A method of operating a gas turbine engine of a multi-engine aircraft is disclosed, where the gas turbine engine has an engine shaft mounted for rotation in a bearing of a bearing assembly. The method comprises limiting motive power supplied to the aircraft by the gas turbine engine by operating the gas turbine engine in a standby mode; and when the gas turbine engine is operating in the standby mode, using an oil piston integrated in the bearing supporting the engine shaft of the gas turbine engine to generate an axial preload force on the bearing.