Patent ID: 8651817

Claim:
An aerofoil blade assembly comprising: a rotor disc having a radially outer surface provided with an axial slot and a radially inner surface provided with a circumferential slot, wherein a lower region of the axial slot intersects an upper region of the circumferential slot; an aerofoil blade comprising a blade root which is received by the axial slot and which is provided with a locating slot which corresponds to the circumferential slot; a retention key which engages with the circumferential slot and the locating slot to restrict axial displacement of the aerofoil blade with respect to the rotor disc, the retention key being provided with a socket which, when the retention key is engaged in the circumferential slot and the locating slot, is substantially aligned with the axial slot; and a slider for insertion along the axial slot, the slider having an engaging portion for engaging with the socket which, unless correctly aligned with the socket upon insertion of the slider into the axial slot, is obstructed by the retention key such that the slider cannot be fully inserted into the axial slot.