Selectable barrier filtration system

An aircraft, comprising:

• an engine comprising an engine compressor intake;
• a plenum;
• an inlet barrier filter associated with the plenum, through which air can selectively enter the plenum;
• an inlet duct associated with the plenum, through which air can selectively enter the plenum;
• a bypass door associated with the inlet duct, the bypass door being configured to selectively change an amount of air allowed to pass through the inlet duct and to the engine compressor intake;
• and
• a filter airflow change device configured to change an amount of airflow allowed through the inlet barrier filter and to the engine compressor intake;
• wherein the filter airflow change device comprises a tubular slide valve and a carrier duct and wherein the slide valve is configured to receive at least a portion of a tubular portion of the carrier duct;
• wherein when the tubular slide valve is fully extended relative to the carrier duct, airflow from the inlet duct to an engine intake duct via the inlet barrier filter is substantially reduced and airflow to the engine intake duct via the inlet duct is substantially increased;
• and
• wherein movement of the tubular slide valve relative to the carrier duct changes an amount of longitudinal overlap between the tubular slide valve and the carrier duct.

A method of operating an aircraft, comprising:

• selectively providing a first airflow path between an inlet duct and an engine compressor intake;
• selectively providing a second airflow path between an inlet barrier filter and the engine compressor intake;
• and
• operating a filter airflow change device configured to change an amount of airflow allowed through the inlet barrier filter;
• wherein the filter airflow change device comprises a tubular slide valve and a carrier duct and wherein operating the slide valve comprises changing an amount of a tubular portion of the carrier duct received within the slide valve;
• fully extending the tubular slide valve relative to the carrier duct so that airflow from the inlet duct to an engine intake duct via the inlet barrier filter is substantially reduced and airflow to the engine intake duct via the inlet duct is substantially increased;
• and
• wherein movement of the tubular slide valve relative to the carrier duct changes an amount of longitudinal overlap between the tubular slide valve and the carrier duct.