Originally posted by justin_g
The MTT dive trials with Me 109F were at 100% engine settings, and they reached Mach 0.8. Dive angle was 70-80º.
Drag is not the limiting factor, the wing design is. For typical WW2 fighter wing designs, thinner was better(measured as ratio of thickness:chord at the wing root) - Me 109 with 15% thickness had a limit of about 0.8M, which closely matches the dive speed limits in the pilots manual. P-51 had 16% thickness, and a dive limit of 0.75M per the POH. Spitfire wing was 13%. Pilots notes give a dive speed limit corresponding to 0.85M. This Spitfire dive table reports 0.891M reached.
How can someone seriously believe that in a 45° dive, that means only 70% of your weight actually pulls you down (engine power can be neglected), a prop fighter can achive 0.88 ??? Oh yeah, while other fightres were barely able to reach 0.8 in vertical dive, the spitfire needed only 45° to outdive them by almost 0.1mach lol. And this only by a "very thin win" what´s actually not true at all in comparison to the 109.
The 109 did not have 15% thickness. Even the earliest models had a 2314-2311 airfoil combinition. The 109E had 14.2%/ 11% thickness combination. The 109F had a 14.5% / 11.35% thickness ratio combintion, the 2nd one is measured at the outside of the ailerons
The spitfire was betwen 12 and 13% in the roots, a RAF report mentions 13% straight on. The low tip ratio is an illusion due to the elliptical shape. The ratio varies with the depth, and elliptical shapes are not very deep at the VERY outside. For example thunderbolt, inside 16%, outside 9%. It´s just depends where you measure, and elliptical shapes seem be very thin on the outer part - but that´s more an illusion due to the elliptical shape. which get´s quickly larger when you move inside.
Furthemore the gradient of the spitfire wing was maybe even steeper because it had the maximum thickness ration already in 20%.
The P51 could not be dived fast because of the Allison engine. It hat to start in less than 30k.
The evaluation of the test is nice but useless. The whole report mentions how difficult the evaluation was. It´s just a guess. I´d like to know how germans did it. The german result looks way more reasonable when we compare it with our knowledge today.
I wonder why they did not test by cameras. If the pilot dives down and you film it with a highspeed camere, the same you use for speed records, you should be able to calculate by triangular formulas in a very simple way the max. speed.
A FW-190 report mentions how bombs under the wing can influence the speed indicator even in normal flight. Now think how a tube is influenced near mach 1.0 by the wing alone. You have to calibrate the whole machine when the tube is mounted, not the tube alone.
niklas
