Army Air Corps issues Specification C-213
of the B-26 proceeded parallel to the North American
B-25 Mitchell both types being designed to a specification
for a five-place bombardment aircraft issued 25th January
1939 by the Army Air Corps. Specification C-213 outlined
the requirement for a "twin engine
medium bombardment airplane." Details
of C-213 were given in Circular Proposal
39-640 on 11 March, 1939. It required an
operating speed of not less than 250 mph,
a top speed of at least 300 mph, a 1,800
mile range with a crew of five, and a service
ceiling of no less than 25,000 feet. Specified
as well was a bomb load of either four 1,000-pound
bombs, two 2,000-pound bombs, six 600-pounders,
twelve 300-pounders, or thirty 100-pounders.
aircraft was to have the load-carrying capacity
of a bomber and the speed plus maneuverability
of a fighter. It was to have twin engines
and a tricycle landing gear.
to the urgency in procuring a suitable aircraft,
for the first time, the Air Corps stated
that a prototype need not be built and tested.
The winning design would be contracted for
and manufacturing started right off the
drawing board. The first unit would be a
production version and the rest were to
roll off the assembly line henceforth.
Bid Selection is made by the Army Air Corps
bids were submitted by four manufacturers
with each firm providing up to 15 design
variations. The four contenders were: The
Glenn L. Martin Co., North American Aviation,
Inc., Douglas Aircraft Co., and the Stearman
Aircraft Division of the Boeing Airplane
Co.. Brg. Gen. Jacob E. Fickel headed the
C-213 Evaluation Board for the Air Corps.
point-rating system of pertinent factors
was the "Method of Evaluation"
as outlined by Circular Proposal 39-640.
Evaluation of the best designs from the
four different companies was performed and
the Martin Model 179 Bid No. 6 was the champion
by a wide margin beating out the North American
P-442-D4, Douglas' B-23, and the Stearman
Glenn L. Martin Company had
a long and distinguished record
of building quality bombardment
factors explained why the Martin design
promised performance with a guarantee
of a top speed of 322 mph, a 266 mph
cruising speed, and a 1,800 mile range.
"reduced to practice" engineering
& production details.
Martin Company's long track record in
that it could deliver the 1st article
in 9 months and 204 aircraft in 23 months
- and the Board's belief that it could
winning bid specified that the propellers
were to be the newest four-bladed 13 ft.
6 in. Curtiss Electrics powered by
the Pratt & Whitney R-2800 engine. The
R-2800 "Double Wasp" had a 2,800
cu. in. displacement and could generate
1,850 horsepower at takeoff and 1,500 mph
at 14,000 feet. The engine had just passed
Type tests and was an American first - no
other air-cooled engine come close to such
The Winning Martin Model 179 Design
ABOUT CLASS! The martin
design was love at first sight.
It was the quintessential two
engined air racer - a "doing
one hundred miles an hour standing
on the ground" design.
The aircraft manifested
the limits of the aerodynamic
state of the art and was by
far the most aesthetically appealing
of all bids submitted.
design features included:
fuselage to provide
maximum interior space,
minimum friction, and manufacturing
short, broad-chord, and
with only a 1.3 degree dihedral
that made it practically
straight. High mounting
of the wings was necessary
to provide clearance for
the 13 1/2 foot Curtiss
end-to-end bomb bays
to accommodate the thirty
100-pound requirement. The
aft bomb bays doors were
to fold up in a unique "accordion
style" to give sufficient
ground clearance for bomb
loading and the rear opened
in the more conventional
.30-caliber machine guns.
One each in the: nose, top
turret, ventral turret,
underslung engine nacelles
of similar aerodynamic profile
as the fuselage. Large spinners
were attached to the props
to fair them smoothly into
tanks of 360 gal. capacity
were inboard of each engine
nacelle and 121 gal. auxiliary
tanks were located outboard
of the engines.
aspect ratio (relationship
of span to chord) was extremely
low at 7.05 to keep wing
loading (gross weight divided
by wing area) was extremely
high at 45 pound per square
foot. This yielded a stall
speed of 97 mph - pilots
at the time considered coming
in at anything over 70 mph
- for a fighter plane.
tail with tricycle landing
& takeoff speeds/distances
greater than any plane
flying at that time.
30 caliber guns had been specified for the original
armament, but this was increased when Martin developed
a power-operated deck gun turret, the first such turret
to go into American production.
fuel tanks and 555 lbs. of armor were specified for
a B-26A version added on option to the original contract,
and by 30th September 1940, the Army decided to include
these features on all B-26's under construction.
the first B-26 had yet to fly, the orders for 139 B-26A's
on 16th September and 791 B-26B's on 28th September
1940 brought the total on order to 1,131 aircraft. No
prototype, as such, was planned because of the Army's
desire to get its new medium bombers into production.
25th November 1940, chief engineer and test pilot William
K. Ebel lifted 40-1361, the first B-26, on its maiden
flight. Its streamlined form, from the plexiglass nose
cone to the tail cone behind the single rudder, earned
immediate attention as a virtual "flying torpedo".
original contract specification was for an empty weight
of 19,250 lbs. and gross weight of 26,625 lbs. with
a guaranteed performance of 323 m.p.h. top speed,
26,440 feet service ceiling and range of 1,800 miles.
The actual B-26 aircraft weighed 21,375 lbs. empty and
27,200 lbs. gross in design condition. Top speed was
315 m.p.h. at 15,000 feet, service ceiling 25,000 feet
and range was 1,000 miles at 265 m.p.h. with 3,000 lb.
bomb load and 962 gallons of fuel. Maximum ferry range
was 2,200 miles with 1,212 gallons.
included a wing span of 65 feet, 602 sq. ft. wing area,
56 feet length and 19 ft. 10 in. height. Effects of
the high wing loading were shown in the 2,500 feet takeoff
run, 12.5 minutes required to climb to 15,000 feet,
and 103 m.p.h. landing speed.
included a 30 caliber flexible gun in the nose operated
by the bombardier, two 50 caliber guns in the deck turret,
another 30 caliber flexible gun at a bottom opening,
and another 50 caliber flexible gun in the tail turret.
The tail gunner had room enough to sit upright, unlike
the prone position on the earlier B-23 and B-25 types.
Ammunition supply included 1,200 30 caliber rounds
and 1,200 50 caliber rounds. A pair of 2,000 lb. bombs
could be accommodated in the main bomb bay, with up
to 4,800 lb. of smaller bombs available if the aft bay
first 113 hours of testing went well without serious
incident, and in February 1941 the first four aircraft
were accepted, by the Army Air Corps. At Langley Field,
Virginia, the 22nd Bombardment Group (Medium) became
the first to use the B-26. But of 66 Martins accepted
by June, only 21 had been delivered, with 44 remaining
in storage. A series of failures of the front wheel
strut caused the delay in bringing the B-26 to operational
status. The strut was strengthened but it was discovered
that the accidents had been due to improper weight distribution.
The manufacturer had to deliver the aircraft without
guns, and had trimmed the new B-26's for delivery flights
by carefully loading service tools and spare parts in
a prescribed manner. When the Army took over, these
were removed without replacement ballast. The resultant
forward movement of the centre of gravity had multiplied
the loads on the nose wheel, causing the accidents.
of the guns corrected the problem, and in October 1941
Martin's production lines completed the original contract
and delivered the first B-26A, 41-7345. This model differed
from the first mainly by provision for an extra ferry
tank in the rear bomb bay. Thirty had the R-2,800-5
Wasps, but 109 delivered with the R-2,800-39 of identical
power were known as the B-26A- 1. Weight had increased
to 21,741 lbs. empty, 28,367 lbs. gross, and ferry range
to 2,600 miles with 1,462 gallons.
1942, many of the original B-26's were fitted with the
extra ferry tanks, and the B-26 and B-26A mingled in
service. These Martins had received the name "Marauder"
in October 1941. Some ships had replaced the 30
caliber nose gun with a 50 caliber weapon. Fifty-two
B-26A's, serials FK1O9 to FK16O, were assigned to the
Royal Air Force with the name "Marauder I".
By the time production of the B-26A was completed in
April 1942, the Marauder had entered combat.