14 CFR § 25.1321

Each flight, navigation, and powerplant instrument for use by any pilot must be plainly visible to him from his station with the minimum practicable deviation from his normal position and line of vision when he is looking forward along the flight path.

The flight instruments required by § 25.1303 must be grouped on the instrument panel and centered as nearly as practicable about the vertical plane of the pilot's forward vision. In addition—

The instrument that most effectively indicates attitude must be on the panel in the top center position;

The instrument that most effectively indicates airspeed must be adjacent to and directly to the left of the instrument in the top center position:

The instrument that most effectively indicates altitude must be adjacent to and directly to the right of the instrument in the top center position; and

The instrument that most effectively indicates direction of flight must be adjacent to and directly below the instrument in the top center position.

Required powerplant instruments must be closely grouped on the instrument panel. In addition—

The location of identical powerplant instruments for the engines must prevent confusion as to which engine each instrument relates; and

Powerplant instruments vital to the safe operation of the airplane must be plainly visible to the appropriate crewmembers.

Instrument panel vibration may not damage or impair the accuracy of any instrument.

If a visual indicator is provided to indicate malfunction of an instrument, it must be effective under all probable cockpit lighting conditions.