Connection of rotatable parts

A gas turbine engine having a first rotatable part and a second rotatable part, each of the first and second rotatable parts being rotatable about a rotational axis, wherein:

• the first rotatable part and the second rotatable part are fixed together so as to be fixed relative to each other using a primary joining mechanism and a secondary joining mechanism;
• the primary joining mechanism is a mechanical fastener;
• the secondary joining mechanism is an interlocking feature through which the first and second rotatable parts are engaged so as to resist relative axial movement of the first and second rotatable parts, the interlocking feature comprising a first interlocking element provided on the first rotatable part and a second interlocking element provided on the second rotatable part, the first and second interlocking elements being engaged with each other so as to provide the resistance to axial movement;
• the first interlocking element is provided by an engagement surface of the first rotatable part that extends substantially perpendicularly to the radial direction;
• the second interlocking element is provided by an engagement surface of the second rotatable part that extends substantially perpendicularly to the radial direction and engages the engagement surface of the first rotatable part;
• and
• the engagement surface of the first rotatable part comprises at least one protrusion that interlocks with at least one corresponding protrusion formed on the engagement surface of the second rotatable part.

A method of fixing a first rotatable part and a second rotatable part of a gas turbine engine together, comprising:

• mechanically fastening the first and second rotatable parts together using a mechanical fastener;
• and
• interlocking a first interlocking element provided on the first rotatable part with a corresponding second interlocking element provided on the second rotatable part, the first and second interlocking elements being engaged with each other so as to provide resistance to axial movement, wherein:
• the first interlocking element is provided by an engagement surface of the first rotatable part that extends substantially perpendicularly to a radial direction;
• the second interlocking element is provided by an engagement surface of the second rotatable part that extends substantially perpendicularly to the radial direction and engages the engagement surface of the first rotatable part;
• and
• either:
• (1) the engagement surfaces of the first and second rotatable parts are at least a segment of a frusto-cone, with an axis of the frusto-cone being the rotational axis of the gas turbine engine;
• or
• (2) the engagement surface of the first rotatable part comprises at least one protrusion that interlocks with at least one corresponding protrusion formed on the engagement surface of the second rotatable part.