Thrust Balance Piston

A thrust balance piston system has been included in the aft-end of the LM6000 engine to control thrust loading on the No 1B bearing. These loads are imposed by the low pressure compressor and the low pressure turbine and vary with output power. Forward axial loads are applied by varying air pressure in the balance piston air cavity to maintain thrust loads within the capability of the bearing.

The balance piston system consists of the balance piston disk, the balance piston casing, their associated seals, and the domed shaped cavity, formed by these parts. This cavity is pressurized by the stage 11 high pressure compressor bleed air, controlled by a modulating valve mounted externally on the turbine rear frame. The balance piston casing is attached to the aft inner half of the turbine rear frame. The balance piston disk is attached to the low pressure turbine shaft. Thrust is monitored by a total-pressure probe (P48) and static-pressure probe (PS55).