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Details
Identification of issue
EASA received a request for an equivalent safety finding (ESF) with CS-E 900 at Amendment 1 for the propeller parking brake installed on a turbine engine.
The function of the propeller parking brake is to stop and hold the propeller when the aeroplane is parked on the ground to permit personnel to move freely around the aeroplane without risk of injury from a windmilling propeller and to facilitate maintenance.
CS-E 900 Amendment 1 reads as follows: “If a Propeller parking brake is provided it must be operated 100 times during the endurance test. It must be applied at the maximum Propeller speed recommended by the Engine constructor”.
The applicant proposes not to perform the compliance demonstration during the engine endurance test, but instead to use a specific bench test (rig test) with representative load and inertia. Hence, the propeller parking brake does not directly comply with CS-E 900 at amendment 1.
The applicant argues that the engine endurance test may not provide adequately representative behavior of the propeller parking brake for certification purposes. While the engine equipped with propeller parking brake is mechanically and electrically representative, the loading aspects cannot be controlled, as these depend upon wind speed and orientation.
Using a rig test allows to reach the maximum torque on the propeller brake unit (PBU) shaft which would occur with strong winds, and which is not easily achievable during engine tests, including the endurance test prescribed by CS E 900.
On both Engine test and rig test, the power supply will not be the aircraft power supply but a representative bench power supply. Therefore, using a rig does not bring under-testing compared to Engine testing.
Considering all the above, the following Equivalent Safety Finding is established.
