P-47D Level Speed

[HR_Zunzun]

2 hours ago, Fumes said:

Again, as you agreed earlier, you can find that this does hold water simply by looking at many other aircraft...identical aircraft...compared at difference weights. Many climb rate charts even have performance at different weights....

 

 

That being said, given the significantly more massive difference in performance change....this comparison is close enough. Especially since the overwhelmingly dominant factor in climb performance is thrust to weight.

 

 

 

 

 

 

 

 

 

 

 

As can be seen here a 24% percent difference in power to weight yields a 29% difference in climb approximate. A significantly smaller change per percent than what we see in il2.

 

As I also recalled, my comment was directed to comparing apples to apples and not oranges. That new example proves your point better.

[Talon_]

6 hours ago, Fumes said:

Especially since the overwhelmingly dominant factor in climb performance is thrust to weight.

 

Spitfire gains 15% power at +25lbs over +18lbs and initial climb goes up by (rough estimate) 40%

[JtD]

Change in weight or power does not directly correlate to change in climb rate. This is very evident if you look at borderline performance, i.e. zero climb rate at a specific weight and power. If you reduce weight or increase power here, you'll get an infinite increase in climb rate.

 

Point is, the extra climb rate at a reduced weight comes out of the reduction of lift induced drag in addition to the linear relationship of power/weight. Lift induced drag is roughly half the total drag, where total drag is engine power times prop efficiency minus climb rate times g times mass of the aircraft. If you run the numbers for an aircraft at 6t weight with 15m/s climb rate at 1800kW power and 0.85 prop efficiency, you'll find that roughly 630kW go into drag. 315kW would be induced. Lowering weight to 5t would lower lift induced drag to about 220kW, clearing roughly an extra 100kW for more climb rate. Gives you a climb rate of 20m/s at 5t - 30% extra at 17% less weight. (Or 25% less at 20% more weight, looking at it the other way round).

 

An estimate like this is the minimum you need to do, comparing performance to other aircraft at other weights is pretty meaningless. However, I do agree that the in game test results shown are extreme.

[-=PHX=-SuperEtendard]

Thanks JtD, so for the particular case in game (6250 Kg at 18.7 m/s down to 5500 Kg at 2600 HP) what should be the estimated improvement? 2 or 3 m/s improvement instead of 4 ?

Edited February 4, 2019 by -=PHX=-SuperEtendard

[JtD]

Following the guesstimate you'd end up at around 3.5m/s.