14 CFR § 23.2615

Installed systems must provide the flightcrew member who sets or monitors parameters for the flight, navigation, and powerplant, the information necessary to do so during each phase of flight. This information must—

Be presented in a manner that the crewmember can monitor the parameter and determine trends, as needed, to operate the airplane; and

Include limitations, unless the limitation cannot be exceeded in all intended operations.

Indication systems that integrate the display of flight or powerplant parameters to operate the airplane or are required by the operating rules of this chapter must—

Not inhibit the primary display of flight or powerplant parameters needed by any flightcrew member in any normal mode of operation; and

In combination with other systems, be designed and installed so information essential for continued safe flight and landing will be available to the flightcrew in a timely manner after any single failure or probable combination of failures.