What is the standby instrument system and when would you rely on it?

• A. Standby attitude, airspeed, and altitude indicators; relied upon if primary instruments fail or are unreliable.
• B. Standby system provides only cabin pressure information.
• C. Standby system is a backup autopilot.
• D. Standby system displays navigation data only.

Answer: (A)

Standby instruments are a separate, independent set of flight data that keeps you informed when the main cockpit instruments aren’t available or are unreliable. They include the standby attitude indicator, the standby airspeed indicator, and the standby altimeter. Because they’re powered by an independent electrical source, they stay functional even if the primary instruments fail or give conflicting readings.

You rely on them whenever the primary instruments are inoperative or unreliable. In those moments, they provide the essential cues you need to maintain control: the horizon to hold the correct attitude, the airspeed to avoid stall or overspeed, and the altitude reference to stay on the assigned flight level or altitude. This is especially important during IMC or abnormal electrical conditions, and you would use the standby data until normal instruments are restored or an alternate method of information becomes available. Note they give basic flight data only and do not replace navigation or autopilot functions.