The YRB-49A was modified from YB-35 (S/N 42-102376) by installing four Allison J35 turbojet engines in the wings and adding two more in pylon mounted nacelles. The placement of two engines in nacelles allowed more room for fuel in the wings. The additional fuel was necessary for the long-range reconnaissance design mission. Northrop engineers designed the engine pylons to act as vertical stabilizers. They reasoned this would help solve a yaw-axis stability problem, which showed up during YB-49 testing.
The aircraft was designed for the photo reconnaissance role and had camera equipment installed in the center and aft fuselage. The aft lower center fuselage was also modified for a radar navigation system with an extensive external modification required for the radome.
The YRB-49A first flew on May 4, 1950. A short test program of only 13 flights was conducted before the aircraft was put into storage in late 1950. The aircraft was flown one more time on April 26, 1951, from short-term storage facilities at Edwards Air Force Base, Calif., to long-term storage at Northrop's Ontario airport (Calif.) facilities. The YRB-49A sat until it was scrapped in late 1953.
All-jet flying wing, reconnaissance version
TECHNICAL NOTES: Armament: Designed for six 188-lb. T-89 photoflash bombs Engines: Six Allison J35-A-19 axial flow turbojet engines of 5,000 lbs. thrust each maximum Maximum speed: 380 mph Cruising speed: 340 mph Range: 2,250 miles Service ceiling: 45,500 ft. Span: 172 ft. 0 in. Length: 53 ft. 1 in. Height: 15 ft. 2 in. Weight: Approx. 206,000 lbs. (maximum gross weight) Crew: Six (pilot, copilot, flight engineer, radio operator, photo navigator, radar navigator) Serial number: 42-102376