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.
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.
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.
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.
25 June 1946: Northrop Aircraft, Inc., experimental test pilot Max R. Stanley, flight test engineer Dale Schroeder and Orva H Douglas, Jr., flight engineer, 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:
Gigantic Flying Wing Triumphs in First Flight
Northrop 110,000-Pound Superbomber Soars 44 Minutes, makes Perfect Landing
Unleashed into the future, a huge and spectral devilfish bellowed up from the earth yesterday and soared eastward toward the morning sun—Northrop’s malevolent Flying Wing superbomber on her maiden test flight, Forty-four minutes later teh ship made a perfect landing at Muroc Army Airfield.
Eerie, almost supernatural, she trundled to the west end of Northrop’s mile-long Hawthorne runway as the sun burned away the morning mists.
For 45 minutes she stood motionless, a 172-foot knife blade, while her four 3000 h.p. engines turned eight coaxial pusher propellers into life.Then at 10:29 a.m. her whirling blades fused into blurred disks. Her thunder enveloped the field.
Interminably she seemed to hug the ground as Test Pilot Max Stanley held her charging 110,000 pounds down past the hangars, past the flight line, past the midfield control tower.
Monster Leaves Ground
For 30 thudding heartbeats—and as many seconds—the fantastic silver monster strained at the shackles of earth, hurtling at more than 100 m.p.h. toward the end of the runway.
Then at 3000 feet Stanley eased back the yoke. Sunlight skipped beneath the spinning wheels and the Wing lifted into her element under perfect control.
Vanishes Into Haze
In another 60 seconds she vanished into the haze, her wheels still down as Stanley gently tested her sinews. Below, and to the right of his bubble canopy, Co-pilot Fred C. Bretcher stared ahead through plexiglas in the leading edge, and just aft of the pilot, Engineer O. H. Douglas watched her pulse in the needles of scores of instruments.
In an easy climb, Stanley took the superbomber to 10,000 feet over the flat lands between the San Gabriel Mountains and the sea and then banked her slowly north and inland toward Muroc.
Settles to Runway
At the Muroc test field, the strip was cleared and ready. Spectators watched the incredible ship circle once and then gently settle to the runway as gently as a tuft of cotton and roll to stop in 3000 feet.”She handled beautifully,” grinned Stanley.
The outgrowth of years of engineering, she followed the secret testing of a parade of small wings, and her designer, John K. Northrop, is confident she’ll carry more bombs farther and faster than any other airplane ever built.
Fourteen more of the giants will be built under Northrop’s contract with the Army.
—Los Angeles Times, Vol. LXV, Wednesday Morning, 26 June 1946, Page 1, Columns 5 and 6
The Los Angeles Daily News reported:
Flying wing passes tests
Everybody who had anything to do with it was happy today over the 44-minute maiden flight of Northrop’s flying wing.
The bat-like plane, a 104-ton monster bomber, met all expectations during the 85-mile flight from Northrop Field to Muroc Army Air Base.
“The wing handled just as I expected it would,” veteran test pilot Max Stanley declared after landing the giant ship. “We were delighted with its performance and the plane fully came up to our expectations.”
Officials of Northrop Aircraft, who witnessed the initial take-off, said the flight had justified their confidence in the wing.
The ship, a tailess airplane with a bat-like appearance, is the latest in a series of 15 Northrop designed flying wings and was built at a cost of $13,000,000 for the army.
—Daily News, Wednesday, 26 June 1946, Page 3, Column 1
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, with -4° of twist, 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).
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).
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.)
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.