The Aerotechnik WGM.21 is a quadrotor helicopter that was developed in the 1970s.

Four rotors are mounted at the end of a four tubular supports arranged into a X shape.

Pitch is controlled by foot pedals.

A second model, the WGM.22, was developed with side-by-side configuration seating and an enclosed cockpit.

[1] Data from Air ProgressGeneral characteristics Performance