Raytheon Beech RC-21E/H
For many years the US Army purchased a number of versions of the Beech King Air / Super King Air /Queen Air series of utility twin-engined aircraft for use in special mission work.
The first was the RC-21A (King Air 100), which had the ARQ-38 ‘Left Jab’ radio direction finding (RDF) system installed. The RC-21 E/H is a military version of Beech Queen Air 80 and was designated as Special Electronic Mission Aircraft (SEMA). These aircraft were operated by 320th ASA (Army Security Agency) Company on behalf on NSA at Ramstein from 1978 and were also operated in South Korea and USA. The aircraft were equipped with Guardrail COMINT/D/F equipment manufactured by Electromagnetic Systems Laboratories of California. The crew consisted of 2 pilots and two system operators at a ground station.
In 1974 the RU-21J began being delivered to the US Army under the Cefly Lancer programme. These aircraft were equipped with the ALQ-150 tactical ESM equipment and were targeted against Warsaw Pact multichannel microwave systems which carried high level trunk communications. They also carried the ALQ-151 (Quick Fix) DF intercept and ECM system and the ALQ-156 Missile Detector System which could evaluate threats and automatically deploy decoys from a M-130 flare dispenser.