Lift to Drag Ratios Compared

[AndyJWest]

My gaming PC is currently out of action, otherwise I'd repeat a test or two with 4.10, to see if anything has changed. With regard to testing, I'd recommend doing this with 'Wind and Turbulence' off, as with it on you can get different results depending on the time of day! As you say, the 'true' ground effect is unlikely to affect your results in most cases, but the W & T pseudo-ground-effect seems to occur at significantly higher levels. All rather strange...

[JG27_PapaFly]

Originally Posted by Letum

Anyone got a graph that compares wing area and weight to vertical speed and TAS for a theoretical plane?

That would be nice to see.

For example, it would show the extent to which ww2 planes would have better energy retention if they had more weight.
i.e. what's the optimum fuel loadout in a P51 for the best energy retention or the highest wingload to v-speed ratio.

That would be nifty.
This NASA document states a L/D ratio of 14.6 for the P-51. No idea whether that was a regular pony or the one they tested as a glider without propeller (see this NACA document).

In my tests, the P51 tops at an L/D of 11, which is quite plausible.

Energy retention depends on many factors, and is itself just one aspect of plane design. Compromises have to be made. In gliding, 2 design aspects are in conflict: one is energy retention, meaning the ability to cruise at high speed and loose as less altitude in the process as possible. The standard recipe to increase that energy retention at high speed is to load water ballast. One of the most advanced gliders, the polish Diana 2, can load more than double its weight with water.
However, just as important for gliders is a second aspect:the ability to turn very tight at slow speed. Thermal winds are very narrow, and the zone of the optimal lift is quite close to the core. The slower a glider can fly in a steep turn (45-60 deg bank), the closer to the core it'll be, and the better it will climb. While an empty glider will happily climbt into thermals at 80-90kph, a fully loaded one will do 110-120 kph, thus climbing less efficiently.
One way to bring both design requirements together is the use of flaperons. Modern gliders and jets make extensive use of these flaps that can go both ways: down to increase lift, and up to decrease lift + reduce drag. The F16 is a good expamle. Imagine a D9 or P51 using flaperons...they could prolly accelerate in level flight up to speeds where prop efficiency and compressibility would be limiting.

[JtD]

I think the 16 are calculated and without propeller. If you look at the NACA report, you get a (L/D)max of about 16.5 for the P-51B from the fig. 21 - without propeller. Seems reasonable from all angles to me.

[JG27_PapaFly]

Yepp, simulations have gone a long way...

After the energy maneuverability theory got widely implemented, modern planes are being tested and described in every possible way. Today's fighter jocks know stuff that nobody had at hand in WW2: corner speeds, turn rates, acceleration performance, performance for different climb profiles, turn radii, sustained turns and much more. Yet, by testing properly modeled simulated planes, we can find out stuff about the real planes that hasn't been covered in history books, and that sometimes wasn't even known at that time. When a bunch of good sticks duke it out online these days, the tactics are very much TOP GUN (in the most positive meaning of the word), whereas back in the days there was lots of trial, error, and luck.

I hope COD offers even better ways for us to test the planes, like proper g force readouts in replays.

[AndyJWest]

I hope COD offers even better ways for us to test the planes, like proper g force readouts in replays.

You can get this from DeviceLink in IL-2 (I think the parameter is described as 'overload' or something, but it is definitely G, and is available in a replay)