14 CFR § 25.1303

The following flight and navigation instruments must be installed so that the instrument is visible from each pilot station:

A free air temperature indicator or an air-temperature indicator which provides indications that are convertible to free-air temperature.

A clock displaying hours, minutes, and seconds with a sweep-second pointer or digital presentation.

A direction indicator (nonstabilized magnetic compass).

The following flight and navigation instruments must be installed at each pilot station:

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.

An altimeter (sensitive).

A rate-of-climb indicator (vertical speed).

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.

A bank and pitch indicator (gyroscopically stabilized).

A direction indicator (gyroscopically stabilized, magnetic or nonmagnetic).

The following flight and navigation instruments are required as prescribed in this paragraph:

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.

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.