Why still no dive acceleration difference?

[MadBlaster]

I see you were still writing.

Originally Posted by BlackBerry

The teeth had been taken by someone who, for some reason, didn't pay enough attention to high Mach number/compressibility effect which leads to efficiency decrease of a CSP.[/B]

You have to audit the numbers coming out of the sim using devicelink tool. That is the only way you could prove it. I tend to think that would be rather difficult. There's probably some stuff you need visibility on that devicelink numbers don't tell you. Maybe some randomness. For example, rudder yaw. But you have the input parameters show in this thread a few posts back, so you could do reasonableness approximation to get comfortable with it. You could build your own algorithm in C++, put in those input parameters, and run it with output to a file. then check that output to devicelink numbers from the sim. if the numbers are close, then it is accounted for. if not, then your statement could be true. otherwise, it is speculation. Crumpp says he thinks it is accounted for in standard formulation and generated some output that does not disprove his conjecture.

[BlackBerry]

Originally Posted by MadBlaster

Blackberry, it's complex calculus algorithm. But in computer, this is handled/simulated by optimizing the algorithm every few milliseconds. He already said, he doesn't have access to the flight model. What exactly to you expect him to do? His formula describe at a moment in time when forces are max. He would have to expand the formula from Tzero to Tn when terminal velocity is reached.

Really, I shouldn't talk about math or physics. I had to copy off my buddy's papers to get through high school. Just a heads up.

Accurate calculation should be performed by Computer. As il2 players, we just need to know on what speed will we dive with better acceleratin than opponents.

In the example of P47 vs Fw190G, the P47 did three steps to overtake Fw190.

1) to get better dive acceleration

And after some time,

2) to get a higher speed

And after some time,

3) to over take fw190G

Therefore, P47 acquired better dive acceleration firstly. So we can estimate roughly:

A)From 400km/h to 500km/h IAS, fw190A has better 65 degree dive acceleration.

B)from 500km/h to 750km/h and above, P47 dives faster.

It's important for P47 to keep high speed in battle field. If a fw190a rides on you at 3000m altitude, with same altitude and IAS, he is ready for shooting at you because there is 350 meters distance between you. THE SPEED OF YOU IS VERY IMPORTANT. If both of you are 500km/h, your P47d could outdive fw190a immediately in a 65degree dive, when you dive to 900m altitude, you could pull around 150m away from him, thus you are out of his shooting range(500m) when both of you begin to level fly near the sea level.

Furthermore, you may 60km/h(17m/s) faster than fw190a in the end of dive(750--800km/h), during the slow down level flight of 30 seconds, fw190a speed decreases more quickly than you, roughly you are round 1000 meters ahead of fw190a when both of you become slower than 650km/h.

I've never seen that significant dive advantage in il2, so I suspect the propeller efficiency calculating (700km/h-800km/)in il2 FM.

[MadBlaster]

Originally Posted by BlackBerry

Accurate calculation should be performed by Computer. As il2 players, we just need to know on what speed will we dive with better acceleratin than opponents.

In the example of P47 vs Fw190G, the P47 did three steps to overtake Fw190.

1) to get better dive acceleration

And after some time,

2) to get a higher speed

And after some time,

3) to over take fw190G

Therefore, P47 acquired better dive acceleration firstly. So we can estimate roughly:

A)From 400km/h to 500km/h IAS, fw190A has better 65 degree dive acceleration.

B)from 500km/h to 780km/h and above, P47 dives faster.

It's important for P47 to keep high speed in battle field. If a fw190a rides on you at 3000m altitude, with same altitude and IAS, he is ready for shooting at you because there is 350 meters distance between you. THE SPEED OF YOU IS VERY IMPORTANT. If both of you are 500km/h, your P47d could outdive fw190a immediately in a 65degree dive, when you dive to 900m altitude, you could pull around 200m away from him, thus you are out of his shooting range(550m) when both of you begin to level fly near the sea level.

Furthermore, you may 60km/h(17m/s) faster than fw190a in the end of dive, during the slow down level flight of 30 seconds, fw190a speed decreases more quickly than you, roughly you are round 1000meters ahead of fw190a when both of you reach Vmax.

I've never seen that significant dive advantage in il2, so I suspect the propeller efficiency calculating in il2 FM.

I just got a flashback of chasing p47 in a steep dive in 109 g-10. I got some light hits with machine gun and he was getting away, then he pulled hard g and the wings flew off. No EAD, but it was pretty funny. All he had to do was fly straight.

[BlackBerry]

You know the 4.11m simulates the G effect on airplane structure, if you pull your stick too hard at high speed, you may lose your wings or get damaged.

I think the 4.11m is lack of pilots strength simulation. Before 4.11m, we had a "super" airplane structure and "super man" pilot with great strength.

"super" plus "super" is "ordinary" result: aircraft is quite firm at high speed maneuver.

However, in 4.11m, we have a "ordinary" plane structure and "super" pilot.

"ordinary" plus "super" is "oddness": aircrafts are too fragile. At high speed, the stick should be very heavy, so heavy that a pilot could not pull out 8-11g even with his full strength. So we need "ordinary" plane structure and "ordinary" pilots, the result should be "ordinary": aircrafts are not so fragile at high speed.

[Aviar]

Originally Posted by BlackBerry

"ordinary" plus "super" is "oddness": aircrafts are too fragile. At high speed, the stick should be very heavy, so heavy that a pilot could not pull out 8-11g even with his full strength. So we need "ordinary" plane structure and "ordinary" pilots, the result should be "ordinary": aircrafts are not so fragile at high speed.

Interesting. Do you think this could be achieved through software alone?

Aviar

[Crumpp]

However, that is "terminal speed difference", not dive acceleration difference.

I don't think I was clear.

The aerodynamic forces will tell you the FW-190A can outdive the P47. Just look at the sea level speeds and power required. At sea level, EAS = TAS and EAS is the speed the airplane always feels.

The P47 generates ~272 THP more than the FW-190A8 to travel ~20mph slower. It takes a lot of power to push that big heavy P47 through the air.

However, the relationship of thrust and drag is not the primary limiting factor in a dive for these airplanes. Dynamic pressure limits and mach limits tend to set the speed limits in WWII fighters.

The FW-190 has a higher terminal velocity than the P47. It developes almost as much power but has lower drag production.

Niether aircraft though is limited by the relationship of thrust and drag. Dynamic pressure limits and mach limits set the boundary.

In the example of P47 vs Fw190G, the P47 did three steps to overtake Fw190.

1) to get better dive acceleration

And after some time,

2) to get a higher speed

And after some time,

3) to over take fw190G

This is not necessarily due to any aerodynamic limitations, Blackberry. There were human being operating these airplanes for the test in question.

Some operational realities of these two aircraft:

1. The FW-190 pilot closes the cooling gills, which are closed anyway for level flight, ensures the propeller is in automatic, which it is for normal operation unless the KG is operating in emergency mode, pushes the nose forward and dives. His engine is automatic and adjust's as required for actual conditions under air load. The supercharger system responds instantly to power changes. In short, he pushes the stick forward and goes....

2. The P47 pilot does not have a automatic system. He has to trim the aircraft tail heavy, reduce his manifold pressure, reduce rpm to 2600, close cowl flaps, and then dive. He has a throttle he must baby because of the turbocharger. A turbocharger does not respond instantly to power changes and the P47 is much more restricted in its use. Reducing it too fast and he can lose pressure in the system which will take him ~30 seconds of level flight to get back. He cannot dive until he reduces it. In short, he cannot just push the stick forward and go......

[BlackBerry]

The FW-190 has a higher terminal velocity than the P47. It developes almost as much power but has lower drag production.

Niether aircraft though is limited by the relationship of thrust and drag. Dynamic pressure limits and mach limits set the boundary.

Ternimal velocity (speed of equilibium piont)depends on many factors.

A: fw190a8 with full oil tank and ammo, 4 tons weight
B: fw190a8 almost out of oil and ammo, 3.5 tons weight.

Max level flight at sea level: A=B
Dive in 45 degree: A>B

The heavier of aircraft, the more benefit in dive. in a 0 degree "dive", that's level flght, fw190a8 has more terminal speed than p47d, eg, 580km/h vs 560km/h. In a 45 degree dives, obviously P47 has more.

Some operational realities of these two aircraft:

1. The FW-190 pilot closes the cooling gills, which are closed anyway for level flight, ensures the propeller is in automatic, which it is for normal operation unless the KG is operating in emergency mode, pushes the nose forward and dives. His engine is automatic and adjust's as required for actual conditions under air load. The supercharger system responds instantly to power changes. In short, he pushes the stick forward and goes....

2. The P47 pilot does not have a automatic system. He has to trim the aircraft tail heavy, reduce his manifold pressure, reduce rpm to 2600, close cowl flaps, and then dive. He has a throttle he must baby because of the turbocharger. A turbocharger does not respond instantly to power changes and the P47 is much more restricted in its use. Reducing it too fast and he can lose pressure in the system which will take him ~30 seconds of level flight to get back. He cannot dive until he reduces it. In short, he cannot just push the stick forward and go.....

.

Perhaps you are right about the operational difference between P47 and Fw190 in summer 1943. Perhaps the fw190 pilot was waiting for p47 until p47's pilot finished his preparation before dive. Don't forget that was a "test", not a real "combat". Btw, there is evidence that p47 propeller has more efficiency at 2600rpm than 2800rpm in a high speed dive. Does P47 need to reduce manifold before dive?

Anyway, for some reasons, P47 was outdived by fw190G initially. P47 was slower and behind of fw190 after a short time of 65 degree dive. In order to over take fw190 in later dive stage, P47 need to get higher acceleration at first, that is the proof of P47 has better dive acceleration WITHIN fw190's allowable dive limits----466mph.

[Crumpp]

The heavier of aircraft, the more benefit in dive.

True but the power required is cubed...

Sorry Blackberry but the even the P47 does not generate enough power to overcome the lower power required advantage.

Do the math and you will see.

[Crumpp]

Does P47 need to reduce manifold before dive?

Yes, if he does not the airload will increase his manifold pressure and the waste gate will open to depressurize the system.

You understand the turbocharger requireds very gentle throttle movements. If you reduce power too fast, you can depressurize the system and you basically have a very poorly normally aspirated engine for the next 30 seconds until the turbine spools back up to repressurize the system.

[RegRag1977]

Since this interesting topic is about propeller types and dive efficiency, i just wanted to ask if, for instance, the fact that the Spit switched from three to four blades prop did allow it to improve its dive performance and to reach better dive speeds than the 109 which kept its 3 blades prop through the entire war period, as we know. Since both designs are very similar in the concept i'm sure the use of a different propeller would show in terms of DIVE performance?

I would like to see the relative dive performance of the aircraft between 109, Spit MkV and later MkIX. I think it could help answering the question we are asking ourselves? If someone knows about this it would be very nice!

PS My prejudice so far is that the 109 always dove better than the Spit (three or four blades propeller) Please correct me if i'm wrong