# Bf109F vs P-38F



## ricardo (Aug 16, 2007)

Overall... which one is better dogfighting?


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## ccheese (Aug 16, 2007)

This is what I found on the F-model:

"If the P38F was the plane the US Army evaluated during the early stages of the US Air War against Germany, then it is no wonder that it was deemed as an inferior aircraft. Climb performance was poor, especially compared to the Messerschmitt 109, diving performance was good, as long as you didn't exceed 375mph IAS. Acceleration was ok for the time, but still inferior to many designs (most notably both of German's fighters at the time, the Bf109 and Fw190). Roll rate was reasonable under 300mph, especially for such a big plane.

The biggest problem with the P38F is it's high speed handling. The P38F's handling at speeds higher than 375mph made a Bf109F seem like a Focke-Wulf. The roll rate was almost nonexistent at these speeds due to excessive stick forces (thus the need for the power-assisted ailerons of the P38L). Elevator control did not feel like the stick was in cement like the Bf109 did, but the turbulence and lift problems at these speeds meant that elevator deflection did not do much (P38L's dive flaps solved this problem). The Germans learned real quick that the best defense against an attacking P38F was a split-s (which the P38F couldn't follow due to slow roll), and a dive (which the P38F couldn't follow for risk of becoming a lawn dart, or shedding it's tail at high speeds).

The P38F is also one of the poorest vertical fighters. Thus virtually any plane with a decent vertical maneuvering capability can yoyo the P38F to death, and overcome any turn disadvantage. The poor vertical performance and diving abilities make the P38F very difficult to energy fight in."

Not good against a bf-109. But, yet again, the P-38's (later models)
did well in the Pacific.

Charles


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## ricardo (Aug 16, 2007)

Thanks Ccheese. "Sweet and to the point". I like the P-38F design, as a fact I always preferred the early models of every airplane the USAAF threw to battle: P-51B, P-38F, P-47 Razorback, B-17F, F4U-1 Corsair Birdcage, P-40B.... but I was wondering how did the P-38 behave when they first saw action.


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## delcyros (Aug 18, 2007)

The P-38 did well in 1942 over North Africa and the central mediterranean. It had an excellent acceleration (better than contemporary US P-39 and P-40 models) and climb rate and reportedly handled well in those low and medium altitudes, where most of the fighting there took place. 
But the -109F, esspeccially the -F4 is as deadly while enjoing a much more difficult target size. It also featured excellent climb, speed and acceleration (the -109F4 probably had the best linear stand off acceleration of any ww2 plane except the Me-163 rocket interceptor).
On the other hand a P-38 is more difficult to take out than a -109...


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## Aussie1001 (Aug 18, 2007)

THe p38 was also dogged by engine trouble was it not ?
I've heard that the engine was prone to overheating and that the turbo-supercharger just made it worse...
Reguards 
Michael


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## FLYBOYJ (Aug 18, 2007)

The 109F was a better dogfighter. Why did you pick the P-38F? The P-38H was the first real combat capable P-38.


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## FLYBOYJ (Aug 18, 2007)

Aussie1001 said:


> THe p38 was also dogged by engine trouble was it not ?
> I've heard that the engine was prone to overheating and that the turbo-supercharger just made it worse...
> Reguards
> Michael



At altitude and in Europe. At middle altitudes and in the Pacific it did very well.


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## syscom3 (Aug 18, 2007)

The P38 wasnt even designed for dogfighting.

It was a bomber interceptor.


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## Aussie1001 (Aug 19, 2007)

Thanks flyboyJ....


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## DerAdlerIstGelandet (Aug 19, 2007)

Voted for the Bf 109F.

Reasons why:

Read FBJ and syscoms posts.


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## mkloby (Aug 19, 2007)

Ahhh Bf 109Fs are my favorite warbirds! Then they ruined it with the G!


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## Aussie1001 (Aug 19, 2007)

WHy apparantly the 109f was grossly undergunned.... that is what i've heard anyway, my favourite aeroplane is the hawker Tempest mk 5 series 2


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## DerAdlerIstGelandet (Aug 20, 2007)

Because with the added weight the Bf 109G started to lose the qualities that made the Bf 109 such a great aircraft.


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## SoD Stitch (Aug 20, 2007)

DerAdlerIstGelandet said:


> Because with the added weight the Bf 109G started to lose the qualities that made the Bf 109 such a great aircraft.



Yes, the Gustav had the DB605 engine, instead of the older DB601, which increased the horsepower of the Gustav over the Freidrich; however, this was more than offset by the increased armament and armor, hence the loss in performance.


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## DerAdlerIstGelandet (Aug 20, 2007)

Yeap. Dont take me wrong though, the Bf 109G was still a marvelous fighter and a match for any aircraft especially with a pilot who knew how to exploit its advantages.


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## drgondog (Aug 20, 2007)

DerAdlerIstGelandet said:


> Because with the added weight the Bf 109G started to lose the qualities that made the Bf 109 such a great aircraft.



I had the same vote for same reasons - the P-38L was a much better match against the G/K than the P-38F was against the 109F


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## DerAdlerIstGelandet (Aug 20, 2007)

I think the 109F was the best all around 109 ever built. It had great performance for its time, great maneuverability and at the time was probably the best fighter in the sky.

My fav 109 is the 109G however but that is for another discussion.


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## drgondog (Aug 20, 2007)

DerAdlerIstGelandet said:


> I think the 109F was the best all around 109 ever built. It had great performance for its time, great maneuverability and at the time was probably the best fighter in the sky.
> 
> My fav 109 is the 109G however but that is for another discussion.



Chris - I'm thinking you are thinking 1942 for 109F being best? and I'm saying to myself the 109F Fw190 and the Spit are hard to choose from, with the Fw190 getting nod over Spit V...

Regards,

Bill


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## SoD Stitch (Aug 20, 2007)

DerAdlerIstGelandet said:


> I think the 109F was the best all around 109 ever built. It had great performance for its time, great maneuverability and at the time was probably the best fighter in the sky.
> 
> My fav 109 is the 109G however but that is for another discussion.



My fave 109, also, Adler; probably the G-10 is my favorite, before they ruined it with the K-4. Decent performance, decent armament, and faster than a -190 in a straight line.


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## timshatz (Aug 20, 2007)

I've heard the Me109F was the most manuverable of the 109 Family while the P38F was the least of the P38 Family. Might feel different if it were the P38J vs 109G but for this one, my money is on the 109F.


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## pbfoot (Aug 20, 2007)

Just read about a impromptu test between a P38 and Spit and the Spit pilot said if they started out equal within 2 360's he would be on the 38's tail


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## DerAdlerIstGelandet (Aug 20, 2007)

drgondog said:


> Chris - I'm thinking you are thinking 1942 for 109F being best? and I'm saying to myself the 109F Fw190 and the Spit are hard to choose from, with the Fw190 getting nod over Spit V...
> 
> Regards,
> 
> Bill



Yes I am talking about when the 109F was at its hight.


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## Aussie1001 (Aug 20, 2007)

mmmm. would still pick the 109 over the p38 no matter what model of plane of either....


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## Kurfürst (Aug 21, 2007)

SoD Stitch said:


> My fave 109, also, Adler; probably the G-10 is my favorite, before they ruined it with the K-4. Decent performance, decent armament, and faster than a -190 in a straight line.



I don't quite see how it is possible, after all, the weight difference between the G-10 and K-4 was (unsurprisingly, given their similiarities in equipment) marginal, being around 70 kg, and in the case of the comparable armed G-10/U4 with the MK 108 cannon, about 20 kg.

The K-4 weighted a little less than the Spit IX, and was a bit more than 1000 lbs lighter than the XIV.

In fact the story of the 109F being such a shiny performer (though indeed it was) 'before the evil G-series begun to add weight' is rather bizarre when one considers that the difference in weight between 109F-2 and F-4 was greater than the difference in weight between the F-4 and G-2...


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## Konigstiger205 (Aug 21, 2007)

The K-4 was the last 109...it was the end of the war and the lack of proper materials put its mark on the K model.The 109F however was indeed a great plane and like Adler said probably the best from the 109 family.


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## chuter (Aug 21, 2007)

SoD Stitch said:


> My fave 109, also, Adler; probably the G-10 is my favorite, before they ruined it with the K-4. Decent performance, decent armament, and faster than a -190 in a straight line.



Odd. It's my understanding the K4 was developed, tested and standardized THEN the G10 was developed as a way to make additional K4's out of the never ending supply of wrecked G(various) components . . .


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## Kurfürst (Aug 21, 2007)

Indeed the G-10 was a 'bastard' aircraft, a G airframe with many internal components from the 109K (new generator, engine amongst others). It ensured that factories could make use of 109K components without re-tooling for a (somewhat) new airframe.


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## Thorlifter (Aug 21, 2007)

syscom3 said:


> The P38 wasnt even designed for dogfighting.
> 
> It was a bomber interceptor.



True, your really not comparing apples to apples. But, to answer your question, I vote for the 109.


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## SoD Stitch (Aug 21, 2007)

Kurfürst said:


> I don't quite see how it is possible, after all, the weight difference between the G-10 and K-4 was (unsurprisingly, given their similiarities in equipment) marginal, being around 70 kg, and in the case of the comparable armed G-10/U4 with the MK 108 cannon, about 20 kg.
> 
> The K-4 weighted a little less than the Spit IX, and was a bit more than 1000 lbs lighter than the XIV.
> 
> In fact the story of the 109F being such a shiny performer (though indeed it was) 'before the evil G-series begun to add weight' is rather bizarre when one considers that the difference in weight between 109F-2 and F-4 was greater than the difference in weight between the F-4 and G-2...



Kurfurst, you are quite right, I didn't do the research . . .

The K-4 was, actually, a bit faster than the G's due to it's increased power output (it had a bigger supercharger) and it's lighter construction. My main reason for disliking the K-4 was the decline in quality and extensive use of wood in it's construction.


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## ricardo (Aug 21, 2007)

Thanks to all for your replies. I chose the Bf109F against P-38F because they were fighting in the same theater (Africa) and in the same period (1942). I think this comparison makes sense.... now, if I make a comparison between a P-51H against a Bf109D... well.... obviously the P-51 comes out the winner, but it is not a valid comparison.


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## Aussie1001 (Aug 21, 2007)

meh good enough....


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## Soundbreaker Welch? (Aug 21, 2007)

That's a good point. In timewise, a P-38J wouldn't be fighting a BF 109F, but more likely a Bf 109G?


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## flojo (Aug 23, 2007)

I find these discussions about the lacking qualities of the 109G a little bit of a problem as the different g-subtypes differ so strongly. G2 was more similar to the F-models in my opinion than to the G6. And also a late G6(+MW50)/G14 or one of the types with AS or D engines with better high altitude chargers were quite different than an early 1943 G6.


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## superpumper (Aug 26, 2007)

I might be wrong but I think I read somewhere that the 109 could lose its wings in combat in very tight turns if one wasn't careful at least in the early models. Is this so?


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## trackend (Aug 26, 2007)

I,ll go for the 109f.
Not that this threads about it but I'd like to have seen what the 309 could have done slower but with two 30mm two 20mm and four 13mm pretty devastating


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## DerAdlerIstGelandet (Aug 26, 2007)

superpumper said:


> I might be wrong but I think I read somewhere that the 109 could lose its wings in combat in very tight turns if one wasn't careful at least in the early models. Is this so?



Early versions of the Bf 109F had problems with vibrations which could make the wing surface to break apart. This however was fixed very quickly.


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## mkloby (Aug 26, 2007)

DerAdlerIstGelandet said:


> Early versions of the Bf 109F had problems with vibrations which could make the wing surface to break apart. This however was fixed very quickly.



I believe I remember reading that at a certain RPM range the empennage (horizontal stab I believe) would suffer catastrophic failure due to sympathetic vibrations.


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## Glider (Aug 26, 2007)

mkloby said:


> I believe I remember reading that at a certain RPM range the empennage (horizontal stab I believe) would suffer catastrophic failure due to sympathetic vibrations.



I have heard this before on other threads, but on the thread about Gunther Rall, the following statement of his caught my eye.

_Anyway, I was chased by P-47. I knew exactly that in a dive P-47 is much faster than 109. And the P-47 has a much higher structural strength. They can go up to 1400 kilometers per hour. The 109, if you go to 1000, pull it up, you risk that the wings come off._

If Gunther was cautious of the wings coming off, then other less experienced pilots must have experienced a wing failure. This proves to me anyway that the problem was more widespread than just 109F vibrations


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## Kurfürst (Aug 30, 2007)

Any wing will fail after the dive limitations are exceeded, or if the ailerons are badly set up. The 109's 'problems' with wing failures were not any more pronounced than your avarage WW2 fighters. It happened, from time to time, the usual culprit was the pilot exceeding the Vne, badly set up ailrons or simply worn-out, old airframes. Usually the problem was not as much the lack of structural strenght, but that conditions could arise which grossly overloaded the wings. No WW2 fighter's wing was built to resist twisting movements, for example, you will find the NACA making such reports with regards of the _P-47 Thunderbolt. _

Certainly there were quite a few fighter types more notorious for these kind of troubles than the 109.


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## Konigstiger205 (Aug 30, 2007)

The 109 was not the most excellent fighter in WW2 but it did its job and in the hand o experienced pilots it proved a very deadly plane and the numbers in which was produced shows as much.


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## Glider (Aug 30, 2007)

Kurfürst said:


> Any wing will fail after the dive limitations are exceeded, or if the ailerons are badly set up. The 109's 'problems' with wing failures were not any more pronounced than your avarage WW2 fighters. It happened, from time to time, the usual culprit was the pilot exceeding the Vne, badly set up ailrons or simply worn-out, old airframes. Usually the problem was not as much the lack of structural strenght, but that conditions could arise which grossly overloaded the wings. No WW2 fighter's wing was built to resist twisting movements, for example, you will find the NACA making such reports with regards of the _P-47 Thunderbolt. _
> 
> Certainly there were quite a few fighter types more notorious for these kind of troubles than the 109.



I have never heard of this problem being mentioned on other fighter aircraft. 
Certainly I have never heard of an experienced pilot of a fighter be limited in his actions by the fear of such a wing failure.
I also find it hard to believe that such a top pilot would have badly set up ailrons or worn out airframes.
Can I ask you to name any examples of other aircraft with similar problems?

I also notice that on the JG26 web site the following phrase

_121 pilots were killed in aircraft accidents—wing or engine failure, bad weather, lack of fuel, takeoff and landing mishaps, air collisions, and the catch-all "loss of control"._

No one would deny that the other types of accidents are common to all airforces, but again, I have never seen wing failure mentioned in the context of a normal accident. Again have you any examples?

It would appear that it was more common on 109's and 190's.


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## drgondog (Aug 30, 2007)

Glider said:


> I have never heard of this problem being mentioned on other fighter aircraft.
> Certainly I have never heard of an experienced pilot of a fighter be limited in his actions by the fear of such a wing failure.
> I also find it hard to believe that such a top pilot would have badly set up ailrons or worn out airframes.
> Can I ask you to name any examples of other aircraft with similar problems?
> ...



Both the 51 and 47 experienced structural failures including wings (and tails) during dives. In the case of the 51 and 47 the tail failures were mostly (not all definitively) a result of yaw in the dive..

The 51B/C wing issue was 'mostly' solved with uplock kits to keep the wheel well door from spring loose as well as stiffer ammo doors which were believed (not conclusively) to 'flex', creating more local lift loads at that critical area.

The latter analysis was mored complicated because it wasn't conclusive that the issue was higher Center of Lift loads inboard or disruption of flow rendering horizontal stabilizer less effective causing nose down pitch (ala Me 262 'departing' at Mcr in a dive- ditto P-38) at very high speeds.

The D fixed (mostly) both of the wing problems and the H fixed (mostly) the high speed yaw problem. Both of these also had metal elevators.

Having said that, both the 51 and 47 had a stronger wing than a 109, maybe because they were both designed to carry pretty heavy wing armament and landing gear loads at mid-point of wing spar. 

That design and subsequent structural approach had a lot to do with the 109's issue in adding more and heavier armament Internal to wing..namely main gear close to fuselage and all armament internal to nose.


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## drgondog (Aug 30, 2007)

mkloby said:


> I believe I remember reading that at a certain RPM range the empennage (horizontal stab I believe) would suffer catastrophic failure due to sympathetic vibrations.



That's interesting.. Resonance and effects w/AeroElasticity were not very well understood sciences until the Comet started failing in the 50's.. I wonder what triggered Messerschmitt to solve the problem?

I'm also wondering, even more, what the natural frequency of the 109 wing might have been as the RPM of the engine would be one of the prime 'input factors'.

You would have to make some serious changes to airframe structure of the wing to change the natural frequency - or change the RPM dramatically (which didn't happen).

Jes ponderin' what all that might be about...I just don't recall ever seeing anything regarding structural failure due to either resonance or fatigue until post war for an airplane. 

Von Karman proved that alternating vortices shed in such a way from the cables suspending the bridge (Washington State??1930's?? CRS) that at a specific wind speed and loading on the bridge, that the frequency of the vibations of the cables resonanated with the natural frequency of the bridge and it 'departed' - does anyone know of a specific aircraft study on this before 1950's?


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## FLYBOYJ (Aug 30, 2007)

Even today certain aircraft cannot be constantly operated in some RPM ranges - I know it's just bugsmashers but 300 HP Piper Cherokees should avoid continuous operation between 1650 and 1900 RPM above 24" MP and 150 hp Cessna 150s have to avoid RPMs bewteen 1850 and 2250 RPM in a desent...


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## Kurfürst (Aug 30, 2007)

Glider said:


> I have never heard of this problem being mentioned on other fighter aircraft.
> Certainly I have never heard of an experienced pilot of a fighter be limited in his actions by the fear of such a wing failure.
> I also find it hard to believe that such a top pilot would have badly set up ailrons or worn out airframes.
> Can I ask you to name any examples of other aircraft with similar problems?



Oh, basically the more you dug into the history of an aircraft, the more you read of troubles, failures and the like. More skeletons of in the cupboard. Development of an aircraft is basically fixing these problems. I recommend you trying to get some really through books on aircraft development, like Spitfire : The History. You'll find plenty of examples of the like in it.

Take a look at this one :

http://i38.photobucket.com/albums/e133/Kurfurst/spits2.jpg

Though I could list you certainlymany more examples than you'd consider friendly  

There are many others, as I said, structural failures due to various reasons were rather not uncommon for WW2 aircraft. And, usually it was not much of a matter of structural strenght but aerodynamics. Ailerons play a huge role in it, just look up 'flutter' effects. There was little in the hands of 1940s engineers to forecast those effects they knew little about in the first place.. so, accidents happened, wings failed, and they tried to fix that by trial and error methods.




> I also notice that on the JG26 web site the following phrase
> 
> _121 pilots were killed in aircraft accidents—wing or engine failure, bad weather, lack of fuel, takeoff and landing mishaps, air collisions, and the catch-all "loss of control"._



It seems to be a total for all causes without any way to know what was the _breakdown._ (getit?)



> It would appear that it was more common on 109's and 190's.



I don't think we have sufficient, comparative evidence to make a statement like that in good faith.


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## Glider (Aug 30, 2007)

Thanks everyone for the details, appreciate it.


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## Soren (Aug 30, 2007)

> Having said that, both the 51 and 47 had a stronger wing than a 109, maybe because they were both designed to carry pretty heavy wing armament and landing gear loads at mid-point of wing spar.



Thats a very false statement Bill.

The Bf-109 featured one of the strongest wings of any WW2 fighter, the wing being capable of withstanding over 13 G's. By comparison the P-51's wing would start seperating itself from the airframe at around 7-8 G's. And the P-51's wing wasn't designed to carry heavier loads either, the Bf-109 could carry the same loads without any problems.

The myth that the 109 featured a flimsy wing derives from the Bf-108's tendency to loose a wing in high G maneuvers - the 109's wing however was an entirely different construction.


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## Glider (Aug 30, 2007)

Soren said:


> Thats a very false statement Bill.
> 
> The Bf-109 featured one of the strongest wings of any WW2 fighter, the wing being capable of withstanding over 13 G's. By comparison the P-51's wing would start seperating itself from the airframe at around 7-8 G's. And the P-51's wing wasn't designed to carry heavier loads either, the Bf-109 could carry the same loads without any problems.
> 
> The myth that the 109 featured a flimsy wing derives from the Bf-108's tendency to loose a wing in high G maneuvers - the 109's wing however was an entirely different construction.



If this is the case, then why the entry on the JG26 site treating a wing failure as being a normal type of accident, plus of course, the concern shown by Gunther Rall who firmly believed that he would lose his wing before the P47?


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## Soren (Aug 30, 2007)

Always Günther Rall 

Rall never dared push the 109 to the limit after his near fatal accident in an Emil early in his carreer, being of the firm believe that as soon as the slats deployed he would stall, you can see him mention this on many occasions. As to the JG26 site refering to it as being normal, well worn out airframes could did break apart, it was normal, the same happened to most other fighters of WW2 - the P-51 loosing its wing completely a good number of times. 

Bf-109 pilots could dive pull out of a high speed dive quicker and more safely than a P-51 pilot could, this happening on numerous occasions.

*Robert C.Curtis, American P-51 pilot: *
_"My flight chased 12 109s south of Vienna. They climbed and we followed, unable to close on them. At 38,000 feet I fired a long burst at one of them from at least a 1000 yards, and saw some strikes. It rolled over and dived and I followed but soon reached compressibility with severe buffeting of the tail and loss of elevator control. I slowed my plane and regained control, but the 109 got away. 
On two other occasions ME 109s got away from me because the P 51d could not stay with them in a high-speed dive. At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. "_

*Thomas L. Hayes, Jr., American P-51 ace, 357th Fighter Group, 8 1/2 victories:*
_"Thomas L. Hayes, Jr. recalled diving after a fleeing Me-109G until both aircraft neared the sound barrier and their controls locked. Both pilots took measures to slow down, but to Hayes' astonishment, the Me-109 was the first to pull out of its dive. As he belatedly regained control of his Mustang, Hayes was grateful that the German pilot chose to quit while he was ahead and fly home instead of taking advantage of Hayes' momentary helplessness. Hayes also stated that while he saw several Fw-190s stall and even crash during dogfights, he never saw an Me-109 go out of control."_


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## drgondog (Aug 30, 2007)

Soren said:


> Thats a very false statement Bill.
> 
> The Bf-109 featured one of the strongest wings of any WW2 fighter, the wing being capable of withstanding over 13 G's. By comparison the P-51's wing would start seperating itself from the airframe at around 7-8 G's. And the P-51's wing wasn't designed to carry heavier loads either, the Bf-109 could carry the same loads without any problems.
> 
> ...



Well maybe the 'myth' lives on when maybe the greatest German fighter pilot (with Hartmann) thinks his 109 is much more fragile in a dive that the P-47 and didn't experience any challenges in that area with the P-51s He Evaluated at Rosarius Zircus?

*Facts Soren are so pesky for you. 

Source please for "13 G"? Ditto for "7g" limits for 51. Facts not fantasy

Where do you get this 'stuff' and why would you think a G Suit was so desirable in combat with 51 pilots if 7g was a structural "do not exceed" limitation? 

Franz Nowarra speaks of the 109F wing being a complete re-design from the E, and Messerschmitt was forced to remove the FF inboard 20mm cannon. On page 118 of "Aircraft and Legend-Messerschmitt Bf 109" he speaks of 'excessive G forces in turns or coming out of dives were inadvisable - the 109F would sometimes ' clap hands' and break off"

The first G wing was strengthened somewhat but the wheel design, by definition forward of the main spar, meant that the 109 G series still had a spar around 0 % chord, increasing torsion aft of the center of lift which was at ~27%. I don't know what kind of engineering education you have but it is NOT a good idea to have your Center of Lift and Moment ~15% chord length away from your main (and only) Spar - helluva built in torsion issue even with the tosionally stiff leading edge he designed to get close to a 'torsion box'.

But he was faced with the idea of keeping the 109 very agile w/o adding more structure to wings, increase weight, lower roll weight and increase wing loading for no real benefit other than more firepower.

The first 109F's also apparently had a resonance issue with horizontal stabilizer due to removal of trusses from E model. They solved the problem This issue was Fixed, but an illustration of challenges encountered with F and G models as more HP and weight added.

Willy recognized the flaw and moved the landing gear aft for the 309 model for both structure and stability with nose gear - but the 209 still had wing cannon mounted underneath and the spar at 50%, he only solved the internal gun mount and ammo in wing with K series wing (IIRC) . 

But you aren't getting 13 G pullouts with a wing designed that way - not to mention not strong enough to put 20mm cannon and ammo internal to wing outboard of the landing gear..

Explain why Rall thought the 109 was much more fragile in a dive... but you think differently

Explain why you think 20mm and 30mm guns were stored in a Gondola instead of internally on the G's

Last , explain where you pulled the "7 G" jewel from in reference to structural limit? The 51 managed to chase and hunt down 109s in near terminal dives with no real problem*

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## FLYBOYJ (Aug 30, 2007)

Soren said:


> _"At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 it often was exceeded, if you wanted to keep up with those enemy planes. _"


What model P-51? The C or the B to C conversion did not have the dorsal in front of the vertical stabilizer which caused the aircraft to be unstable at high speeds


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## FLYBOYJ (Aug 30, 2007)

Soren said:


> Thats a very false statement Bill.
> 
> The Bf-109 featured one of the strongest wings of any WW2 fighter, the wing being capable of withstanding over 13 G's. By comparison the P-51's wing would start seperating itself from the airframe at around 7-8 G's. And the P-51's wing wasn't designed to carry heavier loads either, the Bf-109 could carry the same loads without any problems.


I'd like to see the stress tests for that...


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## drgondog (Aug 30, 2007)

Soren said:


> Always Günther Rall
> 
> Rall never dared push the 109 to the limit after his near fatal accident in an Emil early in his carreer, being of the firm believe that as soon as the slats deployed he would stall, you can see him mention this on many occasions.
> 
> ...



I guess I'll have to dig up some where others experienced outdiving a 109 or seeing it going out of control... they won't e hard to find.

about 10 minutes of effort - here you go
http://www.spitfireperformance.com/mustang/combat-reports/4-godfrey-1may44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/4-fiedler-8april44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/4-fiedler-8april44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/355-hovde-19july44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/355-marshall-11sept44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/355-elder-16aug44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/355-brown-29april44.jpg

This took about 30 seconds to find - what does this prove? that a 109 can always outdive a 51 and pull 13 g's in the process? C'mon Soren.


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## pbfoot (Aug 30, 2007)

I'm no engineer and I'm not all that swift so I asked , since I get closer on to the 109 on regular basis then most of you guys . I;ve asked those that have flown and repaired and they chuckled at 13gs


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## Brain32 (Aug 31, 2007)

> about 10 minutes of effort - here you go
> http://www.spitfireperformance.com/m...rey-1may44.jpg
> 
> http://www.spitfireperformance.com/m...r-8april44.jpg
> ...




I'm not claiming Me109 kicks P51 in a dive, but those reports really do not support your claims, in most of theese starting altitude is not mentioned, speed at any moment is again not mentioned, and no 109 in those reports lost control before it got shot.
Maybe 10minutes was not enough after all 

Oh and BTW report 2 and 3 are same thing...


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## Kurfürst (Aug 31, 2007)

pbfoot said:


> I'm no engineer and I'm not all that swift so I asked , since I get closer on to the 109 on regular basis then most of you guys . I;ve asked those that have flown and repaired and they chuckled at 13gs



That may be, but even pre-war, rather lightly built proto Bf 109s had a documented break-point of 10,8 G, and I recall some intrumented test from mid-war which achieved somewhere around 13 or 14G without breakage. IIRC that was on a Bf 109G.

13 G doesn't sound at all unreasonable as an ultimate load factor for a well built WW2 SE fighter. Max 12 Gs were quite typical. 'Safe' limits, with lots of safety built in was around 6-7 G for the aiframe. The safe limit was usually ~6.5 G for mid-war 109s, when fully loaded.


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## FLYBOYJ (Aug 31, 2007)

Kurfürst said:


> 13 G doesn't sound at all unreasonable as an ultimate load factor for a well built WW2 SE fighter. Max 12 Gs were quite typical. 'Safe' limits, with lots of safety built in was around 6-7 G for the aiframe. The safe limit was usually ~6.5 G for mid-war 109s, when fully loaded.


Agree, and that would include most WW2 fighters.


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## drgondog (Aug 31, 2007)

Kurfürst said:


> That may be, but even pre-war, rather lightly built proto Bf 109s had a documented break-point of 10,8 G, and I recall some intrumented test from mid-war which achieved somewhere around 13 or 14G without breakage. IIRC that was on a Bf 109G.
> 
> 13 G doesn't sound at all unreasonable as an ultimate load factor for a well built WW2 SE fighter. Max 12 Gs were quite typical. 'Safe' limits, with lots of safety built in was around 6-7 G for the aiframe. The safe limit was usually ~6.5 G for mid-war 109s, when fully loaded.



Actually I agree that an ultimate load factor would be 1.5 over design limit based on conventional design criteria.. I would also believe 10.8 G for a 109 as a documented stress to ultimate test. I would be very interested in seeing 13 G but even believe it 'possible' but would still like to see the tests.

The 51 passed Navy Carrier landing tests for 'drop' landing in WWII but I am unsure what that standard was in 1944...the Drop Tests and arresting gear loads were always the limit loads to wing and fuselage longeron/beam design criteria for navy fighters.. but that is a different case altogether for lift loads at high speeds (as in dive) and lift loads in a high G turn.

The 51 did have a design issue with the main wheel cover, 'unlatching' in a dive cause the landing gear to pop out resulting in catastrophic failure - but that had nothing to do with a 'fantasy 7 g' limit proposed by Soren... and it was fixed with uplock kits in the B model, permanent design feature in D and H (and P-82)

The 51 had the main spar at center of Lift Kurfurst, and it had a secondary torsion box created by the spar at the flap interface, undisturbed by wheel well or anything else. out to center of lift. 

The 109 wing had the main spar aft of Center of lift and it's 'torsion box' created by the flap spar was certainly useful but the one created by leading edge spar was essentially useless for positive vertical bending loads - because of the big 'ol wheel well cutting away all the shear web capability - at the worst possible spot. Meaning the center of the lift, forward of the Main spar was taken out in torsion in contrast to simple bending.

I didn't design the 109 so I don't know the final rationale but it is clear that it has one huge design flaw - the landing gear in context of difficulty in landing- was designed that way to minimize spar size and wing weight. 

The gear attach is close to the fuselage so that it could take much of the positive langing loads at the root/fuse area rather than outboard spar.

The 51 and 47 on the other hand had to be designed to carry a LOT of weight out around midpoint of spar (landing loads w/bombs or ferry tanks, and full internal fuel plus guns and ammo) - by necessity a deeper and more fundamentally heavy spar.

So Soren blurts out nonsense when he proclaims that a 109 has 2x design limit load capability over a 51.

Look at all the foolishness Messerschmitt had to go to just to increase firepower - or range. He didn't put internal wing cannon in either the F or the G wings, nor did he hang fuel tanks or bombs from the wing.. there was a reason for that.

If Heinz Nowarra's accounts of the early 109F failing in high G turns is incorrect - I would like to see the rebuttal to improve my own understanding.

Regards,

Bill


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## drgondog (Aug 31, 2007)

Brain32 said:


> I'm not claiming Me109 kicks P51 in a dive, but those reports really do not support your claims, in most of theese starting altitude is not mentioned, speed at any moment is again not mentioned, and no 109 in those reports lost control before it got shot.
> Maybe 10minutes was not enough after all
> 
> Oh and BTW report 2 and 3 are same thing...



Most of the starting altitudes are at bomber escort altitude for the above (and below) encounters. My father's encounter (355 Marshall 9-11)states specifically 23,000 feet and catch up at 11,000 with the 109 starting with a lead... no compressibility in his example - just chase, catch, shoot

http://www.spitfireperformance.com/mustang/combat-reports/4-hofer-8april44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/4-snell-29may44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/4-werner-6oct44.jpg

http://www.spitfireperformance.com/mustang/combat-reports/55-konantz-11sept44.jpg

This took about 30 seconds.. we have chases, we have compressibility, we have 109s losing control and/or disintegrating in the dive... what do we make of that? Most of the dives start at bomber escort altitudes, all the 109s had a head start.

The only reason I even bothered is that Soren seems to think his extracts from encounter reports are conclusive evidence that a 109 outdives a Mustang or that Mustangs chasing 109s are lucky to survive a catastrophic failure - be your own judge. 

Regards,

Bill


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## Soren (Sep 1, 2007)

LoL, you're a joke Bill ! 

7 G was rarely reached by fighters in combat during WWII, and the G-suits available back just barely made 5.5 G sustainable! I doubt the Franks G-suit helped pilots sustain anymore G's than the designed inclined seating position raised foot rests did for German pilots.

You want facts, no problem:

*P-51 Mustang, 7-8G Maximum load limit at a mere 8,000 pounds ! *




Want to try and critize or explain away the above please ????

Also please provide evidence to support your little theory that the P-51's wings were designed to carry more equipment than the Bf-109's - like you say, facts facts facts please Bill !!!

Oh and about Rall, who apparently is the best LW pilot of WW2 in your opinion, well regarding the characteristics of the P-51 I'd rather trust actual experienced P-51 pilots. 

AND, where do you get the stupid idea that the 109's in the accounts I presented were given any meaningful head start ?? Just because the 109 was 1,000 meters straight ahead in level flight doesn't mean that when it dives it gets a head start - unless you want to claim that it took the P-51 pilot more than 5 seconds to react to the 109's dive ???

Also, like usual Bill, you put words into peoples mouths in order to create a deviating argument: For example where did I ever claim that the Bf-109 out-dives the P-51 ??! All I said was it was safer for 109 pilots to enter high speed dives as their a/c could take higher G forces and were quicker to regain control once compressibility was reached, all of which is true! The Bf-109 featured variable pitch horizontal stabilizers, the P-51 didnt, hence why the Bf-109 is able to regain control much quicker from a high speed dive than the P-51. I am no stranger to the fact that the P-51 accellerates quicker in a dive than the 109, but its just not as safe for a P-51 as it is for a 109.

Anyway keep on the backpaddling Bill


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## Soren (Sep 1, 2007)

pbfoot said:


> I'm no engineer and I'm not all that swift so I asked , since I get closer on to the 109 on regular basis then most of you guys . I;ve asked those that have flown and repaired and they chuckled at 13gs



No wonder they chuckled cause at 13 G the wing is about the only thing on the a/c that stays attached (Note I'm not saying the wing won't take damage) 

Also the only remaining operational Bf-109E in the world isn't going to be put under any serious strain so the comment you recieved is entirely understandable.


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## syscom3 (Sep 1, 2007)

At a 13g load, most humanoids would either be dead or unconscience, thus ANY aircraft would be as good as gone.

Ive seen some figures (I think it was a thread here from a year ago) from the USN where the gee suits they used for the dive bombers, handled 7 - 9 gee's without pilot blackout.


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## drgondog (Sep 1, 2007)

Soren said:


> LoL, you're a joke Bill !
> 
> 7 G was rarely reached by fighters in combat during WWII, and the G-suits available back just barely made 5.5 G sustainable! I doubt the Franks G-suit helped pilots sustain anymore G's than the designed inclined seating position raised foot rests did for German pilots.
> 
> ...


*

I'll do the best I can to try to keep up with you*


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## drgondog (Sep 1, 2007)

Soren said:


> LoL, you're a joke Bill !
> 
> 
> The Bf-109 featured variable pitch horizontal stabilizers, the P-51 didnt, hence why the Bf-109 is able to regain control much quicker from a high speed dive than the P-51.
> ...



I'll do the best I can to try to keep up with you


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## drgondog (Sep 1, 2007)

Soren said:


> LoL, you're a joke Bill !
> 
> 7 G was rarely reached by fighters in combat during WWII, and the G-suits available back just barely made 5.5 G sustainable! I doubt the Franks G-suit helped pilots sustain anymore G's than the designed inclined seating position raised foot rests did for German pilots.
> 
> ...



I'll do the best I can to try to keep up with you


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## Kurfürst (Sep 2, 2007)

Not really want to bother the fun of your lovely 109/p51 debate but...







There existed a funny variant of the Bf 109G in the above configuration plus an 500 kg bomb under the fuselage, an aux. undercarriage was placed in under the rear fuselage, but that was due to the fact that more ground clearance was needed for the bigger bomb.

More comments on that 109 wing, when I will have a bit time to waste. 

Re : Encounter reports. I don't quite see what they prove, apart from that on occasion 109s were seen loosing wings in dives when pushed into extreme speeds (and in cases the 109 may have already reached higher airspeeds, we don't know the airspeed of both aircraft... to me they prove little as

a, First and foremost, they are victory reports. By definition, they only contain accounts when Mustangs are being victorious over enemy aircraft.

b, The dead unfortunately don't file their encounter reports. Probably that's why you don't have any Mustang pilot's account of _his_ plane disintegrating... being shot down, etc.

c, they come from spitfireperformance, by which is guaranteed that they are cherry picked for glory and censored for anything emberassing for the agenda that is rather clearly stated on the bottom of the page.

d, Not to mention other obvious factors, difference in the build quality of individual serial production planes, different handing of the planes - what if the plane was trimmed nose up, and it suddenly exited compressibility for example when reaching lower altitudes for example?

Too many unknowns.


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## drgondog (Sep 3, 2007)

Kurfürst said:


> Not really want to bother the fun of your lovely 109/p51 debate but...
> 
> 
> 
> ...



I agree d. completely along with my other comments (and yours) above although I would wonder why nose up trim at 25K when presumably one would dive and reach compressibility.. and at mid altitudes one would not reach compressibility. An absolute No No in P-51 manual is use of elevator trim to recover a dive - or exceed 3000 RPM

If Soren can produce the Design Limit load reference rather than just state a blanket superiorority I can listen to that also - But I have been looking at thousands of encounter reports in which 100's deatil a 51 in a terminal dive - very similar to Hofer's in the April report above - are undergoing noticable stresses in the chase and the 109 disintegrates so it wasn't uncommon. 

The reason I have been doing that is to attempt to piece and match US Macrs/awards with LW awards/losses via Tony Woods lists and vice versa. Obiously incomplete (lost or missing) records from LW make this a formidable task - but I have made great progress on the 355th FG.

Having said that I have no doubt that 51's probably suffered the same fate but perhaps different reasons.. like main gear popping out when uplock on door failed - or a high speed yaw causing a tail separation - or a 51 in desparation attempting a high speed diving roll with same results... but if Soren wishes to make that point - produce the facts.

on perhaps this thread or another one there was a discussion of 109 wings failing due to resonance - which I doubted - but it was close. Nowarra mentioned the 109F tail failures due to resonance following removal of truss on E model - so that story seems true. He also mentioned the cautions regarding extremely high G turns and dive recovery - causing 109F wing to fold at root. 

That's waht made me look at the 109 wing from my personal airframe structural engineering background - to SPECULATE (not know for certain) on the design of the wing - as I stated above. If I saw the actual designe analysis on how they compensated for the wheel well buried in 25% chord area and main spar behind that by more than a foot then I could be better informed... it also made sense that the 109 was never designed (exception on test a/c above) to carry heavy loads mid wing like all US fighters.

Anyway I will be interested in your comments on the wing.

Regards,

Bill


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## Kurfürst (Sep 3, 2007)

*Kurfurst - nice to chat. I read about a test bed 109 on Nowarr's book that was designed to be a fighter bomber with wing hardpoint and a reinforced CL rack for a 550kg bomb.

Are you proposing this as a standard production G aaround which fighter bomber groups were organized?*

That was the G-1/R1 (500kg + 2 x 300 liter underwing droptanks). It was a long range FB model of which a handful was produced. The reason it did not see widespread service - apart from it's oddity - was probably that they had the FW 190, which was much more suited as a JaBo in any case. The 109G remained as a fighter, and on occasion a fighter bomber with a 250 kg bomb under the fuselage. It wasn't that much of a stuctural limitation, but a ground clearance issue; the 109K, which had longer tailwheel as standard, was cleared for the larger 500 kg bombs (and I suppose it stood true for the 109Gs which were having the long tailwheel).

The picture I've posted is a G-4/R3 variant, which was a standard variant, produced on smaller scale (80 or so as I recall, but there was also a G-6/R3 variant which production numbers I can't comment on. G-6 production is a mess), and it was used as a long range fighter recce, with the two droptanks under the wings and camera equipment in the fuselage. The engine cannon was retained, but in the MGs place extra oil capacity was built in. I am no expert on their operations, but they certainly operated in the Med and from Norway (one was shot down in a dive above Scapa Flow, described in Clostermann's book).

Given the above, I doubt it would present too much technical trouble to use the 109 wing to carry loads. You might recall it carried gondola weapons, and it was cleared for high loads under this condition, ie. manouvering dogfights. Each gondola loaded put ca 120 kg under the fuselage, so given that and the fact that operational versions with about 250 kgs under each wings (i.e the long range FRs depicted with the droptanks) were used.
the 109 disintegrates so it wasn't uncommon.


*on perhaps this thread or another one there was a discussion of 109 wings failing due to resonance - which I doubted - but it was close. Nowarra mentioned the 109F tail failures due to resonance following removal of truss on E model - so that story seems true.*

Yes, there were early 109F tail failures which I believe were rooted back to resonance from the engine at certain RPM. These were solved by adding external stiffeners to the tail section, and later internal ones.

Anyway, I don't quite see the point. The 109F had a new layout and was in the aerodynamic sense almost completely new airframe save for the centre section, so a few surpises at the time of the introduction were needed to be ironed out. Resonance also have absolutely nothing to do with actual structural strenght.

*He also mentioned the cautions regarding extremely high G turns and dive recovery - causing 109F wing to fold at root.*

I believe these statements root in British P/W interrogations about the new 109F. A P/W noted that two pilots, one of them being Balthasar snapped their wings on a 109F during high-G pulls in snaking dives. I presume Nowarra (who's rather old work is riddled with errors otherwise) simple repeated these Air Intelligence interrogations, being easy-to-find material. OTOH there's a lot of funny stuff in those A.I. reports, Me 209s etc.

In any case, the 109G wing was strenghtened, so maybe the F-wing was insufficently stressed - that I doubt, US measurements on it were quite positive. It was found to be satisfactory for flutter effects, and had a rather high aileron reversal point of 850 mph. To quote from the report (from March 1944) :

_'
3. The analysis for flutter and aileron reversal indicate that the Me-109F is satisfactory from the flutter standpoint at speeds up the limit diving speed.

4. The wing torsional rigidity of the Me-109E wing, which is practically identical with the Me-109F wing, compares favourably with that of a similiar high speed AAF pursuit plane.'_

*That's waht made me look at the 109 wing from my personal airframe structural engineering background - to SPECULATE (not know for certain) on the design of the wing - as I stated above. If I saw the actual designe analysis on how they compensated for the wheel well buried in 25% chord area and main spar behind that by more than a foot then I could be better informed... it also made sense that the 109 was never designed (exception on test a/c above) to carry heavy loads mid wing like all US fighters.*

There's a French report describing in detail the 109E wing construction; to summerize it, the main spar only takes bending loads, whereas the box spar took the torsional loads. The report notes that the use of plating was rather thick (1-1.5mm), I guess Messerschmitt simply used heavy thickness skin at critical points, formed into a torsion box by 'false' ribs around the wheel well. In any case, combined torsional and bending loads were a sort of a common problem at the time, aircraft structure was usually not designed to resist _both _ at one time (IIRC there's a NACA report mentioning that in regard of the P-47 as well)

The 109 had a box spar and a larger sizeable I-beam as a main spar to carry loads of the wings. The spar, the skin and ribs were reinforced multiple times during it's life. I have it documented in reports that this happened on the 109E, and on the 109G as well (which sported the new 109F wing).

As for the wing, Messerchmitt certainly did not like the idea of putting things into the wings. It was far from not being doable though. Galland even field-hacked his 109F, and put a 20mm Oerlikon FF into each wing. The Spanish post-war 109G airframes could cope with the rather sizable Hispano the Spanish built into the wings. Late war variants proposed as heavy fighter variants of the 109K saw both MK 108s and MG 151/20s alternatively built into wings.

I guess the the notion of the 109 wing not being able to cope with internal armaments stems from the fact that gondola weapons were used, an 'odd' solution. But in fact the gondolas did not add any more weight than an internal installation, and the (rather small) drag rise they gave was comparable to any internally mounted weapons of the era. Gondolas, as per Messerschmitt's datasheets, chopped off 8 km/h or about 5 mph from the top speed of the 109G at SL. Actually a bit less than Hispano installations in Spitfire wings. In other words, if Messerschmitt would have wanted to please the crowds 50 years later, and would have gone with an internal arrangement, he would have the same mount of performance loss. OTOH, the extremely heavy firepower (on par with a contemporary FW 190A) provided by the gondolas was seldom needed (the gondies themselves go back to late 1941), and being a complete unit, they could be easily mounted and dismounted when needed, they seem to me a rational design choice (and also complied well with the modular-designs the Germans preferred at that time, plus it spared the time to make changes in the wing design, and production lines).

Cut the long story short, I don't believe there was any extraordinary problem with the 109's wings structural strenght, nor do I believe that if they'd have wanted to have external stores under the wings it could not have been done in short order, given the similiar loads already carried by the 109 in production. If the 109G wing could carry a 250 kg worth droptank, it could certainly carry a 250 kg bomb, it was a matter of adding an extra rack under each wing in place of the underwing panel for the gondolas. Why it wasn't done? I dunno, but I suspect the FW 190 already took up that job.

What else was there catching my eye? Oh yes, if carrier stresses mean anything, there was a Bf 109T version meant for (never to come) carrier ops. Carrier-capability was probably one reason to have the U/C mounted on the fuselage, in any case it removed landing stresses from the wing structure and spar, and also gave a nice added bonus to maintaince and repair of the wing, which could be simply removed and replaced without disassamling the undercarriage. And no, the narrow undercarriage wasn't a root for the tendency to groundloop (the aircraft's relative real CoG on ground was), though it certainly made it more prone to the effects.


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## drgondog (Sep 4, 2007)

Kurfurst - good to chat...

On Norwarr, I have read other accounts (other thyan Norwarr) about the 109F 'early issues' - and really don't think it was representative of the airplane - similar gestation problems were encountered in 51B from A. 

Just wanted to remind Soren, that is what you expect in war time when you up engine, drop wings and make otherwise significant changes to a sound airframe like a 51.

What it (Norwarra) highlighted (for me) was that all fighters that start out light and gain thousands of pounds to adapt to performance enhancing changes don't always get to escape more weight added in form of say .050 upper and lower skins around the torsion box to take the shear that .032 would no longer take (or whatever the design approach)

Without belaboring the point I think we have arrived at a couple of points.

Soren has not offered us examples of wing stores and internal loads to match or even get close to day to day operational wing stores of a 51. Nor has he offered substantiation that a 109G (as the long production - most typical adversary) was indeed structurally sounder in any documentation that shows even a Design Ultimate load. (You suggested and I would believe 10.8 which would make a pilot suggested manuevering load of 7.2 g) - But I SERIOUSLY doubt that 1935 and 1940 fighter designers were designing to 13 G vertical for manuevering loads in Ultimate Failure Limits - This comment has nothing to do with actual load tests as we (as a former airframe structures guy were often accused of building bridges - not airframes) and conservative approaches in calcs lead to suprising test results. That doubt does not make me right, BTW

At the end of the day I have no doubt most fighters of both varieties exceeded 12 g in thunderstorms, manuevering pullouts etc.. but until I see the doc on the 109 wing I remain skeptical that the wing is as strong as a 51 in Bending.. or Torsion. 

I also remain a little skeptical that Willy simply dropped the 30 mm Gondola below the wing just because it was easier to access - I am aware of post war mods - but who knows what the performance criteria were? or the mission. Did Franco want a strafer or was he planning on taking on the RAF and USAAF Heavy bomber forces?

I'm aware of the K - but have the same issue on what processes or changes were made to the wing when the 30 was dropped in. This is area where my ignorance surfaces. I don't even know if an airfoil change was made, or whether a reinforced spar and torsion box was made - but once it is a new wing instead of a field retrofit - all kinds of changes can be made internally to stiffen wing for both bending and torsion 

- it was a penalty in manuevering performance. 

I dont have proof but I don't believe he wanted to cut up that spar/torsion box out in the CL range. You and I can agree this is my opinion only

As to a CL bomb - best place in world for it - fuse already beefed up for hard landings in that area. (Ditto 51 for wing attach).. but if it had been more desirable for operations to carry bigger bombs on 109, the wing is better for ground clearance - so wing would be natural unless there were structural limits in the mind of a Messerschmitt engineer.

German engineers have not impressed me as 'ILLOGICAL"

Regards,

Bill


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## drgondog (Sep 5, 2007)

Kurfürst said:


> *Kurfurst - nice to chat. I read about a test bed 109 on Nowarr's book that was designed to be a fighter bomber with wing hardpoint and a reinforced CL rack for a 550kg bomb.
> 
> Are you proposing this as a standard production G, around which fighter bomber groups were organized?*
> 
> ...



On the last comment about internal guns - no aerodynamicist would tolerate hanging a gun tub under the wing - causing more drag and reduced performance unless there was a very good reason why an internal installation was worse. One 'worse' consequence of course is re-tooling and delays in production to accomodate complex re-design for internal structure reasons - but what elese?


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## Soundbreaker Welch? (Sep 5, 2007)

Not a good idea, I agree.


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## HoHun (Apr 18, 2009)

Hi Ricardo,

>Overall... which one is better dogfighting?

Quite clearly the Me 109F.

Here is a performance comparison of the Me 109F-4 and the P-38F ...

Regards,

Henning (HoHun)


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## Vincenzo (Apr 18, 2009)

why the 109F-4 it's so slow?


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## HoHun (Apr 18, 2009)

Hi Vincenzo,

>why the 109F-4 it's so slow?

Hm, how fast do you think it should be? I know that there is a considerable range of claimed speeds for this type, but I think 635 km/h @ 6 km is probably a good number for Steig- und Kampfleistung. (It looks like Notleistung wasn't cleared for the DB 601E at least for a good part of its service life - of course the Friedrich would be faster with more power.)

The speed indicated above is not the result of an in-depth analysis like those I posted in the technical section, though. Any data providing deeper insights would be welcome 

Regards,

Henning (HoHun)


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## Vincenzo (Apr 18, 2009)

saw the comparison with P-38-F so encounter only in late '42, i think notleistung was available or not?


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## HoHun (Apr 18, 2009)

Hi Vincenzo,

>saw the comparison with P-38-F so encounter only in late '42, i think notleistung was available or not?

Hm, it seems "Zeugmeister" has found some new documents since I last checked this topic ... it looks like Notleistung was cleared with the February 1942 manual: Beim-Zeugmeister: Seite 8 - Flugzeughandbuch der Bf 109 F-4

Attached a comparison based on Notleistung.

Regards,

Henning (HoHun)


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## Vincenzo (Apr 18, 2009)

the speed commonly indicated for notleistung are 660/670 was your it's only 645 ?


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## HoHun (Apr 18, 2009)

Hi Vincenzo,

>the speed commonly indicated for notleistung are 660/670 was your it's only 645 ?

Yes, that's what automatically follows from the 635 km/h @ 6 km data point if you use the DB 601E Notleistung power curve instead of Steig- and Kampfleistung.

A more accurate way to approach the Me 109F-4 speed question might be to start with the Me 109F-2 Kennblatt (as in my opinion, these Kennblätter are fairly accurate) and replace the DB 601N power curve with the DB 601E curves. However, this will be somewhat awkward as there were several versions of the DB 601N ratings ...

Regards,

Henning (HoHun)


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## Vincenzo (Apr 18, 2009)

why coming 645 km/h from 635 km/h of kampfleistung?, 
if i undestand 635 km/h with 1200 hp becoming with 1350 hp
1350/1200 = 1,125
cube root 1,125 = 1,04...
speed 635 * 1,04 = 660 km/h


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## HoHun (Apr 19, 2009)

Hi Vincenzo,

>why coming 645 km/h from 635 km/h of kampfleistung?, 
>if i undestand 635 km/h with 1200 hp becoming with 1350 hp
>1350/1200 = 1,125
>cube root 1,125 = 1,04...
>speed 635 * 1,04 = 660 km/h

That's a good rule of thumb, but in the specific case the Me 109F-4 also has to increase the engine speed from 2500 rpm to 2700 rpm to gain the extra power.

That increases the propeller tip speed at 6 km to Mach 0.98, leading to a greatly decreased propeller efficiency. According to my calculations, total thrust including exhaust thrust is 4545 N, while at 2500 rpm with a propeller tip speed of Mach 0.92, it's 4513 N.

The increase in shaft power is virtually completely consumed by the reduced propeller efficiency, and I guess if the higher power setting wouldn't yield more exhaust thrust as a by-product, there would be no increase in top speed at all.

Regards,

Henning (HoHun)


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## Vincenzo (Apr 19, 2009)

thanks for explication


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## Vincenzo (Apr 19, 2009)

there is an other trouble why the luftwaffe data, in Rausch pages, are so different from your calculation?


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## HoHun (Apr 19, 2009)

Hi Vincenzo,

>there is an other trouble why the luftwaffe data, in Rausch pages, are so different from your calculation?

Hm, in which regard? I used the same 635 km/h figure from the "Messerschmitt calculated" data sheet on his site. I didn't use the "Rechlin tested" 670 km/h figure because there is so little detail on the source.

Regards,

Henning (HoHun)


----------



## Vincenzo (Apr 19, 2009)

So for you the data on page 12, of your link, aren't reliable?


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## HoHun (Apr 19, 2009)

Hi Vincenzo,

>So for you the data on page 12, of your link, aren't reliable?

On page 12, there is "Cw Schnellflug" ('Cd0 for high speed flight') listed on both pages as 0.023. 

Power is listed as 1185 HP for 635 km/h, 1280 HP for 670 km/h.

As I pointed out above, this power difference is not going to yield the claimed speed difference due to the reduction in propeller efficiency.

So the data looks self-contradictory. Now the question is: Which speed is correct (if any)?

I spontaneously relied on the 635 km/h figure, but that's just a guess. By comparing to the (in my opinion) more trustworthy Me 109F-1/2 data sheet, I might be able to make it more than a guess, but I haven't found the time to make this kind of cross-check yet.

Regards,

Henning (HoHun)


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## Vincenzo (Apr 19, 2009)

ok again thanks for explication and patience


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## mkloby (Apr 19, 2009)

HoHun said:


> Hi Vincenzo,
> 
> >why coming 645 km/h from 635 km/h of kampfleistung?,
> >if i undestand 635 km/h with 1200 hp becoming with 1350 hp
> ...



Hey HoHun,
I'm not greatly into the systems of much of the WWII planes, but why wouldn't the prop rpm stay constant and increase pitch to harness the additional power?


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## HoHun (Apr 19, 2009)

Hi Mkloby,

>I'm not greatly into the systems of much of the WWII planes, but why wouldn't the prop rpm stay constant and increase pitch to harness the additional power?

Hm, I think simply increasing the boost pressure from 1.30 ata to 1.42 ata without increasing rpm would probably induce detonation. Another reason might be that the internal forces would inevitably increase, perhaps beyond what the engine was stressed for.

I have a copy of the DB 601E power chart, so I know they increased the engine speed for Start- und Notleistung, but the engineering reason not to accept the higher boost pressure at constant boost is not obvious from that.

Your question is certainly well-justified as though it's typical to have emergency power ratings employ higher engine speeds than the typical "30 min" settings, many engines also were able to benefit from increased boost pressure at constant rpm (though this more typically was used to make a short-duration emergency rating more powerful).

I believe the general idea of exploiting the better propeller efficiency at lower rpm was used with the GM-1 injection systems, which at high altitude and great true air speeds would have really pushed the propeller tip speeds. GM-1 was typically used at the "30 min" rating engine speed - and the requirement to limit the internal forces in my opinion is one of the reasons GM-1 could only used at altitudes somewhat above the engine's full throttle height.

Regards,

Henning (HoHun)


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## mkloby (Apr 19, 2009)

HoHun,
From what I read, the Bf 109F had a constant speed propeller. What I don't understand is if engine rpm increases, why would prop rpm increase? Why wouldn't the prop increase pitch in order to maintain a constant prop speed?


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## HoHun (Apr 19, 2009)

Hi Mkloby,

>From what I read, the Bf 109F had a constant speed propeller. What I don't understand is if engine rpm increases, why would prop rpm increase? Why wouldn't the prop increase pitch in order to maintain a constant prop speed?

It would, but there are just two ways to increase the power of a piston engine: Increasing the force of the power strokes, or increasing the frequency of power strokes.

If you increase the force of the power strokes, you'll increase the torque of the engine, and there is usually some kind of torque limit not close off the 30 min operating conditions. (Even worse and more complicated, bad things can happen in the combustion chamber. I'm not familiar with all the nasty details of that either, but "detonation" is a keyword there.)

Alternatively, you can increase the frequency of power strokes, which will keep you clear of the torque limits as the power is developed through an increase of engine speed at the same internal forces as before. That was historically the main route to emergency power for piston engines.

Below a diagram showing the operating conditions of the B-29's R-3350 engine. Note that there is a narrow band for each manifold pressure at which operation of the engine is both possible and sensible. You can always increase rpm without danger, that will needlessly increase fuel consumption. If you decrease rpm however, that will increase "engine pressures", internal forces or torque, which are more or less three different ways of looking at the same problem.

(While on the US B-29, it was the task of the flight engineer to keep the engine in the best operating range, many German aircraft were equipped with single-lever control systems that selected the optimum combination of rpm and boost and a couple of other variables such as ignition timing automatically, based on information from perhaps a half dozen of sensors. I'm not sure if the DB 601E in the Me 109F-4 was manually or automatically controlled, but the concept of staying in the small safe and sensible operating area as outlined in the B-29 graph was the same regardless.)

Regards,

Henning (HoHun)


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## drgondog (Apr 19, 2009)

HoHun said:


> Hi Vincenzo,
> 
> >saw the comparison with P-38-F so encounter only in late '42, i think notleistung was available or not?
> 
> ...



There is an incredible disparity between the turn rates of the 38F and 109 in your plot - particularly at 1000m and 6500m where the velocities cross over.

Are you using the Clmax for the NACA 23016 airfoil 'bare' or with manuevering flaps? With manuevering flaps the USAAF had the P-38F turning with the P-51 at Eglin Field (between 12000 and 15000+ feet!

Your plots show the 51D to be approx 0ne degree per sec slower than the 109 on the deck but you show 5+ degrees difference between the 109 and the 38F on the deck and 4 1/2 degrees at 12,000 where the 38F had parity with a 51A. 

Which Clmax are you using for the 38F and what value are you using for AoA at CLmax? What Cd0 are you using for the 38 and what values for trim drag (with or without maneuvering flaps)?

Where is the math?


----------



## mkloby (Apr 19, 2009)

HoHun said:


> Hi Mkloby,
> 
> If you increase the force of the power strokes, you'll increase the torque of the engine, and there is usually some kind of torque limit not close off the 30 min operating conditions. (Even worse and more complicated, bad things can happen in the combustion chamber. I'm not familiar with all the nasty details of that either, but "detonation" is a keyword there.)
> 
> ...



HoHun,
Interesting - it just isn't make sense to me why increasing engine RPM would necessitate increasing prop RPM. On every aircraft I have flown with a constant speed prop, the blade angle is managed in order to maintain a specified RPM. If power is increased, blade angle then increases to maintain the same N2, if power decreases, it reduces blade angle.

I have read that the 109F had an electric operated constant speed prop. I am not sure how this one worked. I have read that it was automatic with a manual override option as well.


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## CharlesBronson (Apr 19, 2009)

P-38, better firepower and faster, with the correct tactic the messer is toasted. I think the both types meet each other over Tunisia in late 1942...right ? Many Me-109 in that teather of operation were the G type already.
By the way 635 mk/h sound a very good figure for the F-4 considering that is the same speed quoted for the G-2 variant wich had a little more powerful engine ( 1350 compared with 1475 hp).


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## HoHun (Apr 20, 2009)

Hi Mkloby,

>Interesting - it just isn't make sense to me why increasing engine RPM would necessitate increasing prop RPM. On every aircraft I have flown with a constant speed prop, the blade angle is managed in order to maintain a specified RPM. If power is increased, blade angle then increases to maintain the same N2, if power decreases, it reduces blade angle.

It works more or less like that on the Messerschmitt, too. If you set rpm to 2700 rpm to begin with, you could hypothetically control power through boost pressure alone, though that would not be the most efficient way to operate the engine.

Regards,

Henning (HoHun)


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## mkloby (Apr 20, 2009)

HoHun said:


> Hi Mkloby,
> 
> >Interesting - it just isn't make sense to me why increasing engine RPM would necessitate increasing prop RPM. On every aircraft I have flown with a constant speed prop, the blade angle is managed in order to maintain a specified RPM. If power is increased, blade angle then increases to maintain the same N2, if power decreases, it reduces blade angle.
> 
> ...



You seem to be referring to engine RPM. I am referring to maintaining a specified prop RPM - there is no reason I can see that should cause prop RPM to increase turns, regardless of an increase in engine power at higher engine RPM.


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## HoHun (Apr 20, 2009)

Hi Mkloby,

>You seem to be referring to engine RPM. I am referring to maintaining a specified prop RPM

Hm, unlike as with some turbine types, on most aircraft piston powerplants engine rpm and prop rpm are directly proportional to each other as they're connected through a fixed-ratio gearing (or directly, in lower powered types). If I mixed the two terms, that would be because they change in unison so that I didn't think of them as separate 

>there is no reason I can see that should cause prop RPM to increase turns, regardless of an increase in engine power at higher engine RPM.

Hm, I don't think that we already touched this topic, but increased thrust (regardless how it's achieved) does in fact improve an aircraft's specific excess power, improving its capability for sustained turns.

Instantaneous turns will be unaffected, of course. I guess that's what you were thinking of?

(Just so that the idealized term "instantaneous" won't cause unnecessary confusion: non-stabilized turns of finite duration would actually be influenced by power available 

Regards,

Henning (HoHun)


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## HoHun (Apr 20, 2009)

Hi Charles,

>By the way 635 mk/h sound a very good figure for the F-4 considering that is the same speed quoted for the G-2 variant wich had a little more powerful engine ( 1350 compared with 1475 hp).

I don't know where you have the 635 km/h for the Me 109G-2 from, but the wartime summary report on the Me 109G-6 credits the Me 109G "Grundausführung" ('basic variant') with 630 km/h at 1.30 ata/2600 rpm. The 1475 HP you list is for the full 1.42 ata/2800 rpm emergency power setting.

Kurfrst - Leistungzusammenstellung Me 109 G.

As background: The 'basic variant' is essentially a G-2 with rigid tail wheel and all the little bumps of a G-6, but without the MG 131 blisters. It's a hypothetical plane serving as baseline for establishing the performance of G-6 series production aircraft with all the variations they were built with, but of course its performance figures were based on flight tests of multiple Gustav aircraft in different configurations.

The real G-2 was a bit cleaner still, and accordingly a bit faster as well.

Regards,

Henning (HoHun)


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## CharlesBronson (Apr 20, 2009)

> I don't know where you have the 635 km/h for the Me 109G-2 from, but the wartime summary report on the Me 109G-6 credits the Me 109G "Grundausführung" ('basic variant') with 630 km/h at 1.30 ata/2600 rpm. The 1475 HP you list is for the full 1.42 ata/2800 rpm emergency power setting.



I saw that figure in the well know Squadron Signal and the Osprey collection ...I know, I know those are not technical editions.


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## Vincenzo (Apr 20, 2009)

saw your figure and explication, now i think that 670 km/h for full power 109 F-4 isn't correct for compressibility effect, (like the 660km/h for climb/combat power setting, that coming 635 km/h corrected)


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## Soren (Apr 20, 2009)

670 km/h doesn't seem illogical if GM-1 was used, but if the propeller couldn't transfer the extra power then I guess its a moot point.


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## mkloby (Apr 20, 2009)

HoHun said:


> Hi Mkloby,
> 
> >You seem to be referring to engine RPM. I am referring to maintaining a specified prop RPM
> 
> Hm, unlike as with some turbine types, on most aircraft piston powerplants engine rpm and prop rpm are directly proportional to each other as they're connected through a fixed-ratio gearing (or directly, in lower powered types). If I mixed the two terms, that would be because they change in unison so that I didn't think of them as separate


I need to get an old aircraft manual to look at now, because that seems to defeat the whole point of a constant speed prop, ie changing pitch to maintain a set propeller RPM.




HoHun said:


> Hm, I don't think that we already touched this topic, but increased thrust (regardless how it's achieved) does in fact improve an aircraft's specific excess power, improving its capability for sustained turns.
> 
> Instantaneous turns will be unaffected, of course. I guess that's what you were thinking of?
> 
> ...



I confused you with that one, sorry about that - "turns" is a rotary wing slang for Nr (rotor rpm). I was referring to prop rpm there. I'll blame it on the V-22, since we still call it Nr.


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## FLYBOYJ (Apr 20, 2009)

HoHun said:


> Hi Mkloby,
> 
> >You seem to be referring to engine RPM. I am referring to maintaining a specified prop RPM
> 
> Hm, unlike as with some turbine types, on most aircraft piston powerplants engine rpm and prop rpm are directly proportional to each other as they're connected through a fixed-ratio gearing (or directly, in lower powered types). If I mixed the two terms, that would be because they change in unison so that I didn't think of them as separate





mkloby said:


> I need to get an old aircraft manual to look at now, because that seems to defeat the whole point of a constant speed prop, ie changing pitch to maintain a set propeller RPM.



A few things to look at here folks.

Although you have have a recip aircraft with a constant speed prop attached to the engine either directly or through an RGB, RPM will be controlled by the Prop - power by the engine and we measure that "power" though manifold pressure. To take it a bit further we cold also measure torque so we don't put too much power or rpms on the RGB depending on power and prop settings. This is more commonly found on turbine engines because they could put out a lot more torque a lot quicker than recips, especially in engines like a PT6. 

The constant speed prop will build up or reduce speed based on engine RPM delivered to the prop governor which will allow pitch changes depending if we're in a dive or climb. As Henning stated earlier, there are some aircraft that have this happen automatically (I actually think the Fw.190 was the first aircraft to have this - Mooney copied the set up in the late 1960s I believe.)

Also consider that there always needs to be a way to prevent the propeller from driving the engine. In many turbine engines this is done automatically but I believe in recips the pilot or FE will have to prevent this.


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## HoHun (Apr 21, 2009)

Hi Mkloby,

>I need to get an old aircraft manual to look at now, because that seems to defeat the whole point of a constant speed prop, ie changing pitch to maintain a set propeller RPM.

Thanks to Micdrow's and Roy's efforts, we have a great collection of them in the technical forum section 

>I confused you with that one, sorry about that - "turns" is a rotary wing slang for Nr (rotor rpm). I was referring to prop rpm there. I'll blame it on the V-22, since we still call it Nr.

Ah, I see! But even then I still don't understand your original comment, I have to admit:

"I am referring to maintaining a specified prop RPM - there is no reason I can see that should cause prop RPM to increase turns, regardless of an increase in engine power at higher engine RPM."

Regards,

Henning (HoHun)


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## HoHun (Apr 21, 2009)

Hi Flyboyj,

>As Henning stated earlier, there are some aircraft that have this happen automatically (I actually think the Fw.190 was the first aircraft to have this - Mooney copied the set up in the late 1960s I believe.)

I think it was actually Bramo who developed the single-lever control before merging with BMW, who applied the technology to the BMW 801 then.

I think the Focke-Wulf Fw 200 was already equipped with single-lever control before the Fw 190, but I'm not entirely certain of that.

Regards,

Henning (HoHun)


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## Vincenzo (Apr 21, 2009)

Soren said:


> 670 km/h doesn't seem illogical if GM-1 was used, but if the propeller couldn't transfer the extra power then I guess its a moot point.



for true info for GM-1 gave also highest velocity, but nobody was talking with GM-1 used


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## drgondog (Apr 21, 2009)

HoHun said:


> Hi Vincenzo,
> 
> >saw the comparison with P-38-F so encounter only in late '42, i think notleistung was available or not?
> 
> ...



The P-38F-15 and all suceeding versions have the inboard NACA 23016 airfoil with manuever flap inboard of the engines, and a NACA 4412 outboard of the engines. I am chasing an obscure reference to determine whether all P-38F's were retrofitted with the manuever flap but for sure the -15 had them

Lockheed P-38F Lightning

As near as I can determine 121 F-15s were produced before 9/42when the G series superceeded the F. Which version are you using for your comparisons? The Mike Williams data for the USAAF March 8, 1943 report are F-1's

Which P-38F did you model and what math approach did you use for Clmax calculations in turn performance to account for the different stall characteristics?


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## Vincenzo (Apr 21, 2009)

why a planes build in '42 have a '43 serial number?


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## FLYBOYJ (Apr 21, 2009)

Vincenzo said:


> why a planes build in '42 have a '43 serial number?


The serial number year represents when the contract was issued.


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## Vincenzo (Apr 21, 2009)

FLYBOYJ said:


> The serial number year represents when the contract was issued.



so it's more strange planes build before of contract??


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## FLYBOYJ (Apr 21, 2009)

Vincenzo said:


> so it's more strange planes build before of contract??


Because that' the way the contract is let out, especially when large numbers are involved. It actually represents a purchase for the indicated "fiscal year." Although being built in 1942, the aircraft in question was purchased with 43' "money." This will happen with multi-year funding or military equipment.


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## Vincenzo (Apr 21, 2009)

i found that US fiscal year start at october so planes ordered last 3 months of '42 are in '43 fiscal


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## FLYBOYJ (Apr 21, 2009)

Vincenzo said:


> i found that US fiscal year start at october so planes ordered last 3 months of '42 are in '43 fiscal


Yes, the contract could have been awarded in that manner.


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## mkloby (Apr 21, 2009)

HoHun said:


> Hi Mkloby,
> 
> >I need to get an old aircraft manual to look at now, because that seems to defeat the whole point of a constant speed prop, ie changing pitch to maintain a set propeller RPM.
> 
> Thanks to Micdrow's and Roy's efforts, we have a great collection of them in the technical forum section


I'm sifting through various manuals and trying to dig up info...



HoHun said:


> >I confused you with that one, sorry about that - "turns" is a rotary wing slang for Nr (rotor rpm). I was referring to prop rpm there. I'll blame it on the V-22, since we still call it Nr.
> 
> Ah, I see! But even then I still don't understand your original comment, I have to admit:
> 
> ...



Apparently it is difficult to find good detailed info on the actual operation of the VDM 109 prop. My basic point being is that even if engine rpm and power are increased, blade pitch should be able to be increased as well maintaining an "ideal" propeller rpm regardless of engine rpm.

From what I understand the 109F had an AUTOMATIC setting, which would adjust blade pitch without manual inputs (although it could be overridden manually).

Seems like there is something I am missing here.


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## drgondog (Apr 21, 2009)

FLYBOYJ said:


> Yes, the contract could have been awarded in that manner.



Joe - there are some strange practices all over the map -

P-51D prototypes USAAF #AC-30479 awarded in 2-27-43 were USAAF serial number 42-106539 and 6740 (THESE TWO were 'plucked' from the P-51B-10NA Block below)

P-51D-5NA, USAAF #AC-40064, dated 4-13-43 were USAAF serial numbers 44-13253 through 44-14052. This is the first block after the two prototypes.

P-51C-10NT, USAAF #AC-40063 (contract no. PRECEEDING the above P-51D-5NA) was dated 5-3-43 (dated AFTER the above P-51D-5NA).. go figure.

P-51B-10NA, AC-30479, dated 10-20-42 were USAAF serial numbers 43-7113 thru 7202, then 42-106429 to 42-106538 (see two ships above that became D prototypes - same contract), then 42-106541 through 106738.


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## HoHun (Apr 21, 2009)

Hi Mkloby,

>Apparently it is difficult to find good detailed info on the actual operation of the VDM 109 prop. My basic point being is that even if engine rpm and power are increased, blade pitch should be able to be increased as well maintaining an "ideal" propeller rpm regardless of engine rpm.

The propeller could do that, but the engine, geared to the propeller at a fixed ratio, would not run at the optimum speed for the power output selected that way.

The DB 601E data sheet attached below shows the use of different engine speeds for different power outputs. It's perfectly typical for the period in this regard, and you'll find the same progression of engine speeds with increasing power in US Specific Engine Flight Charts.

>From what I understand the 109F had an AUTOMATIC setting, which would adjust blade pitch without manual inputs (although it could be overridden manually).

I believe that the automatic setting was meant single lever operation with the desired speed set by the propeller lever. Upon flipping a small electrical switch mounted below the throttle quadrant (very hard to make out in cockpit shots of the Me 109), the propeller went to variable pitch operation, with the pilot using two pushbuttons on the throttle grip to adjust propeller pitch. Unlike Allied aircraft, most German aircraft featured a propeller pitch indicator with two hands, calibrated just like a clock, and the standard operation pitch values were actually given in the manner "for take-off, set pitch to a 'quarter to twelve'" and so on.

I think it was standard to go to manual operation of propeller pitch (and cowl flaps) for take-off and landing to avoid the lag times introduced by automatic gouvernors. A modern description of the procedures used with a restored Me 109G published recently in a German magazine shows that they adhere to this practice, too.

Regards,

Henning (HoHun)


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## FLYBOYJ (Apr 21, 2009)

drgondog said:


> Joe - there are some strange practices all over the map -
> 
> P-51D prototypes USAAF #AC-30479 awarded in 2-27-43 were USAAF serial number 42-106539 and 6740 (THESE TWO were 'plucked' from the P-51B-10NA Block below)


"Plucked" Part of an original procurement and then re-manufacturerd, I seen either the original s/n used or anothwer one re assigned


drgondog said:


> P-51D-5NA, USAAF #AC-40064, dated 4-13-43 were USAAF serial numbers 44-13253 through 44-14052. This is the first block after the two prototypes.


I think paid with 1944 money


drgondog said:


> P-51C-10NT, USAAF #AC-40063 (contract no. PRECEEDING the above P-51D-5NA) was dated 5-3-43 (dated AFTER the above P-51D-5NA).. go figure.


Pot luck!!


drgondog said:


> P-51B-10NA, AC-30479, dated 10-20-42 were USAAF serial numbers 43-7113 thru 7202, then 42-106429 to 42-106538 (see two ships above that became D prototypes - same contract), then 42-106541 through 106738.


Again "plucking" or remanufacturing of the airframes is my guess.

Did you see the post about the A-37's in Vietnam? They too carried two set of S/Ns - my guess is they started out life as a T-37 and went through depo and was modded to an A-37.

I guess in the end its all about how Uncle Sam want to pay for something. Right now we're starting work that's on 2010 funding, so I'm told - some things never change!


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## mkloby (Apr 21, 2009)

HoHun said:


> Hi Mkloby,
> 
> The propeller could do that, but the engine, geared to the propeller at a fixed ratio, would not run at the optimum speed for the power output selected that way.


Hey HoHun,
From what I have read (and what you have been trying to tell me!) the Bf 109, I believe from D on) had a Variable Pitch Prop. Some sources seem to indicate that the 109s had Constant Speed Prop, which is what confused me. We're good now. Thanks!


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## HoHun (Apr 21, 2009)

Hi Mkloby,

>From what I have read (and what you have been trying to tell me!) the Bf 109, I believe from D on) had a Variable Pitch Prop. Some sources seem to indicate that the 109s had Constant Speed Prop, which is what confused me. We're good now. Thanks!

Hehe, welcome, but I don't think we've fully exploited the confusion yet 

The Me 109 from some version on did in fact have a constant speed propeller.

The desired speed was normally set by a simple analogue computer to match the boost pressure selected by the pilot according to a pre-defined curve. (Maybe more inputs and outputs were involved, but that's the most important thing it did.)

However, if the pilot thought it made sense, he could also flip a switch and operate the constant speed propeller in "dumb" variable pitch mode.

Except that they didn't have a single-lever control but a conventional throttle lever/propeller speed lever combination, some US aircraft had similar capabilities for manual pitch control, for example the FM-2 Wildcat.

From NACA report WR-E-192, here a chart showing the basic relation between rpm and manifold pressure the BMW 801 engine computer would yield under normal conditions. The propeller was a constant-speed unit, but on which speed it attempted to stabilize was commanded by the engine computer depending to the power lever position that also governed rpm.

The DB 601E must have had a similar, if maybe somewhat simpler unit, too.

Regards,

Henning (HoHun)


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## HoHun (Apr 21, 2009)

Hi again,

From the same NACA report WR-E-192, another chart showing the functional units of the BMW 801 engine computer. Note that it includes the constant-speed governor of the propeller (which can be overridden by the pilot in just the same way as that of the DB 601E).

Regards,

Henning (HoHun)


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## mkloby (Apr 21, 2009)

HoHun said:


> Hehe, welcome, but I don't think we've fully exploited the confusion yet
> 
> The Me 109 from some version on did in fact have a constant speed propeller.
> 
> ...


If the aircraft had a constant speed prop, the prop gov would seek to maintain an "ideal" prop rpm speed. If the engine is geared to the propeller at a fixed ratio, as you earlier stated, I don't understand how this is possible.

I had read in AUTO mode the prop pitch would be set to a prescribed pitch setting based on boost, not that a prescribed prop rpm speed was tied to boost. Also, another document stated that the prop gov limited prop rpm in proportion to the throttle setting. It would not govern the rpm at a set rpm...


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## HoHun (Apr 21, 2009)

Hi Mkloby,

>If the aircraft had a constant speed prop, the prop gov would seek to maintain an "ideal" prop rpm speed. If the engine is geared to the propeller at a fixed ratio, as you earlier stated, I don't understand how this is possible.

Hm, if you look at it that way, I could say you're right and that it is not possible to maintain an "ideal" propeller speed.

What the engine computer does is to command a specific speed and manifold pressure for the currently set power lever position. The propeller governor would try and maintain this speed, and if the pilot changed the power lever position, it would try to maintain a different speed as commanded by the engine computer.

However, for lack of an infinitely variable transmission between engine and propeller, the engine computer would have to command a very high propeller-and-engine rpm in order to allow the engine to deliver the desired high power. This speed would be less than ideal for the propeller as it would be hit by a serious loss of aerodynamic efficiency in high-speed flight, especially at altitude, and you'd burn a lot more fuel for just very little more speed, but as this was the only way to keep the engine happy, there was no way around this "abuse" of the propeller in a less-than-ideal operating range.

Regards,

Henning (HoHun)


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## Juha (Apr 22, 2009)

A couple German comments on Bf 109 vs P-38 in North Africa/MTO from Jeffrey L. Ethell’s P-38 Lightning p. 21-22 in The Great Book of WWII Airplanes
Johannes Steinhoff, “…Bf 109 was still, perhaps, a little faster. But pilots who had fought them said that the Lightnings were capable of appreciably tighter turns and that they would be on your tail before you knew what was happening…” 
Oblt Franz Stiegler, 28 victories, JG 27, “P-38 could turn inside us with easy and they could go from level flight to climb almost instantaneously. We lost quite a few pilots who tried to make an attack and then pull up. The P-38s were on them at once. They closed so quickly that there was little one could do except roll quickly and dive down, for while the P-38 could turn inside us, they rolled very slowly through the first 5 or 10 deg of bank, and then we would already be gone….”

Juha


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## Soren (Apr 23, 2009)

The comment from Steinhoff is odd since he has said the exact opposite before. And even more oddly is that all German accounts I've ever seen mentioning the P-38 considered it to be easy prey.

But Ethell's has also been accused of making stuff up before so, take what is written in his book with a huge grain of salt...

Don't believe tall tales, let real life physics guide you


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## Soren (Apr 23, 2009)

Steinhoff:
_"The Lightning. It was fast, low profiled and a fantastic fighter, and a real danger when it was above you. It was only vulnerable if you were behind it, a little below and closing fast, *or turning into it*, but on the attack it was a tremendous aircraft."_


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## Soren (Apr 23, 2009)

LW pilots opinion:


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## drgondog (Apr 23, 2009)

Soren said:


> LW pilots opinion:



I know this opinion was widely held by many Luftwaffe pilots. Having said this I wonder how many were interviewed that fought against the post D-Day versions of the J-25s and L's.

The combination of dive brakes, manuever flaps and boosted ailerons really did transform this machine.

By and large only a few LW pilots in LuftReich engaged this ship, as well as remnants of JF77, 27, etc that were still fighting in the Balkans - and those that stumbled on 9th AF ground support missions.

The one intangible that really worked to the LW favor that was not mentioned is that is a very distinctive shape and easy to id from a long way away. At altitude the 109 pilot could often spot a 38 andmake a decision to fight or flee before the 38 was in visible range of a 109. Ditto on spotting a 38 from altitude while it is on the deck.

The intangible made it possible to achieve some initial tactical advantage before attacking.

In my research the P-38's in the 8th AF were by far the least successful against German fighters, the 9th better (but they had the late models) and the 12th/15th still better - perhaps because of better tactics... but the 8th AF ratio was respectable (~2:1 and we can always debate awards to claims) because the 479th had such HUGE success while it was flying the P-38J/L. The 55th, 20th and 364th were above 'even' but they also fought the H and early J's when the Allisons were blowing up, couldn't dive or roll well, and just were outflown.

It remains an interesting question and definitely has a 'break point' between pre J-25s and the rest of the war.


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## mkloby (Apr 23, 2009)

Soren said:


> Don't believe tall tales, let real life physics guide you



Soren - doesn't posting accounts of German pilots regarding the P-38 violate this statement you just made a few posts ago?

I tend to think that pilot accounts, performance data, and employment are all very important and to leave one out is ignoring part of the available information.


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## Soren (Apr 23, 2009)

drgondog said:


> I know this opinion was widely held by many Luftwaffe pilots. Having said this I wonder how many were interviewed that fought against the post D-Day versions of the J-25s and L's.



Yeah I can't answer that question  But Steinhoff only got the chance to meet them in the MTO, he had a very long period where he didn't fly, and when he started again it was in the Me-262 against the high flying bombers in 44.



mkloby said:


> Soren - doesn't posting accounts of German pilots regarding the P-38 violate this statement you just made a few posts ago?



lol, no, it just goes to show exactly why you can't blindly trust pilot accounts or opinions. If you want to know the true abilities of an aircraft then you need to trust in physics and the statements made by modern day pilots of the type.


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## Juha (Apr 24, 2009)

Soren 
I trust in physics but that doesn’t mean that I take too seriously long term (7 days) weather forecasts, even meteorologists who made them using supercomputers admit at least here that one cannot count very much on them. Even much more simple things for ex how certain amount of certain explosive effects known ferroconcrete structure isn’t all too easy to predict. So I don’t see why should place too much faith on rather elementary calculations on such rather complicated phenomenon as how an a/c behaved in turn.

And if you may enlighten me how a modern day pilot is better to judge behaviour of an a/c than a combat pilot who have had much more stick time on type, who had flown it to limits without restrictions nowadays in force, rightly so, on flying old and rare type of a/c or a test pilot who had found out the envelope limits of the type?

Juha


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## Soren (Apr 24, 2009)

Believe what you wish Juha, your odd comparison of aerodynamics with meteorology speaks volumes for me regarding how you see things.


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## Juha (Apr 25, 2009)

Soren
Meteorology is also a natural science based on physic and weather forecasting is in essence using complicated calculations based on numerous known variables and models based on long experience, much research and physical laws to predict what will happened in near future and a commoner can easily make his opinion on the results.

Aerodynamic is much more simple but for ex you are not professional aerodynamist or computer modeller and you very probably don’t have in your use anything near the computer power meteorological institutions have. And even if I don't play with aircombat simulators I would be surprised if all good games give same behaviour for ex Bf 109F-4 or P-38F-15 as it should be if the relatively simple (as compared to those made by a/c manufactures) aerodynamical modelling produces accurate results.

And still waiting the explanation why a modern day pilot is better to judge behaviour of an a/c than a combat pilot who have had much more stick time on type, who had flown it to limits without restrictions nowadays in force, rightly so, on flying old and rare type of a/c or a test pilot who had found out the envelope limits of the type?

Juha


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## Soren (Apr 26, 2009)

Juha,

Again believe what you wish.

As for the modern day pilots, they didn't fly the a/c 60+ years ago during a hateful war, so no memory loss no bias. THAT is why the accounts by modern day pilots are more accurate reliable. And "oddly" enough aerodynamics ALWAYS seems to support what the modern day pilots have to say, something which can't be said about 60+ year old accounts.

And about the meteorologists, sorry no bite, such an awful comparison.


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## Juha (Apr 26, 2009)

Soren
Now it is a bit different to ask today veterans oppinions than to look info from test reports from 40s or even info from what was written in 50s and 60s. For ex E. Brown has his notes to back up his memory, not that I always agree with his oppinions.

And believing that todays pilots had no bias is IMHO a bit naive. Opinions are always subjective, some more and even much more than others. And many were able to remain rather objective and analytical during the war. And as I wrote earlier, IIRC nowadays they don't use full power and had rather strict g-limits when they flew those old planes and not all the modern pilots had fighter pilot training.

Meteorologist comprasion was an answer to your 
Quote:"If you want to know the true abilities of an aircraft then you need to trust in physics"

IMHO rather naive sentence. Of course we trust physics but it isn't same as to trust results which were generated by computer models, more complex the phenomenon and less sophisticated the model are, less trustfull the results will be.

Juha


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## Juha (Apr 26, 2009)

And on the question of the poll, now closed. IMHO 109F-4 was the best fighter around when it was in production from May 41 to May 42. So IMHO 109F-4 was better than P-38F even in very late 42. But I must admit that I cannot remember much on P-38.

Juha


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## drgondog (Apr 26, 2009)

Juha said:


> And on the question of the poll, now closed. IMHO 109F-4 was the best fighter around when it was in production from May 41 to May 42. So IMHO 109F-4 was better than P-38F even in very late 42. But I must admit that I cannot remember much on P-38.
> 
> Juha



Juha - I would agree with you (and Soren) and all the others that voted 109F-4 over P-38 in 1942... and extend that at least through mid 1943 against all versions of the P-38F. 

If the introduction of manuevering flaps made enough difference in turn against to 109F (and early G-2) it would have to be in mid 1943 when the 38F-15 (all 221) was introduced, then followed with G. 

IMHO that would have been significant only in a sustained turn combat that the 109 chose to not perform a series of opposite rolls and finally reverse and escape. Turning combat is over rated but a nice advantage to have when you are forced into it when you lose all other options.

As good an airplane as the P-38 was it never fully realized its potential until the J-25 finally ironed out the altitude dive compressibility issues with dive brakes and improved roll/turn capability with boosted ailerons and manueveing flap combination. That would be mid 1944 - for first combat introduction


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## Juha (Apr 26, 2009)

Hello Drgondog
have You idea why some US a/c had to went fairly long in alphabetics before they became combat ready? P-38, P-39, then a number which never got into combat service in USAAF, excluding P-40 which in any case was based on P-36, come into mind. Spit, Hurri, 109 and 190 seems to became combat ready earlier in their career.

Juha


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## drgondog (Apr 26, 2009)

Juha said:


> Soren
> Meteorology is also a natural science based on physic and weather forecasting is in essence using complicated calculations based on numerous known variables and models based on long experience, much research and physical laws to predict what will happened in near future and a commoner can easily make his opinion on the results.
> 
> *Weather forecasting, IMHO, is the toughest physics problem dealing with Energy/Mass Flow Balances.
> ...



Juha - make your own determination regarding how simple modern day aero is but I rank the Full blown/all mauever Flight Mechanics model with VSAERO type 3-D Fluid Mechanics models and Propeller Model and perhaps even complex boundary layer/Chaos theory based subroutines as 'fairly complicated' - and approaching the Earth/Sun model Navier Stokes solutions in complexity.

What we see as simple in the forums is reducing the Aero properties to several coefficients, extracting initial data from sources, and then leaping away into simplified linear equations to a non linear problem.

Having said this, most of the modelling done here is close enough to illustrate approximations to different states in the manuevering, and there are no such 'simple' analogues to predicting weather.. as you noted.


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## Juha (Apr 26, 2009)

Hello Drgondog
I know that meteorology was a rather extreme case, I choose it partly because of that and partly because of, even if my main subject in university was World History, I also studied Geography and so learned something on climate and got some info on weather forecast models of the day, also one of my ex-girlfriends studied Meteorology. 

I agree that VSAERO type models are rather complicated but I doubt, and can only doubt, a bad thing in these net discussions is that one cannot really know with whom one was discussing, that Soren used so complicated model in his calculations. 
And even rather close approximations can be misleading because deviations can be in opposite directions.

Juha


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## drgondog (Apr 26, 2009)

Juha said:


> Hello Drgondog
> have You idea why some US a/c had to went fairly long in alphabetics before they became combat ready? P-38, P-39, then a number which never got into combat service in USAAF, excluding P-40 which in any case was based on P-36, come into mind. Spit, Hurri, 109 and 190 seems to became combat ready earlier in their career.
> 
> Juha



Good question. In the case of the P-38 (the most extreme example) there were a lot of thorny issues caused by a non traditional approach by Lockheed to achieve very high performance very early in its design gestation. 

(Housing turbo superchargers in a boom, intercoolers in leading edge of wing, lack of fuselage filets to improve drag - but finding significant wake turbulence and flutter in the elevator, combined with lack of knowledge regarding compressibility leading to confusion regarding transonic vs flutter effects, combat experience demontrating that an effective fighter in ETO must be able to compete with LW variants in manuever combat rather than serve in interceptor range, etc.

Then combine all of that with the loss of the prototype before WWII started and setting back the flight test back two years because the prototype was hand built (no production contract).

The P-47 and P-51 did not have such great leaps to hurdle and consequently had far fewer significant dash number/model changes. Ditto F6F and F4U.

Is this what you were asking about?


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## Juha (Apr 26, 2009)

Hello Drgondog
Yes. IIRC USAAF considered P-39D as the first combat ready version of the type, and as you wrote P-38 was an extreme case. P-51 was after all first ordered by British and already P-51A was combat ready. IIRC P-47C was the first model used in combat but if we looked its predecessor P-43 one maybe can say, that it also had rather long development history.

USN got its fighters with shorter gestation periods, IIRC and had fewer misses. F5F comes into mind. 

Of course one reason might be different procurement policies, and maybe the large number of "duds" simply followed from large number of a/c manufactures and from the fact that late 30s many countries looked for new fighters and US a/c manufactures saw fighter business lucrative and USAAF gave their prototypes P numbers.

Juha


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## Juha (Apr 27, 2009)

I did some checking on those projects that didn't produce service fighters. Many of the abandoned projects were attempts by Curtiss to produce a new fighter to USAAC/USAAF. XP-42, -46, -53/60 (up to E version), -62; then there were those unconventional planes XP-54, -55, -56, -67. One cannot accuse USAAC/USAAF being too conservative. US must to have used a lot of R&D resources to all those projects, but fortunately it was a rich country with powerful industrial base. Then there was lightweight XP-77 and the “choose your parts and put them together“ P-75, even if the idea didn’t come true in the end product. Of course there were others, for ex Lockheed’s XP-49 and -58. 
Purely export projects were P-64, -66 and CW-21


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## drgondog (Apr 27, 2009)

Juha said:


> I did some checking on those projects that didn't produce service fighters. Many of the abandoned projects were attempts by Curtiss to produce a new fighter to USAAC/USAAF. XP-42, -46, -53/60 (up to E version), -62; then there were those unconventional planes XP-54, -55, -56, -67. One cannot accuse USAAC/USAAF being too conservative. US must to have used a lot of R&D resources to all those projects, but fortunately it was a rich country with powerful industrial base. Then there was lightweight XP-77 and the “choose your parts and put them together“ P-75, even if the idea didn’t come true in the end product. Of course there were others, for ex Lockheed’s XP-49 and -58.
> Purely export projects were P-64, -66 and CW-21



All true Juha. On the USN side I would offer a couple that tend to fit long gestation period even if not with quite so many production release versions beforehand - the F4U and SB2C took 2.5 and 3 years respectively from first flight before deemed combat ready. The P-47C was fighting with 56th/78th and 4th FG in two years from first flight.

Part of the problem with the P-38 and the P-39 is that the combat role and mission envisioned was not what they confronted and no ready replacements for the new role was available. The US "brought what they had" and modified for a period of time to meet a broader range of needs.

Germany had a clear vision regarding the type of war they were going to fight, as well as the tactical doctrine so I think they did a better job in 1938 and 1939 setting specifications.

Both the P-47 and P-38s were designed as bomber interceptors - never as strategic escorts/air superiority fighters - but they evolved. 

Had the Merlin engine been available to US in 1939 as a foundation for in-line high altitude/high performance aircraft it would have been interesting to see how the US designs would have looked like in 1941. The Mustang would have been air superiority combat ready in 1942, US airpower would have been effective in early 1943 and the LW would have been forced to respond to the threat by accelerating the Fw 190D/Ta 152 and the Me 262.

While the P-51B would have been superior to the P-38E through J and all versions of P-40 and P-39, I doubt that the impact would have been as great in PTO for all USAAF initiatives... and the USN would have had the same types no matter what.

The one intersting question would have been the USMC if the 51B available in flight test during 1941 and combat ops by Pearl Harbor when the F4U was still a year away from serious consideration in the Solomons... No question that the 51 would have been far more effective on Japanese bombers (given radar) a long way out from Guadalcanal compared to F4F and P-40 and P-39.

As to the eternal performance debates I am in agreement with you. The preliminary design phase of aircraft is loaded with a range of mathmatically derived (and simplified) relationships for Lift and Drag. Attempts have to be made to reduce conceptual wing body designs to project performance.

The equations often presented here are correct for such studies - but only relate to stable bodies in linear motion, immersed in a perfect fluid, in linear regions. 

The Dynamic 'Turn' model is an approach to extend the above principles and assumes symmetric forces on a curvelinear wing/body path... and assumes that at each point in the turn that the Free Body Force diagram applies equally to a banked wing/body system that is in fact experiencing asymmetric forces and spanwise flow across most or all surfaces with significant changes to lift and drag - and does not take into account turbulent flow, boundary layer separation, elastic properties of the airframe, etc.

Reality sets in during flight tests....


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## renrich (Apr 27, 2009)

A German pilot called the P38 vulnerable. If one looks at combat film from the LW showing an attack on a P38, one can see that the same thing that made it easy to see and identify made it vulnerable. It was a big AC and there was a lot of vulnerable spots to shoot at. Throw some lead it it's general direction and it is much more likely to hit something on a P38 than on a single engined fighter.


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