Left Foot

Left Foot was an airborne radio direction finding system used by the US Army. The system was mounted on modified U-21 Ute utility aircraft, designated RU-21E.

The Left Foot system was developed in 1972 as an improvement to Laffing Eagle system fitted to the RU-21D. The Left Foot system incorporated a plotting computer that removed all plotting responsibility from the cockpit by providing automatic position fixing. Some 16 aircraft were converted to the Left Foot configuration, but they were never deployed outside of the continental United States.

The Left Foot system was removed from service so that the RU-21E aircraft could be repurposed for the Guardrail II/IIA and IV programs.