This Week In AFLCMC History - September 18 - 24, 2023

  • Published
  • By Air Force Life Cycle Management Center History Office
19 Sep 1967 (Digital Directorate)

Today in 1967, the Electronic Systems Division at Hanscom took on development of a new weather radar designated “AN/FPS-77.” During the 1960s-80s, Air Traffic Control radars could not accurately measure storms from very far out, as they were on a fixed elevation level (typically of 5 degrees) with a broad band of coverage. While this made them very effective for detecting and separating air traffic, these radars could completely miss small storms beyond 60 nautical miles and would detect less and less of larger storms the further away they were. As such, controllers could sometimes unintentionally vector pilots into or through storms that were off their radar. By contrast, the FPS-77 was a C-band radar with a 1.6 degree “pencil” beam (see top beam in picture) which could be adjusted up and down to detect storms more easily by measuring height, depth, and location data at upwards of 200 nautical miles.

20 Sep 2005 (Armament Directorate)

Today in 2005, the GBU-39/B Small Diameter Bomb (SDB)’s was approved to enter Operational Test and Evaluation a month ahead of schedule, and under cost, by Eglin AFB’s Air Armament Center. The SDB is a 250-pound all-weather, low yield air-to-surface bomb guided by GPS. Its small size and low weight allow it to be carried on a wide variety of aircraft, though it was first employed by the F-15E Strike Eagle—where it has seen combat use since Oct 2006. Carried in smart carriages that can hold up to four SDBs at a time, these bombs can be released against either single targets or multiple individual targets. The Air Force describes the SDB as a weapon that “increases aircraft loadout, decreases the logistical footprint, decreases collateral damage, and improves aircraft sortie generation times.”

21 Sep 1938 (Air Force History)

Today, 85 years ago, Maj Gen Oscar Westover, the Chief of the Army Air Corps, lost his life when the aircraft he was piloting crashed short of the Lockheed plant’s runway in Glendale, California. Sergeant Samuel Hynes, Westover’s personal mechanic, aged 39, also perished in the accident. No one on the ground was killed, but the wreckage did cause two houses to catch fire. Following Gen Westover’s death, Gen Henry H. “Hap” Arnold (Westover’s deputy) assumed temporary command of the army’s air forces pending a permanent appointment by President Roosevelt. Eventually Arnold would receive that appointment, though for a time it was unclear if it
would be him or Gen Frank M. Andrews. Today, Westover Air Reserve Base in Massachusetts—the largest Air Reserve Base in the nation—is named in memory of Gen Westover.

22 Sep 1949 (Mobility & Training Aircraft Dir.)

Convair's T-29 “Flying Classroom” made its first flight. This aircraft, a converted airliner with the seats ripped out to make room for fourteen navigation stations, was meant for Undergraduate Navigator Training. At each navigation station, students had access to maps, a loran scope, a radio compass, and an altimeter. There were also four astrodomes above the deck where sextant sightings could be taken. In Sep 1951, the Air Force began experimenting with the idea that specialized training should occur for specific aircraft, and soon additional training was added to the syllabus (at one point in 1954 there were 53 versions of differing syllabi). Initial training continued to be conducted in the T-29 (as well as some other airframes) until 1974, when the “Flying Classroom” was replaced by the T-43, which was itself a modified Boeing 737.

23 Sep 1949 (Intelligence, Surveillance, Reconnaissance & Special Ops Forces Dir.)

On this day in 1949, every newspaper in the country ran the same front-page story after President Truman made a stunning announcement: The Soviet Union had detonated an atomic bomb. But it wasn’t just the American people who were surprised—Soviet leadership was probably just as shocked by the announcement, as they were likely unaware that the Americans had the ability to detect their nuclear testing through tell-tale traces of radiation and other elements in the air. Soviet testing was conducted on 29 Aug 1949, with a device the Soviets called “First Lightning” (and the Americans dubbed “Joe-1”). The U.S. first became aware of the test on 3 Sep, when an Air Weather Service RB-29 picked up traces of it while flying off the coast of Siberia. This marked the beginning of the Cold War’s “nuclear arms race.”

24 Sep 1991 (Tinker AFB/Propulsion Dir.)

Today in 1991, Tinker AFB held a “retirement ceremony” for the Allison TF41 engine, for which that depot had performed maintenance over the past 21 years. This engine was derived from the British Rolls-Royce Spey through their partnership with the American Allison Engine company. It was a subsonic, non-afterburning low-bypass turbofan that produced over 14,000 pounds of thrust. The Air Force used it solely for the LTV A-7D Corsair II ground attack aircraft, which itself was an adaptation of the Navy’s A-7. The TF41 pro-vided more thrust than the Corsair’s original engine, leading the Navy to incorporate it into their later variants. Four years after this retirement event, Rolls-Royce purchased Allison.

75 Years Ago in AFLCMC History: First Flight of the XF-92A (18 Sep 1948)

Seventy-five years ago today, the XF-92A flew for the first time at Muroc (now Edwards) AFB, piloted by Convair test pilot Ellis D. “Sam” Shannon. This experimental airplane was the first jet to fly with a delta-wing configuration— a triangular wing shape named for its resemblance to the Greek letter delta. This shape was pioneered by German aeronautical engineer Alexander Lippisch, who also designed the first operational rocket plane, the Me-163, in World War II Lippisch was one of the many German scientists brought to the U.S. after the war under Project Paperclip, and he was among the more than 200 to be sent to Wright Field. He brought his expertise on radical wing shapes and tailless aircraft, spurring the consideration of the delta wing by the Air Force.

Convair’s original proposed F-92 had a complex ramjet and rocket propulsion system, with swept wings, but was cancelled after the end of WWII. The company revised the design as an interceptor, with turbojets and a delta wing, which it vetted with Lippisch. The USAF and the National Advisory Committee for Aeronautics (or NACA—NASA’s predecessor) conducted wind tunnel tests of the wing shape between 1948 and 1953, verifying that the delta wing was more efficient than conventional or swept wings for supersonic applications. The YF-92A had several design issues, but provided risk-reduction for the F-102 Delta Dagger, the world’s first supersonic jet interceptor that became operational in 1956.

However, the YF-102 prototype demonstrated higher-than-expected drag during transonic flight. NACA research discovered the “area rule” that characterized the need for a smooth increase in cross-sectional area for an aircraft body and wing, which was “violated” by the delta wing. This led to the retrofit of a pinched “wasp waist” fuselage for the F-102 and subsequent F-106 Delta Dart. Only one XF-92A was ever built, which is on display at the National Museum of the U.S. Air Force.