Boeing B-29 Superfortress

Features

Defensive gun turret emplacements

In wartime, the B-29 was capable of flight at altitudes up to 31,850 feet (9,710 m), at speeds of up to 350 mph (560 km/h; 300 kn) (true airspeed). This was its best defense because Japanese fighters could barely reach that altitude, and few could catch the B-29 even if they did attain that altitude.

The General Electric Central Fire Control system on the B-29 directed four remotely controlled turrets armed with two .50 Browning M2 machine guns each. All weapons were aimed optically, with targeting computed by analog electrical instrumentation. There were five interconnected sighting stations located in the nose and tail positions and three Plexiglas blisters in the central fuselage. Five General Electric analog computers (one dedicated to each sight) increased the weapons' accuracy by compensating for factors such as airspeed, lead, gravity, temperature and humidity. The computers also allowed a single gunner to operate two or more turrets (including tail guns) simultaneously.

The gunner in the upper position acted as fire control officer, managing the distribution of turrets among the other gunners during combat. The tail position initially had two .50 Browning machine guns and a single M2 20 mm cannon, and had the ability to override control of the two rear turrets if a target exceeded the maximum angle of the tail weaponry. If the tail gunner or nose gunner are not using the forward or tail weaponry, control is automatically transferred to the waist gunners, who have full 360 degree targeting ability, but limited to 60 degrees of vertical targeting movement. Later aircraft had the 20 mm cannon removed, sometimes replaced by a third machine gun.

In early 1945, Major General Curtis LeMay, commander of XXI Bomber Command—the Marianas-based B-29-equipped bombing force—ordered most of the defensive armament and remote-controlled sighting equipment removed from the B-29s under his command. The affected aircraft had the same reduced defensive firepower as the nuclear weapons-delivery intended Silverplate B-29 airframes and could carry greater fuel and bomb loads as a result of the change. The lighter defensive armament was made possible by a change in mission from high-altitude, daylight bombing with high explosive bombs to low-altitude night raids using incendiary bombs. As a consequence of that requirement, Bell Atlanta (BA) produced a series of 311 B-29Bs that had turrets and sighting equipment omitted, except for the tail position, which was fitted with AN/APG-15 fire-control radar. That version could also have an improved APQ-7 "Eagle" bombing-through-overcast radar fitted in an airfoil-shaped radome under the fuselage. Most of those aircraft were assigned to the 315th Bomb Wing, Northwest Field, Guam.

Pressurization

The crew would enjoy, for the first time in a bomber, full-pressurization comfort. This first-ever cabin pressure system for an Allied production bomber was developed for the B-29 by Garrett AiResearch. Both the forward and rear crew compartments were to be pressurized, but the designers had to decide whether to have bomb bays that were not pressurized or a fully pressurized fuselage that would have to be de-pressurized prior to opening the bomb bay doors. The solution was to have bomb bays that were not pressurized and a long tunnel joining the forward and rear crew compartments. Crews could use the tunnel if necessary to crawl from one pressurized compartment to the other.

Operational history

World War II

In September 1941, the United States Army Air Forces' (AAF) plans for war against Germany and Japan proposed basing the B-29 in Egypt for operations against Germany, as British airbases were likely to be overcrowded. Air Force planning throughout 1942 and early 1943 continued to have the B-29 deployed initially against Germany, transferring to the Pacific only after the end of the war in Europe. By the end of 1943, plans had changed, partly due to production delays, and the B-29 was dedicated to the Pacific Theater. A new plan implemented at the direction of President Franklin D. Roosevelt as a promise to China, called Operation Matterhorn, deployed the B-29 units to attack Japan from four forward bases in southern China, with five main bases in India, and to attack other targets in the region from China and India as needed. The Chengdu region was eventually chosen over the Guilin region to avoid having to raise, equip, and train 50 Chinese divisions to protect the advanced bases from Japanese ground attack. The XX Bomber Command, initially intended to be two combat wings of four groups each, was reduced to a single wing of four groups because of the lack of availability of aircraft, automatically limiting the effectiveness of any attacks from China.

This was an extremely costly scheme, as there was no overland connection available between India and China, and all supplies had to be flown over the Himalayas, either by transport aircraft or by B-29s themselves, with some aircraft being stripped of armor and guns and used to deliver fuel. 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 B-29s launched from India bombing the railroad shops in Bangkok and elsewhere in Thailand. Five B-29s were lost during the mission, none to hostile fire.

Forward base in China

On 5 June 1944, B-29s raided Bangkok, in what is reported as a test before being deployed against the Japanese home islands. Sources do not report from where they launched and vary as to the numbers involved—77, 98, and 114 being claimed. Targets were Bangkok's Memorial Bridge and a major power plant. Bombs fell over 1.2 miles (2 km) away, damaged no civilian structures, but destroyed some tram lines, and destroyed both a Japanese military hospital and the Japanese secret police headquarters. On 15 June 1944, 68 B-29s took off from bases around Chengdu, 47 B-29s bombed the Imperial Iron and Steel Works at Yawata, Fukuoka Prefecture, Japan. This was the first attack on Japanese islands since the Doolittle Raid in April 1942. The first B-29 combat losses occurred during this raid, with one B-29 destroyed on the ground by Japanese fighters after an emergency landing in China, one lost to anti-aircraft fire over Yawata, and another, the Stockett's Rocket (after Capt. Marvin M. Stockett, aircraft commander) B-29-1-BW 42-6261, disappeared after takeoff from Chakulia, India, over the Himalayas (12 KIA, 11 crew and 1 passenger). This raid, which did little damage to the target, with only one bomb striking the target factory complex, nearly exhausted fuel stocks at the Chengdu B-29 bases, resulting in a slow-down of operations until the fuel stockpiles could be replenished. Starting in July, 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)
• 6 January 1945 (49)

B-29s were withdrawn from airfields in China by the end of January 1945. Throughout the prior period, B-29 raids were also launched from China and India against many other targets throughout Southeast Asia, including a series of raids on Singapore and Thailand. On 2 November 1944, 55 B-29s raided Bangkok's Bang Sue marshaling yards. Seven RTAF Nakajima Ki-43 Hayabusas from Foong Bin (Air Group) 16 and 14 IJAAF Ki-43s attempted to intercept. RTAF Flt Lt Therdsak Worrasap attacked a B-29, damaging it, but was shot down by return fire. One B-29 was lost, possibly the one damaged by Flt Lt Therdsak. On 14 April 1945, a second B-29 raid on Bangkok destroyed two key power plants and was the last major attack conducted against Thai targets. The B-29 effort was gradually shifted to the new bases in the Mariana Islands in the Central Pacific, with the last B-29 combat mission from India flown on 29 March 1945.

New Mariana Islands air bases

In addition to the logistical problems associated with operations from China, the B-29 could reach only a limited part of Japan while flying from Chinese bases. The solution to this problem was to capture the Mariana Islands, which would bring targets such as Tokyo, about 1,500 mi (2,400 km) north of the Marianas within range of B-29 attacks. The Joint Chiefs of Staff agreed in December 1943 to seize the Marianas.

US forces invaded Saipan on 15 June 1944. Despite a Japanese naval counterattack which led to the Battle of the Philippine Sea and heavy fighting on land, Saipan was secured by 9 July. Operations followed against Guam and Tinian, with all three islands secured by August. Naval construction battalions (Seabees) began at once to construct air bases suitable for the B-29, commencing even before the end of ground fighting. In all, five major airfields were built: two on the flat island of Tinian, one on Saipan, and two on Guam. Each was large enough to eventually accommodate a bomb wing consisting of four bomb groups, giving a total of 180 B-29s per airfield. These bases could be supplied by ship and, unlike the bases in China, were not vulnerable to attack by Japanese ground forces.

The bases became the launch sites for the large B-29 raids against Japan in the final year of the war. 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 73rd Bomb Wing launched the first mission against Japan from bases in the Marianas, on 24 November 1944, sending 111 B-29s to attack Tokyo. For this first attack on the Japanese capital since the Doolittle Raid in April 1942, 73rd Bomb Wing wing commander Brigadier General Emmett O'Donnell Jr. acted as mission command pilot in B-29 Dauntless Dotty.

The campaign of incendiary raids started with the bombardment of Kobe on 4 February 1945, then peaked early with the most destructive bombing raid in history (even when the later Silverplate-flown nuclear attacks on Hiroshima and Nagasaki are considered) on the night of 9–10 March 1945 on Tokyo. From then on, the raids intensified, being launched regularly until the end of the war. The attacks succeeded in devastating most large Japanese cities (with the exception of Kyoto and four that were reserved for nuclear attacks), and gravely damaged Japan's war industries. Although less publicly appreciated, the mining of Japanese ports and shipping routes (Operation Starvation) carried out by B-29s from April 1945 reduced Japan's ability to support its population and move its troops.

Nuclear weapons

The most famous B-29s were the Silverplate series, being extensively modified to carry nuclear weapons. Early consideration was given to using the British Lancaster as a nuclear bomber, as this would require less modification. However, the superior range and high-altitude performance of the B-29 made it a much better choice, and after the B-29 began to be modified in November 1943 for carrying the atomic bomb, the suggestion for using the Lancaster never came up again.

The most significant modification was the enlargement of the bomb bay enabling each aircraft to carry either the Little Boy or Fat Man weapons. These Silverplate bombers differed from other B-29s then in service by having fuel injection and reversible props. Also, to make a lighter aircraft, the Silverplate B-29s were stripped of all guns, except for those on the tail. Pilot Charles Sweeney credits the reversible props for saving Bockscar after making an emergency landing on Okinawa following the Nagasaki bombing.

Enola Gay, flown by Colonel Paul Tibbets, dropped the first bomb, called Little Boy, on Hiroshima on 6 August 1945. Enola Gay is fully restored and on display at the Smithsonian's Steven F. Udvar-Hazy Center, outside Dulles Airport near Washington, D.C. Bockscar, piloted by Major Charles W. Sweeney, dropped the second bomb, called Fat Man, on Nagasaki three days later. Bockscar is on display at the National Museum of the United States Air Force.

Following the surrender of Japan, called V-J Day, B-29s were used for other purposes. A number supplied POWs with food and other necessities by dropping barrels of rations on Japanese POW camps. In September 1945, a long-distance flight was undertaken for public relations purposes: Generals Barney M. Giles, Curtis LeMay, and Emmett O'Donnell Jr. piloted three specially modified B-29s from Chitose Air Base in Hokkaidō to Chicago Municipal Airport, continuing to Washington, D.C., the farthest nonstop distance (6,400 miles or 10,300 kilometers) to that date flown by US Army Air Forces aircraft and the first-ever nonstop flight from Japan to Chicago. Two months later, Colonel Clarence S. Irvine commanded another modified B-29, Pacusan Dreamboat, in a world-record-breaking long-distance flight from Guam to Washington, D.C., traveling 7,916 miles (12,740 km) in 35 hours, with a gross takeoff weight of 155,000 pounds (70,000 kg). Almost a year later, in October 1946, the same B-29 flew 9,422 miles (15,163 km) nonstop from Oahu, Hawaii, to Cairo, Egypt, in less than 40 hours, demonstrating the possibility of routing airlines over the polar ice cap.

B-29s in Europe and Australia

Although considered for other theaters, and briefly evaluated in the UK, the B-29 was exclusively used in World War II in the Pacific Theatre. The use of YB-29-BW 41-36393, the so-named Hobo Queen, one of the service test aircraft flown around several British airfields in early 1944, was part of a "disinformation" program from its mention in an American-published Sternenbanner German-language propaganda leaflet from Leap Year Day in 1944, meant to be circulated within the Reich, with the intent to deceive the Germans into believing that the B-29 would be deployed to Europe.

American post-war military assistance programs loaned the RAF 87 Superfortresses, to equip eight RAF Bomber Command squadrons. The aircraft was known as the Washington B.1 in RAF service and served from March 1950 until the last bombers were returned in March 1954. Deployment was restricted to long-range training for strategic attacks against the Soviet Union, which was beyond the range of the RAF's Avro Lincolns. The phase-out was occasioned by deliveries of the English Electric Canberra bombers.

Three Washingtons modified for ELINT duties and a standard bomber version used for support by No. 192 Squadron RAF were decommissioned in 1958, being replaced by de Havilland Comet aircraft. Two British Washington B.1 aircraft were transferred to the Royal Australian Air Force (RAAF) in 1952. They were attached to the Aircraft Research and Development Unit and used in trials conducted on behalf of the British Ministry of Supply. Both aircraft were placed in storage in 1956 and were sold for scrap in 1957.

Soviet Tupolev Tu-4

At the end of World War II, Soviet development of modern four-engine heavy bombers lagged behind the West. The Petlyakov Pe-8—the sole heavy bomber operated by the Soviet Air Forces—first flew in 1936. Intended to replace the obsolete Tupolev TB-3, only 93 Pe-8s were built by the end of WWII. During 1944 and 1945, four B-29s made emergency landings in Soviet territory after bombing raids on Japanese Manchuria and Japan. In accordance with Soviet neutrality in the Pacific War, the bombers were interned by the Soviets despite American requests for their return. Rather than return the aircraft, the Soviets reverse engineered the American B-29s and used them as a pattern for the Tupolev Tu-4.

On 31 July 1944, Ramp Tramp (serial number 42-6256), of the United States Army Air Forces 462nd (Very Heavy) Bomb Group was diverted to Vladivostok, Russia, after an engine failed and the propeller could not be feathered. This B-29 was part of a 100-aircraft raid against the Japanese Showa steel mill in Anshan, Manchuria. On 20 August 1944, Cait Paomat (42-93829), flying from Chengdu, was damaged by anti-aircraft gunfire during a raid on the Yawata Iron Works. Due to the damage it sustained, the crew elected to divert to the Soviet Union. The aircraft crashed in the foothills of Sikhote-Alin mountain range east of Khabarovsk after the crew bailed out. On 11 November 1944, during a night raid on Omura in Kyushu, Japan, the General H. H. Arnold Special (42-6365) was damaged and forced to divert to Vladivostok in the Soviet Union. The crew was interned. On 21 November 1944, Ding How (42-6358) was damaged during a raid on an aircraft factory at Omura and was also forced to divert to Vladivostok. The interned crews of these four B-29s were allowed to escape into American-occupied Iran in January 1945, but none of the B-29s were returned after Stalin ordered the Tupolev OKB to examine and copy the B-29 and produce a design ready for quantity production as soon as possible. Because aluminum in the USSR was supplied in different gauges from that available in the US (metric vs imperial), the entire aircraft had to be extensively re-engineered. In addition, Tupolev substituted his own favored airfoil sections for those used by Boeing, with the Soviets themselves already having their own Wright R-1820-derived 18 cylinder radial engine, the Shvetsov ASh-73 of comparable power and displacement to the B-29's Duplex Cyclone radials available to power their design. In 1947, the Soviets debuted both the Tupolev Tu-4 (NATO ASCC code named Bull), and the Tupolev Tu-70 transport variant. The Soviets used tail-gunner positions similar to the B-29 in many later bombers and transports.

Transition to USAF

Production of the B-29 was phased out after WWII, with the last example completed by Boeing's Renton factory on 28 May 1946. Many aircraft went into storage, being declared excess inventory, and were ultimately scrapped as surplus. Others remained in the active inventory and equipped the Strategic Air Command when it formed on 21 March 1946. In particular, the "Silverplate" modified aircraft of the 509th Composite Group remained the only aircraft capable of delivering the atomic bomb, and so the unit was involved in the Operation Crossroads series of tests, with B-29 Dave's Dream dropping a Fat Man bomb in Test Able on 1 July 1946.

Some B-29s, fitted with filtered air sampling scoops, were used to monitor above-ground nuclear weapons testing by the US and the USSR by sampling airborne radioactive contamination. The USAF also used the aircraft for long-range weather reconnaissance (WB-29), for signals intelligence gathering (EB-29) and photographic reconnaissance (RB-29).

Korean War and postwar service

The B-29 was used in 1950–1953 in the Korean War. At first, the bomber was used in normal strategic bombing day-missions, although North Korea's few strategic targets and industries were quickly destroyed. More importantly, in 1950 numbers of Soviet MiG-15 jet fighters appeared over Korea, and after the loss of 28 aircraft, future B-29 raids were restricted to night missions, largely in a supply-interdiction role. The B-29 dropped the 1,000 lb (450 kg) VB-3 "Razon" (a range-controllable version of the earlier Azon guided ordnance device) and the 12,000 lb (5,400 kg) VB-13 "Tarzon" MCLOS radio-controlled bombs in Korea, mostly for demolishing major bridges, like the ones across the Yalu River, and for attacks on dams. The aircraft also was used for numerous leaflet drops in North Korea, such as those for Operation Moolah.

Over the course of the war, B-29s flew 20,000 sorties and dropped 220,000 short tons (200,000 t) of bombs in Korea. B-29 gunners were credited with shooting down 27 enemy aircraft. In turn 78 B-29s were lost; 57 B-29 and reconnaissance variants were lost in action and 21 were non-combat losses. Soviet records show that one MiG-15 jet fighter was shot down by a B-29 during the war. This occurred on 6 December 1950, when a B-29 shot down Lieutenant N. Serikov. A Superfortress of the 91st Strategic Reconnaissance Squadron flew the last B-29 mission of the war on 27 July 1953.

With the arrival of the mammoth Convair B-36, the B-29 was reclassified as a medium bomber by the Air Force. The later B-50 Superfortress variant (initially designated B-29D) was able to handle auxiliary roles such as air-sea rescue, electronic intelligence gathering, air-to-air refueling, and weather reconnaissance. The B-50D 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 KB-50 and WB-50 variants were phased out in the mid-1960s, with the final example retired in 1965. A total of 3,970 B-29s were built.

Variants

The variants of the B-29 were outwardly similar in appearance but were built around different wing center sections that affected the wingspan dimensions. The wing of the Renton-built B-29A-BN used a different subassembly process and was a foot longer in span. The Georgia-built B-29B-BA weighed less through armament reduction. A planned C series with more reliable R-3350s was not built. Moreover, engine packages changed, including the type of propellers and range of the variable pitch. A notable example was the eventual 65 airframes (up to 1947's end) for the Silverplate and successor-name "Saddletree" specifications built for the Manhattan Project with Curtiss Electric reversible pitch propellers.

The Silverplate aircraft had significantly modified electronics and armament. The jammers were removed and replaced with additional AN/APR-4 radio frequency monitoring equipment, because the atomic bombs used a modified tail radar for a radar altimeter, and the lack of delayed arming could cause unintended detonation immediately after release. This was due to the C-3A release mechanism arming the weapon immediately upon release with no delay, making it absolutely necessary to monitor the frequencies used by the radar altimeters. Targeting was accomplished using a license built version of the British H2S, designated the AN/APQ-13 in American service. This provided both guidance and targeting, as well as timing the bomb release precisely.

The other differences came through added equipment for varied mission roles. These roles included cargo carriers (CB); rescue aircraft (SB); weather ships (WB); and trainers (TB); and aerial tankers (KB). Some were used for odd purposes such as flying relay television transmitters under the name of Stratovision. Another role was as a mothership. This included being rigged for carrying the experimental parasite fighter aircraft, such as the McDonnell XF-85 Goblin and Republic F-84 Thunderjets as in flight lock on and offs. It was also used to develop the Airborne Early Warning program; it was the ancestor of various modern radar picket aircraft. A B-29 with the original Wright Duplex Cyclone powerplants was used to air-launch the Bell X-1 supersonic research rocket aircraft, as well as Cherokee rockets for the testing of ejection seats.

The B-29D led progressively to the XB-44, and the family of B-50 Superfortress (which was powered by four 3,500 hp (2,600 kW) Pratt & Whitney R-4360-35 Wasp Major engines). Some B-29s were modified to act as testbeds for various new systems or special conditions, including fire-control systems, cold-weather operations, and various armament configurations. Several converted B-29s were used to experiment with aerial refueling and re-designated as KB-29s. Perhaps the most important tests were conducted by the XB-29G. It carried prototype jet engines in its bomb bay, and lowered them into the air stream to conduct measurements.

Operators

Australia

• Royal Australian Air Force (two former RAF aircraft for trials)

United Kingdom

• Royal Air Force (87 loaned from the USAF as the Washington B.1)

United States

• United States Army Air Forces
• United States Air Force
• United States Navy (four former USAF aircraft designated as P2B patrol bombers)

Soviet Union

• Soviet Air Forces (three USAAF B-29s made emergency landings in the USSR during WWII, and were never returned; they were reverse-engineered to make the Soviet Tupolev Tu-4 "Bull" bomber.)

Surviving aircraft

Twenty-two B-29s are preserved at various museums worldwide, including two flying examples; FIFI, which belongs to the Commemorative Air Force, and Doc, which belongs to Doc's Friends. Doc made its first flight in 60 years from Wichita, Kansas, on 17 July 2016. The public is being invited to inspect and take a short paid flight in Doc and Fifi at various venues.

Three of the Silverplate B-29s modified to drop nuclear bombs survived. Superfortress 44-86292 Enola Gay (nose number 82), which dropped the first atomic bomb, was fully restored and placed on display at the Smithsonian's Steven F. Udvar-Hazy Center of the National Air & Space Museum near Washington Dulles International Airport in 2003. The B-29 that dropped Fat Man on Nagasaki, Superfortress 44-27297 Bockscar (nose number 77), is restored and on display at the National Museum of the United States Air Force at Wright-Patterson AFB in Dayton, Ohio, posed with a replica of the Mark 3 Fat Man nuclear bomb. The third is Superfortress 45-21748, which was delivered on 9 August 1945 and is on display at the National Museum of Nuclear Science and History in Albuquerque, New Mexico.

Only two of the twenty-two museum aircraft are outside the United States: It's Hawg Wild at the Imperial War Museum Duxford and another at the KAI Aerospace Museum in Sachon, South Korea.

Accidents and incidents

Notable accidents and incidents involving B-29s include:

• The 1947 crash of the Kee Bird in Greenland during a flight to the geographic North Pole, and its subsequent destruction in 1995 during a recovery attempt.
• The 1948 Waycross B-29 crash, which resulted in the United States v. Reynolds lawsuit regarding state secrets privilege.
• The 1948 Lake Mead Boeing B-29 crash during the "Sun Tracker" project that aimed to develop an intercontinental ballistic missile guidance system that used the sun for direction and positioning.
• The 3 November 1948 crash at Bleaklow moor near Glossop, Derbyshire, England. Much of the wreckage is still exposed and can be reached by a 2 miles (3.2 km) walk from the summit of Snake Pass, starting along the Pennine Way footpath through Devil's Dyke.
• On 11 April 1950 a B-29 departed Kirtland Air Force Base and crashed into a mountain on Manzano Base approximately three minutes later, killing the crew. Detonators were installed in the nuclear bomb on the aircraft. The bomb case was demolished and some high-explosive (HE) material burned in the fire. Both the weapon and the capsule of nuclear material were on board but the capsule was not inserted in the bomb for safety reasons, so no nuclear detonation was possible.
• On 5 August 1950, a B-29 carrying a Mark 4 nuclear bomb crashed shortly after takeoff from Fairfield-Suisun Air Force Base with 20 men on board. Twelve men were killed in the crash, including Brigadier General Robert F. Travis, and another seven on the ground when the aircraft exploded. The base was later renamed after Travis.

Specifications

Data from Quest for Performance

General characteristics

• Crew: 11 (Pilot, co-pilot, bombardier, flight engineer, navigator, radio operator, radar observer, right gunner, left gunner, central fire control, tail gunner)
• 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 ft² (3.824 m²)
• Empty weight: 74,500 lb (33,793 kg)
• Gross weight: 120,000 lb (54,431 kg)
• Max takeoff 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 turbosupercharged 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:
  • 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 miles (2,600 km; 1,400 nmi) radius at high altitude
  • 12,000 lb (5,400 kg) over 1,600 miles (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, or one 44,600 pound T-12 Cloudmaker deep penetration bomb.
  • Mark I, Mark III, Mark 4 and Mark 6 nuclear bombs (only Silverplate versions of the aircraft).

Notable appearances in media