Bf109F vs P-38F (2 Viewers)

[Glider]

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.

 

[drgondog]

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.

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.

 

[drgondog]

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?

 

[FLYBOYJ]

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...

 

[Kurfürst]

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.

 

[Glider]

Thanks everyone for the details, appreciate it.

 

[Soren]

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.

 

[Glider]

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?

 

[Soren]

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."

 

[drgondog]

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.

Simply stated, no fanfare - BS Soren

The 109 could carry two 110 gallon (750 pounds each) external fuel tanks plus 92 gallons each internal fuel plus 3 .50 Caliber machine Guns plus 1100 rounds of 50 caliber ammo? ROFLMAO - you are kidding aren't you? Oops - you're NOT? Which one of the 109s would you propose to compare 'wing loads' ?? against any version of a 51B/C/D

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.

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

 

[FLYBOYJ]

"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

 

[FLYBOYJ]

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...

 

[drgondog]

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.

And you know he was 'wrong' - how? Relate your time and experience with his to give you a respected opinion? What can you be thinkin'???

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.

Note the 30 seconds of search results on Encounter Reports that directly contradict you

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.

Note the 109 had more than a 1/2 mile lead, entered the dive and accelerated before the 51 did, and reached an altitude where he could regain control before the chasing Mustang did. It doesn't note any specific circumstances under which the 109 'got away' - was there cloud cover? did he lose sight of it? what?

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. "

See Above - and Below for many examples that make your thesis nearly silly

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.


[I]Tommy Hayes was a great combat leader, but neither a/c were remotely close to 'sound barrier - he simply reached compressibility - and at airspeeds exceeding .75 Mach the 51 at the red line - but capable of .82.

It was at this airspeed that the 51 experienced yaw forces which got stronger and more dangerous. Further he didn't say how far out in front the 109 started and as the first ship to reach a density altitude, it would start to pull out before the Mustang would

Both pilots took measures to slow down, but to Hayes' astonishment, the Me-109 was the first to pull out of its dive.

See above and below

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."[/I]

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.

 

[pbfoot]

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

 

[Brain32]

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

http://www.spitfireperformance.com/m...r-8april44.jpg

http://www.spitfireperformance.com/m...r-8april44.jpg

http://www.spitfireperformance.com/m...e-19july44.jpg

http://www.spitfireperformance.com/m...l-11sept44.jpg

http://www.spitfireperformance.com/m...er-16aug44.jpg

http://www.spitfireperformance.com/m...-29april44.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...

 

[Kurfürst]

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.

 

[FLYBOYJ]

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.

 

[drgondog]

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

 

[drgondog]

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

 

[Soren]

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