Measures of Propellers Moments of Inertia

The moment of inertia is a very important data for the propellers. Some explanations here : Propellers and Moment of Inertia

As a comparison, E-PROPS measured the Moments of Inertia of some propellers for Rotax 912 : GT wood, Duc Swirl and Flash, E-Props, using the method recommended by Rotax. Here are the values :

Maximum Moment of Inertia Rotax 912, 912S, 912iS, 914 : 6 000 kg.cm²

The measured propellers respect the Rotax limitation. The moment of inertia of the 3-blade E-Props (2300) is between that of the 2-blade Swirl 1 (2100) and the 2-blade Flash (2500). This contradicts certain assertions that can be heard here and there that an ultra-light propeller has an “insufficient” moment of inertia. An ultra-light propeller can – and must – perfectly respect the limitation of the moment of inertia indicated by the engine manufacturers.

The use of a propeller with a moment of inertia higher than the limitations of the engine manufacturers leads to a reduction in service life, or even a breakage of the reducer, the crankshaft or the propeller fastening screws.

If you want to know more about this subject, read Jérémie Buiatti’s article on the influence of propeller inertia (in French, Colloques de Cachan 2016).