Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: uptown on July 15, 2009, 07:06:25 AM
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Wiki says it had 6 .50 cals. Which one had the 20 mils ? I thought it WAS the A36 :confused:
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No it was a version of the P-51A.
The A-36 had two .50's in each wing and two in the nose, but they were in the bottom of the fusalage.
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No it was a version of the P-51A.
The A-36 had two .50's in each wing and two in the nose, but they were in the bottom of the fusalage.
Sorry Ranger but it was not the P-51A but the P-51 (no letter). The A-36 was based on the British Mustang I. The Mustang Ia had the 4 20mm cannons. The P-51A was the British Mustang II.
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The only USAAF Mustangs with 20 mm cannon were the 57 F-6A recon birds. The British Mk. IA also had 20 mm cannons, but the US didn't use that version. According to my sources, the Brits received 97 Mk. IAs.
<S>
Shubie
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The only USAAF Mustangs with 20 mm cannon were the 57 F-6A recon birds. The British Mk. IA also had 20 mm cannons, but the US didn't use that version. According to my sources, the Brits received 97 Mk. IAs.
<S>
Shubie
93 to GB
91-12001 > 12012
91-12028
91-12033 > 12072
91-12091 > 12130
55 to USAAC
91-11961 > 12000
91-12014 > 12027
91-12029 > 12032
91-12073 > 12081
91-12083 > 12090
All the above from the same contract were 20mm armed. The only difference between the British and American a/c was the camera fitted to the American a/c.
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Sorry Ranger but it was not the P-51A but the P-51 (no letter). The A-36 was based on the British Mustang I. The Mustang Ia had the 4 20mm cannons. The P-51A was the British Mustang II.
Thanks for the correction, though I'm not sure that the A-36 was based on any Mustang, I thought the A-36 came along before any version of the Mustang. I may very well be wrong and would appreciate the correction if I am.
Either way I think the A-36 would be a very cool addition.
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Thanks for the correction, though I'm not sure that the A-36 was based on any Mustang, I thought the A-36 came along before any version of the Mustang.
The A-36 Apache/Invader is the ground-attack/dive bomber version of the Mustang. The Mustang had already seen some action with the RCAF before the Apache/Invader was produced.
ack-ack
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With no funds for pursuit aircraft, as fighters were then called, Lt. Kelsey came up with a way to beat the system and get some additional Mustangs on order for the USAAC. Using some remaining funds for attack aircraft, Kelsey asked North American to develop a dive bomber version of the NA-73. Choosing A-36, which was the next available attack designation, Kelsey ordered 500 of these dive bomber versions on April 16, 1942.
wrongway
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So the British Mustang Ia had the birdcage canopy, dive flaps and cannons?
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So the British Mustang Ia had the birdcage canopy, dive flaps and cannons?
A-36 Apache/Invader was the only Mustang variant to have dive brakes. The Mustang Ia had the birdcage canopy and 4x 20mm cannons.
ack-ack
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cc :salute
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So the British Mustang Ia had the birdcage canopy, dive flaps and cannons?
No
Mustang IA = P-51:
(http://members.lycos.nl/carloslievens/Images/p51/ia.jpg)
(http://www.cybermodeler.com/special/images/mustang_01.jpg)
Allison Engine, 20mm cannons.
A-36 = A-36:
(http://www.military.cz/usa/air/war/bomber/a36/a36b.jpg)
(http://www.warbirdsresourcegroup.org/URG/images/a36apache-2.jpg)
Allison engine. 6 .50 cal. mgs. 4 in the wings. 2 in the nose under the engine. Dive brakes. First Mustang model with under wing shackles for bombs.
Mustang II = P-51A:
(http://www.triofarms.com/album/Planes/slides/P51A%20Mustang%20-%20Over%20Burma.jpg)
(http://www.mustangsmustangs.com/p-51/p51variants/images/P-51A.jpg)
Essentially an A-36 without the dive bombing equipment and 2 .50's removed from the chin to save weight.
wrongway
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My father in law worked on the dive brakes and oleo struts for the A36 ground support model. He said the pilots liked to pop the dive brakes and scare the crap out of people on the ground in a low pass.
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Why do only the american planes have bubble canopies?
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Why do only the american planes have bubble canopies?
(http://www.hsgalleries.com/gallery04/images/Typhoons%20in%20flight.jpg)
(http://www.dday-overlord.com/img/avi/hawker_typhoon.jpg)
(http://upload.wikimedia.org/wikipedia/commons/a/a3/Supermarine_Spitfire_Mk_XVI_edit4.jpg)
Brits had 'em first.
wrongway
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Before the 190A?
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North American was having trouble selling the Mustang (NA-73X) to the Air Force. As part of the export agreement of wartime goods two examples of the P51 were delivered to the USAAF Air Material Command for evaluation where they remained sitting in the sun until it was determined that the USAAF and Navy needed a test of air-pneumatic gun chargers and the P51s were packed and sent to Eglin for testing. The 'Oh S**t' moment came when the P51 was dived toward the gun target and from 12000 ft broke 500 mph and the pilot overshot the target. After the succesful gun test the report sent to Wright Field indicating the tremendous flight performance of the Mustang caused quite a stir.
USAAF Procurement then revisited the NA offices and discovered that North American had not been waiting for them. Moving on their own initiative and realizing the need for an attack aircraft in the inventory (North American was known for this type of innovation) they had moved ahead and designed and constructed the aircraft that would later become the A36 Apache. The Army initially called the aircraft the F-6a and adopted the factory 'Plan' name of Apache. To the Army the P51 and F-6a and A36 were all called Apache in the beginning and it was later changed to Mustang. No one has ever explained why the Mustang should have the honor of adapting the British name when no other type was ever treated in the same manner.
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No one has ever explained why the Mustang should have the honor of adapting the British name when no other type was ever treated in the same manner.
No other type? The Lighting got its name from the British, otherwise it would have gone by the rather lame name of "Atlanta".
ack-ack
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The P-38 did not go into service with the Army as the 'P-38 Atlanta' and then get renamed.
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The P-38 did not go into service with the Army as the 'P-38 Atlanta' and then get renamed.
The A36 and the P-51 are to very different aircraft. Enough so that the designations remained distinctly different.
They do share some nifty looking comparisons when looked at in profile though... I can understand why it confuses most.
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I saw an A-36 last weekend (at Dayton), and it looks like a pretty cool airplane. I'd fly it.
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The A36 and the P-51 are to very different aircraft. Enough so that the designations remained distinctly different.
They do share some nifty looking comparisons when looked at in profile though... I can understand why it confuses most.
While what you say is true there may be people that come along behind us and think what you have said somehow disputes what I have contributed here so I will clarify what I mean.
The NA-73X project was acceptable to the British and the aircraft further evolved into the Mustang line (NA-91). The NA-73X line in its purist form becomes the P-51 and is further evolved into an attack aircraft as the A-36. From the very beginning the 'Plan name' of both projects is Apache. Furthermore the aircraft is first called Apache as it enters into US Army inventory. 55 of the NA-91 line (P-51s in Air Force terms) are retained by the Army for modification into photo reconnaissance and are designated F-6A. All of the pilots first assigned to Peterson Field Colorado were trained in F-6A Apaches which within the first month officially became F-6A Mustangs.
This is touched upon just briefly in the book "Mustang: The Story of the P-51 Fighter" by Robert W. Gruenhagen on page 60 where he writes (following the 'Oh S**t' moment I mentioned above):
At this time the Air Force accepted the Mustang and in an effort to establish its new mission and identity the name "Apache" was assigned to the P-51. By the time the "Apache" was received by flying units the designation had been changed to F-6A indicating a photo recon ship and the name was accepted as Mustang to conform to the standards being established by British use of the aircraft.
More than 800 pilots would be trained in the F-6A and some of them would later fly the A-36 Apache in a photo recon role.
Also the A-36 was the first of the Mustang line that allowed for the mounting of bombs or external fuel tanks. The A-36 played a pivotal role in inventory acceptance and so it most certainly should be present in AHII.
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Actually, It was the A-36 Invader.
:D
Really.
wrongway
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Thats funny because Army personnel actually did call it (the A-36 anyway) the Invader but it never stuck.
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Before the 190A?
Westland Whirlwind had it first, IIRC.
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ty
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Thats funny because Army personnel actually did call it (the A-36 anyway) the Invader but it never stuck.
From a 1941 copyrighted book "Warplanes in Action!" I found in an old relatives stuff. Thought it interesting
(http://i152.photobucket.com/albums/s199/guppy35/Apache.jpg)
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The A-36 played a pivotal role in inventory acceptance and so it most certainly should be present in AHII.
here here :salute
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That is an interesting pic Dan. High altitude battles with an Allison powered airplane.?????
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That is an interesting pic Dan. High altitude battles with an Allison powered airplane.?????
Most definately 1941 make em feel better propoganda
The book also describes the Devesator as the Navy's "Mighty Torpedo bomber!"
descriptions of the Airacobra and others follow that same path :)
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Most definately 1941 make em feel better propoganda
The book also describes the Devesator as the Navy's "Mighty Torpedo bomber!"
descriptions of the Airacobra and others follow that same path :)
So your saying our leaders of the day lied to us? :O
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That is an interesting pic Dan. High altitude battles with an Allison powered airplane.?????
I think at the time that propaganda drawing was released the war department probably didnt want too many people talking about service ceilings but I also dont think too many airplanes were operating much higher than the Apache could operate. The push for high altitude operations was just beginning at that point. Notice in Guppys drawing that the number of exhaust cylinders are not clear the tail looks nothing like the 'Apache' and you cant even tell how many guns it might have.
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IThe push for high altitude operations was just beginning at that point.
P-38 and P-47 were purposefully designed with turbos instead of a multi-speed superchargers. The B-17 and B-24 were purposefully designed with turbos instead of multi-speed superchargers. All of these aircraft were designed before the war started for the U.S., and had turbos for high-altitude design missions. The only reason the A-36 had a single-speed super'd Allison was its design mission--ground attack.
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Yes I understand the Americans had designs for high altitude and thanks for pointing that out. When the first prototype NA-73X rolled out they didnt have an engine at all but the designers must have been thinking far ahead because the design details of this project didnt really make for much advantage until the plane was at higher altitudes. Now concerning the A-36 itself I would agree it was intended to fill a role that North American knew the Army had to fill yet but no one else was considering. When I think of the German or Japanese projects that eventually fill the high altitude roles I can only recall late war designs. Nothing about the time of the A-36 comes to mind as being intended for high-altitude but of course I tend to stick to familiar territory and that would be the Mustang projects.
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the design details of this project didnt really make for much advantage until the plane was at higher altitudes.
Considering the plane used the same Allison powerplant as the P-40 series, was heavier, and bigger than the P-40, it showed the aerodynamic efficiencies gained by the design, regardless of altitude. Those same efficiencies were demonstrated at the higher escort altitudes where the Pony truly developed its reputation.
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Im sorry but while what you say sounds good I dont believe it approaches the real reason the P-51 was better than the P-40. Aerodynamic efficiencies alone are in my mind at least a very small part of the picture.
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Stoney, the P-51 and P-40 were pretty close to being the same size.
P-40E
# Length: 31.67 ft (9.66 m)
# Wingspan: 37.33 ft (11.38 m)
# Height: 12.33 ft (3.76 m)
# Wing area: 235.94 ft² (21.92 m²)
P-51D
# Length: 32 ft 3 in (9.83 m)
# Wingspan: 37 ft 0 in (11.28 m)
# Height: 13 ft 8 in (4.17 m)
# Wing area: 235 ft² (21.83 m²)
weights
P-40E
# Empty weight: 6,350 lb (2,880 kg)
# Loaded weight: 8,280 lb (3,760 kg)
P-51D
# Empty weight: 7,635 lb (3,465 kg)
# Loaded weight: 9,200 lb (4,175 kg)
Mustang I
basic: 5990lb
Max gross: 8633lb
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Stoney, the P-51 and P-40 were pretty close to being the same size.
Hmm, right you are. Thanks for the clarification. Either way, same powerplant in the same sized aircraft, faster at sea level doesn't have anything to do with the supercharger.
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You are comparing the P-40 to the D model. The 1150 horsepower Allison V-1710-F3R was in the A-36 Apache but I couldnt tell you what the P-40 had so I will take your word it had the same engine.
A-36 empty - 6087
A-36 normal T.O. - 8600
A-36 max G.W. - 10700
Same horsepower as the P-40 similar weight and less area in profile but I dont think the airfoil really enjoyed a lot of advantage at sea level. Its tough to tell really how the weights compare without knowing what the different configurations actually were. I believe the A-36 carried more fuel for one thing.
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You are comparing the P-40 to the D model...
I dont think the airfoil really enjoyed a lot of advantage at sea level.
Yeah, apparently I did. But, the airfoil would be just as advantageous at sea level as it was at high altitude. The lower cooling drag and all of the other aerodynamic refinements of the Apache would be as apparent at sea level as they would at altitude. The two speed supercharger on the Packard Merlin was what gave the B and D models their high altitude performance, not aerodynamics. If they were looking for aerodynamics for high altitude, the P-51 planform wouldn't have been a 5.5 aspect ratio wing. To make it more aerodynamically suited for high altitude, they would have made it high-aspect ratio like the Ta-152.
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I dont think it is possible for that to be true. The engine enhancements you mention are intended to maintain the same atmospheric pressures as low altitude but the airplane performs better at 25k which is critical altitude for the D model. So if the engine output is the same (which only in a perfect world would it be the same) why does the D model perform better at 25k than at sea level?
Being a glider pilot I have a high appreciation of wingspan. :D
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I dont think it is possible for that to be true. The engine enhancements you mention are intended to maintain the same atmospheric pressures as low altitude but the airplane performs better at 25k which is critical altitude for the D model. So if the engine output is the same (which only in a perfect world would it be the same) why does the D model perform better at 25k than at sea level?
Being a glider pilot I have a high appreciation of wingspan. :D
Dynamic pressure is the term used to describe the relative density of the air at a certain speed. It is represented by the term "q" in most equations, and is = to:
1/2*p*v^2
Where p = density of air and v = velocity
At altitude, air density is lower so dynamic pressure is lower, so skin friction drag is reduced. The constant amounts of manifold pressure that are created by the turbo or supercharged induction systems, generally speaking, create constant amounts of thrust. We also know from the thrust equation that an aircraft that is at equilibrium:
Thrust = Drag
If the engine produces the same amount of thrust up to critical altitude, thrust in the equation is constant. If the drag is reduced due to lower dynamic pressure, then the velocity of the aircraft will increase, so that the True Air Speed of an aircraft will continue to increase, with the same amount of thrust being applied in the face of decreased friction drag. So, the aircraft will continue to fly faster, until the constant thrust accelerates the aircraft to a speed where the drag and thrust components reach equilibrium again. Generally speaking, all aircraft fly faster with increases in altitude, at least until they begin to lose thrust (either less engine power or prop efficiency) or the drag component begins to increase despite lower dynamic pressure (typically because of higher induced drag).
So, generally speaking, lower drag at altitude means faster planes, even if the engine power remains constant.
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Yes and following your own argument then an airplane with a smalled profile will be faster still in thinner air than an airplane with a thicker and coarser profile will since it will require less horsepower and result in less drag also.
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Yes and following your own argument then an airplane with a smalled profile will be faster still in thinner air than an airplane with a thicker and coarser profile will since it will require less horsepower and result in less drag also.
Not necessarily. The Spit 9 versus P-51 is a good example. Even though they are both powered by the same engine, and the P-51 is larger and heavier (I double checked this time :) ), the P-51 is still faster. The Spit airfoil is also thinner at the root than the P-51, but still generates more drag. My original point is the same though--the aerodynamic design of the P-51 was more efficient at all altitudes, not just at high altitude.
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Quick question.
Wouldn't drag be more noticeable down low where the air is thicker?
(http://www2.hitechcreations.com/ahhelp/models/charts/spit9spd.gif)
(http://bbs.hitechcreations.com/wiki/images/thumb/4/45/P51dspd.jpg/300px-P51dspd.jpg)
Isn't there a larger speed dif at sea lvl than say 25k?
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Well, I'm going to spit-ball for a second. Perhaps, given the aerodynamic efficiencies of the P-51D are mainly efficiencies created by lower parasitic drag, that at high altitudes, where parasitic drag makes up less of the overall drag, and where induced drag makes up more of the overall drag, the Pony will enjoy a smaller speed advantage. At sea level, where more of the drag is parasitic, we see a larger discrepancies in the two top speeds. Assuming both the Spit 9 and Pony are making the same amount of thrust at all altitudes, the lower parasitic drag of the Pony would enable it to be even faster at sea level than it would at altitude.
This is a simplified example, but I believe it is probably what a more detailed analysis would reveal. Ultimately, its the ability for the Pony to make full rated horsepower up to a very high critical altitude that gives it its excellent high altitude performance, not unlike its peer the P-47, which certainly did not earn its high-altitude performance from being dainty.
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Not necessarily. The Spit 9 versus P-51 is a good example. Even though they are both powered by the same engine, and the P-51 is larger and heavier (I double checked this time :) ), the P-51 is still faster. The Spit airfoil is also thinner at the root than the P-51, but still generates more drag. My original point is the same though--the aerodynamic design of the P-51 was more efficient at all altitudes, not just at high altitude.
I dont believe thats accurate. The P-51D and Spitfire IXc have nearly identical wing root thicknesses (and other dimensions). The Spit is lighter and has maybe 50hp more. Also the induced drag of the Spitfires airfoil will always be more severe than the induced drag of the P-51. Thats the whole reason for the airfoil chosen for the Mustang. Also the relationship of the two forms of drag are not a function of altitude but of airspeed (parasitic increases dramatically with greater airspeed and the reverse being true of induced drag). Probably your opinion of the root sections is greatly biased by the fillets which are added to reduce interference drag (one component of parasitic drag) but interference drag was never a severe problem with the P-51. It may have been an issue with maintaining pure laminar flow.
Looking at those tables its hard to believe laminar flow was considered with AH at all or that the Spitfire was given the same advantage but I am not an aerodynamicist just a hobbyist glider pilot.
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I dont believe thats accurate. The P-51D and Spitfire IXc have nearly identical wing root thicknesses (and other dimensions). The Spit is lighter and has maybe 50hp more. Also the induced drag of the Spitfires airfoil will always be more severe than the induced drag of the P-51. Thats the whole reason for the airfoil chosen for the Mustang. Also the relationship of the two forms of drag are not a function of altitude but of airspeed (parasitic increases dramatically with greater airspeed and the reverse being true of induced drag). Probably your opinion of the root sections is greatly biased by the fillets which are added to reduce interference drag (one component of parasitic drag) but interference drag was never a severe problem with the P-51. It may have been an issue with maintaining pure laminar flow.
Looking at those tables its hard to believe laminar flow was considered with AH at all or that the Spitfire was given the same advantage but I am not an aerodynamicist just a hobbyist glider pilot.
Not counting the wing root fillets, the NACA 45-100 used on the P-51 had ~15% root thickness. The Spitfire, until the late models where they completely redesigned the wings, had a NACA 2412 root which is 12% thick. At higher angles of attack, the Spitfire airfoil will create lower profile drag than the P-51 airfoil. The higher the altitude, the higher the required angle of attack to achieve the same lift coefficient (remember like I said, dynamic pressure is lower, therefore airfoils produce less lift). So, at high enough altitudes, if say the Spit and Pony have to pull 6 degrees of AoA to fly level, the Spit could create lower amounts of profile drag.
Now, considering the differences in dynamic pressure, altitude changes the influence levels of the two main types of drag, parasitic and induced, just as speed does. The higher you fly, parasitic drag decreases and induced drag increases. The lower you fly, induced drag decreases and parasitic drag increases. The differences aren't as drastic as when you compare the differences created by speed, but the relationship is the same, and I believe probably accounts for the difference in speed at altitude, if we assume both aircraft create the same thrust on the same powerplant. I'm glossing over some details here, but I think the theory is sound from an aerodynamic perspective...Maybe one of the other guys can jump in and either validate or correct me. Regardless, a stimulating discussion.
EDIT: Removed a section that could have been confusing... :)
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Stoney the definition of a laminar flow airfoil is one designed for minimum drag and uninterrupted flow of the boundary layer. Yes if both the Spit and Mustang had non-laminar flow design then your description would apply but not as the aircraft really were designed.
In real life the Spitfires drag at high speed would increase at a much greater rate than on the Mustang both in level flight and while maneuvering. To some degree this is represented in the game by aileron responses that stiffen at higher speeds but the more I look at it and think about it the less realistic it seems because a maneuvering P-51 should not hit the same drag that a Spitfire does. There is a point at which the P-51 will experience more severe drag in hard maneuvers that would approach the drag of the Spitfire but also in standard turns it would not.
No I think you got the effects of dynamic pressure on these examples incorrect. I think in fact that the P-51 has to experience an AOA in excess of 15 degrees before it experiences turbulent flow.
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I think in fact that the P-51 has to experience an AOA in excess of 15 degrees before it experiences turbulent flow.
Most laminar flow airfoils have extremely low profile drag at their design lift coefficient angle of attack. Typically, anywhere from -2 to +2 degrees AoA off the design lift coefficient angle of attack makes up the "bucket" as its called, where laminar flow will exist. As this chart shows, the design lift coefficient of the Mustang is around 1, as indicated by the point of lowest drag.
(Ignore the NACA 23015 curve here)
(http://i125.photobucket.com/albums/p61/stonewall74/Cd_Comparison_SL150MPH.jpg)
Inside of that bucket, and around the design lift coefficient, the Mustang will display much lower profile drag than the Spitfire. I haven't done a drag polar on the 2412 airfoil for display, but at some point, probably around 6-8 degrees AoA, I'm guessing the Spit will show lower profile drag than the Pony, not unlike the polar for the 23000 airfoil shown in the chart. Basically, laminar flow exists inside the "bucket" with increasingly turbulent flow outside of it.
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Stoney what does that chart look like at 450 mph?
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Stoney what does that chart look like at 450 mph?
Probably close to the same, except that the overall drag numbers will be lower. I'll see if I can't get some polars together at that speed, but XFOIL doesn't like high Reynolds numbers, so they could get a little goofy. While I'm doing that, I'll also do some 2412 plots.
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I thought I had heard somewhere that the radiator outlet (under the cockpit) actually produced a small amount of thrust which negated (slightly) drag of the propeller. Can't remember where I heard this of if it's even correct.
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I looked into the Spitfire to see if I could compare airfoil data from P-51D to Spitfire (any model) and discovered that at no time did the Spitfire have a NACA 2412 airfoil.
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You're right. I mispoke earlier and called it a 2412, when in fact it was a 2213.