Warplanes of the USA: Northrop YB-35 and YB-49

Northrop YB-35

(USAF Photo)

Northrop YB-35 (Serial No. 42-38323), c1947.

The Northrop YB-35/XB-35, Northrop designation N-9 or NS-9,[2] were experimental heavy bomber aircraft developed by the Northrop Corporation for the United States Army Air Forces during and shortly after the Second World War. The airplane used the radical and potentially very efficient flying wing design, in which the tail section and fuselage are eliminated and all payload is carried in a thick wing. Only prototypes and pre-production aircraft were built, although interest remained strong enough to warrant further development of the design as a jet bomber, under the designation YB-49. (Wikipedia)

(Northrop Photo)

Northrop XB-35 Flying Wing showing its quartet of pusher contra-rotating propellers. The option was later discarded due to severe vibration in flight and later changed to the traditional single propeller configuration.

(USAF Photo)

Northrop YB-35

(USAF Photo)

Northrop YB-35

Crew: 9: pilot, copilot, bombardier, navigator, engineer, radio operator, three gunners. Length: 53 ft 1 in (16.18 m). Wingspan: 172 ft 0 in (52.43 m). Height: 20 ft 3.5 in (6.185 m). Wing area: 4,000 sq ft (370 m2). Aspect ratio: 7.4. Airfoil: root: NACA 653-019; tip: NACA 653-018. Empty weight: 91,000 lb (41,277 kg) with turrets. Gross weight: 154,000 lb (69,853 kg) with turrets. Max takeoff weight: 209,000 lb (94,801 kg). Fuel capacity: 10,000 US gal (8,300 imp gal; 38,000 L) internal; 18,000 US gal (15,000 imp gal; 68,000 L) with bomb-bay auxiliary tanks fitted. Powerplant: 2 × Pratt & Whitney R-4360-45 Wasp Major 28-cylinder air-cooled radial piston engines, 3,000 hp (2,200 kW) each mounted left and right outboard. (Pratt & Whitney R-4360-17 Wasp Major with 8-bladed contra-props). Powerplant: 2 × Pratt & Whitney R-4360-47 Wasp Major 28-cylinder air-cooled radial piston engines, 3,000 hp (2,200 kW) each mounted left and right inboard. (Pratt & Whitney R-4360-21 Wasp Major with 8-bladed contra-props). Propellers: 4-bladed Hamilton Standard HSP24F60-344, 15 ft 3 in (4.65 m) diameter constant-speed fully-feathering pusher propellers (originally flown with 8-bladed contra-rotating propellers). PerformanceMaximum speed: 391 mph (629 km/h, 340 kn). Cruise speed: 240 mph (390 km/h, 210 kn). Range: 7,500 mi (12,100 km, 6,500 nmi). Service ceiling: 39,700 ft (12,100 m) (restricted to 20,000 ft (6,096 m) due to APU problems). Rate of climb: 625 ft/min (3.18 m/s). Wing loading: 45 lb/sq ft (220 kg/m2). Power/mass: 0.07 hp/lb (0.12 kW/kg). ArmamentGuns: 20 × .50 in (12.7 mm) M3 Browning machine guns in six remotely controlled turrets and one tail stinger. Bombs: 52,200 lb (23,678 kg) of bombs, maximum.

Variants:

Northrop XB-35. First flight made in June 1946.

Northrop YB-35. First flight made in July 1948.

Northrop YB-49. Two airframes converted to use eight Allison J35 jet engines. Seven unfinished airframes.

Northrop YRB-49A. YB-35 airframe converted to use six jet engines (two placed in under wing pods) for use as a long-range reconnaissance aircraft. 13 flights.

Northrop EB-35B. Cancelled.

Northrop XB2T. Cancelled.

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Northrop XB-35 (Serial No. 42-13603), escorted by a Northrop P-61 Black Widow.

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Northrop XB-35 (Serial No. 42-13603).

USAF Photo)

Northrop YB-35 escorfted by a Boeing B-17 Flying Fortress.

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Northrop XB-35 (Serial No. 42-13603).

The Northrop XB-35/YB-35 was a propeller-driven experimental heavy bomber aircraft of the mid 1940s, it was later fitted with jet engines and flown as YB-49.

(USAF Photo)

Northrop XB-35 taking off at Northrop Field, Hawthorne, California.

The U.S. Army Air Forces had originally ordered 200 production model B-35s. Since Northrop's facilities were not up to the task of producing them, the Glenn L. Martin Company agreed to undertake mass production. This proved irrelevant when the aircraft had too many development problems. Even disregarding these, so many of Martin's engineers had been drafted by 1944 that Martin pushed the first delivery date back to 1947. Seeing that it would almost certainly never be ready in time for the war, the Army Air Forces canceled the production contract, though the Air Technical Services Command continued to run the program for research purposes.

Actual flight tests of the aircraft revealed several problems: the contra-rotating props caused constant heavy drive-shaft vibration and the government-supplied gearboxes had frequent malfunctions and reduced the effectiveness of propeller control. After only 19 flights, Northrop grounded the first XB-35; the second aircraft was grounded after eight test flights. During this time, the contra-rotating propellers were removed and replaced with four-blade single-rotation propellers. In addition to having continued drive shaft vibration problems, the new single-rotation props greatly reduced the aircraft's speed and performance. Furthermore, the intricate exhaust system turned into a fiasco to maintain. After only two years of use, the engines already showed signs of metal fatigue.

In the end, the program was terminated due to its technical difficulties and the obsolescence of its reciprocating propeller engines, and the fact it was far behind schedule and over budget. Another contributing factor to the program's failure was the tendency of Northrop to become engaged in many experimental programs, which spread its small engineering staff far too wide. While the competing propeller-driven B-36 was obsolete by that time and had just as many or even more development problems, the Air Force needed a very long-range, post-war atomic bomber to counter the perceived Soviet threat. It had more faith that the B-36's "teething" problems could be overcome, compared to those of the new and radical "Flying Wing", the unofficial name that was later associated with all the Northrop "all-wing" designs. (Wikipedia)

Northrop YB-49

(USAF Photo)

Northrop YB-49.

The Northrop YB-49 was an American prototype jet-powered heavy bomber developed by Northrop Corporation shortly after the Second World War for service with the United States Air Force. The YB-49 featured a flying wing design and was a turbojet-powered development of the earlier, piston-engined Northrop XB-35 and YB-35. The two YB-49s built were both converted YB-35 test aircraft.The YB-49 never entered production, being passed over in favor of the more conventional Convair B-36 piston-driven design. Design work performed in the development of the YB-35 and YB-49 nonetheless proved to be valuable to Northrop decades later in the eventual development of the B-2 stealth bomber, which entered service in the early 1990s. (Wikipedia)

(USAF Photo)

Northrop YB-49.

Two YB-35s were modified by replacing the four Pratt & Whitney R-4360 radial engines driving dual contra-rotating propellers with eight Allison TG-180 (J35) turbojet engines. The Army Air Forces approved the change order in June 1945 for the conversion program. Besides the jet engine installations, other modifications included the addition of four vertical stabilizers -- two on each wing installed on both sides of the jet engine exhausts. The wings were fitted with four air dams extending forward from the vertical stabilizer to minimize the airflow down the swept wing (reducing lift) rather than over the wing. The completed aircraft were redesignated YB-49.The first aircraft conversion project took about two years and the aircraft was ready for flight testing in October 1947. The first flight of YB-49 No. 1 (S/N 42-102367) was on the Oct. 21. Results of flight testing showed generally good performance; however, stability during simulated bomb runs and political problems doomed the flying wing. The second aircraft was ready for its first flight on Jan. 13, 1948. Testing continued with both aircraft until the second YB-49 crashed on June 5, 1948. The crew on the ill-fated mission included Maj. Daniel H. Forbes Jr., pilot; Capt. Glen W. Edwards, copilot; Lt. Edward L. Swindell, flight engineer; Clare E. Lesser and C.C. La Fountain. Later, two Air Force installations were renamed in honor of the pilots who lost their lives with the aircraft. Edwards Air ForceBase, Calif., was named in honor of Capt. Edwards, and Forbes Air Force Base, Kan., was named in honor of Maj. Forbes.After the crash of the second YB-49, the first aircraft was modified with additional flight performance measuring instruments before tests were resumed. On March 15, 1950, an Air Force crew was testing the aircraft stabilizer response during a high speed taxi run when the nose wheel began a violent shimmy. Before the aircraft could be brought under control, the nose landing gear collapsed and the No. 1 YB-49 broke in two and was destroyed. (NMUSAF)

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Northrop YB-49 taking to the air for the first time.

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Northrop YB-49.

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Northrop YB-49.

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Northrop YB-49 (Serial No. 42-102367), powerplant.

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Northrop YRB-49A with six engines, two of which are mounted externally.

‍‍Armament: Designed for bomb loads up to 16,000 lbs. of bombs. Engines: Eight Allison J35-A-5 axial flow turbojet engines of 4,000 lbs. thrust each maximumMaximum speed: Approx. 495 mph. Cruising speed: Approx. 420 mph. Range: 4,000 miles with 10,000 lbs. of bombs. Service ceiling: 42,000 ft. Span: 172 ft. 0 in. Length: 53 ft. 1 in. Height: 15 ft. 2 in. Weight: Approx. 213,500 lbs. (maximum alternate weight). Crew: Six (pilot, copilot, flight engineer, radio operator, bombardier, gunner); there were provisions for a relief crew and two more gunners on the proposed production version. Serial numbers: 42-102367 and 42-102368.