Definition
Information a pilot provides to ATC or rescue personnel describing the survival and safety equipment carried on the aircraft, particularly when declaring an emergency, filing a flight plan over remote terrain, or responding to a search and rescue inquiry. Typical items reported include life rafts, life vests, survival kits, emergency locator transmitters, signaling devices, fire extinguishers, oxygen, and portable radios.
Plain English
It's the list of safety gear you have with you on the aircraft -- things like life rafts, vests, survival kits, and emergency beacons -- that you tell ATC or rescuers about so they know what you have to work with if something goes wrong.
Context Anchor
Seen in flight planning, emergency planning, and communications where a pilot may need to report what safety or survival equipment the aircraft is carrying.
Derivation
“Emergency” comes from the idea of something that suddenly arises and needs immediate action. “On board” originally referred to being aboard a ship, and in aviation it means carried in the aircraft.
Why Pilots Care
Knowing precisely what emergency equipment is aboard enables immediate access during an actual emergency and satisfies regulatory requirements for certain flight operations.
Intuition Check
Do not assume this means only equipment required by regulation. Here it means the emergency gear actually carried in the aircraft and available for use.
Example Sentence 1
Center, Cessna Three Four Yankee, declaring an emergency, four souls on board, three hours of fuel, emergency equipment on board includes life vests and an ELT.
Example Sentence 2
During the safety briefing, passengers were shown the location of emergency equipment on board.