Motors and propellers: what the rules allow on a racing model.

Motors under the FAI's F9U rules

The FAI's F9U model rules, in the F9 Drone Sports volume, 2025 edition (effective 1 May 2025), article C.1.2, allow electric motors only. Each motor may be tilted at most 15 degrees in each direction from the model's reference plane. The F9U rules as read for this site give no motor size or power figure. The motors are bounded instead by the whole-model rules: the 1 kg weight and 330 mm motor circle in C.1.1 and the battery rule in C.1.2. A 2026 edition exists but was not read (its effective date is reported as 1 January 2026 and as 1 June 2026), so these may have changed.

The earlier texts agree on electric motors only: the 2019 edition (effective 1 May 2019, article C.1.2) and the FAI's 2024 World Drone Racing Championship Sporting Rules (June 2024, article 2.2). The 2019 edition carried a note that the FAI would consider a maximum amount of energy per race, checked by an electronic device or logger. That was a note, not a rule.

Motors in MultiGP's classes

MultiGP, an organiser, uses motor sizes as class limits on its Race Class Specifications page (read 30 October 2026; its Rule Book was not read). These apply only at MultiGP races.

What the size labels mean

No standards body or regulator definition of these labels was found. A trade-press source, Oscar Liang (13 May 2018), describes a four-digit motor size such as 2207 or 2306 as giving the stator width in its first two digits, and its height in the last two. That is a trade reading of a hobby convention, not a defined standard, and it is unconfirmed by any body.

KV is used by MultiGP as a motor rating, as in the Micro class's 4500 to 4600 KV. Trade sources are reported, in a search summary only, to describe KV as revolutions per minute per volt. No regulator or standards body definition was found, so that meaning is unconfirmed here.

Propellers under the FAI's F9U rules

The 2025 edition simply no longer bans guards; dropping a ban is not a statement that guards prevent injury.

Propellers in MultiGP's classes

MultiGP's class page limits Whoop propellers to 31 mm and sets 3.1-inch propellers for Micro. For Pro Spec and Freedom Spec the propeller is announced per event, with the Pro Spec entry recommending a set it labels 7x4x3. Open has no propeller limit.

The MAAA's stricter material rule

The Model Aeronautical Association of Australia (MAAA), whose rules apply to its own members at MAAA clubs and affiliated sites, bans carbon fibre and metal propellers in racing multirotors in its policy MOP066 (revision of 19 August 2019, section 9.6). The FAI's 2025 F9U rule forbids only all-metal propellers. The two bodies disagree on carbon fibre, and each rule applies only within its own framework. Neither is law.

Replacing propellers on a class-marked drone (EU)

Spain's aviation safety agency, AESA (page last modified 21 May 2026), says that on a drone carrying an EU class mark, replacing a part with one of the same physical and functional characteristics, giving a propeller of the same design as its example, does not breach the CE marking requirements, whereas changes that take weight or performance outside the manufacturer's specifications do. That is one national authority's reading of the EU framework. More on class marks.

Why propellers draw attention

A report by the FAA's UAS Center of Excellence (ASSURE), Task A4 (2017), studied injuries from small drones and named rotor diameter as the characteristic most significant for laceration injuries. It was not a study of racing drones. Injury studies are covered one by one, never combined, on the safety pages. Any injury from a propeller needs medical care.

Motors and the FCC Covered List

In the United States, the FCC's fact sheet of 7 January 2026 names motors among the drone "critical components" covered by its December 2025 Covered List additions. The same fact sheet says no part now needs FCC authorisation that did not need it before. What that means is set out on the FCC Covered List.