The E-PROPS are ultra-light and quiet propellers, and they have a very good efficiency. They also are very strong propellers.
Why the E-PROPS are very strong propellers ?
The E-PROPS are made in carbon braid, with continue fibers between upper and lower surfaces of the blade (very high resistance).
The carbon is the material whichs presents by far the best compromise rigidity / weight for long parts, as blades.
An internal spar reinforces the blade.
The HCF (Helical Continuous Fibers) process, specifically designed by E-PROPS, ensures an exceptional strength of the 100% carbon + epoxy resin blade, from leading edge to trailing edge, from blade's foot to tip.
Contrary to the traditional "half-shell" process (used by many propellers manufacturers), fibers are continuous between the intrados and the extrados (carbon braid, made as a sock).
The mechanical resistance of the blade is increased and becomes very high : no slightest risk of blade's explosion by delamination of the leading edge, no possible cracks on the blade or on the hub.
The leading edge of all E-PROPS propellers is reinforced : E-PROPS injects the epoxy resin with a Nanostrength® impact additive (ARKEMA product: high kinetic energy absorption capacity) on the whole leading edge of the blade.
This internal reinforcement, more resistant than a metallic leading edge, leads no detachment and no electrolytic problems. It is extremely resistant.
In very special (and not recommended...) cases, as barefoot flights, it is essential to protect the leading edges with a special tape, used on helicopter rotor blades, which has to be regularly removed (on sale on this e-shop).
The E-PROPS are very light. When they are designed and manufactured with continuous fibers and not in 2 glued half-shell (as many competitor propellers), the ultra-light propellers are more resistant than heavier propellers => less stored kinetic energy, thus fewer damages in case of impact.
All E-PROPS propellers are tested to see how they resist at centrifugal load test.
Centrifugal load tests are very important test in order to define the mechanical resistance of the propellers.
In certified aviation (in Europe), they are defined by EASA Certification Specifications for Propellers (CS-P).
The aircraft propeller must be tested for a period of one hour to a load equivalent to twice the maximum calculated centrifugal load.
The propeller must show no failure or permanent deformation.
E-Props has developped an hydraulic load test bench : high : 3,5 m, weight : 300 kg, and maximum load 40 tonnes. All propellers models are tested on this bench.
Model Ref G74
The maximum centrifugal load on a PLUG'n'FLY propeller at 3.000 tr/min has been calculated by the software LmPTR© : 7.000 N (714 kg).
In this case, the CS-P for certified propellers says that the propeller must be tested for a period of one hour to a load of 14.000 N (1,4 tonnes).
1/ Application of a load of 28.000 N (2,9 tonnes) during 1 hour. Then control : nothing to report
2/ The load increases at 4.000 N per minute
=> Break of one blade at load 32.500 N (3,3 tonnes)
The maximum centrifugal load at 3.000 RPM is 7.000 N, so the safety coefficient of centrifugal load is 4,6.
The propeller can hold 4 times the maximal load during 1 hour without any damages.
The EASA CS-P for certified aircraft propellers says that the propeller must be tested for a period of one hour to a load of 14.000 N.
The propeller has holded a load of 28.000 N during 1 hour, it means twice what is asked by EASA CS-P
for certified propellers.