Shape memory alloy actuated fire and overheat detector

An aircraft duct overheat condition sensing system, comprising:

• a linear detector element, including:
• an outer sheath having a first end and a second end;
• one or more shape memory responsive elements within the outer sheath and between the first end and the second end;
• and
• first and second conductive wires passing through at least a portion of the outer sheath and through the one or more shape memory responsive elements;
• wherein the one more shape memory responsive elements include a shape memory actuator surrounding the first and second conductive wires and that has an expanded size and a contracted size and that is sized and arranged such that when the shape memory actuator is in the contracted state the first and second conductive wires contact one another and when the shape memory actuator is in the expanded state the first and second conductive wires do not contact one another;
• wherein the linear detector element further includes at least one separator element surrounding the first and second conductive wires and configured such that the first and second conductive wires are electrically separated from one another when the SMA actuator is in the expanded state;
• and
• a controller electrically connected to the first and second conductive wires and configured to determine when the first and second conductive wires are contacting one another.