A flight of Boeing B-17E Flying Fortress bombers forms up over England, 1942. “Yankee Doodle,” 41-9023, is just to the left of center. (U.S. Air Force)Brigadier General Ira C. Eaker (Margaret Bourke-White/LIFE)
17 August 1942: Mission No. 1. The United States VIII Bomber Command made its first heavy bomber attack on Nazi-occupied Europe when eighteen Boeing B-17E Flying Fortress four-engine bombers of the 97th Bombardment Group (Heavy), based at RAF Polebrook, Northamptonshire, England, headed for the railroad marshaling yards at Rouen-Sotteville, France. This was the largest and most active railroad yard in northern France.
The group began takeoffs at 1530 hours. It was escorted by several squadrons of Royal Air Force Supermarine Spitfire fighters.
While six B-17s flew along the French coast as a diversion, twelve bombers flew to Rouen and were over the target from 1739 to 1746. From an altitude of 23,000 feet (7,010 meters), they dropped 39,000 pounds (17,690 kilograms) of general purpose bombs.
Accuracy was good. One of the aim points, the locomotive shops, was destroyed by a direct hit. The overall results were moderate.
Rouen-Sotteville target assessment photograph. (U.S. Air Force)
All of the bombers returned to their base, with the first landing at 1900. Two B-17s had been damaged. American gunners claimed damage to one Luftwaffe airplane.
Brigadier General Ira C. Eaker commanded Mission No. 1 from this Boeing B-17E Flying Fortress, 41-9023, Yankee Doodle, shown here being serviced between missions. This bomber survived the War. (U.S. Air Force)
The raid was commanded by Brigadier General Ira C. Eaker aboard Yankee Doodle, B-17E 41-9023, leading the second flight of six B-17s. The 97th Bombardment Group Commander, Colonel Frank A. Armstrong, Jr., flew as the co-pilot of the lead ship, Butcher Shop, B-17E 41-2578, with pilot Major Paul W. Tibbets, Jr. Major Tibbets was in command of the 97th’s 340th Bombardment Squadron. (He would later command the 509th Composite Group and fly the B-29 Superfortress Enola Gay.)
Colonel Frank Alton Armstrong, Jr., Air Corps, United States Army, commanding the 97th Bombardment Group (Heavy), in the pilot’s position of a Boeing B-17E Flying Fortress. (Imperial War Museum)
The Boeing B-17E Flying Fortress was a major redesign. A new aft fuselage was used, incorporating larger vertical and horizontal stabilizers. A tail turret was added. A power-operated gun turret was added at dorsal and ventral positions.
The Boeing B-17E Flying Fortress was a four-engine heavy bomber operated by a flight crew of ten. It was 73 feet, 10 inches (22.504 meters) long with a wingspan of 103 feet, 9-3/8 inches (31.633 meters) and an overall height of 19 feet, 2 inch (5.842 meters). Its empty weight was 32,350 pounds (14,674 kilograms), 40,260 pounds (18,262 kilograms) gross weight, and the maximum takeoff weight was 53,000 pounds (24,040 kilograms).
Boeing B-17E Flying Fortress 41-2578, 97th Bombardment Group, photographed 17 August 1942. (Imperial War Museum)
The B-17E was powered by four air-cooled, supercharged, 1,823.129-cubic-inch-displacement (29.875 liters) Wright Cyclone G666A (R-1820-65) nine-cylinder radial engines with turbochargers, producing 1,200 horsepower at 2,500 r.p.m. for takeoff and 1,000 horsepower at 2,300 r.p.m. at Sea Level. The Cyclones turned three-bladed constant-speed Hamilton-Standard Hydromatic propellers with a diameter of 11 feet, 7 inches (3.835 meters) though a 0.5625:1 gear reduction. The R-1820-65 was 47.59 inches (1.209 meters) long and 55.12 inches (1.400 meters) in diameter. It weighed 1,315 pounds (596 kilograms). 8,422 of these engines were produced by Wright Aeronautical Division and its licensees between February 1940 and August 1942.
The B-17E had a cruise speed of 195 miles per hour (314 kilometers per hour). Its maximum speed was 318 miles per hour (512 kilometers per hour) at 25,000 feet (7,620 meters). The service ceiling was 36,600 feet (11,156 meters).
With a normal fuel load of 2,490 gallons (9,426 liters) the B-17E had a maximum range of 3,300 miles (5,311 kilometers). Carrying a 4,000 pound (1,814 kilogram) bomb load, the range was 2,000 miles (3,219 kilometers).
Boeing B-17E Flying Fortress 41-2578, the lead ship on the 17 August 1942 air raid on Rouen-Sotteville, France, flown by Major Paul W. Tibbets, photographed at RAF Bovingdon, 1943. By the end of the war, this airplane was the oldest, longest-serving B-17E in the USAAF. (Imperial War Museum)
The B-17E Flying Fortress was armed with one .30-caliber Browning M2 Aircraft Machine Gun and eight Browning AN-M2 .50-caliber machine guns. The .30 was mounted in the nose. Power turrets mounting two .50-caliber guns, each, were located at the dorsal and ventral positions. (The first 112 B-17Es were built with a remotely-operated turret in the belly position, sighted by a periscope. A manned ball turret replaced this.) Two machine guns were in a tail turret, and one on each side at the waist.
The maximum bomb load of the B-17E was 20,800 pounds (9,435 kilograms) over very short distances. Normally, 4,000–6,000 pounds (1,815–2,722 kilograms) were carried. The internal bomb bay could be loaded with a maximum of eight 1,000 pound (454 kilogram) or four 2,000 pound (907 kilogram) bombs.
The B-17 Flying Fortress first flew in 1935, and was in production from 1937 to 1945. 12,731 B-17s were built by Boeing. 512 of the total were B-17Es. The last one was completed 28 May 1942. Production shifted to the further-improved B-17F.
Boeing B-17E Flying Fortress 41-2509, flying over the Florida Keys, circa 1942. (Getty Images)
An American Airlines Boeing 707-023B Astrojet (720B) at Los Angeles International Airport, 26 December 1962. (Photograph courtesy of Jon Proctor)
15 August 1962: American Airlines’ Captain Eugene M. (“Gene”) Kruse set a National Aeronautic Association Class C-1 record for Speed Over a Commercial Air Route, East to West Transcontinental, when he flew a Boeing 720B Astrojet from New York to Los Angeles, 2,474 miles (3,981.5 kilometers), in 4 hours, 19 minutes, 15 seconds, at an average speed of 572.57 miles per hour (921.46 kilometers per hour). 56 years later, this record still stands.
The National Aeronautic Association has placed Captain Kruse’ record on its “Most Wanted” list: long-standing flight records that it would like to see challenged. Rules require that a new record exceed the old by at least a 1% margin. The performance needed to establish a new record would be 578.30 miles per hour (930.68 kilometers per hour).
The Boeing 720 was a variant of the Model 707, intended for short to medium range flights. It had 100 inches (2.54 meters) removed from the fuselage length and improvements to the wing, decreasing aerodynamic drag.
The Boeing 720 was operated by a flight crew of four and could carry up to 149 passengers. It was 136 feet, 2 inches (41.25 meters) long with a wingspan of 130 feet, 10 inches (39.90 meters) and overall height of 41 feet, 7 inches (12.65 meters). The airplane had an empty weight of 103,145 pounds (46,785 kilograms) and Maximum Takeoff Weight of 220,000 pounds (100,800 kilograms).
The Boeing 720 was powered by four Pratt & Whitney Turbo Wasp JT3C-7 turbojet engines, a civil variant of the military J57 series. The 720B was equipped with the more efficient P&W JT3D-1 turbofan engines. The JT3C-7 was a “two-spool” axial-flow engine with a 16-stage compressor (9 low- and 7 high-pressure stages), 8 combustion tubes, and a 3-stage turbine (1 high- and 2 low-pressure stages). It was rated at 12,030 pounds of thrust (53.512 kilonewtons) for takeoff. The JT3D-1 was a dual axial-flow turbofan engine, with a 2-stage fan section 13-stage compressor (6 low- and 7 high pressure stages), 8 combustion chambers and a 4-stage turbine (1 high- and 3 low-pressure stages). This engine was rated at 14,500 pounds of static thrust (64.499 kilonewtons) at Sea Level, and 17,000 pounds (75.620 kilonewtons), with water injection, for takeoff (2½ minute limit). Almost half of the engine’s thrust was produced by the fans. Maximum engine speed was 6,800 r.p.m. (N1) and 10,200 r.p.m. (N2). It was 11 feet, 4.64 inches (3.471 meters) long, 4 feet, 5.00 inches (1.346 meters) wide and 4 feet, 10.00 inches (1.422 meters) high. It weighed 4,165 pounds (1,889 kilograms). The JT3C could be converted to the JT3D configuration during overhaul.
The maximum cruise speed was 611 miles per hour (983 kilometers per hour) and maximum speed was 620 miles per hour (1,009 kilometers per hour). Range at at maximum payload was 4,370 miles (7,033 kilometers).
Boeing built 154 720 and 720B airliners from 1959 to 1967.
The last flight of a Boeing 720 was on 9 May 2012, when a 720B aircraft used by Pratt and Whitney Canada as a test aircraft was placed in the National Air Force Museum of Canada at Trenton, Ontario.
Silverplate Martin-Omaha B-29-45-MO Superfortress 44-86292, “Dimples 82,” at Tinian, Marshall Islands, August 1945. Note the “Circle Arrowhead” tail code. (U.S. Air Force)
6 August 1945: At 0245 hours, a four-engine, long range heavy bomber of the 509th Composite Group, United States Army Air Forces, took off from North Field on the island of Tinian in the Northern Mariana Islands, on the most secret combat mission of World War II.
Colonel Paul Warfield Tibbets, Jr., United States Army Air Corps, Commanding Officer, 509th Composite Group, and aircraft commander of the B-29 Superfortress, Enola Gay. (U.S. Air Force)
The Martin-Omaha B-29-45-MO Superfortress, 44-86292, under the command of Colonel Paul W. Tibbets, Jr., was carrying Bomb Unit L-11, the first nuclear weapon to be used during war. This was a 9,700-pound (4,400 kilogram) “gun type” fission bomb, the Mark I, code-named Little Boy. It contained 64 kilograms (141.1 pounds) of highly-enriched uranium. The bomb was 120 inches (3.048 meters) long with a diameter of 28 inches (0.711 meter). Although it was a very inefficient weapon, it was considered to be such reliable design that it had not been tested.
Code named “Little Boy,” the Mark I bomb unit L-11, prior to loading aboard Enola Gay, 5 August 1945. (U.S. Air Force)
On the morning before the mission, Colonel Tibbets had his mother’s name painted on the nose of the airplane: Enola Gay. He had personally selected this bomber, serial number 44-86292, while it was still on the assembly line at the Glenn L. Martin Company plant at Bellevue, Nebraska, 9 May 1945. The B-29 was accepted by the Army Air Corps on 15 May and flown to the 509th’s base at Wendover, Utah, by Captain Robert A. Lewis, a B-29 aircraft commander who would act as Tibbets’ co-pilot on the atomic bombing mission.
The B-29 Superfortress was designed by the Boeing Airplane Company as its Model 345. Produced in three major version, the B-29, B-29A and B-29B, it was built by Boeing at Wichita, Kansas and Redmond, Washington; by the Bell Aircraft Corporation at Marietta, Georgia; and the Glenn L. Martin Company at Fort Crook (now Offutt Air Force Base, Omaha, Nebraska. A total of 3,943 Superfortresses were built.
The B-29 was the most technologically advanced airplane built up to that time, and required an immense effort by American industry to produce.
The B-29 Superfortress was 99 feet, 0 inches (30.175 meters) long with a wingspan of 141 feet, 3 inches (43.053 meters) and an overall height of 27 feet, 9 inches (8.458 meters). The standard B-29 had an empty weight of 74,500 pounds (33,793 kilograms) and gross weight of 120,000 pounds (54.431 kilograms).
Enola Gay at Tinian, with crew members.
The Silverplate B-29s differed from the standard production bombers in many ways. They were approximately 6,000 pounds (2,722 kilograms) lighter. The bomber carried no armor. Additional fuel tanks were installed in the rear bomb bay. The bomb bay doors were operated by quick-acting pneumatic systems. The bomb release mechanism in the forward bomb bay was replaced by a single-point release as was used in special British Lancaster bombers. A weaponeer’s control station was added to the cockpit to monitor the special bomb systems.
Colonel Paul W. Tibbets, Jr., waves from the cockpit of the Silverplate Martin-Omaha B-29-45-MO Superfortress Enola Gay, 44-86292, just before starting engines at 02:27 a.m., 6 August 1945. (Sergeant Armen Shamlian, United States Army Air Forces. National Archives and Records Administration)
Enola Gay had four air-cooled, supercharged, 3,347.662-cubic-inch-displacement (54.858 liter) Wright Aeronautical Division R-3350-41 (Cyclone 18 787C18BA3) two-row 18-cylinder radial engines with direct fuel injection. The R-3350-41 had a compression ratio of 6.85:1 and required 100/130 aviation gasoline. It was rated at 2,000 horsepower at 2,400 r.p.m. at Sea Level, and 2,200 horsepower at 2,800 r.p.m, for take-off. The engines drove four-bladed Curtiss Electric reversible-pitch propellers with a diameter of 16 feet, 8 inches (5.080 meters), through a 0.35:1 gear reduction. The R-3350-41 was 6 feet, 2.26 inches (1.937 meters) long, 4 feet, 7.78 inches (1.417 meters) in diameter and weighed 2,725 pounds (1,236 kilograms).
With the exception of the tail gunner’s position, all defensive armament—four powered remotely operated gun turrets with ten .50-caliber machine guns—were deleted. Their remote sighting positions were also removed. Enola Gay carried 1,000 rounds of ammunition for each of the two remaining Browning AN-M2 .50-caliber machine guns in the tail.
With these changes, the Silverplate B-29s could fly higher and faster than a standard B-29, and the new engines were more reliable. Enola Gay had a cruising speed of 220 miles per hour (354 kilometers per hour) and a maximum speed of 365 miles per hour (587 kilometers per hour). Its service ceiling was 31,850 feet (9,708 meters) and its combat radius was 2,900 miles (4,667 kilometers).
XXI Bomber Command Target Chart for Hiroshima Area. (U.S. Strategic Bombing Survey)XXI Bomber Command Target Chart for Hiroshima. (U.S. Strategic Bombing Survey)
At 09:15:17 a.m., (mission time, 8:15 a.m., local), Enola Gay was at 31,000 feet (9,450 meters) over the Japanese city of Hiroshima on the island of Honshu, an industrial center with a population of about 340,000 people. The bombardier initiated the automatic release sequence and the the atomic bomb was dropped. It fell for 44.4 seconds and detonated at an altitude of 1,968 feet (600 meters), about 800 feet (244 meters) from the aiming point, the Aioi Bridge over the Ota River.
The mushroom cloud rises over Hiroshima, Japan, 2–3 minutes after detonation. Photographed 6,500 meters (4 miles) from hypocenter (Seizo Yamada)A mushroom cloud rises 20,000 feet (6,100 meters) over the devastated city of Hiroshima, Japan, 2–3 minutes after detonation, 6 August 1945, photographed from Yoshiura, looking southward, by Technical Sergeant George R. Caron, U.S. Army Air Corps, tail gunner of the B-29 Enola Gay, using a Fairchild Camera and Instrument Company K-20 aerial camera with a 6-3/8″ f/4.5, 4″ × 5″ film negative. (U.S. Air Force)Two-tier cloud 2–5 minutes after detonation, seen from Kaitaichi, 6 miles east of Hiroshima. Photographer unknown. (The Atlantic)Pyrocumulus cloud rising over Hiroshima. Photographer unknown. (Atomic Heritage Foundation)A pyrocumulus cloud from the firestorm spreads laterally as it reaches the upper atmosphere. (U.S. Air Force)Hiroshima photographed by a reconnaissance airplane several hours after the explosion. (U.S. Air Force)
Ground Zero, the point on the surface directly below the explosion, was the Shima Hospital. The overpressure is estimated to have been 4.5–6.7 tons per square meter. The two-story brick building was completely obliterated. Of the patients, technicians, nurses and doctors inside, nothing remained.
The entrance to Shima Hospital is all the remained following the detonation of the atomic bomb.
The resulting explosion was approximately equivalent in explosive force to the detonation of 16,000 tons (14,515 metric tons) of TNT (16 “kilotons”). An estimated 70,000 people were killed immediately, and another 70,000 were wounded. As many as 160,000 people may have died as a result of the atomic bombing by the end of 1945. More would follow over the next few years.
The shadow of one of the victims of the atomic bomb is etched onto the steps in front of a destroyed building.
An area of the city with a radius of 1 mile (1.6 kilometers) from the point of detonation (“hypocenter”) was totally destroyed, and combined with the fires that followed, 4.7 square miles (12.17 kilometers²) of the city were destroyed. 69% of all buildings in Hiroshima were completely destroyed and another 6% damaged.
Hisroshima photographed in March 1946. (National Archives)
As soon as the bomb was released, Colonel Tibbets turned his B-29 away to avoid the blast. It was just over 11 miles (17.7 kilometers) from the detonation point when the shock waves hit, but no damage resulted. The bomber was then flown back to Tinian, landing after an elapsed time of 12 hours, 13 minutes.
Col. Tibbets’ B-29, Enola Gay, 44-86292, landing at Tinian Island, 6 August 1945. Note: “Circle R” identification on tail. (U.S. Air Force)Martin-Omaha Silverplate B-29 Superfortress 44 86292, Enola Gay, taxis to its hardstand after returning to Tinian, 6 August 1945. (U.S. Air Force)
Enola Gay was placed in storage at Davis-Monthan Army Air Field, Tucson, Arizona, 26 July 1946, and was transferred to the Smithsonian Institution just over one month later, 30 August 1946. For decades it sat in storage at different locations around the country, but finally a total restoration was performed. Today, the B-29 is on display at the Steven F. Udvar-Hazy Center, National Air and Space Museum.
Martin-Omaha B-29-45-MO Superfortress 44-86292, Enola Gay, at the Steven F. Udvar-Hazy Center, Smithsonian Institution National Air and Space Museum. (Photo by Eric Long, National Air and Space Museum, Smithsonian Institution )
The speed-distance record-setting crew of the Boeing XB-15 experimental long range bomber, left to right: Major Caleb V. Haynes, U.S. Army Air Corps, with Captain William D. Old; Walter G. Bryte, Jr.; A.C. Brandt; Master Sergeant Adolph Cattarius; Technical Sergeant Daniel L. Spicer; Staff Sergeant James E. Sands. (FAI)
2 August 1939: The Boeing Model 294, designated by the U.S. Army Air Corps as the XB-15, serial number 35-277, flown by a crew led by Major Caleb Vance Haynes, set a Fédération Aéronautique Internationale (FAI) World Record for Speed Over a Closed Circuit of 5000 Kilometers With 2000 Kilogram Payload, when they flew the experimental long range heavy bomber a distance of 3,109 miles at an average speed of 267.67 kilometers per hour (166.32 miles per hour) while carrying a payload of 2,000 kilograms (4,409.25 pounds).¹
The other members of the XB-15 crew were Captain William D. Old, Walter G. Bryte, Jr., A.C. Brandt, Master Sergeant Adolph Cattarius, Staff Sergeant William J. Heldt, Technical Sergeant Daniel L. Spicer and Staff Sergeant James E. Sands.
The Boeing XB-15, 35-277, flies past the Wright Brothers National Memorial at the Kill Devil Hills, Kitty Hawk, North Carolina. (U.S. Air Force)
The Boeing Model 294, designated XB-15 by the Air Corps, was an experimental airplane designed to determine if a bomber with a 5,000 mile range was possible. It was designed at the same time as the Model 299 (XB-17), which had the advantage of lessons learned by the XB-15 design team. The XB-15 was larger and more complex than the XB-17 and took longer to complete. It first flew more than two years after the prototype B-17.
The Boeing Model 294 (XB-15) at Boeing Field, Seattle, Washington, circa 1937. (The Boeing Company)
Designers had planned to use an experimental 3,421.194-cubic-inch-displacement (56.063 liter) liquid-cooled, supercharged and turbosupercharged Allison V-3420 twenty-four cylinder, four-bank “double V” engine. It produced a maximum of 2,885 horsepower at 3,000 r.p.m. The engine was not available in time, however, and four air-cooled Pratt & Whitney R-1830 (Twin Wasp) engines were used instead. With one-third the horsepower, this substitution left the experimental bomber hopelessly underpowered as a combat aircraft. (The Douglas XB-19 was retrofitted with V-3420s in 1942, and re-designated XB-19A.)
Boeing XB-15 at NACA Langley Memorial Aeronautical Laboratory, 13 September 1938. (NASA)
The XB-15 was a very large four-engine mid-wing monoplane with retractable landing gear. It was of aluminum monocoque construction with fabric-covered flight control surfaces. The XB-15 had a ten-man crew which worked in shifts on long duration flights.
The prototype bomber was 87 feet, 7 inches (26.695 meters) long with a wingspan of 149 feet (45.415 meters) and overall height of 18 feet, 1 inch (5.512 meters). The airplane had an empty weight of 37,709 pounds (17,105 kilograms) and maximum takeoff weight of 70,706 pounds (32,072 kilograms)—later increased to 92,000 pounds (41,730 kilograms).
The XB-15’s wings used a symmetrical airfoil and were very highly tapered (4:1 from root to tip). They had an angle of incidence of 4½° and 4½° dihedral. The total area was 2,780 square feet (258.271 square meters). A contemporary aeronautical publication wrote, “The airfoil provides constant center of pressure, minimum profile drag with flaps up and high maximum lift with flaps down.” The XB-15’s wings were adapted by Boeing for the Model 314 Clipper flying boat.
Boeing XB-15 in flight. (U.S. Air Force)050406-F-1234P-053
As built, the XB-15 was equipped with four air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney R-1830-11 (Twin Wasp S1B3-G) two-row 14-cylinder radial engines with a compression ratio of 6.7:1. The R-1830-11 was rated at 850 horsepower at 2,450 r.p.m. and 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. They turned three-bladed controllable-pitch propellers through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).
The experimental airplane had a cruise speed of 152 miles per hour (245 kilometers per hour) at 6,000 feet (1,829 meters), and a maximum speed of 200 miles per hour ( kilometers per hour) at 5,000 feet (1,524 meters). The service ceiling was 18,900 feet (5,761 meters) and maximum range was 5,130 miles (8,256 kilometers).
The bomber could carry a maximum of 12,000 pounds (5,443 kilograms) of bombs in its internal bomb bay, and was armed with three .30-caliber and three .50-caliber machine guns for defense .
Only one XB-15 was built. During World War II it was converted to a transport and re-designated XC-105. In 1945 35-277 was stripped and abandoned at Albrook Field, Territory of the Canal Zone, Panama.
The Boeing XB-15 experimental long-range heavy bomber flies in formation with a Boeing YP-29 pursuit. (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 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.
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