Tag Archives: NMUSAF

9 August 1945

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Martin-Omaha B-29-35-MO Superfortress 44-27297, Bockscar, at the National Museum of the United States Air Force. The “nose art” was added after the 9 August mission. Note the 509th’s “Circle Arrow” tail insignia. This was replaced by a “Triangle N” marking for the actual bombing mission. (U.S. Air Force)

9 August 1945: Three days after an atomic bomb had been used against the Japanese industrial city of Hiroshima, a second attack was made on Nagasaki. Major Charles W. Sweeney,¹ in command of the Martin-Omaha B-29-35-MO Superfortress 44-27297, named Bockscar, departed Tinian Island in the Marshal Group at 3:47 a.m., and flew to Iwo Jima where it was to rendezvous with two other B-29s, The Great Artiste and The Big Stink, the instrumentation and photographic aircraft for this mission.

Like its sistership, Enola Gay, 44-27297 was a specially modified “Silverplate” B-29. The Silverplate B-29s differed from the standard production bombers in many ways. They were approximately 7,200 pounds (3,266 kilograms) lighter. The bomber carried no armor. Additional fuel tanks were installed in the rear bomb bay. The bomb bay doors were operated by quick-acting pneumatic systems. The bomb release mechanism in the forward bomb bay was replaced by a single-point release as was used in special British Lancaster bombers. A weaponeer’s control station was added to the cockpit to monitor the special bomb systems.

Bockscar had four air-cooled, supercharged, 3,347.662-cubic-inch-displacement (54.858 liter) Wright Aeronautical Division R-3350-41 (Cyclone 18 787C18BA3) two-row 18-cylinder radial engines with direct fuel injection. The R-3350-41 had a compression ratio of 6.85:1 and required 100/130 aviation gasoline. It was rated at 2,000 horsepower at 2,400 r.p.m. at Sea Level, and 2,200 horsepower at 2,800 r.p.m, for take-off. The engines drove four-bladed Curtiss Electric reversible-pitch propellers with a diameter of 16 feet, 8 inches (5.080 meters), through a 0.35:1 gear reduction. The R-3350-41 was 6 feet, 2.26 inches (1.937 meters) long, 4 feet, 7.78 inches (1.417 meters) in diameter and weighed 2,725 pounds (1,236 kilograms).

With the exception of the tail gunner’s position, all defensive armament—four powered remotely operated gun turrets with ten .50-caliber machine guns—were deleted. Their remote sighting positions were also removed. Enola Gay carried 1,000 rounds of ammunition for each of the two remaining Browning AN-M2 .50-caliber machine guns in the tail.

With these changes, the Silverplate B-29s could fly higher and faster than a standard B-29, and the fuel-injected R-3350-41 engines were more reliable. Bockscar had a cruising speed of 220 miles per hour (354 kilometers per hour) and a maximum speed of 365 miles per hour (587 kilometers per hour). Its service ceiling was 31,850 feet (9,708 meters) and its combat radius was 2,900 miles (4,667 kilometers).

Martin-Omaha B-29-35-MO Superfortress 44-27297, Bockscar, in flight. Note "Triangle N" tail code. (U.S. Air Force)
Martin-Omaha B-29-35-MO Superfortress 44-27297, Bockscar, in flight. Note the “Triangle N” tail code. (U.S. Air Force)

44-27297, Victor 7, was assigned to aircraft commander Captain Frederick C. Bock and his crew. Major Sweeney and his crew ordinarily flew The Great Artiste. Sweeney’s B-29 had been the the instrumentation aircraft for the Hiroshima mission and there was not time to remove that equipment and re-install it aboard Bock’s bomber, so the crews switched airplanes. For operational security, Bockscar‘s normal identification was changed from the number 7 on the fuselage to 77. The 509th’s tail code of a circle surrounding a forward-pointing arrow was changed to another unit’s “Triangle N” identification.

All of these last minute changes resulted in confusion in contemporary reports as to which B-29 had actually dropped Fat Man on Nagasaki.

Boeing B-29 crew photo taken Aug. 11, 1945, two days after the Nagasaki mission. Note there is no nose art on the aircraft. (U.S. Air Force photo)
Major Charles W. Sweeney’s B-29 crew. (U.S. Air Force)

In Bockscar‘s forward bomb bay was a 10,213 pound (4,632 kilograms) bomb called Fat Man. This was a completely different and much more complex weapon than the Little Boy (Mark I) atomic bomb dropped by Colonel Paul Tibbet’s Enola Gay on 6 August. The bomb was 12 feet, 8⅜ inches ¹ (3.261 meters) long, 5 feet, ¼ inch ² (1.530 meters) in diameter,

Designated Mark III, the egg-shaped weapon contained a 9.17 centimeter (3.61 inches), 6.15 kilogram (13.6 pound) sphere of Plutonium Pu 239, with a 2.1 centimeter (0.83 inch) hollow cavity at its center. A beryllium neutron initiator was in this cavity. The plutonium sphere was surrounded by a 22.86 centimeter (9.0 inch) diameter uranium tamper with a mass of 108 kilograms (238 pounds). This nuclear assembly was contained in a boron/acrylic shell and surrounded by about 2,390 kilograms (5,269 pounds) of high-explosive, consisting of Composition B and Baratol. The explosives were formed in “lenses” that would direct the force inward in a very precise manner. The purpose was to compress—or implode— the Plutonium to a much greater density, resulting in a “critical mass.”

The Mark III "Fat Man" bomb loaded on its carrier, 8 August 1945.
The Mark III “Fat Man” bomb being loaded onto its carrier, 8 August 1945.

In the conduct of this mission, Major Sweeney made a number of serious errors that nearly caused the mission to fail, and might very well have led to the loss of the bomber and its crew.

Prior to takeoff, the B-29’s crew chief informed Sweeney that a fuel transfer pump was inoperative which made it impossible to transfer 625 gallons (2,366 liters) of fuel from one fuel tank. This meant that nearly 9% of the total fuel load of 7,250 gallons (27,444 liters) was unusable. Chuck Sweeney decided to go anyway.

Next, though under direct orders from the 509th Composite Group commander, Colonel Paul Tibbets, to wait at the rendezvous no more than 15 minutes, when The Big Stink failed to arrive on schedule, Sweeney elected to stay 30 minutes beyond that.

Meanwhile, the two weather reconnaissance B-29s, Enola Gay and Laggin’ Dragon, were over Kokura, the primary target, and the secondary, Nagasaki. Weather over both cities were within the mission parameters.

XX Bomber Command Target Chart for Nagasaki Area. (National Archives)

During the 45 minutes that Sweeney waited at the rendezvous, weather over Kokura had deteriorated. By the time Bockscar arrived overhead, clouds covered the city. The bomber made three attempts to bomb the city over a 50-minute period, but the bombardier was not able to see the target.

Now an hour and twenty minutes behind schedule, Sweeney diverted to the secondary target, Nagasaki. Because of the delays and the unusable fuel as a result of the failed fuel pump, Sweeney reduced engine power to try to conserve fuel during the twenty minute flight to the alternate target. But weather there had also deteriorated.

Sweeney decided that they should bomb through the clouds using radar, but at the last minute, the bombardier was able to see the aim point. The Fat Man was dropped from 30,000 feet (9,144 meters) at 11:01 a.m. After falling for 43 seconds, the atomic bomb detonated at an altitude of 1,950 feet (594 meters). It missed the intended target point by nearly 1.5 miles (2.4 kilometers) and exploded over the Urakami Valley, halfway between the Mitsubishi Steel and Arms Works and the Mitsubishi-Urakami Ordnance Works.

Nagasaki, 9 August 1945, photographed by Joe Kosstatscher, U.S. Navy.
Nagasaki, 9 August 1945, photographed by Joe Kosstatscher, U.S. Navy.

The estimated force of the explosion was 21 kilotons—equivalent to the explosive force of 21,000 tons of TNT (19,050 metric tons)—nearly 20% greater than the Hiroshima bomb. The surrounding hills contained the explosion, protecting a large part of the city. Still, approximately 60% of Nagasaki was destroyed and 70,000 people were killed. By December 1945, at least 80,000 of the city’s 250,000 residents had died.

Atomic cloud rising over nagasaki, japan, 9 August 1945, photographed from Koyagi-jima. (Hiromichi Matsuda)
Pyrocumulus cloud rising over Nagasaki, Japan, approximately 20 minutes after detonation, 9 August 1945, photographed from Koyagi-jima, a small island southwest of Nagasaki. (Hiromichi Matsuda)
Nagasaki. (Bridgeman Images)

Now critically low on fuel and unable to reach the emergency B-29 recovery field on Iwo Jima, Sweeney headed for the airfields of Okinawa. When Bockscar touched down on the runway, one engine quit due to fuel starvation. As they turned off the runway, a second engine ran out of fuel. Charles Sweeney had cut it very, very close.

B-29 44-27297 on Tinian Island, August 1945. The nose art was applied to the airplane after the August 9, 1945 bombing mission. (U.S. Air Force)
Martin-Omaha B-29-35-MO 44-27297 on Tinian Island, August 1945. The nose art was applied to the airplane after the August 9, 1945 bombing mission. (U.S. Air Force)

Five days after the bombing of Nagasaki, the Emperor of Japan—recognizing that his country now faced total destruction—agreed to surrender. World War II was over.

In 1946, Bockscar was placed in storage at Davis-Monthan Army Air Field, Tucson, Arizona. On 26 September 1961, the B-29 was flown to the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Dayton, Ohio, where it remains in the museum’s collection of historic aircraft.

DAYTON, Ohio — Boeing B-29 Superfortress “Bockscar” at the National Museum of the United States Air Force. (U.S. Air Force photo)

¹ The other members of the crew of Bockscar were Captain Charles Donald Albury, co-pilot; Second Lieutenant Frederick John Olivi, co-pilot; Captain James Frederick Van Pelt, Jr., navigator; Captain Kermit King Beahan, bombardier; Master Sergeant John Donald Kuharek, flight engineer; Staff Sergeant Raymond C. Gallagher, assistant flight engineer; Staff Sergeant Edward Kenneth Buckley, radar operator; Sergeant Abe M. Spitzer, radio operator; Sergeant Albert Travis Dehart, tail gunner; Commander Frederick Lincoln (“Dick”) Ashworth, U.S. Navy, weaponeer; Lieutenant Philip M. Barnes, U.S. Navy, assistant weaponeer; First Lieutenant Jacob Beser, radar countermeasures. (Lieutenant Beser also flew aboard Enola Gay, 6 August 1945.)

© 2023, Bryan R. Swopes

30 June 1975

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The last operational U.S. Air Force C-47 Skytrain, 43-49507, on display at NMUSAF. (U.S. Air Force)

30 June 1975: The last operational Douglas C-47 Skytrain transport in service with the United States Air Force, 43-49507, was retired and flown to the National Museum of the United States Air Force at Wright-Patterson Air Force Base, Ohio.

A C-47D, it is on display in the World War II Gallery, painted and marked as C-47A-80-DL 43-15213 of the 91st Troop Carrier Squadron, 439th Troop Carrier Group, during World War II. At the time it was withdrawn from service, 43-49507 had flown a total of 20,831 hours.

43-49507 (Douglas serial number 26768) was built at Oklahoma City as a C-47B-15-DK Skytrain. The C-47B differed from the C-47A in that it was powered by Pratt & Whitney Twin Wasp S3C4-G (R-1830-90) engines. These engines were equipped with two-speed superchargers for improved high-altitude performance. Following World War II, the second speed (“high blower”) was either disabled or removed. Following this modification, the airplane was redesignated C-47D.

A group of new Douglas C-47 Skytrains. The airplane closest to the camera is C-47-DL 41-18415. (Douglas Aircraft Company)

The Douglas C-47 Skytrain is a military transport variant of the Douglas Aircraft Company DC-3 commercial airliner. It is an all-metal, twin-engine, low-wing monoplane with retractable landing gear. It was operated by a minimum flight crew of two pilots, navigator, radio operator and mechanic/load master. The airplane’s control surfaces are covered with doped-fabric. The primary differences between the civil DC-3 and military C-47 was the addition of a cargo door on the left side of the fuselage, a strengthened cargo floor, a navigator’s astrodome and provisions for glider towing.

The DC-3 made its first flight 17 December 1935, while the C-47 flew for the first time six years later, 23 December 1941.

Two Douglas C-47 Skytrains. Nearest the camera is C-47A-90-DL 43-15661. The further airplane is C-47A-65-DL 42-100550. (U.S. Air Force)

The C-47 is 64 feet, 5½ inches (19.647 meters) long with a wingspan of 95 feet (28.956 meters) and height of 17 feet (5.182 meters). The total wing area is 988.9 square feet (91.872 square meters). The angle of incidence is 2°. The wing center section is straight, but outboard of the engine nacelles there is 5º dihedral. The wings’ leading edges are swept aft 15.5°. The trailing edges have no sweep.  Empty weight of the C-47D is 17,865 pounds (8,103 kilograms) and the maximum takeoff weight is 33,000 pounds (14,969 kilograms).

The C-47A was powered by two 1,829.4-cubic-inch-displacement (29.978 liter) air-cooled, supercharged R-1830-92 (Pratt & Whitney Twin Wasp S1C3-G) two-row 14-cylinder radial engines with a compression ratio of 6.7:1. These were rated at 1,060 horsepower at 2,550 r.pm., up to 7,500 feet (2,286 meters), maximum continuous power, and 1,200 horsepower at 2,700 r.p.m. at Sea Level for takeoff. Each engine drives a three-bladed Hamilton Standard Hydromatic constant-speed full-feathering propeller with a diameter of 11 feet, 6 inches (3.505 meters) through a 16:9 gear reduction. The R-1830-92 is 48.19 inches (1.224 meters) long, 61.67 inches (1.566 meters) in diameter, and weighs 1,465 pounds (665 kilograms).

U.S. Army paratroopers jump from Douglas C-47-DL Skytrain 41-7805, over England, May 1944. (U.S. Air Force)

The specifications of the  Pratt & Whitney Twin Wasp S3C4-G (R-1830-90) installed on the C-47B and C-47D were nearly the same as the -92 engine of the C-47A. Displacement and compression ratio were identical. The engines’ diameters were the same, though the -90 was very slightly longer than the -92—1.85–2.74 inches (4.699–6.960 centimeters), depending on specific variant. Also, the -90 was heavier than the -92 by 25–30 pounds (11.34–13.61 kilograms), again, depending on the specific variant. The R-1830-90 could maintain 1,000 horsepower at 2,550 r.p.m. at 12,500 feet (3,810 meters), and 1,000 horsepower at 2,700 r.p.m. at 14,000 feet (4,267 meters), a significant increase over the -92.

The C-47D has a cruising speed of 161 knots (185 miles per hour/298 kilometers per hour) at 10,000 feet (3,048 meters), and maximum speed of 202 knots (232 miles per hour/374 kilometers per hour) at 3,500 feet (1,067 meters). Its service ceiling was 22,150 feet (6,751 meters). The Skytrain had a maximum range of 1,026 nautical miles (1,181 miles/1,900 kilometers) with full cargo.

The C-47 could carry 9,485 pounds (4,302 kilograms) of cargo, or 27 fully-equipped paratroopers. Alternatively, 24 patients on stretchers could be carried, along with two attendants.

C-47 Skytrains in Vee-of Vees formation.

On D-Day, The Sixth of June, 1944, a formation of C-47 Skytrains, nine airplanes abreast, 100 feet (30 meters) from wing tip to wing tip, 1,000 feet (305 meters) in trail, stretching for over 300 miles (483 kilometers), airdropped 13,348 paratroopers of the 82nd and 101st Airborne Divisions, United States Army, and another 7,900 men of the British Army 6th Airborne Division and the 1st Canadian Parachute Battalion, behind the beaches at Normandy, France.

During the Vietnam War, 53 C-47s were converted from their transport role to AC-47 Spooky gunships. These were armed with three fixed, electrically-powered General Electric  GAU-2/A .30-caliber (7.62 NATO) Gatling guns firing out the left side of the fuselage. These aircraft were highly effective at providing close air support. The three Miniguns could fire a total of 12,000 rounds per minute.

Douglas AC-47D Spooky gunship, 45-0927, 4th Special Operations Squadron, Nha Trang, Republic of Vietnam, September 1968. (U.S. Air Force)
Douglas DC-3 (C-47B) three-view drawing. (NASA)

Douglas Aircraft Company built 10,174 C-47 Skytrains at its factories in Santa Monica and Long Beach, California, and at Oklahoma City, Oklahoma.

© 2018, Bryan R. Swopes

30 April 1959

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Convair B-36J-1-CF 52-2220 at NMUSAF, Wright-Patterson AFB, Ohio.

30 April 1959: Convair B-36J-1-CF Peacemaker, serial number 52-2220, landed at Wright-Patterson Air Force Base, Dayton, Ohio, completing the very last flight ever made by one of the giant Cold War-era bombers. It is on the collection of the National Museum of the United States Air Force.

Convair B-36J 52-2220 was among the last group of 33 B-36 bombers built. It was operated by an aircraft commander/pilot, co-pilot, two navigators, bombardier, two flight engineers, two radio operators, two electronic countermeasures operators and five gunners, a total 16 crewmembers. Frequently a third pilot and other additional personnel were carried.

Crewmebers pose in front of a B-36F, wearing capstan-type partial pressure suites for protection at high altitude. Front (L-R): G.L. Whiting, B.L. Woods, I.G. Hanten, and R.L. D’Abadie. Back (L-R):A.S. Witchell, J.D. McEachern, J.G. Parker and R. D. Norvell. (Jet Pilot Overseas)
Crew members pose in front of a Convair B-36F-1-CF Peacemaker, 49-2669, wearing David Clark Co. S-2 capstan-type partial pressure suits and early K-1 “split shell” 2-piece helmets for protection at high altitude. Front (L-R): G.L. Whiting, B.L. Woods, I.G. Hanten, and R.L. D’Abadie. Back (L-R):A.S. Witchell, J.D. McEachern, J.G. Parker and R. D. Norvell. (Jet Pilot Overseas)

The bomber is 162 feet, 1 inch (49.403 meters) long with a wingspan of 230 feet (70.104 meters) and overall height of 46 feet, 9 inches (14.249 meters). The empty weight is 171,035 pounds (77,580 kilograms) and combat weight is 266,100 pounds (120,700 kilograms). Maximum takeoff weight is 410,000 pounds (185,973 kilograms).

The B-36J has ten engines. There are six air-cooled, supercharged 4,362.49 cubic-inch-displacement (71.49 liter) Pratt & Whitney Wasp Major C6 (R-4360-53) four-row, 28-cylinder radial engines placed inside the wings in a pusher configuration. These had a compression ratio of 6.7:1 and required 115/145 aviation gasoline. The R-4360-53 had a Normal Power rating of 2,800 horsepower at 2,600 r.p.m. Its Military Power rating was 3,500 horsepower at 2,800 r.p.m., and 3,800 horsepower at 2,800 r.p.m. with water injection—the same for Takeoff. The engines turned three-bladed Curtiss Electric constant-speed, reversible propellers with a diameter of 19 feet, 0 inches (5.791 meters) through a 0.375:1 gear reduction. The R-4360-53 is 9 feet, 9.00 inches (2.972 meters) long, 4 feet, 7.00 inches (1.397 meters) in diameter, and weighs 4,040 pounds (1,832.5 kilograms).

Four General Electric J47-GE-19 turbojet engines are suspended under the wings in two-engine pods. The J47 is a  single-shaft axial-flow turbojet engine with a 12-stage compressor section, 8 combustion chambers, and single-stage turbine. The J47-GE-19 was modified to run on gasoline and was rated at 5,200 pounds of thrust (23.131 kilonewtons).

The B-36J had a cruise speed of 203 miles per hour (327 kilometers per hour) and a maximum speed of 411 miles per hour (661 kilometers per hour) at 36,400 feet (11,905 meters) . The service ceiling was 39,900 feet (12,162 meters) and its range was 6,800 miles (10,944 kilometers) with a 10,000 pound (4,536 kilogram) bomb load. The maximum range was 10,000 miles (16,093 kilometers).

Convair B-36J-1-CF Peacemaker 52-2220. (San Diego Air and Space Museum Archives)

Designed during World War II, nuclear weapons were unknown to the Consolidated-Vultee engineers. The bomber was built to carry up to 86,000 pounds (39,009 kilograms) of conventional bombs in two bomb bays. It could carry the 43,600 pound (19,776.6 kilogram) T-12 Cloudmaker, a conventional explosive earth-penetrating bomb, or several Mk.15 thermonuclear bombs. By combining the bomb bays, one Mk.17 25-megaton thermonuclear bomb could be carried.

For defense, the B-36J had six retractable defensive gun turrets and gun turrets in the nose and tail. All 16 guns were remotely operated. Each position mounted two M24A1 20 mm autocannons. 9,200 rounds of ammunition were carried.

Convair B-36 Peacemakers at Davis-Monthan AFB, Tucson, Arizona. (U.S. Air Force)

Between 1946 and 1954, 384 B-36 Peacemakers were built. They were never used in combat. Only five still exist.

Convair B-36J-1-CF 52-2220 being moved from Building 1 to Building 3 at the National Museum of the United States Air Force, October 2002. (U.S. Air Force)

© 2017, Bryan R. Swopes