B-17 Flying Fortresses attack Schweinfurt, Germany, 1943. (U.S. Air Force)
14 October 1943: A large force of 8th Air Force heavy bombers and escorting fighters attack the ball bearing factories at Schweinfurt, Germany, for the second time. Five bombardment groups sent 291 B-17 Flying Fortress four-engine heavy bombers on the raid.
A B-17F Flying Fortress going down over Europe. The left outboard engine is on fire and the right wing has been shot off. There are ten men in this airplane. (U.S. Air Force)
60 B-17s were shot down by German fighters or anti-aircraft artillery (“flak”). Another 17 were so heavily damaged that they crashed on landing back at their bases, or were so severely damaged that they were beyond repair. 121 B-17s received lesser damage. 594 crewmen were listed as Missing In Action (presumably Killed In Action). 65 men were captured and held as Prisoners of War. Of the bombers that returned to England 5 crewmen were killed and 43 were wounded. B-17 gunners shot down 35 to 38 Messerschmitt Bf 109s and Focke-Wulk Fw 190s. Another 20 fighters were damaged.
A B-17G Flying Fortress with its bomb bay doors open. (U.S. Air Force)
Boeing B-17F Flying Fortresses of the 1st Bombardment Wing (Heavy) over Schweinfurt, Germany, 17 August 1943. (U.S. Air Force)
17 August 1943: Mission No. 84. One year after the Eighth Air Force first attacked occupied Europe with its B-17 Flying Fortress four-engine heavy bombers, a mass attack of 376 B-17s attacked the Messerschmitt Bf-109 factory at Regensburg, Germany, and the ball bearing factories at Schweinfurt.
Over Germany for over two hours without fighter escort, 60 bombers were shot down and as many as 95, though they made it to bases in Allied territory, were so badly damaged that they never flew again. 55 air crews (552 men) were listed as missing in action.
Of the 146 B-17s of the 4th Bombardment Wing which attacked Regensburg, 126 dropped their bombs, totaling 298.75 tons (271.02 Metric tons), destroying the factory and seriously slowing the production of the Messerschmitt Bf 109 fighter. After the attack, the 4th Bomb Wing headed for bases in North Africa. 122 B-17s landed there, half of them damaged.
The 1st Bombardment Wing (Heavy) sent 230 B-17s to Schweinfurt. Weather delays caused the planned diversion of two separate attacks to be unsuccessful. Cloud buildup over the Continent forced the bombers to fly at 17,000 feet (5,182 meters), nearly 10,000 feet (3,048 meters) lower than planned, increasing their vulnerability. Just 183 bombers made it to the target and dropped 424.3 tons (383.9 Metric tons) on the five factories in the target area. Then they headed back to their bases in England, under fighter attack most of the way. The 1st Bombardment Wing lost 36 bombers.
Though the raid did cut production of ball bearings as much as 34%, the losses were quickly made up from stockpiles. The two attacking forces succeeded in shooting down 25–27 German fighters.
A B-17 Flying Fortress, its right wing shot off and the left outboard engine on fire, goes down over Europe. (U.S. Air Force)
The flight crew of the FAI World Altitude Record-setting Boeing Y1B-17A. Left to right: Captain Pearl H. Robey, Captain Clarence S. Irvine and R. Swofford. (FAI)
1 August 1939: Captains Clarence S. Irvine and Pearl H. Robey, United States Army Air Corps, used the Boeing Y1B-17A Flying Fortress (Model 299F), serial number 37-369, to set a Fédération Aéronautique Internationale (FAI) World Record for Altitude with a 5,000 Kilogram Payload. The bomber climbed to 10,371 meters (34,026 feet) with a payload of 11,023 pounds.¹ ²
On the same day, Irvine and Robey flew the Y1B-17 from Dayton, Ohio to St. Jacob, Illinois, setting an FAI World Record for Speed Over 1,000 Kilometers with a 5,000 Kilogram Payload, averaging 417.46 kilometers per hour (259.40 miles per hour).³
The flight crew of the FAI World Speed Record-setting Boeing Y1B-17A. Left to Right: Captain Carl J. Crane, P.G. Miller, Captain Clarence S. Irvine and Captain Pearl H. Robey. (FAI)
The single Y1B-17A (Boeing Model 299F) was originally ordered as a static test article, but when that was determined to be unnecessary, it was used as an engine test aircraft. It was equipped with four 1,823.129-cubic-inch-displacement (29.875 liter) air-cooled, supercharged, Wright R-1820-51 (Cyclone G59) single-row nine-cylinder radial engines. Moss/General Electric turbo-superchargers were installed, initially on top of the wings, but were moved to the bottom of the engine nacelles.
Boeing Y1B-17A 37-369. (FAI)
The supercharged Wright R-1820-39 (Cyclone R-1820-G5) engines of the YB-17s were rated at 805 horsepower at 2,100 r.p.m., at Sea Level, 775 horsepower at 14,000 feet (4,267 meters), and 930 horsepower at 2,200 r.p.m., for take off. By contrast, the YB-17A’s R-1820-51 engines were rated at 800 horsepower at 2,100 r.p.m. at Sea Level, and 1,000 horsepower at 2,200 r.p.m. for take off. But the turbochargers allowed the engines to maintain their Sea Level power rating all the way to 25,000 feet (7,620 meters). Both the -39 and -51 engine had a 16:11 propeller gear reduction ratio. The R-1820-51 was 3 feet, 9.06 inches (1.145 meters) long, 4 feet, 6.12 inches (1.375 meters) in diameter, and weighed 1,200.50 pounds (544.54 kilograms). 259 were produced by Wright between September 1937 and February 1940.
Boeing Y1B-17A 37-369. (U.S. Air Force)
The turbo-superchargers installed on the YB-17A greatly improved the performance of the bomber, giving it a 55 mile per hour (89 kilometer per hour) increase in speed over the supercharged YB-17s, and increasing the bomber’s service ceiling by 7,000 feet (2,132 meters). The turbo-superchargers worked so well that they were standard on all following B-17 production models.
Boeing Y1B-17A 37-369. (U.S. Air Force photo)
The Boeing Y1B-17A was 68 feet, 9 inches (20.955 meters) long with a wingspan of 103 feet, 9–3/8 inches (31.633 meters) and height of 14 feet, 11–5/16 inches (4.363 meters). Its empty weight was 26,520 pounds (12,029 kilograms). The maximum gross weight was 45,650 pounds (20,707 kilograms)
The Model 299F had a cruise speed of 230 miles per hour (370 kilometers per hour), a maximum speed of 271 miles per hour (436 kilometers per hour) at Sea Level and 295 miles per hour (475 kilometers per hour) at 25,000 feet (7,620 meters). The service ceiling was 38,000 feet (11,582 meters). The maximum range was 3,600 miles (5,794 kilometers). Carrying a 4,000 pound (1,814 kilogram) load of bombs, the range was 2,400 miles (3,862 kilometers).
The Y1B-17A could carry eight 600 pound (272 kilogram) bombs in an internal bomb bay. Defensive armament consisted of five .30-caliber machine guns.
Following the engine tests, 37-369 was re-designated B-17A.
The Boeing Y1B-17A in flight near Mt. Rainier on 28 February 1938. (U.S. Air Force)
¹ FAI Record File Number 8318
² This record-setting flight was dramatized in the motion picture “Test Pilot,” (1938, Metro-Goldwyn-Mayer) with Clark Gable, Spencer Tracy and Myrna Loy. This movie is now 80 years old and has a melodramatic plot, but is well worth seeing for aviation history enthusiasts.
Boeing Model 299 X13372, photographed during its first flight, 28 July 1935. (The Boeing Company)Boeing’s Chief Test Pilot Leslie R. Tower.
28 July 1935, At Boeing Field, Seattle, Chief Test Pilot Leslie Ralph (“Les”) Tower and Louis Waite took off on the maiden flight of the Boeing Model 299, X13372,¹ a prototype four-engine long range heavy bomber. For approximately one-and-a-half hours, Tower flew back and forth between Tacoma and Fort Lewis. When he landed, he said, “It handles just like a little ship—a little bigger, of course.”
The Boeing Model 299 was a four-engine bomber operated by a crew of eight. It was designed to meet a U.S. Army Air Corps proposal for a multi-engine bomber that could carry a 2,000 pound (907 kilogram) bomb load a distance of 2,000 miles (3,219 kilometers) at a speed greater than 200 miles per hour (322 kilometers per hour). Design of the prototype began in June 1934 and construction was started 16 August 1934. The Air Corps designated it B-299, and later, XB-17. It did not carry a military serial number, being marked with civil experimental registration X13372.
The Boeing Model 299 with Mount Rainier. (U.S. Air Force)
The Model 299 was 68 feet, 9 inches (20.955 meters) long with a wingspan of 103 feet, 9–3/8 inches (31.633 meters) and height of 14 feet, 11–5/16 inches (4.554 meters). Its empty weight was 21,657 pounds (9,823 kilograms). The maximum gross weight was 38,053 pounds (17,261 kilograms).
The prototype was powered by four air-cooled, supercharged, 1,690.537-cubic-inch-displacement (27.703 liter) Pratt & Whitney Hornet S1E-G nine-cylinder radial engines with a compression ratio of 6.5:1. The S1E-G was rated at 750 horsepower at 2,250 r.p.m., and 875 horsepower at 2,300 r.p.m. for takeoff, using 87-octane gasoline. They turned 11 foot, 6 inch (3.505 meters) diameter, three-bladed, Hamilton Standard Hydromatic constant-speed propellers through a 3:2 gear reduction. The S1E-G was 4 feet, 1.38 inches (1.254 meters) long, 4 feet, 6.44 inches (1.383 meters) in diameter and weighed 1,064 pounds (483 kilograms)
Boeing Model 299. (U.S. Air Force)
In flight testing, the Model 299 had a cruise speed of 204 miles per hour (328 kilometers per hour) and a maximum speed of 236 miles per hour (380 kilometers per hour) at 10,000 feet (3,048 meters). The service ceiling was 24,620 feet (7,504.2 meters). Its maximum range was 3,101 miles (4,991 kilometers). Carrying a 2,573 pounds (1,167 kilograms) load of bombs, the range was 2,040 miles (3,283 kilometers).
Boeing 299 X13372, all engines running.
The XB-17 could carry eight 500 pound (226.8 kilogram) bombs in an internal bomb bay. Defensive armament consisted of five air-cooled Browning .30-caliber machine guns.
Nose turret of the Boeing Model 299, photographed 24 July 1935. (The Boeing Company)
X13372 was destroyed when it crashed on takeoff at Wright Field, Dayton, Ohio, 30 October 1935. An Army Air Corps pilot making his first familiarization flight neglected to remove the control locks. This incident led directly to the creation of the ”check list” which is used by all aircraft crew members.
Waist gun position of the Boeing 299. (The Boeing Company)
Designated XB-17 by the Army Air Corps, this airplane and the YB-17 pre-production models that followed would undergo several years of testing and improvement before entering production as the B-17 Flying Fortress, a legendary airplane of World War II. By the end of the war 12,731 B-17s had been built by Boeing, Douglas and Lockheed Vega.
Boeing Model 299 X13372, designated XB-17, at Wright Field, Ohio, 1935. (U.S. Air Force)
Leslie Ralph Tower was born at Sisseton, South Dakota, 21 January 1903. He was the first of three children of Ralph R. Tower, a farmer who would later serve as a state senator for Montana, and Mayme Amanda Johnson Tower, a Swedish immigrant.
Les Tower attended high school at Polson, Montana, graduating in 1922. He then attended the University of Washington, where he studied engineering. He was a member of the Radio Club.
Tower enlisted in the United States Army as an aviation cadet, training at Brooks and Kelly airfields in Texas. He then served with the 2nd Bombardment Squadron at Langley Field, Virginia.
In 1925 Tower started working for Boeing as a draftsman, but soon began test flying new airplanes, which included the B-9 bomber and the Model 247 commercial airliner. He also demonstrated and delivered Boeing airplanes around the world.
On 20 August 1935, Tower and Louis Wait flew the Model 299 from Seattle to Dayton, approximately 2,100 miles, in 9 hours, 3 minutes, averaging 233 miles per hour (375 kilometers per hour).
Les Tower was aboard the XB-17 as an observer during the 30 October flight. He saw that the control locks had not been released and tried to reach them, but was unable. In the fire that followed the crash, Tower suffered severe burns to his face, right arm and both legs.
Leslie Ralph Tower died of his injuries 19 November 1935 at Miami Valley Hospital in Dayton. His remains were transported by train, escorted by Army airplanes, and were buried at Lakeview Cemetery, Polson, Montana.
¹ At that time, experimental and restricted category aircraft were prohibited from displaying the letter “N” at the beginning of their registration mark.
The Boeing 299 is rolled out for the first time, 16 July 1935. (Boeing photograph via Seattle Post-Intelligencer)
16 July 1935: Just over a year after design began, the Boeing Model 299, X13372,¹ a prototype four engine long range heavy bomber, was rolled out of its hangar at Boeing Field, Seattle, Washington for the first time. The largest land airplane built up to that time, it seemed to have defensive machine guns aimed in every direction. A Seattle Times reporter, Roland Smith, wrote that it was a “flying fortress.” Boeing quickly copyrighted the name.
After several years of testing, the Model 299 went into production as the B-17 Flying Fortress. By the end of World War II, 12,731 B-17 Flying Fortresses had been built by Boeing, Douglas and Lockheed Vega.
Rollout of the Boeing Model 299, X13372, prototype XB-17. (Museum of Science and Industry via Seattle Post-Intelligencer)
The Boeing Model 299 was a four-engine bomber operated by a crew of eight. It was designed to meet a U.S. Army Air Corps proposal for a multi-engine bomber that could carry a 2,000 pound (907 kilogram) bomb load a distance of 2,000 miles (3,219 kilometers) at a speed greater than 200 miles per hour (322 kilometers per hour). Design of the prototype began in June 1934 and construction was started 16 August 1934. The Air Corps designated it B-299, and later, XB-17. It did not carry a military serial number, being marked with civil registration NX13372.
The Model 299 was 68 feet, 9 inches (20.955 meters) long with a wingspan of 103 feet, 9–3/8 inches (31.633 meters) and height of 14 feet, 11–5/16 inches (4.554 meters). Its empty weight was 21,657 pounds (9,823 kilograms). The maximum gross weight was 38,053 pounds (17,261 kilograms).
The prototype was powered by four air-cooled, supercharged, 1,690.537-cubic-inch-displacement (27.703 liter) Pratt & Whitney Hornet S1E-G nine-cylinder radial engines with a compression ratio of 6.5:1. The S1E-G was rated at 750 horsepower at 2,250 r.p.m., and 875 horsepower at 2,300 r.p.m. for takeoff, using 87-octane gasoline. They turned 11 foot, 6 inch (3.505 meters) diameter, three-bladed Hamilton Standard Hydromatic constant-speed propellers through a 3:2 gear reduction. The S1E-G was 4 feet, 1.38 inches (1.254 meters) long, 4 feet, 6.44 inches (1.383 meters) in diameter and weighed 1,064 pounds (483 kilograms)
Cockpit of the Boeing Model 299. (Boeing)
In flight testing, the Model 299 had a cruise speed of 204 miles per hour (328 kilometers per hour) and a maximum speed of 236 miles per hour (380 kilometers per hour) at 10,000 feet (3,048 meters). The service ceiling was 24,620 feet (7,504.2 meters). The maximum range was 3,101 miles (4,991 kilometers). Carrying a 2,573 pounds (1,167 kilograms) load of bombs, the range was 2,040 miles (3,283 kilometers).
Boeing XB-17 (Model 299) bombers and front gunners compartment. (U.S. Air Force photo) 060706-F-1234S-007Nose turret of the Boeing Model 299, with .50-caliber machine gun, photographed 24 July 1935. (Boeing 8195)Bomb sight position., 9 August 1935. (Boeing 8227-B)
The XB-17 could carry eight 500 pound (227 kilogram) bombs in an internal bomb bay. Defensive armament consisted of five air-cooled .30-caliber or .50-caliber Browning machine guns.
Starboard waist gunnner’s position of the Boeing 299. (Boeing)Starboard waist gunners position, with Browning M2 .50-caliber machine gun and ammunition canisters. (Boeing)
NX13372 was destroyed when it crashed on takeoff at Wright Field, Dayton, Ohio, 30 October 1935. An Army Air Corps pilot making his first familiarization flight neglected to remove the control locks. This incident led directly to the creation of the “check list” which today is used by all aircraft crew members.
Boeing Model 299, left quarter, at Boeing Field, south of Seattle, Washington,August 1935. (Boeing)Boeing Model 299, X13372, the prototype XB-17, at Wright Field, Ohio. (U.S. Air Force)Boeing Model 299, left profile, at Boeing Field, 13 August 1935. (Boeing 8234-B)Boeing Model 299 X13372, designated XB-17, at Wright Field, Ohio, 1935. (U.S. Air Force)Boeing 299 X13372, all engines running.
¹ At that time, experimental and restricted category aircraft were prohibited from displaying the letter “N” at the beginning of their registration mark.
