Patent ID: 8572985

Claim:
A gas turbine engine pneumatic system for controlling an air bleed valve, comprising: an apparatus for generating a maximum air pressure; a first passage extending between the apparatus and the air bleed valve for applying the maximum air pressure to the air bleed valve to close the air bleed valve against a pressurized air; a second passage connected to the first passage and a variable orifice device included in the second passage to controllably discharge air from the first passage through the variable orifice device, thereby reducing the maximum air pressure applied to the air bleed valve to a predetermined level; and a wash filter located in the pneumatic system for filtering the air discharged through the variable orifice device, wherein the wash filter comprises an inlet and first and second outlets, the inlet and first outlet being connected to a main passage of the apparatus to allow an air flow to be introduced into the inlet, a first portion of the air flow passing through the wash filter without filtration and being discharged through the first outlet, and the second outlet being connected to the first passage to allow a second portion of the air flow introduced into the inlet to be filtered and to enter the first passage.