Français / English







moment d'inertie hélices




The inertia of an object is its capacity to resist a variation of speed. The slowness is directly connected to the mass of the object and thus confronts in kg. For rotating objects, the mass is not a sufficient information. The mass of the object is associated with its distance by report the axis of rotation, in order to compare the capacity of resistance with a variation of angular speed.

It is the moment of inertia, which confronts kg.cm ² there.



The moment of inertia is a very important data for the propellers



Indeed, the aeronautical engines are mostly piston motors. The brace undergoes a push of the connecting rod in every tour in 2-strokes engines, and both tours in 4-strockes engines. The brace is accelerated during an about-turn, and is slowed down during the rest of the cycle. It is the inertia of all the rotary set which is going to allow to assure the rise of pistons and regularization of the rotation.


The propeller makes the biggest steering wheel of inertia. If it is pulled by a reducer, the points of engine torque will be supported by the reducer. If it is directly bound on the brace (for direct drive engines), this one will support all the efforts. The efforts are besides passed on through all the system: the braces of redrive engines can also suffer if the moment of inertia of the propeller is too high. And the screws of the propeller are submitted to the same efforts.


Using of a propeller with a moment of inertia upper to the values indicated by the engines manufacturers is going to decrease of the longevity, even to break the reducer or the screws of the propeller.


That's why the engines manufacturers indicate the maximum values of moment of inertia of the propellers which can be adapted to their engines :

- Rotax 582 reducers A & B : 3000 kg.cm²

- Rotax 582 reducers C & E : 6000 kg.cm²

- Rotax 912, 912S, 912iS, 914 : 6000 kg.cm²

- Jabiru 2200 : 3000 kg.cm²


In case of problems linked to the use of an unsuitable propeller, engines manufacturers refuses any guarantee.


The moments of inertia of Hélices E-Props are calculated when the propellers are designed. Then the data are verified and measured for each propeller.





Measure of the moment of inertia of the propeller

Technical document done by ROTAX ref SI11UL91E :





moment d'inertie hélices e-props



hélice e-props mesure du moment d'inertie

measure of the moment of inertia - E-Props propeller carbon





abaque moment d'inertie hélice

click to open





The E-Props propellers are very light and have a low moment of inertia.

Example 1 :

- engine Jabiru 2200 => maximum moment of inertia : 3000 kg.cm²

- VORPALINE propeller for this engine, diameter 152 cm => moment of inertia = 1500 kg.cm²


Example 2 :

- engine Rotax 912 => maximum moment of inertia : 6000 kg.cm² max

- DURANDAL 80 for this engine, diameter 190 cm => moment of inertia = 4400 kg.cm²