This aircraft was designed for a competition, announced in 1934, to find
a modern replacement for the assorted Keystone biplane bombers
then in service. The prototype first flew on July 28,1935, and went on
to win the competition. The manufacturer then built a few preproduction
YlB-17s (later re-designated), followed by 39 planes which entered
service in the late thirties. Money was short, and by the autumn of 1939
only 30 aircraft were fully operational. As the US was not then fighting
in Europe it did not seem to matter although, as it became clearer that
involvement was inevitable, orders were increased. Furthermore, a small
number of planes were delivered to the RAF and it quickly showed that
defensive armament was inadequate.
In September of 1941, a new version appeared with an extensively
modified empennage. Gone was the pert fin and rudder riding precariously
behind the stabilizer. Instead, a broad yet graceful dorsal fin rose
from amidships and enveloped a deadly stinger of twin .50-cal. machine
guns. A remote controlled belly turret held two more .50s. This was the
model, of which 112 were built. Four hundred more followed but with a
manned Sperry ball turret replacing the remote system. It was then
lengthened to 73 feet 10 inches to accommodate the new defensive tail
position. Top speed was 317 mph, cruising at over 200 mph with 4,000
pounds of bombs.
The Pearl Harbor attack of December 7,1941 finally brought the United
States into the war and production rapidly increased. By July 1942 the
US began forming the Eighth Air Force in Britain, equipped with the "E"
version of this plane. The 'E' represented an important improvement over
the earlier versions, in that it had a tail turret, so eliminating a
previous defensive blind spot. On August 17,1942 United States carried
out a bombing raid on the railway yards at Rouen in France using this
plane. The real offensive, however, started on January 27,1943, when the
USAAF made their first attack on Germany. Initially, casualties were
very high because they attacked during daylight hours to achieve greater
accuracy and because proper formation flying (to enable a group of
airplanes to defend each other with crossfire) had not yet been
formulated. Delivery of the "G" version helped. The 'G' was the first
variant to have a gun turret under the nose, so increasing the armament
to 13 guns.
Production of the similar plane was undertaken by Douglas and Vega, a
subsidiary of the Lockheed Aircraft Corp., was taking its toll in speed.
The "F" version, though now armed with eleven .50-cal. guns, could only
reach 299 mph, but landing speed was up to 90 mph! Service ceiling was
37,500 feet and range 2,880 miles. It took twenty-five and a half
minutes to climb to 20,000 feet. Three thousand, four hundred planes
were produced by the three companies.
By September 1943, the aircraft showed its final shape. During firepower
tests on the XB-40, a modified version, the advantage of a chin turret
was clearly proven and a new series, labeled "G", sported this nasal
appendage. The Bendix turret held two .50-cal. guns and this model had a
total of twelve of these weapons with 6,380 rounds of ammunition. In
all, there were 8,680 planes built by Boeing, Vega, and Douglas to make
this the largest production variation. Following the first Model 299,
the Air Corps purchased 12,725 "B" type aircraft.
On 19 July 1943 this plane and
Liberators carried out the first bombing raid on Rome; and US
bombing in Europe reached its high point in February 1945 with a
1,000-bomber raid on Berlin, escorted by 400 fighters, and the Dresden
raid (alongside the Royal Air Force) which caused a massive fire storm
to sweep the city.
Meanwhile, these planes were also helping to win the war against Japan,
although by mid-1943 the larger B-29 had begun to take over the
major strategic bombing missions. By the end of production, more than
12,700 planes had been built, of which a few served with Royal Air Force
Coastal Command and the United States Navy for patrol, air-sea rescue,
antisubmarine and other duties.
Specifications included a span of 103 feet 9 inches, length of 74 feet 4
inches, and a height of 19 feet 1 inch. The four supercharged
R-1820-97 Cyclones delivered 1,200 hp and gave a top speed of 287
mph, cruising at 182 mph. Service ceiling was 35,600 feet, with a range
of 3,400 miles. Empty and gross weights were 36,135 pounds and 55,000
pounds. Maximum fuel load was 3,630 gallons.
Cargo conversions of this plane were known as C-108.