Brief History of the USAF Cessna O-2A “Fighting Skymaster”
In April 1967, Cessna delivered the first of 501 Model 337 Skymasters, designated the O-2A, to the U.S. Air Force (USAF) for use as forward air control (FAC) aircraft in the ongoing unpleasantness in Southeast Asia. Modifications to the basic civilian configuration included two underwing weapons hardpoints on each wing, a rear-engine smoke-generation system, an armament control system, a non-computing optical gunsight, and a large radio rack in the aft baggage compartment to accommodate an impressive array of communications, navigation, and secure identification equipment.
The O-2 quickly gained a reputation as a highly capable FAC platform and saw combat action throughout the theater of operations until the final days of the Vietnam War. After the war, the O-2A continued to serve in active-duty, Air National Guard, and USAF Reserve units until December 1987 when USAF retired its last O-2As, three of the five that had served the Air Force Flight Test Center at Edwards AFB, California, as low-speed chase aircraft.
Enter the Sandcrab
In early 1982, Brico Ltd. of Arlington, Virginia, joined with Robertson Aircraft Corporation of Everett, Washington, to develop a prototype O‑2ST (single turboprop), which was first flown six months later. Brico had a contract with the Saudi Arabian government with some contract assistance (and possible official interest) from the USAF. The Saudis wanted a multipurpose aircraft able to operate off loose sands in desert environments, which led to it being dubbed the Sandcrab. They also wanted short takeoff and landing capabilities (with a takeoff roll of 945 feet and a landing roll of 470 feet), a 185 KTAS cruise, a 1,520‑mile range, and up to 2,250 pounds of useful load.
This O-2ST used a single, rear‑mounted, 700‑horsepower Allison 250‑C30 turboprop (later replaced by a Pratt & Whitney 700‑horsepower PT6A) turning a 102‑inch pusher propeller. The design incorporated a Robertson high‑lift system – including increased wing leading edge camber, wing upper surface stall fences, and drooped ailerons – and a third vertical stabilizer mounted at the midpoint of the standard horizontal stabilizer to improve low-speed control. The stretched fuselage allowed six‑place seating. Brico also designed an optional composite annular propeller shroud with a narrow chord that increased thrust by 25 percent but added minimal drag at cruise airspeeds.
For flight tests, the tricycle landing gear was fixed, although production plans included retractable gear. After the US flight tests were completed, the prototype aircraft was shipped to Saudi Arabia for further tests and demonstrations. Eventually, they dismantled the Sandcrab, shipped it back to the US, and turned it over to a university. No follow-up production contract ensued.