Frames and classes: how each body sizes a racing drone.

The FAI: F9U, the F9 volume's racing class

The FAI's F9 Drone Sports volume has one racing class, F9U, and its model rules are in chapter C. Everything below is from the 2025 edition, effective 1 May 2025. A 2026 edition is listed by the FAI but could not be opened; its effective date is reported as 1 January 2026 and as 1 June 2026, both from search summaries, so any figure here may have changed in 2026.

The FAI calls a racing drone a "model" and defines a multi-rotor as a rotary-wing radio-controlled model aircraft with at least three power-driven propeller devices. Its limits are on the whole model:

Size is measured by where the motors sit, not by the frame's outline. Under rule C.7.4 officials may stop a competitor's flight if the model no longer meets acceptable safety standards, giving damage after a crash or a dangling battery as examples.

Earlier FAI texts

The 1 kg weight and 330 mm motor circle are the same in the 2019 edition (effective 1 May 2019, when F9U was labelled provisional) and in the FAI's 2024 World Drone Racing Championship Sporting Rules (June 2024). The 2019 edition allowed a 1 percent tolerance for measuring-device inaccuracy on size, weight and battery voltage, and listed the LED device as optional; the 2024 championship rules required one, spread across all arms. Before F9 existed, the FAI's older drone racing page named the class F3U and described it as electric multi-rotors with at least three propellers and a maximum flight weight of 1 kg.

MultiGP: frames by class

MultiGP is an organiser, and its classes apply at MultiGP races only. These come from its Race Class Specifications page, read on 30 October 2026; its full Rule Book was not read, and where it differs the Rule Book and the race's published rules decide.

MultiGP added a Mega Class safety section to its rules in 2019 for drones of 800 to 1050 mm, which it said carried added risk. Whether that section is in the current Rule Book was not checked.

MultiGP's figures are not the FAI's. MultiGP Open caps weight at 800 g where F9U allows 1 kg, and MultiGP measures the frame diagonally where the FAI uses a circle around the motor axes. Neither rule applies at the other's races. More on MultiGP classes and the FAI F9U rules.

About size words

The hobby talks about "5-inch" quads and "Tiny Whoops". This site's research found no body that defines a class by those names other than MultiGP's own Whoop and 5" Spec entries, so on this site "Whoop" means MultiGP's Whoop class as written.

Ducts and propeller guards

The racing bodies have pulled in different directions here. MultiGP's Whoop class requires a ducted frame. The FAI's 2019 edition forbade any propeller protection device on an F9U model. The 2025 edition's change log records that this ban was removed in the changes effective 1 January 2020, with the FAI stating there was no safety reason to prohibit such devices. The 2025 text simply no longer bans them; dropping a ban is not a statement that guards or ducts prevent injury. No BMFA, MAAC or MAAA rule on propeller guards or indoor whoop frames was found.

Indoor micro aircraft: the AMA

The Academy of Model Aeronautics (AMA), a US association, sets weight limits for indoor FPV flying in its Document #551 (its Executive Council approval is dated 04/05/2014). An FPV ultra-micro aircraft is limited to 150 g all-up weight and an FPV micro aircraft to 300 g, counting the aircraft, propulsion, radio control, FPV equipment, any autopilot and batteries. The document says AMA members flying FPV indoors may fly these aircraft without a spotter or buddy-box, subject to the other conditions in its article 3. These are association rules for AMA members, not law, and the copy read is dated 2014; whether it is AMA's current version was not confirmed.

League-built drones

At least one organiser has supplied the aircraft itself. According to Wikipedia (a secondary source), the Drone Racing League built its drones in-house so that every pilot raced identical LED-covered aircraft: Racer2 in 2016, Racer3 from 2017 and Racer4 from the 2019 season. Wikipedia also says its RacerX, built in 2017, once held a Guinness World Record for the fastest battery-powered remote-controlled quadcopter, at a recorded 163.5 mph. The FCC, in a 2018 Notice of Apparent Liability (FCC 18-71), quoted the league's own description of pilots flying custom-built quadcopters at speeds of up to 120 mph. Wikipedia further says the league is no longer active and that its assets, including Racer4 drones, were auctioned in 2026; that rests on Wikipedia alone and is unconfirmed.

Weight and the law

Aviation authorities also draw lines by weight, and they draw them differently in each country: the US registration and Remote ID rules, the UK's Flyer ID and Operator ID thresholds, and the EU's class marks all use different figures. These are covered country by country on the US, UK and EU law pages and on class marks. A racing body's weight limit never replaces them.