Bf109F vs P-38F

[Soren]

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.

 

[syscom3]

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.

 

[drgondog]

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.

Here is what you said to start this debate

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.

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 ????

Pretty easy actually Soren. Do you know the difference between Limit Loads in a Flight Manual and Design Ultimate (from which the Limit Loads are mathmatically derived?) - I didn't think so! - Did you see the dialogue between Kurfurst and me on this subject - just below yours?

FYI the Design Ultimate Load factor for the P-51B and D was 12 (g) for 8,000 pounds gross (pg 119 "Mustang - History of the P-51 Fighter", the ultimate for H was 11 .

As Kurfurst pointed out he had seen 10.8 Ultimate (not Design Limit) for a 109 and thought he had heard 13.. but you haven't substantiated either by docs or source... on the subject of LW data - I trust what I've seen from Kurfurst. I might trust you but you never produce any in these debates


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 !!!

Show me a Me 109E, Me 109F or G with a.) wing bomb shackles or attach points for 1 -150 Gallon Ferry Tank (1030 pounds including weight of tank and 135 gallons of fuel) plus six .50 caliber machine guns plus 940 rounds of 50 caliber per wing ??? I'm sure you must have vast amounts of data and pics to show such - right? or just pick the 110 gallon combat tank at 975 pounds plus the 50's plus the ammo.

so operational pics of any of those 109s with 550 kg bombs under each wing and 2 x 20mm internal guns or Gondolas would suffice to show me I am incorrect?

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.

If you will go back to you comments, You questioned his manhood in the speeds (IAS) that he felt was a limit dive for the 109... based on his fear of the leading edge slats.

If you will go up to the links for combat encounter reports I just posted you will note that three common factors exist - a.) 600-650 IAS chasing the 109 in the dive, and b.) either the 109 was caught and shot down in near vertical dives, or c.) the 109 disintegrated w/o shots being fired.

So, if you trust actual and experienced P-51 pilots check out the Encounter Reports read on!- If you want to correspond with American Aces on this subject I will introduce you on the condition that you apologise if they say things you don't like - publically, on this board.

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 ???


Soren - I assume you either took geomerty or Vectors? If so, read on.

Draw two points at same level (scale 1000 yards apart) - take the leading point (109) and construct a maximum speed dive angle from the leading dot.. (yes, AWAY from the P-51) draw the pursuing vector to an intercept point..

If you are successful in reproducing this picture, please ponder two facts.

Fact A - the 109 takes a maximum speed dive angle - unless he has a death wish and is stupid. (I will assume he is smart)

Fact B - the pursuing Mustang either has to travel 1000 yards and then dive after the 109 to get the same angle of dive.. or the Mustang must take a shallower dive angle and a longer intercept vector... meaning a much higher speed to intercept or a very long distance at a higher speed..

Got this, so far?

Now go up to your statement and see if you make sense

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!

See above, then below-

First entering the high speed dive has nothing to do with structural integrity - the pullout does

Second - the diving fighter will reach an adequate pressure density altitude sooner, in which cases compressibility factors dimninish and pilot can gain control... so unless the design is flawed the fighter reaching lower altitude the first will regaing normal control first. is this understandable?

Third - you STILL have not submitted any fact(s) demonstrating that the Me 109 gould take higher G forces

I on the other hand, in two posts above, (particularly in the second one) have submitted 10+ in various encounters with diving 109s, at high speed, with high G pullouts or blowing the 109 up, or watching the 109 disintegrate with no hits - just manuever.

Last you have not refuted the specific reference I submitted to you of the 109F folding it's wings in both dives and high G turns(Franz Nowarra - pg118)

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.

Facts Soren - did Rosarius Zirkus perform a test that you can share with us to demontrate this claim came from a bright, shiny place? Did anyone on our side do a test to prove this notion of yours? Facts - those would add to my education but your saying it so doesn't.


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.

That is of course the reason why so many 109s were chased and caught and killed - right? because the 51 was 'unsafe' or 'less safe'? How safe was the diving 109 that got killed??


Anyway keep on the backpaddling Bill

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

 

[drgondog]

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.

Facts Soren - did Rosarius Zirkus perform a test that you can share with us to demontrate this claim came from a bright, shiny place? Did anyone on our side do a test to prove this notion of yours? Facts - those would add to my education but your saying it so doesn't


Anyway keep on the backpaddling Bill

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

 

[drgondog]

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 have sources which prove either of the statements? What causes you to 'doubt' 7 G in the Franks G-suit? How many accelerometes or strain gauges were a standard feature on any fighter to lead you to that conclusion - And at the end of the day it only matters if the G suit slows the blackout or speeds the recovery - and it did both better than no G suit.

Anyway keep on the backpaddling Bill

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

 

[Kurfürst]

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.

 

[drgondog]

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.

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?

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

I will be interested. I know the design ultimate load was 12 for the B/C/D but I have not been able to determine the actual test to destruction loads on the wing. I know it passed the carrier tests for both wing and arresting gear but haven't got the data on that either

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.

Agreed - and I thionk I made the comment that they (as well as Soren's) Encounter Reports don't prove much.. my only reason was to produce documented reports that rebutted Soren's extracts from a Tommy Hayes Encounter Report - I din't truly understand what his point was so I collected several that a.) demonstrated a 51 catching up, and b.) a 51 chasing and the 109 breaking up to see what point he was trying to make re: demonstrated structural integrity

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.

Agreed... but actually I do have sevaral reports on the wheel uplock as well as high speed (diving) slow roll failures - And I know of two TO's which addressed both the wheel cover uplock and the strake/dorsal fin attach instructions to address danger of high speed slow roll on the 51 Tail. The > .8-.82 Mach yaw issue was never completely solved even with H model tail

I personally never approached 480IAS in a dive much less the flight envelope limit 505 IAS but one heeluva lot of 51 jocks exceeded 600-650 IAS in dives per the Encounter Reports - who knows what actually occurred- and all my flights in a 51 were partial loads - so I make no personal claims in this argument

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.

Actually Kurfurst - those are all bona fide Encounter Reports of pilots that scored on 109s, 190s and 262s - they fit the profile of b. above. No more or less - it even has one of my father's reports - no glory - just simple "this is what happened" - what would you suggest Mike do with respect to 'other' reports?

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.

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

 

[Kurfürst]

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.

 

[drgondog]

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

 

[drgondog]

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?

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.
Kurfurst - the Gondola would obviate the need to cut away and then reinforce the main spar internally - which would pose (solvable) problems that would add more weight than the gondolas.

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 then doubted - but it was close to real issue. 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 ?? 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.

Did they state the Limit Diving Speed as 850mph -above- ??

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 what 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 design 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.

That is classic wing design - but the main spar of 1he 109 is at approx 40MAC whereas the P-47 and P-51 and P-38 are at 25%MAC or where the aerodynamic center of lift is -- therefore no torque on the 'torque box' due to lift - which is not the case for the 109.. The 51 'torque box' starts with the 25% main spar, the 109 starts aft of CL as well as main spar

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).

All of those measures would be taken because of concern for both bending and torsional failures - there was no such design modification for a 51. Adding thickness to aluminum plate on top and bottom of spar adds 'effective cross section to spar caps' to take out more tension in bending as well as distributing shear loads.

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.

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?

 

[Soundbreaker Welch?]

Not a good idea, I agree.

 

[HoHun]

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)

 

[Vincenzo]

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

 

[HoHun]

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)

 

[Vincenzo]

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

 

[HoHun]

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)

 

[Vincenzo]

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

 

[HoHun]

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)

 

[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

 

[HoHun]

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)