Free flight (model aircraft)
Model aircraft that fly without any external control after launch.
Free flight is a branch of model aviation where the aircraft receives no active external control once launched. It represents the earliest form of hobby aeromodeling, and in competition, the goal is to build and launch a self-controlling model that repeatedly achieves the longest possible flight time across several rounds, while adhering to class-specific limits.
The core idea is that these aircraft do not require external commands, such as those from a radio. Such models have been flown for more than two centuries. They are built to be inherently stable: if a gust of wind or a thermal current disturbs them, they automatically return to stable flight. This stability comes from a combination of design and trim—specifically, the relationship among the center of gravity, wing and tailplane incidence, and rudder setting.
Because they have much lower wing loading than the engine-powered radio-controlled models many people first picture when they hear “model aircraft,” free-flight planes fly far more slowly. Most glide at little more than walking speed, and few weigh over 500 grams.
In competition, flight duration is almost always the sole objective. A major part of the sport’s appeal and challenge lies in designing the most efficient aircraft possible within constraints like minimum weight, maximum wing area, and type of motive power.
Free flight models generally fall into four categories: gliders (launched by towline or by hand), rubber-powered models (for pure duration or scale with duration), power models (using CO₂, methanol-fueled glow engines, or electric motors), and indoor models (again for pure duration or scale with duration).
When flown outdoors in competition, the usual aim is maximum flight time. The modeler tries to launch into a rising column of air—a thermal. These outdoor models are typically designed for two very different flight modes: climbing rapidly under power or tow, and then gliding slowly in circles with minimal sink rate. Much of the design and flying challenge is maintaining aerodynamic stability in both modes and making a smooth transition between them. Modern models use mechanical or electronic timers to move control surfaces at preset moments.
- Fai generic code
- F1
- Fai glider class
- F1A (also A/2 or Nordic glider)
- F1a projected area
- 32–34 dm²
- F1a minimum weight
- 410 g
- F1a tow line length
- 50 m
- Fai rubber class
- F1B (Wakefield)
- F1b maximum rubber motor
- 30 g
- F1b minimum empty airframe weight
- 200 g
- F1b maximum total area
- 19 dm²
- Mini rubber class
- F1G (Coupe d'Hiver)
Lore & Background
Free flight models have been flown for over two centuries. They are designed to be inherently stable; if disturbed by a gust or thermal they return automatically to stable flight through a combination of design and trim—the relationship between centre of gravity, wing and tailplane incidence, and rudder setting. With much lower wing loading than engine-powered radio-controlled aircraft, most free flight models glide at little more than walking pace and few weigh more than 500 grams. The sole objective of free flight competition is usually flight duration, challenging designers to create the most efficient aircraft within limits on minimum weight, maximum wing area, and motive power. Outdoors, modelers attempt to launch into a thermal, using methods ranging from radio telemetered temperature and wind speed to Mylar streamers or soap bubbles to visualize rising air. Indoor models do not depend on rising air but must maximize efficiency from limited stored energy. Competitions typically involve up to seven rounds per day, each with a maximum flight time hard to achieve without thermal assistance. An automatic on-board time switch upsets the trim when the max is achieved to bring the aircraft down safely. Locating and recovering the aircraft is important; many carry radio location beacons, and flyers use GPS, binoculars, a compass, and a directionally sensitive radio tracking receiver. A day's flying and retrieval may involve 20 miles or so on foot or bike.
Reader's Guide
Free flight is the original form of hobby aeromodeling, establishing the foundational principles of aerodynamic stability and efficient design that underpin all model aviation. Its competitive focus on duration has driven innovation in lightweight structures, variable-pitch propellers, and automatic timer systems that transition the model from powered climb to glide. The sport's categories—gliders, rubber-powered, power (CO2, glow engine, or electric), and indoor—each present distinct engineering challenges. Gliders withstand launch stresses exceeding 60 G and speeds over 140 km/h, made possible by composite materials like carbon, fiberglass, and Kevlar. Rubber-powered models exploit the stored energy of twisted elastic, with automatic variable-pitch propellers and timer-operated changes to wing and tailplane incidence to manage the motor's declining torque. The FAI class codes (F1 for free flight, with subclasses F1A, F1B, F1C, F1D, F1E, F1G, F1H) provide a structured framework for international competition. The sport's legacy includes beginner models like the AMA Cub, Denny Dart, Canarsie Canarie, and Squirrel, which introduce new generations to construction and flight. The smallest rubber powered model, the Flying Flea, built in 1931, was 1.25 inches long and could remain airborne for about one minute, demonstrating the extreme miniaturization possible within free flight.
Did You Know?
- During launch, many gliders withstand 60 G or more and have launch speeds sometimes over 140 km/h.
- The smallest rubber powered model aircraft, the Flying Flea, was 1.25 inches long and could remain airborne for approximately one minute.
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