Tag Archives: 20-mm Aircraft Automatic Gun AN-M2

21 September 1942

A Boeing XB-29 takes off from Boeing Field, Seattle, Washington. (SDASM)
Edmund T. ("Eddie") Allen
Edmund T. (“Eddie”) Allen

21 September 1942: At Boeing Field, Seattle, Washington, the Boeing Model 345, the first of three XB-29 prototypes, Air Corps serial number 41-002, took off on its first flight.

Edmund T. “Eddie” Allen, Director of Aerodynamics and Flight Research, was in command, with Al Reed, Chief of Flight Test and Chief Test Pilot, as co-pilot. They climbed to 6,000 feet (1,829 meters) and began testing the XB-29’s stability and control, control power and response, and stall characteristics.

The flight was uneventful. Landing after 1 hour, 15 minutes, Allen is supposed to have said, “She flew!”

Eddie Allen lean’s out of a cockpit window following the first taxi test of the XB-29. (Boeing)

The XB-29 was 98 feet, 2 inches (29.921 meters) long with a wing span of 141 feet, 3 inches (43.053 meters), and 27 feet, 9 inches (8.458 meters) high to the top of its vertical fin. The prototype bomber had a gross weight of 105,000 pounds (47,627 kilograms).

Boeing XB-29-BO, 41-002, the first XB-29 built. (U.S. Air Force)
Boeing XB-29-BO, 41-002, the first of three prototypes. (U.S. Air Force)

The prototype bomber was powered by four air-cooled, supercharged and fuel-injected 3,347.662-cubic-inch-displacement (54.858 liter) Wright Aeronautical Division Duplex-Cyclone 670C18H1 (R-3350-13) twin-row 18-cylinder radial engines with a compression ratio of 6.85:1. The R-3350-13 was rated at 2,000 horsepower at 2,400 r.p.m., and 2,200 horsepower at 2,800 r.p.m. for takeoff, burning 100-octane gasoline. These engines drove 17-foot-diameter (5.182 meters) three-bladed Hamilton Standard constant-speed propellers through a gear reduction of 0.35:1. The R-3350-13 was 76.26 inches (1.937 meters) long, 55.78 inches (1.417 meters) in diameter, and weighed 2,668 pounds (1,210 kilograms). Wright built 50 of these engines.

Boeing XB-29 41-002. (SDASM)

The XB-29 had a maximum speed of 368 miles per hour (592 kilometers per hour) and cruised at 255 miles per hour (410 kilometers per hour). Its service ceiling was 32,100 feet (9,784 meters).

The airplane was designed to carry 20,000 pounds (9,072 kilograms) of bombs. Though the prototypes were unarmed, the production B-29s were defended by 10 Browning AN-M2 .50-caliber machine guns in four remotely-operated power turrets, with 2 more .50-caliber machine guns and a single AN-M2 20mm autocannon in the tail.

Boeing XB-29 41-002. (SDASM)

The B-29 Superfortress was the most technologically advanced—and complex—aircraft of the War. It required the manufacturing capabilities of the entire nation to produce. Over 1,400,000 engineering man-hours had been required to design the prototypes.

The B-29 was manufactured by Boeing at Seattle and Renton, Washington, and at Wichita, Kansas; by the Glenn L. Martin Company at Omaha, Nebraska; and by Bell Aircraft Corporation, Marietta, Georgia. There were three XB-29 prototypes, 14 YB-29 pre-production test aircraft, 2,513 B-29, 1,119 B-29A, and 311 B-29B Superfortress aircraft. The bomber served during World War II and the Korean War and continued in active U.S. service until 1960.

The first prototype, 41-002, was scrapped in 1948.

Boeing B-29A-30-BN Superfortress 42-94106, circa 1945. (U.S. Air Force)
Boeing B-29A-30-BN Superfortress 42-94106, circa 1945. (U.S. Air Force)

© 2018, Bryan R. Swopes

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26 May 1942

Northrop Corporation XP-61 Black Widow at Hawthorne.
Northrop Corporation XP-61 prototype 41-19509 at Northrop Field, 1942. (U.S. Air Force)

26 May 1942: The prototype Northrop XP-61-NO Black Widow, 41-19509, made its first flight at Northrop Field, Hawthorne, California, with free-lance test pilot Vance Breese at the controls. (Breese had taken the North American Aviation NA-73X, prototype of the Mustang, for its first flight, 20 October 1940.)

Northrop XP-61 41-19509 taking off from Northrop Field. (U.S. Air Force)

The first American airplane designed specifically as a night fighter, the XP-61 was the same size as a medium bomber: 48 feet, 11.2 inches (14.915 meters) long with a wingspan of 66 feet (20.117 meters) and overall height of 14 feet, 8.2 inches (4.475 meters). The prototype was equipped with a mockup of the top turret. Its empty weight was 22,392 pounds (10,157 kilograms), gross weight of 25,150 pounds (11,408 kilograms) and maximum takeoff weight of 29,673 pounds (13,459 kilograms).

Northrop XP-61 41-19509 retracts its landing gear after takeoff. (U.S. Air Force)

The XP-61 was powered by two air-cooled, supercharged, 2,804.4-cubic-inch-displacement (45.956 liter) Pratt & Whitney Double Wasp SSB2-G (R-2800-10) two-row, 18-cylinder radial engines with a compression ratio of 6.65:1. The R-2800-10 had a Normal Power rating of 1,550 horsepower at 2,550 r.p.m. at 21,500 feet (6,553 meters), and 2,000 horsepower at 2,700 r.p.m. for takeoff, burning 100-octane gasoline. The R-2800-10 had a 2:1 gear reduction and drove four-bladed Curtiss Electric constant-speed propellers which had a 12 foot, 2 inch (3.708 meter) diameter. The R-2800-10 was 4 feet, 4.50 inches (1.334 meters) in diameter, 7 feet, 4.47 inches (2.247 meters) long, and weighed 2,480 pounds (1,125 kilograms), each.

The prototype Black Widow had a top speed of 370 miles per hour (595 kilometers per hour) at 29,900 feet (9,114 meters) and a service ceiling of 33,100 feet (10,089 meters). The maximum range was 1,450 miles (2,334 kilometers).

Prototype Northrop XP-61 Black Widow 41-19509 in camouflage. (U.S. Air Force)

The night fighter was crewed by a pilot, a gunner and a radar operator. A large Bell Laboratories-developed, Western Electric-built SCR-720 air search radar was mounted in the airplane’s nose. The gunner sat above and behind the pilot and the radar operator was in the rear fuselage.

SCR-720 Air Search Radar mounted in nose of a Northrop P-61 Black Widow night fighter. (NOAA)

The Black Widow was armed with four Browning AN-M2 .50-caliber machine guns in a remotely-operated upper turret, and four AN-M2 20 mm aircraft automatic cannons, grouped close together in the lower fuselage and aimed directly ahead. This was a superior arrangement to the convergent aiming required for guns mounted in the wings. The fire control system was similar to that used by the B-29 Superfortress. The guns could be fired by either the gunner or the radar operator.

Northrop P-61A-1-NO Black Widow 42-5507 in olive green camouflage. (U.S. Air Force)
Northrop P-61A-1-NO Black Widow 42-5507 in olive green camouflage. (U.S. Air Force)

The XP-61 was built with a center “gondola” for the crew, radar and weapons, with the engines outboard in a twin-boom configuration, similar the the Lockheed P-38 Lightning. The Black Widow did not use ailerons. Instead, it had spoilers mounted on the upper wing surface outboard of the engines. Roll control was achieved by raising a spoiler, decreasing lift on that wing and causing it to drop. A similar system was employed on the Boeing B-52 Stratofortress ten years later.

The P-61 got its nickname, Black Widow, from the glossy black paint scheme that scientists at the Massachusetts Institute of Technology (M.I.T.) had determined was the best camouflage for a night fighter. Over 700 P-61s were built, with 36 built as the F-15 photo reconnaissance variant. They served in both the Pacific and European Theaters during World War II, and were also used during the Korean War. After the war, the radar-equipped fighter was used for thunderstorm penetration research.

Northrop P-61C-1-NO Black Widow 43-8353 at the National Museum of the United States Air Force. (U.S. Air Force)
Northrop P-61C-1-NO Black Widow 43-8353 at the National Museum of the United States Air Force. (U.S. Air Force)
Northrop P-61C-1-NO Black Widow 43-8353 at the National Museum of the United States Air Force. (U.S. Air Force)

© 2018, Bryan R. Swopes

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18 March 1945

LaVerne Brown, Director of Flight Test, Douglas Aircraft Company, in the cockpit of the first XBT2D-1 Dauntless II prototype, Bu. No. 9085. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
LaVerne Ward Browne, Director of Flight Test, Douglas Aircraft Company, in the cockpit of the first XBT2D-1 Dauntless II prototype, Bu. No. 9085. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

18 March 1945: At the Naval Airplane Factory, El Segundo, California (at the southeast corner of Los Angeles Airport, now best known as LAX), Douglas Aircraft Company Director of Flight Test LaVerne Ward (“Brownie”) Browne took the prototype XBT2D-1 Dauntless II, Bu. No. 9085, for its first flight.

He later commented, “I wish I could tell of some dramatic incident that occurred. There wasn’t any. I just floated around up there for an hour and a half and brought her down. But I did do something that’s unprecedented, I believe, for a first trip. The airplane handled so well that I put it through rolls and Immelmanns to check it for maneuverability.”

The first prototype Douglas XBT2D-1 Dauntless II, Bu. No. 9085. In this photograph the airplane has a propeller spinner. (San Diego Air and Space Museum archive)
The first prototype Douglas XBT2D-1 Dauntless II, Bu. No. 9085. In this photograph the airplane has a propeller spinner. (Douglas Aircraft Company)

The XBT2D-1 would be ordered into production as the Douglas AD-1 Skyraider.

Designed by Douglas’ Chief Engineer, Edward Henry Heinemann, the XBT2D-1 was a single-place, single-engine attack bomber capable of operation from the U.S. Navy’s aircraft carriers. The prototype was 39 feet, 5 inches (12.014 meters) long with a wingspan of 50 feet, ¼ inch (15.246 meters) and overall height of 15 feet, 7½ inches (4.763 meters). The airplane had an empty weight of 10,093 pounds (4,578 kilograms) and maximum weight of 17,500 pounds (7,938 kilograms).

The first four XBT2D-1 prototypes were powered by an air-cooled, supercharged, direct-fuel-injected 3,347.662-cubic-inch-displacement (54.858 liter) Wright Aeronautical Division R3350-8 (Cyclone 18 779C18BB1) twin-row 18-cylinder radial engine rated at 2,100 horsepower at 2,400 r.p.m., and 2,400 horsepower at 2,600 r.p.m., for takeoff. The next 20 airplanes built utilized the R3350-24W (Cyclone 18 825C18BD1) which had a takeoff power rating of 2,500 horsepower at 2,900 r.p.m.

Test pilot Brown in teh cockpit of Douglas XBT2D-1 Dauntless II Bu. No. 9085 during a test flight. (Douglas Aircraft Company)
Test pilot LaVerne Brown in the cockpit of Douglas XBT2D-1 Dauntless II Bu. No. 9085 during a test flight. (Douglas Aircraft Company)

The XBT2D-1 had a maximum speed of 375 miles per hour (604 kilometers per hour) at 13,600 feet (4,145 meters) and normal cruise speed of 164 miles per hour (264 kilometers per hour).

The first XBT2D-1, Bu. No. 9085, was sent to NAS Patuxent River, Maryland for further testing. The second, 9086, went to NACA Ames at Moffet Field, California, where it underwent testing from 11 March 1946 to 4 September 1947..

The second prototype XBT2D-1, Bu. No. 9086, was tested at the NACA Ames Research Center, Moffet Field, California, from 11 March 1946 to 4 September 1947. (NASA)
The second prototype XBT2D-1, Bu. No. 9086, at the NACA Ames Research Center, Moffet Field, California, 18 June 1946. (NASA)

3,180 Skyraiders in 11 variants were built at the Douglas Aircraft Company’s El Segundo, California, plant from 1945 to 1957. The attack bomber was widely used during the Korean War and the Vietnam War. It was utilized for many purposes but is best known for its close support missions during combat rescue operations. After 1962, the AD-series aircraft still in service were redesignated A-1E through A-1J.

Douglas XBT2D-1 Dauntless II at Los Angeles Airport, circa 1945. (Douglas Aircraft Company via Tommy H. Thomason)

The most numerous Skyraider variant was the AD-6 (A-1H), of which 713 were produced by Douglas. The AD-6 was 38 feet, 10 inches (11.836 meters) long with a wingspan of 50 feet, 9 inches (15.469 meters) and overall height of 15 feet, 8¼ inches (4.782 meters). Its empty weight was 11,968 pounds (5,429 kilograms) and gross weight was 18,106 pounds (8,213 kilograms). The maximum takeoff weight (MTOW) for the AD-6 was 25,000 pounds (11,340 kilograms).

Douglas AD-4 Skyraider of VA-195 taking off from USS Princeton (CV-37) circa 1950–52 (U.S. Navy)
Douglas AD-4 Skyraider of VA-195 taking off from USS Princeton (CV-37) circa 1950–52 (U.S. Navy)

The Douglas AD-6 was powered by an air-cooled, supercharged, direct-fuel-injected, 3,347.662-cubic-inch-displacement (54.858 liter), Wright Aeronautical Division R-3350-26WA (Cyclone 18 836C18CA1) twin-row 18-cylinder radial engine, with water/alcohol injection. This engine has a compression ratio of 6.71:1. The R-3350-26W has a Normal Power rating of  2,300 horsepower at 2,600 r.p.m., and a Takeoff/Military Power rating of 2,700 horsepower at 2,900 r.p.m., using 115/145 aviation gasoline. The engine drives a four-bladed Aeroproducts constant-speed propeller with a diameter of 13 feet, 6 inch (4.115 meters) through a 0.4375:1 gear reduction. The engine is 4 feet, 7.62 inches (1.413 meters) in diameter and 6 feet, 6.81 inches (2.002 meters) long. It weighs 2,848 pounds (1,292 kilograms), dry.

The AD-6/A-1H Skyraider had a cruise speed of 198 miles per hour (319 kilometers per hour) and a maximum speed of 322 miles per hour (518 kilometers per hour). The ceiling was 29,400 feet (8,961 meters) and its combat radius carrying 2,000 pounds (907 kilograms) of ordnance was 275 miles (443 kilometers).

A U.S. Marine Corps Douglas AD-2 Skyraider of VMF-121 parked at airfield K-6, Pyongtaek, South Korea, 1952. The hard points under the wings are fully loaded with bombs.
A U.S. Marine Corps Douglas AD-4 Skyraider, Bu. No. 127874, of VMF-121 is parked at airfield K-6, Pyongtaek, South Korea, 1952. The hard points under the wings are fully loaded with bombs. The aircraft is painted overall glossy sea blue. (Navy Pilot Overseas)
Douglas AH-1H Skyraider 52-137593 (U.S. Air Force)
Douglas AH-1H Skyraider 52-137593 of the 602nd Special Operations Squadron. (U.S. Air Force)

The AD-6 Skyraider was armed with four 20mm AN-M2 autocannons, with two in each wing. The guns fired explosive projectiles with a muzzle velocity of 2,850 feet per second (869 meters per second), and had a rate of fire of 600–700 rounds per minute. The AD-6 could carry 8,000 pounds (3,629 kilograms) of bombs, rockets, gun pods and external fuel tanks from the 15 hard points and pylons under the wings and fuselage.

A Douglas A-1H Skyraider of the 6th Special Operations Squadron dive bombing a target during a close air support mission, Vietnam, 1968. (U.S. Air Force)
A Douglas A-1J Skyraider, 52-142016, of the 6th Special Operations Squadron dive bombing a target during a close air support mission, Vietnam, 1968. (U.S. Air Force)

Many United States Navy and Marine Corps Skyraiders were transferred to the U.S. Air Force. The Air Force retained the Navy’s Bureau of Aeronautics serial numbers (“Bu. No.”) but added two digits corresponding to the fiscal year in which each airplane was contracted. This resulted in serial numbers similar, though longer, than customary in the Air Force and Army numbering system.

The oldest Skyraider in existence is XBT2D-1 Bu. No. 9102. Formerly on display at NAS Oceana, Virginia Beach, Virginia, the airplane was transferred to The Intrepid Sea, Air & Space Museum in New York City for restoration and preservation.

This is the Douglas A-1H Skyraider flown by LCOL Jones, 1 September 1968. Though it was extensively damaged by anti-aircraft gunfire and the subsequent fire, 52-139738 was repaired and returned to service. On 22 September 1972, -738 was shot down over Laos. It was the last Skyraider shot down during the Vietnam War.
Douglas A-1H Skyraider 52-139738, 1st Special Operations Squadron. Lieutenant Colonel William A. Jones III, commanding the 602nd Special Operations Squadron, flew this airplane on 1 September 1968 during a Combat Search and Rescue mission for which he was awarded the Medal of Honor. On 22 September 1972, -738 was shot down over Laos. It was the last Skyraider shot down during the Vietnam War. (U.S. Air Force)

LaVerne Ward Browne was born at Orange, California, 9 December 1906. He was the third child of Edwin J. Brown, a farm worker, and Phebe Alice Proctor Brown. He studied law at the University of Southern California (USC).

“Mystery Plane” poster. (Monogram Pictures Corporation)

In 1928, Brown learned to fly at the Hancock College of Aeronautics, Santa Maria, California. He then worked as a pilot for Transcontinental and Western Airways, flying the Douglas DC-2. He was also commissioned as a second lieutenant in the United States Army Air Corps Reserve.

Browne married Miss Dorothy Leonore Bach at Los Angeles, California, 28 January 1926. They had a daughter, Barbara May Browne, born 6 December 1926, but later divorced. One 12 June 1933, Browne married Harriette Fitzgerald Dodson at Norfolk, Virginia.

From 1931 to 1941, under the pseudonym “John Trent,” Browne performed in sixteen Hollywood movies, including “I Wanted Wings,” with William Holden, Ray Milland and Veronica Lake. He played the character “Tailspin Tommy Tompkins” in four: “Danger Flight,” “Sky Patrol,” “Stunt Pilot,” and “Mystery Plane.”

Browne worked for Douglas Aircraft Company from 1942 to 1957. He died 12 May 1966 at Palos Verdes, California, at the age of 59 years.

“John Trent” (LaVerne Ward Browne) portrayed “Tailspin Tommy Tompkins” in four Hollywood movies. (Monogram Pictures Corporation via IMDb)

© 2017, Bryan R. Swopes

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