Spitfire having Two Pitch propellors. By the time the BOB began, the RAF had made two significant changes to the RAF fighters which seriously improved their performance.
1) The RAF fighters had changed to 100 octane fuel which improved the power of the engine from around 1,000hp to 1,300hp at their rated heights.
2) Constant speed propellors had replaced the Two Pitch props which meant that the aircraft would always make best use of that power.

neither of these changes are reflected in this review.

From : Kr.-Fernschr.Ob.d.L.,Führ.Stab Ia Nr.8092/40 g.K. (II)
(only to Lfl.3)

Subject : Comparison flight between Bf 109 E, Bf 110 C, Spitfire, Hurricane and
Curtiss.

In the following the performance- and air combat comparison that has been performed
at the E-Stelle Rechlin between Bf 109 E and Bf 110 C and the captured enemy fighters
Spitfire, Hurricane and Curtiss shall be brought to acknowledgement. The results of
the comparison are to be announced immediately to all Jagd- and Zerstörer units under
command, to guarantee the appropriate air combat behavior in the engagements on the
basis of technical conditions.

The Bf 109 E type clearly outperforms all foreign planes:

Speed: the Spitfire is at 0 m by ca. 20 km/h, at 4 km by ca. 10 km/h, Hurricane and
Curtiss at 0 and 4 km altitude by ca. 60 km/h. A similar superiority of the Bf 109 E
exists in the climb performance as well. Climb times to 4 km:
Bf 109 E 4.4 min, Spitfire 5 min, Hurricane 5.6 min, Curtiss 5.2 min.

The plane Bf 110 C is speed-wise inferior to the Spitfire, superior to the Curtiss
and Hurricane. Regarding the climb performance is the Curtiss equal at ground level,
up to 4 km superior then inferior. Hurricane is inferior up to altitude 2 km, then
superior up to 6.5 km. Spitfire is equal at ground level, otherwise superior.

The best climb for Bf 109 E and Bf 110 C is achieved with shallow climb angle
and higher speeds than at the enemy fighters. It is wrong to climb away steep or climb
behind an enemy fighter with the same angle.

Before turning fights with the Bf 109 E type, it must be noted in every case, that
all three foreign planes have significantly smaller turning circles and turning times.
An attack on the opponent as well as disengagement can only be accomplished on the basis of
existing superiority in performance.

For this the following suggestions are given:

The Spitfire and partly the Hurricane have two-pitch propellers.
Climbing away with the Bf 109 and Bf 110 must be done with the best climbing speed or
even higher speeds of about 280 – 300 km/h. On aircraft with two-pitch propellers with
low blade angle the engine will experience a very high over-revolution, and on the other
hand with high blade angle high boost pressure – therefore in other words, performance loss.

On sudden push forward on stick to below, the carburetor of the enemy fighters cuts out
due to the negative acceleration. This [evasive] measure is also recommended.

The rolling ability of the enemy fighters at high speeds is worse than that of the Bf 109.
Quick changes of the trajectory along the vertical axis cause especially with the Spitfire
load changes around the cranial axis, coming from high longitudinal thrust momemtum, and
significantly disturb the aiming.

In summary, it can be said that all three enemy planes types are inferior to the German
planes regarding the flying qualities. Especially the Spitfire has bad rudder and elevator
stability on the target approach. In addition the wing-mounted weapons have the known
shooting-technique disadvantages.

 

[Engineman]

For a different perspective, here are what I have for the German comparison tests. There is one observation I would make before reading it. There are a number of comments about the Hurricane and Spitfire having Two Pitch propellors. By the time the BOB began, the RAF had made two significant changes to the RAF fighters which seriously improved their performance.
1) The RAF fighters had changed to 100 octane fuel which improved the power of the engine from around 1,000hp to 1,300hp at their rated heights.
2) Constant speed propellors had replaced the Two Pitch props which meant that the aircraft would always make best use of that power.

There are observations that should be made about the Bf 109 as well.
The statement that "The RAF fighters had changed to 100 octane fuel which improved the power of the engine from around 1,000hp to 1,300hp at their rated heights." is misleadingly phrased. The power of the engines was only improved below their original 6.25lb 87 Octane rated heights. The single stage Merlin at that time could only make the full 100 Octane increased Boost of 12lb at 9,000feet, by the previous rated altitude of 16,250feet they were right back to their 6.25lb boost and the same power as on 87 Octane. In some ways, the Germans did better, with some versions of the Bf 109 DB 601 engines having their rpm ratings raised to 2600rpm and so the rated altitude actually raised and their Manifold pressure limits also raised with their 96 Octane fuel.
The Bf 109 had had a VP propeller that allowed multi pitch settings for several years before the BoB. However, the German equivalent of the automatic Constant speed propeller was introduced during the BoB.

Eng

 

[Holtzauge]

What is the reference weight / fuel state for the Messerschmitt test? What is the ATA setting?

Just at a glance I can tell you that the turn time in WarThunder will probably be in the ballpark depending on the weight it's taken at. Turn performance at 5000-6000m is much worse than at sea level. That will be doubly true for higher fuel state.

A test setup in a simulator matching this scenario would be with the Bf 109 K-4 being at 50% fuel and with a full internal ammunition load, and at 1.8 ata Notleisting, starting off at 180 m/s in TAS (648 km/h TAS) at 6 km altitude in standard atmospheric conditions, maintaining altitude throughout the turn, initially only holding 5 g's even if more can be achieved, and then when the speed has bled off to the point that 5 g's cannot be maintained, then transition to riding the edge of stall throughout the rest of the turn.

Note that the German calculated example only encompasses about one complete turn. So I would suggest a few turn trials going a bit further just to be sure the complete turn is captured, and then post-processing the results to try to get some sort of average. And since we have data points for both the German WW2 calculation and the C++ simulations at 7, 12, 18 and 24 seconds, it would of course be good if we could extract that as well from any in-game trials.

A bonus would be if we also could have video both from the cockpit showing control movement and pilot's view, and also an external view so that reference points are visible, and so it's clear that altitude and loadfactor is maintained throughout.

I realize that to get all of this absolutely right is probably just not possible, but I think we could even so from something that is sufficiently close in an in-game trial still be able to see how close the in-game results are to the performance as estimated by Messerschmitt themselves.

Edit: Added info about full ammunition load.

 

[Holtzauge]

Some more input on why you sometimes need to take what you read in a report with a grain of salt:

Excerpt from Wing Commander George H Stainforth's report "Report on investigation of turning circles of M.E. 109, Spitfire and Hurricane", dated 9th​ June 1940, covering the Bf 109 E:

"Tightening up beyond a certain point resulted in the slots opening unevenly and lateral flickering and slowing down of the rate of turn. The maximum rate of turn was obtained with the slots just about opening, either both just closed or both just open, and at the maximum rate of turn the Hurricane remained close to my tail."

And this is just plain wrong. The maximum turn rate and minimum radius on the Bf 109 E is achieved when the slats are fully out at the altitude these tests were done at. And the pilot doing the test was probably just not familiar with the aircraft and therefore did not fly it properly. As simple as that.

So the lesson here is I think, that even the sun has its spots, and just because a report if published by the RAE or the German ZWB, that this is no guarantee that everything in them can be taken at face value. In fact, there is also a NACA report that claims that the Spitfire's pleasant handling at low speed was bought at the cost of a Clmax being as low as 1.2. However, this was later shown to be a IAS calibration error by the Americans, and refuted by the British aerodynamicist M B Morgan, who pointed out that it was not at all low for its type, and actually as high as 1.36 when properly measured by a trailing pitot system.

Then more about the Bf 109 E's slats: In addition to what I wrote about them in an earlier post, i.e. that them coming out unevenly, snatching and with a bang, are all clues that they were poorly adjusted. Is not only as witnessed by German sources (Report VB 109 10 E 42, and also in Hoerner's Fluid Dynamic Drag book), but I have actually also seen this for myself (their smooth operation) in a private 360 deg cockpit view video recording of a flight with Sywell's two-seat Buchon from about 4 years ago. And in this video, you can view both the slats and the stick, and see that there is no disturbance whatsoever when they go in and out. In fact, the well known British Warbird pilot Paul Bonhomme, who was pilot in command in this flight, demonstrated them coming in and out in a shallow turn, and commented to the passenger about their carefree operation.

And G Gilder , connected to this, in a previous a post you said that the ailerons snatched on the Bf 109 E the RAE tested, and that "it wasn't a problem with adjustment or maintenance of the plane in question". Now how are you so sure about that? Can you elaborate on this please?

In addition, Paul Bonhomme had no trouble at all doing aerobatics in the video, thus contradiction the British RAE report referenced earlier which claimed that this was difficult in the Bf 109 E, since rather to the contrary, that a loop in the video was a very straightforward affair, only needing the speed to be sufficient and the stick pulled back. He even commented that the slats opened up somewhat on the way up, and then closed on the way down. And there was no perceptible effect on the stick that I could see, and the stick certainly did not "snatch".

Finally, since some post are now are starting to include testimony that the Hurricane and Spitfire Mk I turned better than the Bf 109 E, perhaps hinting that what I've been saying here and in my YouTube video somehow contradicts this, let me be crystal clear on this point: In general and as a rule, I agree that both British fighters HANDILY out-turned the Bf 109 E. And what the video shows, in an EXCEPTION to the rule, nothing else.

 

[Squish]

A test setup in a simulator matching this scenario would be with the Bf 109 K-4 being at 50% fuel, and at 1.8 ata Notleisting, starting off at 180 m/s in TAS (648 km/h TAS) at 6 km altitude in standard atmospheric conditions, maintaining altitude throughout the turn, initially only holding 5 g's even if more can be achieved, and then when the speed has bled off to the point that 5 g's cannot be maintained, then transition to riding the edge of stall throughout the rest of the turn.

I will attempt to duplicate the test in War Thunder later today.

I might substitute the Bf.109 G-14 or G-10 for the K-4 since those planes use 1.8 ATA in the game while the K-4 used 1.98 ATA setting. Results between all 3 will be practically identical for a given power setting.

 

[Holtzauge]

I will attempt to duplicate the test in War Thunder later today.

I might substitute the Bf.109 G-14 or G-10 for the K-4 since those planes use 1.8 ATA in the game while the K-4 used 1.98 ATA setting. Results between all 3 will be practically identical for a given power setting.

Great. But a word of caution so you don't do it in vain: I don't have time to check right now, but before you spend time doing the tests, make sure that the plane you test with has about the same weight as the K-4 (guns and ammo load, Erla canopy, RD and radio gear etc.) and that the 1.8 ata Full Throttle Height is the same as it was on the K-4's engine, since otherwise it will be hard to compare results.

 

[Engineman]

Great. But a word of caution so you don't do it in vain: I don't have time to check right now, but before you spend time doing the tests, make sure that the plane you test with has about the same weight as the K-4 (guns and ammo load, Erla canopy, RD and radio gear etc.) and that the 1.8 ata Full Throttle Height is the same as it was on the K-4's engine, since otherwise it will be hard to compare results.

There are subtle differences between the power of a DB 605 D set up for 1.98ata and another set up for 1.80ata (other than the full throttle power difference). Both ratings are at 2800U/min and the engine must be used in AUTOMATIK control, that gives 2800U/min at the full 110% throttle and 2600U/min at the 100% Throttle stop ( 2600/1.45 for both). Obviously, the engine set for 1.80 will achieve that at 2800, but the engine set for 1.98 will achieve 1.80 at less than 110% (less than full throttle travel) and so the U/min will be lower, possibly just 2700 and the power will be lower.
Also, there will be a difference if a 1.80 engine is not using MW50. Possible differences here are around 100PS.

Eng

 

[Squish]

Great. But a word of caution so you don't do it in vain: I don't have time to check right now, but before you spend time doing the tests, make sure that the plane you test with has about the same weight as the K-4 (guns and ammo load, Erla canopy, RD and radio gear etc.) and that the 1.8 ata Full Throttle Height is the same as it was on the K-4's engine, since otherwise it will be hard to compare results.

There will be discrepancies regardless but just doing some looking at starshark figures for minimum radius it looks like around 415m for the G-14/G-10 and 440m for K-4. Those figures don't appear to be radically different than the Messerschmitt chart if we are just looking at radius at the end of the turn as being close to min radius.

The sustained turn rate at this altitude for this configuration is around 12.5 degrees per second for all 3 aircraft with smallest fractional advantage in favor of G-10. The peak initial turn is around 19 degrees per second at around 570kph TAS.

In order to meet chart performance the averaged turn rate would have to be 15 degrees per second and I think that we will probably end up pretty close to that +/- 0.75 second depending on how AoA limit is treated.

 

[Gilder]

Some more input on why you sometimes need to take what you read in a report with a grain of salt:

Excerpt from Wing Commander George H Stainforth's report "Report on investigation of turning circles of M.E. 109, Spitfire and Hurricane", dated 9th​ June 1940, covering the Bf 109 E:

"Tightening up beyond a certain point resulted in the slots opening unevenly and lateral flickering and slowing down of the rate of turn. The maximum rate of turn was obtained with the slots just about opening, either both just closed or both just open, and at the maximum rate of turn the Hurricane remained close to my tail."

And this is just plain wrong. The maximum turn rate and minimum radius on the Bf 109 E is achieved when the slats are fully out at the altitude these tests were done at. And the pilot doing the test was probably just not familiar with the aircraft and therefore did not fly it properly. As simple as that.

I think that its a bit strong for any one of us today, to say that very experienced pilots of days gone by were not familiar with the aircraft and didn't fly it properly. Clearly a British pilot wouldn't be as familiar as a German pilot or the other way around. But any pilot who is an experienced test pilot would be able to carry out the tests and fly the aircraft well. We are not talking about average squadron pilots.
Back to the topic. No one would deny that the aircraft will fly with the best potential with the slots deployed, the problem was that the slots deployed automatically and it was common for one to deploy before the other, that was the problem. As mentioned this was worked on and my understanding was that this became more controlled as the the aircraft was developed in later versions.

And G Gilder , connected to this, in a previous a post you said that the ailerons snatched on the Bf 109 E the RAE tested, and that "it wasn't a problem with adjustment or maintenance of the plane in question". Now how are you so sure about that? Can you elaborate on this please?

This behaviour was mentioned in the pilots flying the Me109E, and later by Eric Brown who I believe was flying an Me109G-6, then it was common over a long period of time. The RAF had experience of slots and the units responsible for testing captured aircraft had ground crews experienced in the care and maintenance of foreign aircraft.
Also as you would expect the RAF captured a number of Me109's and its a fair assumption that they are going to use the best of them for testing.

Finally, since some post are now are starting to include testimony that the Hurricane and Spitfire Mk I turned better than the Bf 109 E, perhaps hinting that what I've been saying here and in my YouTube video somehow contradicts this, let me be crystal clear on this point: In general and as a rule, I agree that both British fighters HANDILY out-turned the Bf 109 E. And what the video shows, in an EXCEPTION to the rule, nothing else.

Totally agree

 

[Greg Boeser]

There are observations that should be made about the Bf 109 as well.
The statement that "The RAF fighters had changed to 100 octane fuel which improved the power of the engine from around 1,000hp to 1,300hp at their rated heights." is misleadingly phrased. The power of the engines was only improved below their original 6.25lb 87 Octane rated heights. The single stage Merlin at that time could only make the full 100 Octane increased Boost of 12lb at 9,000feet, by the previous rated altitude of 16,250feet they were right back to their 6.25lb boost and the same power as on 87 Octane. In some ways, the Germans did better, with some versions of the Bf 109 DB 601 engines having their rpm ratings raised to 2600rpm and so the rated altitude actually raised and their Manifold pressure limits also raised with their 96 Octane fuel.
The Bf 109 had had a VP propeller that allowed multi pitch settings for several years before the BoB. However, the German equivalent of the automatic Constant speed propeller was introduced during the BoB.

Eng

Chris Goss' Luftwaffe Fighters and Bombers - Battle of Britain has some interesting observations about the switch from VP to CS. More experienced pilots preferred the VP, but the CS was easier for newer pilots. I suppose in the same way an experienced driver with a manual shift tranny gets better performance than a neophyte.

 

[Squish]

Great. But a word of caution so you don't do it in vain: I don't have time to check right now, but before you spend time doing the tests, make sure that the plane you test with has about the same weight as the K-4 (guns and ammo load, Erla canopy, RD and radio gear etc.) and that the 1.8 ata Full Throttle Height is the same as it was on the K-4's engine, since otherwise it will be hard to compare results.

Here is a clip of the Bf.109 K-4 turn test in War Thunder. I was able to approximate the 1.8 ATA setting by removing some of the "engine modifications" which remove horsepower. However in this configuration the engine has a takeoff horsepower rating of 1713hp when the real engine should be around 1775hp. In-game the 1.98 ATA setting has takeoff rating of 1947hp.

It would be possible to repeat this test with engine setup to produce 1772hp in game. The power difference is around 3% difference and I don't think that re-doing it 10 times will produce radically different results. Completing the test itself is rather annoying because having to hit multiple test points in one turn without losing altitude perfectly is difficult; this is why StatShark basically exists for this game.


View: https://youtu.be/F7Uf9zr9b_I

All of the data should be readily visible in the center of the screen. I used the heading setting to index how far into the turn I was. I got a turn time of right around 22.25 seconds which lines up pretty closely with the Messerschmitt chart time of 23 seconds. I am using 23 seconds because in their chart the turn is established at 1 second whereas in my test it is established at 0 seconds. I have also applied the same correction to your chart as well for an apples-to-apples comparison.


This is the chart that I made based on the speeds in the MTT chart vs what I was seeing in WT.

There are a few factors that affect the WT comparions.
1. It is impossible to hold perfect altitude and perfect 5.0g schedule followed by perfect 15.0 AoA while using a flight-stick. I could repeat this test 20 times and the results will have a range of results.
2. Due to the fact that it is a 360 degree turn I think minor differences from test to test will equalize out; i.e pulling too hard at start will bleed energy and be slightly offset in end of turn.
3. The horsepower setting of the aircraft could be improved by 3% and would narrow the margins seen at the end of the test. Increased horsepower will also decrease the turn time as well.
4. My recorded data might be slightly skewed because I didn't do a frame-by-frame analysis. My data is based on taking the kph data and dividing by 3.6 to get to meters per second.

Here are my observed results.
1. The War Thunder flight model is in the ballpark. The turn time is 22.25 seconds vs 23 seconds in the calculation. At 23 seconds the plane has turned 375 degrees in the video game vs 360 degrees according to the calculation. This is around 4% better than it should be. That 4% margin only starts to develop once the aircraft gets to lower speed.
2. The energy retained by the end of the turn is 4% less than it should be. Part of this can be explained away with the missing 60hp. However mathematically speaking this relationship isn't linear so 3% more horsepower is not going to materialize as 3% more speed at the end of the turn; probably more in the order of 1.5%

 

[Holtzauge]

There are subtle differences between the power of a DB 605 D set up for 1.98ata and another set up for 1.80ata (other than the full throttle power difference). Both ratings are at 2800U/min and the engine must be used in AUTOMATIK control, that gives 2800U/min at the full 110% throttle and 2600U/min at the 100% Throttle stop ( 2600/1.45 for both). Obviously, the engine set for 1.80 will achieve that at 2800, but the engine set for 1.98 will achieve 1.80 at less than 110% (less than full throttle travel) and so the U/min will be lower, possibly just 2700 and the power will be lower.
Also, there will be a difference if a 1.80 engine is not using MW50. Possible differences here are around 100PS.

Eng

Yes, and this was the point I wanted to make before S Squish made any tests: For example, while the K-4 has a DB 605 D with a FTH of 6.8 km at 2600 rpm and no RAM, one G-14 version has a DB 605 AM with FTH of 5.6 km at 2600 rpm, another a DB 605 ASM again with a FTH of 7.8 km at 2600 rpm. But at least one G-10 has the same DB 605 D as in the K-4 I think, so this could serve as a substitute for the B4 powered 1.8 ata DB 605 D powered K-4. In addition, there was also a 1.98 ata version of the K-4 that ran on C3 fuel, and IIRC then these were designated DB 605DB and DB 605 DC respectively to distinguish them. And to complicate things even further, some of these engines could be operated at 2800 rpm as well for short periods of time.

 

[Holtzauge]

I think that its a bit strong for any one of us today, to say that very experienced pilots of days gone by were not familiar with the aircraft and didn't fly it properly. Clearly a British pilot wouldn't be as familiar as a German pilot or the other way around. But any pilot who is an experienced test pilot would be able to carry out the tests and fly the aircraft well. We are not talking about average squadron pilots.
Back to the topic. No one would deny that the aircraft will fly with the best potential with the slots deployed, the problem was that the slots deployed automatically and it was common for one to deploy before the other, that was the problem. As mentioned this was worked on and my understanding was that this became more controlled as the the aircraft was developed in later versions.

This behaviour was mentioned in the pilots flying the Me109E, and later by Eric Brown who I believe was flying an Me109G-6, then it was common over a long period of time. The RAF had experience of slots and the units responsible for testing captured aircraft had ground crews experienced in the care and maintenance of foreign aircraft.
Also as you would expect the RAF captured a number of Me109's and its a fair assumption that they are going to use the best of them for testing.

Maybe the wording came across as a bit to strong, but if the pilot who flew the tests did not fly with the slats out, he was only extracting a lift coefficient which was around 0.8, while the aircraft with slats out can reach 1.4. So any comparisons done under such conditions would be invalid, irrespective if the pilot was British or German.

And the latter is not so strange as it may sound, because even the German ace Johannes Steinhoff lamented that some German Bf 109 pilots thought they were doing really tight turn even though the slats had not come out.

And then, as I write in my book, we have Erwin Leykauf who claimed he never had any problems out-turning Spitfires, which was also probably true, since even the British wrote that some pilots were out-turned simply because they were afraid to take their aircraft to their limits.

But all this just goes to show how important the pilot is. However, if we are to compare the aircraft designs as such, we need to do so assuming that the pilots who fly them, fly them to their full potential. If not, then any test result will be null and void.

Finally, if the slats on the typical in-service Bf 109 deployed smoothly or snatched and came out with a bang, I have presented the data I have on this, and I have also read what you wrote, so it seems we will just have to agree to disagree on this point.

 

[Holtzauge]

Here is a clip of the Bf.109 K-4 turn test in War Thunder. I was able to approximate the 1.8 ATA setting by removing some of the "engine modifications" which remove horsepower. However in this configuration the engine has a takeoff horsepower rating of 1713hp when the real engine should be around 1775hp. In-game the 1.98 ATA setting has takeoff rating of 1947hp.

It would be possible to repeat this test with engine setup to produce 1772hp in game. The power difference is around 3% difference and I don't think that re-doing it 10 times will produce radically different results. Completing the test itself is rather annoying because having to hit multiple test points in one turn without losing altitude perfectly is difficult; this is why StatShark basically exists for this game.


View: https://youtu.be/F7Uf9zr9b_I

All of the data should be readily visible in the center of the screen. I used the heading setting to index how far into the turn I was. I got a turn time of right around 22.25 seconds which lines up pretty closely with the Messerschmitt chart time of 23 seconds. I am using 23 seconds because in their chart the turn is established at 1 second whereas in my test it is established at 0 seconds. I have also applied the same correction to your chart as well for an apples-to-apples comparison.


This is the chart that I made based on the speeds in the MTT chart vs what I was seeing in WT.
View attachment 886567

There are a few factors that affect the WT comparions.
1. It is impossible to hold perfect altitude and perfect 5.0g schedule followed by perfect 15.0 AoA while using a flight-stick. I could repeat this test 20 times and the results will have a range of results.
2. Due to the fact that it is a 360 degree turn I think minor differences from test to test will equalize out; i.e pulling too hard at start will bleed energy and be slightly offset in end of turn.
3. The horsepower setting of the aircraft could be improved by 3% and would narrow the margins seen at the end of the test. Increased horsepower will also decrease the turn time as well.
4. My recorded data might be slightly skewed because I didn't do a frame-by-frame analysis. My data is based on taking the kph data and dividing by 3.6 to get to meters per second.

Here are my observed results.
1. The War Thunder flight model is in the ballpark. The turn time is 22.25 seconds vs 23 seconds in the calculation. At 23 seconds the plane has turned 375 degrees in the video game vs 360 degrees according to the calculation. This is around 4% better than it should be. That 4% margin only starts to develop once the aircraft gets to lower speed.
2. The energy retained by the end of the turn is 4% less than it should be. Part of this can be explained away with the missing 60hp. However mathematically speaking this relationship isn't linear so 3% more horsepower is not going to materialize as 3% more speed at the end of the turn; probably more in the order of 1.5%

Very interesting results S Squish , so thanks for taking the time to do these tests. To begin with, I agree that one test was enough given that you managed to fly it so well. The reason I asked for an average, was that I've previously seen in-game testing that varied quite a lot in-between tests.

In summary, it looks like War Thunder has done a remarkably good job here given how close these numbers are. And I think this is within the acceptable margin of error, given that both mine and the German WW2 data are based on calculations, so anything below 5% must be said to be acceptable.

However, this comes with the caveat the same type of deviations (4% optimistic for turn angle, 4% optimistic for turn time, and 4% pessimistic for speed retention) are replicated across the board for other aircraft as well in War thunder. For example, the P-51D. Because then you retain the relative performance relationships between the aircraft, thus making them interesting (and realistic) to fly against each other. And not like you see in the attached figure below, where the deviations are not consistent.

But based on the data we have so far, this again makes me question the low status War Thunder seems to have in the flight sim community. Especially given that flight simulations that are credited as being more realistic, such as Il-2 and DCS, not only have very wobbly and oscillating flight models, but also sometimes produce some strange numbers when you test them. And as an example, here is a compilation of how the sustained turn performance for the Bf 109 F4 and G2 has been modeled in relation to the Yak-1 and LaGG-3 in Il-2 Sturmovik.

As you can see, there is a trend in how the aircraft are modeled in Il-2. And I think the data really speaks for itself. There is an elephant in the room. Granted, these tests were done in 2017, so I can't vouch for how well they reflect the current situation, but I can't say that I remember that this feedback to the developers was acted upon at the time.

Then about the numbers as such: I know I said earlier on that anything within 5% is acceptable. But this does not mean that it's acceptable if one aircraft is 5% above and another is 5% below. What I mean by that is that any calculation method that consistently gives results within 5% is acceptable. So for the Il-2 results below, what would have been acceptable was if the results had been consistently translated either 5% higher or lower, thus showing that the modeling was consistent. As it is, it's not.

But now, given we got such a good result from this instantaneous turn trial in War Thunder, would it be possible to also test (or are the StatShark numbers reliable enough?) the Bf 109 E-4's and Spitfire Mk I's sustained turn performance without flaps as present in the video in the OP about 30 s into the video?

In addition, testing the P-51 D's instantaneous turn under the same conditions as the Bf 109 K-4 would be interesting as well. And if you do a test then tell me at which weight and engine boost it was done and I'll test it in my simulation as well. I have the Packard Merlin V1650-7 modeled with both 67 and 75" boost, so either will do.