The GROB G109B is a two-seat motor glider with T-type stabilizer, fixed landing gear and airbrakes. It is classified as a TMG (Touring Motor Glider). It was designed by Burkhart Grob GmbH and features side by side seating as well as a classical tail-dragger undercarriage with a steerable tail wheel. The fuselage and wings are made of industrial carbon-fibre and glass-fibre composites.

A total of 154 of the G109 and  322 of the G109B aircraft were built from 1983 through to 1990. The Royal Air Force ordered the last 54 of the G109B (Vigilant MK 1) for the training of its cadets.

The G109B's engine was made by Grob (GR 2500) and is an aircooled 4-stroke flat engine.

The G109B is famous for its aerodynamic performances and ergonomically designed cockpit. It is easy to handle, good natured and has a respectable manoeuvrability. It banks very gently without spinning. G109B pilots and passengers enjoy flying in comfort with glider like visibility and side by side seating.

 In 1983 a Grob G109B motorglider extended the gliding world altitude record to 6,406m (21,018ft) and the gliding world altitude gain record to 5,042m (16,544ft).