So, for the loadout in question (40x 500lbs, 20,000 lbs total) taking an overload of fuel nearly doubles the time to climb to 25k (a reasonable, average alt). You were right that my theory of diminishing returns wasn't accurate, but the extra time duration doesn't help if it takes you almost an hour (~55min) to get to 25k, when going to 50% takes 35 minutes for the same alt.
(...)
Even if you absolutely wanted to loiter around after your bombs were gone, 75% would be the max you should ever take with those 40x 500lb loads.
Of course % is much lighter and thus faster at alt no doubt. And I'm surely not advocating taking max fuel and I'm not even advocating max bombload all the time (depending on target the other loadouts can be more effective). In fact, 40x500 is a rare choice for me only used in special cases.
However, there
are times, when it is all about the range. Sometimes the target (I'm thinking almost exclusively of the strats) is very far away so that 50% will be way too little to reach it. Even 75% can be very tight of a budget if you are making many passes over the strats, as the 56x250, 80x100 (city busting loadouts) or 40x500 do require. Unless you are not going for precision and just carpted everything, possibly even with .salvo. I never do that, if I'm going on a such long ride I want to make every bomb count as much as possible. A regular city busting attack requires 4-6 passes over the strats. And turning around an recalibrating takes a lot of time in the Superfortress.
For the record, this is not only a result of academical tests, but also of 186 B-29 missions I have flown since 9-1-2012, with more of 90% of them being strat runs. And I kept very detailed logs on all of them, including loadout, fuel, altitude and mission duration. So I gathered enough data to see how long my missions really were, and how much time I had to spend over my targets and what kind of problems I was running into.
So for the average strat run, my fuel loadout is 75% for the 20x500, 12x1k, 2x8k or 4x4k bomb load... I often
could do with 50%, but there ain't much of a margin if you run in trouble (for example a fuel leak, or a persistent long range fighter who's only waiting to vulch you while landing). When I go city busting, with 80x100 or 56x250 (preferred), I take 100% fuel, as this mission can easily reach 2.5 hours for me (depending on distance to the strats and fighter defense).
My longest mission ever took me 2 hours and 50 minutes, attacking retreated strats with 12x1k.
For informational purposes: These are the bomb/fuel combinations and resulting takeoff weights of all but the last of my B-29 missions:
Note that unlike many others, I almost never fly at altitudes above 30k, in fact 30K is usually the altitude I do fly in Komet Kountry only. My average B-29 in all of these sorties was 28K.
And the resume of all that?
Plan your mission. Know what you are going to hit. Select the best, and necessarily not the biggest load of bombs. Plan your route (use the charts above for optimum climbout phase) and flight level and select the
appropriate fuel percentage. Drain the center fuel first, 'cause that's the one most likely to get hit by the puffy ack.
