Plain English Meaning

The strongest sideways wind that test pilots actually proved the airplane could handle during the testing required to get it approved. It is shown in the airplane's handbook so pilots have a benchmark, but it is not a hard maximum the airplane is forbidden to exceed.

Full Definition

The highest crosswind velocity, measured at 90 degrees to the runway, in which an aircraft was successfully flown and landed during certification testing by the manufacturer's test pilots. It is published in the Pilot's Operating Handbook (POH) or Airplane Flight Manual (AFM) as a reference value, not as a regulatory or structural limit on the aircraft.