Boeing B-29/B-50 Superfortress

The Boeing B-29 Superfortress is an American four-engine propeller driven heavy bomber and used primarily by the United States during World War II and the Korean War.

Named in allusion to its predecessor, the B-17 Flying Fortress, the Superfortress was designed for high-altitude strategic bombing but also excelled in low altitude night incendiary bombing and in dropping naval mines to blockade Japan.

B-29s dropped the atomic bombs on Hiroshima and Nagasaki and became the only aircraft that has ever used nuclear weapons in combat.

Variants

XB-29

The XB-29, Boeing Model 345, was the first accepted prototype or experimental model delivered to the USAAC, incorporating a number of improvements on the design originally submitted, including more and larger guns and self sealing fuel tanks.

Two aircraft were ordered in August 1940, and a third was ordered in December.

A mock up was completed in the spring of 1941, and it first flew on September 21, 1942.

YB-29

The YB-29 was an improved XB-29 and 14 were built for service testing.

Testing began in the summer of 1943, and dozens of modifications were made to the planes.

The engines were upgraded from Wright R-3350-13s to R-3350-21s.

Where the XB-29 had three-bladed props, the YB-29 had four-bladed propellers.

Various alternatives to the remote-controlled defensive systems were tested on a number of them.

B-29

The B-29 was the original production version of the Superfortress.

Since the new bomber was urgently needed, the production design was developed in tandem with the service testing.

In fact, the first B-29 was completed only two months after the delivery of the first YB-29.

Forty six B-29s of this variant, built by the Glenn L. Martin Company at its Omaha plant, were used as the aircraft for the atomic bomb missions, modified to Silverplate specifications.

B-29A

Enhancements made in the B-29A included a better wing design and defensive modifications.

Due to a demonstrated weakness to head on fighter attacks, the number of machine guns in the forward dorsal turrets was doubled to four.

Where the wings of previous models had been made by the sub-assembly of two sections, the B-29A wing was built up from three.

This made construction easier, and increased the strength of the airframe.

The B-29A was produced until May 1946, when the last aircraft was completed.

It was much used during the Korean War, but was quickly phased out when the jet bomber (B-47 Stratojet) became operational.

Washington B Mk 1

This was the service name given to 88 B-29As supplied to the Royal Air Force.

B-29B

In the B-29B, as with the atomic raid-dedicated Silverplate versions earlier, all defensive armament was removed except for that in the tail turret.

Initially the armament was two .50 in AN/M2 machine guns and one 20 mm M2 cannon which was soon changed to three .50 in AN/M2s.

The weight saved by removing the guns increased the top speed from 357 mph to 364 mph (575 km/h to 586 km/h).

Also incorporated on this version was an improved APQ-7 “Eagle” bombing through-overcast radar that was fitted in an airfoil shaped radome under the fuselage.

B-29C

The B-29C was a modification of the B-29A re-engined with improved Wright R-3350 engines.

The Army Air Force originally ordered 5,000, but cancelled its request when World War II ended and none were built.

B-29D (XB-44)

The B-29D was an improved version of the original B-29 design, featuring 28-cylinder Pratt & Whitney R-4360-35 Wasp Major engines of 3500 hp (2600 kW) each, nearly 60% more powerful than the usual Duplex-Cyclone.

It also had a taller vertical stabilizer and a strengthened wing.

The XB-44 was the testbed designation for the D model.

When World War II ended, the B-29D was given the quartet of Wasp Major engines to become the B-50, which served throughout the 1950s in the U.S. bomber fleet.

Testbeds

XB-29E, XB-29F, XB-29G, XB-29H, YB-29J, YKB-29J, RB-29J,

KB-29 Tanker Development

The Boeing KB-29 was a modified Boeing B-29 Superfortress for air refuelling needs by the USAF.

Two primary versions were developed and produced, KB-29M and KB-29P.

EB-29

The EB-29 (E stands for exempt), was used as a carrier aircraft in which the bomb bay was modified to accept and launch experimental aircraft.

They were converted in the years following World War II. 

RB-29J

(RB-29, FB-29J, F-13, F-13A)

Early B-29/B-29As that were modified for photo reconnaissance carried the F-13/F-13A designations, with “F” meaning ‘Photo’.

The aircraft carried three K-17B, two K-22 and one K-18 cameras.

Between 1945 and 1948 the designation was changed to FB-29J.

In 1948, the F-13/FB-29s were redesignated RB-29 and RB-29A.

Six B-29A/F-13As were modified with the Wright R-3350-CA-2 fuel injected engines and designated at YB-29Js.

These were then converted to RB-29Js.

In January 1949, RB-29s were assigned to the 91st Strategic Reconnaissance Wing and moved to Yokota AB, Japan in December 1950, to provide support to the Korean War and attached to the 15th Air Force, Far East Air Force.

SB-29

The SB-29 ‘Super Dumbo’ was a version of the B-29 adapted for air-sea rescue duty after World War II.

Sixteen B-29s were modified to carry a droppable A-3 lifeboat under the fuselage.

Redesignated SB-29, they were used mainly as rescue support for air units that flew long distances over water. 

TB-29

The TB-29 was a trainer conversion of B-29 used to train crew for bombing missions, some were also used to tow targets, and the designation included B-29s modified solely for that purpose.

Their most important role was serving as radar targets in the 1950s when the United States Air Force was developing intercept tactics for its fighters.

WB-29

The WB-29s were production aircraft modified to perform weather monitoring missions.

An observation position was fitted above the central fuselage section.

They conducted standard data-gathering flights, including from the UK over the Atlantic.

They were also used to fly into the eye of a hurricane or typhoon to gather information.

Following nuclear weapons tests, some WB-29s used air sampling scoops to test radiation levels. 

Airborne Early Warning

In 1951, three B-29s were modified for use in the Airborne Early Warning program.

The upper section of the forward fuselage was extensively modified to house an AN/APS-20C search radar, and the interior was modified to house radar and Electronic Counter Measures (ECM) equipment.

MX-767 Banshee

A study for the conversion of B-29s to long-range cruise missiles was conducted by the Air Material Command between 1946 and 1950, given the designation MX-767, it was given the codename Project Banshee.

Flight tests were conducted, however no full conversions were carried out before the project was abandoned.

Navy P2B patrol bomber

The U.S. Navy acquired four B-29-BWs from the U.S. Army Air Forces on March 14, 1947.

These aircraft were modified for long range patrol missions and given the designation P2B-1S. 

Other Types

XB-39

A single YB-29 modified to use water-cooled Allison V-3420-17 Vee type engines.

Tupolev Tu-4

In 1945, three B-29s were forced to land in Soviet territory after a bombing raid on Japan because of lack of fuel, Seeking a modern long range bomber, Joseph Stalin ordered the Tupolev OKB to reverse-engineer the Superfortress.

KJ-1 AEWC

The People’s Liberation Army Air Force of China attempted to use the Tu-4 airframe in the KJ-1 AWACS aircraft.

B-50 Superfortress

A post World War II revision of the Boeing B-29 Superfortress, it was fitted with more powerful Pratt & Whitney R-4360 radial engines, stronger structure, a taller tail fin, and other improvements.

Specifications

B-29

Crew

11

Length

99 ft 0 in (30.18 m)

Wingspan

141 ft 3 in (43.05 m)

Height

27 ft 9 in (8.46 m)

Wing area

1,736 sq ft (161.3 m2)

Aspect ratio

11.5

Airfoil

Root

Boeing 117 (22%)

Tip

Boeing 117 (9%)

Zero-lift drag coefficient

0.0241

Frontal area

41.16 sq ft (3.824 m2)

Empty weight

74,500 lb (33,793 kg)

Gross weight

120,000 lb (54,431 kg)

Max take-off weight

133,500 lb (60,555 kg)

135,000 lb (61,000 kg) Combat overload

Powerplant

4 × Wright R-3350-23 Duplex-Cyclone 18-cylinder air-cooled turbo supercharged radial piston engines, 2,200 hp (1,600 kW) each

Propellers

4-bladed constant-speed fully feathering propellers,

16 ft 7 in (5.05 m) diameter

Performance

Maximum speed

357 mph (575 km/h, 310 kn)

Cruise speed

220 mph (350 km/h, 190 kn)

Stall speed

105 mph (169 km/h, 91 kn)

Range

3,250 mi (5,230 km, 2,820 nmi)

Ferry range

5,600 mi (9,000 km, 4,900 nmi)

Service ceiling

31,850 ft (9,710 m) 

Rate of climb

900 ft/min (4.6 m/s)

Lift-to-drag

16.8

Wing loading

69.12 lb/sq ft (337.5 kg/m2)

Power/mass

0.073 hp/lb (0.120 kW/kg)

Armament

Guns

8 or 10× .50 in (12.7 mm) Browning M2/ANs in remote controlled turrets.

(Omitted from Silverplate B-29s)

2× .50 BMG and 1× 20 mm M2 cannon in tail position

(The cannon was later removed)

Bombs

5,000 lb (2,300 kg) over 1,600 mi (2,600 km; 1,400 nmi) radius at high altitude

12,000 lb (5,400 kg) over 1,600 mi (2,600 km; 1,400 nmi) radius at medium altitude

20,000 lb (9,100 kg) maximum over short distances at low altitude

Could be modified to carry two 22,000 lb (10,000 kg) Grand Slam bombs externally.

The Silverplate version delivered the first atomic bombs.

 

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