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1- Description of the E-Props extended hub system

2- Existing extended hubs

3- Does your aircraft need an extended hub ?

4- Length of extended hub and spinners : measures

5- Please note




1- Description of the E-Props extended hub system


In leisure aviation, there are not large series as in the automotive industry. Aircraft manufacturers are used to change somes details on their aircraft, particularly engines covers. Sometimes the engines come outside the covers, and sometimes are inside. It depends on the versions... and it is impossible for propellers manufacturers to know all versions of all aircraft.

Usually propellers manufacturers propose aluminium spacers if the engine is inside the engine covers, in order to space the propellers from the covers.


E-PROPS has developed an innovative system to replace the usual spacers in aluminium (heavy, expensive and difficult to assemble) : the extended hubs. For the moment, this light, strong, secure and cheap solution is available for the 3-blade tractor propellers for Rotax serie 9 engines.



presentation video






weight of the spacer (carbon extended hub) = 3.5 gram * Se in mm (including screws)
it means 3.5 gr/mm

To be compare with 20 gr/mm of a usual aluminium spacer (with screws)

Example for the spacer of a Savannah ultralight :

- weight of an E-PROPS extended carbon hub, length 120 mm (including screws) = 0,42 kg

- weight of an usual aluminium spacer, length 120 mm (including screws) = 2,4 kg

it means a reduction of 2 kg !


- PROTECTION of the GEAR BOX : less weight on the gear box

A too big weight hanged to the gear box is reducing its lifetime.

The heavy propellers generate a significant risk of breakage of the gear box.

Reducing the weight of the spacer allows to limit this risk.



The extended hubs are at the same price as the standard hubs.

No need to buy a spacer in addition. Considerable savings !



With an extended hub, the propeller centering is direct. No need of spacers and screws stacks, which can generate vibrations.

A simple system reduces the vibrations risks.



The E-PROPS hubs, standard or extended, are extremely strong.

Material : 100% carbon + epoxy resin high T°

Injection with RTM process (Resin Transfer Molding)

Compact hub for minimum drag and to optimize engine's cooling

No life limitation. Recommended major periodic inspection : 2.000 hrs




montage moyeu prolongé e-props


6 Screws + 1 central nut (for the central screw of the hub)


7 Nord-Lock washers


1 Flange in anodized aluminium


1 upper Half Hub


1 lower extended Half Hub


Option : 5mm counterplate to adjust the length of the hub (only if necessary)

1 reducer flange (on reduced engines) or engine flange (direct drive engine)


6 drive lugs : threaded or smooth


Option : 6 smooth washers => only for the direct drive engines (smooth drive lugs)





Option : 6 nuts => only for the direct drive engines (smooth drive lugs)

In case of threaded drive lugs, the use of nuts is absolutely forbidden.

In case of direct drive engines, the use of threaded drive lugs is absolutely forbidden.

The tightening torque must be applied on the nut side.



3-blade propeller with ISS : 3 blades, 2 half hubs, 1 aluminium flange, 7 Nord-Lock washers, 6 screws, 1 nut
=> It means 20 parts
3-blade propeller with aluminium spacer : 3 blades, 2 half hubs, 1 aluminium flange, 7 washers, 6 screws, 1 nut , 1 aluminium spacer, 6 drive lugs for spacer, 6 washers, 6 nuts, 6 screws and 6 washers for spacer
=> It means 51 parts
The "Extended Hub" solution allows to reduce of 61% the number of parts necessary for the propeller's assembly.


ISS E-Props

hub with integrated spacer 120 mm (for Savannah, for example)

and on the right with a 250 mm spacer



2- Existing extended hubs


For the moment, this light, strong, secure and cheap solution is available for the 3-blade tractor propellers for Rotax serie 9 engines (DURANDAL range).


11 lengths available : from 0 to 110 mm, on 10 mm increments

Extended hubs : 10 - 20 - 30 - 40 - 50 - 60 - 70 - 80 - 90 - 100 - 110 mm


extended hubs eprops propellers

some examples of E-Props extended hubs



3- Does your aircraft need an extended hub ?


Sometimes it is necessary to have a spacer between the propeller and the reducer flange, whan the engine is far inside the engine cover.


It exists 3 configurations :


A) the gear box side plate is outside the engine cover

=> you don't need any spacer


B) the gear box side plate is just at the edge of the engine cover

=> you don't need any spacer. A 5 mm spacer is usually enough to space the propeller from the engine cover.

A picture of your present propeller assembly, taken above the engine and from the side, could help the E-PROPS team to see if a 5 mm spacer is necessary.


C) the gear box side plate is outside the engine cover

=> you need a spacer. An extended hub as proposed by E-PROPS is a very good solution : light, strong and cheap.

To know which extended hub, please see § 4.


Please note :

If your aircraft need an extended hub and if you want a spinner, you must have a spinner assembled by front of the propeller. If your spinner is assembled between the propeller and the gear box side plate, il would not be possible to use it, because the extended hub is a one-piece carbon part, and it is prohibited to cut it (see § 5).


You have 3 solutions :

- you order a complete set : E-Props propeller + extended hub + standard hub. See page : STANDARD SPINNERS

- you take a mini-spinner, which is available for each E-Props propellers, tractor or pusher. Simple, very light and cheap solution. See here : MINI-SPINNERS

- you order an E-Props with a standard hub, and you keep the aluminium spacer you already had before, and your spinner. You just have to check : 1/ if your spacer has a drilling patern 6M8d101,6 ("big" Rotax drilling patern), and 2/ if your spinner is a 3-blade model.





4- Length of extended hub and spinners : measures


The thickness of the standard DURANDAL hub is 80 mm.

Then it is necessary to add the good thickness to replace a spacer.


Drawing of the DURANDAL standard hub, see here i : HEP_hub_durandal.pdf



To order an extended hub, you just need to take a measure. It is very simple.




Procedure :

- remove your current propeller and all its accessories, particularly the aluminium

- put the engine cover back

durandal moyeu standard épaisseur 80 mm

- take two metal rulers : one to be put between the 2 external sides of the engine cover, the other to measure

- out the ruler 1 against the engine cover, in front of the gear box plate, where will be the propeller

- put the ruler 2 perpendicularly to the ruler 1, side which measured staying visible

- note the measure M as on the picture below, or take a picture and send it to [email protected]

- this measure M will allow the E-PROPS team to define the thickness of the extended hub which necessary to your aircraft


mesure capot moteur ULM rotax 912

how to take M measure




The E-Props spinners are assembled on the flange of the propeller, so they are adapted to all hubs configurations

Please note : the back of the spinner arrives just in the back plane of the hub, near the blades feet

The plate of the spinner is adjusted on the middle of the spinner.

More information on the E-Props spinners : page STANDARD SPINNERS


plan du cone eprops



The standard gap between the spinner and the engine cover is usually between 5 and 10 mm.

If you need a larger gap between the spinner and your cover, please ask it at order.



gap spinner eprops

standard gap between spinner and engine cover = between 5 and 10 mm





5- Please note


In case of mistake on the M measure (length of the extended hub) :

- we can change the extended part of the hub

- for this, please send back to E-Props the complete propeller : the 3 blades, the 2 parts of the hub and the screws

(you can keep the accessories, protractor, covers, spinner and its plate)

- please indicate the length of extended hub you want

- we change the extended hub, and we balance the propeller again with the new extended hub

- cost of the change : 100 euros HT / 120 euros TTC + shipment costs

- within about 1 week
- to order this change, you can go to the E-SHOP


NEVER cut an E-PROPS extended hub.

The extended hubs are designed and manufactured for a defined length.

Cut them is similar to destroy the mechanical strength of the hub. This would be very dangereous.

It is absolutely FORBIDDEN to fly with an E-PROPS extended hub which would have been cutted.

There is no risk to do this by accident : it would be very noticeable that a hub has been cutted. If the hub is cutted, it is destroyed.

If you have no the good length, please contact us and we will send the hub you want.





extended hub on a ROTAX's reducer with a spinner