Fw-190 Dora-9 vs P-51D Mustang

[JonJGoldberg]

hey paul.kachurak,
Thanks, post it here or send it to JonJGoldberg@aol.com. I thank you for your offer to help, maybe I'm not seeing something as plain as the light of day but... being as I never went to 'school' for any of this, I graduated High School & went into the Air Force, became a sheet matal mechanic due to color blindness I didn't know I had; two years later trained for electronics, 'till medical records forced me out & back to tin knocking. From there I sold electronics then High End Stereo, now I sell, design, program, and manage lighting system automation for a large company. Being 'self learned' my approach to many thimgs goes across the grain of the educated norm. My CAD guys for example hate my drawings, as they do not follow some 'conventions' they feel I should. My contractors however love them, as for them the 'drawings' clearly represent the tasks at hand. They also have won an award from the manufacturer whoes product they show how to install, for being the best available of thier type; still the CAD guys gripe about 'CAPITAL LETTERS' that I don't use, and they have other valid points of form I'm learning to correct. But it was/is my 'non-standard' approach to the installation drawings and support materials that is being followed, within in which I'm now learning to conform to convention. I believe my approach to 'turn data / performance' is of the same mold, and we are experiencing a similar circumstance. However I'm defenitily willing to learn of, and accept any of my errors as errors.

Lastly, I believe that we must be very very close to one another in our personal 'overall' assessments of this issue, as we agree that the '51 & '190D9 are really too close to call; victory being matters of circuimstance, pilot skill & luck, much more than any imbalance in aircraft capabilities.

I've enjoyed this exchange paul, but feel it has run it's course on this thread. I welcome your data and would like to digress about this turn stuff further; please start a new thread & we will explore this together with the rest of the intrested members there.

[syscom3]

[quote].........'51 & '190D9 are really too close to call; victory being matters of circuimstance, pilot skill & luck, much more than any imbalance in aircraft capabilities. ....../quote]

I agree. The planes are so close in performance to each other that in the real world, slight differences are inconsequential.

[JonJGoldberg]

...Hey Flyboy, are you picking a fight with me? You are the man! I'm kidding, really, no offense taken or meant...

At your chosen speed & height as long as it is less than 225 knots, and below 20K Ft (choose any color you wish, as long as it is black). Oh and one other thing, the BATTLE does not start 'head to head' rather it will stat with the aircraft approaching the same point from the same altitude at a 90 degree off-set from one another. Fair? Thought not!

But what about the bank angle & loading numbers? How come I need no limits here? Is this where you are going? This proves your & paul's point about their relative unimportance. Smart guy (pilot), as I said you are the man, & I greatly respect your prowess in the art of one line comments, as I seem to need volumes of verbiage to properly express myself.

But please consider 'bank angle' & loading as it affects the following: AOA, Twist & Wash-Out. Another set of numbers I show was something I though others would pick up on, they are Tail Distance from CG, and area. After we finish rolling, and achieve a proper bank angle do we not apply 'Rudder & elevator to speed up or retard our turn, and roll rate, by effecting AOA, power delivery thrust lines, & torque balancing if needed. In certain 'maneuvers' I've learned to 'trick' my sims, as I see the g scale climb, and the screen darken, I know I'm going to loose it if this maintained any longer. As I can not change line, for if I do I die, or lose my opportunity, I've learned in my sim world to pull my nose up as much as possible, increasing my bank angle to above that at which there is 'equilibrium' forcing a climb during an inside loop turn, in effect slowing me down by increasing the distance traveled for each degree of the turn, storing my speed with altitude, and allowing me to lower the loading due to the aid of gravity, as I approach an inverted flying position, regardless of my climb.

Most planes of the time, WW2, are good for about 10 to 20 seconds of this, not due to airframe limits, but to engine limits, or human limits all of which I'm not sure are solved even today. Inverted, or near inverted flight played havoc on the engines ability to lubricate itself; as most every pilots manual warns. So where I go with this is that even though the optimal bank angle of all winged aircraft from a rock to an F-22 for turn of 2g is 60 degrees, the law effects the rock differently than the F-22, as 2g for each is achieved at different 'points' within each ones performance envelope.

Please see below the bank angles for the P-51 & P-38

[pbfoot]

Why are you using the standard rate turn as far as I know it is not a combat maneuver but an instrument procedure that you a measured rate of turn 180 degrees per minute or 3 degrees a second using 3 instruments needle/ball clock and altimeter it is very early instrument procedure but still very valid I can't see g forces being a part of this turn and if you used this turn in combat you would more then likely end up in a crater impaled on your engine if I'm misreading your post my apology

[JonJGoldberg]

pbfoot, thank you.

The illustrations are to show that although the math that proves 60 degrees is the proper bank angle for a 2g turn for every aircraft from a rock to an F-22, we implement turns not by loading but by rate of change; that a 'load factor 2' turn, or saying "I pulled a 2g turn", signifies a different rate of change in each aircraft, & a different turn performance: That bank angle is relevant to turn performance.

As shown in the pages from the manuals, this difference increases as speed increases, as each aircraft is at a different loading, therefore different bank angle, while flying at the same speed, and implementing the same rate of change turn.

[Lunatic]

Originally Posted by wmaxt

What it really did was by slowing the air before passing it through the radiators allowing it to absorbe a greater percentage of the heat from the radiator. The Only thrust generated, or can be generated, was by the heat expansion caused by the transfer of heat from the radiator. This helped reduce the drag of the cooling system but never came close to a positive thrust situation.

Heres a site that deals with both the "Merideth effect" (again a British therory) but the laminar flow and high speed tests of the P-51.
http://yarchive.net/mil/laminar_flow.html
This summs up what I've learned about the P-51s main atributes.

wmaxt

That is an interesting article. However I would point out that:

1) Argument 1 is falacious because the P-51 wing, inside the prop arc (at the crook for the P-51A/B/C/D) is conventional, not lamiar flow.

2) Argument 2 is invalid because on a twin engine aircraft the engines are mounted on the wings and transmit much more vibration to the wing than on a single engine plane. Also, the prop wash covers a larger proportion of the wing area.

3) Argument 3 is true, but only for an older P-51. For the first 50-100 hours of a P-51's life the wing was generally in good shape. Also, care was taken to keep the wings in good shape, and they were even often sanded to promote laminar flow. It is certainly true that no P-51's flying today (or even by Korea) had laminar flow performance, but in WWII the average combat life of a P-51 was about 50 hours, and most did have laminar flow.

4) Argument number 4 is picking nits. It is true the P-51 wing never exhibited "true laminar flow", but neither do modern wings. Even so, most jets today used laminar flow wing designs. The P-51's and modern jets utilize what's known as "near laminar flow", which is still superior to conventional flow.

5) Argument 5 ignores the facts. For the P-51 B, extensive in flight testing with aifoil measurement gear was conducted and the wing was re-designed to account for in-flight surface distortions.


LAL- 52638
"This P-51B was used at NACA Langley to conductin-flight
investigations of wing sections, including therevolutionary near
laminar-flow airfoil. The device located behind the white (test) section
of the wing is an air pressure rake which registered details of airflow
over the section." -- http://oea.larc.nasa.gov/PAIS/WWII.html

As for the cooling system generated thrust. First off, if you study the genisis of the P-51 it is pretty clear that Meredith's 1935 paper on the subject of cooling system based thrust had very little if anything to do with the system on the P-51. If you read the Meredith paper it is very short on details and does not discuss the significance of the pre-radiator expansion chamber nor the post-radiator compression chamber, nor the pressure controlled exit nozzle. In short, it is simply stating that if properly designed a small amount of thrust can be gained from a conventional radiator design.

The whole "Meredith" association was created by Lee Atwood, who, after Edgar Schmued's death (I believe in 1989?), started trying to claim a significant roll in the P-51's design and development. In fact, as pointed out very bluntly by Ed Horkey neither he nor Irv Ashkenas could recall Atwood's having had any part in the P-51's cooling system design (or anything else for that matter). Lee Atwood was in charge of the B-25, a plane that clearly lacks imagination or significant innovations. In studying the P-51 and NAA's history it becomes very very clear that Atwood was jelous of Schmued's accomplishments (the P-51 and F-86). It is sad that Atwood waited until after Schmued's death to try to steal credit for his work.

Generally speaking, the radiator thrust system negates between 90 and 100% of the P-51's cooling system drag at speeds above about 200 mph IAS. To give pespective to this number, at 85% of the P-51's mach rating (based upon 90% of cooling system drag being canceled by radiator thrust):

1) At 400 mph TAS @ 25,000 feet the P-51 was using only about 40 HP to overcome cooling system drag. The radiator thrust system was generating about 360 HP of engine equivalent thrust.

2) At 25,000 feet at 445 mph TAS, which is 85% of the P-51's mach speed limit, the radiator thrust generates approximately 530 HP of engine quivalent thrust.

3) At 15,000 feet at 454 mph TAS, again 85% of Mach limit, the P-51 generated about 630 HP of engine equivalent thrust.

This is one of the reasons why the P-51's dive acceleration and zoom climb were so good. The radiator thrust increases with the square of the speed, just like drag. So, as the speed increases the amount of thrust increases in proportion to the drag. Other planes must overcome this drag with engine power if they can, but even this is problematic because at such high speeds the prop begines to encounter its own mach effects and becomes somewhat useless as a source of additional thrust.

90% of cooling system thrust is not at all insignificant - the cooling system was responsible for well over half the drag on a slick WWII fighter.

=S=

Lunatic

[Lunatic]

Originally Posted by syscom3

I didnt think the gee suits available in the 40's were rated for those high G turns.

The Berger G-Suit was quite effective. In the years following WWII only slight improvments have been made in the design, and most of these have to do with pilot comfort (they ramp up more smoothly) not suit effectiveness.

Today, there are a new class of hydrolic G-suits under development which may provide much superior performance, but until they are developed, the pneumatic Berger type G-suit is still the standard type and it has changed very little since WW2.

[FLYBOYJ]

Originally Posted by pbfoot

Why are you using the standard rate turn as far as I know it is not a combat maneuver but an instrument procedure that you a measured rate of turn 180 degrees per minute or 3 degrees a second using 3 instruments needle/ball clock and altimeter it is very early instrument procedure but still very valid I can't see g forces being a part of this turn and if you used this turn in combat you would more then likely end up in a crater impaled on your engine if I'm misreading your post my apology

Very true, those charts are showing turns related to instrument procedures, but it clearly shows the more speed, the higher the bank angle, then refer back to the original chart that shows how G loading increases with bank angle...

[wmaxt]

Lunatic,

The site I referenced is what I belive after seeing a large number of descriptions of both systems including post war AAF and NAA descriptions which stated, True laminar flow was not achievable due to manufacturing tolerances available at that time. To keep the surface smooth on a B-47 required slippers, How many times have I seen people riding the wing or walking in boots on a P-51 wing? I viewed these several years ago but will try to find them again.

How much speed added, are we talking here
P-51D 9,000lbs/1650hp = 5.4 lbs/hp and 437
P-47N 16,000lbs/2800hp = 5.7lbs/hp and 460mph
F4U-4 12,000lbs/2200hp = 5.3lbs/hp and 446mph
P-38L 18,000lbs/2850hp = 6.3lbs/hp and 414mph
Bf-109K 7348lbs/2,000hp = 3.7lbs/hp

The P-51 doesn't show anything special here, infact the F4U-4 is doing as good with higher drag cloth wings and a radial engine. The P-38 is giving up a full pound per hp for 23mph. AND the N is not only 23mph faster but is carrying more weight for each horse and that terrible radial engine.

I'm not sure where your numbers come from but that level of extra thrust isn't showing up in the performance of the P-51. The Placement of the cooling scoop/plenum in a high drag area and the resultant smoothing of the airflow provides most of the effect your seeing.

The Merideth Effect is a minor jet engine just without the open flame, the same rules of thermodynamics apply. The only thrust is that provided by the expansion of the air caused by the radiator heat. If that wasn't true every aircraft we fly today would have a big scoop under the wing to get free horse power. The P-51s system slowed the air more than any other giving a. better cooling system performance and b. a little thrust many of the estimates I've seen were from 50lbs to 150lbs

I have also seen the speed of the P-51 creditted to either the laminar flow or to the cooling system without mention of the other, which is it?. The P-51 was a very good aircraft but it wasn't perfect nor was it as good as its press.

wmaxt

[lesofprimus]

The P-51 was a very good aircraft but it wasn't perfect nor was it as good as its press.

I think thats true of every aircraft thats ever flown... I dont think there was ever a perfect aircraft.... Hmmmm....

[wmaxt]

Originally Posted by lesofprimus

[
I think thats true of every aircraft thats ever flown... I dont think there was ever a perfect aircraft.... Hmmmm....

I agree 100%.

wmaxt

[syscom3]

The P38 also had some thrust from its exhaust.

Im also curious, are these figures with a painted surface? Ive read somewhere that by skipping the paint on your aircraft, you can gain a few mph.

[pbfoot]

the paints weight alone will cause lost of speed airliners that are painted usually have less useful cargo capacity I once heard that a 747 has over a ton of paint on it these numbers of top speeds are always in a/c that are highly waxed (xtra duty from personal experience) and access panels would probably be sealed and streamlined after all the numbers have alot to due whether the manufacturer gets a contract

[wmaxt]

Originally Posted by syscom3

The P38 also had some thrust from its exhaust.

Im also curious, are these figures with a painted surface? Ive read somewhere that by skipping the paint on your aircraft, you can gain a few mph.

Thats true at least to the extent of weight and paint finish. I read recently that it was estimated that the paint on a C-18 (twin Beech?) added up to about 91 horsepower penalty.

The numbers for the P-51, P-38, P-47 can be assumed to be without paint as they hit the lines in mid 44 or later. The F4U-4 and 109 had painted surfaces.

wmaxt

[Soren]

Well said Les.

Originally Posted by Lunatic

It is true the P-51 wing never exhibited "true laminar flow", but neither do modern wings. Even so, most jets today used laminar flow wing designs. The P-51's and modern jets utilize what's known as "near laminar flow", which is still superior to conventional flow.

Lunatic the reason modern fighters use a laminar flow airfoil design is purely because it allows them to go faster, thats it. If modern jet fighters were using conventional airfoils their speed would be decreased considerably, and going supersonic would be more difficult. However low speed maneuverability would be alot better with the conventional airfoil.

One thing that is worth knowing about laminar flow wings is that they stall earlier and more violently in turns than conventional type wings. This is why modern day fighters use automatic slats and flaps, to prevent these early stalls in banking maneuvers. And this is also why laminar flow wings weren't particularly efficient on WWII fighters, because of the low speeds the a/c were flying at, speeds where a conventional type wing will provide much better maneuverability.

However there are two good points about the Laminar flow wing which WW2 fighters could benefit from, and that was an increased speed when flying straight and a better acceleration in dives. Both things which are good to have if your only going to rely on B&Z tactics.