Definitions

The International Civil Aviation Organisation (ICAO) defines all RAs as involving either “a manoeuvre intended to provide separation from all threats” or “a manoeuvre restriction intended to maintain existing separation.” ICAO further breaks down this term as either a corrective RA, which “advises the pilot to deviate from the current flight path” or a preventive RA, which “advises the pilot to avoid certain deviations from the current flight path but does not require any change in the current flight path.”

A TCAS RA Reversal happens when the system issues one command, for example, "Climb, climb now," then issues a different command, such as "Descend, descend now." This can take place for a number of reasons such as the ones described below.