Definition
A section of an aircraft's Pilot's Operating Handbook (POH) or Airplane Flight Manual (AFM) that contains additional operating information, limitations, procedures, and performance data specific to optional equipment, modifications, or systems installed on that particular aircraft. Supplements have the same regulatory weight as the rest of the POH/AFM and must be carried and complied with when the related equipment is installed.
Plain English
Extra pages added to the aircraft's handbook that cover any optional or added-on equipment fitted to that specific aircraft. They tell the pilot how to operate that equipment safely and what rules apply to it.
Context Anchor
Seen in the aircraft flight manual or pilot’s operating handbook, especially when the aircraft has added or optional equipment.
Derivation
From Latin 'supplementum,' meaning 'something added to fill a gap.' In aviation, supplements fill the gap between the standard handbook (which covers the base aircraft) and the actual aircraft a pilot is flying (which often has added equipment the original manual didn't cover).
Why Pilots Care
If an aircraft has optional equipment installed -- such as a GPS, autopilot, or auxiliary fuel tank -- the supplement for that equipment is legally part of the operating limitations. Ignoring it can mean operating the aircraft outside its approved procedures, which is both unsafe and a regulatory violation.
Intuition Check
Do not read “supplements” as optional extra reading. In an aircraft manual, a supplement may be required information for the equipment actually installed in that aircraft.
Example Sentence 1
Before flying the rental Cessna with the upgraded GPS, the pilot reviewed the avionics supplement to understand the unit's operating procedures and limitations.
Example Sentence 2
FAA handbooks include supplements that add new chapters without changing the original text.