Tag Archives: M24 20mm Automatic Aircraft Cannon

5 February 1958

Boeing B-47E-55-BE Stratojet 51-2394, similar in appearance to Ivory Two. Photographed 7 April 1956. (U.S. Air Force)

On the night of 4–5 February 1958, two Boeing B-47 Stratojet bombers from MacDill Air Force Base, Florida, were flying a simulated bombing mission. The second bomber, B-47B-50-BW serial number 51-2349, was under the commander of Major Howard Richardson, USAF, with co-pilot 1st Lieutenant Bob Lagerstrom and radar navigator Captain Leland Woolard. Their call sign was “Ivory Two.”

Aircrew of B-47, left to right, Major Howard Richardson, Bob Lagerstrom and Leland Woolard. (U.S. Air Force)

Carried in the bomb bay of Ivory Two was a 7,600-pound (3,448 kilogram) Mark 15 Mod. 0 two-stage radiation-implosion thermonuclear bomb, serial number 47782. The bomb had an explosive yield of 1.69–3.8 megatons.

Bomb, Thermonuclear, Mark 15.
Bomb, Thermonuclear, Mark 15. (Nuclear Weapons Archive)

After completing their simulated bombing mission, the B-47s were returning to their base in Florida.

On the same night pilots of South Carolina Air National Guard were on alert at Charleston Air Force Base with their North American Aviation F-86L Sabre interceptors. The fighters were fully armed with twenty-four 2.75-inch (70 mm) rockets. At 00:09 a.m., the pilots were alerted for a training interception of the southbound B-47s. Within five minutes three F-86Ls were airborne and climbing, with air defense radar sites directing them. In of of the F-86Ls, 52-10108, an upgraded F-86D Sabre, was 1st Lieutenant Clarence A. Stewart, call sign “Pug Gold Two.”

The flight of interceptors came in behind the bombers at about 35,000 feet (10,668 meters). Tracking their targets with radar, they closed on the lead B-47, Ivory One, from behind. Ivory Two was about 1 mile (1.6 kilometers) in trail of Ivory One, but the airborne radars of the Sabres did not detect it, nor did the ground-based radar controllers.

This North American Aviation F-86L-60-NA Sabre, 53-1047, of the 444th Fighter Interceptor Squadron, Charleston, South Carolina, is similar to 1st Lieutenant Clarence A. Stewart's F-86L-50-NA 52-10108, destroyed in the collision with the B-47, 5 February 1958. (U.S. Air Force)
This North American Aviation F-86L-60-NA Sabre, 53-1047, of the 444th Fighter Interceptor Squadron, Charleston Air Force Base, South Carolina, is similar to 1st Lieutenant Clarence A. Stewart’s F-86L-50-NA 52-10108, which was destroyed in the collision with the B-47, 5 February 1958. (U.S. Air Force)

At 00:33:30, 5 February, Lieutenant Stewart’s fighter collided with the left wing of Major Richardson’s bomber. The Sabre lost both wings. Lieutenant Stewart fired his ejection seat. His descent from the stratosphere took twenty-two minutes and his hands were frostbitten from the cold. He spent five weeks in an Air Force hospital. Pug Gold Two crashed in a farm field about 10 miles (16 kilometers) east of Sylvania, Georgia.

Damage to the left wing and aft fuselage of B-47B 51-2349. (U.S. Air Force)

The B-47 was heavily damaged. The outboard engine had been dislodged from its mount on the wing and hung at about a 45° angle. The wing’s main spar was broken, the aileron was damaged, and the airplane and its crew were in immediate jeopardy. If the number six engine fell free, the loss of it’s weight would upset the airplane’s delicate balance and cause it to go out of control. The damaged wing might itself fail, and the damage to the flight controls made it difficult to fly.

Damage to the left wing of B-47B 51-2349. (U.S. Air Force)

Major Richardson didn’t think they could make it back to MacDill, and the nearest suitable airfield, Hunter Air Force Base, Savannah, Georgia, advised that the main runway was under repair. A crash on landing was a likely outcome.

Damage to the aft fuselage and vertical fin of B-47B 51-2349. (U.S. Air Force)

With this in mind, Richardson flew Ivory Two out over Wassaw Sound, and at an altitude of 7,200 feet (2,195 meters) the hydrogen bomb was jettisoned. It landed in about 40 feet (12 meters) of water near Tybee Island. No explosion occurred.

The B-47 safely landed at Hunter AFB, but was so badly damaged that it never flew again. Major Richardson was awarded the Distinguished Flying Cross for his handling of the incident.

The missing Mark 15 has never been found and is considered to be “irretrievably lost.” It is known as “The Tybee Bomb.”

Boeing B-47B-50-BW 51-2348, sister ship of Ivory Two. (U.S. Air Force)

Designed by Boeing, the Stratojet was a high-subsonic-speed strategic bomber and reconnaissance aircraft, in service from 1951 until 1977. The B-47 could fly higher and faster than jet fighters of the time, and it was also highly maneuverable. The B-47 was flown by a two pilots in a tandem cockpit. A navigator/bombardier was at a station in the nose.

The Boeing B-47B Stratojet was the first full-production model. The B-47B is 106 feet, 10 inches (32.563 meters) long with a wingspan of 116 feet , 0 inches(35.357 meters), and an overall height of 27 feet, 11 inches (8.509 meters). The wings are shoulder-mounted with the leading edges swept at 35°. The B-47B has an empty weight of 78,102 pounds (35,426 kilograms), and a gross weight of 184,908 pounds (83,873 kilograms). The maximum takeoff weight was 200,000 pounds (90,718 kilograms).

From 1953 to 1957, the B-47B fleet underwent an extensive modification program which brought them up to the B-47E configuration.

A Boeing B-47B-40-BW Stratojet 51-2212 of the 306th Bombardment Wing (Medium) rolling out after landing at MacDill AFB, Florida. This airplane is similar to B-47B 51-2349, Ivory Two. (U.S. Air Force)

The B-47B was originally powered by six General Electric J47-GE-11 turbojet engines in four nacelles mounted on pylons below the wings. All B-47Bs after serial number 51-2046 were equipped with J47-GE-23 engines. The airplanes built with the -11 engines were retroffitted with the -23s. Under the modification and upgrade program, the -23s were replaced by the J47-GE-25. This engine has a 12-stage axial-flow compressor, eight combustion chambers, and single-stage turbine. The J47-GE-25 is rated at 5,970 pounds of static thrust at Sea Level, at 7,950 r.p.m. and 1,250 °F. (677 °C.) turbine outlet temperature (TOT). (7,200 pounds of thrust with water injection). It has a maximum diameter of 3 feet, 1 inch (0.940 meters) and length of 12 feet, 0 inches (3.658 meters) and weighs 2,653 pounds (1,203 kilograms).

The B-47B Stratojet had a cruise speed of 498 miles per hour (801 kilometers per hour), and maximum speed of 608 miles per hour (978 kilometers per hour) at 16,300 feet (4,968 meters) and 565 miles per hour (909 kilometers per hour) at 35,000 feet (10,668 meters). The service ceiling was 33,900 feet (10,333 meters) and combat ceiling 40,800 feet (12,436 meters).

The combat radius of the B-47B was 1,965 miles (3,162 kilometers with a 10,000 pound (4,536 kilograms) bomb load. Two jettisonable underwing fuel tanks could carry 1,780 gallons (6,738 liters) each. The maximum ferry range was 4,444 miles (7,152 kilometers).

For defense the B-47B was armed with two Browning AN-M3 .50-caliber machine guns in a remotely-operated tail turret. The co-pilot acted as the gunner using an optical sight. The machine guns were replaced by two M24A1 20 mm autocannons and radar control.

The maximum bomb load of the B-47B was 18,000 pounds (8,165 kilograms). The B-47 could carry two 7,600 pound (3,447 kilogram) Mark 15 two-stage radiation implosion thermonuclear bombs, each with an explosive yield of 3.8 megatons, or a single 10,670 pound (4,808 kilogram) B-41 three-stage, 25 megaton bomb.

Beginning in 1953, the B-47B fleet underwent an extensive modification program which brought them up to the B-47E configuration.

A total of 2,032 B-47s were built by a consortium of aircraft manufacturers: Boeing Airplane Company, Wichita, Kansas; Douglas Aircraft Company, Tulsa, Oklahoma; Lockheed Aircraft Company, Marietta, Georgia. 399 of these were B-47Bs.

The Stratojet is one of the most influential aircraft designs of all time and its legacy can be seen in almost every jet airliner built since the 1950s: the swept wing with engines suspended below and ahead on pylons. The B-47 served the United States Air Force from 1951 to 1977. From the first flight of the Boeing XB-47 Stratojet prototype, 17 December 1947, to the final flight of B-47E 52-166, was 38 years, 6 months, 1 day.

© 2018, Bryan R. Swopes

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30 August 1952

The left wing attachment points of this Northrop F-89C-30-NO Scorpion, 51-5781, failded during a fly-by at the Inaternational Aviation Exposition, Detroit, Michigan, 30 August 1952. (U.S. Air Force)
The left wing of this Northrop F-89C-30-NO Scorpion, 51-5781, failed during a fly-by at the International Aviation Exposition, Detroit, Michigan, 30 August 1952. (Wikipedia)

30 August 1952: At 4:40 p.m., a tragic accident occurred during a fly-by of two new United States Air Force Northrop F-89C Scorpion all weather interceptors at the International Aviation Exposition at Detroit, Michigan.

Two F-89Cs of the 27th Fighter Interceptor Squadron, 4711th Defense Wing, based at Griffis Air Force Base, Rome, New York, made a low-altitude, high speed pass in full view of 51,000 spectators, including General Hoyt S. Vandenberg, then serving his second term as Chief of Staff, United States Air Force. Suddenly, the left wing of the lead interceptor separated. The tail also broke away and the fighter crashed and exploded. In the resulting fire, the Scorpion’s 20 millimeter cannon shells exploded.

Photograph by B.J. Mullof from The Detroit Free Press, Sunday, 31 August 1952, Vol.122, No. 118, Page 1, Columns 1–3.

Major Donald E. Adams, a fighter ace who had won the Silver Star in Korea just months earlier, was killed, along with Captain Edward F. Kelly, Jr., the radar intercept officer. Five people on the ground were injured by falling wreckage.

The second F-89 was flown by Major John Recher and Captain Thomas Myslicki. They landed immediately at Selfridge Air Force Base.

This was not the first wing failure in an F-89C, nor the last. The Air Force grounded the Scorpions and ordered Northrop to return the airplanes to the factory or to modification centers using the company’s pilots. Northrop engineers began an intensive investigation to discover the cause of these catastrophic failures.

When designing the airplane engineers tried to use materials that provided the greatest strength at the lightest weight. A new aluminum alloy had been used for the wing attachment fittings. This material had properties that weren’t understood at the time, but when subjected to certain types of dynamic loads, it could fatigue and become brittle rapidly. It was also very sensitive to surface imperfections, such as scratches or machining marks, that could rapidly propagate fatigue fractures.

Northrop F-89C-30-NO Scorpion 51-5785, sister ship of Major Adams’ interceptor.

A second problem was that, under certain conditions, the Scorpion’s wings could enter a sequence of rapidly increasing oscillations, actually twisting the wing. This occurred so quickly that a pilot was not likely to see it happening. The twisting motion focused on the wing attachment points, and resulted in a catastrophic failure.

Northrop redesigned the wing to reduce the oscillation, and replaced the aluminum attachment fittings with new ones made of forged steel.

The F-89 was returned to service and became a very reliable airplane.

Pilot and radar intercept officer of a Northrop F-89C Scorpion. (Jet Pilot Overseas)

Major Adams’ Scorpion, Northrop F-89C-30-NO 51-5781, was a two-place, twin-engine, all weather interceptor, designed as a replacement for the World War II-era Northrop P-61 Black Widow night fighter. It was 53 feet, 5 inches (16.281 meters) long with a wingspan of 56 feet (17.069 meters) and overall height of 17 feet, 6 inches (5.334 meters). Its empty weight was 24,570 pounds (11,145 kilograms) and maximum gross weight was 37,348 pounds (16,941 kilograms).

The F-89C was powered by two Allison J35-A-33 afterburning turbojet engines. The J35 was a single-spool, axial-flow turbojet with an 11-stage compressor section, 8 combustion chambers and single-stage turbine. The J35-A-33 was rated at 5,400 pounds of thrust (24.02 kilonewtons) and 7,400 pounds (32.92 kilonewtons) with afterburner.

It had a maximum speed of 650 miles per hour (1,046 kilometers per hour) at Sea Level and 562 miles per hour (905 kilometers per hour) at 40,000 feet (12,192 meters). The service ceiling was 50,500 feet (15,392 meters) and maximum range was 905 miles (1,457 kilometers).

An Air Force master sergeant loading 20mm cannon shells for an F-89’s six 20 mm guns. (LIFE Magazine)

The interceptor was armed with six 20 mm M24 cannon in the nose, and could carry sixteen 5-inch rockets or 3,200 pounds (1,451.5 kilograms) of bombs on hardpoints under its wings.

Northrop Corporation built 1,050 F-89 Scorpions. 164 were F-89Cs. Variants produced after this deleted the six cannon in the nose and used aerial rockets instead. Scorpions served the Air Force and Air National Guard in the air defense role until 1969.

Major Donald E. Adams, United States Air Force. (Imperial War Museum)

Donald Earl Adams was born 23 February 1921 at Canton, New York. He was the first of two sons of Alonzo Deys Adams, a wallpaper and paint salesman, and Mae C. Hurd Adams.

Adams attended Western State Teachers College, Kalamazoo, Michigan. He was a member of the baseball, boxing and wrestling teams.

After graduating from college, Adams enlisted as a private, Enlisted Reserve Corps, at Rochester, New York, 10 October 1942. He was 6 feet, 0 inches (1.83 meters) tall and weighed 155 pounds (70 kilograms). Private Adams was appointed an Aviation Cadet, 18 November 1942.

Miss Mary Ann Lewark, 1942

On 13 February 1943, at Montgomery, Alabama, Adams married Miss Mary Ann Lewark, the 21-year-old daughter of Mr. and Mrs. Glenn W. Lewark, and a graduate of Western Michigan College at Kalamazoo. They would have three children, Donald, Nancy and Steven.

On completion of flight training, Cadet Adams was commissioned as a Second Lieutenant, Army of the United States (A.U.S.), 30 August 1943.

Lieutenant Adams was assigned as a flight instructor until July 1944, when he underwent operational training as a P-51 Mustang fighter pilot.

Second Lieutenant Adams joined the 343rd Fighter Squadron, 55th Fighter Group, at RAF Wormingford (Air Force Station 131), Hertfordshire, in February 1945. He was assigned a North American Aviation P-51D-15-NA Mustang, 44-15372, with squadron markings CY R. He named his fighter Sweet Mary, after his wife. Adams is credited with destroying a Messerschmitt Bf 109 and Me 410 and damaging a second Bf 109, in strafing attacks on the afternoon of 9 April 1945, and a second Bf 109 damaged, 17 April 1945. He was promoted to First Lieutenant, A.U.S., 2 May 1945.

1st Lieutenant Donald Earl Adams, 343rd Fighter Squadron, 55th Fighter Group, 1945. (Imperial War Museum)

On 24 August 1946, Lieutenant Adams was appointed a second lieutenant, Field Artillery, with date of rank to 30 August 1943, his original commissioning date. In November 1946, Lieutenant Adams was assigned to the 307th Fighter Squadron, 31st Fighter Group, on occupation duty at Kitzigen Army Airfield in Bavaria. The 307th was one of the first units to be equipped with the Lockheed P-80A Shooting Star jet fighter. On 1 May 1947, Lieutenant Adams was transferred to the Air Corps.

Returning to the United States in June 1947, Lieutenant Adams was assigned to the 62nd Fighter Squadron, 56th Fighter Group, at Selfridge Air Force Base, near Mount Clemens, Michigan. The squadron flew P-80s and F-86 Sabres.

In October 1951, Major Adams joined the 16th Fighter-Interceptor Squadron, 51st Fighter-Interceptor Group, at Suwon Air Base (K-13), Republic of South Korea, flying the North American Aviation F-86 Sabre.

Silver Star

On 3 May 1952, Adams was leading a flight of six Sabres. He and his flight attacked a group of twenty Chinese MiG 15s. During the battle, he shot down the enemy flight leader and then the deputy flight leader and damaged three more enemy fighters, completely breaking up the enemy flight. He was awarded the Silver Star.

While flying the the 16th, Major Adams was credited with destroying 6½ enemy aircraft in aerial combat, and damaging another 3½. On his twentieth mission, he had just shot down a MiG 15 when he was attacked by four more. The enemy fighters chased Adams out over the Yellow Sea before he could break away. By this time, he was 250 miles (402 kilometers) from base with fuel remaining for just 100 miles (161 kilometers). He said, “I climbed to 45,000 feet [13,716 meters], shut of the engine and glided 150 miles [241 kilometers] before starting up again.”

Adams flew 100 combat missions during the Korean War. He returned to the United States 16 June 1952, and in July, was assigned to the 27th Fighter-Interceptor Squadron, 4711th Defense Wing, Air Defense Command, at Griffis Air Force Base.

In addition to the Silver Star, Major Adams had been awarded the Distinguished Flying Cross, the Air Medal with one silver and two bronze oak leaf clusters (seven awards), the Presidential Unit Citation with one oak leaf cluster (two awards), the American Campaign Medal, European African-Middle Eastern Campaign Medal with three service stars, World War II Victory Medal, Army of Occupation Medal, National Defense Service Medal, Korean Service Medal with three service stars (three campaigns), the Air Force Longevity Service Award with one oak leaf cluster (ten years service), the Republic of Korea Presidential Unit Citation, the United Nations Service Medal for Korea, and the Republic of Korea War Service Medal.

Major Donald Earl Adams, United States Air Force, is buried at the Clinton Grove Cemetery, Mount Clemens, Michigan.

© 2017, Bryan R. Swopes

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