Page 30 - Volume 15 Number 6

certification, production com- menced for the 1966 model year. Priced at about $400,000, the Model A90 offered a lot of performance and utility and 206 airplanes were built before the A90 was superseded on the production line by the Model B90 King Air.
The B90 took to the air for the first time April 13, 1967. It possessed only minor upgrades to airframe systems but retained the A90’s PT6A-20 engines and reversing propellers. The B90 entered production in 1968, and 184 airplanes were manufactured before the Model C90 appeared for the 1971 model year.
In addition to being popular with commercial operators, the Model A90/B90 was soon pressed into service with the U.S. Army. Designated U-21A (Beechcraft designation was A90-1), the Army
bought 110 airplanes from 1966- 1968 and the majority were assigned to units serving in Southeast Asia during the Vietnam War, chiefly performing liaison, transport, surveillance and utility missions which they accomplished in admirable fashion.
Unlike the commercial A90 and B90, however, the Army’s airplanes were unpressurized and featured square windows reminiscent of the Model 65 Queen Air series. To facilitate handling of large cargo, such as spare engines, propellers and other war material, the U-21A fleet was equipped with a cargo door on the left side of the fuselage that incorporated an airstair door.
A small number of airplanes were built by the factory specifically to meet Army specifications for special missions such as intelligence gathering and battlefield
communications. Officially dubbed “Guardrail” by the Army, four of these unique aircraft were designated RU-21A and another 10 served under the designation RU- 21D with special antenna arrays installed vertically on the wings and empennage surfaces.
To conduct special missions operations of a more clandestine nature, the Army ordered and equipped 17 U-21Gs. All were built and delivered in 1971. These airplanes were designed specifically to accommodate sophisticated electronic countermeasures and communications equipment in the cabin and in pods at each wingtip.
The aircraft were not the first built as the Army’s new special missions’ platform. In 1967, the factory built three RU-21B (A90-2) and two RU-21C (A90-3) aircraft. In 1971, Beech Aircraft built and delivered 16 “Guardrail” platforms designated RU-21E and RU-21H (A90-4) that served the Army in the role of electronic surveillance and other related missions. These airplanes were powered by Pratt & Whitney PT6A-28 engines each rated at 620 shp to accommodate a higher maximum gross weight of 10,900 pounds. KA
Ed Phillips, now retired and living in the South, has researched and written eight books on the unique and rich aviation history that belongs to Wichita, Kan. His writings have focused on the evolution of the airplanes, companies and people that have made Wichita the “Air Capital of the World” for more than 80 years.
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28 • KING AIR MAGAZINE
MAY 2021