14 CFR 25.1303 - Flight and navigation instruments.
(1) A free air temperature indicator or an air-temperature indicator which provides indications that are convertible to free-air temperature.
(2) A clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation.
(3) A direction indicator (nonstabilized magnetic compass).
(b) The following flight and navigation instruments must be installed at each pilot station:
(1) An airspeed indicator. If airspeed limitations vary with altitude, the indicator must have a maximum allowable airspeed indicator showing the variation of VMO with altitude.
(2) An altimeter (sensitive).
(3) A rate-of-climb indicator (vertical speed).
(4) 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 on large airplanes with a third attitude instrument system useable through flight attitudes of 360° of pitch and roll and installed in accordance with § 121.305(k) of this title.
(5) A bank and pitch indicator (gyroscopically stabilized).
(6) A direction indicator (gyroscopically stabilized, magnetic or nonmagnetic).
(c) The following flight and navigation instruments are required as prescribed in this paragraph:
(1) A speed warning device is required for turbine engine powered airplanes and for airplanes with VMO/MMO greater than 0.8 VDF/MDF or 0.8 V D/MD. The speed warning device must give effective aural warning (differing distinctively from aural warnings used for other purposes) to the pilots, whenever the speed exceeds VMO plus 6 knots or MMO 0.01. The upper limit of the production tolerance for the warning device may not exceed the prescribed warning speed.
(2) A machmeter is required at each pilot station for airplanes with compressibility limitations not otherwise indicated to the pilot by the airspeed indicating system required under paragraph (b)(1) of this section.