14 CFR § 121.305 - Flight and navigational equipment.
(a) An airspeed indicating system with heated pitot tube or equivalent means for preventing malfunctioning due to icing.
(b) A sensitive altimeter.
(c) A sweep-second hand clock (or approved equivalent).
(d) A free-air temperature indicator.
(e) A gyroscopic bank and pitch indicator (artificial horizon).
(f) A gyroscopic rate-of-turn indicator combined with an integral slip-skid indicator (turn-and-bank indicator) except that only a slip-skid indicator is required when a third attitude instrument system usable through flight attitudes of 360° of pitch and roll is installed in accordance with paragraph (k) of this section.
(g) A gyroscopic direction indicator (directional gyro or equivalent).
(h) A magnetic compass.
(i) A vertical speed indicator (rate-of-climb indicator).
(j) On the airplane described in this paragraph, in addition to two gyroscopic bank and pitch indicators (artificial horizons) for use at the pilot stations, a third such instrument is installed in accordance with paragraph (k) of this section:
(1) On each turbojet powered airplane.
(3) On each turbopropeller powered airplane having a passenger-seat configuration of 30 seats or fewer, excluding each crewmember seat, and a payload capacity of 7,500 pounds or less that is manufactured on or after March 20, 1997.
(4) After December 20, 2010, on each turbopropeller powered airplane having a passenger seat configuration of 10-30 seats and a payload capacity of 7,500 pounds or less that was manufactured before March 20, 1997.
(k) When required by paragraph (j) of this section, a third gyroscopic bank-and-pitch indicator (artificial horizon) that:
(1) Is powered from a source independent of the electrical generating system;
(2) Continues reliable operation for a minimum of 30 minutes after total failure of the electrical generating system;
(3) Operates independently of any other attitude indicating system;
(4) Is operative without selection after total failure of the electrical generating system;
(6) Is appropriately lighted during all phases of operation.