From a letter - Peyton Magruder to Bernard Mallon, February 23, 1964:
While we submitted proposals for all three engines (WAC 3350, WAC 2600, P &
W 2800) ... I personally had chosen the 2800 single stage, single speed
engine with turbo supercharger for the basic B-26 design and designed the
entire aircraft, particularly the wing, for this engine combination although
provisions were made to substitute the larger WAC 3350 if and when this
became desirable. The different engine combinations ... gave high speeds at
critical altitude ranging from 317 mph to 414 mph. With the combination I
wanted (E-& W 2800 turbo) the high speed was 392mph. The particular wing
section chosen as well as the other aerodynamic features were largely based
on this top speed and on the power characteristics of this particular engine
There is little question but that the original and first B-26 flown, before
it became butchered later by the necessities of combat production, was the
cleanest production airplane which had ever been built up to that time-and
as a matter of fact, even for the next 6 or 8 years. You might say then that
the basic design criteria for this airplane was: speed, first; bomb load,
second; and production design, third.
The original engine combination chosen lasted about two months and before we
were well under way in the detail design we had to drop the turbo because it
was found impossible to produce them in time to meet our delivery schedule.
Turbos which had been designed for the B-17 were suitable only for a much
smaller engine and GE simply could not produce one suitable for the B-26 in
time for us to proceed with this design.
Later, of course such a turbo did come out and was used quite successfully
on the P-47, which as you know was one of the war's greatest fighters, which
utilized the 2800 single-stage, single-speed engine for its power plant.
Upon losing the turbo feature, the next best bet was the two-stage,
two-speed which would still give us a top speed of 368 mph but within a few
weeks it was established that this engine could not be produced in time so
we finally went with the single-stage two speed version of the 2800 and our
resulting high speed dropped to 324 mph, thus we had lost about 70 mph as
opposed to the turbo design with the 2800 engine and 90 mph as compared to
the 3350 engine with turbo yet the entire design philosophy which had
dictated the wing section, area, wing loading etc., had been based upon a
top speed of about 400 mph.
There was no time to completely redesign everything to take into account the
lower top speed. We were going to have to be satisfied with it. Actually we
should have immediately increased the wing area by primarily increasing the
wing span and in addition should not have used the symmetrical airfoil for
the wing, but another one which would have had slightly higher lift
characteristics throughout the speed range.
The reason why these changes should have been made is that we should have
anticipated the fact that the airplane's gross weight would inevitably grow.
While we had set the original gross weight at 26,500 lbs. (first plane gross
27,000 lbs.) we had taken into account a growth to about 32,000 lbs., but we
certainly never conceived of the original B-26 being forced to fly in the
40-42,000 lbs. weight range as it did towards the end of the war.
Editor: With P-47 engines, as originally intended, nothing would have caught