Bypass valve system state indication

An aircraft, comprising:

• a gas turbine engine;
• a fluid system at least one of coupled to, or in fluid communication with, the gas turbine engine, comprising:
• a fluid passage comprising a passage inlet and a passage outlet, wherein the fluid passage is configured to allow a fluid to pass through the fluid passage by entering the passage inlet as an inlet flow and exiting the passage outlet as an outlet flow;
• a bypass valve comprising a bypass inlet and a bypass outlet, the bypass inlet being in fluid communication with the passage inlet, wherein the bypass valve further comprises a piston coupled to a spring, wherein the spring retains the piston in a rest position, and the spring and the piston are configured to block the fluid from passing through the bypass outlet in response to the inlet flow exerting a pressure below a bypass pressure threshold, wherein the piston is in the rest position in the bypass inlet, wherein the bypass inlet comprises an inlet surrounding wall, wherein a portion of the inlet surrounding wall adjacent to the bypass outlet is a bypass slack area, wherein the piston is in the rest position at a slack area end furthest from the bypass outlet, and the piston is configured to move along the bypass slack area toward the bypass outlet in response to a pressure threshold being reached by the inlet flow in the passage inlet before allowing the fluid to pass through the bypass outlet;
• a position sensor coupled to the bypass valve and configured to detect a position of the piston in the bypass valve;
• and
• a control system in electronic communication with the position sensor, wherein the position sensor transmits the position of the piston to the control system, wherein the control system comprises a processor and is configured to determine an impending bypass flow through the bypass outlet in response to the piston being moved to a displaced position along the bypass slack area from the rest position without allowing the fluid to pass through the bypass outlet.

A method for monitoring a fluid passage, comprising:

• passing a fluid through the fluid passage in a fluid system by the fluid entering a fluid inlet as an inlet flow and exiting through a fluid outlet as an outlet flow, wherein the fluid system comprises a bypass valve having a bypass inlet fluidly coupled to a passage inlet and a bypass outlet, wherein the bypass valve further comprises a piston in the passage inlet coupled to a spring, wherein the spring retains the piston in a rest position, and the spring and the piston are configured to block the fluid from passing through the bypass outlet in response to the inlet flow exerting a pressure below a bypass pressure threshold,
• wherein the bypass inlet comprises an inlet surrounding wall, wherein a portion of the inlet surrounding wall adjacent to the bypass outlet is a bypass slack area, wherein the piston is in the rest position at a slack area end furthest from the bypass outlet of the bypass slack area, and the piston is configured to move along the bypass slack area toward the bypass outlet in response to the pressure threshold being reached by the inlet flow in the passage inlet before allowing the fluid to pass through the bypass outlet;
• detecting, by a position sensor coupled to the bypass valve, a position of the piston in the passage inlet;
• determining, by a processor, whether the piston has moved from the rest position;
• and
• determining, by the processor, an impending bypass flow in response to determining that the piston has moved from the rest position to a displaced position along the bypass slack area.