Browning Aircraft Machine Gun Caliber .30 M2 | This Day in Aviation

Boeing Model 299, NX13372, photographed during its first flight, 28 July 1935. (The Boeing Company) — Boeing Model 299 X13372, photographed during its first flight, 28 July 1935. (The Boeing Company)

Boeing test pilot Les Tower. (Boeing) — 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)

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 NX13372, all engines running. — 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. (U.S. Air Force) — 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. (U.S. Air force) — 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.

Fortress Mark I, AN521 WP-K, of No. 90 Squadron RAF based at West Raynham, Norfolk, preparing for take off at Hatfield, Hertfordshire, during an inspection of newly-arrived American aircraft by the Chief of the Air Staff and the US Air Attache. (Photograph by Flight Lieutenant Bertrand John Henry Daventry, Royal Air Force/CH 2873, Imperial War Museum) — Boeing Fortress Mark I AN521, WP-K, (U.S.A.A.F. serial number 40-2052) of No. 90 Squadron R.A.F., based at West Raynham, Norfolk, preparing for take off at Hatfield, Hertfordshire, during an inspection of newly-arrived American aircraft by the Chief of the Air Staff and the U.S. Air Attache. Photograph by Flight Lieutenant Bertrand John Henry Daventry, Royal Air Force. © IWM (CH 2873)

8 July 1941: Three Royal Air Force Boeing Fortress Mk.I heavy bombers departed from their base at RAF Watton to attack Wilhelmshaven, Germany. This was a daylight bombing mission, with the airplanes flying at 30,000 feet (9,144 meters). One bomber diverted to a secondary target because of engine trouble, while the remaining two Fortresses continued to the primary target.

At the very high altitudes flown, the defensive heavy machine guns that gave the airplane its name froze due to the low temperatures and could not be fired. (In standard atmospheric conditions, the temperature at 30,000 feet would be -45 °C., or -49 °F.)

"Vertical aerial reconnaissance of Wilhelmshaven." © IWM (HU 91201) — “Vertical aerial reconnaissance of Wilhelmshaven.” © IWM (HU 91201)

All three aircraft returned safely to their base. The mission was completely ineffective, however.

This was the very first use of the Boeing B-17 Flying Fortress in combat.

Fortress B.I WP-F — Fortress B.I AN530, WP-F (U.S.A.A.F. B-17C 40-2066) (Royal Air Force)

The Boeing Model 299H, designated B-17C, was the second production variant ordered by the U.S. Army Air Corps. 38 were built by Boeing for the U.S. Army Air Corps, but 20 were transferred to Great Britain’s Royal Air Force, designated Fortress Mk.I. (Boeing Model 299T.) They were initially assigned to No. 90 Squadron, Bomber Command. (A 1941 book, War Wings: Fighting Airplanes of the American and British Air Forces, by David C. Cooke, Robert M. McBride & Company, New York, refers to the B-17C in British service as the “Seattle,” which is in keeping with the R.A.F.’s system of naming bombers after cities.)

Of the 20 Fortress Mk.I bombers, 8 were lost in combat or in accidents.

Boeing Fortress Mk.I AN529 U.S.A.A.F. B-17C 40-2065) at Heathfield, Scotland, after arrival from United States, May 1941. © Imperial War Museum E(MOS) 276

The Boeing B-17C/Fortress Mk.I was 67 feet, 10-9/16 inches (20.690 meters long with a wingspan of 103 feet, 9⅜ inches (31.633 meters) and the overall height was 15 feet, 4½ inches (4.686 meters). The B-17C had an empty weight of 30,900 pounds (14,016 kilograms). The maximum design gross weight was 47,500 pounds (21,546 kilograms).

The B-17C was powered by four air-cooled, supercharged, 1,823.129-cubic-inch-displacement (29.876 liters) Wright Cyclone G666A (R-1820-65)¹ nine-cylinder radial engines with a compression ratio of 6.70:1. The engines were equipped with remote General Electric turbochargers capable of 24,000 r.p.m. The R-1820-65 was rated at 1,000 horsepower at 2,300 r.p.m. at Sea Level, and 1,200 horsepower at 2,500 r.p.m. for takeoff. The engine could produce 1,380 horsepower at War Emergency Power. 100-octane aviation gasoline was required. 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 engine is 3 feet, 11.59 inches (1.209 meters) long and 4 feet, 7.12 inches (1.400 meters) in diameter. It weighs 1,315 pounds (596 kilograms).

Crew members of a No. 90 "RAF Fortress crew at RAF Polebrook July 19, 1941." (IWM CH 3090) — “RAF Fortress crew at RAF Polebrook July 19, 1941.” © IWM (CH 3090)

The B-17C had a maximum speed of 323 miles per hour (520 kilometers per hour) at 25,000 feet (7,620 meters). Its service ceiling was 37,000 feet (11,278 meters) and the maximum range was 3,400 miles (5,472 kilometers).

The Fortress Mk.I could carry 4,800 pounds (2,177 kilograms) of bombs in an internal bomb bay. Defensive armament consisted of one Browning AN-M2 .30-caliber air-cooled machine gun at the nose and four Browning AN-M2 .50-caliber heavy machine guns in dorsal, ventral and waist positions.

Fortress I AN528 (Getty Images/Three Lions) — Royal Air Force Fortress Mk.I AN528 (B-17C 40-2064) prior to being camouflaged. (Getty Images/Three Lions)

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28 July 1935

8 July 1941