Corsair vs. BF 109G,K or FW 190's

[drgondog]

Hi Bill,

Things are moving toward using computer simulation exclusively. There have been quite a few advances in computer algorithums for solving the Euler and Navier Stokes equations for example. It is still the realm of the big time firms though.

The little guys are still using saw horses and sandbags.

Do you have a copy of David Lednicer's computational fluild dynamics evaluations of the Spitfire, P51, and FW190 series? He used Vasero to analyze the designs with some very good agreement and insight. I can give you a copy if you do not have it already.

All the best,

Crumpp

Crumpp - I do not have a copy and would love it if not too much trouble..

As to solving Navier Stokes - it was only a figment of imagination in context of IBM 360/50 and CDC 6600 computers of the day in the airframe biz when I was dabbling. I actually thought about doing my Doctoral Dissertation on modelling cloud formation which would have required heavy doses of NS.. but stopped short of pursuing when 'family count' built up.

Now that I am retired I have started to investigate pursuing the PhD (Who knows why? LOL)

Thanks, as always

 

[AL Schlageter]

LoL, read the report before making stupid statements like that AL !

The report is about structural issues, it has NOTHING to do with the issues surrounding the carburators.

You read what was said Soren.

"This is tactical advise to the RAF Spit pilots, how to get around the negative G problems with a roll-and-dive manouvre."

This was the maneuver (roll and dive) done to get around the carb cut out problem.

The only way one could get NEG G force was if an outside maneuver was done for it to be structural.

Now what is this about stupid statements?

 

[Crumpp]

The excerpt appears to warn Spitfire pilots against asymmetrical loading of the airframe during the maneuver.

 

[Soren]

Exactly Crumpp, however AL seems unable to figure that out.

About the stalling speeds, do you have the figures for the FW-190 P-51 ?

 

[16KJV11]

Exactly Crumpp, however AL seems unable to figure that out.

About the stalling speeds, do you have the figures for the FW-190 P-51 ?

For what it's worth:
Wikipidia has the P-51D's stall speed at 100 MPH and the FW 190 prototype stall speed at 127 MPH.

 

[Hunter368]

The excerpt appears to warn Spitfire pilots against asymmetrical loading of the airframe during the maneuver.

Sorry (Soren), but Crumpp can you explain that a little better.......I am not too proud to say I don't understand what you are saying.

What Al is saying makes sense to me, but then again I have no experience in the field. I need to dummies version of what you are saying and what Soren knows already.

 

[Glider]

The excerpt appears to warn Spitfire pilots against asymmetrical loading of the airframe during the maneuver.

What I find interesting is what it doesn't say. It doesn't say not to do the maneuver, it doesn't say do not do it above a certain speed.

What it does say is that it should be practiced, which is fair enough and that it can be carried out at high speed.

Just a question but would the leaf spring design of the Spits wing spar help or hinder as it gave the structure some 'give' in its design.
Part of me says that it would hinder by making it more liable to twist, but part of me says that it would help as the plane would depart from normal flight without structural failure enableing the pilot to recover.

Any ideas on this welcome.

 

[Glider]

PS one thing the thread is about the later 109G which was heavier than the F and this wouldn't have helped in its ability to take stresses.

 

[Soren]

For what it's worth:
Wikipidia has the P-51D's stall speed at 100 MPH and the FW 190 prototype stall speed at 127 MPH.

Hehe 127 mph is not the stall speed, the landing speed was lower than that. The stall speed of the P-51D with flaps and gear retracted is 109 mph IIRC, and the FW-190 around 102 - 105 mph under the same conditions.

 

[Kurfürst]

Stress factors of the late 109G were practically the same as the 109F. Dive limits of the 109K were even increased by 100 km/h.

 

[Soren]

The new wheel covers and retractable tail-wheel undoubtedly allowed this increase in the dive speed limit. At 850 km/h the K-4 has the same dive speed limit as the FW-190.

 

[AL Schlageter]

The new wheel covers and retractable tail-wheel undoubtedly allowed this increase in the dive speed limit. At 850 km/h the K-4 has the same dive speed limit as the FW-190.

Dive limits 109G
Up to 3 km (9,842 ft.) 750 km/h. (466 m.p.h.)
At 5 km (16,404 ft) 700 km/h. (435 m.p.h.)
At 7 km (22,965 ft) 575 km/h. (357 m.p.h.)
At 9 km (29,527 ft) 450 km/h. (280 m.p.h.)
At 11 km (36,089 ft) 400 km/h. (248 m.p.h.)

So the 109K could be dived to 528mph under a height of 3km (9845').

No Soren, it is you is who is having trouble. Now if Kurfurst had said,
"care has to be exercised with the roll-and-dive maneuver to get around the negative G problems "
instead of
"how to get around the negative G problems with a roll-and-dive maneuver."

Do you see the difference?

Where is the rest of the report? Selective editing?

Btw, when was the thread title changed to Spitfire vs. BF 109G,K or FW 190's

I checked out your site Kurfurst and could not find the following. Why is that?

1.)Boost 1,8ata with B4 fuel
Reason for the meeting were the problems in "field" and at the serial production facility "Genshagen" because of the "white flame" effect during the use of the
Higher output. First it is shown by Hr. Dr. Scherenberg how the "white flame"
followed by burned pistons, develop. Because of the results of the engine knocking test the lower quality of the fuel is the main reason for the problems.
DB has allready solved the problem with adjusting the ignition timing by 5°(???) .
This allowes the use of "Sondernotleistung" and the 1.45 and 1.80ata settings.
But because of later ignition , 50PS are lost during the "Sondernotleistung",
Where the 1,45 ata setting doesn't lose power.
DB although mentions the problems with the bad fit of the valvesitrings or
the plug thread , that where reasons for the glow-ignition too. But because
of improovments in the production these failurs are said to be canceled.
All agreed and the decision was done, that all engines should get the new ignition time. The lose of power is not so critical. But, because of hints from DB (DaimlerBenz), there should be test flight with 5 planes within all alts, but especially above rated alt, to get knowledge about the power loose above rated alt.

END SHEET ONE

This will be done at II/JG11. It is asked, if the ignition timing can be set on old value
if better fuel quality is back. Answer is delayed till it is for sure that only better fuel is used, and if it is shown, that later ignition does have no influence on the planes perfromance. DB mentions that the later ignition point although is better for the plugs that have a thermal problem at all.
It is mentioned too, that the performance lose will be decrease with increasing engine run time , means with less oil lose. It indicates too, that new engines with less oil usage are better in performance than the ones with at first high usage and the lower usage of oil. From the troop should be taken 1 engine with 15-20h for oil consumption and performance tests to be done in Genshagen. Because the b4 fuel is mostly used in the east, the order for the new ignition point/time should get out asap by…

2.)1.98 boost with c3 fuel
the first report shows, that the test with the 1.9, and 1.98 boost had negative results.
Then a telegram from Rechlin was shown (they tested 4 engines) that criticized the
clearing of the Sondernotleistung by Gen. Ing. Paul direct from the company to A.Galland bevor sufficient tests were done. Rechlin although defend themselves, that
they did NOT give the new boost free for the Troop. (looks like some thought they did). DB on the other hand shows their positive test results for the 1.9 , 1.98 usage.
They say, that the clearance for the 1.98 boost was given with the same TAGL (?)
(think a kind of order) as the 1.8 ata boost was cleared..both on the same day!.

SHEET THREE

It was then decided (after hearing all the reports) than currently only II/JG11 should test the 1.98 boost and that the 1.9ata engine test should be finished when the engines failed. (so no more test after them). The JG should then only get 1.8 ata engine supplies. Heavy punnishment is threaten when this order is not followed. The 1.98 clearance decission may only come from department 4 of general staff.
It is suggested that some recon planes should be equiped with 1.98 boost. Decission was not done. To disburden the current 1.98 and 1.9 engines it is suggested to give them the new ignition time too. So, all engines flowen with the sondernotleistung will
Be set to the new ignition point/time.

The JG's in field complain about the plug failurs. Especially in the last time the number of failurs increased. DB reports about improoved plug modells and better
quality control e.g. with x-ray controlling. Again DB points out that the cooling of the
109 is insufficient and wishes that the LW will solve this problem asap. This was mentioned by Gen.-Ing Paul and arrangements where done instandly.
DB points out that the performance of the "cell" (fuselage/wings) is extremely bad,
and even worser J. It makes no sense to increase the power output of the engine when on the other side the plane quality is decreasing dramatically. Is is reported that a coparison of a 109 with a mustang was arranged for Mr. Sauer, but he failed to come.
The result of the comparison was, spoken of produktion quality only, shocking
for the 109.

 

[AL Schlageter]

Who has a drawing showing the construction of this box spar on the 109? I can only see an I-beam type main spar.

 

[Crumpp]

Crumpp can you explain that a little better.......I am not too proud to say I don't understand what you are saying.

An example of assymetrical loading is when you combine both aileron input and elevator as the memo recommends. It also reminds the Spitfire pilot that doing so significantly reduces the amount of load the aircraft can safely handle.

Asymmetric aerodynamic loads such as combined rolling and pitching reduce the maximum airframe load allowable by perhaps 30%.

Fly real fast

All the best,

Crumpp

 

[drgondog]

Who has a drawing showing the construction of this box spar on the 109? I can only see an I-beam type main spar.

AL- IIRC, the main spar was around 45% chord, and supplemented by a leading edge "C" box and another spar at the flap intersection point on the chord. The 109G wing was stiffened over the 109F by increasing the skin thickness over main to aft spar.

Anectdotally (I haven't seen the reports) this solved the high G turn wing failures experienced by the 109F.

Anecdotally again, I have seen several references to both 109F and G and Spit (through XII) control reversal issues due to torsion at tip caused by aileron deflections at high speed.

Kurfurst - that was a nice report from the Brits - but would add that neither flutter nor aeroelasticity were 'sciences' during WWII - particularly in regions of compresssibility.

Having said that, the ability to calculate limit and ultimate loads in symmetrical conditions was pretty good as long as the pressure distributions were well understood.

In the case of a P-51 in a .78-81 dive the concept of the ammo door 'bulging', as stiff as it originally was, and creating a locally higher cambered, thicker wing came as a "suprise"

That is why, as much as I have enjoyed the analytical discussions, that I tend to fall back on wind tunnel and flight test to evaluate the 'real' from the theoretical.

I was delighted to see reports of VSAERO computer modelling recently which showed the pressure distribution comparisons between P-51, Fw 190A8 and D-9 and Spit IX (and compared to wind tunnel results).

Computational aerodynamics has come a LONG way since I was practicing and would have been very useful in improving all the designs.

 

[drgondog]

Hehe 127 mph is not the stall speed, the landing speed was lower than that. The stall speed of the P-51D with flaps and gear retracted is 109 mph IIRC, and the FW-190 around 102 - 105 mph under the same conditions.

The zero sink rate flight speed of a clean 51D is about 110 IAS - which means at that speed it loses no altitude in level flight.

The Stall speed - clean- is about 80 +/- IAS.

The 51 typically rolls slowly to right in a level flight stall and immediately recovers (if you have altitude) by simply letting go of the stick.

 

[Crumpp]

The 109G wing was stiffened over the 109F by increasing the skin thickness over main to aft spar.

Hi Bill,

Excellent point. As a former structure guy, I am sure you will agree with the following and is exactly why you made the point on the skins.

It is common in these type of discussions to look at design change and make assumptions that frankly cannot be made.

Everyone,

The German duralumin alloy had a lower cupric content than the US duralumin. This meant is some ways, the German duralumin was stronger but in other ways weaker.

Generally speaking the German duralumin had a higher tensile strength and much better resistance to corrosion. The US duralumin had a higher shear strength and was more vulnerable corrosion.

The German construction also relied on thicker skins. In some places, the FW-190 wing skins for example are 2cm thick.

Point is that there is little to choose in the results. Both sides aircraft construction resulted in airframes which had the same ultimate load factors. The construction techniques reflect the base materials chosen for the airframes.

Trying to compare strengths based on the shape of the I-beam is not going to get anyone very far.

It is a leap of logic that cannot be made given the facts behind the engineering.

All the best,

Crumpp

 

[davparlr]

My reference show the P51 D with a sea level vmax of 367 mph, the P51B was slightly faster at SL. The F4U 4 was fastest of all at SL(US fighters) with Vmax of 380 mph. Same reference shows the P51D is introduced into the 8th AF in March of 1944. Same reference shows F4U4 could climb to 20000 ft in 6.8 minutes. Another reference shows the FW190D9 took 7min 6sec to climb to 19685 ft. The F4U4 was a significantly better climber.

In May, 1944, both North American estimates and AF flight test show that the P-51B with 150 grade fuel, pulling 75" Hg, could exceed 380 mph at SL (without wing racks).

http://www.wwiiaircraftperformance.org/mustang/na-p51b-150grade-level.jpg

http://www.wwiiaircraftperformance.org/mustang/p-51b-24771-level-blue.jpg

 

[drgondog]

Hi Bill,

Excellent point. As a former structure guy, I am sure you will agree with the following and is exactly why you made the point on the skins.

It is common in these type of discussions to look at design change and make assumptions that frankly cannot be made.

Everyone,

The German duralumin alloy had a lower cupric content than the US duralumin. This meant is some ways, the German duralumin was stronger but in other ways weaker.

Generally speaking the German duralumin had a higher tensile strength and much better resistance to corrosion. The US duralumin had a higher shear strength and was more vulnerable corrosion.

The German construction also relied on thicker skins. In some places, the FW-190 wing skins for example are 2cm thick.

Point is that there is little to choose in the results. Both sides aircraft construction resulted in airframes which had the same ultimate load factors. The construction techniques reflect the base materials chosen for the airframes.

Trying to compare strengths based on the shape of the I-beam is not going to get anyone very far.

It is a leap of logic that cannot be made given the facts behind the engineering.

All the best,

Crumpp

Crump - Agreed with one minor departure.

As a structures guy I want the main spar as close as possible to the Center of Lift- nominally at 25%, so that I am not adding a Lift Force to the existing Moment by moving the main spar, to say at 45% Chord, away from Center of lift.. like the 109.

In effect that 109 wing was a small, eccentric beam (leading edge) at zero chord, big beam and skin at 45% and another small beam at flap line. So the Center of Lift was approximately mid way beteen leading edge (small beam) and main spar with a big freaking hole in the bottom in the worst place - called a wheel well.

I can make that wing stiff in bending by increasing the structure (and weight) with thicker skins to give me more cap size for tension and compression (and shear) but as I get further out toward the tip, building a torque box with decreasing sectional thickness is a problem and the simple lift in level flight is creating an additional torque to aero moment.

I would love to see exactly what the analysis looked like... particularly for the asymetric load of a turn in a diving pullout

 

[Glider]

Certainly there were warnings to German pilots that if a yaw developed in a dive the wing tips tended to come off. Instructions were given that the wing tips should be checked so it would appear that the weakness is one that would build up over time, as opposed to one off catastrophic failures