Roll rate

A unique aspect of the so called "Laminar Profile"
wings of the P-51 was they were relatively thick
compared to other wings and that thickness was at
about 50% of chord not 25% as is typical.

This is where the P-51 stored its prodigous fuel.

It also left room in the wing for internal pressure balancing:
if the aileron was deflected up the pressure at the wing
aileron hinge line was channeled to a bellows to reduce
aileron forces.

Internal balancing was added to the P-51B, the P-51A did
not yet have that facility.

That's because IJN aerial doctrine emphasized stall fighting at speeds of 150 mph. Why they thought that way when even early model A6Ms could achieve 330 mph in level flight is a good question.

dave I read that this requirement came from pilots requesting manoeuvre characteristics similar to the A5M, I know the listed requirements for the A6M were combat range and manoeuvre, combat flaps were added to the model 21, the original A6M in limited production were land based preproduction versions given to pilots in China for service evaluation. It maybe that the belief at the time was that low speed handling was more important than high speed manoeuvres with the presumption that enemy aircraft won't be doing 400mph in level flight. In China they dominated late-30s fighters but pilots requested more manoeuvrability and regarded speed as superfluous.

I read Italian pilots had similar leanings, some squadrons switched back to biplanes from Fiat monoplanes in 1940 because they were dissatisfied with the faster fighter's manoeuvre characteristics. They determinedly felt that aerobatics trumped speed. They learned better the hard way, like Mitsubishi did but the main reason for the fairy build of the Zero was for range, not manoeuvre. It was literally stripped to break long distance flight records, then shoved into combat with only guns fitted. Strip a Wildcat like that and it won't do combat so good outside its element either, as it was put an ace in a Zero and Wildcats will fall like autumn leaves.

Perhaps so for acrobatic superstars like Saburo Sakai and Hans-Joachim Marseille. Unfortunately such people comprise only about 1% of pilots. You need to create aerial tactics and build fighter aircraft that allow the other 99% to succeed. That's what made the Me-109 and Spitfire so good during the early 1940s. They could boom zoom while still being quite acrobatic in the hands of an expert.

Refering back to the NACA reports mentioned earlier on this Lateral Control thread. :

Summary of Lateral-Control Research NACA-TR-868

Summary of Lateral-Control Research NACA-TN-1245

Lateral Control by Spoilers at the DVL NACA-TM-1307

These reports, though post-dating the war by several years, are applicable to this forum as the research was done during it. Searching TN-868 will only interest those meaning to get an understanding of metals at impact velocities. Regards

Take a careful read on NACA 868. The chart that most peopple trot out from that report is not a measured roll rate for ANY of the aircraft on the chart.

It is the pb/2V roll helix angle calculated at 10,000 feet with 50 pounds of side force applied to the stick. In real life, most aircraft cannot meet the ideal helix angle, most didn't fight at 10,000 feet in Europe and, in combat, people applied whatever force was necessary to get the desired rersult or to hit the control stop, whichever happened first.

As a rough rule of thumb, the density of the air at 20,000 feet is one half that at sea level. So at 20,000 feet, you had to apply twice the aileron to get the same result as at sea level. Roll gets lot slower as you go up from there.

That information is not very evident if you just look at the chart. You have to read the report to find out the chart conditions. The conditions ar about 2 pages or so before the chart in the report.

Dean in "America's Hundred Thousand" says that anything under four seconds for 360 degrees was doing pretty well for a WW2 fighter. The P47 was not necessarily noted for a great roll rate but Bob Johnson in his book, "Thunderbolt" said the P47 could outroll the Spitfire with ease since the Spit rolled poorly. That was part of his tactics in beating the Spitfire in a mock dogfight. It is a myth that the IJN pilots in the Zero liked to dogfight. Their typical attack was a boom and zoom run with AC in line astern. Lundstrom devotes a good deal of the appendix in one of his books to IJN tactics.