P-51D maneuvrability - what it was in reality ...

[BarnOwlLover]

And I do believe that the above poster's P-51B book (talks about I believe the NA-73X and it's evolution from P-509 to flying prototype, to the production Allison Mustangs and the development of the Merlin models--Mustang X, XP-78/XP-51B, and P-51B production aircraft) and it's upcoming sequel (that is planned to discuss the P-51D, lightweight P-51s, P-51H, P-51M and possibly the XP-82/P-82B) would have a lot of material that talks about how the wing actually worked.

I should note that from what I've read and been told, though all I've written is true, the two books focus on the "unsung heroes" of the Mustang saga (P-51B, LW Mustangs, P-51H and P-51M, as well as the Merlin Twin Mustangs if he's able to get that far).

 

[GrauGeist]

I find focusing on the Mustangs that actually saw service (and combat) far more interesting than pursuing the Mustangs that never were.

It's sort of like being infatuated with the Messerschmitt Me309, which had potential but never progressed beyond the testing stage, while the Bf109 and all it's variants were far more fascinating to follow.

 

[Clean32]

in a word 'Balderdash'

which bit ?

 

[Deleted member 68059]

which bit ?

These jumped out in particular as indefensibly incorrect, the spelling alone is stunning.

"it was not actually a Lamour flow was quite Fat and dragy"

"the overall wing design was not less dragy that say a spitfire."

 

[Clean32]

These jumped out in particular as indefensibly incorrect, the spelling alone is stunning.

"it was not actually a Lamour flow was quite Fat and dragy"

"the overall wing design was not less dragy that say a spitfire."

sorry about my spelling, i didn't realise that this was a selling bee site.

the P51 wing is not actually a laminar flow wing. close but not the case, liberator had a laminar flow wing but not the P51. i don't have to defend it because it's simply a fact. anyone looking at the profile can see that it is not a laminar flow profile.
as yes it is quite a fat wing, how do you fit .50 brownings in there? logic dictates fat = dragy.

the overall wing design was more draggy than a spitfire. fuel economy, critical and terminal Mach numbers demonstrate that ( in combination with the fuselage etc)
now i wrote that not to make the spitfire look good or better or to make the P51 look bad, because neither were bad.

 

[bobbysocks]

HAHA. I have flown planes...nothing like a 51, 109.. mind you but Cessna, Piper, and Stensons. I have also flown sims since the 90s. When you are sitting on your couch or floor with a joystick in your hand flying a sim you are void of all the forces that pilots must face, fight, overcome. You don't feel G forces. OH you might have force feedback to give you a harder stick or your screen black out or vibration in the joystick. Even a 2 or 3 G maneuver make your arms feel like they are made of lead. Your ass buries itself in the seat where you can feel the treads and your stomach goes into your throat. To be in combat like that wears you out physically. It flat out fatigues you worse than any workout you can imagine. I dare say some pilots only lost the battle because they were more physically spent than the other pilot. Sims will give you a fundamental understanding of flying but when you are bouncing up, down, left, right, on final approach and trying your keep your nose on the runway and airspeed above stall speed...then throw a 15 knot crosswind ( which wing do your dip..what rudder pedal ) life gets REAL exciting. To bring this more home. I have known people selling wrecked ultralights who thought sims were as good as flight instruction. I almost bought one. These guys were lucky to be alive.

 

[BarnOwlLover]

None of this adds ups. One, the Spitfire's wing could house 1 .50 Browning and 1 20mm Hispano cannon, or 2 20mm Hispano cannons in each wing.

And two, the P-51 overall is significantly less draggy than the Spitfire. On the same power, the P-51B/D was 35-40 mph faster at least than the Spitfire IX. That speaks to better aero alone.

I'm far from knowledgeable on the detailed intracices of aircraft, but even I understand this.

 

[GrauGeist]

HAHA. I have flown planes...nothing like a 51, 109.. mind you but Cessna, Piper, and Stensons. I have also flown sims since the 90s. When you are sitting on your couch or floor with a joystick in your hand flying a sim you are void of all the forces that pilots must face, fight, overcome. You don't feel G forces. OH you might have force feedback to give you a harder stick or your screen black out or vibration in the joystick. Even a 2 or 3 G maneuver make your arms feel like they are made of lead. Your ass buries itself in the seat where you can feel the treads and your stomach goes into your throat. To be in combat like that wears you out physically. It flat out fatigues you worse than any workout you can imagine. I dare say some pilots only lost the battle because they were more physically spent than the other pilot. Sims will give you a fundamental understanding of flying but when you are bouncing up, down, left, right, on final approach and trying your keep your nose on the runway and airspeed above stall speed...then throw a 15 knot crosswind ( which wing do your dip..what rudder pedal ) life gets REAL exciting. To bring this more home. I have known people selling wrecked ultralights who thought sims were as good as flight instruction. I almost bought one. These guys were lucky to be alive.

Agreed and how's this for real life?

Get caught in a line of thunderstorms in a Cherokee Warrior with only a VFR rating over a mountain range with peaks about 12,000 ASL - no sim on earth can replicate that experience...

 

[pbehn]

sorry about my spelling, i didn't realise that this was a selling bee site.

the P51 wing is not actually a laminar flow wing. close but not the case, liberator had a laminar flow wing but not the P51. i don't have to defend it because it's simply a fact. anyone looking at the profile can see that it is not a laminar flow profile.
as yes it is quite a fat wing, how do you fit .50 brownings in there? logic dictates fat = dragy.

the overall wing design was more draggy than a spitfire. fuel economy, critical and terminal Mach numbers demonstrate that ( in combination with the fuselage etc)
now i wrote that not to make the spitfire look good or better or to make the P51 look bad, because neither were bad.

If you can deduce drag and laminar flow just by looking at a wing why did or do thy need wind tunnels? F1 cars dont look fast, only the fact that they are makes them seem so and they all look equally fast or slow while in practice there are huge differences. Nobody at NAA claimed the P-51 Mustang I had a laminar or lamellar flow wing, it had a high speed low drag wing and being "fat" is a distinct advantage, giving more room for fuel, munitions wheels and any other stuff. With the same engine the P-51B /D was faster and more economic than the Spitfire at all speeds up to the transonic range but at those speeds you are in danger of structural damage and props falling off. The lower drag of the P-51 was only partly due to its wing, the cooling set up was better and the overall design and build of the fuselage was better. A layman's logic dictates that fat = draggy but research by NACA showed that putting the thickest part of the chord further back delayed the onset of turbulence giving less drag in the speed ranges that prop aircraft use.

Edit, I studied metallurgy the words laminar and lamellar were used as synonyms, I have also seen the same in aerodynamics, is there actually any difference?

 

[drgondog]

Good luck, while there is a lot out there none of it is definitive and all requires interpretation as well as all being incomplete.

I have 9 complete wind tunnel reports ranging from 1/4 and 1/3 scale at NAA and Galcit, several from NACA Ames and Langley. Many are, or were available on internet, especially important ones. Lo and behold if you have the aero background they do not require 'interpretation', nor are they incomplete. They range from profile/parasite drag component development, pressure distributions in the entry duct/radiator matrix of the cooling system, transonic flow development, dive tests, stability and control damping, full scale compressibility, Thrust development and measurement testing of P-51H at 90"P, etc, etc.

so it very hard to get a good picture.
for example the P51 Near Laminar flow wing as it was not actually a Lamour flow was quite Fat and dragy.

Balderdash, BS, not in the ballpark with respect to comprehension.

While the ROOT chord of the Mustang wing - both NAA/NACA 45-100 and the NACA 66 series - was 'fatter' than the Spitfire (16.5 to 13% T/Cmax), the resulting Profile/Pressure drag as function of Drag Cofficient to Lift Coefficient ratio was superior for entire range of cruise to top speed. The Spitfire NACA 2213 wing section was an early 1930s design, with benevolent stall characteristics and a higher Max CL than the Mustang wing section. The actual effective T/C max, while lower than the Mustang, was less than you imagine as they both tapered to 9% (9.4 for Spit) thickness tips

The Profile drag component is the 'area' the freestream 'sees'. Due to the unique (1940) nature of the High Speed/Low Drag Mustang wing, the velocity gradient (and velocity) over the wing was more gradual from Leading Edge to Maximum thickness of the wing and the max T/C was ~20%+ farther from the Leading Edge of the wing than the Spitfire, Bf 109, FW 190, F6F, F4U, F8F, P-38, Me 262. Of those, only the Spirfire and Me 262 were slightly better in shock wave development at Mach No. > 0.65.

The freestream air was 'fooled' by point/region of the wing where the adverse pressure gradient formed to transition the Boundary Layer from 'attached' to ful blown separation. Ed Horkey had this notion and I tend to agree - this transition area was Past the Mac T/C of the airfoil section, where the T/C is decreasing and becoming 'hidden' from the fatter section. In the NACA 23016 (and similar) the pressure distribution of the airfoil peaks in the 25-30% range, whereas the NAA/NACA 45-100 peaks aft of the T/Cmax of 37.%

but it had a bucket load of advantages, it was fat enough to carry .50. it was actually 3 profiles, the inner wing being having quite a sweep. like a modern jet. the middle section being near laminar gave its controllable dive speed and its more conventional wing tips improved its low speed and tip stall characteristics. add to that it was bloody strong.
It was for its day a tech marvel and you can see its further development in the crescent wing of the valiant

See above. The 'inner' wing sweep acomodated the main gear, but it also had a reduced AoA relative to the wing Station 67.5 to provide a unique washout scheme - to delay separation at high AOA for inboard lift distribution, while still accomodating roll authority at the tip.

but back to your comment " reduced drag" the inner section being at such an angle did reduce drag. but the overall wing design was not less dragy that say a spitfire.

so when we do comparisons in wings. the near identical profile of the top and bottom of the wing meant that when the shock wave formed it would form at the same place top and bottom at the same time.
where for example a P47 had the shock wave form much slower but only on the top of the wing. forcing the aircraft nose down.
and another and very important fact is the tail of the P51 is very thin

That paragraph is incomprehensible. The P-47 wing formed a shock wave earlier (top and bottom) and closer to the LE. The decrease in Lift and movement aft of the wing aerodynamic Center resulted in pitch down Moment, combined with wake turbulence blanking the elevator, made the P-47 as hard to recover as the P-38. Installing the dive flap solved the problem by immediately creating a 'Pitch Up CM'

there are a myriad of really documented issues that can interfere or explain why this report is different to that report etc. for example, rearming the p51 required the amours to drag the ammo boxes over the wings, denting and scratching the wing skin. this had a large detrimental effect on the effectiveness of the wing. it was fixed by a ammo cartridge system.
but that added weight.

Both the ammo and gun bays are behind the max T/C of the wing, and are aft of the meticulous flush rivet,putty, sand prime process from LE to max T/C of the wing and are in that region where boundary layer separation is dominant. And no, the loading process was to lay the 50 cal linked belts into the ammo trays. Even the P-51-NA/Mustang I with 20mm was a belt feed system.

it reminds me of the spitfire and the universal wing. i think Parks wrote" it slower in the climb its heavier and we just don't want it" but manufacturing concerned got there way and the RAF got the universal wing, although not in its original form.
So if your looking for a definitive source of actual data on the P51 or any aircraft for that matter, well it just will not exist

PBehn summarized most of the points. Some in Bold above

 

[Deleted member 68059]

sorry about my spelling, i didn't realise that this was a selling bee site.

the P51 wing is not actually a laminar flow wing. close but not the case, liberator had a laminar flow wing but not the P51. i don't have to defend it because it's simply a fact. anyone looking at the profile can see that it is not a laminar flow profile.
as yes it is quite a fat wing, how do you fit .50 brownings in there? logic dictates fat = dragy.

the overall wing design was more draggy than a spitfire. fuel economy, critical and terminal Mach numbers demonstrate that ( in combination with the fuselage etc)
now i wrote that not to make the spitfire look good or better or to make the P51 look bad, because neither were bad.

"spelling".

Also the P-51 wing was so good even the Germans wanted to copy it, I believe they had slightly more sophisticated tools at their disposal than "looking" which
has been an unpopular technique in aviation to deduce performance for about the last century or so. The German aerodynamicists were all stunned how far back
the flow stayed attached, considerably further than standard profiles (which means it was working, nobody sensible thinks than a "laminar flow" wing can only
be called such if it has 100% laminar flow, it simply has substantially more laminar area than standard profiles, which is more than enough to really
significantly lower drag).

Also note that the Mustang wing area is 5% larger than mid-war Spitfires, meaning it has an even harder job to lower actual absolute total wing drag.

 

[pbehn]

Did anyone try fluffy dice hanging from the mirror to get a faster look?

 

[GrauGeist]

Pretty sure it was the Tiffy that had a "fat" wing which made the Spit's anemic in comparison.

 

[Thumpalumpacus]

sorry about my spelling, i didn't realise that this was a selling bee site.

the P51 wing is not actually a laminar flow wing. close but not the case, liberator had a laminar flow wing but not the P51. i don't have to defend it because it's simply a fact. anyone looking at the profile can see that it is not a laminar flow profile.
as yes it is quite a fat wing, how do you fit .50 brownings in there? logic dictates fat = dragy.

the overall wing design was more draggy than a spitfire. fuel economy, critical and terminal Mach numbers demonstrate that ( in combination with the fuselage etc)
now i wrote that not to make the spitfire look good or better or to make the P51 look bad, because neither were bad.

Laminar-flow is not the same as "thin". A laminar-flow wing has the thickest part of the wing positioned along the wing's chord in such a manner that the airflow at the boundary doesn't separate so quickly.

 

[pbehn]

Pretty sure it was the Tiffy that had a "fat" wing which made the Spit's anemic in comparison.

As I remember the "tale" Hawkers were acting on advice and the conventional wisdom of the time about future fighters. Mitchell at Supermarine ignored it and ploughed his own furrow. The error was learned quickly, but with the Typhoons other issues it took a while before the Tempest appeared.

 

[drgondog]

As I remember the "tale" Hawkers were acting on advice and the conventional wisdom of the time about future fighters. Mitchell at Supermarine ignored it and ploughed his own furrow. The error was learned quickly, but with the Typhoons other issues it took a while before the Tempest appeared.

If the above analogy was in reference to advances made in Laminar Flow airfoils, the early results of the NACA 45-125 (20%) didn't hit the news tands until 1939 North American was intrigued but realized that a 20% wing would produce profile drag exceeding desired limits - independent of sterling manufacturing practices? IIRC the Typhoon wing was a 19% T/Cmax section.

 

[pbehn]

If the above analogy was in reference to advances made in Laminar Flow airfoils, the early results of the NACA 45-125 (20%) didn't hit the news tands until 1939 North American was intrigued but realized that a 20% wing would produce profile drag exceeding desired limits - independent of sterling manufacturing practices? IIRC the Typhoon wing was a 19% T/Cmax section.

Nothing so specific, as I recall it was harking back to the old debate about top speed v manoeuvrability, advice I think from the RAE, The Typhoon design started in 1937 according to wiki it was a was a NACA 22 wing section, with a thickness-to-chord ratio of 19.5% at the root tapering to 12% at the tip. Immediately they had compression issues of various sorts.

 

[drgondog]

Nothing so specific, as I recall it was harking back to the old debate about top speed v manoeuvrability, advice I think from the RAE, The Typhoon design started in 1937 according to wiki it was a was a NACA 22 wing section, with a thickness-to-chord ratio of 19.5% at the root tapering to 12% at the tip. Immediately they had compression issues of various sorts.

Yep, same NACA 22xx series as Spitfire - just 50% 'thicker'.

 

[GregP]

sorry about my spelling, i didn't realise that this was a selling bee site.

the P51 wing is not actually a laminar flow wing. close but not the case, liberator had a laminar flow wing but not the P51. i don't have to defend it because it's simply a fact. anyone looking at the profile can see that it is not a laminar flow profile.
as yes it is quite a fat wing, how do you fit .50 brownings in there? logic dictates fat = dragy.

the overall wing design was more draggy than a spitfire. fuel economy, critical and terminal Mach numbers demonstrate that ( in combination with the fuselage etc)
now i wrote that not to make the spitfire look good or better or to make the P51 look bad, because neither were bad.

Doesn't matter if it is a spelling bee site. Sometimes my typing isn't all it should be, either.

It matters if you communicate what you intend.

If you're trying to get technical, be as correct as possible since that minimizes misunderstanding.

The critical Mach number has not too much to do with overall drag; it defines critical Mach: the speed at which a supersonic shock wave begins to form on the wing and/or fuselage. Overall, the P-51 is MUCH less "draggy" than the Spitfire. The main drags were profile drag of the lifting surface, profile drag of the fuselage, cooling drag, and friction drag.
The P-51D has the best fuselage drag of any WWII piston combat aircraft. Period.
The P-51D has very low drag near its top speed, compared with other aircraft of the time.
The cooling drag is close to zero due to the Merideth effect.
Friction drag is quite low compared with most other fighters.
The combined effects of these account for the P-51 being so fast on such ordinary power. Definitely faster than most Spitfires, despite being a ton or more heavier. Late Spitfires were faster than earlier ones, but that came with considerably more power. By the time the P-51H showed up, it had more power, too, and showed all Spitfires a clean pair of heels easily.

But, by that time, it didn't much matter because everyone was interested in jets anyway. The Hunter, F-86, and Gnat were all pretty decently close to one another in performance. The Gant just couldn't perform well for very long on only internal fuel. The EE Lightning, despite being a Mach 2 airplane, was similarly range-limited. I once had a former Lightning pilot tell me he COULD get to Mach 2, but only if he was headed "toward the fuel." He said, tongue in cheek, that if he ever got going Mach 2 headed away from the fuel, he'd never get back to the fuel.

The P-51 wing IS a laminar flow wing back about as far along the chord as any laminar wing in WWII was. Later, we got even better laminar flow wings, but not during WWII on a piston combat aircraft. For all it's supposed mastery, the Ta 152 wasn't faster than P-51H and not much faster than a Tempest/Fury/Sea Fury (close to the same family). Most the late-war super-pistons were quite good and quite comparable, regardless of country of origin. Everyone learned a lot during wartime development. Everyone had decent engines, at least when manufactured with care, decent fuel, and decent airframes.

The British were flying 4 and 5-blade props while the Germans were using very wide-chord 3-blade props all with similar power. The difference in top speed wasn't much.

Cheers.

 

[BarnOwlLover]

Also pertaining to the P-51, Merlin Mustangs were flown with 3 and 4 bladed props. Though the 4 bladed prop was standardized, testing showed no real performance difference.