Definition
A fire detection system that uses individual heat-sensitive sensor units (spots) placed at specific locations where a fire is most likely to occur, with each sensor wired using two electrical terminals — one connecting the sensor to the warning circuit and the other connecting it to aircraft ground. When a sensor reaches its set temperature, it closes the circuit between its two terminals and triggers a fire warning in the cockpit.
Plain English
A fire-warning system made up of small heat sensors placed at specific spots inside the aircraft. Each sensor has two wires: one to the warning system, one to ground. When a sensor gets hot enough, it completes the circuit and the fire warning comes on.
Context Anchor
Seen in aircraft maintenance manuals and fire detection system descriptions, especially when checking engine, heater, or other fire-warning detector installations.
Derivation
‘Spot-type’ refers to placing sensors at individual spots rather than running a continuous sensing element along a length. ‘Two-terminal’ means each sensor has two electrical connection points — one to the circuit, one to ground — as opposed to single-terminal designs that ground through the sensor’s mounting body.
Why Pilots Care
Provides reliable, localized fire warning so crews can take immediate action before a fire spreads.
Grounding Statement
This system is like placing several small heat watchers in key locations, with each watcher responsible only for the heat at its own spot.
Intuition Check
Do not read “spot-type” as meaning a small or minor fire system. It means each detector senses heat at one specific location rather than along a continuous path.
Example Sentence 1
The maintenance manual specifies a two-terminal spot-type fire detection system in the engine nacelle, with sensors located near the hottest sections.
Example Sentence 2
After replacing a damaged sensor, the crew performed a functional check of the two-terminal spot-type fire detection system before the next flight.