B-17F bombers flew over Pacific islands
In 1934, the international situation deteriorated rapidly. Japan had already begun invading northeast China a year earlier and withdrew from the League of Nations, followed by Germany. This greatly undermines any hope of disarmament. The U.S. Army Air Force reacted by launching Plan A based on a feasibility study conducted by the Wright Airfield Materials Division. It called for the creation of a bomber capable of carrying a capacity of 1 ton and traveling 8,045 kilometers. That is, the aircraft can take off from the continental United States and fly without landing to U.S. military bases in Panama, Hawaii or Alaska. The General Staff endorsed the development of such aircraft.
Boeing bid for the Type 299 aircraft. The project engineer was Emory, aided by Edward Wells.
The Boeing 299 was a prototype of the Bastion Air bomber, which was introduced on July 17, 1935. The prototype then made its maiden voyage on July 28, piloted by Boeing's chief test pilot, Leslie Thor.
This new aircraft is an all-metal lower monoplane with retractable landing gear. The fuselage has a smooth appearance, excellent performance in all aspects, and low operating costs. Its technological innovations include an ice removal device when the wings and tail are frozen.
The B-17 bombers were starting engines for testing, and ground crews had fire extinguishers ready
At 3:42 a.m. on August 20, 1935, Leslie Thor took off from the Seattle runway in a Type 299 and began a demonstration flight. He was accompanied by co-pilot Louis Werther, and as observers were Benton of Boeing and Henry Egger of Pratt Whitney. After 9 hours. The Type 299 plane landed at Wright Airport near Dayton, Ohio. The aircraft flew 3,379 km without landing, with an average speed of 373 km/h, using only 63 percent of the 3,000 horsepower. The average altitude flown is 3812 km. Mainly for automatic driving.
Their high-speed flight caused the plane to arrive 2 hours earlier than the team's officials had expected. The Air Force Team appointed Lieutenant Donald Putt as a project test pilot for the Boeing 299, and in a series of preliminary flight tests that followed, he reported that the aircraft exceeded all Army standards in terms of speed, climb speed, range, and load.
On March 1, 1937, the first YIB-17 aircraft (serial number 36-149) arrived at the 2nd Bombing Force at Langley Base, and the 12th aircraft was delivered to the base on August 5 of the same year. A Second Bombing Force aircraft, fully loaded with equipment and instruments, encountered a storm over The Langley base, and strong turbulence caused the aircraft to rotate and the pilots woke up and landed safely.
Inspections of the aircraft revealed that the aircraft was serviceable despite the curved wings and protruding rivets. In addition, test instruments show that the aircraft exceeds the maximum load capacity in all aspects within the allowable load range.
The 2nd Bombardment Force was the only heavy bombing unit of the U.S. Flying Force at the time, and the task of guiding the YIB-17 aircraft into full service fell to the shoulders of the Force Commander, Lieutenant Robert Oltz. In the months that followed, selected members of the 2nd Bombardment Force flew a total of 9,293 hours over sea and land in all weather conditions, with a total range of 2,896,200 kilometers, equivalent to 72 weeks of orbiting the earth at the equator. There were no serious accidents during the voyage.
In July and August 1939, during the celebration of the 30th anniversary of the U.S. Air Force, the B-17 broke several international and domestic records in terms of speed, load, and altitude. By this time the 2nd Bombardment Force had completed its tests. The letter "Y" is no longer used in bomber code names. At the same time, the B-17B production aircraft set a new record, flying from Seattle to New York in 9 hours and 14 minutes at an average speed of 426 kilometers per hour.
In addition to orders for 30 B-17Bs, Boeing has now received orders for 39 B-17C aircraft, and orders for variant B-17Ds are also under negotiation.
The B-17 bomber was fitted with three main fuel tanks on each of the inner flanks and nine main fuel tanks on each of the outer flanks. Ground crews are working on B-17 bombers
Boeing and the Air Force were engaged in a heated discussion behind the scenes about the price of each aircraft.
According to the agreement reached by both parties in the original contract, the unit price of each aircraft is $205,000. But air force forces insisted at this point that the price was too high. Even if Boeing told the War Department that it could cut the minimum price to $202,500 by eliminating some components, such as an outboard bomb rack, the entire B-17 program remained unresolved.
B-17 bomber production line in Seattle.
On September 1, 1939, Germany invaded Poland, pushing the world into war, and World War II broke out in full swing.
At that time, the United States could no longer continue its policy of isolation.
In the end, Boeing and the U.S. Air Force finally reached an agreement to save the heavy bomber program.
Boeing B-17F "Air Fortress" heavy bomber
All early models of the B-17 bomber, up to the B-17E with a tail gunner's cabin and later, were constructed of multiple nacelles and then connected with interlaced ring reinforcements and longitudinal reinforcements, including girders. The body is covered with a 24ST aluminum alloy coating. Fix with aluminum rivets. The thickness of the surface layer is different, and the load-bearing part is thicker.
To assist in mass production, the fuselage is manufactured in 4 parts, suspended and assembled, and integrated on the production line. The fuselage consists of 2 pilot's cabins and the navigator-bomber's cabin, which extends from the nose and is located below the cockpit; the middle part is the bomb storage compartment; and the rear and tail of the fuselage are rear.
Position of the machine guns on the back of early B-17 bombers
The early B-17 series (from the B-17B to the B-17D) was designed to be defensive rather than offensive, like other American bombers of the same period. That is, their main role in the war is to attack invading enemy forces that threaten the continental United States. Aircraft designers did not anticipate that the bombers would encounter onslaught from enemy fighters while defending. This line of thinking was reflected in the early combat aircraft armament. Up to the B-17D model. The aircraft is equipped with no more than 7 machine guns of mixed calibers of 0.30 inches and 0.50 inches.
The early "Air Fortress" was equipped with a turret in the middle of the body, and later the B-17 model was replaced by a simple window. The flexible handheld machine gun is equipped with shock absorbers on the mount to absorb recoil and vibration. Turret machine guns were equipped with control cams, while the machine guns in the middle of the fuselage were not so well designed. It is not uncommon for a mid-fuselage gunner to shoot his own plane in a fierce battle against enemy fighters.
Although the mid-fuselage gunners wore electric flying suits, their combat positions were the most uncomfortable among the B-17 bombers. Until the installation of glass windows in the middle of the B-17 bomber's fuselage. Strong hurricane-like winds often hit the fuselage, and the temperature drops as low as minus 40 degrees.
The rear machine gunners of the B-17 bombers had no backing protection, and when the German bombers adopted frontal offensive tactics, some bullets or shells penetrated the nose and penetrated the inside of the fuselage, shooting the tail machine gunners from behind, causing many machine gunners to die.
In the face of enemy fighter attacks, the defensive strength and armament must be strengthened, and the overall weight must be increased. The B-17G has a smaller range and lift limit than its predecessor, the B-17E.
The B-17E bomber weighs 15,075 kg on empty load, weighs 7 tons more than the earliest Type 299, is much faster (40% faster), and has a top speed of 512 km/h. The B-17E bomber was the first air fortress that could be described as an offensive type, playing a tactical bombing role.
The new B-17G bomber was mass-produced at the Boeing plant in Seattle
Later production of the B-17F bomber was equipped with a new bow lower turret, and the lower bow turret was commonly used in the next and final major variant of the B-17G bomber.
The B-17F bomber is also known as the "Memphis Beauty".
The first B-17G bomber was delivered on September 4, 1943, and the last B-17G bomber was delivered on April 13, 1945, less than a month before Germany surrendered.
The B-17 bomber was fitted with a very sophisticated device: the Norton bomb-throwing sight.
The bomb-dropping sight was very precise and stealthy, developed by Carl Norton and Captain Friedrich Entwesser.
Norton bomb-dropping sight
The main component of the front of the Norton bomb-throwing sight is a telescope fixed by a gyroscope and driven by a motor through which the bombardier observes the target. The sight is able to calculate the appropriate wind speed and altitude and give ballistic data. The bomb thrower uses the telescope's ruler to lock on to the target.
After the precise data of the bomber's movements in the air is fed into the Norton aiming computer, the bombardier can adjust the lateral movement of the aircraft through an automatic flight control device (this device is often referred to as an autopilot). As long as the sight locks on to the target, the aircraft remains in automatic control until it is dropped. Bomb dropping is also an automatic process, and the ballistic angle is calculated by the sight. After the bomb was dropped. The bombardier turns off the sight.
B-17 Air Fortress bomber
The first "Air Fortress" sent to the European theater was a B-17E, numbered 19085, which landed in Prestwick, Scotland, on July 1 of the same year. Subsequently, between 6 and 31 July 1942, the 97th Bombardment Group (340th, 341st, 342nd and 414th Bombing Squadrons) sent 38 B-17 bombers to British airfields.
On 17 August 1942, the 97th Bombardment Brigade was ordered by the United States to launch its first bombing attack from Britain, accompanied by a squadron of Spitfire fighters of the 11th Brigade of the RAF Fighter Force, targeting the railway shunting yard in Rouen. Attacked by 12 B-17 bombers and 6 more on the French coast. The bombing was clear and the results were so successful that only one B-17 bomber suffered minor anti-aircraft gun damage.
On 19 August, two of the 24 B-17 bombers dispatched bombed the German fighter airfield in Abbeville and returned safely.
After the summer of 1942, B-17 bombers were increasingly used in Britain, and by the end of the year, American daytime bombers had repeatedly attacked targets in France, the Netherlands, Belgium, And Rwanda during the voyages of fighter convoys.
A B-17 bomber formation of the 8th Air Force flew into the cloudy sky toward a German target.
For two years, from 1943 to 1944, the American B-17 bomber crew competed with German fighter pilots in the air, and the United States gradually gained the upper hand.
Production of the B-17 continued until the end of World War II in early 1945, when its bomber role began to be replaced by other new aircraft.
B-17 bombers flew a total of 291508 sorties on the European battlefield.