Could the Bf 109 E really out-turn the Spitfire Mk I? (5 Viewers)

[Holtzauge]

I posted a video about this in the Forum's video section here.

So my conclusion was that it actually could under certain circumstances.

Frankly, I was quite surprised by the result myself, since I've always lived with the conviction that the Bf 109 had no chance at all against a Spitfire in a turn fight.

Granted, the example in the video is only valid for lower altitudes, so the question is what happens at higher altitudes?

And if the Spitfire is instead powered by 100 octane fuel?

Does that change the equation?

Could the Bf 109 still stay competitive by dropping even more flaps than is assumed in the video?

In addition, in a turn fight it's both about turn rate and turn radius, and how do flaps and higher engine boost affect these parameters?

Would be interesting the hear what our learned forum members have to say about this.


Figure from video:

 

[drgondog]

I posted a video about this in the Forum's video section here.

So my conclusion was that it actually could under certain circumstances.

Frankly, I was quite surprised by the result myself, since I've always lived with the conviction that the Bf 109 had no chance at all against a Spitfire in a turn fight.

Granted, the example in the video is only valid for lower altitudes, so the question is what happens at higher altitudes?

And if the Spitfire is instead powered by 100 octane fuel?

Does that change the equation?

Could the Bf 109 still stay competitive by dropping even more flaps than is assumed in the video?

In addition, in a turn fight it's both about turn rate and turn radius, and how do flaps and higher engine boost affect these parameters?

Would be interesting the hear what our learned forum members have to say about this.


Figure from video:

View attachment 884923

For greater context and clarity, a similar set of plots should cross plot sustained altitude capability for deployed flaps. I suspect without proof that the drag of the Bf 109 is much higher in the turn with both flaps and slats deployed forcing the pilot to drop nose sooner in the turn to avoid loss of lift in the high wing. In fact. at lower speeds both ships should be in a corkscrew turn profile.

 

[Holtzauge]

For greater context and clarity, a similar set of plots should cross plot sustained altitude capability for deployed flaps. I suspect without proof that the drag of the Bf 109 is much higher in the turn with both flaps and slats deployed forcing the pilot to drop nose sooner in the turn to avoid loss of lift in the high wing. In fact. at lower speeds both ships should be in a corkscrew turn profile.

Well as I say in the video, the simulation model and how it has been verified and validated will be covered in greater detail in the longer 40 minute video I'm working on.

I gather you don't think that the Bf 109 E should be able to turn inside the Spitfire Mk I with flaps while maintaining altitude? Perhaps you could expand on that and provide some references or calculations?

Because "I suspect without proof" does not give us much to work on does it?

Also, you mention the Bf 109's slats: How much drag in % of the total do you think were the slats contribution in a tight turn?

 

[Dimlee]

Since Helmut Lipfert was mentioned in the comments to the video, I remember one episode of him turn-fighting against an Il-2 at tree top level. I think it can be found in the English edition of Lipfert's "War Diary". He was confused by the unexpected agility of the opponent and had to extend the flaps in order to avoid being outturned (by Il-2!). Both lost speed and altitude and Il-2 was the first to stall and hit the ground. Its pilot survived.
Post-war historians identified that "turn-fighter" Il-2 as a specially lightened one-seater's field mod. Some armor plates and rocket rails removed, bomb bays sealed, fuel restricted, etc. Allegedly, its 360-degree turn time was reduced below 20 seconds.

 

[Holtzauge]

Since Helmut Lipfert was mentioned in the comments to the video, I remember one episode of him turn-fighting against an Il-2 at tree top level. I think it can be found in the English edition of Lipfert's "War Diary". He was confused by the unexpected agility of the opponent and had to extend the flaps in order to avoid being outturned (by Il-2!). Both lost speed and altitude and Il-2 was the first to stall and hit the ground. Its pilot survived.
Post-war historians identified that "turn-fighter" Il-2 as a specially lightened one-seater's field mod. Some armor plates and rocket rails removed, bomb bays sealed, fuel restricted, etc. Allegedly, its 360-degree turn time was reduced below 20 seconds.

Yes, Lipfert seems to have been an exception: Because in contrast to other German aces, he seems to have scored many of his victories not in dive and zoom attacks, but in turn fights.

However, as I recall his memoirs, he almost always did this from an "unfair" position in that he usually had his wingman or other German fighters above him ready to intervene if he got into really deep problems. So while it looks like he was willing to commit to turn fights, he seems mostly to have done so from a position of strength. In addition to the Sturmovik example you mention, I have another one in my book when he shot down a La-7 in 1944 and when both Lipfert and the Soviet pilot rode the edge of stall at an altitude of 40 m according to Lipfert. But I don't recall that he dropped his flaps in that fight.

However, I seem to have missed that Lipfert used flaps when he shot down that Sturmovik you mentioned. The only good examples I had so far of flaps used in combat was Marseille in North Africa and also the USAAF ace John Godfrey who used them on his P-51B in an inconclusive dogfight with a Fw 190 D-9.

 

[GregP]

Well as I say in the video, the simulation model and how it has been verified and validated will be covered in greater detail in the longer 40 minute video I'm working on.

I gather you don't think that the Bf 109 E should be able to turn inside the Spitfire Mk I with flaps while maintaining altitude? Perhaps you could expand on that and provide some references or calculations?

Because "I suspect without proof" does not give us much to work on does it?

Also, you mention the Bf 109's slats: How much drag in % of the total do you think were the slats contribution in a tight turn?

The slats only come out when the airflow separates and pulls then open, usually but not always at lower speeds. When they do, the slatted portion of the wing (about 1/3 of the total span) instaltly has a greater drag and also a greater coefficient of lift. With the greater CL, there is more induced drag. With the slat profile, there is more form drag. Altogether, slat deployment will mean the Bf109E-4 will start slowing down more rapidly than when just before the instant the slats deploy. That does not bode well for maintaing speed in a hard turn.

Since the Bf 109 was developped for the lower to medium speed regime, it follows that the wings were intended for that speed range. In fact, the Bf 109E models are VERY good at 180 - 280 mph. Once they get faster than that, they are much less optimum. The Spitfire, though was optimized for a turning fight.

At normal fighter weight (5,844 lbs), the Spitfire I has a wing loading of 24.2 pouns per square foot. Wing area is 242 sq ft. This speaks well for hard turning.
At normal fighter weight (5,519 lbs), the Bf 109E-3 has a wing loading of 31.7 pounds per square foot. Wing area is 174.1 sq ft.

So, the Bf 109E-3 is 5.5% lighter, but has 28% less wing area. The Spitfire's wing loading is some 23.7% lower than the Bf 109E-3. The slats will keep the airflow attached to the ailerons for good roll control around the stall for the Bf 109 E-3. Even with the lift coefficient aiprovement due to slat deployment, I have some difficulty believing the charts.

To me in comparison flights, it is far more likely that, in the heat of an intial dogfight breakaway from formation flight, one pilot or the other has more experience in his airplane and can pull closer to stall or structural limit than the other one can. In comparison flights, even if the pilots are quite familiar with, say, the Spitfire ... assuming a British comparison flight with a captured Bf 109E-3, they will almost certianly NOT be quite familiar with the "enemy mount". That means they will not be using optimum techniques when flying the "other" airplane. The resulting comparison, while valid for thet test flight, is not indicative of how things might go when trained pilots, familiar with their airplanes, perform when they engage one another for real.

I think they were close to one another, and for sure traded the title of "best" back and forth for most of the war. But The Bf 109E generally out-turn the Spitfire I? I think not. Of course, MOST of the dogfights happened at speeds higher than 180 - 240 mph. Most happened around 280 - 320 mph since both airplanes were accelerating for all they were worth once the enemy was sighted. The only one NOT accelerating was the guy getting ambushed.

 

[BiffF15]

The slats only come out when the airflow separates and pulls then open, usually but not always at lower speeds. When they do, the slatted portion of the wing (about 1/3 of the total span) instaltly has a greater drag and also a greater coefficient of lift. With the greater CL, there is more induced drag. With the slat profile, there is more form drag. Altogether, slat deployment will mean the Bf109E-4 will start slowing down more rapidly than when just before the instant the slats deploy. That does not bode well for maintaing speed in a hard turn.

Since the Bf 109 was developped for the lower to medium speed regime, it follows that the wings were intended for that speed range. In fact, the Bf 109E models are VERY good at 180 - 280 mph. Once they get faster than that, they are much less optimum. The Spitfire, though was optimized for a turning fight.

At normal fighter weight (5,844 lbs), the Spitfire I has a wing loading of 24.2 pouns per square foot. Wing area is 242 sq ft. This speaks well for hard turning.
At normal fighter weight (5,519 lbs), the Bf 109E-3 has a wing loading of 31.7 pounds per square foot. Wing area is 174.1 sq ft.

So, the Bf 109E-3 is 5.5% lighter, but has 28% less wing area. The Spitfire's wing loading is some 23.7% lower than the Bf 109E-3. The slats will keep the airflow attached to the ailerons for good roll control around the stall for the Bf 109 E-3. Even with the lift coefficient aiprovement due to slat deployment, I have some difficulty believing the charts.

To me in comparison flights, it is far more likely that, in the heat of an intial dogfight breakaway from formation flight, one pilot or the other has more experience in his airplane and can pull closer to stall or structural limit than the other one can. In comparison flights, even if the pilots are quite familiar with, say, the Spitfire ... assuming a British comparison flight with a captured Bf 109E-3, they will almost certianly NOT be quite familiar with the "enemy mount". That means they will not be using optimum techniques when flying the "other" airplane. The resulting comparison, while valid for thet test flight, is not indicative of how things might go when trained pilots, familiar with their airplanes, perform when they engage one another for real.

I think they were close to one another, and for sure traded the title of "best" back and forth for most of the war. But The Bf 109E generally out-turn the Spitfire I? I think not. Of course, MOST of the dogfights happened at speeds higher than 180 - 240 mph. Most happened around 280 - 320 mph since both airplanes were accelerating for all they were worth once the enemy was sighted. The only one NOT accelerating was the guy getting ambushed.

Greg,

A couple of questions. First, how do the slats on the Bf109 keep the airflow attached to the ailerons? Second, does your normal fighter weight for the Bf109 have him at half fuel weight (normal fuel quantity for having crossed the channel? Third, do the ailerons droop on the 109 with flap extension (or any WW2 aircraft)?

While I can't say how guys did it in WW2, but when I dropped the flaps on the Eagle I released some back pressure to counter the drag increase. I only used flaps when slow at the floor and I needed about 15-20 degrees more nose rotation to bring the gun to bear. If I misjudged I would hold airspeed (by not pulling too hard), misalign turn circles, and attempt another shot if fuel permitted.

 

[SaparotRob]

Greg,

A couple of questions. First, how do the slats on the Bf109 keep the airflow attached to the ailerons? Second, does your normal fighter weight for the Bf109 have him at half fuel weight (normal fuel quantity for having crossed the channel? Third, do the ailerons droop on the 109 with flap extension (or any WW2 aircraft)?

While I can't say how guys did it in WW2, but when I dropped the flaps on the Eagle I released some back pressure to counter the drag increase. I only used flaps when slow at the floor and I needed about 15-20 degrees more nose rotation to bring the gun to bear. If I misjudged I would hold airspeed (by not pulling too hard), misalign turn circles, and attempt another shot if fuel permitted.

I love that kind of talk.

 

[andy1967]

I posted a video about this in the Forum's video section here.

So my conclusion was that it actually could under certain circumstances.

Frankly, I was quite surprised by the result myself, since I've always lived with the conviction that the Bf 109 had no chance at all against a Spitfire in a turn fight.

Granted, the example in the video is only valid for lower altitudes, so the question is what happens at higher altitudes?

And if the Spitfire is instead powered by 100 octane fuel?

Does that change the equation?

Could the Bf 109 still stay competitive by dropping even more flaps than is assumed in the video?

In addition, in a turn fight it's both about turn rate and turn radius, and how do flaps and higher engine boost affect these parameters?

Would be interesting the hear what our learned forum members have to say about this.


Figure from video:

View attachment 884923

Interesting video i look forward to watching the longer more indepth video. Christoph Bergs on his Military Aviation History covers this topic.His conclusion is generally a Spitfire will out turn a 109E but an experienced 109E pilot could and did out turn an average Spitfire pilot.

 

[drgondog]

Yes, Lipfert seems to have been an exception: Because in contrast to other German aces, he seems to have scored many of his victories not in dive and zoom attacks, but in turn fights.

However, as I recall his memoirs, he almost always did this from an "unfair" position in that he usually had his wingman or other German fighters above him ready to intervene if he got into really deep problems. So while it looks like he was willing to commit to turn fights, he seems mostly to have done so from a position of strength. In addition to the Sturmovik example you mention, I have another one in my book when he shot down a La-7 in 1944 and when both Lipfert and the Soviet pilot rode the edge of stall at an altitude of 40 m according to Lipfert. But I don't recall that he dropped his flaps in that fight.

However, I seem to have missed that Lipfert used flaps when he shot down that Sturmovik you mentioned. The only good examples I had so far of flaps used in combat was Marseille in North Africa and also the USAAF ace John Godfrey who used them on his P-51B in an inconclusive dogfight with a Fw 190 D-9.

I don't know where the source of Godfrey vs Fw 190D-9 originated but the D-9 story is impossible. Godfrey was shot down by his own wingman on 8-24-44 while strafing an airfield ne of Nordhausen. The D-9s weren't operational until December. I suspect a mis-identification by Godfrey as several ETO pilots named a 'long nose Fw' in Match 1944 encounter reports.

I know of several ETO aces, including my father, that did not out-turn, nor lose ground against a Bf 109 when both using flaps to tighten their turns. Plus several that 'did'. Suspect the latter was a pilot skill difference factor. A light P-51B (eg when returning from a distant target and internal fuel drawn down after dropping external tanks) should out turn a Bf 109 at high altitude every time and also in the altitudes where low blower is peaking and the Power Available over Drag is optimal

 

[Holtzauge]

Some input to the points that have been brought up so far concerning slats, the Spitfire, and pilot skills:

The slats on the Bf 109 are controlled by suction forces at the leading edge, and not by the airspeed as such, but by the angle of attack. So this means that they do not only come out at lower airspeeds, but also at higher speeds when the pilot pulls g's and thereby increases the angle of attack. And this angles the resulting lift vector forwards, thus pulling them out.

The way they maintain aileron control at higher angles of attack is by ensuring that the airflow stays attached to the wing's upper surface by injecting energy into the upper wing's boundary layer which without this would detach and thus leave the aileron behind it to work in "dead" air and therefore lose effectivity. So what the slats really do is to move the point at which the wing stalls to a higher angle of attack, and thus making the ailerons work in an environment much as they did at lower angles of attack.

The Spitfire was never designed with turn performance in mind: The Spitfire's main design requirements were connected to climb and speed. However, the specification also contained a requirement for landing speed. And it was this that drove the size of the Spitfire's wing, not that it should provide good turn performance. This was just a "side effect" of the landing speed requirement.

Then the point about pilot skills: Yes, of course this is important: And in the longer video, I have quotes both from German and British pilots who flew the Bf 109, and show that some German pilots thought they were doing really tight turns even without the slats not having come out. Which as the German ace Johannes Steinhoff points out they were obviously not doing. In addition, there is an RAE evaluation of the Bf 109 in which the British test pilot claimed that the Bf 109 turned best at the point when the slats were just about to come out, thus basically invalidating these tests.

Finally, what the video shows is what the aircraft as such were capable off, and it does not suggest that the Bf 109 should turn fight with the Spitfire. The video only shows that it was possible to do that at lower altitudes if the pilot chose to do so.

In the longer video, I have a quote by John Godfrey who used flaps in a turn fight with a Fw 109 D-9. Does this mean that the P-51B should try to engage Bf 109's in turn fights using flaps? Of course not. I'm sure Godfrey as a rule flew the Mustang to its strengths. But got himself into a fix with this particular Fw 190, and was probably quite glad that combat flaps was a part of the P-51 pilot's toolbox at this particular time.

So in summary, just because a Bf 109 CAN outturn a Spitfire by using flaps does not necessarily mean that it as a rule SHOULD. But as the Godfrey example shows, if your flaps ARE usable for turning, you may encounter situations when you are glad that they can.

 

[Holtzauge]

I don't know where the source of Godfrey vs Fw 190D-9 originated but the D-9 story is impossible. Godfrey was shot down by his own wingman on 8-24-44 while strafing an airfield ne of Nordhausen. The D-9s weren't operational until December. I suspect a mis-identification by Godfrey as several ETO pilots named a 'long nose Fw' in Match 1944 encounter reports.

I know of several ETO aces, including my father, that did not out-turn, nor lose ground against a Bf 109 when both using flaps to tighten their turns. Plus several that 'did'. Suspect the latter was a pilot skill difference factor. A light P-51B (eg when returning from a distant target and internal fuel drawn down after dropping external tanks) should out turn a Bf 109 at high altitude every time and also in the altitudes where low blower is peaking and the Power Available over Drag is optimal

Well, Godfrey may have misidentified his opponent, but he describes it not as a Bf 109, but as one of the new improved long-nosed Fw 190s in Robert L Shaw's Fighter Combat Tactics and Maneuvering. And here is the quote in which using combat flaps is mentioned:

"Around and around we went. Sometimes the FW got in close, and other times, when I'd dropped my flap to tighten my turn, I was in a position to fire; but the German, sensing my superior position kept down in his turn, gaining speed and quickly pulling up, and with the advantage of height he would then pour down on my tail."

But for me the big takeaway here is not the type of German fighter he fought, but that he actually used flaps in this encounter, thus showing that it was actually done sometimes.

And yes, I agree about the fuel status: How much fuel the P-51 had was of course a major factor in these fights. And from a technical standpoint, I think it is more fair to compare aircraft with a fuel status for equal endurance, and not penalize an aircraft like the Mustang for having larger fuel tanks , and compare them with 100% internal fuel like people sometimes do.

 

[drgondog]

Well as I say in the video, the simulation model and how it has been verified and validated will be covered in greater detail in the longer 40 minute video I'm working on.

I gather you don't think that the Bf 109 E should be able to turn inside the Spitfire Mk I with flaps while maintaining altitude? Perhaps you could expand on that and provide some references or calculations?

Because "I suspect without proof" does not give us much to work on does it?

Also, you mention the Bf 109's slats: How much drag in % of the total do you think were the slats contribution in a tight turn?

As you implied, I don't have the hard data on either one to state my 'suspicion' as fact.

Couple of points.
Wing loading favored the Spitfire.
You would have to go deeply into the CL profile as a function of angle of attack to conclusively derive 'estimates' of turn radius for both the 109 conditions of deployed slats, and deployed flaps.
I don't know where the parasite drag increases could be found for both of those conditions, but the delta between HP available over Drag must be calculated for both ships and I 'suspect' (that word again) that the ability of the 109 to maintain constant altitude degrades far more rapidly than the Spit.
The question of wing Oswald efficiency comparisons between the two wings suggest that the Spit has lower Induced drag for the same relative CL

Couple of questions for the modeler.
In asymmetric flight with slats deployed for the 109 the 'high' wing will presumably have more lift and drag and rudder should be introduced to bring the nose on track. Is trim drag significant? How does the modeler test for this? The Spit also begs the same question but i'm inclined to believe less severe.
At lower speeds propeller efficiency becomes a question to be tested for Thrust HP calculations at all relevant speeds and altitudes. Data available?
Per the point (assumption) above, where does the comparative Parasite drag as a function CL enter the model assumptions? Parasite drag (CD vs CL) is a steep curve as speeds decline, as does Induced drag. Are those data available for the Spit and Bf 109 wings?

At the end of the day, I believe the VVS had the right approach in their testing - but their methods still beg the question of whether analytics were ever a factor to Predict the performance and compare against the actual 'time to 360 degree turn'.

Thus concludes the points underlying my opinions, and represent only the infamous and often derided 'gut feel'. The opinion is not intended as a challenge to your POV,

 

[z42]

And from a technical standpoint, I think it is more fair to compare aircraft with a fuel status for equal endurance, and not penalize an aircraft like the Mustang for having larger fuel tanks , and compare them with 100% internal fuel like people sometimes do.

Good point that 100% internal fuel is probably not a good base for comparison, but, shouldn't one rather compare realistic fuel loads in a likely combat scenario? In such a scenario, over Germany, the P-51 would be disadvantaged by needing sufficient fuel to get back to England (or at least some emergency strip in France come summer '44 or later?) whereas the Bf-109 would need considerably less fuel for its return journey?

 

[drgondog]

Good point that 100% internal fuel is probably not a good base for comparison, but, shouldn't one rather compare realistic fuel loads in a likely combat scenario? In such a scenario, over Germany, the P-51 would be disadvantaged by needing sufficient fuel to get back to England (or at least some emergency strip in France come summer '44 or later?) whereas the Bf-109 would need considerably less fuel for its return journey?

that is a correct point but there even two scenarios here. One is that inbound only 50-60 gallons of 269 gallons internal fuel in the Mustang when engine is started. that includes left main through formation assembly and internal fuselage tank before switching to externals. That means inbound combat has reduced gross weight of the clean P-51B by say 360 pounds. If engagement is on the way home drop tanks have been consumed and the Mustang is back to using internal fuel. So combat on the way home occurs after more weight is lost.

The point to be made is that the Mustang uses 50% of a Bf 109 total capacity just climbing to bomber altitude.

 

[Holtzauge]

As you implied, I don't have the hard data on either one to state my 'suspicion' as fact.

Couple of points.
Wing loading favored the Spitfire.
You would have to go deeply into the CL profile as a function of angle of attack to conclusively derive 'estimates' of turn radius for both the 109 conditions of deployed slats, and deployed flaps.
I don't know where the parasite drag increases could be found for both of those conditions, but the delta between HP available over Drag must be calculated for both ships and I 'suspect' (that word again) that the ability of the 109 to maintain constant altitude degrades far more rapidly than the Spit.
The question of wing Oswald efficiency comparisons between the two wings suggest that the Spit has lower Induced drag for the same relative CL

Couple of questions for the modeler.
In asymmetric flight with slats deployed for the 109 the 'high' wing will presumably have more lift and drag and rudder should be introduced to bring the nose on track. Is trim drag significant? How does the modeler test for this? The Spit also begs the same question but i'm inclined to believe less severe.
At lower speeds propeller efficiency becomes a question to be tested for Thrust HP calculations at all relevant speeds and altitudes. Data available?
Per the point (assumption) above, where does the comparative Parasite drag as a function CL enter the model assumptions? Parasite drag (CD vs CL) is a steep curve as speeds decline, as does Induced drag. Are those data available for the Spit and Bf 109 wings?

At the end of the day, I believe the VVS had the right approach in their testing - but their methods still beg the question of whether analytics were ever a factor to Predict the performance and compare against the actual 'time to 360 degree turn'.

Thus concludes the points underlying my opinions, and represent only the infamous and often derided 'gut feel'. The opinion is not intended as a challenge to your POV,

Wing loading is absolutely an important factor: But for induced drag (and by extension turn performance), the big determinant is actually the span loading, as in the weight divided by the wing span. This is why for example the Ta 152 H was quite good in turns, even though it had quite a high wing loading.

Then when it comes to drag, the drag of the slats is something that is often quite misunderstood: Sure, it looks horrible with those things sticking out, and many make the mistake that this then must mean that they cause a lot of drag. And sure, on wing profile level they do. But this actually drowns in the massive induced drag the huge vortices shed from the wingtips cause.

And added to that, when the flaps are out, you get another couple of huge vortices at the middle wing stations where the flaps end, thus making the slats drag contribution even smaller. And this (the induced drag) absolutely dominates, so the drag contribution of the slats are just a few percent of the total in a tight turn close to stall. In fact, I write quite a lot about this in my book, and also calculate a percentage range, which the interested reader can find described there in my book in more detail.

And yes, the simulation model I use takes the degrading Oswald factor into account, as this is as you say needed to get reliable results. Since assuming this constant between aircraft (I model this different) and at higher Cl will not yield reliable results. Same goes for propeller efficiency: This has to vary with blade angle, speed and tip Mach number even for a constant speed propeller. And yes, as speed declines angle of attack changes, and Cl and Cd is continuously recalculated in an instantaneous turn. In addition my model separates the thrust vector from the speed vector, so I capture those effects as well.

Then about the Spitfire's and Bf 109's ability to maintain altitude while still having the flaps out: During WW2, the famous British aerodynamicist M B Morgan published a report (RM 2349) on the Spitfire's turn capabilities as affected by flaps: And it turns out that even with split flaps dropped in the landing position at 85 deg down, this even so improved the turn performance (even while maintaining altitude) as high as 12,000 ft and above! So the power to overcome the added drag from flaps was there. In addition, in the report Morgan has a theoretical example of the improvement with the Spitfire's flaps set at 30 deg (As we know IRL it could only do 0 or 85 deg flap): And that lowered the turn radius to about 80% of that without flaps, so quite comparable to my simulation in which I get 79% (See doghouse chart about 6 min into the video) for the Bf 109.

So in conclusion, I think both my simulations, and RAE RM 2349 show that flaps do indeed improve turn performance. And given that the Bf 109 could crank out its flaps gradually as the speed wound down, this was a nice "tool" to have if you needed it.

A bit like the 4-wheel drive on your SUV: You probably seldom need it, but when you do, you're glad it's there.

 

[Holtzauge]

Good point that 100% internal fuel is probably not a good base for comparison, but, shouldn't one rather compare realistic fuel loads in a likely combat scenario? In such a scenario, over Germany, the P-51 would be disadvantaged by needing sufficient fuel to get back to England (or at least some emergency strip in France come summer '44 or later?) whereas the Bf-109 would need considerably less fuel for its return journey?

that is a correct point but there even two scenarios here. One is that inbound only 50-60 gallons of 269 gallons internal fuel in the Mustang when engine is started. that includes left main through formation assembly and internal fuselage tank before switching to externals. That means inbound combat has reduced gross weight of the clean P-51B by say 360 pounds. If engagement is on the way home drop tanks have been consumed and the Mustang is back to using internal fuel. So combat on the way home occurs after more weight is lost.

The point to be made is that the Mustang uses 50% of a Bf 109 total capacity just climbing to bomber altitude.

I agree with both your points here, but this really brings us into a tactical analysis, since one could then also argue that while the Mustang probably had more fuel to lug around when it encountered a Bf 109, the Germans were outnumbered, and had to climb up to meet the escorting Mustangs.

And given the choice between being loaded with less fuel, lower and outnumbered, or being loaded with more fuel, higher and in greater numbers, I think most would have opted for the latter.

But again, from a design perspective, a Bf 109 with tanks topped off had only 400 l, and a P-51 with only that amount of fuel in its tanks would give German fighters a very hard time indeed.

 

[Engineman]

So in conclusion, I think both my simulations, and RAE RM 2349 show that flaps do indeed improve turn performance. And given that the Bf 109 could crank out its flaps gradually as the speed wound down, this was a nice "tool" to have if you needed it.

A bit like the 4-wheel drive on your SUV: You probably seldom need it, but when you do, you're glad it's there.

In a turning fight , you are likely to need all the turning performance you can get, if you want to live! A turning fight is often judged by the amount of "angle" off the enemy aircraft. If you start with both on opposite sides of the turning circle you are equal on angles, both 180 off. If you find the enemy is starting to get closer to your six-o'clock, he is making angles on you and you must do something like tighten your turning or use a manoeuvre that achieves angles against your enemy, who is going to kill you soon.
If, after starting with 180 off, you gain angles against your enemy and start to get closer to his 6-o'clock, you are winning and may soon get a shot at him.
In both situations, there is no room for complacency and not using your maximum performance in a turning combat. That doesn't mean you need flap from the start, because at high speed you are probably G limited, however as the indicated airspeed reduces, G reduces and Alpha increases, there will be a need for better lift performance and that was where the 109 pilot had the advantage with automatic manoeuvre slats and manual flap within the high lift-low drag range of movement of the flaps.

Eng

 

[Engineman]

I agree with both your points here, but this really brings us into a tactical analysis, since one could then also argue that while the Mustang probably had more fuel to lug around when it encountered a Bf 109, the Germans were outnumbered, and had to climb up to meet the escorting Mustangs.

And given the choice between being loaded with less fuel, lower and outnumbered, or being loaded with more fuel, higher and in greater numbers, I think most would have opted for the latter.

But again, from a design perspective, a Bf 109 with tanks topped off had only 400 l, and a P-51 with only that amount of fuel in its tanks would give German fighters a very hard time indeed.

Bf 109 and escorting Mustang engagements of Germany were fairly well defined. The defending Bf 109 fighters could be launched to intercept the raid with a good choice of altitude and position, T/O fuel would probably be 400L internal with 300L drop tank. Initial Combat would see the drop tanks released leaving 400L. The P-51 fuel state would be according to the time that they were engaged, again dropping tanks on contact.
German Bomber killer fighters may have operated similar to the fighter escort killers.
I suspect that the German aircraft would always try to operate with drop tanks, because the raid may divert and the fighters might need to travel a long way.
Also worth remembering that the escort fighters had only visual means to locate their attackers. I do not know if allied listening EW was effective in warning the raid about German fighter defence activity in real-time?

Eng

 

[Holtzauge]

In a turning fight , you are likely to need all the turning performance you can get, if you want to live! A turning fight is often judged by the amount of "angle" off the enemy aircraft. If you start with both on opposite sides of the turning circle you are equal on angles, both 180 off. If you find the enemy is starting to get closer to your six-o'clock, he is making angles on you and you must do something like tighten your turning or use a manoeuvre that achieves angles against your enemy, who is going to kill you soon.
If, after starting with 180 off, you gain angles against your enemy and start to get closer to his 6-o'clock, you are winning and may soon get a shot at him.
In both situations, there is no room for complacency and not using your maximum performance in a turning combat. That doesn't mean you need flap from the start, because at high speed you are probably G limited, however as the indicated airspeed reduces, G reduces and Alpha increases, there will be a need for better lift performance and that was where the 109 pilot had the advantage with automatic manoeuvre slats and manual flap within the high lift-low drag range of movement of the flaps.

Eng

I agree completely: Once you are committed to a turn fight you need all the advantages you can get. OTOH I can also sympathize with the objections I usually get when I mention that the Bf 109 had this item in the "toolbox", which is usually that this would not be the "right" way to fly a Bf 109 to its strengths. Because common wisdom holds (and rightly so I suppose) that the Bf 109 should be used in slashing attacks, and not "mix it up" with Spitfires and Hurricanes in turn fights. But as you say, once you ARE in a turn fight, anything that helps you is positive, and this is where the Bf 109 flaps come in handy IMHO: Because while probably not the first item you would reach for, it's still there, ready to be picked up if you ever need it.

Bf 109 and escorting Mustang engagements of Germany were fairly well defined. The defending Bf 109 fighters could be launched to intercept the raid with a good choice of altitude and position, T/O fuel would probably be 400L internal with 300L drop tank. Initial Combat would see the drop tanks released leaving 400L. The P-51 fuel state would be according to the time that they were engaged, again dropping tanks on contact.
German Bomber killer fighters may have operated similar to the fighter escort killers.
I suspect that the German aircraft would always try to operate with drop tanks, because the raid may divert and the fighters might need to travel a long way.
Also worth remembering that the escort fighters had only visual means to locate their attackers. I do not know if allied listening EW was effective in warning the raid about German fighter defence activity in real-time?

Eng

True, the Germans did have what we today would call GCI but as I recall it, there were some pretty funny episodes connected to this since Allied Intelligence soon began to try to take over and direct the intercepting German flights in the wrong directions, with verbal battles going on on the German frequencies with both real and fake German GCI officers saying things like: " No! Listen to me! I'm the REAL controller!" The other one is a British imposter! LISTEN TO ME!" and vice versa. IIRC then the Germans tried to counter this by using female controllers, to which the Allies of course responded by using their own female German speakers to impersonate them! ECM, ECCM and ECCCM in its infancy!

Jokes aside, I recently listened to an audiobook on Spotify (The German Aces Speak, Volumes I and II) where Johannes Steinhoff lamented that towards the end of the war, they were according to him maybe 75 German fighters climbing up to meet what he called a thousand escorts. And that must have been tough: Facing well trained pilots who swooped down on you from above in great numbers. Being able to turn slightly better with flaps seems like a pretty poor substitute under those conditions!