What Are Adjustable Bolted Propellers?

adjustable bolted propeller
Image: Rolls-Royce

An adjustable bolted propeller, like the one pictured above for Britain’s new QE-class aircraft carrier, feature fixed-pitch blades which are installed on the hub after machining, as compared to the entire propeller being machined at once. This enables the pitch of the blades to be increased or decreased during yard periods should variations in hull resistance warrant such a change.

Rolls-Royce notes, “In comparison to conventional monobloc fixed pitch propellers the ABP has higher quality blade machining and reduced overall weight, which give easier shipment, handling and mounting.”

Transporting a monoblock fixed-pitch propeller, such as this one for Maersk’s giant Triple-E class containership can be a significant undertaking.

While at Wartsila’s facility in Trieste, Italy last year, we saw a few blades being readied for transport:

Wärtsilä propeller blade

And the associated hub (controllable reversible pitch):

Wärtsilä controllable pitch propeller