F1D

F1D is a class within the Fédération Aéronautique Internationale (FAI) competition system for free-flight model aircraft. It is part of the F1 family of international classes and is primarily associated with indoor, micro-power models designed to fly in confined spaces.

Historically, F1D models are small and lightweight and are typically powered by a wound rubber motor, though some variations have used other compact propulsion. They are optimized for stable, level flight in gymnasiums or similar indoor venues, where flight duration and precision are key performance criteria.

Rules governing F1D specify maximum dimensions, minimum weight, and propulsion limits, along with endurance targets. Pilots wind the rubber motor to a prescribed number of turns, then launch the model by hand; after release the model must maintain a stable climb and graceful glide until the flight ends at a specified time or when the energy is exhausted. Flights are timed and judged for duration, adherence to the intended flight profile, and safety.

FAI sanctions F1D competitions at international events such as the World Indoor Championships, and national federations also organize regional and national meets that feed into the world circuit.

F1D is one of several free-flight classes under the FAI umbrella, reflecting the sport’s focus on lightweight construction, simple propulsion, and precise, low-speed flight in restricted spaces.