Tag Archives: Flying Wing

5 June 1948

A Northrop YB-49 over Muroc Air Force Base, 1948. (U.S. Air Force)

5 June 1948: Flying at 40,000 feet (12,192 meters), north of Muroc Air Force Base, California, the second Northrop YB-49 “flying wing,” serial number 42-102368, was undergoing stall recovery performance testing with a crew of five aboard. The pilot was Major Daniel A. Forbes, Jr., United States Air Force, and the co-pilot was Captain Glen W. Edwards.

The aircraft suffered a catastrophic structural failure with the outer wing panels tearing off. The experimental airplane crashed approximately 10 miles (16 kilometers) east of the small desert town of Mojave. The entire crew, which included 1st Lieutenant Edward L. Swindell, flight engineer, and civilian engineers Charles H. LaFountain and Clare C. Lesser, were killed.

The YB-49 was an experimental jet engine-powered bomber, modified from a propeller-driven Northrop XB-35. It was hoped that the all-wing design would result in a highly efficient airplane because of its very low drag characteristics. However, the design could be unstable under various flight conditions.

A few months after the crash, the first YB-49 was destroyed in a taxiing accident and the project cancelled. It would be 41 years before the concept would be successful with the Northrop B-2 Spirit.

Northrop YB-49 42-102367. (U.S. Air Force)

42-102367 had been converted from the second YB-35 pre-production test aircraft. The original Flying Wing’s four Pratt & Whitney Wasp Major (R-4360-21) radial engines were replaced by eight Allison J35-A-15 turbojet engines and several aerodynamic improvements were made. The change to jet power  increased the airplane’s speed by about 100 miles per hour (161 kilometers per hour) and significantly reduced the vibrations caused by the reciprocating engines, drive shafts and counter-rotating propellers.

The YB-49 was a very unusual configuration for an aircraft of that time. There was no fuselage or tail control surfaces. The crew compartment, engines, fuel, landing gear and armament was contained within the wing. Air intakes for the turbojet engines were placed in the leading edge of the wing. The exhaust nozzles were at the trailing edge. Four small vertical fins for improved yaw stability were also at the trailing edge.

The fins were likely too small. Test pilots complained about the airplane’s instability, which made it difficult to maintain course or altitude. A stability augmentation system was required.

Northrop YB-49 (U. S. Air Force)

The YB-49 had a length of 53 feet, 1 inch (16.180 meters), wingspan of 172 feet, 0 inches (52.426 meters) and overall height of 15 feet, 2 inches (4.623 meters). It weighed 88,442 pounds (40,117 kilograms) empty, and its maximum takeoff weight was 193,938 pounds (87,969 kilograms).

The Wing defined the airplane. It had an aspect ratio of 7.4:1. The wing’s root chord was 37 feet, 6 inches (11.430 meters). The wing was 7 feet, 1.5 inches (2.172 meters) thick at the root. The tip chord was 9 feet, 4 inches (2.844 meters). There was 0° angle of incidence at the root, -4° at the wing tips, and 0° 53′ dihedral. The leading edge was swept aft 26° 57′ 48″, and the trailing edge, 10° 15′ 22″. The wing’s total area was 4,000 square feet (371.6 square meters).

Northrop YB-49

The YB-49 was powered by eight General Electric-designed, Allison Engine Company-built J35-A-15 engines. The J35 was a single-spool, axial-flow turbojet engine with an 11-stage compressor section and single-stage turbine. The J35-A-15 was rated at 3,270 pounds of thrust (14.55 kilonewtons) at 7,400 r.p.m., Normal Power, and a Maximum (Military Power) rating of 3,750 pounds of thrust (16.68 kilonewtons) at 7,700 r.p.m. The engine was 14 feet, 0.0 inches (4.267 meters) long, 3 feet, 4.0 inches (1.016 meters) in diameter and weighed 2,400 pounds (1,089 kilograms).

Cruise speed for the YB-49 was 429 miles per hour (690 kilometers per hour). Its maximum speed 499 miles per hour (802 kilometers per hour) at 18,000 feet (5,486 meters) was restricted by Mach number. The airplane could climb from Sea Level to 30,000 feet (9,144 meters) in 21.0 minutes. It had a service ceiling of 49,700 feet (15,149 meters). The YB-49 had a combat radius of 1,611 miles (2,593 kilometers) at 420 miles per hour (676 kilometers per hour), carrying a 10,000 pound (4,536 kilogram) bomb load.

The YB-49 had no defensive armament. It could carry a maximum bomb load of 16,000 pounds (7,257 kilogram) in its internal bomb bay. (Turbulence resulting from open bomb bays significantly decreased bombing accuracy.)

Only two Northrop YB-49s were built. They were tested by Northrop and the Air Force for nearly two years. Although an additional nine YB-35s were ordered converted, the B-49 was not placed into production.

Northrop YB-49.
Daniel H, Forbes, Jr., 1940

Daniel Hugh Forbes, Jr., was born at Carbondale, Kansas, 20 June 1920. He was the son of Daniel Hugh Forbes, a farmer, and Hattie Rundle Forbes. He attended North High School in Wichita Kansas, and then the Kansas State College at Manhattan, Kansas,

Maj. Daniel Forbes, Jr., USAF

Daniel Forbes enlisted in the United States Army as an aviation cadet at Fort Riley, Kansas, 23 May 1941. On 9 January 1942, he was commissioned a second lieutenant, Air Reserve. Forbes was promoted to the rank of 1st lieutenant, Army of the United States, 25 August 1942, and to captain, A.U.S., 15 August 1944. On 4 October 1945, he was promoted to major, A.U.S.

Major Forbes married Mrs. Edward C. Winkle (née Hazel Marie Moog), 11 March 1948. Her first husband, a 1st lieutenant assigned to the 314th Infantry Regiment, 79th Infantry Division, was killed in action in France, 1 October 1944. Less than three months later, Mrs. Hughes was a widow again.

Major Daniel Hugh Forbes, Jr., Air Corps, United States Army.

Glen Walter Edwards was born at Medicine Hat, Alberta, Canada, 5 March 1916, the second son of Claude Gustin Edwards, a real estate salesman, and Mary Elizabeth Briggeman Edwards. The family immigrated to the United States in August 1923 and settled near Lincoln, California. He attended Lincoln High School, where he was a member of the Spanish Club and worked on the school newspaper, “El Eco.” He graduated in 1936.

Lt. Glen W. Edwards

Edwards attended Placer Junior College, Auburn, California, before transferring to the University of California, Berkeley. He graduated in 1941 with a Bachelor of Arts (A.B.) degree, and then enlisted in the United States Army as an aviation cadet, 16 July 1941.

Following pilot training, Edwards was commissioned as a second lieutenant, Air Reserve, 6 February 1942. He was promoted to 1st lieutenant, Army of the United States, 16 September 1942. Lieutenant Edwards flew 50 combat missions in the Douglas A-20 Havoc light bomber with the 86th Bombardment Squadron (Light), 47th Bomb Group, in North Africa and fought at the Battle of the Kasserine Pass, 19–24 February 1943. He was next promoted to captain, 28 April 1943. He also flew during the invasion of Sicily, in late 1943.

Two U.S. Army Air Force Douglas A-20B-DL Havoc light bombers, 41-3014 and 41-3134, in Tunisia, 1943. (U.S. Air Force)

Edwards returned to the United States and was assigned to the Pilot Standardization Board, but was then sent to train as a test pilot at Wright Field. Captain Edwards was assigned as a test pilot in 1944 and tested the Northrop XB-35 and Convair XB-36.After World War II came to an end the U.S. Army and Air Corps were demobilized to 1/16 of their peak levels (from 8,200,000 to 554,000). Edwards was retained but reverted to the rank of 1st lieutenant. He had been awarded the Distinguished Flying Cross and the Air Medal with three oak leaf clusters (four awards). He was transferred to the United States Air Force after it was established as a separate service, 18 September 1947.

Glen Edwards was recommended to fly the Bell X-1 rocket plane, but when that assignment went to Chuck Yeager, Edwards was sent to Princeton University, Princeton, New Jersey, to study aeronautical engineering. He earned a masters degree in engineering (M.S.E.) in 1947.

Captain Glen Walter Edwards, Air Corps, United States Army.

Following the crash of the YB-49, Topeka Air Force Base in Kansas was renamed Forbes Air Force Base. Muroc Air Force Base was renamed Edwards Air Force Base in honor of Captain Edwards.

Captains Edwards’ remains were buried at the Lincoln Cemetery, Lincoln, California.

Edwards Air Force Base, California, looking northeast, photographed in 2007. (U.S. Air Force)

Edward Lee Swindell was born at Currituck, North Carolina, 22 April 1916. He was the sun of Rudolph Bridgman Swindell, a machinist’s helper at the Portsmouth Navy Yard, and Eula Belle Williams Swindell.

Edward L. Swindell married Miss Edna Irene Hayman, 2 January 1942 at South Mills, North Carolina.

Swindell enlisted in the U.S. Army at Camp Lee, Virginia, 17 March 1942. He was 5 feet, 9 inches (1.75 meters) tall and weighed 156 pounds (70.7 kilograms).

Lieutenant Swindell’s remains were buried at the Forest Lawn Cemetery, Norfolk, Virginia.

Charles H. LaFountain was born 12 June 1925 in New York. He was the son of Leo L. LaFountain and Gladys Ethel Taylor LaFountain. He had served in the United States Navy and was a civilian employee of the Air Force. His remains were buried at the Lake Luzerne Cemetery, Lake Luzerne, New York.

Clare C. Lesser was born 27 June 1925 at Joliet, Illinois. He was the fifth of five children of Henry J. Leser, a worker at a wire mile, and Alvina Leser. Leser served as an ensign in the United States Naval Reserve. Like LaFountain, he was also a civilian employee of the Air Force. His remains were buried at St. John’s Cemetery, Joliet, Illinois.

© 2018, Bryan R. Swopes

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30 May 1949

John Oliver Lancaster, DFC. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)
John Oliver Lancaster, D.F.C. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

30 May 1949: While testing a radical “flying wing” aircraft, the Rolls-Royce Nene-powered Armstrong Whitworth A.W.52, TS363, test pilot John Oliver (“Jo”) Lancaster, D.F.C., encountered severe pitch oscillations in a 320 mile per hour (515 kilometer per hour) dive. Lancaster feared the aircraft would disintegrate.

In the very first use of the Martin-Baker Mk1 ejection seat in an actual emergency, Lancaster fired the seat and was safely thrown clear of the aircraft. He parachuted to safety and was uninjured. The aircraft was destroyed.

Bernard I. Lynch, B.E.M., seated in the cockpit, with John O. Lancaster, D.F.C. (Photograph courtesy of Neil Corbett, Test & Research Pilots, Flight Test Engineers)

The Martin-Baker MK1 was developed by Bernard Ignatius (“Benny”) Lynch, B.E.M., a ground fitter for Martin-Baker Aircraft Co., Ltd., who tested it himself, ejecting from a test aircraft at 420 miles per hour (676 kilometers per hour) and 12,000 feet (3,658 meters). He eventually made more than 30 ejections. Lynch was awarded the British Empire Medal in the King’s 1948 New Year Honours.

The seat was launched with a two cartridge ejection gun, with an initial velocity of 60 feet per second (18.3 meters per second). After rising 24 feet (7.3 meters), a static line fired a drogue gun, deploying a 24-inch (0.61 meter) drogue parachute to stabilize the seat. The static line also actuated the seat’s oxygen supply. The pilot manually released himself from the seat, and opened his parachute by pulling the rip cord.

Martin-Baker Mk1 ejection seat (Martin-Baker)
Martin-Baker Mk1 ejection seat. The parachute is an Irvin I 24. (Martin-Baker)

As of 29 May 2018, 7,567 airmen worldwide have been saved by Martin-Baker ejection seats. 69 of these were with the Mk1.

Armstong Whitworth A.W. 52, TS363
Armstrong Whitworth AW.52, TS363

The Armstrong Whitworth A.W.52 was an all-metal, experimental two-place, twin engine, tailless “flying wing” airplane with retractable tricycle landing gear. The concept was that of an air mail aircraft. The cockpit was pressurized and offset to the left of the aircraft centerline. The two turbojet engines are in nacelles positioned almost entirely within the wing. The A.W.52 was 37 feet, 4 inches (11.354 meters) long with a wingspan of 90 feet (27.4 meters) and height of 14 feet, 4 inches (4.343 meters).

The wings were swept in two sections. From the fuselage to just outboard of the engines, the leading edges were swept to 17° 34′. From that point, called “the knuckle” in contemporary descriptions, the sweep increased to 34° 6′ to the wing tips. (A line from the ¼-chord points at the wing root and tip gave a sweep of 24¾°.) The inner wing had no dihedral, and the outer wing had 1° dihdreal. The wing incorporated a -5° twist between the root and tip. The total wing area was 1,314 square feet (122.1 square meters). Vertical fins and rudders are attached at the wing tips.

The airplane incorporated boundary layer control to delay the wing stalling in the area of the ailerons. It also used engine heat for deicing,

The A.W.52 had a empty weight of 19,662 pounds (9,055 kilograms) total weight of 32,700 pounds (14,832 kilograms).

The A.W.52 was powered by two Rolls-Royce RB.41 Nene Mk.I engines. The Nene was a single-shaft turbojet developed from the RB.40 Derwent. It had first been run in October 1944. The Nene was considerably larger than the Derwent and produced nearly double the thrust. It had a single-stage centrifugal-flow compressor and single-stage axial-flow turbine. It was rated at 5,000 pounds of thrust (22.24 kilonewtons) at 12,400 r.p.m. for takeoff. The second A.W.52 prototype, TS368, used two Derwent engines.

The A.W.52 had a maximum speed at Sea Level of 500 miles per hour (805 kilometers per hour) and 480 miles per hour (772 meters) at 36,000 feet (10,973 meters). Its maximum range was 1,500 miles (2,414 kilometers), flying 330 miles per hour (531 kilometers per hour) at 36,000 feet (10,973 meters).

Sir W. G. Armstrong Whitworth Aircraft Limited (AWA) advertisement from FLIGHT, 14 January 1948. (Aviation Ancestry)

© 2018, Bryan R. Swopes

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21 October 1947

Northrop YB-49 42-102367 takes off from Northrop Field, Hawthorne, California. (U.S. Air Force)
Northrop YB-49 42-102367 takes off from Northrop Field, Hawthorne, California, 21 October 1947. (U.S. Air Force)

21 October 1947: At Northrop Field, Hawthorne, California, Northrop Corporation Chief Test Pilot Max R. Stanley took off in the first YB-49, 42-102367, and flew it to Muroc Air Force Base for flight testing.

42-102367 had been converted from the second YB-35 pre-production test aircraft. The original Flying Wing’s four Pratt & Whitney Wasp Major (R-4360-21) radial engines were replaced by turbojet engines and several aerodynamic improvements were made.

Chief Test Pilot Max R. Stanley. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

The YB-49 was a very unusual configuration for an aircraft of that time. There was no fuselage or tail control surfaces. The crew compartment, engines, fuel, landing gear and armament were contained within the wing. Air intakes for the turbojet engines were placed in the leading edge and the exhaust nozzles were at the trailing edge. Four small vertical fins for improved yaw stability were also at the trailing edge.

Northrop YB-49 42-102367. (U.S. Air Force)
Northrop YB-49 42-102367 at Northrop Field, Hawthorne, California. (U.S. Air Force)

The YB-49 had a length of 53 feet, 1 inch (16.180 meters), wingspan of 172 feet (52.426 meters) and overall height of 15 feet, 2 inches (4.623 meters). It weighed 88,442 pounds (40,117 kilograms) empty and its Maximum Takeoff Weight (MTOW) was 193,938 pounds (87,969 kilograms).

The Wing defined the airplane. The leading edge was swept aft 26° 57′ 48″, and the trailing edge, 10° 15′ 22″. The wing’s total area was 4,000 square feet (371.6 square meters). It had an aspect ratio of 7.4:1. At the root, the chord was 37 feet, 6 inches (11.430 meters), tapering to 9 feet, 4 inches (2.844 meters) at the tip. There was 0° angle of incidence at the root, -4° at the wing tips, and 0° 53′ dihedral.

The YB-49 was powered by eight General Electric-designed, Allison Engine Company-built J35-A-5 engines. (This same engine variant was used in the North American Aviation XP-86, replacing its original Chevrolet-built J35-C-3.) The engines were later upgraded to J35-A-15s. The J35 was a single-spool, axial-flow turbojet engine with an 11-stage compressor and single-stage turbine. The J35-A-15 had a Normal Power rating of 3,270 pounds of thrust (14.546 kilonewtons) at 7,400 r.p.m. The Military Power rating was 3,750 pounds (16.681 kilonewtons) at 7,700 r.p.m. The engine was 14 feet, 0.0 inches (4.267 meters) long, 3 feet, 4.0 inches (1.016 meters) in diameter and weighed 2,400 pounds (1,089 kilograms).

During testing the YB-49 reached a maximum speed of 428 knots (493 miles per hour/793 kilometers per hour) at 20,800 feet (6,340 meters). Cruise speed was 365 knots (429 miles per hour/690 kilometers per hour). The airplane had a service ceiling of 49,700 feet (15,149 meters). The YB-49 had a maximum fuel capacity of 14,542 gallons (55,047 liters) of JP-1 jet fuel. Its combat radius was 1,403 nautical miles (1,615 statute miles/2,598 kilometers).

The maximum bomb load of the YB-49 was 16,000 pounds (7,257 kilograms), though the actual number of bombs was limited by the volume of the bomb bay and the capacity of each bomb type. While the YB-35 Flying Wing was planned for multiple machine gun turrets, the YB-49 carried no defensive armament.

Northrop YB-49 42-102367 takes off from Northrop Field, Hawthorne California. Note teh crowds of onlookers and residential housing along W. 120th Street, on the north side of the airport. (U.S. Air Force)
Northrop YB-49 42-102367 takes off from Northrop Field, Hawthorne, California. Note the crowds of onlookers and residential housing along W. 120th Street, on the north side of the airport. (U.S. Air Force)

Only two Northrop YB-49s were built and they were tested by Northrop and the Air Force for nearly two years. Though an additional nine YB-35s were ordered converted, the B-49 was not placed into production.

The second ship, YB-49 42-102368, disintegrated in flight during a test flight north of Muroc Air Force Base, 5 June 1948, killing the entire crew, which included Captain Glen Edwards. The name of Muroc was changed to Edwards Air Force Base in his honor.

YB-49 42-102367 was destroyed by fire following a taxiing accident at Edwards, 15 March 1950. The program was cancelled on the same day.

Northrop YB-49 42-102367 in flight near Muroc Air Force Base. (U.S. Air Force)
Northrop YB-49 42-102367 in flight near Muroc Air Force Base. (U.S. Air Force)

© 2018, Bryan R. Swopes

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25 June 1946

Northrop XB-35 taking of at Northrop Field, Hawthorne, California. (U.S. Air Force)
Northrop XB-35 taking off at Northrop Field, Hawthorne, California. (U.S. Air Force)
Max R. Stanley (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers))

25 June 1946: Northrop Aircraft, Inc., experimental test pilot Max R. Stanley and flight engineer Dale Schroeder made the first flight of the Northrop XB-35 “Flying Wing,” serial number 42-13603. They took off from the factory’s airfield at Hawthorne, California, and flew the prototype bomber to Muroc Army Air Field (now, Edwards Air Force Base). The initial flight lasted 55 minutes.

The Los Angeles Times reported:

On June 25, 1946, Stanley piloted the first Flying Wing, the B-35, which was a four-engine 172-foot-long, boomerang-shaped craft, from Northrop’s Hawthorne Airport to what was then the Muroc Army airfield east of Palmdale.

Emerging from the cockpit after the 55-minute flight, Stanley told The Times: “She handled beautifully.”

But taxiing along the rabbit-infested Hawthorne runway, he had had momentary doubts, he conceded 50 years later: “I looked out and I was not gaining speed on this rabbit. I thought, either something’s wrong or that’s one hell of a fast rabbit.”

Flight test crew of Northrop's XB-35 at Northrop Field, Hawthorne, California, 1946.
The flight test crew of the Northrop XB-35 at Northrop Field, Hawthorne, California, 1946. Max Stanley is just to the left of center. (Unattributed)

The XB-35 was designed as an aerodynamically efficient heavy bomber. It had a very unusual configuration for an aircraft of that time. There was no fuselage or tail control surfaces. The crew compartment, engines, fuel, landing gear and armament was contained within the wing. It was 53 feet, 1 inch (16.180 meters) long, with a wingspan of 172 feet (52.426 meters) and overall height of 20 feet, 1 inch (6.121 meters). The prototype weighed 89,560 pounds (40,624 kilograms) empty, with a gross weight of 180,000 pounds (81,647 kilograms).

The Wing defined the airplane. It had an aspect ratio of 7.4:1. The wing’s root chord was 37 feet, 6 inches (11.430 meters). The wing was 7 feet, 1.5 inches (2.172 meters) thick at the root. The tip chord was 9 feet, 4 inches (2.844 meters). There was 0° angle of incidence at the root, -4° at the wing tips, and 0° 53′ dihedral. The leading edge was swept aft 26° 57′ 48″, and the trailing edge, 10° 15′ 22″. The wing’s total area was 4,000 square feet (371.6 square meters).

This view of the Northrop XB-35 Flying W 42-13603 on the ramp at Muroc Air Force Base shows the pusher arrangement of four-bladed contra-rotating propellers. In the background, a turbojet-powered YB-49 is in a right bank.. (U,S. Air Force)
This view of the first prototype Northrop XB-35, 42-13603, the “Flying Wing,” on the ramp at Muroc Air Force Base shows the pusher arrangement of four-bladed contra-rotating propellers. In the background, a turbojet-powered Northrop YB-49 is in a steep bank. (U.S. Air Force)

The XB-35 was powered by four air-cooled, supercharged and turbocharged 4,362.49 cubic-inch-displacement (71.49 liter) Pratt & Whitney Wasp Major TSB1P-RGD (R-4360-17 or  -21) four-row 28-cylinder radial engines with a compression ratio of 7:1. The R-4360-17 was rated at 2,500 horsepower at 2,550 r.p.m at 40,000 feet (12,192 meters), and 3,000 horsepower at 2,700 r.p.m., for takeoff. It could maintain the takeoff rating to an altitude of 40,000 feet (12,192 meters) for Military Power. The engines were mounted completely inside the wing and were connected to a remote propeller drive unit by drive shafts. The engines were direct drive, while the propeller gear boxes had a 0.381:1 reduction ratio. The R-4360-17 was 5 feet, 7.00 inches (1.702 meters) long, 4 feet, 4.50 inches (1.334 meters) in diameter, and weighed 3,306 pounds (1,499.6 kilograms).

Northrop XB-35 42-13603 in flight with early contra-rotating propellers. (U.S. Air Force)

The propellers were dual three-bladed contra-rotating assemblies located in pusher configuration at the wing’s trailing edge. (These were quickly changed to four-bladed propellers, which were smoother in operation and more efficient.)

Northrop XB-35 42-13603. (U.S. Air Force)
Northrop XB-35 42-13603. (U.S. Air Force)

The XB-35 had a cruising speed of 183 miles per hour (295 kilometers per hour) at 39,700 feet (12,100 meters) and maximum speed was 391 miles per hour (629 kilometers per hour) at 35,000 feet (10,668 meters). With a crew of nine, and another six relief crewmembers, the bomber had a range of 8,150 miles (13,116 kilometers).

The production Northrop B-35 would have been armed with twenty .50-caliber machine guns for defense and a maximum bomb load of 51,200 pounds (23,223 kilograms).

The XB-35 was plagued by unresolved problems with the propeller gear boxes which eventually forced Jack Northrop to ground the aircraft until the engine and propeller manufacturers could come up with a solution, which was to change from piston to turbojet engines. That version became the YB-49. Because of the continuing problems, though, 42-13603 was grounded after only 19 flights, and with its sister ship, XB-35 42-38323, was scrapped in August 1949.

Northrop XB-35 in flight. (U.S. Air Force)
A Northrop XB-35 in flight. (U.S. Air Force)

© 2018, Bryan R. Swopes

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