You're absolutely correct, mate.





........................................you are wasting you're time!! 

I understand all this, but still, the fact remains that the NA blokes had the drawings which Curtiss were 'forced' to handover. But NA refuse to confirm the obvious 'temptation' was given into, to look at what the Curtiss people had come up with. Even in the face of their 'famous' 102 day feat (or however many days it was), they still mantain that they simply "tossed" such a valuable asset aside and went about designing their 'unique' fighter.      Ha!!!!!!!!

It means much to me that Curtiss, who were approached first for the 'much needed' high performance, high altitude fighter (shortly to have 'long range' added to the requirement), were unable to entertain the idea of such a project because they were busy stocking ALL the allied Air Forces with the fighter that held the lines for 3 years (bar the Spit), in every theatre of the war. 

Seriously, I know what you say is true, but we all have our favourite plane and we defend it, even when the odds are stacked high........like the P40.   

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Getting there...

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If you ever need an excuse Doug, just ask...

Charlie

Certainly lovely photos Hagar.  And a beautiful plane. As far as WWII birds go, I've only ever seen them up close in Museums and the Australina War Memorial (except when I flew in the Spit...... But I was too young to be that thrilled about the plane itself. Just a mixture of scared and exhilarated, is all I recall from my flight in "The Kangaroo Plane").

I do love the P51, although I prefer the B/C version (a bit faster and still looking like your 'classic' - 'framed canopy'/ridge back - WWII fighter). I know these things actually impeded the pilots ability to see, but I just like it. I also think the 'ridge back' arrangement contributed to some more 'longitudinal stability', which I feel may be lacking in your 'bubble canopy' types.

Most Australian pliots I have read accounts by, preferred their B/C's to the D, citing some sort of "lack of stability, especially in a tight turn against torque"

It (the P51) would be my next 'sentimental' choice after the P40, between which there is no comparison, because of the part it played in the RAAF after the P40 was finally discontinued as the 'frontline fighter' (although this was very late in the peice, and many pilots flew the P40 later variants up till the end of the war).

By the way. The ammo in the wing of that P51 is obviously 'empty' and harmless, but are there 'complete' guns in there (maybe with firing mechanisms missing)? Or are there just 'barrel ends' projecting out the front of the wing, with no 'body' inside? 

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I think this is borne out by the additions on some models of the dorsal fin in front of the main vertical stab.....seen here on a few models showing different canopies and cooler intake shapes........also of note is the differing heights and aspect ratios of the vertical fin on the later models, in an attempt to improve this longitudinal stability issue.......

Thanks for that set of profiles, Ken. I have seen it a few times in my travels, but to be honest, didn't notice the fin having been added on later D models.

Obviously, the Australian pilots that I mention, were not alone in their having criticisms of the D model in terms of this 'longitudinal stability'. I'm sure, for the manufacturer to make such additions, it would have to have been an obvious and commonly acknowledged problem for them to have engineered a modification.

I'm certainly no 'aerodynamics' expert. In fact, I understand little. But it seems to me that this 'instability' could well have had something to do with the abnormal speed 'bleed-off' in tight turns experienced by the D model (but not the B - another reason I prefer the B).

(Let me see if I can explain my idea without a knowledge of the aerodynamic terms).
It seems to me, if you are directing the plane to turn sharply (while using the elevator pivoting upwards, when the plane is 'banked'), the plane is going to want to tend to go in the original direction, belly first. Without a good degree of 'directional' guidance (for want of the correct term), like that which would be given by the 'razorback' or the added fin, the plane, when it eventually began to move in the direction required, will have spent much of it's speed being 'forced' by inertia belly-first in the original direction.  ???

I can picture it, but I don't know if I've been able to explain it  clearly. But anyway, in my head, it would seem to account for the 'bleed-off' of speed that the D experienced in tight turns. (Like I siad,  in my head, anyway  .

I always found it disappointing that the P51D, being such a wonderful plane, in most ways, could literally 'turn on a sixpence, but after having done so, you look at the ASI and find you've lost 100 knots somewhere in the process.

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This would appear to be the case...... ??? ???

Thanks mate.

I've forgotten more about aerodynamics than I ever knew which wasn't a great deal to start with.

Ken will know from his experience with R/C models that it's possible to fly an aircraft perfectly well on ailerons & elevator alone with no rudder at all, even doing basic aerobatics. Many popular sport models have a fixed fin with no rudder. On conventional piston-engined aircraft & gliders the rudder is used to help initiate turns but "opposite rudder" is often required to hold the nose up once the turn is established. In a real aircraft this tends to be instinctive & you might not even notice what you're doing with the rudder or what position it's in relative to neutral.

From what I do remember about aerodynamic theory, the problem with the bubble canopies is that modifying an existing design by cutting down the rear fuselage decking to fit them reduces the surface area of the fuselage profile. When the aircraft is banked in a steep turn the fuselage acts as a wing & creates its own lift. The deeper the fuselage, the more surface area & hence more lift available when banked. This also helps to maintain stability in the yaw axis in all normal flight conditions. Reducing the surface area of part of the basic airframe without compensating for it will upset the delicate balance of the original design & make it twitchy & less controllable.

Many WWII fighters had a short tail moment arm* & were by no means perfect in this respect to start with, suffering from instabilty problems throughout their time in service. The canopy itself might also disturb the airflow over the vertical tail surfaces, further reducing stability & control - especially at low airspeeds. Fitting a dorsal fin or using other methods for increasing the area of the fin & rudder will often but not always correct this problem. Fighter aircraft are flown to the limits in combat situations & the usual rules go out of the window. An aircraft with predictable flying characteristics & responsive controls throughout the speed range must be a great bonus to a fighter pilot.

I discovered to my surprise when I had a flight in one many years ago that the rudder is very rarely used in normal flight on jet fighters like the Hunter. It's only required for advanced aerobatic manoeuvres & steering on the ground.

*PS. The XP-37 in Prof's original topic is a perfect example. I suspect it suffered from longitudinal instability in the pitch & yaw axes. Lengthening the rear fuselage by even a couple of feet would improve it considerably, both in looks & performance. Leaving aside all aerodynamic theory, the old adage, "If it looks right, it will fly right" proves true more often than not.