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freakvollder
08-23-2009, 10:35 AM
http://i7.photobucket.com/albums/y274/gt_diesel/P-51D_Mustang.jpg
What makes the P51 Mustang ore Hawker Tempest so energy efficient? Is the Bf-109-wing-profile and airframe aerodynamic so much different? Are the Fw190s equal in this regard. Why are early war planes so different from late war planes?

Who has good information about this?

~S~

freakvollder
08-23-2009, 10:35 AM
http://i7.photobucket.com/albums/y274/gt_diesel/P-51D_Mustang.jpg
What makes the P51 Mustang ore Hawker Tempest so energy efficient? Is the Bf-109-wing-profile and airframe aerodynamic so much different? Are the Fw190s equal in this regard. Why are early war planes so different from late war planes?

Who has good information about this?

~S~

BillSwagger
08-23-2009, 11:28 AM
I'm no expert but i notice that many early war planes tend to have a steeper dihedral. This would allow for more stability in turns, but would also eat energy in other maneuvers.
So possibly having a flatter wing was more efficient for maintaining high speeds.
http://en.wikipedia.org/wiki/D..._and_Dihedral_Effect (http://en.wikipedia.org/wiki/Dihedral_%28aircraft%29#Dihedral_Angle_and_Dihedra l_Effect)

Waldo.Pepper
08-23-2009, 11:41 AM
Google "laminar flow wing" and read up on it for part of the answer.

Also may want to look up "Meredith effect" (Ignore all returns speaking about Burges Meredith though.)

freakvollder
08-23-2009, 11:48 AM
oh thank you! very good tips!

R_Target
08-23-2009, 01:27 PM
In the case of the P-51, it's a pretty slippery plane for it's time.

VW-IceFire
08-23-2009, 01:36 PM
Another "slippery" plane is the P-39. It has a very low drag coefficient...I forget the number but its up there with the Mustang. It just doesn't have the power to make full use of it...

Kettenhunde
08-23-2009, 07:17 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> many early war planes tend to have a steeper dihedral. </div></BLOCKQUOTE>

Designers attempt to achieve neutral lateral stability. The amount of dihedral required to achieve that varies based on the aircraft's design particulars. The result is the same however, neutral stability in the lateral axis.

This thread goes down the same road as "energy retention" in aircraft.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> What makes the P51 Mustang ore Hawker Tempest so energy efficient? </div></BLOCKQUOTE>

What is energy efficient? Your question does not make much sense. We are talking about airplanes not household appliances.

If your goal is to control your speed and be able to land in the shortest distance possible, which is more energy efficient in your opinion?

A Zenith CH-701 or an F-22 Raptor……

See the point, if you ask more specific questions it would be easier to provide specific answers that make sense to you.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Is the Bf-109-wing-profile and airframe aerodynamic so much different? </div></BLOCKQUOTE>

It is a different airplane. The designer chose the airfoil, wing design, and airframe design to accomplish his design goals of producing an air superiority fighter.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Are the Fw190s equal in this regard. </div></BLOCKQUOTE>

In regard to what? All of these aircraft maximize the appropriate amount of energy input into the design in accordance with their design performance parameters.

They all have sustained and instantaneous performance design goals set by the designer which the aircraft meet.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Why are early war planes so different from late war planes?
</div></BLOCKQUOTE>

Technology tends to advance faster in times of conflict. Enclosed cockpits, airframe construction, monoplane design, retractable landing gear, materials technology, engine technology, avionics, and weapons all progressed or came into fashion as a result of the war.

The war moved theory into the realm of practical experience.

All the best,

Crumpp

Lt_Letum
08-23-2009, 11:19 PM
Control authority can have a big effect on how draggy a plane feels (not how draggy it actually is).

If it is easy to make energy inefficient maneuvers then most pilots will make more of them and find their energy gone much sooner than they would in a plane that can't easily make energy inefficient maneuvers (i.e. highspeed turns/vertical maneuvers).

JtD
08-24-2009, 12:18 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by VW-IceFire:
Another "slippery" plane is the P-39. It has a very low drag coefficient...I forget the number but its up there with the Mustang. It just doesn't have the power to make full use of it... </div></BLOCKQUOTE>

Then why does the heavier and larger P-51 go faster with the same power installed?

Waldo.Pepper
08-24-2009, 12:40 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
Then why does the heavier and larger P-51 go faster with the same power installed? </div></BLOCKQUOTE>



Consider the following from - WW2 Fighter Conflict by Alfred Price page 43. (I bolded the relevant text)

"One important airframe change which was not incorporated in the Spitfire during the Second World War was the so-called 'laminar flow' wing. This was a wing with an exceptionally fine finish: the surface roughness had to be less than .0005 of an inch and the maximum wave allowance was .0001 of an inch in any two inches of surface. This fineness of finish was combined with a high speed aerofoil section, with its thickest point about half way back from the leading edge (rather than a third of the way back, in a conventional aerofoil).

The first aircraft operational with the laminar flow wing was the North American P-51 Mustang, which entered service in the RAF in the summer of 1942. Later, re-engined with a Rolls-Royce Merlin with a two-stage supercharger, the Mustang became one of the outstanding fighters of the war.

The effect of the laminar flow wing can be seen if the performance of the P-51B Mustang is compared with that of the Spitfire IX; the comparison is valid, because the two aircraft were powered by almost exactly the same type of Merlin. In terms of wing span and area the Mustang's wing was closely comparable with that of the Spitfire; the latter's wing was 2 inches longer and about 4 per cent greater in area. Yet in spite of the similarity in wing dimensions and engine power, and the considerably greater weight of the Mustang (about a quarter greater), the latter was approximately 20 mph faster than the Spitfire IX for any given cruising power setting of the engine , and about 30 mph faster at maximum speed. The main factors responsible for this were the laminar flow wing and the high speed aerofoil."

deepo_HP
08-24-2009, 01:51 AM
i would like to know, how much the laminar flow over the laminar-airfoil depends on the finish.
i think, laminar-profiles are commonly used with sail-planes nowadays, fe. which indeed alays look quite proper and clean.

for a combat plane i can't help thinking of a pilot of less than 8 stones, who needs to enter the cockpit with silk-stockings in order not to scratch the finish. what about mosquitos, splashing on the wing and leaving crusty blood and chitin?

i would guess, the profile would be the factor of laminar flow rather than the finish - even if it surely makes sense to have it smooth, those .0005 inches are just too hypothetical for my taste to be mentioned.

perhaps anyone has information, how the finish contributes in real use and how it was taken care of?

R_Target
08-24-2009, 05:49 AM
Wind-tunnel type airflow was rarely realized on service examples. It's kind of a moot point though, as the P-51 was fast nevertheless.

stalkervision
08-24-2009, 06:07 AM
http://upload.wikimedia.org/wikipedia/commons/0/0d/Blohm%26Voss_BV_40_am_Boden_wiki.jpeg

The Blohm & Voss BV 40 was a German glider fighter designed to attack Allied bomber formations. By eliminating the engine and positioning the pilot in a prone position (i.e., lying on the front), the cross-sectional area of the aircraft was much reduced, making the aircraft much harder for bomber gunners to hit.

Its key features were a very narrow and fairly heavily-armored cockpit, and two 30 mm (1.18 in) MK 108 cannons in the wing roots with very limited ammunition. The fuselage was constructed almost entirely of wood, a non-strategic material. During its short attack time, the glider would fire its weapons, then glide back to earth, although for a time, the idea of carrying a bomb on a cable behind the glider was entertained.

The first flight was in the May of 1944. Several prototypes were completed, but the project was stopped later in the year as the end of the war drew near.


I win! http://forums.ubi.com/groupee_common/emoticons/icon_razz.gif

stalkervision
08-24-2009, 06:16 AM
If we are talking about powered fighters then the Japanese aircraft like the zero and oscar beat the american's heavyweights hands down. This is because of their light weight and low horsepower needed for the speeds they archived. Just look at their combat radius also.

Bremspropeller
08-24-2009, 08:14 AM
Anyone can achieve great ranges by building a toaster in a tinfoil-airplane.

The P-51 was one of the first aircraft that achieved great ranges and high speeds out of a medicore-powered engine.
The key to this is a reasonably efficient airframe and a high fuel-fraction compared to other fighters.

The drawbacks of any laminar-flow wing are it's lower lift-coefficients accross the board, it's sh1ttier stall characteristics and it's vulnerability to dents, scratches, finish-tolerances and contaminations of the airfoil - something, that most commonly happens in operational service.

Xiolablu3
08-24-2009, 08:25 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:


The P-51 was one of the first aircraft that achieved great ranges and high speeds out of a medicore-powered engine.
</div></BLOCKQUOTE>


http://forums.ubi.com/images/smilies/88.gif

AndyJWest
08-24-2009, 08:29 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Xiolablu3:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:


The P-51 was one of the first aircraft that achieved great ranges and high speeds out of a medicore-powered engine.
</div></BLOCKQUOTE>


http://forums.ubi.com/images/smilies/88.gif </div></BLOCKQUOTE>

+1 http://forums.ubi.com/images/smilies/88.gif

JtD
08-24-2009, 09:25 AM
Waldo, I know about the laminar flow design of the P-51s wings. Like others have stated by now, I doubt that much of a laminar flow did actually develop under wartime conditions. The P-51 still achieved outstanding speeds.

Also, my question was rather why the P-39 would be nearly as good as the P-51 if the latter managed be heavier, larger and yet to go faster for the same power. As opposed to IceFires statement, this indicates the P-51 was a lot better aerodynamically.

AndyJWest
08-24-2009, 10:42 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
...my question was rather why the P-39 would be nearly as good as the P-51 if the latter managed be heavier, larger and yet to go faster for the same power. As opposed to IceFires statement, this indicates the P-51 was a lot better aerodynamically.
</div></BLOCKQUOTE>

P-39s wre all powered by Allison engines (1,200 hp in a P-39Q)
P-51s from the B model onwards had Packard Merlins (1,490 hp in a P-51D)

The P-51 was probably a lot more refined aerodynamically, and the extra weight of the long shaft to drive the prop, as well as the weight of the nosewheel, can't have helped the P-39 either. Very different aircraft though.

Freiwillige
08-24-2009, 10:42 AM
I have read post war reports that claim that Laminar flow was not actually achieved in the P-51. The key to its speed was an overall clean design and the low drag radiator which produced very little drag and at speed it produced thrust!

The P-39 did not have a laminar flow wing installed but the P-63 did.

Lt_Letum
08-24-2009, 10:49 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freiwillige:
I have read post war reports that claim that Laminar flow was not actually achieved in the P-51. </div></BLOCKQUOTE>

That may be so, but a thinner wing would help without L.Flow anyway.

JtD
08-24-2009, 10:54 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AndyJWest:


P-39s wre all powered by Allison engines (1,200 hp in a P-39Q)
P-51s from the B model onwards had Packard Merlins (1,490 hp in a P-51D) </div></BLOCKQUOTE>

The P-51A was driven by the same Allison as the P-39D and was quite a bit (roughly 10%) faster.

JtD
08-24-2009, 10:55 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freiwillige:
The key to its speed was an overall clean design and the low drag radiator which produced very little drag and at speed it produced thrust!
</div></BLOCKQUOTE>

The drag created by the radiator was always larger than the thrust created by it. Also at high speeds.

freakvollder
08-24-2009, 11:48 AM
First thank you for ALL your posts! I am sorry but my English is not so very good because I am from Germany. That why I have tried to make my questions simple. http://forums.ubi.com/images/smilies/11.gif



<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Lt_Letum:
Control authority can have a big effect on how draggy a plane feels (not how draggy it actually is).

If it is easy to make energy inefficient maneuvers then most pilots will make more of them and find their energy gone much sooner than they would in a plane that can't easily make energy inefficient manoeuvres (i.e. high-speed turns/vertical manoeuvres). </div></BLOCKQUOTE>

you are sure with vertical manoeuvres? Vertical manoeuvring should be energy efficient...?



<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stalkervision:
http://upload.wikimedia.org/wikipedia/commons/0/0d/Blohm%26Voss_BV_40_am_Boden_wiki.jpeg

The Blohm & Voss BV 40 was a German glider fighter designed to attack Allied bomber formations. By eliminating the engine and positioning the pilot in a prone position (i.e., lying on the front), the cross-sectional area of the aircraft was much reduced, making the aircraft much harder for bomber gunners to hit.

Its key features were a very narrow and fairly heavily-armored cockpit, and two 30 mm (1.18 in) MK 108 cannons in the wing roots with very limited ammunition. The fuselage was constructed almost entirely of wood, a non-strategic material. During its short attack time, the glider would fire its weapons, then glide back to earth, although for a time, the idea of carrying a bomb on a cable behind the glider was entertained.

The first flight was in the May of 1944. Several prototypes were completed, but the project was stopped later in the year as the end of the war drew near.


I win! http://forums.ubi.com/groupee_common/emoticons/icon_razz.gif </div></BLOCKQUOTE>

a very nice plane? Cool http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Bremspropeller
08-24-2009, 11:58 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Xiolablu3:
http://forums.ubi.com/images/smilies/88.gif </div></BLOCKQUOTE>

You think that ~1,300hp is lotsa power, huh? http://forums.ubi.com/images/smilies/34.gif

AndyJWest
08-24-2009, 12:10 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Xiolablu3:
http://forums.ubi.com/images/smilies/88.gif </div></BLOCKQUOTE>

You think that ~1,300hp is lotsa power, huh? http://forums.ubi.com/images/smilies/34.gif </div></BLOCKQUOTE>

Can you be a bit more specific about which P-51 model you are talking about. Then we can sensibly discuss power-to-weight ratios, performance, and exactly what you meant by "great ranges and high speeds".

stalkervision
08-24-2009, 01:55 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freiwillige:
I have read post war reports that claim that Laminar flow was not actually achieved in the P-51. The key to its speed was an overall clean design and the low drag radiator which produced very little drag and at speed it produced thrust!

The P-39 did not have a laminar flow wing installed but the P-63 did. </div></BLOCKQUOTE>

I read this to F/W out of a Smithsonian air and space magazine about the p-51. The author makes some very convincing points.

Xiolablu3
08-24-2009, 02:27 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stalkervision:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freiwillige:
I have read post war reports that claim that Laminar flow was not actually achieved in the P-51. The key to its speed was an overall clean design and the low drag radiator which produced very little drag and at speed it produced thrust!

The P-39 did not have a laminar flow wing installed but the P-63 did. </div></BLOCKQUOTE>

I read this to F/W out of a Smithsonian air and space magazine about the p-51. The author makes some very convincing points. </div></BLOCKQUOTE>

Yeah, apparantly it cleverly uses exhaust and radiator thrust which also adds to the clean design.

Bremspropeller
08-24-2009, 02:35 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Can you be a bit more specific about which P-51 model you are talking about. Then we can sensibly discuss power-to-weight ratios, performance, and exactly what you meant by "great ranges and high speeds". </div></BLOCKQUOTE>

Doesn't actually matter.

With contemporary fighters such as the Corsair, F6F, P-47, Temspest/ Typhoon, even the Mustang doesn't look all that powerful.

BTW: "power to weight" is completely useless.
What counts is "thrust to weight" http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Xiolablu3
08-24-2009, 02:49 PM
You dont often hear the Merlin engine called 'mediocre' http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

I guess when comparing it to the Griffon?

Bremspropeller
08-24-2009, 02:51 PM
Well, in terms of power-output it wasn't top-of-the-line anymore by 1940; let alone 1943 http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

AndyJWest
08-24-2009, 02:53 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Can you be a bit more specific about which P-51 model you are talking about. Then we can sensibly discuss power-to-weight ratios, performance, and exactly what you meant by "great ranges and high speeds". </div></BLOCKQUOTE>

Doesn't actually matter.

With contemporary fighters such as the Corsair, F6F, P-47, Temspest/ Typhoon, even the Mustang doesn't look all that powerful.

BTW: "power to weight" is completely useless.
What counts is "thrust to weight" http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

'... doesn't look all that powerful' is different from 'mediocre' (I assume that is what you meant).

If you pick the contemporary aircraft with the biggest engines, then yes, a Merlin has less power.

If 'power to weight' is useless, why comment on a 'mediocre' engine, rather than mediocre thrust? The engine produces the power, the propeller produces the thrust, as far as I know....

AndyJWest
08-24-2009, 02:57 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Well, in terms of power-output it wasn't top-of-the-line anymore by 1940; let alone 1943 http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

I'm sure the engine on a cross-channel ferry will produce more power than a Merlin too. Would that make a P-51 faster? Or does the power-to-weight ratio matter after all. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

Bremspropeller
08-24-2009, 03:09 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">'... doesn't look all that powerful' is different from 'mediocre' (I assume that is what you meant). </div></BLOCKQUOTE>

"Medicore" is in-between "weak" and "powerful".
What's your point?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">If 'power to weight' is useless, why comment on a 'mediocre' engine, rather than mediocre thrust? The engine produces the power, the propeller produces the thrust, as far as I know.... </div></BLOCKQUOTE>

http://forums.ubi.com/groupee_common/emoticons/icon_rolleyes.gif
Because the engine's power-output WAS medicore by the time?

I never made any comment about the prop's thrust.
Maybe you should read my post again - with your eyes opened this time, though.

Xiolablu3
08-24-2009, 03:12 PM
Hes got you hooked well and proper Andy http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

na85
08-24-2009, 03:19 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Xiolablu3:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stalkervision:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freiwillige:
I have read post war reports that claim that Laminar flow was not actually achieved in the P-51. The key to its speed was an overall clean design and the low drag radiator which produced very little drag and at speed it produced thrust!

The P-39 did not have a laminar flow wing installed but the P-63 did. </div></BLOCKQUOTE>

I read this to F/W out of a Smithsonian air and space magazine about the p-51. The author makes some very convincing points. </div></BLOCKQUOTE>

Yeah, apparantly it cleverly uses exhaust and radiator thrust which also adds to the clean design. </div></BLOCKQUOTE>

Pretty sure that's been debunked numerous times on this forum, hasn't it? IIRC the thrust produced by the radiator/exhaust was shown to be negligibly small.

stalkervision
08-24-2009, 03:34 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by na85:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Xiolablu3:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by stalkervision:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Freiwillige:
I have read post war reports that claim that Laminar flow was not actually achieved in the P-51. The key to its speed was an overall clean design and the low drag radiator which produced very little drag and at speed it produced thrust!

The P-39 did not have a laminar flow wing installed but the P-63 did. </div></BLOCKQUOTE>

I read this to F/W out of a Smithsonian air and space magazine about the p-51. The author makes some very convincing points. </div></BLOCKQUOTE>

Yeah, apparantly it cleverly uses exhaust and radiator thrust which also adds to the clean design. </div></BLOCKQUOTE>

Pretty sure that's been debunked numerous times on this forum, hasn't it? IIRC the thrust produced by the radiator/exhaust was shown to be negligibly small. </div></BLOCKQUOTE>

I saw some graphs and proofs in the Smithsonian magazine that say otherwise. What has been debunked is the Mustang's laminar flow wing as being the reason for the low drag. A true laminar flow wing except on a research aircraft is mighty hard to come by.

Lt_Letum
08-24-2009, 03:36 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Lt_Letum:
Control authority can have a big effect on how draggy a plane feels (not how draggy it actually is).

If it is easy to make energy inefficient maneuvers then most pilots will make more of them and find their energy gone much sooner than they would in a plane that can't easily make energy inefficient manoeuvres (i.e. high-speed turns/vertical manoeuvres). </div></BLOCKQUOTE>

you are sure with vertical manoeuvres? Vertical manoeuvring should be energy efficient...? </div></BLOCKQUOTE>


Nosing-down and pulling-up both cause an energy
drop. The harder you do it, the more energy you
lose.

If you are in a plane that can nose-down/pull-up
very violently then you may be prone to losing
more energy than you would in a plane that will
only nose-down/pull-up gently.

Of course, a good pilot will compensate by being
especially careful not to be to forceful in the
more maneuverable planes if e-retention is
very important at that point.

na85
08-24-2009, 03:39 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Lt_Letum:

Nosing-down and pulling-up both cause an energy
drop. The harder you do it, the more energy you
lose. </div></BLOCKQUOTE>

Any maneuver in an aircraft causes an energy drop.

AndyJWest
08-24-2009, 03:45 PM
Bremspropeller:

The only definition of 'medicore' I can find, from http://www.urbandictionary.com...ne.php?term=medicore (http://www.urbandictionary.com/define.php?term=medicore)
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
medicore:
less than excellent; mediocre. An all-too-common Internet typo of 'mediocre'.
</div></BLOCKQUOTE>

A definition of 'mediocre', from here http://www.merriam-webster.com/dictionary/mediocre
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
mediocre:
of moderate or low quality, value, ability, or performance
</div></BLOCKQUOTE>

If you think that puts "Medicore" between "weak" and "powerful", well thats your interpretation, but why not be clearer in the first place?

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
I never made any comment about the prop's thrust.
Maybe you should read my post again - with your eyes opened this time, though.
</div></BLOCKQUOTE>

But from your post of 21:35:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
BTW: "power to weight" is completely useless.
What counts is "thrust to weight"
</div></BLOCKQUOTE>

Bremspropeller
08-24-2009, 03:52 PM
Sorry, but my dictionary puts it right where I put it - pity your's doesn't.

In order to keep it simple:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The P-51 was one of the first aircraft that achieved great ranges and high speeds out of a medicore-powered engine.
The key to this is a reasonably efficient airframe and a high fuel-fraction compared to other fighters. </div></BLOCKQUOTE>

=&gt; "efficient airframe"
=&gt; "low drag"
=&gt; "less thrust required"

Anything left to be explained? http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

stalkervision
08-24-2009, 04:00 PM
you left out " less weight" http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

and maybe a high lift airfoil?

AndyJWest
08-24-2009, 04:03 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
Sorry, but my dictionary puts it right where I put it - pity your's doesn't.

In order to keep it simple:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The P-51 was one of the first aircraft that achieved great ranges and high speeds out of a medicore-powered engine.
The key to this is a reasonably efficient airframe and a high fuel-fraction compared to other fighters. </div></BLOCKQUOTE>

=&gt; "efficient airframe"
=&gt; "low drag"
=&gt; "less thrust required"

Anything left to be explained? http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif </div></BLOCKQUOTE>

Yes, two things:
(a) why use 'medicore' rather than a word we can at least look up in a proper dictionary?

(b) How you can talk about 'a medicore-powered engine', and later state that 'BTW: "power to weight" is completely useless.'?

If you can't write clearly and consistently, perhaps it might be better not to criticise others for allegedly not reading your posts with their eyes open.

Bremspropeller
08-24-2009, 04:25 PM
a) I used "mediocre", because it struck my mind right at that moment.
I haven't taken literature-classes, so excuse me if I can't describe the facts more poetically.
I'll draw a picture next time, I promise http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

b) Comparing both, P-51 and Corsair, I get a ~3.077% thrust/ weight-advantage of the Corsair over the P-51 at both's MTOW.

I got there the following way:
Taking both, max. power-figures and and MTOW for both fighters.
As we assume the same efficiency for both airscrews and a linear thurst-output (thrust per engine-power), we can actually compare power/ weight for the sake of easiness:
I took 1600HP and 5200kg for the P-51 and 2000HP and 6300kg for the Corsair.

(1600/5200) / (2000/6300) = 0.9692

Those figures are an approximation and gross simplification, yet they give you an idea.
Especially, when you think of the issue that a Corsair a MTOW is hauling a whole lot of iron.

AndyJWest
08-24-2009, 04:39 PM
I'm not sure that a 3% higher power-to-weight ratio for the Corsair is enough to bring out the bunting and declare a national holiday, is it. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif


Given that even the best radial engine installation is likely to produce more drag than a properly-designed in-line engine & radiator setup, you could easily lose this 3% advantage anyway...

ImpStarDuece
08-24-2009, 05:04 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
a) I used "mediocre", because it struck my mind right at that moment.
I haven't taken literature-classes, so excuse me if I can't describe the facts more poetically.
I'll draw a picture next time, I promise http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

b) Comparing both, P-51 and Corsair, I get a ~3.077% thrust/ weight-advantage of the Corsair over the P-51 at both's MTOW.

I got there the following way:
Taking both, max. power-figures and and MTOW for both fighters.
As we assume the same efficiency for both airscrews and a linear thurst-output (thrust per engine-power), we can actually compare power/ weight for the sake of easiness:
I took 1600HP and 5200kg for the P-51 and 2000HP and 6300kg for the Corsair.

(1600/5200) / (2000/6300) = 0.9692

Those figures are an approximation and gross simplification, yet they give you an idea.
Especially, when you think of the issue that a Corsair a MTOW is hauling a whole lot of iron. </div></BLOCKQUOTE>

Which Packard Merlin are you using, and at what altitudes are you measuring the power output?

V-1650-3 on the P-51 B/C was rated at 1,530-1,540 hp at 61" and 1,690-1,700 hp at 67";
V-1650-7 on the P-51D was rated at 1,580 hp at 61" and at 1,700 hp at 67".

Power-to-weight is not a static number, particularly not with a two stage, two speed engine like the later Merlins. It changes significantly with altitude.

PanzerAce
08-24-2009, 05:09 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
Waldo, I know about the laminar flow design of the P-51s wings. Like others have stated by now, I doubt that much of a laminar flow did actually develop under wartime conditions. The P-51 still achieved outstanding speeds.

Also, my question was rather why the P-39 would be nearly as good as the P-51 if the latter managed be heavier, larger and yet to go faster for the same power. As opposed to IceFires statement, this indicates the P-51 was a lot better aerodynamically. </div></BLOCKQUOTE>

On the deck they were probably quite evenly matched, but the advantage of the Merlin is that it allows similar performance no matter what the altitude, which the Allisons couldn't equal.

PanzerAce
08-24-2009, 05:13 PM
And why are some of you guys (like stalker) so hung up on weight? Since we aren't discussing ACMs or climb rates, weight as little to do with the speed of an aircraft. CoD, cross-sectional area, and engine power curves have far more impact on the speed and efficiency of an airplane.

Bremspropeller
08-24-2009, 05:25 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Given that even the best radial engine installation is likely to produce more drag than a properly-designed in-line engine & radiator setup, you could easily lose this 3% advantage anyway... </div></BLOCKQUOTE>

Thatswhy I said "more efficient airframe" in the first place. http://forums.ubi.com/images/smilies/10.gif

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I'm not sure that a 3% higher power-to-weight ratio for the Corsair is enough to bring out the bunting and declare a national holiday, is it. </div></BLOCKQUOTE>

Well, considering the Corsair would be over a ton heavier, it quite is.
And that is with extarnal ordnance http://forums.ubi.com/images/smilies/10.gif

Taking 1700hp for the Mustang and 2250hp for the Corsair to get both max ratings, the difference opens up to 8.5%

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Which Packard Merlin are you using, and at what altitudes are you measuring the power output?

V-1650-3 on the P-51 B/C was rated at 1,530-1,540 hp at 61" and 1,690-1,700 hp at 67";
V-1650-7 on the P-51D was rated at 1,580 hp at 61" and at 1,700 hp at 67".

Power-to-weight is not a static number, particularly not with a two stage, two speed engine like the later Merlins. It changes significantly with altitude.
</div></BLOCKQUOTE>

None, I took one in-between - see above.

I know that those ratios are dependant on a couple of factors, such as supercharger alts, temperature, humidity and the state of the engine itself.

But you have to make tradeoffs for the sake of comparison.

stalkervision
08-24-2009, 05:33 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PanzerAce:
And why are some of you guys (like stalker) so hung up on weight? Since we aren't discussing ACMs or climb rates, weight as little to do with the speed of an aircraft. CoD, cross-sectional area, and engine power curves have far more impact on the speed and efficiency of an airplane. </div></BLOCKQUOTE>

weight was always a important consideration in ww 2 fighters. Even now it is still important though a lot less so with the very powerful jet engines available to us now.

take a p-51 and pull some weight out and you now have a aircraft with a much lower wing loading. Do you realize what this means?

also a higher thrust to weight ratio. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

Bremspropeller
08-24-2009, 05:39 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">And why are some of you guys (like stalker) so hung up on weight? Since we aren't discussing ACMs or climb rates, weight as little to do with the speed of an aircraft. CoD, cross-sectional area, and engine power curves have far more impact on the speed and efficiency of an airplane. </div></BLOCKQUOTE>

Don't blame me - I was just stating the 51 had an efficient airframe with a mediocre-powered engine http://forums.ubi.com/images/smilies/59.gif

I'm also finding it hard to get the challange behind understanding the "efficient =&gt; low drag =&gt; less thrust req'd =&gt; less power req'd"-chain http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

stalkervision
08-24-2009, 05:42 PM
Brems your the il-2 scapegoat for everything don't you know? http://forums.ubi.com/images/smilies/winky.gif


"....ah brems. He did it once again. http://forums.ubi.com/images/smilies/51.gif" http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif

Bremspropeller
08-24-2009, 05:49 PM
I'm so glad nobody brought up wing-loading so far http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif http://forums.ubi.com/images/smilies/shady.gif

Wanna know why?

Because the P-51 had a MEDIOCRE (my new favourite word http://forums.ubi.com/images/smilies/59.gif ) wing-loading and laminar-wings with crappy CL/ Alpha-behaviour http://forums.ubi.com/images/smilies/winky.gif

AndyJWest
08-24-2009, 05:50 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">...the 51 had an efficient airframe with a mediocre-powered engine </div></BLOCKQUOTE>
... and then they fitted a Merlin. http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

What Brems fails to grasp is that to us Brits, insulting the Merlin is grounds for divorce - worse than accusing us of cheating in a game of golf, or mistaking us for Americans. http://forums.ubi.com/images/smilies/16x16_smiley-wink.gif

The_Stealth_Owl
08-24-2009, 05:52 PM
I'm an American!

http://i605.photobucket.com/albums/tt138/SILVERFISH1992/Owldontmess.jpg

stalkervision
08-24-2009, 05:58 PM
New thread.."The merlin engine. Not really so great after all"

http://forums.ubi.com/images/smilies/winky.gif

Bremspropeller
08-24-2009, 06:04 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">What Brems fails to grasp is that to us Brits, insulting the Merlin is grounds for divorce - worse than accusing us of cheating in a game of golf, or mistaking us for Americans. </div></BLOCKQUOTE>

http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif http://forums.ubi.com/images/smilies/25.gif

R_Target
08-24-2009, 07:06 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
I'm also finding it hard to get the challange behind understanding the "efficient =&gt; low drag =&gt; less thrust req'd =&gt; less power req'd"-chain http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif </div></BLOCKQUOTE>

I think they understand that, but you insulted the Merlin, and they will never forgive you.

Flight_boy1990
08-24-2009, 07:31 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by The_Stealth_Owl:
http://i605.photobucket.com/albums/tt138/SILVERFISH1992/Owldontmess.jpg </div></BLOCKQUOTE>
http://i293.photobucket.com/albums/mm63/GringoBG/4444.jpg

http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

<STRIKE>Just kidding.</STRIKE>

jarink
08-24-2009, 07:37 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by R_Target:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:
I'm also finding it hard to get the challange behind understanding the "efficient =&gt; low drag =&gt; less thrust req'd =&gt; less power req'd"-chain http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif </div></BLOCKQUOTE>

I think they understand that, but you insulted the Merlin, and they will never forgive you. </div></BLOCKQUOTE>

You could get really mean and suggest that the Allison-built Merlins were superior to the ones built by Rolls-Royce...
http://forums.ubi.com/images/smilies/winky.gif

The_Stealth_Owl
08-24-2009, 07:45 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Flight_boy1990:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by The_Stealth_Owl:
http://i605.photobucket.com/albums/tt138/SILVERFISH1992/Owldontmess.jpg </div></BLOCKQUOTE>
http://i293.photobucket.com/albums/mm63/GringoBG/4444.jpg

http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

<STRIKE>Just kidding.</STRIKE> </div></BLOCKQUOTE>

http://i605.photobucket.com/albums/tt138/SILVERFISH1992/angry-owl.jpg

I wouldnt do that if I were you flight boy...

na85
08-24-2009, 07:50 PM
Stop spamming. How you haven't been banned yet is beyond me.

Viper2005_
08-24-2009, 07:58 PM
Power:weight is insufficient to get a grasp on performance since the rated altitude of the engine is extremely important.

Drag =Q*Cd*S
since power = force*velocity,
Drag power = Q*Cd*S*v
Q = 0.5*roh*v^2

thus

Drag power = roh*(v^3)*Cd*S/2

In level flight at constant speed, drag power = thrust power, so we can just write:

Power = roh*(v^3)*Cd*S/2

Rearranging,

(Power*2)/(Cd*S*roh) = (v^3)

Thus

v = ((Power*2)/(Cd*S*roh))^(1/3)

If you want to simply examine the effect of engine rated altitude upon aircraft performance, Cd and S may be eliminated.

Hence

"velocity factor" = ((power*2)/roh)^(1/3)

Look up roh from standard atmosphere tables for the rated altitude, or use a calculator such as:

http://www.aerospaceweb.org/de.../scripts/atmosphere/ (http://www.aerospaceweb.org/design/scripts/atmosphere/)

So for example, let's consider the V-1650-3.

Combat power is 1600 bhp in MS gear at 11800'.

1600 bhp ~ 1.12 MW.
roh at 11800' ~ 0.85475 kg/m^3.

velocity factor = ((2*1.12*10^6)/(0.85475))^(1/3) ~ 138

Alternatively, combat rating in FS gear is 1330 bhp at 23300'.

1330 bhp ~ 0.99 MW
roh ~ 0.58321 kg/m^3

velocity factor = ((2*0.99*10^6)/(0.58321))^(1/3) ~ 150.

So despite having less power, you'll go faster in FS gear at high altitude because of the reduced air density.

These results are in pretty good agreement with flight test data; there is a slight tendency for this simple theoretical approach to over-estimate the speed advantage available to fast aeroplanes at high altitude because it doesn't account for the increased drag and reduced prop efficiency caused by the higher Mach numbers associated with high altitude flight.

However, as first order calculations go it's pretty good. If you examine the performance of the Merlin's competitors at altitude using this method you'll start to see why the Merlin was such a successful engine.

Viper2005_
08-24-2009, 08:00 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by jarink:
You could get really mean and suggest that the Allison-built Merlins were superior to the ones built by Rolls-Royce...
http://forums.ubi.com/images/smilies/winky.gif </div></BLOCKQUOTE>

Since when did Allison build Merlins?

Methinks you are referring to Packard, who were an entirely different concern...

Waldo.Pepper
08-24-2009, 08:49 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
"I doubt that much of a laminar flow did actually develop under wartime conditions. </div></BLOCKQUOTE>

? Maybe I sure don't know - wasn't there. But I don't think that the ground crews and pilots went out of there way to trod all over the wing. Nor do I think they allowed the planes to deteriorate to the point where it looked as if they has spent a weekend off roading with the boys.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
... why the P-39 would be nearly as good as the P-51 </div></BLOCKQUOTE>

I don't think it was.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
... if the latter managed be heavier, larger and yet to go faster for the same power. As opposed to IceFires statement, this indicates the P-51 was a lot better aerodynamically. </div></BLOCKQUOTE>

Right, which is why the quote I supplied mentions "the high speed aerofoil" as well.

The Meredith effect has been mentioned as well. (I think by me in fact!) I have an article from I think Aeroplane Magazine [titled - We can build you a better airplane than the P-40] which did/or quoted some calculations that had been done which (from memory I think) mention that the radiator unit produced some 400 pounds of drag. But due to the Meredith effect, 350 of those 400 were negated. This would likely not be present on other planes of the era.

If any of this is valid I expect that this might make the difference.

I uploaded We can build you a better airplane than the P-40 here in case anyone wants to go over it which their Cherry Pickers.

http://rapidshare.com/files/27...an_the_P-40.pdf.html (http://rapidshare.com/files/271135296/We_can_build_you_a_better_airplane_than_the_P-40.pdf.html)

Viper2005_
08-24-2009, 09:23 PM
http://www.wwiiaircraftperform...mustang/rae1501.html (http://www.wwiiaircraftperformance.org/mustang/rae1501.html)

Surface finish of operational aircraft often left much to be desired.

Laminar flow was probably not achieved on operational P-51s during WWII. It seems likely that the majority of the P-51's performance advantage came from its radiator design.

This is corroborated by the disappointing performance of the Spiteful/Seafang.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Atwood maintained an active "retirement" schedule, corresponding with members of industry and authors, writing technical papers and attending as many aerospace-related events as possible. In July 1998, having just returned from a second trip in two years to England to lecture on the aerodynamic virtues of the P-51, Atwood was eager to discuss history as well as a few more recent events in aerospace.

During World War II, everyone was trying to figure out how the P-51 Mustang was out-performing German fighters as well as the British Spitfire, which had more horsepower and was 1,000 pounds lighter. The German aircraft manufacturer, Messerschmitt, was also researching the Mustang's performance to no avail.

Atwood explained, "Both the British and German engineers at the time thought you could test a scale model in a wind tunnel. But the wind tunnel models didn't generate the engine-heat factor, which we successfully controlled within the air scoop to create positive thrust. They were all looking at Mustang's laminar flow wing, which was noted for reducing air friction over the surface of aircraft wings."

Pointing to several mathematical equations, Atwood continued, "The laminar flow wing is great for jet airplanes or in a high-speed dive but had little effect on the P-51's overall performance envelope. You have to attribute the speed increase to the radiator energy recovery (positive thrust), not the characteristic of the wing itself. The wing did help in a dive -- not in level flight. I never mentioned this to anyone during the war."

Atwood credited F.W. Meredith of the RAE Farnborough, U.K., whose August 1935 report known as the Meredith Effect greatly influenced his work on the P-51 cooling radiator. </div></BLOCKQUOTE>
http://www.wingsoverkansas.com...s/article.asp?id=968 (http://www.wingsoverkansas.com/profiles/article.asp?id=968)

There used to be an article by Atwood explaining this in detail floating around the 'net, but I can't find it atm...

stalkervision
08-24-2009, 10:00 PM
http://ww2drawings.jexiste.fr/Images/2-Airplanes/Allies/1-USA/1-Fighters/XP-77/Left.jpg

with a far better engine.

JtD
08-24-2009, 10:32 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Waldo.Pepper:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JtD:
... why the P-39 would be nearly as good as the P-51 </div></BLOCKQUOTE>

I don't think it was. </div></BLOCKQUOTE>

Well, then maybe you leave it to the poster of the original statement (IceFire) to answer my question.

Thanks for uploading the pdf, nice read!

JtD
08-24-2009, 10:48 PM
As to the power of the Merlin 66, it was one of the most powerful aero engines available when built into the P-51. This is particularly true if you look at the power output at altitude, and not even necessarily up high. At 4000m it outperformed both German fighter engines of that time, the DB605 and BMW801, the Soviet M105-PF and ASh-82FN, all Japanese fighter engines I can think of and know enough about and the US Allisons and P&W R 1800's in various installations.

This essentially leaves just the Sabre and the P&W R-2800 as more powerful engines.

Viper2005_
08-24-2009, 10:56 PM
And of course "We can build you a better airplane than the P-40" was the article I was referring to. Amazing how these things are often under one's nose as it were...

Bremspropeller
08-25-2009, 05:10 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">As to the power of the Merlin 66, it was one of the most powerful aero engines available when built into the P-51. This is particularly true if you look at the power output at altitude, and not even necessarily up high. At 4000m it outperformed both German fighter engines of that time, the DB605 and BMW801, the Soviet M105-PF and ASh-82FN, all Japanese fighter engines I can think of and know enough about and the US Allisons and P&W R 1800's in various installations. </div></BLOCKQUOTE>

You're right on that. But there's a difference between max rated power-output and power-output over altitude with the help of superchargers.

You can add "efficient supercharger" on the "have" list, but that won't change the issue that the Merlin wasn't among the most powerful engines at the time it was built into the Mustang.

Does anybody have some data for comparing L/D of some fighters against the Mustang's?

BillSwagger
08-25-2009, 08:27 AM
I'm not sure there's been any mention of prop designs yet.
Its said that late war Allied propellers were ahead of the curve compared to German contemporaries, so you might actually see similar airframes with a disparity in horsepower but achieving similar performance due to a difference in prop designs.

For example, you might notice the German 109 prop has a triangular design, where the Mustang's is closer to a paddle design.
The reasons for the more coned shaped design was to reduce drag at higher speeds, at the cost of acceleration.
The paddle design works toward improved acceleration but at the cost of higher top speeds.

This is all relevant considering that as the war advanced the allied designers had shifted away from "tooth pic" props and had done significant research on how the horsepower was translated into thrust through different sections of the prop blades. So we start to see more paddle blade designs, with differing chords and widths, to maximize thrust and horsepower. German paddle blades look remarkably similar, but a majority of their inventory was still using the three cone shaped bladed props with only adjustments made to the width of the blades.

So, to me, talking horsepower output and drag coefficients is somewhat moot if you're comparing planes that use entirely different prop designs.

JtD
08-25-2009, 09:33 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bremspropeller:

You're right on that. But there's a difference between max rated power-output and power-output over altitude with the help of superchargers. </div></BLOCKQUOTE>

This is linked, you can't separate it. If you have to power only a small supercharger, the net output of the engine is naturally larger. The Germans simply sacrificed altitude performance for power on the deck, it's a change of power distribution, not more power.

DrHerb
08-25-2009, 10:30 AM
Well, I went googling around trying to find a drag comparison chart between ww2 aircraft. Theres not much around, but I ran into this..

http://www.hobbybokhandeln.se/j22/images/cd_0.jpg

From this website...

http://www.hobbybokhandeln.se/j22/aero.htm

Unfortunately it's missing ALOT of aircraft http://forums.ubi.com/images/smilies/bigtears.gif

Viper2005_
08-25-2009, 11:12 AM
L/D is reasonably easy to calculate.

In level flight at maximum speed, thrust = drag and lift = weight.

Weight is known, so lift is known.

Thrust may be calculated to a good approximation.

Power = Thrust * Velocity.

Velocity is known.

Power is known.

Thus:

Power/Velocity = Thrust.

Note however that the prop efficiency is not 100%. I'd say that 85% is a reasonable first order guess for high speed level flight, so we can write:

0.85*(Power/Velocity) = Thrust

Now, the prop efficiency is a guess. But the error is unlikely to exceed 10% in either direction...

Because Thrust = Drag, we know the Drag.

Hence we can calculate the L/D.

It should be pretty easy for anybody with the time and inclination to calculate the L/D of various fighters using this methodology.

I would advise performing the calculations in SI. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Lt_Letum
08-27-2009, 11:04 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by na85:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Lt_Letum:

Nosing-down and pulling-up both cause an energy
drop. The harder you do it, the more energy you
lose. </div></BLOCKQUOTE>

Any maneuver in an aircraft causes an energy drop. </div></BLOCKQUOTE>

Rubbish!
Many maneuvers result in energy gain.
Climbing, stall recovery, acceleration, takeoff...