Mission System Operator (MSO) Standardization Practice Test

In flight, if all five AC generators are lost, how long do the batteries provide emergency power?

30 minutes 15 minutes 45 minutes 60 minutes

Correct Answer:

30 minutes

Explanation:

When all primary AC power is gone, the aircraft must rely on emergency power from the batteries to keep the essential systems running. The batteries are sized to support those critical loads for a fixed period, which in this scenario is 30 minutes. That half-hour window gives the crew enough time to maintain basic flight capability, verify status, and complete a safe approach and landing while the situation is stabilized. The other durations would require a different battery capacity or load mix, but with five AC generators lost, the design expectation is to provide approximately 30 minutes of emergency power for the necessary avionics, instruments, communications, and emergency lighting.

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