Thank you for the engine chart.
as for the accuracy of the weights?
See;
http://zenoswarbirdvideos.com/Images/P-39/P39TOCLC.pdf
for a chart on the P-39Q-1 that gives weights of 8100lbs, 7600lbs and 7200lbs.
8100lbs is correct (or close enough) for carrying either a 500lb bomb or 75 gallon drop tank, 7600lbs is close (30lbs over) for the plane clean, with ammo and 87 gallons of fuel.
7200lbs means either no ammo of any caliber (and no ballast) or only 20 gallons of fuel left in the tanks (or combination).
This last combination, while interesting to the pilot and "accurate" tells the pilot how long a runway he needs in such a condition or the difference in climb or some differences in other performance as the plane gets lighter. performance can be estimated depending on actual weight when it differs from the weights given in the table ((falls between).
Picking the lightest weight on the chart may mean a less than "combat" ready condition even if the plane will fly perfectly well in that condition/at that weight.
The weight "selection" is not consistent on the charts. P-40 chart/s is/are like the P-39 chart. the lightest weight given means there is something not in the airplane. The one for the P-40E lists one weight of 7500lbs, once you stick your 180lb pilot and 75-97lbs of oil into a 7665lb basic weight airplane you have 580lbs left for fuel and ammo (and a P-40E will hold 423lbs of ammo)
However the P-38L chart starts at 17,400lbs. I don't have the weight charts for the P-38L but for the J 17,400lbs covers the plane with
full ammo (500rounds per .50 cal gun) and and nearly full tanks, including leading edge. (17,699lbs) using just 300 gallons of fuel and full ammo drops the weight to 17,009lbs. P-38s often carried 300 rounds per .50 cal gun and the weight savings was 240-250lbs.
The P-38L may well be several hundred pounds heavier than the J and I have no explanation as to why the lightest weight listed for the P-38L is for a more fully supplied plane (even if not max clean weight) than the lightest weight plane on the other two charts.
granted an F-8 Mosquito doesn't have to worry about ammo but
if the plane weighs 21,000lbs max with 887 US gallons of fuel (carried by whatever means needed) then to get down to the 16,770lb figure you have to lose 4230lb of fuel or equipment (or crew?) as there is no ammo or guns. If you lose 4230lbs of fuel that is 705 US gallons and comparing a Mosquito with 182 gallons of fuel to a P-38 with even 300 gallons is a bit of a bogus comparison.
I would imagine (but could very well be wrong) that the F-8 would use the bottom line on the engine chart for a "ferry" climb. This chart doesn't say but 2650rpm and 4lbs boost was the common limit for two speed Merlins when running lean.
So for the "ferry" climb we have the P-38 using engines that are 3.6% larger but turning only 87% as fast(rpm) and operating at 92% of the manifold pressure. Not exactly a surprise that a
lightweight Mosquito can climb well in comparison.
I admit I have made a few assumptions here, we don't have the actual numbers to back either of us up. I am not claiming that I am right or that you are wrong, only that there seem to be a range of possible answers (weights and power levels) that can skew the results if not looked at in a critical manor.
Pilots notes/manuals are great and I am not saying that the numbers are wrong (at least not in the sense that you exceed limits, either high or low, you won't be in trouble) but sometimes the weights used seem out of touch with the intended use of the plane. although knowing that even running with no ammo and little fuel trying to put a P-39 down on a wet jungle airfield is going to need a lot more runway than even a warm summer day on dry concrete
May help with the planning of auxiliary or emergency airstrips too. How long a runway do you need to get a repaired airplane running light off the ground to 'ferry' it to the main field only 10-30 miles away?