Successful propeller pull-out test for gliders
An important part of the “B13 electric” project of the Akaflieg Berlin e.V. is the design of own propeller blades. Anyone who operates a prototype and wants to fly with it (for the purpose of flight testing, for example) is in active contact with the staff of the German Federal Aviation Authority (LBA). There, a decision is made as to whether or not the aircraft is allowed to take to the air in the given configuration. In the case of the B13 electric drive, proof must therefore be provided that the propeller blades can withstand the forces that occur in flight.
The means of choice for this is a propeller pull-out test, carried out at Grasse Zur Composite Testing Berlin. The propeller passed the required test with 15 kN (corresponds to four times the expected load in flight with engine operation J=4). Subsequently, the load was continuously increased. At 25 kN, the first white cracks appeared in the glue-on area, a crack only occurred at 32 kN, but not in the propeller blade structure, but in the glue-on area.