Fly within the rules
This page explains what aviation authorities, model-aircraft associations, racing bodies and researchers publish. It is not legal advice and not a substitute for your aviation authority's own rules, a club safety officer or proper training.
An aid, not a ruling
This tool compares figures you type in with the F9U model limits in the FAI's F9 rules, 2025 edition (effective 1 May 2025, Section C.1). A 2026 edition exists and was not read here; its effective date is reported as 1 January 2026 in one source and 1 June 2026 in another, and its limits may differ. The event's officials decide whether a model may race. The FAI rules also say radio frequencies and power must follow the host country's rules, which this tool does not check. MultiGP and other organisers set their own classes: see MultiGP classes.
Check a model
The limits the tool uses
All figures are from the FAI Sporting Code, Section 4, Volume F9 (Drone Sport), 2025 edition, Section C.1, which covers the F9U class.
| Item | F9U rule (2025 edition) | Article |
|---|---|---|
| Take-off weight, batteries included | At most 1 kg | C.1.1 |
| Size | All motor axes inside a circle of 330 mm diameter | C.1.1 |
| Battery | Electric motors only; packs up to 6S; no cell above 4.25 V when fully charged (the rule gives 17 V for a 4S pack and 25.5 V for a 6S pack) | C.1.2 |
| Propellers | At most 6 inches (15.2 cm) in diameter; all-metal propellers forbidden | C.1.3 |
| Video | Analogue or digital systems in the 5.8 GHz band only; at most 25 mW output, on the ground and in the air | C.1.5 |
| Fail-safe and pit mode | A fail-safe whose triggering stops the motors, and a pit mode whose triggering cuts the video transmitter's power | C.1 |
What the tool does not check
- The 2026 edition of the F9 rules, which was not read here. Its limits may differ from the 2025 figures above.
- Motor tilt. The 2025 rules allow each motor at most 15 degrees of tilt each way from the reference plane (C.1.2).
- The radio control link. The rules allow any 2.4 GHz spread-spectrum system, require frequencies and power to follow the host country's rules, and let organisers list other modules (C.1.4).
- Banned functions. The rules forbid pre-programmed manoeuvres, automatic positioning or path correction and pre-programmed video-power increases, while allowing recovery modes the pilot switches on (C.1).
- Goggles, lights and markings: where the goggle antenna may sit (C.1.5), an LED unit an organiser may require (C.1.6), and the national mark and licence number each model carries (C.1.7).
- The law where you fly. Aviation and radio rules differ by country: see flying with goggles and observers and radio rules by country.
- Other organisers' classes, such as MultiGP's, which set different limits.