Performance of the Fw 190A on the Deck?

[George Hopp]

Totally non-technical I'm afraid. But the chart by M. Degnan is a bit misleading in showing the P-47D of March 1944 when the chart gives the time frame as 1943. By the time of the P-47's tests there would also have been the P-51B in service in addition to the new generation of 605AS-powered 109s. And, since the B-17 is mentioned it would have been interesting to see its performance also.

Anyway, an interesting thread.

[Harri Pihl]

Originally Posted by Crumpp

The only way to judge the affects of weight is to hold a constant, adjust weight, and measure the results.

In the polar analysis, the weight is adjusted and the answer to the question in hand is calculated directly adjusting the Cl accordingly to keep thrust and drag balance.

Originally Posted by Crumpp

That is the basic scientific method and is generally accepted for aerodynamics and applied physics.

The polar analysis is the very basic method of performance analysis, it can be found from any good aerodynamics book. The formula you used is based on the polar analysis but limited to one given Cl (or AoA).

Originally Posted by Crumpp

Otherwise we miss the forest for the trees.

Using the same terms; with the polar analysis we can see the forest and the trees, with your formula we can see only the trees.

[Crumpp]

But the chart by M. Degnan is a bit misleading in showing the P-47D of March 1944 when the chart gives the time frame as 1943.

I think at the time that was the only P-47 data available. The chart was constructed several years ago IIRC.

Good to see you George, BTW.

All the Best,

Crumpp

[Graham Boak]

You are right, I haven't been an Aerodynamicist for twenty years. I had worked on performance aerodynamics for the previous nineteen. Like riding a bicycle, I believe you said? Some things you don't forget.

You want a more academic source. I offer you "Design for Air Combat", by Ray Whitford C.Eng MRAeS. Page 13, "Trailing vortex drag typically represents 75% of the total drag in maximum sustained manoeuvre flight.........only 5 to 10% in the low altitude high speed flight." Trailing vortex drag is his term for induced drag. This value is for modern combat jets: for WW2 fighters at about half the speed the induced drag proportion will be higher, about 10-20%.

You might also wish to consider his Fig 16, where the 1g and 4g flight envelopes for the F-5E can be seen to be very close together, at max speed at sea level. That's very little change for a 300% increase in weight. You can see why the change in level speed due to a 5% increase in weight is regarded as insignificant.

In combat, every little helps, of course. In this sense, insignificance can be claimed as the effect is less than the variation to other causes such as surface finish, fit of panels, age of engine, excrescence standard. And indeed, pilot handling. A mis-set trim will create more drag than a couple of mph. If the radiator shutters are set too open they will create more drag.

Re comments from actual pilots: They were referred to much earlier in the thread, at least indirectly. Every kill of a fleeing Jabo proved that other fighters could outrun an Fw 190, so the basic statement was untrue. Yet many Fw 190s did escape their pursuers, and the question how such differences arose led to discussions of basic aerodynamics.

Which I suspect has gone far enough now.

[Harri Pihl]

Originally Posted by Graham Boak

You want a more academic source. I offer you "Design for Air Combat", by Ray Whitford C.Eng MRAeS. Page 13, "Trailing vortex drag typically represents 75% of the total drag in maximum sustained manoeuvre flight.........only 5 to 10% in the low altitude high speed flight." Trailing vortex drag is his term for induced drag. This value is for modern combat jets: for WW2 fighters at about half the speed the induced drag proportion will be higher, about 10-20%.

Ah, this is where the things get complicated. Generally the polar of the aircraft stays pretty unchanged up to mach 0,4-0,5. And at low altitude WWII fighters reached this kind of speeds, 600km/h being slightly below mach 0,5 at sea level at standard atmosphere. So simple relations based on assumption of constant polar work pretty well for this kind of analysis.

However, around Mach 0,5 the polar shape as well as the zero lift drag coefficient start to change so the formulas intended for slow speeds and constant shape of the polar work poorly for the jets which can do around Mach 1 at sea level. In other words, induced drag proportion of the jet aircraft drag does not prove much here because these fly at speeds where the drag and lift relations are very different and not constant.

IMHO the best way to show the limitations of constant AoA analysis is to rewrite L/D ratio as:

L/D = Cl/Cd = Cl/(Cd+Cdi)

In other words there is basic polar analysis hiding behind, the Cl and Cdi are just assumed to be constant. And that is a wrong assumption for this particular case.

[Boomerang]

Art and Crumpp:

Thank you for the observations based on actual experience.

I found it interesting that your threads gave quite different perspectives on the ability (or otherwise) of the Fw 190A to outrun Allied fighters on the deck.

Variations in the performance of individual aircraft of the same type and possible reasons for such variations were themes earlier in the discussion. This made me recall (another!) quote from The JG 26 War Diary Vol Two: '...was chased and caught by Lt. Paul Jasper, whose P 47D-16 was 15-20 mph faster than any other aircraft in his squadron owing to his crew chief's initiative in sanding, waxing and polishing it.'

Clearly, it is impossible to assess the reliabity of the cause and effect relationship set out in this statement. What is striking, however, is the statement that one aircraft was significantly faster than the others in the squadron. This is entirely consistent with the idea that there were considerable variations between the performances of aircraft of the same type.

Regards

Don W

[Kutscha]

A Ta152H certainly could outrun a P-51D at low level for Tank did. The drag on the Ta must be greater than on a 190.

[Graham Boak]

So is the power. The encounter supposedly took place at altitude, not as far as I know specified, where the different behaviour of the various superchargers could be very relevant.

However, few have argued that a Ta 152 was slower than Allied fighters.

[Crumpp]

You are most welcome Boomerang. I personally am most thankful to Col Feidler for joining us too.

Clearly, it is impossible to assess the reliabity of the cause and effect relationship set out in this statement. What is striking, however, is the statement that one aircraft was significantly faster than the others in the squadron. This is entirely consistent with the idea that there were considerable variations between the performances of aircraft of the same type.

Absolutely.

It's funny too the bond that forms between a pilot and his aircraft. Even my little GA family mover has an emotional attachment.

I mentioned to my wife last flight that I was thinking about getting a Mooney. It's faster and more economical than what we have now. The wife wouldn't have a thing to do with that idea. Completely out of character for her, she snapped at me to quit being disloyal to "Bravo Fox" as the plane had always carried us safely through every encounter. I though it was funny as she is not a pilot. Women huh? God bless em.



Of course, I will admit that the last thing I do before shutting out the lights in the hanger is get pat her on the cowl and thank her for being such a good airplane.

Oskar told me he was extremely upset when he lost one particular FW190 after being shot down. He was really upset when they hauled the plane off to the scrap yard an still remembers little details about that one aircraft. It was definitely his favorite.

You might also wish to consider his Fig 16, where the 1g and 4g flight envelopes for the F-5E can be seen to be very close together, at max speed at sea level. That's very little change for a 300% increase in weight. You can see why the change in level speed due to a 5% increase in weight is regarded as insignificant.

I think we are still just looking at maximum speed and nothing has changed in my opinion:

Crumpp says:

Now I understand you only wanted to make the point that "in regards to top level speed" in a very narrow definition, the affect of weight is insignificant.

I guess you could make that statement. I certainly would not make it. Once again it sounds to me like a Doctor claiming the small size of a cancer tumor means it is insignificant to the body.

From Perkins and Hage, "Airplane Performance Stability and Control"










Additionally it is very hard to compare aircraft like the F-16 to WWII designs. The entire design emphasis has evolved over time as to what is important in the fight due to the abundance of thrust available.

From Andrew M Skow paper "Agility as a Design contributor" AIAA library:




Mr Skow's paper is a worthwhile read and I meant to share it but unfortunately it exceeds the boards allotted attachment size for pdf files.


All the best,

Crumpp

[Nick Beale]

Obviously, I enjoy a bunch of equations as much as anybody but then I glanced up, saw the title of this thread and got distracted...

Something else I picked up from AIR40/152 was some numbers for the Fw 190 F-9. I've posted it as an attachment to preserve the layout, superscripted letters etc.

I get the words and the gist but if anyone can explain some of the other terms used, I'd be interested.