My problem with this is that there were some other changes between the B-2 and the B-10. Some were subtle and some not so subtle but somehow the change in the wing gets all the credit (blame).
Changes between the B-10 to the B-25B-2 include:
Larger cowling intakes for new engines*
Four added .50 cal machine guns- two added .50 cal to fuselage side hatches, one .50 cal added to nose, two package .50 cal added*.
Ventral .50 cal machine gun removed
Various internal mods
- automatic life raft ejector
- Day and night drift signals (?)
- Inclinometer
- Astrocompass
- Astrograph
- New Starter
- Winterization equipment (?)
- Lengthened nose wheel strut
- Mechanically operated gear doors (?)
Slotted flaps
Rudder/vertical stabilizer increase*
* Changes that affect aerodynamic performance not including wing span increase . It is my opinion that all these changes put together would have an almost imperceptible impact to the overall form drag of the B-26.
Wing span extension from 65 to 71 feet,
Empty weight increased from 22,380 lbs to 24,000 lbs, or 1600 lbs. I would guess that the non-wing extension weight increases as between 200-300 lbs (the entire tail structure of the P-47 was 250lbs) which would make the wing extension 1300-1400 lbs.
There were a bunch of changes between the B-26/A and the B-26B-2 that also cost speed.
engine on a B-26A
I was not interested in the B-26A, I was interested in two aircraft configurations that were close but with different wings in order to isolate the performance degradation of the wing extension alone. The B-26B-2, represented all the configurations prior, and the B-26B-10, which is basically the base for follow on models. And, I had flight test results of these two aircraft.
The Spinners went away on the very early Bs. The oil cooler inlets got bigger, On the B-3s the air intakes got much bigger in order to accommodate sand filters. Now if the four package guns cost 3-5mph (or 3% of range, sources differ) what did all the changes to the engine installation cost?
Neither the B-26B-2 nor the -10 tested had spinners. Also, apparently the -10 only had two package guns, per Mendenhall's Deadly Duo.
Please notice that the vertical stabilizer and rudder grew about 1ft 6in from the small wing to the big wing.
I haven't seen what this cost in speed and it may be lumped in the cost of the big wing.
It is said that the larger fin and rudder were needed to stabilize the bigger wing but I am at least somewhat sure that having a bigger fin and rudder helped in an engine out situation.
At some point the horizontal stabilizer and elevators got bigger too, but I don't know when.
Don't know much about this. I think the added size of the vertical stabilizer, or the package guns, would be very small relative to the form drag of a pretty large bomber.
A problem with a B-26 doing a 300 mile deep penetration strike (or even a 150 mile radius in enemy territory) is the amount of fuel required. A B-26 used 350-400 gallons an hour at max continuous depending altitude/supercharger gear and so on. Backing down to 75% power gets you (at least on the very early B-26) a cruise of just under 280mph at 8,000ft while burning around 270-290 gallons an hour. IF for instance you drop bombs at 250 miles from base and you figure 150 miles of that is enemy territory then you need about 200 gallon at bombs gone (cruise can be dropped to around 200mph and a fuel burn of close to 100gph once in friendly territory) and this means entering enemy territory with at least 350 gallons in the tanks. Now please note this takes into account NO deviations in flight path (even a several mile turn around at the target), NO reserves , Runway is lined up with the target and NO use of power above 75% even for 1 minute.
I don't really want to dig into this and, knowing you, I doubt if I could identify an error. However, the salient point is that the B-26B-2 has a lower drag value than the B-26B-10. Therefore, for any given mission, the B-26B-2, vs. the -10, could fly at the same speed with less power therefore use less fuel, therefore more bombload? Or could fly the same mission with the same power setting and fly faster. And since it will fly the mission faster at the same power level, it would use less fuel, therefore more bombload?
Test at approx.
5k ft.
B-26B-2, AC 41-17756,
airspeed 281 mph,
1400 hp/eng,, test weight
29,860 lbs
B-26B-10, AC 41-18199, airspeed
250 mph,
1400 hp/engine est. (247mph/1325hp), wt
30,780 lbs
Notes: Since the added wing span is most likely over 1,000 lbs, the two test weights should represent identical load carry capacity.
Miscellaneous issues mentioned above, and a few others including cowl flaps have an impact on these test. Including these, I estimated the difference in airspeed at 5000 ft, 1400 hp power setting and equivalent weight to be
reduced from 31 mph to 20 mph.
If any modification, e.g. electro-hydraulic tail gun, to the -10 that led to later configurations up to B-25C were applied to the -2 configuration, i.e. short wing, the results would be the same in that the -2 configuration would be faster at the same power levels just because it was just cleaner.
