Hi Renrich,
>For instance it's speed and range figures as well load carrying.
Here is the Ju 87B manual:
http://www.ww2aircraft.net/forum/other-mechanical-systems-tech/ju-87b-pilots-manual-5085.html
It does not have top speed or range figures, but at least lists a true air speed in the cruise of circa 350 km/h @ 5.2 km at maximum continuous power, and a more economical 325 km/h @ 4.0 km for a range of 505 km in supercharger low gear. (This is not best range, which would be achieved at a considerably lower power setting. It's not "theoretical still air range" either, as some deductions have already been made from the figure compared to the theoretical figure you'd derive from true airspeed, fuel supply and fuel consumption.)
For the Ju 87D that was the contemporary of the SBD-3 and -5, I only have the loading diagram from the manual, so I'm afraid I don't have performance figures.
However, you can see the load cases 13 and 14 in the diagram: Two external tanks in combination with a 250 kg or a 500 kg bomb. Load case 15 actually is a 1000 kg bomb in combination with the two tanks, but it's marked as "take-off with overload - only by special RLM operations order", so it's not a standard configuration.
In short, I see little reason to doubt the load carrying figures and the typically quoted top speeds for the Ju 87. Range, as always, is difficult to determine from incomplete data, but with the external tanks, it would probably have had the range for carrier operations in the Pacific theatre, even if other dive bombers still would hold a range advantage over the Stuka.
>What I was referring to on external fuel is that I believe the rule of thumb in WW2 was that half the fuel in an external tank was used for overcoming the additional drag and the other half went to extend the range.
Hm, interesting rule of thumb, I hadn't heard this one before. Seems a bit pessimistic to me, though ... are you sure it's not actually a Vietnam era rule? For high-speed jets, it would make more sense in my opinion.
Looking at WW2 aircraft, the Me 109G-6's top speed at sea level for example dropped by 8% when a 300 L drop tank was carried, while the fuel load increased by 75% ... more like 10% of the additional fuel burnt to carry the drop tank.
Kurfrst - Leistungzusammenstellung Me 109 G.
And remember "speed cubed" ... if you fly as slow as the dive bombers, the additional drag pretty much collapses into irrelevance. If the Me 109G-6 travels at 1/2 its top speed, the drop tank drag penalty is only 1/(2^3) = 1/8 of the high speed value. That's very roughly 1% of the unencumbered speed ... not a concern at all.
Regards,
Henning (HoHun)