Why still no dive acceleration difference?

[BlackBerry]

Originally Posted by fruitbat

Blackberry, the reason i posted the charts i did, is because the weights you are using appear to be off.

empty is 3050, max load is 4272 for a standard A8, it also lists the HP as 1700.

how you want to interpret that is up to you.

See my edited post. Fw190A8 is Notleistung emergency boost system which produce 1953HP, I use 1980HP in calculation. There is some exhaust boost(bigger than 27HP at high speed). 578km/h, I use 580km/h.

So fw190a8 drag coefficient is no less than 0.2790

Ok, let's be more accurate with 4272kg

when dive in 45 degree, let the new equilirium speed as V:

new engine thrust should be 7231*(161/V)

m*g* sin(45)+t=d*V^2

4272*9.8*0.707+7231*(161/V)=0.2790*V^2

thus

v^3-106090V-4172728=0

Finally, we get V=344m/s=1238km/h. roughly euqal to 1232.6km of 6-ton P47D.

1)There should be 100HP+ exhaust boost for fw190A8@580km/h@SL, so darg efficienct should be more than 0.2790.

2) max load is 4272kg for a standard A8, max load is 8000kg for a standard P47D, even with 7-ton weight, P47D could also has higher equilirium speed.

[BlackBerry]

Oh, you might want to rethink your view on HP at atlitude,

I just compare P47D and fw190A8 at sea level.

If we compare the data at 7000m altitude, P47D has more advantage because fw190a8 lose a lot of engine output there while P47D is still 2000-2300HP.

Furthermore, the air density is only 1/2-1/3 of sea level, and aircrafts should maintain a longer time at high speed above Vmax. It's more easy to dive to a high Mach number where the 4-blade propeller has efficiency advantage.

BTW, german broad chord 3-blade propeller loses 8% efficiency at Vmax compared with old 3-blade. Therefore, allied 4-blade prop should has more efficiency than german new wide blades. not 80% vs 80%, that's sth. 85% vs 75% at Vmax.

From the A-8 on, Fw 190s could be fitted with a new paddle-bladed wooden propeller, easily identified by its wide blades with curved tips.

To sum up, at 7000m, a high speed diving P47D is more dreadful than at sea level.

[Crumpp]

So, the aircraft weight plays a important role in a 45 degree dive.

Yes it does as does the lower drag of the FW-190.

If you use Take Off Weights, the equilibrium speed of the FW-190 is higher than the P47.

It does not matter though as neither aircraft can achieve equilibrium velocity as they are dynamic pressure and mach limited.

The P47 always has higher limits.

Blackberry, the reason i posted the charts i did, is because the weights you are using appear to be off.

Yes his weights are off and it makes a big difference. Thanks for catching that.

but your not going to be diving much at sea level me thinks!

No but don't think of it as sea level. It is EAS when we use sea level performance. Adjust it for density effects and it becomes actual performance.

As such it is good approximation of Indicated Airspeeds and delivers a very good prediction of the performance trends you should see.

[Crumpp]

HP as 1700.

At SL @1.42ata@2700U/min with allowance for dynamic pressure gains at equivilent airspeeds.

The 2300 hp for the R-2800 is at War Emergency Power and the 1980 hp for the BMW801D2 is at Erhohte Notleistung 1.58ata@2700U/min.

[Crumpp]

If we use a 7-ton P47D, again, P47 has more equilibrium speed.

You will not be comparing fighters....

You guys need a weight and balance chart for the P47 series?

[fruitbat]

Originally Posted by Crumpp

You guys need a weight and balance chart for the P47 series?

I'd be very interested in seeing one thanks

for the FW to clarify, is it 1,980 PS or 1,980hp?

this has turned into a very interesting thread imo.

[Crumpp]

1,980 PS

That is Horsepower.



BTW at the velocity we are talking about, the conversion form PS to HP is really irrelevant.