Why E-Props are particularly well-balanced ?

The E-PROPS propellers are known as ultra-light propellers, with a very low moment of inertia and very well balanced. Here below some explanations.

1. E-Props are ultra-light

E-Props are Carbon propellers with Titanium leading edge protection, designed and engineered to be as light as possible yet extremely strong.

The lighter a propeller, the easier it is to get a good balance.

Rotax recommends a balancing tolerance of 0.5 g/m.
At E-Props, we aim for a balancing tolerance of 0.2 g/m, to avoid vibrations and ensure smooth, comfortable propeller operation.

On gear-drive engines like Rotax, the propellers are mounted on the gearbox flange. It is inevitable that the “gearbox bearing / gearbox shaft / eventual spacer between propeller and gearbox flange” assembly will have a slight form error.

Let’s assume a form error of 0.1 mm (current value).
This will give :

• propeller weight = 2000 g => unbalance 0.2 g/m (acceptable to E-Props and within Rotax tolerance)
• propeller weight = 6000 g => unbalance 0.6 g/m (outside Rotax tolerance)
• propeller weight = 12,000 g => unbalance 1.2 g/m (well outside Rotax tolerance)

When the unbalance generated by shape defects is greater than 0.5 g/m, which is very often the case with E-Props’ competitors, some propellers on the market require dynamic balancing of the propeller on the aircraft after each assembly/disassembly of the propeller.

This is not the case with E-Props, whose light weight means they can easily withstand shape defects.

2. E-Props have integrated centering drive lugs

Competitors’ propellers use steel centering drive lugs, which increase mounting dispersion (or centering / coaxiality error).

E-Props have carbon drive lugs integrated into the carbon spacer that mounts on the gearbox flange. In addition to saving 125 g, these carbon drive lugs reduce backlash and improve assembly precision, enabling excellent balance to be maintained.

3. E-Props have an integrated spacer

Competing propellers use aluminum spacers which increase mounting dispersion (or centering / coaxiality error).

E-Props has developed an exclusive system to replace the usual aluminum spacers: integrated carbon spacers (ESU). They are ultra-light, 13 times lighter (!) than aluminum spacers, at 1.5 g/mm instead of 20 g/mm.
See more data on this page => E-PROPS ESU Spacers

Example 1, for a 40 mm long spacer:
– the traditional aluminum model weighs 800 g
– the E-Props carbon spacer weighs only 60 g

Example 2, for a 120 mm long spacer:

The E-Props carbon spacer eliminates shape defects in spacer stacks, screw sets and centering drive lugs, making propeller balancing much easier.

4. E-Props are mass-produced

E-Props produces 75,000 carbon parts a year (in 2024).
Each blade model is mass-produced, so it’s easy to have blades with a very close static moment to facilitate balancing. What counts for perfect balancing is the distribution of mass along the entire length of the blade : the static moment. This is the sum of the products of the surfaces multiplied by the lever arm normal to the reference axis.
See detailed explanations on this PDF file : E-PROPS BALANCING

5. All E-Props are balanced before shipment

Each propeller is carefully balanced by the E-Props team: blades + hub + spacer, on high-precision digital balancing benches designed and built in-house.
The computer system imposes a maximum tolerance of 0.2 g/m, and quality control must validate this value before authorizing shipment.

Ultra-light parts, ultra-low balancing tolerances and extremely precise assemblies result in perfectly balanced propellers that generate very little vibration.

And it really works : E-Props propellers are known for their exceptional smoothness and comfort in flight. The many COMMENTS and FEEDBACK available on the e-props.fr website bear this out. 🙂