Plain English Meaning

The set of working instruments and radios on board that the aircraft needs in order to be flown safely and legally in the clouds, on instruments alone, rather than by looking outside.

Full Definition

The instruments, navigation receivers, communication radios, and supporting systems that an aircraft must have installed and operational to be legally and safely flown under Instrument Flight Rules. This typically includes attitude, heading, and altitude instruments; navigation equipment appropriate to the route and approaches to be flown (such as VOR, GPS/WAAS, DME, or ILS receivers); two-way radio communication equipment; a ; and any equipment specifically required by the , the route, or the .