Crumpp, your very good information.

Especially this one, P47d4 vs fw190a5? a6?

I bet that il2 4.11m can't simulate this.

Attachment 9504
There are some interesting records:

1) bf109g6as initially outdives spitfire IX LF, but spitfire overtakes 109 as speed building up.

2)fw190a5 initially outdives p47d, but p47d overtakes fw190a5 as speed building up.

3)Tempest and 109G's initial dive acceleration are roughly same, but Tempest outdives 109G easily as speed building up.


When speed building up, what happens to P47/P51/Tempest? There airscrew tips reach/break sonic barrier??? howabout 109/190's airscrew?

If Daidalos Team solve this "supersonic" issue, we''ll appreciate that.

Doesn't changing the blade angle keep the prop from going sonic in a dive?

That doesn't make sense because airscrew tip's speed is irrelevant to blade angle.

Airscrew aerodynamics is quite complex, one need to read a whole book to master that.

I'm not an engineer or a pilot. I understand that tip speed means velocity at the tip of the prop and it's faster at the tip then near the center. Theres some formula that describes rotational velocity.

my point is when they built these planes, I imagine the didn't want the tip to be breaking the sound barrier all the time, so they put governors on the engines and design the props to keep it from doing that. if your in a dive and ram air is pushing your prop to rpm limits, I'm pretty sure the operators manual is going to tell you that isn't so good and you need to change the pitch angle and slow the rpms/reduce the tip speeds or something might break or do damage when you get near your never exceed speeds.

Going back to your tempest example, will the pilot not try to do something to mitigate the effects of sonic tip speeds? Or simply, the prop design specs try to engineer that out of the equation as much as possible? It seems in your analysis, you assume not, that it is simply a function of prop length, max rpms of the engine and forward velocity. I just don't know if that is realistic. To me, it seems that tips speed breaking the sound barrier would be a rare event. So, not sure why it needs detailed modeling.

But then again, I only learn aviation stuff from playing this game.;)


Edit:

Relates to what I was thinking about. http://en.wikipedia.org/wiki/Scimitar_propeller

BlackBerry, I think what you're saying about Tempest vs. P-51C is about right, even if your sources are vague and not always the right ones (you're quoting a comparison between Tempest and Typhoon, for instance). A direct test between the P-51C and the Tempest V revealed that the "Tempest tends to pull away" - which is a marginal advantage for the Tempest. You've tested a marginal advantage for the P-51.
Given the average accuracy of the flight models, which was aiming at a 5%, this is something that simply may happen between individual planes, it is no indication that the general algorithm is wrong.
Mach effects are modelled, not extensive enough for accurate high speed performance imho, but they are there.
The differences in initial acceleration between individual planes is there, if you fly them properly. Some of the acceleration differences you see as simple statements "this one is better" has a lot to do with engine management. If say an Fw 190 and a P-47 cruise side by side and then go into a full power dive, the guy in the 190 slams the throttle forward and off he goes, while the guy in the P-47 adjusts mixture, then rpm and then the throttle and then starts to accelerate. Gives the 190 a two second head start. But even without considering this, if you compare a 190A-4FR with a P-47D-22 at medium altitude in 4.11, you'll be getting something similar to the test you quoted.

JTD, I'll make clear that I am not saying the il2 FM is wrong, on the contrary, I believe il2 is the best simulation of WII a/c, especially 4.11m has achieved "structute failure" at high G manoeuver. Well done Daidalos Team! And many of us just hope il2 go further to become PERFECT.


In il2 FM, the wing drag coeffiecent is a constant, since most a/c fly below 0.8 Mach, the result is very accurate. However, there is small flaw in high speed diving. See picture below:

Attachment 9519
Even the best prop diver---Tempest MKV can hardly reach 0.8 Mach in diving----maximum permissible airspeeds 540m.p.h. IAS below 10000 ft, but the airsrew==a twisted and rotating "wing" could exceed 0.8 Mach with its "tip" in a high speed dive.

As long as we could simulate "the balance of propeller power", il2 will be nearly perfect. Don't forget those exhaust tubes just behind airscrew! Exhaust boost!

Attachment 9515

In WWII, US had NACA-16 series airfoil(eg. 4-blade Hamilton), UK had ARA-D airfoil, German had Gottingen airfoil.

I just suspect that those engineers of Hamilton or Rotol intently designed very big 4-blade airscrews in order to optimise high mach performance at high speed.


P51D----Hamilton Standard, four-blade, hydraulic, constant speed, 11 feet 2 inches, non-feathering

Bf109----The propeller is a V.D.M.9 - 12087. Three bladed metal constant-speed with electric pitch change, hand controlled or automatic. Diam. 9' 10" Max. blade width 11 5/8".

Tempest MKV----All versions of the Sabre drove four-bladed, 14 ft (4.267 m) diameter de Havilland Hydromatic or Rotol propellers.

Fw190A9----Three types of propeller were authorised for use on the A-9: the VDM 9-112176A wooden propeller, 3.5 m (11 ft 6 in) in diameter, was the preferred option, however, many A-9s were fitted with the standard VDM 9-12067A metal propeller and some had a VDM 9-12153A metal propeller with external, bolt on balance weights.

P47D----The P-47D-16, D-20, D-22 and D-23 were similar to the P-47D-15 with minor improvements in the fuel system, engine subsystems, a jettisonable canopy, and a bulletproof windshield. Beginning with the block 22 aircraft, the original narrow-chorded Curtiss propeller was replaced by propellers with larger blades, the Evansville plant switching to a new Curtiss propeller with a diameter of 13 ft (3.96 m) and the Long Island plant using a Hamilton Standard propeller with a diameter of 13 ft 2 in (4.01 m). With the bigger propellers having barely 6 in (152 mm) of ground clearance, Thunderbolt pilots had to learn to be careful on takeoffs to keep the tail down until they obtained adequate ground clearance, and on landings to flare the aircraft properly.

Last but not least, I believe the high-speed dive and zoom advantage of P51P47Tempest is their most important tactic in combat, and is the most amazing aspect of their flight characters.

If they can outzoom from high-speed against opponent for 300 metres higher; if they can outdive rival for more kinetic energy(sth. equals to 300 metres Potential Energy ). What will happen?

As we all known, Bf109s are very good at climbing(low speed,max climb), usually, in low-medium altitude, Bf109 has 1000ft/minute climbing advantage to their opponents.

Bf109's Energy fight: When finding enemy at rear, same energy, 700-800m away , 109 will probably climb, after 2 minutes(Be patient! Be careful about the 3rd one!), 109 will establish 600 meters higher advantage over the opponent who follows the 109. And then, 109 will fight back by using this 600 meters "extra" energy. This kind of story takes place again and again and again in most il2 servers.

P51P47Tempest could also "E-fight" in different style: diving and zooming. If a P51 find a 109 at rear, same energy, 700-800m away, P51 can dive to 650km/h IAS ( by split S), if 109 follows, he will find P51 is gaining on him, that is, P51 is quite faster than him, and the distant between them has been enlarged to 1000 m, and then, P51 will zoom at 60 degree (Be patient! Be careful about the 3rd one!), of course 109 will cut the coner, but P51 has zoom advantage so that 109 could not get close to shooting range during zooming period. Roughly P51 will find himself 600 m higher than 109, and this is the time to fight back.


1v1 is quite funny, teamwork of E-fighting will be more attractive, believe it or not. If you have some advantage, be good at using it, don't waste it, don't spoil it, be patient.

Which is already modelled including Mach effects. Like I said, some aspects are there. This is one.

IIRC, the FW-190 tested is a G series by WerkNummer.

The maximum helical tip velocity is extremely important to any propeller design. At about mach .85 most propellers will begin to dramatically decrease efficiency as the normal shock formation disrupts flow. Yes, they break the sound barrier.

You can see the effect in any fast aircraft equipped with a CSP and the ability to over speed the propeller. Climb to about 12,500 feet, preferably on a hot summer day and set the aircraft for 75% cruise. If you increase to maximum rpm and manifold pressure, you will see a drop in your airspeed.

Maybe one could simulate the effect just by decreasing propeller efficiency sharply at Mach .85.

As you stated, propellers are extremely complicated and there are lots of trade-offs in design. For example, adding blades does increase the co-efficient of power but adding blades decreases propeller efficiency. The materials one chooses also has a large effect on propeller design. Metal blades have good power absorption but are fatigue limited. The primary reason for a metal propeller is cheap production and erosion resistance. Metal propellers have excellent erosion resistance so they be flown in the rain. Wooden blades have even better power absorption and unlimited fatigue life. Wooden blades can delaminate in the rain and require some sort of protection in order not to erode. The German wooden propellers were wrapped in metal mesh, fabric covered, and covered with a thick resin.

In the event of a prop strike, metal transferred more force to the engine resulting in more damage. Wooden propellers tend to act like a circuit breaker and disintegrate transferring less force to the engine. It is cheaper to replace a propeller than an engine.

Let's discuss this record.

Jtd's explanation:
It sound reasonable, in a real world combat, the engine management can't be neglected, but this is a "test" to determine dive accelaration so P47 should prepare for diving: at first setting rich-mixture, rpm/pitch to 3000rpm, throttle to 40% so that actual engine rpm is 2000 or so(although pitch is fine), criusing side by side with fw190 @250mph IAS. Next step for P47 is just slam the throttle forward and dive.

BTW, I am doubt fw190A4 could PULL AWAY RAPIDLY from P47d at initial dive in 4.11m.

My GUESS about that historical test:

When diving from 250mph to 380 mph or so, the speed of tip of P47's airscrew firstly reached 0.8 Mach than fw190's due to its greater rotating speed. When P47's reached 0.8 Mach and suffered from obvious airscrew efficience drop while 190's remained at BELOW 0.8 Mach, 190 had more thrust and outdove P47 rapidly.

But 380mph IAS(just my estimate) is the turning point, where P47's tip breaks sound barrier, and the drag coefficient of airscrew tip DECREASES, P47's efficiency INCREASES as we known that the majority of airscrew thrust is from tip section of propeller. From 380mph to 450mph, it was 190's turn to suffer from efficiency drop due to it's 0.8-1.0 Mach tip speed, P47 began to catch up with 190, and the P47's hugh weight advantage boosted its taking over because the higher speed, the more important role of weight. Therefore P47's diving accelarartion became astonishing-------quickly catched up fw190 200yard ahead, and passed 190 with MUCH GREATER SPEED like "thunderbolt".

It's good thinking. I'll take a shot.

I think if the props on both planes are nearing 450 TAS and running inefficiently, you must fall back to the drags of the planes themselves. We know that the wing loading on p47-22 is greater than fw 190A. We also know that fw190A out turns a p47-22 based on the fan plots. So, I think we can conclude that the p47 is simple more aerodynamically streamlined for diving (less draggy) and this is why it eventually catches up and surpasses the 190A in a dive. I don't think the p47 prop all of a sudden gets more efficient when it breaks the sound barrier, but I could be wrong about that. Anyway, it is not the weight of the p47, but more so that the 190 wing simply generates more lift and that creates a drag. Yes, there is a weight difference. But if both planes were shaped as same sized spheres and one is twice as heavy as the other, I think you won't get that much separation.

Also ot, don't ever dive after a p51 in 109. Climb, pursue and hope he turns. If he is diving away from his home base, you have him. Simply cut off the angle. ;)