Boeing B 17 Flying Fortress
Although it is sometimes introduced as the most famous of all US World
War 11 aircraft, there are many who will argue that Boeing's B-17
Flying Fortress ranks equally with several other superb machines which
became available to the US Army at just the right moment. The North
American P-51 Mustang has its ardent advocates for pride of place in
the USAAF's wartime armoury, but it was a child of war, conceived to
live, fight and endure in the battle-torn skies of Europe. The origin
of the Fortress was very different, its gestation long and troubled.
the first few years after World War I the US Army Air Corps' Brigadier
General William ('Billy') Mitchell began his campaign in favour of
strategic bombing, demonstrating (perhaps inconclusively) the
ascendancy of bomber over battleship in July 1921 and September 1923 by
the destruction of captured or obsolete warships anchored at sea. His
burning belief in air power led to a bitter campaign, against the US
Navy initially, but later involving also the US Army. In the last month
of 1925 'Billy' Mitchell was court-martialled and suspended from the
service. He resigned very soon after this verdict, so that he could
continue his campaign for the creation of the air force which he
believed was needed by the USA. World War II was to prove him right in
his ideas for in 1946, 10 years after his death, he was elevated to the
rank of the nation's heroes by the posthumous award of the
Congressional Medal of Honour.
Although Mitchell had been discredited in 1925, there were many of his
former colleagues who were less outspoken but nevertheless believed in
the concept of air power. With Mitchell no longer there to provide
support and encouragement, the efforts of this small steering nucleus
were necessarily slow. More far sighted, in some ways, were the
nation's aircraft manufacturers. Boeing, for example, began work in
1930 on its Models 214 and 215, twin-engined developments of its
revolutionary Model 200 Monomail civil airliner. Built as a private
venture these were ordered in small numbers as Y1B-9 and YB-9, but the
first significant order for monoplane bombers went to the Glenn L.
Martin Company for 48 twin-engined B-10 bombers.
Deliveries of production B-10s began in June 1934, and in a changed
climate of opinion the US Army had issued a month earlier its
specification for an even more advanced multi-engined bomber, able to
haul a bomb load of 2,000 lbs (907 kg) over a range of between 1,020
miles (1640 km) and, optimistically, 2,200 miles (3540 km), at speeds
of between 200 - 250 mph (322 - 402 km/h). So far as the US Army was
concerned, 'multi' meant more than one engine but Boeing, invited to
submit its proposal for this requirement, elected to use four engines
to power its Model 299, on which design work was initiated in mid-June
Boeing the Model 299, built as a private venture, was a make or break
gamble. Hitherto the company had built aircraft in only 'penny packet'
numbers. The failure of the B-9 to win a worthwhile order had forced
economies af near desperation upon Boeing, with its work force split in
half and working two weeks on and two weeks off. Unless the Model 299
entered production in significant numbers the company faced, at the
least, a very bleak prospect. Not surprisingly, every effort was
devoted to the success of the project; every employee knew that he or
she had an important contribution to make if the company was to
US Army specification had stipulated that the prototype should be
available for test in August 1935, and however impossible this target
had seemed in mid-1934, it became reality on 16 July 1935 when the
Model 299 was rolled out of its hangar at Boeing Field, Seattle, for
its first introduction to the press. Headlines on the following day
announced the new'15-ton Flying Fortress', and seizing upon the name
the company had it registered as the official name of its Model 299.
Contrary to popular belief, this was not because of its defensive
armament, but because it was procured as an aircraft which would be
operated as a mobile flying fortress to protect America's coastline, a
concept which needs some explanation.
USAAC protagonists of air power were still compelled to step warily,
despite procurement of the B-10 bomber, for the US Navy had the most
prestigious support in the corridors of power and was determined to
keep the upstart US Army in its place. Even if strategic bombers were
required, efforts must be made to prevent the US Army acquiring such
machines. The USAAC was, however, quite astute when needs be and so,
with tongue in cheek, succeeded in procuring 13 YB-17s, the original
service designation of the Fortress, for coastal defence. However, this
explanation anticipates the story.
28 July 1935 the Model 299 flew for the first time: just over three
weeks later it was flown non-stop to Wright Field, Ohio, to be handed
over for official test and evaluation. The 2,100-mile (3 380-km) flight
had been made at an average speed of 252 mph (406 km/h), a most
impressive performance which augured well for the future. The elation
of the Boeing company was understandable, especially with confirmation
that initial trials were progressing well. On 30 October 1935 hopes
were dashed with the news that the prototype had crashed on take-off.
Subsequent investigation was to prove that the attempt to take-off had
been made with the controls locked, and in view of the satisfactory
testing prior to this accident, the USAAC decided on the procurement of
13 YB-17s (later Y1B-17s), plus one example for static testing.
prototype (X13372) which had crashed at Wright Field was powered by
four 750 hp (559 kW) Pratt & Whitney R-1690-E Hornet radial engines.
The cantilever monoplane wings were in a low-wing configuration, the
wing section at the root so thick that it was equal to half the
diameter of the circular-section fuselage; and wide-span trailing-edge
flaps were provided to help reduce take-off and landing speeds. Landing
gear was of the electrically retractable tailwheel type. Armament
comprised five machine-guns, and a maximum bomb load of 4,800 lbs (2177
kg) could be carried in the fuselage bomb bay.
initial Y1B-17 (36-149) flew for the first time on 2 December 1936, and
differed from the prototype by having 930-hp (694-kW) Wright GR-1820-39
Cyclone radials, accommodation for a crew of nine, and minor changes in
detail. Twelve were delivered between January and August 1937,
equipping the USAAC's 2nd Bombardment Group at Langley Field, Virginia.
The thirteenth aircraft went to Wright Field for further tests and
after one of the Y1B-17s survived without damage the turbulence of a
violent storm, it was decided that the static test example would,
instead, be completed as an operational aircraft. Designated Y1B-17A,
this aircraft (37-369) was provided with 1,000 hp (746 kW) GR-1820-51
engines each fitted with a Moss/ General Electric turbocharger
(supercharger powered by a turbine driven by exhaust gases). It flew
for the first time on 29 April 1938, and subsequent testing by the
USAAC gave convincing proof of the superiority of the turbocharged
engine over those which were normally aspirated, and such engines were
to become standard on all future versions of the Fortress.
utilisation of the Y1B-17s, designated B-17 in service with the 2nd
Bombardment Group, did little to improve relations between the US Army
and US Navy. When three of the force were used to stage an
'interception' of the Italian liner Rex some 750 miles (1207 km) out in
the Atlantic, to demonstrate that the USAAC was more than capable of
defending the nation's coastline, it sparked a row which dispersed the
air power disciples from General Headquarters Air Force (GHQAF) to
other commands, where they were remote from each other and potential
influential supporters. Orders for additional B-17s had to be reduced
after it had been underlined by Major General Stanley D. Embrick that .
. . "the military superiority of a B-17 over the two or three smaller
aircraft which could be procured with the same funds has yet to be
established." This helps explain why, despite the growing war clouds in
Europe, the USAAC had less than 30 B-17s when Hitler's forces invaded
Poland on 1 September 1939.
order for Y1B-17s was followed by a contract for 39 B-17Bs, more or
less identical to the Y1B-17A prototype with turbocharged engines. The
first of these flew on 27 June 1939, and all had been delivered by
March 1940. In 1939 the B-17C was ordered, the first of the 38 on
contract making its first flight on 21 July 1940. They differed by
having 1,200 hp (895 kW) R-1820-65 engines, and by an increase from
five to seven machine guns.
B-17C was the first version of this bomber to be supplied to the RAF in
Great Britain, which designated the 20 examples received in early 1941
as Fortress I. Equipping No. 90 Squadron, they were used operationally
for the first time on 8 July 1941 when aircraft launched a
high-altitude (30,000 ft / 9145 m) attack on Wilhelmshaven. In the 26
attacks made on German targets during the next two months the Fortress
Is proved unsatisfactory, although there was American criticism of the
way in which they had been deployed. Nonetheless, their use in daylight
over German territory had proved that their operating altitude was an
inadequate defence in itself, and so they needed more formidable
defensive armament, for Messerschmitt Bf 109E and 109F fighters had
little difficulty in intercepting them at heights of up to 32,000 ft
(9750 m). Until improvements in the Fortress were made, or means found
of deploying them more effectively, they were withdrawn from operations
With the end of 1941 drawing near, the USA was soon to become involved
in World War 11, initially in the Pacific theatre, but following the
containment of the initial explosion of Japanese expansion it was
decided that the Allies would first concentrate their efforts on
bringing about a speedy conclusion of the war in Europe. Thus, large
numbers of B-17s which otherwise would have found employment in the Far
East were instead to equip the USAAF's 5th Air Force in Britain. Those
allocated to serve with the Anglo-American Northwest African Air Forces
were later to become part of the US 15th Air Force.
1940 Boeing received an order for 42 B-17Ds. These differed little from
the B-17C, but as a result of early reports of combat conditions in
Europe were provided with self-sealing tanks and additional armour for
protection of the crew, and these were delivered during 1941. The B-17E
which followed was the first version to benefit from the RAF's
operational experience with its Fortress Is. A major redesign provided
a much larger tail unit to improve stability at high altitude, and to
overcome the criticism of inadequate defence 13 machine-guns were
mounted in one manual and two power-operated turrets, radio
compartment, waist stations and in the nose. Of the 512 of this version
built under two contracts, the first flew on 5 September 1941. B-17Es
were the first to serve with the 8th Air Force in Europe, with
deliveries beginning in July 1942. They were used operationally for the
first time by the 97th Bombardment Group, 12 aircraft being detailed
for a daylight attack on Rouen on 17 August, with fighter escort
provided by RAF Supermarine Spitfires.
B-17F, of which the first flew on 30 May 1942, was the first version to
be built in large numbers. Boeing produced 2,300 at Seattle, and
further construction of 1,105 came from Douglas (605) and Lockheed Vega
(500). Major changes included a redesigned nose, and strengthened
landing gear to cater for a higher gross weight. Other changes included
increased fuel capacity, the introduction of additional armour,
provision of external bomb racks beneath the inner wings and, on late
production aircraft, the introduction of R-1820-97 engines.
B-17Es and B-17Fs became used extensively by the 8th Air Force in
Europe, but in two major operations against German strategic targets,
on 17 August and 14 October 1943, a total of 120 aircraft were lost.
Clearly the Fortresses could not mount an adequate defence, no matter
how cleverly devised was the box formation in which they flew. The hard
truth was that without adequate long-range fighter escort they were
very vulnerable to attack during mass daylight operations. Many of the
losses were attributed to head-on attack, and the final major
production version was planned to offset this shortcoming.
Thus the B-17Gs had a 'chin' turret housing two 12.7 mm (0.50 in)
machine guns mounted beneath the fuselage nose, which meant that this
version carried a total of thirteen 12.7 mm (0.50 in) guns. To increase
the aircraft's operational ceiling, later production examples had an
improved turbocharger for their R-1820-97 engines. B-17G production
totalled 8,680, built by Boeing (4,035), Douglas (2,395), and Lockheed
Although used most extensively in Europe and the Middle East, B-17s
were operational in every area where US forces were fighting. In the
Pacific theatre they offered invaluable service for maritime patrol,
reconnaissance, and conventional and close-support bombing. A number of
variants were also produced or converted for special purposes and
operations, and details of these follow. Although almost 13,000 B-17s
were built, only a few hundred B-17Gs were retained in USAAF service
after the end of the war, and these were soon made redundant
Nicknames: Fort; The
Flying Coffin (Nazi propaganda nickname)
Engines: Four 1,200-hp Wright
R-1820-97 Cyclone turbocharged radial piston engines
Weight: Empty 36,135 lbs.,
Max Takeoff 65,500 lbs.
Wing Span: 103ft. 9in.
Length: 74ft. 4in.
Height: 19ft. 1in.
Maximum Speed at 25,000 ft:
Cruising Speed: 182 mph
Ceiling: 35,800 ft.
Range: 2,000 miles with
6,000 lb. bomb load
13 12.7-mm (0.5-inch) machine guns
Up to 17,600 pounds of bombs
Number Still Airworthy: