What is the function of a standby attitude indicator (SAI) and how does it differ from the primary AI?

What is the function of a standby attitude indicator (SAI) and how does it differ from the primary AI?

• A. SAI provides attitude data from an independent source if the primary AI fails; it remains independent of primary instruments.
• B. SAI duplicates the primary AI and has no independence.
• C. SAI provides attitude data using the same source as the primary AI but with lower priority.
• D. SAI provides altitude data instead of attitude data.

Answer: (A)

Redundancy and independence in attitude information are what this is about. A standby attitude indicator provides attitude data from an independent source that stays available if the primary attitude indicator fails. It uses its own gyro source and its own power supply, separate from the primary AI’s electrical or vacuum system, so a fault in the main system doesn’t wipe out attitude information. The primary attitude indicator is the main source of attitude data and is tied to the aircraft’s primary power and systems. The standby isn’t just a less important duplicate; it’s a separate, often battery-backed instrument designed to remain functional when the main system is not. It’s focused on attitude information, not altitude, so it won’t provide altitude data.

Redundancy and independence in attitude information are what this is about. A standby attitude indicator provides attitude data from an independent source that stays available if the primary attitude indicator fails. It uses its own gyro source and its own power supply, separate from the primary AI’s electrical or vacuum system, so a fault in the main system doesn’t wipe out attitude information.

The primary attitude indicator is the main source of attitude data and is tied to the aircraft’s primary power and systems. The standby isn’t just a less important duplicate; it’s a separate, often battery-backed instrument designed to remain functional when the main system is not.

It’s focused on attitude information, not altitude, so it won’t provide altitude data.