Why still no dive acceleration difference?

[Crumpp]

no, that is not what I'm saying. it may provide thrust. but it is not "excess" thrust. that is the key here. excess thrust, excess thrust, excess thrust. it is not excess thrust because Crumpp posted a diagram on csp propellar that shows you can not have peak efficiency beyond Vmax. The only way to get beyond vmax and create excess thrust is to dive at the necessary angle. go back and look how he defined excess thrust. it's the difference between the two force vectors. in level flight, the force vector from gravity has no forward direction. at vmax and level flight, there is no more opportunity to create excess thrust from the prop. you have to dive to create excess thrust and acceleration.

You got it!

One small tweak though....

Crumpp posted a diagram on csp propellar that shows you can not have peak efficiency beyond Vmax.

It is not that you cannot have peak efficiency beyond Vmax. You could design such a propeller but there is little point as all performance the airplane cannot sustain is instantaneous. Of course there would be some serious design trade off's to gain such performance as well. A supersonic propeller design would not work very well on a WWII Piston fighter.

http://www.aerospaceweb.org/question...s/q0031b.shtml

The CSP is designed to maintain peak efficiency through the designs sustainable envelope.

[BlackBerry]

I drew these pictures. Hope you understand my opinion about excess thrust.

When speed above Vmax, engine thrust is always smaller than air drag force.

w.jpg

q.jpg

[BlackBerry]

Originally Posted by Crumpp

You got it!

One small tweak though....



It is not that you cannot have peak efficiency beyond Vmax. You could design such a propeller but there is little point as all performance the airplane cannot sustain is instantaneous. Of course there would be some serious design trade off's to gain such performance as well. A supersonic propeller design would not work very well on a WWII Piston fighter.

http://www.aerospaceweb.org/question...s/q0031b.shtml

The CSP is designed to maintain peak efficiency through the designs sustainable envelope.

Speed in IAS.

This is my test in Il2 4.11m, Tempest cruising 250km/h @3000 m altitude, and dive to 700km/h, then I tried to maintain 700km/h by lowing my altitude in a shallow dive, after getting on deck at 700km/h, Tempest was slowed down to Vmax-600 km/h.


In this whole process, there is 70 seconds during which tempest speed is between 650km/h and 700km/h(IAS). And it took 40 seconds to slow down Tempest from 700km/h to 600km/h on the deck. Don't forget this is in low altitude where the air is thick--high density, if you dive at high altitude where air density is much less, you could hold a longer time in high speed.


If a La7 follows me from the very beginning with same energy, I can easily drag him down to his low efficciency zone----650-700 km/h IAS for 70 seconds. During this period, I could steal several hundreds of HP from him for more than 1 minutes, it's a HUGE energy loss for La7.

high speed dive.zip

[BlackBerry]

Originally Posted by Crumpp

A supersonic propeller design would not work very well on a WWII Piston fighter.

See here, 3-blade NACA16 propeller on P47D, propeller tip speed is 1.0-1.1 Mach while efficiency is still quite high.

http://digital.library.unt.edu/ark:/...adc62616/m1/7/

med_res.jpeg

here, effect of compressibility on propeller efficiency.

http://digital.library.unt.edu/ark:/...dc62616/m1/25/

[Crumpp]

When speed above Vmax, engine thrust is always smaller than air drag force.

Right...

When speed above Vmax, engine thrust is always smaller than air drag force.

Correct.

You getting lost in the trees Blackberry and cannot see the forest.

Maybe if you go back to my very first post, it will help you to gain a better understanding. You understand what is going on with the actual forces but do seem to be able to recognize it in the math.

The difference between the force on the axis of motion in the dive and the force on the axis of motion for level flight is your initial excess force that will move the aircraft to its new equilibrium point velocity. The derivative between that and equilibrium is your average excess force along that vector....

http://forum.1cpublishing.eu/showpos...3&postcount=98

At Vmax, that initial excess force is composed entirely of a component of weight.

We don't have to break anything down. The detail is already there in our calculations. To determine aceleration, we need the amount of excess force along our vector of motion. It is that excess force that causes the aceleration.

If we start our dive at a velocity below Vmax, then our initial thrust force is the difference between that specific velocity propeller thrust and zero at Vmax. Then we add the additional component of weight that shifts to thrust.

The derivative between that and equilibrium is your average excess force along that vector...

Your argument that your game would benefit from a more "detailed" propeller model such as Blade Element Theory in dive performance is not valid.

You are confusing the mathmatical process of summing the forces with what is actually going on with those forces in a moment in time.

We have already considered that moment in time when we determined our derivative.