Aircraft compartment overheat indicator, system, and method

An aircraft compartment temperature indication system for visually detecting at an aircraft exterior an above-threshold temperature within an aircraft compartment proximate to the aircraft exterior, the aircraft compartment temperature indication system comprising:

• a self-powered aircraft compartment thermal indicator removably attached to an aircraft component, said self-powered aircraft compartment thermal indicator comprising:
• an indicator body comprising an indicator body length, said indicator body comprising:
• an indicator body interior;
• an indicator body exterior;
• an indicator body first end visible at an aircraft exterior;
• an indicator body second end positioned within the aircraft compartment and extending into the aircraft compartment a selected distance from the indicator body first end;
• an indicator body second end base;
• an internal piston, said internal piston comprising a piston base, said piston base comprising a piston base first side and a piston base second side, said internal piston further comprising a piston rod, said piston rod comprising a piston rod first end and a piston rod second end, said piston rod second end at least in communication with the piston base first side;
• an indicator body wall, said indicator body wall extending along the indicator body length from the indicator body first end to the indicator body second end, said indicator body wall comprising an indicator body wall outer surface at the indicator body exterior and an indicator body wall inner surface at the indicator body interior;
• a battery compartment configured to house a battery, said battery configured to deliver an electrical current along an electrical circuit, said battery compartment comprising a plurality of battery plates, said battery compartment comprising a battery compartment base, said battery compartment defined by the battery compartment base and the indicator body wall inner surface;
• an indicator body first chamber defined by the indicator body wall inner surface, the piston base first side, and the battery compartment base, said indicator body first chamber comprising a frangible container, said frangible container housing a volume of battery electrolyte;
• an indicator body second chamber defined by the indicator body wall inner surface and the piston base second side, said indicator body second chamber comprising a spring, said spring comprising a spring first end fixedly attached to the piston base, said spring further comprising a spring second end located immediately adjacent the indicator body second end base;
• and
• a degradable retainer, said degradable retainer in communication with said spring, said degradable retainer configured to retain the spring in a compressed spring state within a first temperature range, said degradable retainer configured to degrade at a threshold temperature, said threshold temperature within a second temperature range, said degradable retainer further configured to retain the spring in a compressed spring state while at the first temperature range, said degradable retainer further configured to release the spring from the compressed spring state toward an expanded spring state at the threshold temperature in the second temperature range;
• a visually detectable signaling device located at the indicator body first end, said visually detectable signaling device in communication with the electrical circuit, said visually detectable signaling device further configured to be visually detectable at the aircraft exterior;
• and
• wherein said visually detectable signaling device is configured to activate at and above a threshold temperature.

A method for indicating at an aircraft exterior a temperature exceeding a threshold temperature within an aircraft component compartment, the method comprising:

• positioning a self-powered aircraft compartment thermal indicator in an aircraft component, said self-powered aircraft component comprising an aircraft component outer surface, said aircraft component outer surface positioned adjacent to an aircraft compartment, said self-powered aircraft compartment thermal indicator comprising:
• an indicator body comprising an indicator body length, said indicator body comprising:
• an indicator body interior;
• an indicator body exterior;
• an indicator body first end;
• an indicator body first end through opening;
• an indicator body second end;
• an indicator body second end base;
• an internal piston, said internal piston comprising a piston base, said piston base comprising a piston base first side and a piston base second side, said internal piston further comprising a piston rod, said piston rod comprising a piston rod first end and a piston rod second end, said piston rod second end at least in communication with the piston base first side, said piston rod first end comprising a light-emitting fixture;
• an indicator body wall, said indicator body wall extending along the indicator body length from the indicator body first end to the indicator body second end, the indicator body second end base, said indicator body wall comprising an indicator body wall outer surface at the indicator body exterior and an indicator body wall inner surface at the indicator body interior;
• a battery compartment comprising a plurality of battery plates, said battery compartment comprising a battery compartment base, said battery compartment defined by the battery compartment base and the indicator body wall inner surface;
• an indicator body first chamber defined by the indicator body wall inner surface, the piston base first side, and the battery compartment base, said indicator body first chamber comprising a frangible container, said frangible container housing a volume of battery electrolyte;
• an indicator body second chamber defined by the indicator body wall inner surface and the piston base second side, said indicator body second chamber comprising a spring, said spring comprising a spring first end fixedly attached to the piston base, said spring further comprising a spring second end located immediately adjacent the indicator body second end base;
• and
• a degradable retainer, said degradable retainer in communication with said spring, said degradable retainer configured to retain the spring in a compressed spring state at a first temperature range, said degradable retainer configured to degrade at a threshold temperature, said threshold temperature within a second temperature range, said degradable retainer further configured to release the spring from the compressed spring state while at the first temperature range to an expanded spring state at the threshold temperature in the second temperature range, said threshold temperature is higher than the first temperature range;
• degrading the degradable retainer at the threshold temperature;
• releasing the spring from the compressed spring state to the expanded spring state;
• delivering the piston from a piston initial position to a piston deployed position;
• rupturing the frangible container to form a ruptured frangible container;
• releasing from the ruptured frangible container at least a portion of the volume of battery electrolyte;
• directing at least a portion of the volume of battery electrolyte into the battery compartment to form a battery, said battery configured to produce electrical current;
• directing the piston rod first end through the indicator body first end through-opening to a selected distance beyond the aircraft component outer surface;
• and
• directing an electrical current from the battery to activate the light-emitting fixture to emit light from the light-emitting fixture.