Units of History B 17 Flying Fortress DOCUMENTARY

The B-17 stands as one of the most iconic and mass-produced bombers of American aviation history. This reputation is in large part due to the unparalleled quantity of mounted turret and machine gun positions, which earned it the name the Flying Fortress. Certainly, the maelstrom of fire such a beast could unleash was formidable. Yet, there is more to this plane than meets the eye. From its early adoption of autopilot technology to its billion-dollar Norden bombsight, its four air-cooled, nine-cylinder radial engines with coupled turbo-superchargers, and self-sealing fuel tanks, its life-support system for high-altitude environments, and more. So today, let's see how the B-17 Flying Fortress really worked. The B-17 and the aerial campaigns of the Second World War were ultimately just a small part of a wider conflict unfolding around them. But you can get involved in strategy and campaigning on this grander scale with today's sponsor, Conflict of Nations. 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So check it out, enjoy, and good luck out there. and air-to-air combat. While their overall impact was relatively small, militaries of the interwar period quickly realized the future potential of aircraft. This led to a feverish development in both the commercial and military industries. Out of this churn would emerge a range of new technologies, major archetypes, and subtypes. Coupled with this technical side came the theory of its use. Key to our story would be the idea of strategic bombing. It postulated that air power could allow one to simply fly over the front lines and pummel the enemy's homeland into submission. Of course, this concept cut both ways. Thus, a range of stratagems and counter-stratagems involving fighters, escorts, and intricate formations were developed. Yet their delicate balance could easily be upset by new innovations. Thus it was that in 1934, the U.S. Army Air Corps put out a call for the delivery of a state-of-the-art multi-engine high-altitude bomber set to be judged at a fly-off the following year. Among the most ambitious entries would be the Boeing Model 299. Not only did it feature double the number of engines as its competitors with top-of-the-line flight characteristics and a host of other innovative features, but it was brimming with machine guns facing in all directions. This caught the attention of the press, which dubbed it the Flying Fortress, a name which Boeing quickly trademarked. Unfortunately, a tragic crash during the fly-off disqualified the B299 from the competition. However, it had clearly won over fans in high places. After further rounds of improvement, the Army soon ordered small numbers of test models. Once service testing was complete, Boeing was ready to begin delivering operational models which bore the famous title the B-17. A few batches of planes would be ordered by the Air Corps over the following years, with an eventual July 1940 order for a whopping 512 planes. While fewer than 200 of these were available by the time of Pearl Harbor, Boeing was ready to begin mass production. In the end, the company would deploy its aircraft across every theater of World War II, with nearly 13,000 B-17s being produced, the highest number of any American bomber in the war. With this context in mind, let us take a closer look at this marvel of engineering, starting with an overview of its features and its crew before diving into the guts of its operating systems. From its inception, the physical features of the B-17 would face a near-continuous stream of modifications to adapt to feedback from the field, as well as pressures of logistics, financing, and engineering. This spawned numerous models and variants whose nuances we will not have time to cover. Instead, we can focus on its final production version, the B-17G. In overall dimension, it measured roughly 75 feet long and 103 feet wide, with a standing height of almost 20 feet. For propulsion, it was given flight by four air-cooled nine-cylinder radial engines with coupled turbo-superchargers. These were fueled by both dedicated and filler tanks located in the wings. Hydraulics, meanwhile, operated the wheel brakes and engine cowl flaps, while electricity operated the landing gear, tailgear, wing flaps, and bomb bay doors. Various other systems provided heating, de-icing, oxygen, and communications. A sophisticated autopilot system was even present to assist with bombing runs. The bomb bay was rated for roughly 8,000 pounds worth of rack-mounted explosives. Special racks helped increase this capacity, while either wing could bear an additional 4,000 pounds of payload. On the approach, these would be aimed by the Norden bombsight, whose secret development had cost nearly two-thirds the price tag of the Manhattan Project. All of this would already have been quite impressive for a contemporary bomber. However, what made the Flying Fortress different was its formidable array of defensive firepower. The B-17 boasted four turret emplacements, with paired Browning M2 .50 caliber machine guns, in addition to five single MG positions spread across the plane. This totaled 13 machine guns, each capable of firing at a rate of 13 rounds a second. Thus, if all fired at once, the air around the B-17 could instantly be filled with hundreds of bullets in a veritable maelstrom of fire. The entire vehicle weighed in at 36,000 pounds when empty, and almost double that when fully armed and loaded. Even greater weights could be sustained for shorter missions. As a quick rundown of its flight capabilities, the B-17's four engines powered the bomber's propellers with 1,200 horsepower apiece. As a result, it could reach a top speed of 300 miles per hour and climb to its desired altitude of about 25,000 feet in 37 minutes. Operating here just below the common altitude of modern commercial planes, it cruised at a speed of 170 miles per hour. With a loaded range of some 2,000 miles, it could strike into the heart of occupied Europe and Germany itself. The B-17 was assigned a crew of 10. Its commanding officer was the pilot, and its second-in-command was the co-pilot. Joining them were two additional officers, the navigator and the bombardier. On a typical crew near the end of the war, all would have been 1st or 2nd lieutenants. However, captains, majors, and even generals may have filled these slots for important operations. Joining them was a radio operator, a flight engineer, and a left-waist gunner, who held the rank of technical sergeant. The remaining three men were gunners with the rank of sergeant or staff sergeant. All crewmen were highly trained specialists who had passed through the aviation cadet training program and completed additional schooling in their respective disciplines. In terms of equipment, each crewman would have suited up with life-support systems meant to keep them alive in the low-pressure, low-oxygen, and low-temperature environment of high altitude. This included gloves, boots, and suits with built-in electrical heating elements. These would be powered by plugging into outlets at the various crew stations. Over these suits would be worn flak vests or flak aprons. A helmet provided additional insulation and protection, while a mask and tube supplied oxygen, which came either from A4 walk-around bottles or from the ship's oxygen system. For communication, the crew used a headset and paired comms throat microphone. Lastly, they would wear or have at their disposal a bailout parachute. Beyond this kit, various other small items might be carried as needed. In flight, the crew of a B-17 was arranged as follows. The bombardier sat at the very front of the plane in the nose section. Here he manned his equipment, which included the all-important bomb sight. During the final stages of a bombing run, he would take command of the plane. Otherwise, the bombardier stood ready to wield the remotely controlled chin turret. The navigator sat just behind him at a desk, with various instruments for determining position and communication. In combat, he had two cheek machine guns at his disposal. The pilot and co-pilot came next and were seated in the elevated flight deck, which contained all the essential flight control instruments. Behind them in the compartment came the engineer, who manned the top-mounted Sperry power turret. Aft came the bomb bay, which could be crossed by a narrow catwalk leading to the radio compartment. Here the radio operator sat at a desk with his communications equipment. Under the floor was a ground-facing camera, while above the ceiling lay a machine gun that could be fired out of the top hatch. Next came the waist section, with a series of three gunners. The first of these was the ball turret gunner, who would descend through a floor hatch into the Sperry ball turret. To his aft were two staggered waist gunner positions who protected either flank of the plane. In the very rear, a small door led to the tail section, where a fourth and final gunner manned the cramped quarters of the tail gun. To his side was an emergency exit, which could also be used for entry prior to take-off. Matching each of these crew positions and the location of key components would have been protective armour. This was a necessary upgrade, given the fact that while the B-17 was made of metal, its aluminium alloy frame and stressed metal skin had been optimised for weight rather than defence. In fact, parts of the plane, such as the flaps and ailerons, were even made of fabric. Thus it was that heavy metal armour had been carefully placed across the ship, based on feedback from the field and the famous analysis of statistical research groups. We can review these starting from fore to aft. The nose of the plane was protected in the front by a bulletproof plexiglass window. The rear of this compartment's bulkhead featured an armour plate rated to withstand machine-gun fire from a range of contemporary fighters. This in turn protected the front of the flight deck. The pilot and co-pilot's seats were each fitted with their own armour-backed chairs, while the rear bulkhead was also reinforced, which helped cover the top turret position. Behind them, the radio operator had his own armour-backed seat. In the bull turret below, a curved band of armour covered the rear of the gunner's seat position, while plexiglass covered the front. Further aft, meanwhile, each waist gunner's firing position had an armour-plated wall section. In prior B-17 models, the guns had been aligned, allowing each side's plate to provide simultaneous front and back support to both gunners. However, their close proximity proved to cramp, and so the B-17G compromised on defence to remedy this issue by slightly offsetting them. At the very tail of the plane, the gunner manned his post in a kneeling position against an armour plate. He gripped the gun on the other side by sliding his arms through special holes. Altogether, these upgrades, in addition to the flak armour worn by crew members, made them quite durable in combat. Let us now shift gears to review the internal systems which made the B-17 operational. We can begin with propulsion. Flight was achieved by spinning propellers to generate forward thrust. This motion in turn caused a flow of air over the wings, whose pressure differential lifted the plane. Understandably, the amount of power needed to achieve flight for the multi-ton B-17 was significant. Indeed, each set of propellers was driven by four of the 1,200 horsepower Wright Cyclone air-cooled nine-cylinder radial engines. Such a set-up not only provided top-of-the-line power, but also ensured redundancy in the face of failure or damage. Indeed, the B-17 proved capable of flight on just a single engine, a feature which saved many crews. Turbo-superchargers were used to compress intake air being fed to the engine in order to produce more power. At take-off, this meant generating greater-than-sea-level pressures, while at high altitude, this meant regaining the pressure one would expect on the ground. This worked by using intake ducts along the wing to pass the air into a compressor, at which point it would then be re-cooled before being passed into the engine's carburettor for mixing with fuel and subsequent ignition. Exhaust from the engine would then be harnessed to help run the compressor before being vented on the underside of the wing. The entire system would be controlled electronically. Each engine consumed roughly 50 gallons per hour while cruising. This was supplied by four independent fuel systems in the wings, one for each engine. Within each system, a large dedicated fuel tank was connected directly to the engine. It was in turn refilled by smaller feeder tanks distributed across the wing. Transfer was controlled by the flight engineer. Altogether, each system held roughly 700 gallons, or about 14 hours, of cruising fuel. Longer, non-combat flights might utilise extra fuel stored in 410-gallon bladders within the bomb bay. All tanks were self-sealing in the event of damage to preserve the integrity of the system. Also key to the functioning of the engines was an oil system, which provided lubrication, cooling and hydraulic pressure to operate both the propeller pitch and feathering mechanisms. To this end, each engine was paired with a 37-gallon tank and its associated connectors, valves, regulators and pumps. It would be the job of the pilot to operate these systems to actually fly the plane. This was made possible by the operational equipment in the cockpit. For the most part, the instrument dashboard was filled with important indicators and statuses on things like heading, altitude, airspeed and fuel levels. Most were clustered in the centre for dual-use. However, the co-pilot side was focused on engine management. The central pedestal controlled key functions of flight. Large throttle levers in the centre set the engine power. The levers beneath them determined the propeller pitch. And those above regulated the turbo superchargers and fuel mixtures. At the very top, a series of switches and dials above controlled things like the wing flaps, landing gear and ignition. The lower control pedestal housed controls and locks for both the elevator trim and the rudder. In its centre were the autopilot controls, which helped stabilise the aircraft and assist with flight. Beyond this, many other controls and indicators were distributed across the cabin, but for our purposes, the last major items to mention would be the aircraft yoke and rudder pedals. The former let you go up or down, while the latter steered left or right. Such commands were transferred to the appropriate plane parts via mechanical and cable linkages. There were also inbuilt buttons for communications, yoke lock and an autopilot quick release. Both the pilot and co-pilot had essentially the same setup. But while getting the plane into the air and flying its route was certainly important, many other systems were just as vital to the B-17's operation. Let us cover these now. At high altitudes, freezing was a very real threat to the plane. Various de-icer systems were therefore used. Windshields relied on wipers, alcohol spray and defroster air. Meanwhile, ice which had formed on the leading edges of wings was cracked and cleared by the inflation and deflation of rubber membranes known as de-icing boots, which were actuated by a vacuum pump. For the most part, the rest of the B-17 was left to the elements, with its crew simply wearing the appropriate gear to survive. As previously mentioned, this involved clothing with integrated electric heating elements, which could be powered by 10 receptacles located across the crew stations. However, a dedicated heating system was in place to warm the all-important personnel and equipment of the flight cabin. Here, a glycol line transferred heat from engine 2 into an air control unit. The pilot then had a control knob to switch vane positions, which directed either heated, ambient or no air into his cabin. Another important survival feature was the oxygen system. To this end, 19 Type G1 cylinders were stored across the plane, each one holding a 5-hour supply. A single filler line system helped charge all the bottles. Discharge to the crew, meanwhile, was broken out into 5 independent systems for increased resiliency. Should any cylinder be punctured, a check valve further guarded against any pressure loss. The terminus of each distribution line ended in a regulator, which furnished oxygen on demand or upon inhalation. Here, crewmen might plug in their breather tubes or charge their own walk-around oxygen tanks. The communications system allowed for conversation between crew members, ground personnel and external equipment. Comms were largely provided by 11 interphone jackboxes distributed across the crew stations. Here, users plugged in their headphones and throat mics. Some members had a station-integrated push-to-talk button, while others activated this button on their neck lanyard switches. Meanwhile, dials on each jackbox allowed crews to switch between modes. The inter setting, for instance, would be used for team communication, while liaison allowed one to transmit and receive over long ranges. Zooming out, it is hard not to appreciate the sheer amount of skill that went into designing, manufacturing and operating the B-17. And we've only just scratched the surface here in terms of detail. But now that we've at least been introduced to this complexity, we can ask, how did it actually hold up in the realities of war? In our next episode, we shall review the Flying Fortress in action. For now, you can join us on Patreon or YouTube Memberships to catch script previews and download our art. A big thanks to the current supporters and a shout out to the researchers, writers and artists for making this episode possible. We couldn't have done it without this team and this community. A big thanks again to Conflict of Nations for sponsoring this video. 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