Operation Teapot HA fireball, 6 April 1955. (U.S. Air Force)
6 April 1955: At 10:00:04.1 a.m. local time (1800 GMT), a Convair B-36H assigned to the 4925th Test Group (Atomic) at Kirtland Air Force Base, New Mexico dropped an atomic weapon from 42,000 feet (12,802 meters) over the Nevada Test Site, Area 1. The bomb was parachute-retarded to slow its fall so that the bomber could escape its blast effects.
The weapon was a test device produced by the Los Alamos Scientific Laboratory to investigate its use as an air-to-air anti-aircraft missile warhead. The bomb detonated at 36,620 feet (11,162 meters) with an explosive force of 3.2 kilotons. Because of the altitude of the explosion, there was no significant fallout.
All test observers (with goggles) agreed that the fireball appeared more intensely bright than in events of similar yield fired at lower altitude.
—United States High-Altitude Test Experiences by Herman Hoerlin, Los Alamos Scientific Laboratory, June 1976, at Page 12.
Captain William L. Hickey, USAF, pilot of a Convair B-36 Peacemaker very long-range heavy bomber during Operation Teapot, 1955. Captain Hickey is wearing a David Clark Co. S-2 capstan-type partial-pressure suit and K-1 helmet for protection at high altitude. (Jet Pilot Overseas)
The warhead was designed at the Los Alamos Scientific Laboratory (LASL) in New Mexico and was similar to the Wasp Prime device, which had been detonated earlier in the Operation Teapot test series. It used a spherical implosion system. The warhead was a 17-inch (43.2 centimeters) diameter sphere weighing approximately 125 pounds (56.7 kilograms). It was placed inside a Mark 5 bomb case which weighed 1,085 pounds (492.2 kilograms).
This was the only bomb dropped by parachute at the Nevada Test Site.
Flight crew of a Convair B-36 Peacemaker, 4925th Test Group (Atomic) during Operation Teapot, 1955. The crewmen are wearing David Clark Co. S-2 capstan-type partial-pressure suits for protection at high altitude. The two white helmets are early K-1 “split shell” two-piece helmets, while the green helmets are later K-1 one-piece models. (Jet Pilot Overseas)
The Convair B-36H Peacemaker was the definitive version of the ten engine bomber, with 156 B-36H/RB-36H built out of the total production of 383 Peacemakers. It is similar to the previous B-36F variant, though with a second flight engineer’s position, a revised crew compartment, and improved radar controlling the two 20 mm autocannons in the tail turret.
The B-36H was 162 feet, 1 inch (49.403 meters) long with a wingspan of 230 feet (70.104 meters) and overall height of 46 feet, 8 inches (14.224 meters). The total area of its wings was 4,772 square feet (443.3 square meters). The wings’ leading edges were swept aft 15° 5′ 39″. Their angle of incidence was 3°, with -2° twist and 2° dihedral. The empty weight of the B-36H was 165,887pounds (75,245 kilograms) and the maximum takeoff weight is 357,500 pounds (162,159 kilograms).
Three flight crewmen don their parachutes before boarding the B-36H Peacemaker for Operation Teapot HA, 5 April 1955. The automobile behind them is a 1955 Chevrolet Bel Air 4-door sedan. (U.S. Air Force)
The B-36H 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).
A smoke ring formed following the detonation of the Operation Teapot HA test. Contrails of the test aircraft are visible. (U.S. Air Force)
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-36H was the fastest variant of the Peacemaker series, with a cruise speed of 216 knots (249 miles per hour/400 kilometers per hour) and a maximum speed of 382 knots (440 miles per hour/707 kilometers per hour) at 35,500 feet (10,820 meters). The service ceiling was 47,000 feet (14,326 meters) and its combat radius was 3,190 nautical miles (3,671 statute miles/5,908 kilometers). The ferry range was 7,120 nautical miles (8,194 statute miles/13,186 kilometers).
Convair RB-36H-40-CF 51-13741 Featherweight III. (U.S. Air Force)
The B-36H has six remotely-controlled retractable gun turrets mounting two M24A1 20 mm autocannon, each, with 600 rounds of ammunition per gun. The tail turret was radar-controlled, and another 2 guns were mounted in the nose.
The B-36 was designed during World War II, when nuclear weapons were unknown to the manufacturer. The bomber was built to carry up to 86,000 pounds (39,009 kilograms) of conventional bombs in fours bomb bays. It could carry two 43,000 pound ( kilogram) T-12 Cloudmakers, 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.
This Convair RB-36D-5-CF, 49-2686, is similar in appearance to the B-36H used in Operation Teapot HA. (U.S. Air Force)
Lieutenant Stewart R. Graham, USCG, in cockpit of Sikorsky HNS-1 near Gander, Newfoundland, September 1946. (U.S. Coast Guard)
April 6, 1949: Lieutenant Stewart Ross Graham, United States Coast Guard, and his crewman, Aviation Metalsmith 2nd Class (AM2) Robert McAuliffe, completed the longest unescorted helicopter flight on record. They flew a Sikorsky HO3S-1G, serial number 51-234, from the Coast Guard Air Station, Elizabeth City, North Carolina, to Coast Guard Air Station Port Angeles, Washington, via San Diego, California, covering a distance of 3,750 miles (6,035 kilometers) in 57.6 flight hours over 11 days.
Lieutenant Graham was the first Coast Guard pilot to fly a helicopter from a ship.¹ On 16 January 1944, he flew a Sikorsky HNS-1, Bu. No. 46445,² from the deck of a British freighter, SS Daghestan, while in convoy from New York to Liverpool. After 30 minutes, he returned to the freighter. He was a pioneer in the use of the helicopter by the Coast Guard and the Navy.
U.S. Coast Guard Sikorsky HO3S-1G 51-232, sister ship of 51-234. (U.S. Coast Guard)
The HO3S (Sikorsky S-51) was a second-generation helicopter, capable of carrying a pilot and up to three passengers. The cabin was built of aluminum with Plexiglas windows. The fuselage was built of plastic-impregnated plywood, and the tail boom was wood monocoque construction.
The main rotor consisted of three fully-articulated blades built of metal spars and plywood ribs and covered with two layers of fabric. (All metal blades soon became available.) The three bladed semi-articulated tail rotor was built of laminated wood. The main rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right.) The tail rotor was mounted on the helicopter’s left side in a pusher configuration. It turned clockwise as seen from the helicopter’s left.
The helicopter’s fuselage was 41 feet, 7.5 inches (12.687 meters). The main rotor had a diameter of 48 feet (14.630 meters) and tail rotor diameter was 8 feet, 5 inches (2.2.565 meters) giving the helicopter an overall length of 57 feet, 1 inch (17.399 meters). It was 13 feet, 1.5 inches (4.001 meters) high. The landing gear tread was 12 feet (3.7 meters).
The S-51 had an empty weight of 4,050 pounds (1,837.05 kilograms) and maximum takeoff weight of 5,500 pounds (2,494.76 kilograms). Fuel capacity was 100 gallons (378.5 liters).
The helicopter was powered by an air-cooled, supercharged, 986.749-cubic-inch-displacement (16.170 liter) Pratt & Whitney R-985 AN-5 (Wasp Jr. T1B4) direct-drive, nine-cylinder radial engine which was placed vertically in the fuselage behind the crew compartment. This engine had a compression ratio of 6:1 and was rated at 450 horsepower at 2,300 r.p.m., Standard Day at Sea Level. The R-985 AN-5 was 48.00 inches (1.219 meters) long, 46.25 inches (1.175 meters) in diameter and weighed 684 pounds (310.3 kilograms) with a magnesium crankcase.
The S-51 had a maximum speed (Vne) of 107 knots (123.1 miles per hour/198.2 kilometers per hour). Range was 275 miles (442.6 kilometers). The service ceiling was 14,800 feet (4,511 meters). The absolute hover ceiling was 3,000 feet (914.4 meters).
Sikorsky built 220 helicopter of the S-51 series.
U.S. Coast Guard HO3S-1G, serial number 51-238, sister ship of Lieutenant Graham’s record-setting helicopter. (USCG/Smithsonian Institution)
¹ On 6 and 7 May 1943, Colonel Hollingsworth Franklin (“Frank”) Gregory, U.S. Army Air Corps, made 23 landings and takeoffs from the tanker SS Bunker Hill in Long Island Sound, flying the Army’s Vought-Sikorsky XR-4, 41-18874. Please see TDiA at: https://www.thisdayinaviation.com/6-7-may-1943/
Jackie Cochran with her Seversky AP-7A, NX1384, prior to her speed record attempt. (San Diego Air and Space Museum Archive)
6 April 1940: Flying her Seversky AP-7A, NX1384, Jackie Cochran set a Fédération Aéronautique Internationale and National Aeronautic Association speed record over a 2,000 kilometer (1,242.742 miles) course from Mount Wilson, California (northeast of Los Angeles) to Mesa Giganta, New Mexico (west of Albuquerque) with an average speed of 533.845 kilometers per hour (331.716 miles per hour).¹
National Aeronautic Association Certificate of Record in the San Diego Air and Space Museum Archive. (Bryan R. Swopes)
The Seversky AP-7 was an improved civil version of the Seversky P-35 fighter, which was the first U.S. Army Air Corps single engine airplane to feature all-metal construction, an enclosed cockpit and retractable landing gear. It was designed by Major Alexander Nikolaievich Prokofiev de Seversky, a World War I Russian fighter ace.
Jackie Cochran paints her race number, 13, of the fuselage of her Seversky AP-7. (San Diego Air and Space Museum Archives)
Cochran’s AP-7A was a specially-built racer, modified from the original AP-7 with a new, thinner, wing and different landing gear arrangement. It was powered by a an air-cooled, supercharged, 1,829.39-cubic-inch-displacement (29.978 liter) Pratt & Whitney Twin Wasp S1B3-G (R-1830-11) two-row 14-cylinder radial engine rated at 850 horsepower at 2,450 r.p.m. at 5,000 feet (1,524 meters), and 1,000 horsepower at 2,600 r.p.m. for take off. The engine turned a three-bladed Hamilton-Standard controllable-pitch propeller through a 3:2 gear reduction. The R-1830-11 was 4 feet, 8.66 inches (1.439 meters) long with a diameter of 4 feet, 0.00 inches (1.219 meters), and weighed 1,320 pounds (599 kilograms).
This is the same airplane in which Jackie Cochran won the 1938 Bendix Trophy Race.
Jackie Cochran’s Seversky AP-7A, NX1384, at the Union Air Terminal, Burbank, California, 1940. (Bill Larkins/Wikipedia)
The Bell XP-39 prototype, 38-326, in the original turbosupercharged configuration. The intercooler and waste gates created significant aerodynamic drag. (U.S. Air Force)
6 April 1939: ¹ After being shipped by truck from the Bell Aircraft Company factory at Buffalo, New York, the XP-39 prototype, 38-326, (Bell Model 4) made its first flight at Wright Field, Dayton, Ohio, with test pilot James Taylor ² in the cockpit. During the test flight, Taylor flew the XP-39 to 390 miles per hour (628 kilometers per hour) at 20,000 feet (6,096 meters). The service ceiling was 32,000 feet (9,754 meters).
The XP-39 was designed by Bell’s chief engineer, Robert J. Woods, to meet a U.S. Army Air Corps requirement, X-609, issued in March 1937, for a high altitude interceptor. A contract for the prototype was issued 7 October 1937. On 15 April 1939, Assistant Secretary of War Louis Johnson announced that the U.S. Army had purchased the experimental Bell XP-39 and the Seversky XP-41. The War Department announced a $1,073,445 contract to purchase 12 YP-39s and one YP-39A on 27 April 1939.
The Bell XP-39 Airacobra was a single-place, single-engine prototype fighter with a low wing and retractable tricycle landing gear. The airplane was primarily built of aluminum, though control surfaces were fabric covered.
Bell XP-39 Airacobra 38-326. (U.S. Air Force)
As originally built, the XP-39 was 28 feet, 8 inches (8.738 meters) long with a wingspan of 35 feet, 10 inches (10.922 meters). The prototype had an empty weight of 3,995 pounds (1,812 kilograms) and gross weight of 5,550 pounds (2,517 kilograms).
The Bell XP-39 Aircobra in original configuration. (U. S. Air Force)
The XP-39 was unarmed, but it had been designed around the American Armament Corporation T9 37 mm autocannon, later designated Gun, Automatic, 37 mm, M4 (Aircraft).³ The cannon and ammunition were in the forward fuselage, above the engine driveshaft. The gun fired through the reduction gear box and propeller hub.
The XP-39 was originally powered by a liquid-cooled, turbosupercharged and supercharged 1,710.597-cubic-inch-displacement (28.032 liter) Allison Engineering Co. V-1710-E2 (V-1710-17), a single overhead cam (SOHC) 60° V-12 engine with a compression ratio of 6.65:1. The V-1710-17 had a Maximum Continuous Power rating of 1,000 horsepower at 2,600 r.p.m. at 25,000 feet (7,620 meters), and Takeoff/Military Power rating of 1,150 horsepower at 3,000 r.p.m. at 25,000 feet, burning 91 octane gasoline.
Bell P-39 Airacobra center fuselage detail with maintenance panels open. (U.S. Air Force photo)
The engine was installed in an unusual configuration behind the cockpit, with a two-piece drive shaft passing under the cockpit and turning the three-bladed Curtiss Electric constant-speed propeller through a remotely-mounted 1.8:1 gear reduction gear box. The V-1710-17 was 16 feet, 1.79 inches (4.922 meters) long, including the drive shaft and remote gear box. It was 2 feet, 11.45 inches (0.900 meters) high, 2 feet, 5.28 inches (0.744 meters) wide and weighed 1,350 pounds (612 kilograms).
Allison V-1710 E19 (V-1710-85) with extension drive shaft and remote propeller drive gear unit. (Allison Division of General Motors)
On 6 June 1939 the XP-39 was flown to the National Advisory Committee for Aeronautics (NACA) Langley Memorial Aeronautical Laboratory at Hampton, Virginia, by Lieutenant Mark E. Bradley, Jr. The prototype was tested in the Full-Scale Wind Tunnel. Improvements in aerodynamics were recommended and Bell rebuilt the airplane as the XP-39B with an Allison V-1710-E5 (V-1710-37) engine.
Bell XP-39 Airacobra 38-326 in the NACA Langley Memorial Aeronautical Laboratory Full-Scale Wind Tunnel, Langley Field, Virginia. (NASA)Bell XP-39 Airacobra 38-326 in the NACA Langley Memorial Aeronautical Laboratory Full-Scale Wind Tunnel, Langley Field, Hampton, Virginia, 9 August 1939. The fuselage has had all protrusions removed. (NASA)Bell XP-39 Airacobra 38-326 in the NACA Langley Memorial Aeronautical Laboratory Full-Scale Wind Tunnel, Langley Field, Hampton, Virginia. (NASA)
The turbosupercharger had been removed, which reduced the airplane’s power at altitudes above 15,000 feet (4,572 meters). The V-1710-37 had a maximum power of 1,090 horsepower at 3,000 r.p.m. at 13,300 feet (4,054 meters). This resulted in the P-39 being used primarily as a ground-attack weapon.
The XP-39B, with test pilot George Price in the cockpit, was damaged when when its landing gear did not fully extend, 6 January 1940. It was repaired and test flights resumed. On 6 August 1940, Captain Ernest K. Warburton stalled the prototype on landing. The impact resulted in significant structural damage, beyond economic repair. The airplane was later scrapped.
Bell XP-39B Airacobra prototype, 38-326, at the Bell Aircraft Corporation airfield, Buffalo, New York, 1940. (Bell Aircraft Corporation)
On 27 April 1939, the U.S. Army announced that a contract to Bell Aircraft had been issued in the amount of $1,073,445 for delivery of thirteen YP-39s. 9,584 Bell P-39 Airacobras were built during World War II. More than half were sent to the Soviet Union.
Bell XP-39B prototype, serial number 38-326. (Bell Aircraft Corporation)
¹ Reliable sources indicate the date of the first flight as both 6 April 1938 and 6 April 1939. The Bell Helicopter Company web site, “The History of Bell Helicopter: 1935–1949” states 1938. However, contemporary newspaper articles strongly suggest that the date was 1939. The first newspaper references to the XP-39 located by TDiA are dated 16 April 1939. On 18 April 1939, the Dayton Daily News reported:
The radically-designed XP-39 is at the field now undergoing further testing. Its purchase was announced Saturday in Washington. It had been at the materiel division for about two months before its initial flight on Army Day, April 6.
² James Taylor may have been James Blackstone (“Jimmie”) Taylor, Jr. (23 September 1897–25 May 1942). Taylor (Lieutenant Commander, United States Naval Reserve) was a well-known test pilot of the time. He was famous for his high-speed power dive from 20,000 feet (6,096 meters) over Farmingdale, New York, in the Seversky NF-1, 25 June 1937.
³ The 37-mm Aircraft Gun Matériel M4 is a recoil-operated aircraft weapon designed by John M. Browning. It has an overall length of 7 feet, 5 inches (2.26 meters). The barrel, or “tube,” is 5 feet, 5 inches (1.65 meters) long with a caliber of 1.457 inches (37.0 millimeters) and weighs 55 pounds (25 kilograms). The barrel is part of the recoiling section of the gun and moves rearward 9-5/8 inches (245 millimeters). The weight of the gun with a loaded 30-round magazine is 306.4 pounds (138.98 kilograms). The M4 fires a high-explosive tracer round with a muzzle velocity of 2,000 feet per second (607 meters per second). Each M54 shell is 9.75 inches (248 millimeters) long and weighs 1.93 pounds, of which the projectile makes up 1.34 pounds (0.608 kilograms). The cannon has a cyclic rate of fire of 125–150 rounds per minute.
William MacCracken’s Pilot Identification CardUnited States of America Pilot License No. 1
6 April 1927: William Patterson MacCracken, Jr., Assistant Secretary of Commerce for Aeronautics, became the first person to be issued a pilot’s license by the government of the United States. License Number 1 was a private license, signed by then Secretary of Commerce Herbert Hoover, who would later become the 31st President of the United States of America.
Assistant Secretary MacCracken had offered the first pilot certificate to aviation pioneer Orville Wright, but Wright declined, as “he no longer flew and did not think he needed a Federal license to show that he had been the first man to fly.”
