Northrop YB-49

https://en.wikipedia.org/wiki/Northrop_YB-49

The Northrop YB-49 was a prototype jet-powered heavy bomber developed by
Northrop Corporation shortly after World War II for service with the U.S. 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 actually 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.

With the XB-35 program seriously behind schedule by 1944, and the end of
piston-engined combat aircraft in sight, the production contract for this
propeller-driven type was cancelled in May of that year. Nevertheless, the
Flying Wing design was still sufficiently interesting to the Air Force that work
was continued on testing a single YB-35A production aircraft.

Among the aircraft later completed were two airframes that the Air Force ordered
be fitted with jet propulsion and designated as YB-49s. The first of these new
YB-49 jet-powered aircraft flew on 22 October 1947 (from Northrop airfield in
Hawthorne, CA) and immediately proved more promising than its piston engined
counterpart. The YB-49 set an unofficial endurance record of staying continually
above 40,000 ft (12,200 m) for 6.5 hours.

The second YB-49 was lost on 5 June 1948, killing its pilot, Major Daniel Forbes
(for whom Forbes Air Force Base was named), co-pilot Captain Glen Edwards (for
whom Edwards Air Force Base is named), and three other crew members, one of
whom, 1st Lieutenant Edward Lee Swindell, was a crew member on the Boeing B-29
that assisted Chuck Yeager in breaking the sound barrier in the Bell X-1
aircraft. Their aircraft suffered structural failure, with both outer wing
sections becoming detached from the center section. Speculation at the time was
that the YB-49 was lost due to excessive pullout loads imposed on the heavy
airframe when a scheduled flight test of the large bomber's stall recovery
resulted in a sudden and dramatic high-speed, nose-over dive. The post-stall
high-speed dive resulted from the clean, low-drag, all-wing design, which gave
the YB-49 a rapid speed increase in any type of dive. Fellow YB-49 test pilot
Robert Cardenas later claimed that the YB-49 rotated backwards in stall, and
that he warned Edwards about it. Jack Northrop later countered that such a
behavior was impossible for the all-wing design.

The conversion of the long-range XB-35 to jet power essentially cut the
effective range of the aircraft in half, putting it in the medium-range bomber
category with Boeing's new swept-winged jet bomber the B-47 Stratojet. The B-47
was optimized for high-altitude and high-speed flight and, in an era where speed
and altitude were becoming the name of the game, the YB-49's thick airfoil could
never be maximized for high-speed performance. In the same Discovery Channel
documentary, former Air Force Flight Test Center Historian Dr. James Young
states his opinion that while political gamesmanship and back room dealing
certainly played a role in the aircraft's demise, the Flying Wing program was
ultimately cancelled for solid technological reasons.


Role
Strategic bomber

Manufacturer
Northrop Corporation

Designer
Jack Northrop

First flight
21 October 1947

Status
Prototype only

Primary user
United States Air Force

Number built
3 converted from YB-35
two YB-49
one YRB-49A
More incomplete examples scrapped

Developed from
Northrop YB-35

Northrop's Flying Wing program may have been terminated due to its technical
difficulties and the program being behind schedule and over budget. Another
possible contributing factor to the cancellation may have been Northrop
spreading its small engineering staff too wide in other experimental programs.
While the competing propeller-driven Convair B-36 "Peacemaker" was an obsolete
World War II-era design by this time, and had been having just as many or even
more development problems, the Air Force seemed to have greater confidence that
its more conventional design and "teething" problems could be overcome, when
compared to those of the more radical Flying Wing. While the YB-49 had
well-documented performance and design issues, the B-36 program needed more
development money. At one time, it appeared the B-36 program might be canceled
as well. But the Air Force and the Texas Congressional delegation desired to
have a production program for their large Fort Worth aircraft production
factory, and Convair had much more effective lobbyists in Washington DC. The
Northrop Corporation was always a technological trailblazer, but the independent
nature of Jack Northrop often collided with the political wheeling-and-dealing
in Washington, which gravitated toward massive military appropriations;
consequently, the obsolete Convair B-36 prevailed. When the YB-49 jet bomber was
canceled, Northrop was awarded a much smaller, lower profile production contract
for its straight-winged F-89 Scorpion fighter as compensation for the canceled
Flying Wing.

Thirty years later, in April 1980, Jack Northrop, then quite elderly and
wheelchair bound, was taken back to the company he founded. There, he was
ushered into a classified area and shown a scale model of the Air Force's
forthcoming but still highly classified Advanced Technology Bomber, which would
eventually become known as the B-2; it was a sleek, all-wing design. Looking
over its familiar lines, Northrop, unable to speak due to various illnesses, was
reported to have written on a pad: "I know why God has kept me alive for the
past 25 years." Jack Northrop died 10 months later, in February 1981, eight
years before the first B-2 entered Air Force service.

Specifications (YB-49)

General characteristics
Crew: 6
Length: 53 ft 1 in (16.18 m)
Wingspan: 172 ft 0 in (52.43 m)
Height: 15 ft 2 in (4.6 m)
Wing area: 4,000 ft² (371.6 m²)
Airfoil: NACA 65-019 root, NACA 65-018 tip
Empty weight: 88,442 lb (40,116 kg)
Loaded weight: 133,569 lb (60,585 kg)
Max. takeoff weight: 193,938 lb (87,969 kg)
Aspect ratio: 7.2
Powerplant: 8 (6 J35-A-19 on the YRB-49A) × Allison J35-A-15 turbojets, 4,000
(5,000 for J35-A-19) lbf (17 kN) each

Performance
Maximum speed: 493 mph (793 km/h)
Cruise speed: 365 mph (587 km/h)
Range: 9,978 mi (16,057 km) maximum
Combat radius: 1,615 mi (1,403 nmi, 2,599 km) with 10,000 lb bombload
Service ceiling: 45,700 ft (13,900 m)
Rate of climb: 3,785 ft/min (19.2 m/s)
Wing loading: 33 lb/ft² (163 kg/m²)
Thrust/weight: 0.23

Armament

Guns: 4 × .50 in (12.7 mm) machine guns (to be mounted in rotating "stinger"
tail cone on all production aircraft)
Bombs: 16,000 lb (7,260 kg) of ordnance





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