I matched duration and looked at speeds, which then gives range. The only reason I did it this way, though, is that it would take a long time to figure out best settings to get maximum range in AH (as you have to wait for speed to get to steady state after any engine adjustment to be able to figure out range). Max cruise is not really max range in AH, and max cruise for one plane might be closer to the true optimum range than max cruise for another plane. For example, max cruise settings for the P-47N had the plane flying at stall speed with full external fuel and at a speed where the autopilot could not maintain altitude. So, I couldn't compare both set at their max cruise settings. What then to pick? I decided to use the P-51D's max cruise settings (as it could fly just fine at those settings), noted speed, duration, and range; then I set the P-47N to have the same duration, and noted speed and range. Or I could have set the P-47N to have the same speed and noted duration and range; but matching speeds takes a long time of fiddling, whereas matching duration is very easy with just a quick RPM adjustment.
You're partially correct. It was interesting for me to note last night that, when using the power/rpm settings in the P-47N POH, I couldn't hold altitude at 5000 feet. That's something I'm going to look into later as the POH says you should be able to hold altitude at that loading with 1900RPM and 33.5" MP. But, I did manage around 190 TAS on 2100 RPM, and 35" of MP, which gave me a fuel burn of about 115 gph. Once the belly tank was off, I was able to maintain altitude on 1900 RPM and 34" of MP, which dropped the fuel burn to right around 100 gph. Once the wing tanks were off, I was able to maintain altitude on 1700 RPM and 31" of MP, which dropped the fuel burn down to around 80 or so GPH. So, flying around 190-200 mph TAS, you can easily make in excess of 2000 miles for the P-47N in game. I'll do some more testing to see if I can come up with some hard numbers.
But, duration changes as the weight of fuel, and drag of tanks is removed, if flying at a constant speed, since lower power settings are available at the lower weights/drag. So, theoretically, the duration number would continue to stretch out until you ultimately ran out of fuel. According to the POH, the 2X165 and 1X110 external tanks (440 total gallons) were capable of taking you 900 miles, but almost the same amount of internal fuel could take you 1400 on the trip back.
So, merely looking at the duration shown on the E6B at the start of the flight won't give you an accurate representation of the true max range.
