Flight and navigational equipment

This regulation establishes the minimum flight and navigational instruments required for Part 121 air carrier operations. All aircraft must have basic instruments including a heated pitot system, sensitive altimeter, clock with sweep-second hand, outside air temperature gauge, artificial horizon, turn coordinator (or slip-skid indicator if a third attitude system is installed), directional gyro, magnetic compass, and vertical speed indicator.

Certain turbine-powered aircraft must install a third attitude indicator (artificial horizon) beyond the two at the pilot stations. This applies to all turbojets and larger turboprops. The third instrument must run independently from the main electrical system, operate for at least 30 minutes after electrical failure, work without pilot selection, and be clearly visible and appropriately lit.

This ensures pilots maintain critical attitude awareness even during electrical system failures—a vital safety backup when flying in instrument conditions where outside visual references may be unavailable.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*