quote:

Originally posted by AndyJWest:
I've done a little testing on the effect of weight on max airspeed in IL-2, and as the theory says it should, you only get a noticeable effect at high altitude. I don't have the figures to hand, but it is simple enough to reproduce.

Does anyone know the correct technique for measuring roll rate, though? As has been said, this should change with ammo load in a P-47, but I'm not sure how you would measure it.

Use sustained climb at 400+ IAS (parasitic drag using up much engine power, less weight difference should show more?)
and two separate runs to have the same basic amount of fuel each time. We know that fuel used does lighten the planes
in IL2.

I kept this in mind when i flew a P-47 last, and there is no obvious difference in rate of roll between empty, default or extra ammo load outs.

I didn't have a stop watch but i used a more informal method of recording tracks and relying on the clock timer in the ntrk. I performed rolls at 2000-3000ft at 200-250IAS, with and with out rudder. It ranged between 4-5 seconds to do one complete roll.

As for climb the only noticeable difference was above 5000m. I didn't do any comparisons but using a default load out, i noticed it zoomed upward much more quickly when i threw it into WEP. Something to consider when "weighing" your options.



ahhh puns.



Bill

quote:

Originally posted by na85:
Easy way to test:

Set unlimited fuel, but limited ammo. Go into QMB, see how fast you can get the 47 to go in level flight.

Then shoot all your ammo, and see how fast you can get it to go in level flight. If it's faster after shooting your ammo, it is lighter.

Let us know what you find out.

No offense, but that is not a very good benchmark for measuring the weight of the aircraft after expending ammunition. It would probably be more noticable to gauge the up-trim behaviour of the aircraft in level flight at a consistent speed and throttle/prop/mixture settings. Either way, however, the benefits of the lack of weight from expended ammo are minimal at best, and is pretty much just academic.

The weight is significant and easy to calculate.

The weight is about 200kg, which in a plane with a takeoff weight of 6 tonns, really isn't that significant, especially given that it more than doubles your fire time.

quote:

Originally posted by na85:
Set unlimited fuel, but limited ammo.

I should have caught that trick first time around! Very neat!

What will a 4% change in weight do to the performance of my airplane?

V2 = V1 * SQRT W2/W1 = 95 mph EAS = 83KEAS* SQRT 10000/9600 = 83 (1.04) = 85 KEAS = 98 mph EAS

Positive Limit:
LLF2/LLF1 = W1/W2
LLF2/6G = 10,000lbs/9,600lbs
LLF2 = 6 * 10,000/9,600
LLF2 = 6.25G

Negative limit
LLF2/LLF1 = W1/W2
LLF2/3G = 10,000lbs/12,000lbs
LLF2 = 3 * 10,000/9,600
LLF2 = - 3.125G


In parametric study of zoom climb from 250 KEAS to stall speed our airplane at 10,000lbs can zoom to 5606ft.

At 9,600lbs our airplane reaches a zoom height of 5960 ft or a gain of 354 ft.

Our climb performance is reduced as well when we add weight.

ROC = 33,000 (1955lbs –525lbs) / 10,000lbs = 4719fpm

ROC = 33,000 (1955lbs –525lbs) / 9600lbs = 4915fpm

In fact the entire envelope is shrunk when we add weight to an airplane.

Learning to do the math will help to eliminate much of the idle speculation and guesswork. Of course you still have to contend with those who will go to great lengths like re-inventing EAS to prove any point for their team.

All the best,

Crumpp

quote:

Originally posted by BillSwagger:
Historical load outs were somewhere between 300 and 400 rpg depending on the ordinance.
I'm not sure why 200rpg is the default, as that usually represents a very heavy load, ie rockets/bombs and a drop tank.

AF documents say 267 standard, 425 max. This applies for both 6 and 8 guns. Now the funny thing is that 6*267 = 8*200 = 1600; maybe the folks at 1C thought that 1600 rounds were standard outfit no matter how many guns installed.

Did you know that the ammo and fuel aboard a P-47 weighs as much as a whole Ki-27 fighter plane (roughly 1.5 t)?

quote:

Originally posted by JtD:
Did you know that the ammo and fuel aboard a P-47 weighs as much as a whole Ki-27 fighter plane (roughly 1.5 t)?

While observed in the wild, the P-47 feeds on many small planes including 109s.

quote:

Originally posted by BillSwagger:

quote:

Originally posted by JtD:
Did you know that the ammo and fuel aboard a P-47 weighs as much as a whole Ki-27 fighter plane (roughly 1.5 t)?

While observed in the wild, the P-47 feeds on many small planes including 109s.