Definition
A method of releasing the entire contents of a fire-extinguishing agent container into an engine or other protected area in a very short time -- typically a fraction of a second -- through large-diameter outlets opened by a frangible disc or explosive cartridge. Used in aircraft engine fire protection systems to flood the area with extinguishing agent quickly enough to smother a fire before it can re-establish.
Plain English
A way of dumping all the fire-extinguishing chemical at once, almost instantly, so the fire is smothered before it has a chance to grow back.
Context Anchor
Seen in aircraft battery servicing, starting-system troubleshooting, and battery load-test procedures.
Derivation
“Discharge” means to release or let out a charge. In this electrical use, the “charge” is the energy stored in the battery, and “high-rate” means that energy is being taken out quickly.
Why Pilots Care
A battery that cannot sustain high-rate discharge may fail to start the engine, grounding the aircraft or creating an in-flight electrical emergency.
Grounding Statement
When the starter is engaged, the battery must deliver a large burst of electricity in just a few seconds.
Intuition Check
High-rate discharge does not mean the battery is being charged quickly. It means electrical energy is leaving the battery quickly.
Example Sentence 1
When the crew pulled the engine fire handle, the system performed a high-rate discharge of the fire bottle into the engine nacelle.
Example Sentence 2
If the battery passes the high-rate discharge check it is approved for another service interval.