T-MOTOR MF1503 Polymer Folding Propeller

The T-MOTOR MF1503 is a folding two-blade propeller made of polymer with carbon fibre for mid-sized multicopters from T-MOTOR (China). It measures 15 in in diameter with a 5.4 in pitch and is recommended for 1 to 1.5 kg of thrust per rotor.

The figures given in millimetres are 381 for the diameter and 136.1 for the pitch. The 5.4 in pitch is a little over a third of the diameter: flat, laid out for hovering and efficiency. T-MOTOR states the weight per single blade, 24 g; to compare it with complete propellers it is multiplied by the number of blades and the hub added. The maximum thrust is 3 kg. The speed of 7,000 rpm is the recommended maximum speed at 3 kg of thrust and not a limit of the material; the recommended 1 to 1.5 kg of thrust per rotor is about half of that. The blades fold for transport and are opened by centrifugal force in operation.

Legally the aircraft counts: mid-sized multicopters with 15 in propellers fall, depending on take-off mass, into class C2 (under 4 kg) or C3 (under 25 kg). A C2 aircraft keeps 30 m from uninvolved people in subcategory A2, classes C1 to C3 require direct remote ID, and from 250 g the operator must register.

On a folding propeller the hinge and blade seat are the wear points: they must be clean and free of play, and both blades must open evenly. Polymer with carbon fibre tolerates ground contact more forgivingly than pure carbon but picks up nicks at the tip and leading edge that cause imbalance. Propellers are replaced in pairs, and direction of rotation and motor shaft must match.