FAQ #395
Regular Class 2027: Prop Diameter Constraint

Last Updated On 9/14/2026 10:39:44 AM by

talmadge33

Question
Section 7.3 of the regular class rules state: "The aircraft shall be propelled by either two (2) or four (4) electric motors. There are no restrictions on the make or model of the electric motors." and "Maximum propeller diameter (per motor) shall be twelve (12) inches if two (2) motors are used or nine (9) inches if four (4) motors are used".

Is there a limit to the number of propellers that can be spun by one motor?

In an aircraft configuration utilizing two motors, if each motor spins two propellers, what is the allowed propeller diameter for each propeller?
Answer
Based on team feedback over the last several years, we were asked to remove the power limiter as a requirement. Our solution to prevent abuse of propulsion power, was to heavily regulate the battery and propeller specification. The sum total propeller diameter for a 2 motor design choice is 12 inches per motor. That could be a single propeller with a 12 inch diameter per motor. Or you could drive two propellers per motor with 6 inch diameters each (6 + 6 = 12). Or three propellers with 4 inch diameters (4 + 4 + 4 = 12), etc. With the removal of the power limiter, we have very carefully specified the battery and propeller requirements to size the aircraft payload capability and potential scoring. We don't restrict the number of propeller blades on each propeller.
No Attachments
Rule Numbers
2027:2027.7.3