Beyond the engines and ball turret, the F-model was notable in bringing about a single-piece plexiglass nose cone which did away with the complex, heavily-framed unit of earlier production models. This gave the bombardier one of the most impressive views from the aircraft as he was able to see through an unobstructed pane over all of the forward field of the bomber - very useful in identifying ground-based target areas for his role.
These changes led to a greater overall weight for the heavy bomber but this was acceptable amidst the growing demands of the war. The F-models took over production lines from the now-abandoned E-models and 3,405 units were added to the B-17 stable - Boeing contributed 2,300 aircraft while 605 arrived from Douglas Aircraft plants, and a further 500 came from Lockheed Vega facilities - a joint effort to be sure.
The B-17 Comes of Age - the Definitive B-17G
The evolution of the B-17 was fast and furious with much owed to the evolution of the war itself. The B-17G model was a major upgrade over previous versions and became the undisputed definitive form of the series. It carried over the refinements of the improved F-models mentioned earlier but also introduced the twin-gunned, electrically-powered Bendix chin turret for the bombardier's position. One of the lingering limitations of the defensive network of earlier B-17s was its defense against oncoming attacks by enemy fighters. There were "cheek" machine guns the bombardier and navigation could rely on as well as some support from the dorsal turret but these held restricted firing arcs when concerning direct frontal threats. The Bendix installation gave unrestricted access to the forward field of the aircraft and could scan across the horizon for threats side-to-side. German pilots were, no doubt, surprised that their frontal attacks were no longer useful and, instead, greeted with hot lead from twin 0.50 caliber Brownings.
Beyond this armament improvement came an increased war load capability: the bomber now capable of carrying up to 90,000lb of conventional drop stores over distance. Boeing contributed 4,035 G-models while Douglas added 2,395, and Lockheed Vega another 2,250 units.
The B-17 In Action
B-17 Flying Fortresses followed common bomber doctrine of the time in that the units were arranged in what was known as a "box formation". This formation, made up of multiple individual bombers flying within relatively close proximity to one another, allowed virtually every machine gunner onboard the respective aircraft to bring their guns to bear against any impending threat as needed through combined firepower. With no fewer than twelve machine guns featured on a single G-model, a sole B-17 was quite the defensive network for enemy fighters to get through during an attack run.
Gunner positions on a B-17G model included 2 x 0.50 caliber machine guns in the Bendix chin turret, 1 x 0.50 caliber machine guns at each cheek position, 2 x 0.50 caliber machine guns at the dorsal turret, 2 x 0.50 caliber machine guns at the ventral ball turret, 1 x 0.50 caliber machine guns at each beam position, and 2 x 0.50 caliber machine guns at the tail position. In theory, no one approach route outside of the bomber was uncontested. All positions were afforded some level of armor protection but this varied considerably by position.
The Norden Bombsight
One of the major challenges of bombing in the 1930-1940 period was accuracy and there were several technological attempts made to aid the bombardier in his role but none were as critical to the war effort as was the Norden Bombsight designed by Carl Lukas Norden - who previously had worked for the Sperry Gyroscope Company before World War 1 (1914-1918). Lucas first interested the United States Navy (USN) in his invention as the service sought to increase the lethality of its own bombers against moving enemy warships. The early-form Mk III bombsight was developed in 1921 from this requirement and the design eventually progressed to the M-Series units which were adopted in 1943.
The bombsight was instrumental in gradually increasing accuracy of American bombers and this improved from a near 25% accuracy (within 1,000 yards) to about 40% (within 500 yards) by 1944 and beyond. The bombardier was also allowed lateral control of the aircraft from the pilot during the bombing run which further gave aided the bombardier in placing the ordnance where it had to go. Bomber flights frequently followed a lead plane as their "director" and would drop war loads on queue. As such, the lead bombardier was to make absolutely sure he was over the correct target and this was accomplished by studying photography and maps for hours on end to verify physical structures and landmarks. During the bomb run itself, there were also the pressures of Flak attack, enemy fighter drives, and the like - external distractions not properly replicated in training. His job was made easier by a competent navigator whose primary role was to get the bomber to within range of the target by way of maps and measurements. The pilots fed off of the navigator's direction and the radioman aided the effort as well. In this way, the entire B-17 core crew was required to reach some level of cohesion for not only mission success but also unit survival.
About 40,000 candidates graduated from the USAAF bombardier program related to use of the ultra-secret Norden bombsight system.
The B-17 Cockpit
The pilot and co-pilot sat in the cockpit in a side-by-side arrangement with engine/throttle controls seated between them - offering equal control access. Each pilot also had a good view of his respective engine pairing for monitoring against fires and general failures. Either pilot could also control the aircraft as needed through their control yokes which was particularly useful should one crewman become incapacitated or killed during a mission. Views out-of-the-cockpit were generally adequate but restricted on the whole - ground-running certainly required the assistance of ground personnel for direction.
B-17 Reliability
The B-17 quickly became recognized for its ability to sustain an extraordinary amount of combat punishment and keep flying. This is not to say that the design was invulnerable to enemy attack - for many B-17 bombers and B-17 bomber crews lost their lives during the war - but the Boeing product was known to limp back home with even entire sections of aircraft missing. Whole sections of tail unit could be shot away or the fuselage blown open or severed to the point of nearly falling off but the Boeing bomber continued to "bring the boys home" time-and-time-again. While fighters were one direct threat, the seemingly random nature of ground-based FlaK fire were terrifying for the bomber formations required to hold course while entering into what was essentially an aerial minefield. When the enemy interceptors stopped attacking the Fortress, this was a sure sign that an extensive FlaK attack was to follow.
Despite all of the dangers, B-17 crews did their jobs successfully throughout the entire course of the war. This led the bomber to become a symbol of American aerial might over its enemies and was the principle component in the dismantling of the Reich's war-making capability into 1945. A flight of thousands of such bombers became commonplace heading into the final year of the war and the German nation capitulated under pressure from all sides by May of that year, signaling the end of the war in Europe. B-17s also did their part in the Pacific Theater and ultimately paved the way for the high-flying Boeing B-29 "Superfortress" which eventually dropped the atomic bombs on Hiroshima and Nagasaki to help end the war in the East.
B-17 Post-War Exposure
Total production of B-17s reached 12,731 units by war's end. Production spanned from 1936 until 1945. Beyond the United States and Great Britain, the B-17 was taken into service by a plethora of global operations mainly during the post-war years and these were used in both military and civilian markets. Operators ranged from Brazil, Canada, and Columbia to Portugal, the Soviet Union, and the Republic of China.
During the war, those B-17s operating in the Far East and unable to return to American bases in the region for one reason or another were forced to land on Soviet soil and these specimens were interned and reengineered by the Soviets down to the last bolts. This jumpstarted the Soviet bomber program of the Cold War period and resulted in types like the Tupolev Tu-4 which took over for the refurbished B-17s in Soviet service. Soviet B-17s operated into 1948.
Similarly during the war, the German regime captured as many as forty B-17s in various conditions and refurbished them back into fighting form. These were known locally as the Dornier Do 200 and used in reconnaissance and general spying roles through Luftwaffe unit KG 200.
When Israel was formed as a nation in 1948, it took on three B-17s when establishing its newly-founded air service. The specimens were obtained through Czech and South American sources and were pressed into combat during the 1948 Arab-Israeli War as the subsequent 1956 Suez Crisis, the fleet flying into 1958.
Notable Projects and Offshoots
While there proved many derivatives of the base B-17 design throughout its storied career, two were notable in their attempts - the XB-38 and the XB-40, both based on the established framework of the original B-17 (and both detailed elsewhere on this site). The XB-38, based in the B-17E model, was an attempt to develop an inline piston-engined form of the Flying Fortress to maximize performance of the heavy bomber. 4 x Allison V1710-89 12-cylinder units of 1,425 horsepower each replaced the typical air-cooled radials during the program and this allowed streamlined engine nacelles to be used for better aerodynamics. While performance was, in fact, improved, the sole prototype was consumed by fire in a June 1943 test which ended its flying days. This fire, and the arrival of F-models production units as well as the Allison inline engines being required elsewhere, all contributed to the end of the XB-38.
The XB-40/YB-40 was an F-model B-17 modified by Lockheed Vega to serve as a flying "Gun Bus" reminiscent of World War 1 types intended to escort vulnerable bombers into contested airspace. This was developed prior to jettisonable fuel drop tanks being adopted and longer-ranged escort fighters being available in number. Armament was variable on these aircraft due to their developmental status and some twenty-five aircraft emerged from the program. The Gun Bus variant included extra 0.50 caliber machine guns as well as automatic cannons to go along with improved crew station armoring. Some carried multiple dorsal turrets and individual twin-gunned positions.
The "improvements" led to an aircraft that was heavier by some 4,000lb when compared to a fully-laden B-17 bomber. Decreased performance due to weight gains and added drag, as well as the arrival of long-range P-51 Mustang fighters as escorts, all contributed to the death of the B-17 Gun Bus project. However, these gunships were used in operational service (though for only a short time) with the first mission flown in May of 1943. it was found that these gun-laden heavies had trouble keeping up with the formations once the bombers had dropped their loads. The XB-40/YB-40 program was ended in August of 1943.
The C-108 was the B-17 converted to serve in the transport role. General Douglas MacArthur's own C-108, named the "Bataan", became the most famous of these and was used in the VIP transport role across the Pacific Theater until war's end. The fleet was made up of E- and G-models and some were sent over to the United States Coast Guard service to operate in the Search and Rescue (SAR) role over water. These forms was additionally outfitted with radar for the task.
The B-17 was instrumental in the development of another Boeing product, the Model 307 "Stratoliner", a passenger-hauler introduced in July of 1940 with Pan American Airways. Just ten of these transports were completed but the series operated into 1975.
Beyond these were G-model inspired troop transports, drone aircraft, static and flyable test articles, a missile carrier (MB-17G), reconnaissance platforms (RB-17G), a lifeboat-equipped model (SB-17G), trainers, and an AWACS form (PB-1W) - such was the versatility of the aircraft.
Notable B-17 Bombers
Due simply to the sheer number of B-17 bombers built, and their constant exposure to combat in World War 2, it was only natural that many of the type went on to have highly publicized careers - the most famous of the these becoming the "Memphis Belle". A few notables of the bomber line are briefly detailed below:
Memphis Belle - The Memphis Belle, named after Margaret Polk of Memphis, Tennessee (who was then the girlfriend of the bomber's pilot, Lt. Robert Morgan), carried the iconic nose art of a leggy woman with her face turned away from the viewer (she wore blue on the portside of the forward fuselage and was depicted in red along the starboard side). She was painted by artist Tony Starcer of the 91st Bombardment Group onto the nose of a B-17F. The bomber is notable in being recognized as the first B-17 Flying Fortress to have completed a tour of 25 combat missions which meant that the crew had earned the right to return stateside for good (the aircraft also claimed eight air victories against the Luftwaffe in that time frame). The Belle went on to serve in war bond drives and the like during the conflict and ultimately ended in the care of the National Museum of the United States Air Force (Dayton, Ohio). A Hollywood version of the true story of the Memphis Belle appeared as a motion picture in 1990 (the bomber was played by the still-flying B-17G "Sally B"). During the war in 1944, the aircraft was also the subject of the 45-minute-long documentary "Memphis Belle: A Story of a Flying Fortress" which was meant to depict the final mission of the bomber (in reality it was actually the second-to-last mission flown).
Hell's Angels - The Hell's Angels was a B-17F named after the 1930s Howard Hughes movie "Hell's Angels". By January of 1944, this bomber had completed 48 total missions and she and her crew were sent stateside to drum up support for the war effort. She ended her days in March Field (California) to serve as a crew trainer from May of 1944 onward. Unfortunately this Flying Fortress was not saved from the scrap heap.
The Swoose - The Swoose operated from April 1941 until February of 1944 and went on to be preserved - the only one of the earlier B-17D models to be saved and of note being its distinct "shark fin" vertical tailplane. The Swoose operated from the first day of the U.S. entry into World War 2 (December 1941) and managed to survive the war intact. After suffering through periods of exposure to weather and damage (the latter at the hands of lowly vandals), the aircraft was saved for preservation work by the National Museum of the United States Air Force (Dayton, Ohio).
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