# Why was the BF109 so slow compared with the P51?



## johnbr (Jan 3, 2019)



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## pbehn (Jan 3, 2019)

It was designed a generation or two later?

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## swampyankee (Jan 3, 2019)

johnbr said:


>



Because North American had better aerodynamicists than did the Messerschmidt company, and those NA engineers also had access to better resources. After all, look at how many Luftwaffe aircraft used NACA airfoils.

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## pbehn (Jan 3, 2019)

swampyankee said:


> Because North American had better aerodynamicists the Messerschmidt who had access to better resources. After all, look at how many Luftwaffe aircraft used NACA airfoils.


If that was the case then the P-51 would have been available at the same time as the Bf109, in service in 1939/40.


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## Crimea_River (Jan 3, 2019)

Getting my popcorn....

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## fubar57 (Jan 3, 2019)

Have some of mine...

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## GrauGeist (Jan 4, 2019)

swampyankee said:


> Because North American had better aerodynamicists than did the Messerschmidt company, and those NA engineers also had access to better resources. After all, look at how many Luftwaffe aircraft used NACA airfoils.


The Bf109 V13 set the world airspeed record in November 1937 (379mph) and the P-51 was...wait...it didn't exist at the time.


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## swampyankee (Jan 4, 2019)

pbehn said:


> If that was the case then the P-51 would have been available at the same time as the Bf109, in service in 1939/40.


Why does that follow? The USAAF’s leadership didn’t see need the P-51 in 1935 or 1936

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## swampyankee (Jan 4, 2019)

GrauGeist said:


> The Bf109 V13 set the world airspeed record in November 1937 (379mph) and the P-51 was...wait...it didn't exist at the time.



The absolute record, in 1937, was still held by a floatplane, the MC.72, which was about 100 km/hr faster than the Bf.109V13. I would hardly consider a floatplane to be a exemplar of good aerodynamics.


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## chuter (Jan 10, 2019)

swampyankee said:


> The absolute record, in 1937, was still held by a floatplane, the MC.72, which was about 100 km/hr faster than the Bf.109V13. I would hardly consider a floatplane to be a exemplar of good aerodynamics.



Well, then, my friend, you need to have another look. 

As for the P-51/109 question ... cooling drag. Like the Spitfire, the 109 never actually got Meredith to work despite trying very hard to get it to, therefore binned Meredith and assumed it must've been the wing which, frankly, it wasn't (according to Lee Atwood).


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## me109g4 (Jan 10, 2019)

I thought the BF109G-10 was faster than the p51 in some flight regimes,,,


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## tomo pauk (Jan 10, 2019)

Funnily enough, I've watched the video a week ago, as well as the 'spin-off' titled, roughly, 'Why Bf 109K was faster than Mustang'.
I'd toss in some details the author got wrong or iffy at least. Eg. his suggestion that engine's cubic capacity has a lot to do with aircraft speed, or that variable S/C drive is a contributing factor. He says that P-51 had 'some aerodynamic advantages' - nope, IMO that's downplaying it. (advantages). Then - manifold pressure is also a function of compression ratio, the tidbit does not get mentioned. Video says that 109s used 95 oct fuel - not true. 'No technology can overcome advantage in fuel grade' - nope, technology was there, called ADI, used by Germans as MW 50. 'P-51's primary advantage was fuel' - ?? 'Bf 109 does not have enough of roomfor duel S/C' - ?? 'Mustang's designers could simply gear the S/C...' - ??
All of this in 1st 7 minutes.

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## Zippythehog (Jan 10, 2019)

I believe the main answer is that the U.S. and Britain had far better fuel. The powerplants of the two A/C in question had different compression ratios. The Merlin engine specified higher octane than the DB because they could.


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## DarrenW (Jan 10, 2019)

tomo pauk said:


> Funnily enough, I've watched the video a week ago, as well as the 'spin-off' titled, roughly, 'Why Bf 109K was faster than Mustang'.
> I'd toss in some details the author got wrong or iffy at least. Eg. his suggestion that engine's cubic capacity has a lot to do with aircraft speed, or that variable S/C drive is a contributing factor. He says that P-51 had 'some aerodynamic advantages' - nope, IMO that's downplaying it. (advantages). Then - manifold pressure is also a function of compression ratio, the tidbit does not get mentioned. Video says that 109s used 95 oct fuel - not true. 'No technology can overcome advantage in fuel grade' - nope, technology was there, called ADI, used by Germans as MW 50. 'P-51's primary advantage was fuel' - ?? 'Bf 109 does not have enough of roomfor duel S/C' - ?? 'Mustang's designers could simply gear the S/C...' - ??
> All of this in 1st 7 minutes.



Wow I really need to watch that video again, and this time while paying far better attention to what's said! I actually didn't notice all those "glitches" Tomo, but knowing how you're VERY well-schooled in various aircraft technology, I don't doubt any of it one bit.....


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## DarrenW (Jan 10, 2019)

me109g4 said:


> I thought the BF109G-10 was faster than the p51 in some flight regimes,,,



Not trying to challenge you here, but do you or anyone else have any charts that show this to be true? I don't, but that doesn't mean they don't exist somewhere.


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## nuuumannn (Jan 10, 2019)

> Have some of mine...



Don't mind if I do! Munch munch...

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## cherry blossom (Jan 11, 2019)

swampyankee said:


> The absolute record, in 1937, was still held by a floatplane, the MC.72, which was about 100 km/hr faster than the Bf.109V13. I would hardly consider a floatplane to be a exemplar of good aerodynamics.


Floatplanes were able to use very long runways and could therefore have relatively small wings. I suspect that a land version of the MC.72 could have been built with a retracting undercarriage and flown from Edwards Air Force Base (then Muroc), which would have been even faster.


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## DarrenW (Jan 11, 2019)

tomo pauk said:


> Video says that 109s used 95 oct fuel - not true



Wasn't the Allied equivalent lean octane rating of C3 fuel around that number?


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## tomo pauk (Jan 11, 2019)

DarrenW said:


> Wasn't the Allied equivalent lean octane rating of C3 fuel around that number?



IIRC the Allies called the C3 as '96 oct fuel', while Germans called it '100 oct fuel'. Both values being lean rating, while rich rating going steadily up towards 140+ as war progressed. Used mostly by DB 601N and BMW 801D.

The fuel used by most Bf 109s was B4 - 87 oct.


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## nuuumannn (Jan 11, 2019)

tomo pauk said:


> The fuel used by most Bf 109s was B4 - 87 oct.



There it is...





87


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## Snowygrouch (Jan 11, 2019)

swampyankee said:


> Because North American had better aerodynamicists than did the Messerschmidt company, and those NA engineers also had access to better resources. After all, look at how many Luftwaffe aircraft used NACA airfoils.



There is no doubt the Mustangs aerodyanamics were superlative. However, it is too simple to start saying this was due to the chaps at Me just not knowing how to do it. In fact they did know perfectly well what Laminar flow wings were (although there are many other nice aero bits it has too).

A very important thing to note is that the Germans could NOT impliment Laminar flow wings because they discovered through testing that they were only effective if the fit and finish of the aircraft was absolutely spot - on. Knowing perfectly well that such a fit and finish was impossible to imagine in the manufacturing environment that existed in Germany in wartime, they didnt bother, as they actual advantage would have been negligable. A second point being that this requirement for fit and finish made it impossible to retain the
leading edge slats. Eliminating those on an existing aircraft would have been a total rework of the plane (thats not something I`ve "read" into it, thats a direct statement in the
original report as well). (Ref#1) 

There are about 20 other things one could talk about on this subject but thats one to keep in mind before assuming incompetance of the aerodyamics staff, who had actually designed one for the 109. It was never implimented. They do seem to have waited longer to try it than the USA did, but that can probably be attributed to the fact that nobody in Germany
had been seriously planning for them to even be at war after about 1942, so they really slacked off with development until it became evident that things were a bit stickier than hoped for. So this seems to have been a case of bungled direction of research from above, rather than technical inability. (Ref#2)

=============
ARCHIVAL SOURCES
=============

1) "Me.109 Laminar Profile wing" - Pieckert, TB No.128/44 - Messershmitt A.G. Windtunnel Report

2) "A Scientists Analysis of the German Defeat" - Professor Dr. Walter Georgii; being interrogated on 19th Nov 1945 (Georgii had been in charge of the glider development aerodyamics
centre in Germany through much of ww2.

Some bio info on him here:
Walter Georgii (Meteorologe) – Wikipedia

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## nuuumannn (Jan 11, 2019)

Snowygrouch said:


> So this seems to have been a case of bungled direction of research from above, rather than technical inability.



Oh yes, the downfall of the whole Third Reich, really.

Nice bio, Calum; looking forward to nabbing a copy of the book.

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## tomo pauk (Jan 13, 2019)

Zippythehog said:


> I believe the main answer is that the U.S. and Britain had far better fuel. The powerplants of the two A/C in question had different compression ratios. The Merlin engine specified higher octane than the DB because they could.



Because who could?
There was a DB engine that used hi-oct fuel, it was called DB 601N. Due to many inter-related things (one of them being, indeed, much higher compression ratio), that engine never took advantage of the C3 fuel, and barely attained 1.40 ata (around +5.25 psi). We can compare speeds of Bf 109F1 or F2, the aircraft with 601N engine, and see that they lag behind P-51A on military power (= slightly less altitude power than 601N) by some 30 mph. 



Snowygrouch said:


> There is no doubt the Mustangs aerodyanamics were superlative. However, it is too simple to start saying this was due to the chaps at Me just not knowing how to do it. In fact they did know perfectly well what Laminar flow wings were (although there are many other nice aero bits it has too).



Against already thin and small wing of Bf 109, the P-51s wing probably offers just small advantage for over-all speed; that 'transplantation' of P-51s wing would've improved other things - like usable internal volume, better U/C layout and lower wing loading (= no need for slats?) - is probably not in the scope of this thread.
All of what brings us to a part two of the answer to The Question - streamlining.
On the Bf 109E-G, there was a number of things that add the 'delta Cd', the drag increments. In no particular order:
- ram air scoop was not blended in fuselage shape
- coolant radiators will be 'struck' by turbulent air, two of them, vs. one on P-51 that went improving 4 times between P-51 and P-51H
- no cover for wheen wells
- separate oil cooler
- questionable use of Meredith effect
- fixed tailwheel on many produced examples
- HMG 'bumps' at cowling on many later Bf 109Gs
- possible imperfections at slat/wing joint
- wing bumps for wheels on late 109Gs and 109Ks

All of these, along with many more, are listed at the Hoerner's analysis of drag of the Bf 109G. He states that wing contributed to drag by more than 1/3rd, and engine-related drag being at almost 1/4th of whole drag.

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## Schweik (Jan 17, 2019)

Is there some systematic standard by which they measure drag across different aircraft types? Like a number?


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## swampyankee (Jan 18, 2019)

Schweik said:


> Is there some systematic standard by which they measure drag across different aircraft types? Like a number?




Well, at least two: zero-lift drag coefficient and lift/drag ratio.

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## gliding (Jan 18, 2019)

tomo pauk said:


> IIRC the Allies called the C3 as '96 oct fuel', while Germans called it '100 oct fuel'. Both values being lean rating, while rich rating going steadily up towards 140+ as war progressed. Used mostly by DB 601N and BMW 801D. The fuel used by most Bf 109s was B4 - 87 oct.



The comparison of fuels and their knock resistance is not possible over "the" octane number. Then and now different methods of measurement are used. 
For the comparison, one needs a test engine, which is operated with Isooctane. Depending on this test engine, there are different "octane" numbers.
_(An early German C3 fuel (95 german-octane) was roughly comparable to a 100 US-octane fuel.)_
The production of high-octane gasoline was complex and expensive and could not be realized in the required extent by Germany in the last years of the war.

Reports from Daimler show that higher performance was possible even without GM or MW50. The required fuel was not sufficiently available.


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## drgondog (Jan 18, 2019)

I will devote a lot of time in the Apendices of my new book on this very subject:

Start with Power Available vs Power Required as the fundamental set of calculations once the drag parameters are derived (wind tunnel testing);

'The Wing is The Thing' to begin the discussion.
The achievement of (Close to) net zero drag for the internal cooling system is an assumption based on the composers (Horkey and Ashkenas) of the Performance Calculations contained in NA-5534 on the P-51B-1-NA airplane - for high speed Cooling Drag. In this assumption the Pressure and internal friction Drag compared to Thrust generated by the design often referred to as the Meredith Effect is specifically stated as "0 for high speed cruising at Critical Altitude" BUT the Delta CDp for 35,000 feet = .0004 and at 40,000 feet = .0010. In other words Net Zero Internal CDp for only a region at high speed in a narrow altitude envelope.

The Delta CDp for CLIMB condition = .0064 at ALL altitudes independent of Reynold Number.

The INITIAL base CDp for RN =1.8x10^^ for the Wing = .0074 (note: the same initial value for same wing at 2.0x10^^6 for the P-51D wing =.0070). This is a value that considers the profile drag of the wing immersed in a flow - INDEPENDENT of the friction drag.

This value is far below that of the same relative thickness wings of the Fw 190/F6F/F4U/P-47/Bf 109 using NACA 230xx airfoils at same RN.

The second significant base Delta CDp values for comparison, but less than the wing in importance, are the form drag totals for Fuselage, empennage, carb duct, cockpit enclosure build ups. If you wish to ask why, consider that the entire airframe Lines were developed using Descriptive geometry for which the contour from nose through cockpit enclosure was essentially an ascending shape area of low gradient change aft of the card intake duct (including Allison).

(Note that ALL Mustang variants placed the 'disruptor' (scoop, ducting for radiator/oil cooler, intercooler, and exhaust exit) aft of the CP of the wing and aft of the boundary layer separation from fuselage and wing.)



The next significant CDp factor was the Friction Drag Delta CD = .0008 + 'Gap' Drag Delta CD = .0004 = .0012 which is Constant for All RN - a Very low value speaking to the following: 1.) Extremely good production design co-ordinated with factory processes to achieve extremely good sheet butting, flush riveting, excellent jigs and fixture design, priming/sanding/painting of upper and lower wing surfaces through ~ 40% wing chord, and placement of important panels at or aft of that region. 

These values for CDp were the very best in comparison with all the values I have seen presented for other aircraft. 

Looking to Hoerner 14-4 (b.) Drag of the Wing ------------> the comparable Friction drag for paint irregularities, gaps, bumps, sheet edge and rivet losses @ RN=1.1X10^^7 (For ONLY the wing) ----------> .0035 (skin friction) plus .010 (gap/surface imperfections). Compare to .0008 plus .0004 for the P-51 values above. More than 10x Bf 109G total skin friction and surface imperfection components for the wing drag over P-51B drag.

Hoerner does not present the individual components of parasite drag as a function of RN like NAA. That said, the clues for his Parasite Drag as function of RN @ 4x10^^6 (Wind tunnel at Chalais-Meudon for either Bf 109E or F in 1941) = CDp .030 Without momentum drag of engine air intake of that of the tail wheel.

The comparable CDp for RN=4x10^^6 for the P-51B = .0190 -----------> ~ 63% of the Bf 109E

Comparing CDp for his calculation of .028 @RN=2^^7, the comparable P-51B CDp = .0155 ----------> 55% of the Bf 109E

In Chapter 14 he 'reverse calculated total drag based on T=D;
For his Calculated Total Drag (CDt) at Vmax (= 380mph at 22,000 feet) = 0.036 [includes base parasite/form drag, vortex drag + high speed cooling drag) multiplied by Mach No. correction +Induced drag. For the P-51B, the same CDt = 0.24 ------------> 66% of the Bf 109G

Last note - the High Speed/Low Drag 45-100 wing while loosely described as Laminar (not so much), was extremely low drag in two areas of discussion. First, the low velocity gradient from LE to max T/c at 37.2 % was much lower than equivalent thickness 23016 airfoil which delayed Mach drag rise and major CP shift, and second - the form drag of the wing was simply lower.

I HAVE not spent a lot of time looking at the Hoerner discussion, but the P-51B drag values for CDp and CDp1(combined gun ports, radio mast, gaps/leaks, friction, etc) are extracted from the P-51B Report, compared to P-51D and P-51H to check for unexplainable variances (none other than P-51H had lower wing parasite drag)

Postscript. The Cooling drag build up for climb (worst case) was .0064 for a combination of internal pressure drag/flow losses of the scoop/plenum/oil cooler/radiator/exit plenum and open exit gate. So, if we take Horkey and Ashkenas at their technical competency, then for Net Zero high speed Cooling drag, the CD to be recovered by incremental Meredith Effect jet thrust = .0064. Thus, if Jet THRUST = 0 and all internal drag components are not neutralized, the the total drag build up for RN=2x10^^7 = 0.31 --------> 86% of the Bf 109G-6 calculated total by Hoerner.

Take what you want, leave the rest.

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## Shortround6 (Jan 18, 2019)

In the west (American and Britain) the Performance Number scale was developed. While this could be applied to any octane number of fuel it was rarely applied to under 100 octane. 100PN does equal 100 octane so any numbers over 100 are PN numbers. PN numbers under 100 explain a lot but get discouraging rather quickly.
OCt=PN
100=100
96=87.5
91=75.7
87=68.3
80=58.3
70=48.3

The octane scale was NOT linear and was really screwed up between 90 and 100. One can also see the huge improvement between 87 oct and 100 oct, what one cannot see is that the British never published a rich rating for their 87 octane fuel. 


The Germans _may_ have shot themselves in the foot with their fuel injection system. I am open to correction on this, by my thinking goes along like this.

The allied fuel was rated at lean (low number) and rich condition (high number) and difference was that under rich conditions the fuel system was providing 30-40% more fuel per HP (or per pound of air) than it was at lean condition. I don't know if the German fuel injection system could reach this level of "richness". Now it might not have necessary to quite go that far as the Germans did have better fuel distribution (less difference between rich and lean cylinders) but the Germans may not have been using excess fuel as an internal coolant either. 

German fuel when tested by the allies often did have a good (and sometimes excellent) rich rating, but if the engine is not set up to take advantage of it where are you? 
The next problem is that unless the purchasing dept specifies a particular rich response it can vary from batch to batch even at the same refinery let alone between refineries, Just because batch A was 96/135 doesn't mean batch B is any better than 96/120 for instance.

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## Shortround6 (Jan 18, 2019)

drgondog said:


> I will devote a lot of time in the Apendices of my new book on this very subject:
> .



Welcome back

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## tomo pauk (Jan 18, 2019)

gliding said:


> The comparison of fuels and their knock resistance is not possible over "the" octane number. Then and now different methods of measurement are used.
> For the comparison, one needs a test engine, which is operated with Isooctane. Depending on this test engine, there are different "octane" numbers.
> _(An early German C3 fuel (95 german-octane) was roughly comparable to a 100 US-octane fuel.)_



No problems with this.



> The production of high-octane gasoline was complex and expensive and could not be realized in the required extent by Germany in the last years of the war.



Agree pretty much.
On the other hand, crediting just the fuel quality for performance gap existing between Mustangs and Bf 109s would've mean a discreditation of engineers at NACA, NAA, RR etc. Again - we know that Bf 109F1 or F2, fighters whose engines used hi-octane fuel, were slower by large margin than P-51A (Mustang II) on when on similar engine powers vs. altitude.



> Reports from Daimler show that higher performance was possible even without GM or MW50. The required fuel was not sufficiently available.



Higher performance was certainly possible with higher octane fuel. However, when we have both Bf 109 and P-51 with hi-oct fuel and no anti-detonant injection, Bf 109 will come as second best, speed wise.


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## Snowygrouch (Jan 18, 2019)

I`m not following why we are discussing octane, the title of the thread is why the PLANE was slower, in that respect it is a simple matter to write down the horsepower outputs of each engine (which are all known very well).

Getting into a mess about octane numbers and engine development is a new thread, and WHY the engines were making less power is not the same question.

Just my opinion, I think the thread would be better served concentrating on the aero-features, whilst acknowledging the thrust power available to each plane.

Its very clear from Archival records that the big factor here is airframe, as is evident from the utter shock at the British air ministry at the performance of the Mustang over the Spitfire with essentially an identical engine. Of course the 109 shares neither the airframe NOR the engine, but all I`m saying is that in my view - I`d be far more interested in discussing the aero than octane stuff - I`m not very convinced another DB vs RR thread will help the original post ? - maybe the original poster can clarify whats wanted !


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## gliding (Jan 18, 2019)

My post was a comment on #19. The engine technology (performance) would certainly have led to similar results for the Germans, if the same materials (fuel, metals, ..) would have been available.

A comparison of Bf 109 to P-51 is in my view without sense. The Bf 109 was developed when biplanes still served in many air forces. The first flight was in 1935.
The P-51 had its maiden, as already the 5th generation of the Bf 109 was produced. The experience from the war led to the specification. 

A better comparison would be P-51 and Me 262. Both come from the same generation.

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## jetcal1 (Jan 18, 2019)

gliding said:


> My post was a comment on #19. The engine technology (performance) would certainly have led to similar results for the Germans, if the same materials (fuel, metals, ..) would have been available.
> 
> A comparison of Bf 109 to P-51 is in my view without sense. The Bf 109 was developed when biplanes still served in many air forces. The first flight was in 1935.
> The P-51 had its maiden, as already the 5th generation of the Bf 109 was produced. The experience from the war led to the specification.
> ...


Better yet, P-36 versus Bf-109.

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## Schweik (Jan 18, 2019)

gliding said:


> My post was a comment on #19. The engine technology (performance) would certainly have led to similar results for the Germans, if the same materials (fuel, metals, ..) would have been available.
> 
> A comparison of Bf 109 to P-51 is in my view without sense. The Bf 109 was developed when biplanes still served in many air forces. The first flight was in 1935.
> The P-51 had its maiden, as already the 5th generation of the Bf 109 was produced. The experience from the war led to the specification.
> ...




Lol

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## tomo pauk (Jan 18, 2019)

gliding said:


> My post was a comment on #19. The engine technology (performance) would certainly have led to similar results for the Germans, if the same materials (fuel, metals, ..) would have been available.



I'll disagree as before.
For aerodynamical reasons of why Bf 109 was slower than P-51, please see post #27 by Bill, who is a) one of prominent scholars on P-51 and b) engineer that worked in industry, including Lockheed for example. 
For 'power' reasons*, Germans missed opportunity to design & produce a V12 engine with 2-stage supercharger until it was too late. Jumo engineers designed the Jumo 213E, a 3-speed 2-stage supercharged engine that used 87 oct fuel. No fancy metals are needed for a 2-stage S/C, people at RR designed a service-worthy 2-stage S/C engine in 1941-42, at Jumo and DB in late 1944. The Bf 109 was slated for DB-605L for spring of 1945. 
Mentioning the quality of fuel and metals are worn-off excuses for lacklustre performance of German fighters in 1944.

* the author of the video devoted a few minutes to this



> A comparison of Bf 109 to P-51 is in my view without sense. The Bf 109 was developed when biplanes still served in many air forces. The first flight was in 1935.
> The P-51 had its maiden, as already the 5th generation of the Bf 109 was produced. The experience from the war led to the specification.



5th generation of Bf 109 in October of 1940? That's something new. 
What particular experience from the war had to do with any crucial technology P-51 used to a good cause, ditto with specification?



> A better comparison would be P-51 and Me 262. Both come from the same generation.



I disagree, but you are certainly entitled to your opinion.

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## Shortround6 (Jan 18, 2019)

The 109 is a mish-mash. 


gliding said:


> The Bf 109 was developed when biplanes still served in many air forces. The first flight was in 1935.







Not exactly the best radiator set up, strut braced tail plain, no ejector exhaust. 




Carb (or air) intake not the best. Spinner and forward cowl looks a bit suspect. 

By the 109F 




Better radiators under the wings (with bounder splitters?)Better even if not great air intake., Better spinner, front of cowl. (canopy still sucks). ejector exhausts, wing tips have gone from square to round (????) changes in ailerons, and slats form early models (? asking, not telling?)struts for the tail plain have gone away. The 109 got a redo in 1940 and not a minor one.

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## GrauGeist (Jan 19, 2019)

gliding said:


> A comparison of Bf 109 to P-51 is in my view without sense. The Bf 109 was developed when biplanes still served in many air forces. The first flight was in 1935.
> The P-51 had its maiden, as already the 5th generation of the Bf 109 was produced. The experience from the war led to the specification.


The Bf109 had it's first flight in 1935 BUT it was accepted into service in 1937.
It should be also pointed out that the Hurricane first flew in 1935 and entered service in 1937, and the same for the P-36, first flight in 1935, though it entered service in 1938. All of which were world class fighters for their time.

The P-51 had it's first flight in 1940 and entered service in 1942. By 1942, the Bf109 had matured considerably, by way of engine, aerodynamics and firepower.



gliding said:


> A better comparison would be P-51 and Me 262. Both come from the same generation.


This is not even a consideration - the technology and design between the both are night and day.

Why not compare the P-51 to the He280? The He280 was the world's first combat jet and designed as a true fighter. It also shared a development timeline comparable to the P-51.


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## parsifal (Jan 19, 2019)

Can anyone extrapolate or guess what the performance increase in bf109g might have been had been provided with 130 or 150 octane fuel like the P-51?


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## gliding (Jan 19, 2019)

I think I did not express myself correctly. The P-51 was a wonderful aircraft and also superior to the Bf-109. No doubt. It is also a great airplane for me. But in my view, it's not fair to compare a development started > 5 years earlier.



tomo pauk said:


> What particular experience from the war had to do with any crucial technology P-51 used to a good cause, ditto with specification?



The order for a fighter-development received Messerschmitt in February 1934. It should be fast with short range and low altitude. It should only carry 2 MG17 (7.9 mm) and the undercarriage must be attached to the fuselage. Maybe the wrong demands, but the order to Messerschmitt. The solutions of the engineers were in my opinion (1935!) more than good. Airplanes of the same time (Spitfire development starting from 1935, Hurrican development starting from 1933) were on similar level.

The P-51 should be a long-range hunter. Great heights were required. The Mk I wore 4 machine cannon and 4 machine rifle. Demands from the current war.



tomo pauk said:


> For aerodynamical reasons of why Bf 109 was slower than P-51, please see post #27 ....



The results are undoubted. Dr. Hoerner also wrote (14-7): "If rebuilding the ME-109 in a manner that would reach 100%, the maximum speed would be 610 to some 800 km / h, if using the same power plant." Even in the ideal case, the speed of the P-51 could only be achieved with a larger engine. A larger engine did not fit in the Bf-109. The diagram of Dr. Hoerner shows the development of the parasite drag coefficient. It also shows the difference of 5 years. European scientific sources say degreasing drag coefficient reduction of 1920 (100%) -> 1932 (88%) -> 1936 (51%) -> 1940 (42%). However, it should also be mentioned here that these results were determined many years later (Dr. Hoerner, 1957).

Messerschmitt had also recognized that the Bf-109 was outdated. The planned replacement "Bf-209" with DB603 could be possible compared with the P-51. It also has similar performance data. However, the policy was afraid that a change of the series production could mean a loss of quantity. In addition, Messerschmitt (also Focke-Wulf, according to Kurt Tank) was in this time no more interested in piston aircraft, because he saw the jet aircraft as future.



tomo pauk said:


> 5th generation of Bf 109 in October of 1940? That's something new.



Not really new. B - C - D - E - F. Until the end (K), the adjustments were always small. The biggest change was E -> F, not a priority for performance but in more production-efficiency. (Blueprints for F are dated from mid-1940)




tomo pauk said:


> I disagree, but you are certainly entitled to your opinion.



The comparison P-51 - Me-262 should be fun. Nevertheless, they were designed at the same time. If you want to make a "real" comparison, maybe P-51 and Do335 would be suitable. Again, different requirements and solutions, but also here you can see that about the same time comparable benefits were achieved.

Yes, that's my opinion and thank you for allowing me to. I think a forum lives from different opinions. I do not want to convince anyone.


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## tomo pauk (Jan 19, 2019)

gliding said:


> I think I did not express myself correctly. The P-51 was a wonderful aircraft and also superior to the Bf-109. No doubt. It is also a great airplane for me. But in my view, it's not fair to compare a development started > 5 years earlier.



Probably it is not fair.



> The order for a fighter-development received Messerschmitt in February 1934. It should be fast with short range and low altitude. It should only carry 2 MG17 (7.9 mm) and the undercarriage must be attached to the fuselage. Maybe the wrong demands, but the order to Messerschmitt. The solutions of the engineers were in my opinion (1935!) more than good. Airplanes of the same time (Spitfire development starting from 1935, Hurrican development starting from 1933) were on similar level.
> 
> The P-51 should be a long-range hunter. Great heights were required. The Mk I wore 4 machine cannon and 4 machine rifle. Demands from the current war.



British, the people that aproached NAA to make P-40s didn't asked for anything like. NAA offered them a 'better fighter than P-40'. Long range was not specified, Mustang I was even without drop tanks facility. Neither were the great heights specified, the Mustang was featuring 1-stage supercharged V-1710 that had lower altitude-power than the old Merlin III.
Mustang I didn't wore cannons until well into 1942. Look at the armament from British perspective - their pre-war Hurricanes and Spitfires were outfitted with 8 LMGs, the cannon-armed fighters were in the design phase in 1938/39, so Mk.I with 4 HMGs and 8 LMGs is nothing awe inspiring to them.

added: RLM didn't asked for undercarriage to be attached to fuselage - MTT used the known tech from BF 108, while the He 112 was not disqualified because of the place the U/C legs were attached. I agree that MTT did a good, if not a great job with Bf 109.



> The results are undoubted. Dr. Hoerner also wrote (14-7): "If rebuilding the ME-109 in a manner that would reach 100%, the maximum speed would be 610 to some 800 km / h, if using the same power plant." Even in the ideal case, the speed of the P-51 could only be achieved with a larger engine. A larger engine did not fit in the Bf-109. The diagram of Dr. Hoerner shows the development of the parasite drag coefficient. It also shows the difference of 5 years. European scientific sources say degreasing drag coefficient reduction of 1920 (100%) -> 1932 (88%) -> 1936 (51%) -> 1940 (42%). However, it should also be mentioned here that these results were determined many years later (Dr. Hoerner, 1957).



That drag reduction was not applied to any design from those years, some designers/companies did a better job, other failed. Hurricane was much draggier than Bf 109, Me 210 and Welkin were much draggier than Mosquito, Typhoon was much draggier than Mustang.
Bf 109 was certainly able to accept DB 605L, a 2-stage superchaged engine from 1945. The DB 605AS/ASM engines were also fitted, bringing the altitude powers to levels of 2-stage Merlins. Problem with those engines is their late introduction.
Then we have aerodynamics improvements - all the time use retractable tailwheel, cover the Wheel wells, avoid the draggy HMG installation, introduce better radiators (whether in leading edge extensions like on Mosquito, or take a page from Italian or Soviet fighters, or from D.520, or go with annular radiator), blended ram air intake like on He 100. Some of these improvements were fitted on the K series.



> Not really new. B - C - D - E - F. Until the end (K), the adjustments were always small. The biggest change was E -> F, not a priority for performance but in more production-efficiency. (Blueprints for F are dated from mid-1940)



I see the B/C/D as one generation, E as another, F as another. The F series represented a major improvement of aerodynamics vs. E.



> The comparison P-51 - Me-262 should be fun. Nevertheless, they were designed at the same time. If you want to make a "real" comparison, maybe P-51 and Do335 would be suitable. Again, different requirements and solutions, but also here you can see that about the same time comparable benefits were achieved.
> 
> Yes, that's my opinion and thank you for allowing me to. I think a forum lives from different opinions. I do not want to convince anyone.



1940 and 1942 are not same time.
As for the P-51 vs. Do 335, I'd pick P-51H - on just one engine, it is no worse a fighter than Do 335 that needed two.

added: without different opinons, we would never have meaningful discussion, whether in forums or otherwise. I am certailnly not the one allowing/disallowing people from expressing their opinions.

*edited due to the typos/grammar and additions*

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## Shortround6 (Jan 19, 2019)

gliding said:


> Not really new. B - C - D - E - F. Until the end (K), the adjustments were always small. The biggest change was E -> F, not a priority for performance but in more production-efficiency. (Blueprints for F are dated from mid-1940)



I am agreeing with Tomo. The B-D were one generation, differences were minor and often just a change in equipement. 
I am not sure if you could turn a D into an E, to would take quite a bit of work and parts. 
But an E is basically a D with a new engine, new radiator installation (and oil cooler) and larger fuel tank. 

The F has a lot more changes to the basic airframe and no, it wasn't just for production reasons. An early F was 20-30mph faster than a late model E when using the same engine. Later Fs did get higher powered engines but the change from a 350mph airplane to a 390mph airplane was NOT due to the new engine alone. This is the major break between the 1935 109 and the 1944-45 109s. from the F on there was little or no aerodynamic refinement and performance increases came from fitting increasing more powerful engines. Which unfortunately for the Germans and fortunately for the rest of the world, often had teething troubles that lasted for months and prevent full use from being made of the hoped for power increase. 
late 109s were a mad scramble to get something into the air and aerodynamic refinement went out the window. The wing bulges over the tires on the K series may have negated much of the gain from the auxiliary wheel well doors for example.

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## nuuumannn (Jan 19, 2019)

Shortround6 said:


> The F has a lot more changes to the basic airframe and no, it wasn't just for production reasons



Yup, the 'F was arguably the peak of design development of the Bf 109 as a pure fighter. Yes, you could argue that the K and marks of the G were faster etc, but they were swiftly overtaken by events and by then, the Bf 109's basic design was a bit long in the tooth. At the time the Friedrich entered the fray the Bf 109 was at the top of its game; it was the best fighter in service in Western Europe; the aerodynamic changes over the Emil did pay off, but they came at a price; the removal of the tailplane bracing struts did cause early 'Fs to suffer structural failure owing to tail flutter at high speeds, leading to the aircraft being grounded, but strengthening was undertaken. The Friedrich also had a governed constant speed prop for the first time in a '109, previous iterations being variable pitch only.

AS SR stated, in the Gustav the aerodynamics suffered. Those bigger guns and wheels resulting in protrusions did nothing for the the aircraft aerodynamically or appearance wise; the Gustav wasn't nicknamed the 'Beule' for nothing!

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## Schweik (Jan 20, 2019)

Maybe the obvious basis for.comparison is that they in fact competed directly in combat thousands of times. The Bf109G and K etc. variants that faced P-51B and C in 1943 were obviously not the same fighter as the 1935 design that saw action in the Spanish Civil War, nor was a Spit 21 the same bird as a Spit I from the BoB.

Whether using an earlier design for the basis of the latest front line fighter or coming up with something entirely new, the challenge was much the same. Changes radical enough to meet the harsher and harsher standards of each new year of the war were likely to pose a host of problems in implementation. 

Getting new engines to work properly, or new wings better streamlining, a new fuselage etc. is going to take a while and break the hearts of a lot of good engineers and mechanics in the process. A brand new aiframe poses even more potential teething hazards than a major upgrade but also offers the potential of new design improvements that bypass old limitations. Either way its a gamble 

This was the challenge faced by North American Aviation when asked to produce P-40s for England (or further extend the even older P-36, depending how you look at it). They took a risk and got lucky with their streamlining and exhaust system, but still had a lot of teething problems (like bad ailerons.) The fuel capacity seems to be almost a happy accident.

Orher more radical designs like the Do 335 and the 262 (or He 280) never got through their teething / implementation challenges quickly enough to make it into the field in sufficient numbers to make a difference in the war.

Even the 262, while it probably could have had a greater impact as a heavy bomber killer if political circumstances had been different, may not have been a mature enough design to change thimgs on the Russian Front for example, or over the Tactical Battlefield over Europe.

Ultimately the German designers and engineers for all their skill, also made mistakes and reached the limits of their abilities. They were way ahead of the game in 1936, and even still in 1940 to a large degree (the Spitfire being the one glaring exception), but by 1943 they had lost a step in the face of onrushing doom and annihilation in the zero sum game they themselves had instigated.

The designers of the Allied countries proved to be as resourceful- and more, in the long run.

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## fubar57 (Jan 20, 2019)

Schweik said:


> Maybe the obvious basis for.comparison is that they in fact competed directly in combat thousands of times. The Bf109G and K etc. variants that faced P-51B and C in 1943 were obviously not the same fighter as the 1935 design that saw action in the Spanish Civil War, nor was a Spit 21 the same bird as a Spit I from the BoB.


The Bf 109K faced the P-51 in '43?


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## GrauGeist (Jan 20, 2019)

The shortcomings of the Germans was their approach to production and manpower.

*IF* they had started the war on a wartime footing AND not made questionable decisions regarding where to launch new fronts, then perhaps they might have had a chance.

Waiting until 1944 to peak aircraft production five years AFTER starting the war is not going to lead to any measure of success.

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## Schweik (Jan 20, 2019)

fubar57 said:


> The Bf 109K faced the P-51 in '43?



Grouping all variants that faced it from 43 to the end. Sorry I was typing on a phone.


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## michael rauls (Jan 20, 2019)

Speaking of the 109k I read once that about 2000 were made but only about 200 ever saw combat. Other than this one statement in one article I've never run across anything else pertaining to numbers of k's built or deployed.
Would be interested if anyone could confirm or dispell this.


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## swampyankee (Jan 20, 2019)

One thing to remember is that the NACA was formed to advance aeronautics and directly improve aircraft performance, construction, and design methods, with the information being made widely available. To a great extent, it was _the _world's source for this information, with, for example, NACA airfoils being used by German aircraft, such as the Bf109. 

I don't know how mobile German aeronautical engineers were, but US ones have long been notorious job hoppers, which means that there is quite a lot of inter-company intellectual cross-fertilization.

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## fubar57 (Jan 20, 2019)

michael rauls said:


> Speaking of the 109k I read once that about 2000 were made but only about 200 ever saw combat. Other than this one statement in one article I've never run across anything else pertaining to numbers of k's built or deployed.
> Would be interested if anyone could confirm or dispell this.



Wiki cites these books as sources for the production numbers so I think it might be safe to quote Wiki in this case, "...Deliveries began in mid-October 1944 and 534 examples had been delivered by the Messerschmitt A.G., Regensburg by the end of November and 856 by the end of the year.[105][106] Regensburg delivered a total of 1,593 by the end of March 1945, after which production figures are missing.[_citation needed_] With such a high rate of production, despite continuous heavy fighting, by the end of January 1945, 314 K-4s – about every fourth 109 – were listed on hand with the first line _Luftwaffe_ units..."

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## michael rauls (Jan 20, 2019)

fubar57 said:


> Wiki cites these books as sources for the production numbers so I think it might be safe to quote Wiki in this case, "...Deliveries began in mid-October 1944 and 534 examples had been delivered by the Messerschmitt A.G., Regensburg by the end of November and 856 by the end of the year.[105][106] Regensburg delivered a total of 1,593 by the end of March 1945, after which production figures are missing.[_citation needed_] With such a high rate of production, despite continuous heavy fighting, by the end of January 1945, 314 K-4s – about every fourth 109 – were listed on hand with the first line _Luftwaffe_ units..."
> 
> View attachment 526332
> View attachment 526333​


Thanks George. Looks like a good adition to my prospective reading list. I tried to rate your post as useful but at least on my screen the ratings aren't working right now.
Might just be a problem with my phone.
Thanks again.

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## stona (Jan 20, 2019)

nuuumannn said:


> Yup, the 'F was arguably the peak of design development of the Bf 109 as a pure fighter.



I don't disagree from an aerodynamic point of view, but it was badly under armed for a1941/42 fighter.

An MG-FF cannon (admittedly later upgraded to the faster firing MG 151/15) and a couple of 7.92mm MG 17s is nothing to shout about. It was fine for shooting down P-40s and Hurricanes in the MTO I suppose.

Cheers

Steve


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## Schweik (Jan 20, 2019)

I think they're mainly talking about speed here.

But I also think the armament on a 109F was sufficient for shooting down Spitfires and Yak ones and sevens and P-38s and Pe 2s and Blenheims & Bostons & Baltimores and B 25s and pretty much anything else they needed to shoot down while they were in action.

When more heavy bombers and better-armed Il-2's hit the battlefield the need for heavier armament was addressed in the G series if perhaps in a less than ideal manner.


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## nuuumannn (Jan 21, 2019)

stona said:


> An MG-FF cannon (admittedly later upgraded to the faster firing MG 151/15) and a couple of 7.92mm MG 17s is nothing to shout about.



Depends on who you're talking to. Galland thought the same thing as you, but both Molders and Maseille said that was all they needed to shoot down the enemy. Yes, other fighters had heavier armament, but that didn't stop the Friedrich out performing the Spitfire V - the frontline RAF interceptor in almost every respect, with the exception of the turn and as one RAF pilot said when this was pointed out to him, "Turning doesn't win battles!" It's record speaks for itself; the 'F was a very potent fighter.


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## stona (Jan 21, 2019)

nuuumannn said:


> Depends on who you're talking to. Galland thought the same thing as you, but both Molders and Maseille said that was all they needed to shoot down the enemy.



It was all they needed to shoot down enemy fighters, which were the target at the time. Once the Luftwaffe was forced onto the defensive it became completely inadequate. There was a good reason that the early G-series had a commonly used option for two MG 151/20s under the wings. By early 1943, when the G-6 started reaching front line units much heavier armament came as standard ( two heavy MG 131s and an MG 151/20 or MK 108 cannon) with the option for underwing cannon retained.

I'd also point out that what Molders and Marseilles thought they needed might not apply to many other Luftwaffe pilots  Didn't Bader persevere with 8 pop guns after cannon were introduced? He was good enough to make them count at very short range and he was confident that they wouldn't let him down. Most of his contemporaries couldn't fly like him, however much of an a-hole he may have been!

Cheers

Steve


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## tomo pauk (Jan 21, 2019)

Schweik said:


> I think they're mainly talking about speed here.
> 
> But I also think the armament on a 109F was sufficient for shooting down Spitfires and Yak ones and sevens and P-38s and Pe 2s and Blenheims & Bostons & Baltimores and B 25s and pretty much anything else they needed to shoot down while they were in action.
> 
> When more heavy bombers and better-armed Il-2's hit the battlefield the need for heavier armament was addressed in the G series if perhaps in a less than ideal manner.





nuuumannn said:


> Depends on who you're talking to. Galland thought the same thing as you, but both Molders and Maseille said that was all they needed to shoot down the enemy. Yes, other fighters had heavier armament, but that didn't stop the Friedrich out performing the Spitfire V - the frontline RAF interceptor in almost every respect, with the exception of the turn and as one RAF pilot said when this was pointed out to him, "Turning doesn't win battles!" It's record speaks for itself; the 'F was a very potent fighter.



Agree with Steve here - Germans introduced gondola cannons as an option already for the F series, and G2 with gondolas were used by 1942 and early 1943 both in East and MTO. They certainly didn't felt that every pilot is a world-class marksman. 

Perhaps the Germans failed to pick the low-hanging fruit until too late - the belt-fed MG FFM, available from some time 1943 and used on night-fighter Do 217s with 200 rpg. A Bf 109F with 3 internally-mounted, belt-fed MG FFMs, anyone?


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## DarrenW (Jan 21, 2019)

From reading the discussion so far, I'm under the impression that the only way the BF 109 could ever compete on anything like equal terms with Allied aircraft such as the P-51D it needed vastly more horsepower. The air frame refinements found on the the later G and K models did very little in the way of overcoming its relatively inferior aerodynamics. The performance gap seems to have been closed somewhat by the implementation of over-boosting, using water-methanol injection and/or higher octane fuels, but 109 pilots were still left wanting. 

I haven't seen any discussion here concerning the rather poor manufacture quality of late-war 109s, which must have also played some role in its apparent inferiority to the Allied fighters that it faced by 1944.

From Spitfire Mk XIV versus Me 109 G/K:

_Conditions in Germany during the last year of the war, however, were not conducive to aircraft achieving maximum theoretical performance levels. Hans Knickrehm of I/JG 3 recalled the condition of new Me 109 G-14/AS’s received by his group in October, 1944:
_
_The machines that were delivered were technically obsolete and of considerably lowered quality. The engines proved prone to trouble after much too short a time, because the factories had had to sharply curtail test runs for lack of fuel. The surface finish of the outer skin also left much to be desired. The sprayed-on camouflage finish was rough and uneven. The result was a further reduction in speed. We often discovered clear cases of sabotage during our acceptance checks. Cables or wires were not secured, were improperly attached, scratched or had even been visibly cut..._​
And I know it's a gaming forum but there's actually some intelligent conversation going on here, intermixed with both snippy and childish remarks too I'm afraid.... 

The K-4 Isn't Special

Some comments made in this thread:

_.....All DB 605D and ASB-ASC engines were cleared for 1,98 ata at that time (i.e. the month before and after Bodenplatte) _


_"Chin bulges on the lower cowling - this was present only on aircraft with uprated DB 605 ASB/ASC engine (same engine, designated differently depending on fuel/boost used). These engines could operate on either B-4 / 87 octane fuel up to 1.8ata (ASB), or 1.98ata with C-3 fuel (designated as ASC). This particular aircraft has a C-3 fuel triangle, pointing towards that it uses the latter ASC rating._



_












_

I was under the impression that 1.8 ata was the highest boost setting ever approved for field use. Anyone have data to refute this notion? 

And surely C3 fuel must have been used to a greater extent than most realize. I happen to see far too many photos to believe otherwise. But on the other hand maybe it was normal practice for B4 fuel to be used in place of the seemingly rarer C3, so these markings didn't necessarily denote the actual fuel used????

From a Wiki article on the DB 605 engine ( Daimler-Benz DB 605 - Wikipedia ):

_The DB 605AM, running initially on C3 and MW-50, saw power improved to 1,800 PS (1775 hp) for takeoff. In mid-1944, the requirement for C3 was dropped and standard B4 fuel with MW-50 was used. _

_As early as 1942 Daimler had also been working on an upgraded D-series engine that could run on either C2 or C3 fuel. The first of these, which appeared in late 1944, were a small series of DB 605DM, followed by the main production series, the DB 605DB/DC. These engines were fitted with an adjustable screw stop which allowed the use of either B4 fuel with MW-50, or C-3 fuel without MW-50, in which case the engine was designated DB 605DB, or the use of C-3 fuel with MW-50, in which case the engine was given the -DC suffix instead... _

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## tomo pauk (Jan 21, 2019)

DarrenW said:


> From reading the discussion so far, I'm under the impression that the only way the BF 109 could ever compete on anything like equal terms with Allied aircraft such as the P-51D it needed vastly more horsepower. The air frame refinements found on the the later G and K models did very little in the way of overcoming its relatively inferior aerodynamics. The performance gap seems to have been closed somewhat by the implementation of over-boosting, using water-methanol injection and/or higher octane fuels, but 109 pilots were still left wanting.
> 
> I haven't seen any discussion here concerning the rather poor manufacture quality of late-war 109s, which must have also played some role in its apparent inferiority to the Allied fighters that it faced by 1944.
> ...



Aerodynamic refinements do count. The K-4 introduced the more stremlined HMG installation, wheel well covers, and reintroduced retractable tailwheel - all of that accounted for 20+ km/h more than 109Gs with DB 605ASM and 605D engines. The K-4 was upposed to do 710 km/h at 7.5 km with 1565 PS (441 mph at 24600 ft with 1543 HP), that is a ballpark with P-51D that used ~1500 HP to do the same.

This also shows at least two things:
- size matters (smaller size can get you fly fast)
- P-51 was one very, very sleek fighter


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## swampyankee (Jan 21, 2019)

_Every_ report I've seen has shown the P-51 had, by far, the lowest zero-lift drag coefficient reported for _any_ piston-engined aircraft of the era, at about 0.016 to 0.018. The Bf109 was quite high, at 0.027 to 0.029. All the other monoplane fighters were in the band of about 0.020 to 0.025, regardless of type of piston engine: radial, V-12, or H-24, with most aircraft between, if I recall, between 0.021 and 0.024.

To a great extent, the BF109 was at the opposite end of the bell curve as the P-51. This is one reason (there are others....) why I claim that the US had, on average, better aircraft designers than did the nazis.

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## nuuumannn (Jan 21, 2019)

stona said:


> Most of his contemporaries couldn't fly like him, however much of an a-hole he may have been!



Ha ha! Funny!




tomo pauk said:


> They certainly didn't felt that every pilot is a world-class marksman.



True. The fact that the three guns alone still enabled it to be a potent fighter is not in dispute, though. The canoe guns did affect handling and manoeuvrability, however; virtues that the F maintained, but were lost on subsequent variants.


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## Schweik (Jan 21, 2019)

Does the zero lift drag coefficient take into consideration the size of the object (like the wingspan) or is it just like a per meter kind of thing? 

Is there a list of the drag coefficients for different aircraft by type?

The 109 had a lot of protrusions, tail wheel and open wheel wells and everything but it was such a small aircraft. That is why it had relatively low drag.

Wasn't until the ultra streamlined P-51 showed up that they arguably needed to focus more on reducing drag further.

The low drag wing of the P51 seems to have lost a little bit and lift because it doesn't turn all that well despite being pretty big, or maybe that's just a factor of weight


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## DarrenW (Jan 21, 2019)

tomo pauk said:


> Aerodynamic refinements do count. The K-4 introduced the more stremlined HMG installation, wheel well covers, and reintroduced retractable tailwheel - all of that accounted for 20+ km/h more than 109Gs with DB 605ASM and 605D engines. The K-4 was upposed to do 710 km/h at 7.5 km with 1565 PS (441 mph at 24600 ft with 1543 HP), that is a ballpark with P-51D that used ~1500 HP to do the same.



Hmm, I don't know if 12 mph is such a monumental increase, given the extent of the refinements you mentioned. I'm also wondering if suspected poor quality control negated a lot of the possible performance improvement that these changes could bring. And wasn't that speed only an estimate, as no real-world test data exists for the K series? I'm fully prepared to be wrong about this.


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## tomo pauk (Jan 21, 2019)

nuuumannn said:


> True. The fact that the three guns alone still enabled it to be a potent fighter is not in dispute, though. The canoe guns did affect handling and manoeuvrability, however; virtues that the F maintained, but were lost on subsequent variants.



What enabled the 109F4 (and less applicable to the F1 and F2) was that big & powerful engine was installed on smalll, light and reasonably well streamlined fighter.



Schweik said:


> Does the zero lift drag coefficient take into consideration the size of the object (like the wingspan) or is it just like a per meter kind of thing?
> 
> Is there a list of the drag coefficients for different aircraft by type?
> 
> ...



Cd0 does not take into consideration size of object. 
List of Cd0 for different aircraft can be made from different sources, eg. the Cd0 for the 109F4 is/was 0.0232 per manufacturer data. 109E were 'dirtier', 109G5s were also 'dirtier'. British have an useful list, posted here, for many A/C. NACA reports have a lot of data, too. Germans were probably aware that Bf 109 will be over-shadowed by new Allied fighters, hence Bf 209 and 309 fighters, plus jets.
Lift-to-drag (L/D) ratio of the wing profile choosen for the P-51 wasn't greatest indeed, that combined with usually high weight didn't made it into a turning champion.

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## DarrenW (Jan 21, 2019)

Schweik said:


> Does the zero lift drag coefficient take into consideration the size of the object (like the wingspan) or is it just like a per meter kind of thing?



Total drag (CD) - induced drag (CDi) = zero lift drag (CD0)

Both total drag and induced drag take wing area into account.

Equivalent flat plate area (or "drag area") is zero lift drag x wing area. Some say that this is a true representation of an aircraft's "foot print" and how much thrust is needed to overcome total drag.

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## tomo pauk (Jan 21, 2019)

DarrenW said:


> Hmm, I don't know if 12 mph is such a monumental increase, given the extent of the refinements you mentioned. I'm also wondering if suspected poor quality control negated a lot of the possible performance improvement that these changes could bring. And wasn't that speed only an estimate, as no real-world test data exists for the K series? I'm fully prepared to be wrong about this.



12 mph was certainly not a monumental increase, but it shows that improvement in streamlinign counts. The Bf 109K4 was still saddled with 3 radiators, the ram air intake is still 'outside' of airframe, the 2R1 wing profile was no longer competitive even if it was thin on the 109s. The 441 mph probably represented the best case scenario indeed.
There is a number of charts and tables for the K4 on the 'net, how good/bad (= based on the tests or manufacturers estimate) they are really is anyone's guess I suppose. 441 mph figure is from LW data sheet.

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## swampyankee (Jan 21, 2019)

Schweik said:


> Does the zero lift drag coefficient take into consideration the size of the object (like the wingspan) or is it just like a per meter kind of thing?
> 
> Is there a list of the drag coefficients for different aircraft by type?
> 
> ...



Yes. It’s a non-dimensional coefficient, so it provides a comparison that removes size differences. 

If I remember, the P-51 had a higher wing loading.


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## DarrenW (Jan 21, 2019)

tomo pauk said:


> but it shows that improvement in streamlinign counts.



Yes, off course streamlining counts but in my view the negative aerodynamic characteristics you mentioned above had a far greater impact on it's speed than the lack of wheel-well doors and the like. It just seems like a band aid attempt to overcome some truly poor aerodynamics by 1944 standards. 

The added parasitic drag of the leading edge slats must have not helped its case either.


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## Schweik (Jan 21, 2019)

swampyankee said:


> Yes. It’s a non-dimensional coefficient, so it provides a comparison that removes size differences.
> 
> If I remember, the P-51 had a higher wing loading.



It would at takeoff, but after climbing to altitude, forming up, and flying an hour or three to the target area maybe not.

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## drgondog (Jan 22, 2019)

Schweik said:


> Does the zero lift drag coefficient take into consideration the size of the object (like the wingspan) or is it just like a per meter kind of thing?
> 
> *The drag coefficients for a specific RN (see below) are individual component drag ("force) values observed in the wind tunnel as each individual component is isolated as a change, then divided by wing area. Only Wetted Area calculations are derived as Total Drag/Total surface area.*
> 
> ...



First - the Comparison of minimum parasite/profile drag requires that you research the RN for which the drag values were extracted in the Wind tunnel. 
Second - the RN is a function of Velocity, Kinematic Viscosity and Mean Aerodynamic Chord(based on the wing). E.G. the RN for a Bf 109G-6 at 300 mph at 25000 feet is totally different (lower because the m.a.c. of 109 wing is much less) from P-51 at same speed and altitude in a parallel run. RN=V(m.a.c.)/v where v = kinematic viscosity.

Third, Parasite/profile drag components have certain values that correlate with RN, (wing, fuselage, empennage, cockpit, carb duct, exhaust stacks, external radiator duct) and some that are constant with RN as they relate to pressure drag (gun ports, antenna, bomb rack, leaks/gaps, surface roughness). Also included in the Drag build up are the values of total drag introduced by changes of CL (as one must when altitude increases in order to maintain constant altitude in cruise).

Cooling Drag (internal losses in Radiator/Intercooling system), and prop vortex pressure drag are also independent of RN).

For any given flight profile all of the above factors are added together - then multiplied by the Compressibility factor which changes with increasing Mach No. (beginning somewhere above incompressible fluid region of approx. .3 Mach. THIS FACTOR is critical to comparisons between aircraft at high speeds. Bumps, slopes of windscreens, etc are important - but the WING is to core of this factor.... both airfoil shape and thickness play a role. E.G. The Spit wing was considerably 'thinner t/c ratio' than the Mustang and dived slightly faster without structural damage, but the Mustang wing with max t/c and quasi-wedge shaped airfoil reaching maximum value at ~37.2 % (vs 25-26% for most other WWII fighter) had both lower profile drag as well as delayed drag rise.

Last value added is Induced Drag which is added to all the Parasite/pressure drag elements corrected by compressibility factor.

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## Peter Gunn (Jan 22, 2019)

drgondog said:


> I will devote a lot of time in the Apendices of my new book on this very subject:
> 
> Start with Power Available vs Power Required as the fundamental set of calculations once the drag parameters are derived (wind tunnel testing);
> 
> ...



Man, I *really* wish you'd actually explain this stuff with fact, formula and sources and not just these apocryphal stories, superficial speculation and SWAG's...

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## Schweik (Jan 22, 2019)

Is there such a thing as a list of parasitic / profile drag for a variety of major fighter types, or is that going to be in the book? When is the book available I'm sold!


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## DarrenW (Jan 22, 2019)

Schweik said:


> Is there such a thing as a list of parasitic / profile drag for a variety of major fighter types, or is that going to be in the book? When is the book available I'm sold!



Having comparable trustworthy drag figures for the majority of WWII fighters is a moving target at best. Even for one aircraft type you'll find variations. Problem is to have comparable numbers the same wind tunnel and test conditions must best used, which is obviously not possible in every case.

But I guess one can still get a basic idea of how "clean" or "dirty" an aircraft is by using the data that's currently out there, so there is some value in that I suppose. You first just have to make sure that you are comparing apples to apples. A value for total drag (CD) of one aircraft should not be compared with another's zero-lift drag coefficient (CD0), as total drag is always greater than zero-lift drag.

By the way, early P-40s had a fairly low total drag number, as noted in NACA wind tunnel test results from the period:

NASA Technical Reports Server (NTRS) - Review of drag cleanup tests in Langley full-scale tunnel (from 1935 to 1945) applicable to current general aviation airplanes

But please note that even NACA insisted that it would be unwise to compare data between the various aircraft tested, and only the drag reduction results per type are useful to the engineer. Also note that many of these airplanes were early examples of production aircraft so I am sure there were some incremental improvements made to aerodynamic efficiency along the way.

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## nuuumannn (Jan 22, 2019)

tomo pauk said:


> What enabled the 109F4 (and less applicable to the F1 and F2) was that big & powerful engine was installed on smalll, light and reasonably well streamlined fighter.



Not saying it wasn't, my point is that _despite_ its three guns it still was a formidable fighter.

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## Dan Fahey (Jan 24, 2019)

The ME 109 K could get up to the 440 mph speed.
Read where the speeds got past 400mph the ME 109 was a good bit harder to maneuver.


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## spicmart (Mar 4, 2019)

I had read a max speed figure of 727 kmh/452 mph. Anyone knows about this?


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## spicmart (Mar 4, 2019)

Messerschmitt always had a clear focus on performance, speed and light build for his designs. Given this premise one might say that he was not better than other designers and his creation, with the exception of the Me 262, were not faster than other planes and often inferior in their characteristics. So his planes were not on the forefront of aerodynamic progress.

Someone said that laminar flow profile was not feasible because of the surface structure of the planes deteriorating thus negating the laminar flow. But I read that the Me 309 featured a laminar flow wing and the later Ta 152 variants as well.


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## Shortround6 (Mar 4, 2019)

I may have to tread lightly here, there seem to to be a multitude of definitions of "laminar flow" at the time (and even now) in that what can be achieved in the laboratory/wind tunnel is one thing. What can be achieved in the real world, even with a carefully crafted and tended high performance glider with a fiberglass/composite wing, what could be achieved with a metal wing (even with 20 coats of paint sanded between each coat and so on and so on................
There seems to have been something of a misunderstanding in regards to what was needed in surface finish instead of just changing the air foil in order to even get "laminar Flow" to occur over 30-40% of the wings surface. Some wings were referred to as "laminar flow" when they changed the maximum thickness of of the wing from about 30% of cord back to 40-50% of cord. It was a step and some of the best surface finish in the world wasn't going to give much of an improvement in laminar flow if the airfoil wasn't correct but the best airfoil in the world (in the lab/wind tunnel) wasn't going to work in the real world without surface finish standards that were pretty much unobtainable on a service aircraft. 

The P-51 did about the best and a 'good' P-51 maintained laminar flow to almost the 40% of cord mark, which is not laminar flow at all according to some people because it didn't maintain it all the way (or even 90%).

The Me 309 or late Ta 152 might have been designed with the intention of getting laminar flow, or at least getting more laminar flow (keeping it non turbulent) over higher percentage of the wing than previous wings but achieving that intention/goal was pretty much beyond the capabilities of the German aircraft industry at the time. 

So the question maybe were they designed with the intention/hope of getting laminar flow (or at least a significant reduction in drag) rather than if they achieved it.

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## tomo pauk (Mar 5, 2019)

spicmart said:


> I had read a max speed figure of 727 kmh/452 mph. Anyone knows about this?



That would be a speed value for the K-14, the version powered by DB 605L engine that was outfitted with a 2-stage supercharger.


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## spicmart (Mar 5, 2019)

tomo pauk said:


> That would be a speed value for the K-14, the version powered by DB 605L engine that was outfitted with a 2-stage supercharger.



The source gave it for the K-4 actually.


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## spicmart (Mar 5, 2019)

So the airfoils of a lot of WW2 fighers were obsolete/not competitive at the end? Afaik as the Me 109, Fw 190, F4U Corsair, F6F Hellcat, F7F Tigercat, F8F Bearcat et al are concerned.


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## tomo pauk (Mar 5, 2019)

spicmart said:


> The source gave it for the K-4 actually.



What source?


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## spicmart (Mar 5, 2019)

tomo pauk said:


> What source?



"Source" may be not be the right term. I read in a couple of publications. Would really have to look for it. Sorry, my bad.


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## spicmart (Mar 5, 2019)

Tomo. Would it have been possible to combine 150 octane fuel with MW50 injection and thus create a monster power output?


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## tomo pauk (Mar 5, 2019)

spicmart said:


> Tomo. Would it have been possible to combine 150 octane fuel with MW50 injection and thus create a monster power output?



Of course. P-47D did it in ww2, result was 2800 HP when 150 grade was used together with water/alcohol injection. The post-war US fuel was 145 grade, for example V-1650-9 produced 2200+ HP with water injection.


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## Shortround6 (Mar 5, 2019)

You do need an engine strong enough to stand up to power though


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## Shortround6 (Mar 5, 2019)

spicmart said:


> So the airfoils of a lot of WW2 fighers were obsolete/not competitive at the end? Afaik as the Me 109, Fw 190, F4U Corsair, F6F Hellcat, F7F Tigercat, F8F Bearcat et al are concerned.


That is a sort of "it depends" answer.
In addition to the basic airfoil shape you needed careful manufacturing to make it work.
The US found for example that the edge of paint from the national insignia on the wing disrupted the airflow to some extent. A lot of people say bug splat will disrupt the airflow. 
So you need a proper airfoil, good/excellent manufacturing and good/excellent maintenance in the field to get the benefit. Good airfoil with poor manufacture and maintenance doesn't get you anything while a less than optimal airfoil and good manufacturing and maintenance at least gets you close. 
It also depends on what you want it to do, the Mustang's airfoil was less than optimum for carrier operation. Yes they flew of carriers in trials but the handling, stalls, what not what was wanted.

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## spicmart (Mar 6, 2019)

tomo pauk said:


> Of course. P-47D did it in ww2, result was 2800 HP when 150 grade was used together with water/alcohol injection. The post-war US fuel was 145 grade, for example V-1650-9 produced 2200+ HP with water injection.




Can you estimate how much power would a 2700 PS Jumo 213J or 2800 PS DB 603N respectively be able to produce with high grade fuel?


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## tomo pauk (Mar 6, 2019)

spicmart said:


> Can you estimate how much power would a 2700 PS Jumo 213J or 2800 PS DB 603N respectively be able to produce with high grade fuel?



Who knows? 1st - I have never heard whether those power figures were attained with B4 or C3 fuel (MW 50 was used in both instances). So we'd probaby see 3200-3300 HP with best fuel around + MW 50. 
FWIW, I'll drop the PM to Calum, he is probably the most knowledgable person when it is about German aero engines of ww2 nowadays, to see whether he can share some info here.


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## Snowygrouch (Mar 6, 2019)

*DB603N =* 3200rpm
2800PS @2.1ata manifold pressure using B4+ MW50
3000PS @2.5ata manifold pressure using C3 + MW50

*Jumo-213J =* 3700rpm
2900PS 2.02ata with MW50 using B4
2400PS 1.66ata no MW using B4

I do not have any reliable documents on 213J with C3. However I would have thought that slightly over 3000PS would have been 
perfectly possible from the 213J with C3 and MW50.

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## tomo pauk (Mar 6, 2019)

Thank you.


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## spicmart (Mar 6, 2019)

Snowygrouch said:


> *DB603N =* 3200rpm
> 2800PS @2.1ata manifold pressure using B4+ MW50
> 3000PS @2.5ata manifold pressure using C3 + MW50
> 
> ...




2900 PS is a very high figure. I have only seen 2700 PS or more often less. The Jumo has greater exhaust thrust so would provide greater propulsion than the DB. Can you say more about it?


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## Shortround6 (Mar 6, 2019)

Am I missing something??

to have _greater_ exhaust thrust you have to have one of two things (or a bit of both) more mass per minute flowing through the engine, that is fuel, air and whatever additives you are using (like water/alcohol or higher pressure exhaust leaving the cylinder. Actually that is not quite right, you need higher pressure (higher velocity) exhaust gas leaving the exhaust outlets/nozzles. But on a V-12 with short nozzles there probably isn't a lot difference unless somebody screwed things up. 

If you are getting similar power to the propeller you are probably burning a similar amount of fuel/air in the cylinders (plus whatever it takes to drive the supercharger which is a point of variation, plus whatever it takes in friction to turn the engine over at the specified RPM that is the 2nd point of variation.) 

perhaps the Jumo opens it's valves when there is still higher pressure in the cylinders? But once open it is going to drop pretty quick.


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## spicmart (Mar 7, 2019)

Shortround6 said:


> Am I missing something??
> 
> to have _greater_ exhaust thrust you have to have one of two things (or a bit of both) more mass per minute flowing through the engine, that is fuel, air and whatever additives you are using (like water/alcohol or higher pressure exhaust leaving the cylinder. Actually that is not quite right, you need higher pressure (higher velocity) exhaust gas leaving the exhaust outlets/nozzles. But on a V-12 with short nozzles there probably isn't a lot difference unless somebody screwed things up.
> 
> ...



I don't know much about how much such thrust is generated. Just saw it stated in Manfred Griehl's book about the Fw 190D/Ta 152.


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## spicmart (Mar 7, 2019)

Snowygrouch said:


> *DB603N =* 3200rpm
> 2800PS @2.1ata manifold pressure using B4+ MW50
> 3000PS @2.5ata manifold pressure using C3 + MW50
> 
> ...



Do you have figures for the Jumo 213S, special low altitude engine? I just once saw a figure in kW but cannot recall it.


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## spicmart (May 24, 2020)

tomo pauk said:


> 12 mph was certainly not a monumental increase, but it shows that improvement in streamlinign counts. The Bf 109K4 was still saddled with 3 radiators, the ram air intake is still 'outside' of airframe, the 2R1 wing profile was no longer competitive even if it was thin on the 109s. The 441 mph probably represented the best case scenario indeed.
> There is a number of charts and tables for the K4 on the 'net, how good/bad (= based on the tests or manufacturers estimate) they are really is anyone's guess I suppose. 441 mph figure is from LW data sheet.



Can you tell exactly why the 2R1 wing profile was not competitive any more?


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## swampyankee (May 24, 2020)

spicmart said:


> Can you tell exactly why the 2R1 wing profile was not competitive any more?



How many aircraft used it? Other than Messerschmitt (and Bf109 clones), it seems to be approximately no one. This is usually a sign that an airfoil or airfoil family is not competitive or is poorly characterized. This can happen even with modern airfoils, like the Liebeck airfoils, which have a reputation for very poor off-design characteristics and are not widely used.

I’ve not been able to find much data on the 2R1and 2R2 series, but that may just be because NASA hasn’t gotten around to scanning the relevant reports from the NACA (yes, Messerschmitt used NACA airfoils) reports of the 1920s or very early 1930s, when the airfoil was designed.

After digging into Dave Lednicers "The Incomplete Guide to Airfoil Usage" (The Incomplete Guide to Airfoil Usage), I've found these aircraft that used the 2R1 airfoil. The only US aircraft is the Howard DGA. There was a 2R, a 2R1, and a 2R2 series; none were widely used. 


Root Airfoils
'NACA 2R1 14.2
 'Avia CS 199',
 'Avia CS 99',
 'Avia S 199',
 'Avia S 99',
 'Hispano HA-1109 Buchan',
 'Hispano HA-1110',
 'Hispano HA-1112 Buchan',
 'Messerschmitt Bf 109B',
 'Messerschmitt Bf 109C',
 'Messerschmitt Bf 109D Dora',
 'Messerschmitt Bf 109E Emil',
 'Messerschmitt Bf 109F Fredrich',
 'Messerschmitt Bf 109G Gustav',
 'Messerschmitt Bf 109K',
 'Messerschmitt Me 155B'

 

 'NACA 2R1 16'
 'Kawasaki Ki-100',
 'Kawasaki Ki-61 Hien',
 'Kawasaki Ki-88',
 'Messerschmitt Me 209V1


 'NACA 2R1 16.5'
 'Kawasaki KAL-2' 

 'NACA 2R1 18.5'
 'Messerschmitt Bf 110',
 'Messerschmitt Bf 161',
 'Messerschmitt Bf 162



 'NACA 2R1 19'
 'Messerschmitt Me 321 Gigant',
 'Messerschmitt Me 323 Gigant' ],


 'NACA 2R2 12' => [
 'Howard DGA-11',
 'Howard DGA-12',
 'Howard DGA-15',
 'Howard DGA-8',
 'Howard DGA-9'


Tip Airfoils
 NACA 2R1 10
Messerschmitt Me 321 Gigant,
Messerschmitt Me 323 Gigant

NACA 2R1 11
Messerschmitt Bf 109B,
Messerschmitt Bf 109C,
Messerschmitt Bf 109D Dora,
Messerschmitt Bf 109E Emil,
Messerschmitt Bf 110,
Messerschmitt Bf 161,
Messerschmitt Bf 162

NACA 2R1 11.35
Avia CS 199,
Avia CS 99,
Avia S 199,
Avia S 99,
Hispano HA-1109 Buchan,
Hispano HA-1110,
Hispano HA-1112 Buchan,
Messerschmitt Bf 109F Fredrich,
Messerschmitt Bf 109G Gustav,
Messerschmitt Bf 109K,
Messerschmitt Me 155B

NACA 2R12
CVV 7 Pinocchio

NACA 2R2 12
Howard DGA-11,
Howard DGA-12,
Howard DGA-15,
Howard DGA-8,
Howard DGA-9

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## tomo pauk (May 24, 2020)

spicmart said:


> Can you tell exactly why the 2R1 wing profile was not competitive any more?



Without going in circumstantial evidence at all, here is how the Germans determined the profile drag coefficient (at lift coefficient of 0.2) of wings of following A/C:
Bf 109: 0.0101
Fw 190: 0.0089
Mustang: 0.0072

(note that Bf 109 have had the thinnest wing of the listed fighters, the Mustang was with thickest - both in % and in centimeters)
The data is noted at "Vee's for victory" book, pg. 338, credited as 'H.H. Arnold Manuscript, Roll 194, Von Karman Report, Library of Congress'.

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## swampyankee (May 24, 2020)

spicmart said:


> So the airfoils of a lot of WW2 fighers were obsolete/not competitive at the end? Afaik as the Me 109, Fw 190, F4U Corsair, F6F Hellcat, F7F Tigercat, F8F Bearcat et al are concerned.



"Obsolete/non competitive" are excessively harsh; airfoil selection is just one factor in an aircraft's overall performance. Many people here seem to overvalue the airfoil, itself, as a determinant of the aircraft's performance (and some people who should know better, such as Riblett, condemn an airfoil for little valid reason). Of course, since the 1970s, all of the airframe manufacturers will use bespoke airfoils, designed with various 3D progams, some of which will even give valid predictions of behavior post-stall and unsteady behavior. Before this time, airfoils were usually picked out of a catalogue, such as Abbot and von Doenhoff's.

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## spicmart (May 24, 2020)

One wonders what the world record plane Me 209 V1 could have reached with a better airfoil.
Astonishing that the late design Me 155 used the 2R1 while the Me 210/410, a way earlier design, does not.
The Me 155 was developed out of the Me 109 but still they should have made the effort for a better airfoil.




swampyankee said:


> How many aircraft used it? Other than Messerschmitt (and Bf109 clones), it seems to be approximately no one. This is usually a sign that an airfoil or airfoil family is not competitive or is poorly characterized. This can happen even with modern airfoils, like the Liebeck airfoils, which have a reputation for very poor off-design characteristics and are not widely used.
> 
> I’ve not been able to find much data on the 2R1and 2R2 series, but that may just be because NASA hasn’t gotten around to scanning the relevant reports from the NACA (yes, Messerschmitt used NACA airfoils).





swampyankee said:


> How many aircraft used it? Other than Messerschmitt (and Bf109 clones), it seems to be approximately no one. This is usually a sign that an airfoil or airfoil family is not competitive or is poorly characterized. This can happen even with modern airfoils, like the Liebeck airfoils, which have a reputation for very poor off-design characteristics and are not widely used.
> 
> I’ve not been able to find much data on the 2R1and 2R2 series, but that may just be because NASA hasn’t gotten around to scanning the relevant reports from the NACA (yes, Messerschmitt used NACA airfoils).
> 
> ...


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## spicmart (May 24, 2020)

Do you have drag coefficients of the Fw 190D, Spitfire and Tempest (and maybe of Russian and Japanese planes)?


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## mad_max (May 24, 2020)

spicmart said:


> Do you have drag coefficients of the Fw 190D, Spitfire and Tempest (and maybe of Russian and Japanese planes)?



This article has plenty of numbers for folks to see. Page 32-33 spit, tempest, 190A-3 and others.

drive.google.com/open?id=1RzSw6SPTOzapjbZza78-fgKdsELrqW-n

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## pbehn (May 24, 2020)

spicmart said:


> So the airfoils of a lot of WW2 fighers were obsolete/not competitive at the end? Afaik as the Me 109, Fw 190, F4U Corsair, F6F Hellcat, F7F Tigercat, F8F Bearcat et al are concerned.


An aerofoil is chosen from what is known at the time for the use the plane is intended for. The Bf109 was designed for a short range fighter with a 650BHP engine at the start. Research into laminar flow showed that a wing could be thicker and have less drag in a certain speed range. The P-51D was also obsolete in terms of airfoil technology when introduced, Jets were in service with the USA , Germany and UK the speed of military combat had just jumped by 100MPH and transonic /supersonic performance was the new-new thing.

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## tomo pauk (May 25, 2020)

spicmart said:


> Do you have drag coefficients of the Fw 190D, Spitfire and Tempest (and maybe of Russian and Japanese planes)?



For the Fw 190/Ta 152 - this table, although it needs come math to come to the Cd0 (Cw0 in German). 
Namely, take the equivalent flat plate for max speed (that is 0.485 m^2 for the Fw 190A-8 and A-9), and divide it with wing area (18.3 m^2 for the two) = 0.0265. For the Fw 190D-9: 0.444/18.3= 0.02426.

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## spicmart (Jun 1, 2020)

tomo pauk said:


> For the Fw 190/Ta 152 - this table, although it needs come math to come to the Cd0 (Cw0 in German).
> Namely, take the equivalent flat plate for max speed (that is 0.485 m^2 for the Fw 190A-8 and A-9), and divide it with wing area (18.3 m^2 for the two) = 0.0265. For the Fw 190D-9: 0.444/18.3= 0.02426.



I do not know much about the differences but the it seems not that much of it between the Anton and the Dora. I would have expected more drag advantage for the Dora.


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## tomo pauk (Jun 1, 2020)

Having 10% more drag (A-8 vs D-9) is big - that big difference in drag will net you far greater speed difference than, for example, a 10% less power or thrust.
Other 'ingredients' that made D-9 faster than A-8 were power at altitude (100+ HP at 5.7 km without ram; more with ram), a bit more exhaust thrust (150 kg vs. 120kg, all max figures for 'Notleistung'), and a better ram air intake.

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## Snowygrouch (Jun 1, 2020)

I would like to point out to nobody in particular, just as an interesting aside - that I think its not wise to expend too much effort
on looking at top speeds of late model German fighters. They were so badly assembled, that it was reckoned that
a typical fighter made in the "Jäegerstab" era (basically early 1944 onwards) was up to 40km/h under its "design speed"
due to appauling build standards of both airframes and engines. In interrogations of leading German aviation personalities in 1945, they stated that
this was the main reason for the very late acceptance of +1.98 ata (and even above) on the DB engine, even though the
engines were not really cut out for it, because the terrible build standard meant that the planes were basically worthless
with the factory spec engine power, and were not even as fast as the previous versions.

You can of course compare orginal factory tests with resonable confidence, as the first prototypes probably did just about perform
as expected, but looking any any data from captured test-flights, or pilots stories and combat reports is likely to bear virtually
no resembance to the actual potential of the airframes under "normal" circumstances.

In addition huge numbers were running de-rated engines for B4 even if they were specified as C3 only engines (i.e. lowered boost).

The above is all in the British Air Intelligence A.I.2(g) files in Kew, London.

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## Koopernic (Jun 1, 2020)

For an Me 109GG the following speed improvments were possible compared to an standard aircraft operating a 1.3 ata boost at 0 meters altitude at around 483km/h

Streamlined cowling to smooth over MG131 bulges *483km/h-> 489km/h +6 km/h 1.24% (Test Carried out on a G6 with MG131 gun bulges)*
Fully Retractable Tail wheel..........................................…...…...*494km/h-> 506km/h* *+12km/h 2.37% (Test Carried out on a G1 without bulges)*
Fully covered wheels*..........................................………..506km/h-> 516km/h +10km/h 1.97% (Test Carried out on a G1 without bulges)
Percentage......................................................................................................…...........Total 5.58%*

The effect on a 397mph Me 109G6 at 1.42 ata is 397 mph x 1.0558 = *419.15 mph.*
Kurfürst - Influence of the shape the engine cowling on the level speed of the Me 109 G and
Kurfürst - Leistungzusammenstellung Me 109 G. (no English version so)

It should be noted that the P-51D had all these features : retractable tail wheel, fully covered wheels and of course no gun bulges. With fairly minor modifications that Me 109G6 could have been 22mph 35km/faster but production priorates were put ahead of quality and Luftwaffe pilots had to suffer.

The lack of a high altitude supercharger explains the rest of the speed gap. When the Me 109K4 came into service it had all of these features plus and enlarged supercharger and the speed was the same at around 20,000ft-25000ft. The P-51 was superior at sea level.

The P-51 Laminar flow wing was superior to the Me 109's but this manifested itself only in the thick air of low altitude where the lower parasitic drag of the P-51 was unbeatable. The laminar flow wing was only slightly more laminar and this was not a big advantage but it had 2 big advantages: 1 It had a much higher mach limit which meant that the rise of compressibility or shock wave drag was less at the speed the Mustang operated which was Mach 0.55 (at sea level) to Mach 0.66 (at 30,000ft), it was this rather than laminar flow that made the mustang more efficient. it also helped stop the ailerons from locking up from compressibility and helped the P-51 have a high roll rate. 2 The other factor was that the wing was much thicker which allowed space for the fuel which gave the range the P-51 was famous for. This also allowed a stiffer wing.

The Germans understood laminar flow technology and 3 aircraft were planed with laminar flow wings: the Me 309 (all their own work), the Blohm and Voss BV.155 and a planed improved version of the Dornier Do 335. The work on the Me 309 was all their own. The Japanese also introduced several laminar flow wing aircraft.

The Hawker Tempest had laminar flow wings, the thickest point was a little further forward than the P-51 and the wing cross section of the Tempest seems the same as the Me 262 to me.

The follow on of the Me 109K4 was the Me 109K6 which incorporated two MK108 30mm integrated wholly inside the wings. I suspect this would allow an elimination of the cowling guns or at least a return to rifle calibre machine guns. The Me 109K14 had a two stage supercharger (without intercooling but with water injection) and was expected to reach 457mph.

So apart from range the Me 109 remained theoretically competitive. It was clear it was on its way out. Yes the Mustang (and Tempest) was superior but remember the same cant be said of other allied fighters such as P-47, P-38 (superior high altitude performance due to turbo-superchargers) nor the Typhoon or Spitfire or Hurricane or P-40 or P-39.


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## Koopernic (Jun 1, 2020)

spicmart said:


> I do not know much about the differences but the it seems not that much of it between the Anton and the Dora. I would have expected more drag advantage for the Dora.



It's about a 9.2% lower drag for the Dora which equates to about 3% speed advantage using a cube root law . That's about 12mph from a 408mph base. The BMW801 and Jumo 213A were operating at about the same power levels at this time (2000-2050 for the BMW and 2100 for the Jumo ) and so the air mass flow was about the same but the Jumo was operating at both higher RPM and higher boost levels due to its lower displacement and I suspect this gave higher jet thrust.


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## mad_max (Jun 2, 2020)

The "laminar wing profile" didn't give it a higher mach limit, but what it did do was it provided less or no nose tuck at high speed. At high alt. (30,000+ ft) the 109's wing was bearly able to handle the thin air without stalling in maneuvers I've heard, which makes sense to me.


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## spicmart (Jun 6, 2020)

I was always thinking thet the airfoil of the Fw 190 was draggier than the Me 109's. But looks can be deceiving.


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## swampyankee (Jun 6, 2020)

mad_max said:


> The "laminar wing profile" didn't give it a higher mach limit, but what it did do was it provided less or no nose tuck at high speed. At high alt. (30,000+ ft) the 109's wing was bearly able to handle the thin air without stalling in maneuvers I've heard, which makes sense to me.



Because of the 6-series airfoils' pressure distribution, they tended to have a high critical Mach number; this was a consequence of the pressure distribution used to maximize the region of laminar flow. The 16-series airfoils were designed for regions of barely supersonic flow (see http://web.stanford.edu/~cantwell/AA200_Course_Material/The NACA airfoil series.pdf), but was little used except on propellers. The 6-series airfoils also tended to have quite limited regions of low drag, usually only ±0.1 from the design lift coefficient. Airfoils with better off-design characteristics would have to wait for a few decades.


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## mad_max (Jun 12, 2020)




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## mad_max (Jun 12, 2020)



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