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Boeing 345 / B-29 Superfortress



In March 1936, a team lead by Lysle Wood began work on an updated XB-15, the Model 316. This plane featured the all-glass nose that would make the B-29 distinctive. Designated the Y1B-20, it was 17 percent heavier than the eventual B-29. The Army was not interested. Boeing continued heavy bomber development in 1938 and 1939 with Models 330, 333, 333A, 333B, 334, and 334A. In August 1939 they began work on the Model 341, featuring a much improved wing: the Boeing Model 115 airfoil.

Around 1938, General Henry H. 'Hap' Arnold, the head of the Army Air Corps, was growing alarmed at the possibility of war in Europe and in the Pacific. To prepare the Air Corps, Arnold created a special committee chaired by Brigadier General W. G. Kilner; one of its members was Charles Lindbergh. After a tour of Luftwaffe bases, Lindbergh became convinced that Nazi Germany was far ahead of other European nations. In a 1939 report, the committee made a number of recommendations, including development of new long-range heavy bombers.

When war broke out in Europe, Arnold requested design studies from several companies on a Very Long-Range bomber capable of travelling 5,000 miles (8,000 km). Part of Arnold's motivation for these studies was the fear that Britain might fall to the Nazis. In that event, it would be imperative that the Army Air Force have a bomber capable of flying round-trip from the U.S. East Coast to Europe to strike targets on the European mainland. Approval was granted on December 2. This request, R-40B, fitted perfectly with the research Boeing was doing at the time.

On 29 January 1940, the Air Corps issued a request for proposals for a much larger bomber, which was to have the range for operation over the Pacific; this bomber would serve in the inevitable war with Japan. Four firms submitted design studies: the Boeing XB-29, Lockheed XB-30, Douglas XB-31, and Consolidated XB-32. Douglas and Lockheed soon withdrew, in part because Boeing was well ahead of them in the design process. On 6 September 1940 contracts were awarded to Boeing and Consolidated (later Convair) for the construction and development of two (later three) prototypes of their respective designs. Convair's XB-32 Dominator was the first to fly, on 7 September 1942, but extensive development delayed its entry into service.

In early 1940, the Army Air Corps analysed the performance of bombers used in Europe against the Luftwaffe, and requested that the B-29 have self-sealing fuel tanks, more machine guns, and higher-caliber guns. Boeing incorporated these into a redesign of the Model 341, and resubmitted it to the Army Air Corps as Model 345, which would become the XB-29. Impressed by the mock-up completed in the spring 1941, the Army Air Corps had placed a massive order for 1,500 B-29s, a year before the prototype would fly for the first time on September 21, 1942. A long-range bomber was urgently needed, so service testing proceeded largely in tandem with production. The first B-29 rolled off the assembly line two months after the first service test flight. In under a year, the B-29 was in full-scale production.

The USAAC's specification had called for a speed of 644km/h, so the XB-29 had a high aspect ratio cantilever monoplane wing mid-set on the circular-section fuselage. Because such a wing would entail a high landing speed, the wide-span trailing-edge flaps were of the Fowler type which effectively increased wing area by almost 20%, thus allowing a landing to be made at lower speed. Electrically retractable tricycle landing gear was provided and, as originally proposed by Boeing, pressurised accommodation was included for the flight crew. In addition, a second pressurised compartment just aft of the wing gave accommodation to crew members who, in the third XB-29 and production aircraft, sighted defensive gun turrets from adjacent blister windows. The crew and aft compartments were connected by a crawl-tunnel which passed over the fore and aft bomb bays. The tail gunner was accommodated in a third pressurised compartment, but this was isolated from the other crew positions.




 Rather than the traditional bulky manned gun turrets, Boeing used small, remote-control units 'networked' together with an analog computer that compensated for factors such as air temperature and bullet drop. This system was very difficult to develop, but it proved effective. Each gun was served by a 1,000 round bullet belt.

The powerplant consisted of four Wright R-3350 Cyclone twin-row radial engines, each with two General Electric turbochargers mounted one in each side of the engine nacelle.

Prototype production was followed by 14 YB-29 service test aircraft, the first of these flying on 26 June 1943. Deliveries of YB-29s began almost immediately to the 58th Very Heavy Bombardment Wing (VHBW), a unit which had been established on 1 June in advance of the first flight. B-29 production was the most diverse aircraft manufacturing project undertaken in the USA during World War II, with literally thousands of sub-contractors supplying components or assemblies to the four main production plants: Boeing at Renton and Wichita; Bell at Marietta, Georgia; and Martin at Omaha, Nebraska.

Because of its highly advanced design, challenging requirements, and immense pressure for production, development was deeply troubled. The first prototype crashed during testing, killing the entire crew and several ground personnel. Changes to the production craft came so often and so fast that in early 1944, B-29s would leave the production lines and fly directly to modification depots for extensive rebuilds to incorporate the latest changes. This 'battle of Kansas' nearly sank the program, which was only saved by General Hap Arnold's direct intervention. It would still be nearly a year before the aircraft was operated with any sort of reliability.

The most common cause of maintenance headaches and catastrophic failures, even more so than the advanced gunnery system, was the engine. Though the Wright R-3350 would later become a trustworthy workhorse in large piston-engined aircraft, early models were beset with dangerous reliability problems. It had an impressive power-to-weight ratio, but this came at a heavy cost to durability. Worse, the cowling Boeing designed for the engine was too close (out of a desire for improved aerodynamics), and the early cowl flaps caused problematic flutter and vibration when open in most of the flight envelope.

These weaknesses combined to make an engine that would overheat regularly when carrying combat loads; it frequently swallowed its own valves. The resulting engine fires were exacerbated by a crankcase designed mostly of magnesium alloy. The heat was often so intense the main spar burned through in seconds, resulting in catastrophic failure of the wing. This problem would not be fully cured until the aircraft was re-engined with the more powerful Pratt & Whitney R-4360 'Wasp Major' in the B-29D/B-50 program, which arrived too late for World War II. Pilots, including the present-day pilots of the Commemorative Air Force's Fifi, describe flight after takeoff as being an urgent struggle for airspeed. Radial engines need that airflow to keep cool, and failure to get up to speed as soon as possible could result in an engine failure and risk of fire.




The initial plan was to use B-29s to attack Japan from airfields in southern China, with the main base in India, and to attack other targets in the region from China and India as needed. This was an extremely costly scheme, as there was no overland connection available between India and China, and all the supplies had to be flown over the Himalayas. The first B-29s started to arrive in India in early April, 1944. The first B-29 flight to airfields in China (over the Himalayas, or "The Hump") took place on 24 April 1944. The first B-29 combat mission was flown on 5 June 1944, with 77 out of 98 planes launched from India bombing the railroad shops in Bangkok (5 B-29s were lost to non-battle causes).

On June 15, 1944, 47 B-29s launched from Chengtu in China bombed the Imperial Iron and Steel Works at Yawata, Japan. This was the first attack on Japanese islands since the Doolittle raid in April, 1942. The first B-29 combat loss occurred during this raid, with 1 B-29 destroyed on the ground by Japanese fighters after an emergency landing. Because of the extreme cost of operations, the raids against Japan from Chinese airfields continued at relatively low intensity. Japan was bombed on: 7 July 1944 (14 B-29s), 29 July (70+), 10 August (24), 20 August (61), 8 September (90), 26 September (83), 25 October (59), 12 November (29), 21 November (61), 19 December (36) and for the last time on 6 January 1945 (49). B-29s were withdrawn from airfields in China by the end of January, 1945. Throughout this period B-29 raids were also launched from China and India against many other targets throughout South-East Asia. However, the entire B-29 effort was gradually shifted to the new bases in the Marianas, with the last B-29 combat mission from India flown on March 29, 1945.

The need to use inconvenient bases in China for attacks against Japan ceased after the capture of the Marianas islands in 1944. On the islands of Tinian, Saipan and Guam a series of airfields were built, which became the main bases for the large B-29 raids against Japan in the final year of the war. The islands could be easily supplied by ship. The first B-29 arrived on Saipan on 12 October 1944, and the first combat mission was launched from there on 28 October 1944, with 14 B-29s attacking the Truk atoll. The first mission against Japan from bases in the Marianas was flown on 24 November 1944, with 111 B-29s sent to attack Tokyo. From that point ever more intense raids were launched regularly until the end of the war. These attacks succeeded in devastating all large Japanese cities and gravely damaged Japan's war industries.

Perhaps the most recognized B-29 is the Enola Gay, which dropped the atomic bomb 'Little Boy' on Hiroshima on 1945 August 6. The Bockscar, also a B-29, dropped 'Fat Man' on Nagasaki three days later.

The B-29 was used in World War II only in the Pacific Theatre. It was later used in the Korean War, over the course of which they flew 20,000 sorties and dropped 200,000 tons (180,000 tonnes) of bombs. 3970 of the aircraft were built before they were retired in 1960. The B-29 was soon made obsolete by the development of the jet engine. With the arrival of the mammoth B-36, the B-29 suffered its first ignominy by being classified a medium bomber with the new Air Force. However, the later B-29D/B-50 variant was good enough to handle auxiliary roles such as air-sea rescue, electronic intelligence gathering, and even air-to-air refuelling. It was replaced in its primary role during the early 1950s by the Boeing B-47 Stratojet, which in turn was replaced by the Boeing B-52 Stratofortress. The final active duty variants were phased out in the mid 1960s.

B-29 production totalled 1,644 from Boeing's Wichita plant, with 668 built by Bell and 536 by Martin. The Renton plant produced only the B-29A variant, with a 12in wider span, later marks of the 2,200hp Wright R-3350 engines, changes in fuel capacity, and the addition of a four gun forward dorsal turret and armament: production continued until May 1946 and totalled 1,122 aircraft.

The designation B-29B related to 311 of the aircraft built by Bell. These were reduced in weight by removal of all defensive armament except for the tail guns, which were then unmanned, being aimed and fired automatically by an AN/APG-15B radar fire-control system. The production total of 3970 B-29s of all versions saw a wide variety of employment in the post-war years, operating under several designations. A number of B-29s were used operationally during the Korean War.




B-29s were followed by several hundred of many versions of the B-50, with more powerful engines and other changes. These saw action only as tankers in the Vietnam War, but B-29s operated throughout the Korean War, the 22nd and 92nd Bomb Groups open-ing strategic missions as early as 13 July 1950. Though never more than 99 B-29s were on strength, the two groups flew 21,000 sorties and dropped 167,100 tons, more than the tonnage dropped by B-29s in World War II.

B-29s force-landed in Soviet territory were dissected in minute detail, and the Tupolev design bureau built first a simple transport, the Tu-70, followed in July 1947 by the first Tu-4 bomber. This was a B-29 except in having 23-mm cannon in its five twin turrets. About 400 were built, but they did not see action; their main importance was that they were the starting point for all to-day's Tupolev strategic turboprop and jet bombers. Some of these remained in service into the 1960s in the Soviet Union. All but one of the Tu-4s were scrapped in the 1960s. The lone example of a Tu-4 known to exist today is located at the Yuri Gagarin Air Force Academy near Moscow, as a static display. This particular airplane was tasked with bombing the Budapest headquarters of the Hungarian rebel movement during the 1956 rebellion; but although the mission was rehearsed it was never put into play.

The KB-29 was the tanker version of the B-29, the SB-29 the search & rescue version, carrying a lifeboat; the DB-29 was a drone controller, the TB-29 a trainer, the RB-29 a reconnaissance aircraft. Some B-29s were also used as launch aircraft for research aircraft like the X-1 and X-2. The KB-29P flying boom flight refuelling tanker version and the SB-29 search and rescue aircraft were still in service in 1955. The SB-29 equipped to carry an A.3 remote control lifeboat under its fuselage.



Boeing KB-29P


Eventually 4221 B-29 were built.


1 June 1943
The USAAF's 58th Heavy Bombardment Wing was established. This wing was equipped with Boeing B-29 superfortresses for strategic attack on Japan.

15 June 1944
47 B-29s bombed the imperial iron and steel works at Yawata Japan.

20 November 1945
A new non-stop distance record of 7,916 miles was set by B-29 bomber "Pacusan Dreamboat" after flying from the island of Guam to Washington DC.

1 November 1954
The last B-29 in front-line service, based at Kadena, was retired. The B-29s were replaced by the B-47.





Engines: 4 x Wrigth R-3350-23 (supercharged radial engines), 1600kW/ 2,200 hp
Wing Span: 142.26ft (43.36m)
Length: 99.02ft (30.18m)
Height: 29.56ft (9.01m)
Wing Area: 161.27 sq.m
Empty Weight: 71,361lbs (32,369kg)
Max.Weight: 141,102lbs (64,003kg)
Maximum Speed: 358mph (576kmh; 311kts)
Service Ceiling: 31,808ft (9,695m)
Maximum Range: 4,100miles (6,598km)
Rate-of-Climb: 526ft/min (160m/min)
Wing loading: 337 kg/sq.m
Armament: 1 x 20mm, 12 x mg 12.7mm,
Bombload: 20,000lbs / 9072 kg
Crew: 10 (pilot, co-pilot, flight engineer, bombardier, navigator, radio operator, side gunners (two), top gunner, and tail gunner)

Engines: Four Wright R-3350-21 or -23 "Cyclone" radials  with two type B-11 turbo superchargers; later B-29 models fitted with -23A, -41 or -57 Cyclone radials
Engine gear ratio: 20:7 (.35)
Take-off power: 2,200 hp at 2,600 rpm w/ manifold pressure of 47.5 in.
Military power: 2,200 hp at 2,600 rpm w/ manifold pressure of 47.5 in at 25,000 ft.
Normal rated power: 2,000 hp at 2,400 rpm at sea level
Idling speed: 600 +/- 50 rpm (propeller at increase rpm)
Manufacturer: Hamilton Standard Propeller division of United Aircraft Corp.
Type: 4-blade, full feathering
Diameter: 16 ft. 7 in.
Span: 141 ft. 2.76 in.
Length: 99 ft. 0 in.
Height: 27 ft. 9 in. (at rest) 27 ft. 6.7 in. (taxi position)
Maximum fuselage diameter: 9 ft. 6 in.
Height to centerline of propeller hub (taxi position)
1. Inboard engines: 9 ft. 5.6 in.
2. Outboard engines: 10 ft. 8 in.
Ground clearance of inboard propeller tips (taxi position): 14.1 in.
Airfoil section: Boeing 117
1. Root: 22%
2. Tip: 7%
Chord root: 17 ft.
Chord tip (70 feet 10 inches from centerline of fuselage): 7 ft. 5 in.
Incidence: 4 degrees
Dihedral: 4 degrees 29 minutes 23 seconds
Sweepback: 7 degrees 1 minute 26 seconds
Span: 43 ft.
Maximum chord: 11 ft. 2.4 in.
Wing (less ailerons): 1609.68 sq. ft.
Wing (flaps extended, plus ailerons): 2070.88 sq. ft.
Alierons (total, including tabs): 129.2 sq. ft.
Flaps (total): 332 sq. ft.
Stabilizer and elevators (including tabs): 333 sq. ft.
Elevators (total including tabs): 115 sq. ft.
Elevator trim tabs (total): 10.12 sq. ft.
Vertical fin: 131.9 sq. ft.
Dorsal fin: 40.6 sq. ft.
Rudder (including tab): 65.5 sq. ft.
Rudder trim tab: 5.79 sq. ft.
Weight: 133,500 lbs. (maximum overload) 105,000 lbs. gross
Armament: 10 or 12 .50-cal. machine guns and one 20mm cannon plus 20,000 lbs. of bombs.
Fuel Tank Capacities:
Regular wing (22 cells): 5608 US gals. (4669 Imp.)
Auxiliary center wing (four cells): 1333 US gals. (1110 Imp.)
Auxiliary bomb bay (four cells): 2560 US gals. (2133 Imp.)
Net Total capacity: 9501 US gals. (7912 Imp.)
Crew: Normal crew of 10 consists of Pilot, Co-Pilot, Flight Engineer, Bombardier, Navigator, Radio Operator, (2) Side Gunners, Top Gunner, and Tail Gunner
Maximum speed: 357 mph at 25,000 ft.
Cruising speed: 220 mph
Range: 5,600 miles maximum ferry range and 3,250 miles with 20,000 lbs. of bombs
Service ceiling: 33,600 ft.

Crew: 10
Engines: 4 x Wright R-3350-23-23A/-41 Cyclone 18, 1641kW
Take-off weight: 56245 kg / 124000 lb
Empty weight: 31815 kg / 70140 lb
Wingspan: 43.05 m / 141 ft 3 in
Length: 30.18 m / 99 ft 0 in
Height: 9.02 m / 29 ft 7 in
Wing area: 161.27 sq.m / 1735.89 sq ft
Max. speed: 576 km/h / 358 mph
Cruise speed: 370 km/h / 230 mph
Ceiling: 9710 m / 31850 ft
Range w/max.fuel: 5230 km / 3250 miles
Range w/max.payload: 2880 km / 1790 miles
Armament: 11 x 12.7mm machine-guns, 9000kg of bombs


Engines: 4 x four 2,200-hp (1641-kW) Wright R-3350-57 (or related) Duplex Cyclone 18-cylinder radials.
Wing span: 43.05 m (141 ft 3 in).
Length: 30.18 m (99 ft 0 in).
Height: 9.02 m (29 ft 7 in).
Wing area: 161.28 sq.m (1,736.0 sq ft).
Weight empty: 31816 kg (70,140 lb).
MTOW: 64002 kg (141,100 lb).
Maximum speed: 576 km/h (358 mph) at high altitudes.
Service ceiling: 9750 m (32,000 ft).
Range with maximum bombload: 5230 km (3,250 miles).
Armament: bombload of 9072 kg (20, 000 lb), plus 10 12.7-mm (0,5-in) machine-guns and one 20-mm cannon in five turrets.
Crew: 10.

Engines: 4 x four 2,200-hp (1641-kW) Wright R-3350-57 (or related) Duplex Cyclone 18-cylinder radials.
Wing span: 43.05 m (141 ft 3 in).
Length: 30.18 m (99 ft 0 in).
Height: 9.02 m (29 ft 7 in).
Wing area: 161.28 sq.m (1,736.0 sq ft).
Maximum speed: 576 km/h (358 mph) at high altitudes.
Service ceiling: 9750 m (32,000 ft).
Range with maximum bombload: 5230 km (3,250 miles).
Weight empty: 31816 kg (70,140 lb).
MTOW: 64002 kg (141,100 lb).
Armament: bombload of 9072 kg (20, 000 lb), plus 10 12.7-mm (0, 5-in) machine-guns and one 20-mm cannon in five turrets.
Crew: 10.


Flight refuelling tanker.
Engines: 4x 2,200 h.p. Wright R3350-57 or -83
Wingspan: 141 ft. 3 in
Length: 99 ft.
Max speed: 351 m.p.h.
Ceiling: over 35,000 ft.
Range: 4,600 miles





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