Which combination would cause the APU indication to disappear from the MFD electrical page?

Which combination would cause the APU indication to disappear from the MFD electrical page?

• A. APU available with RPM above 10%
• B. APU not available and APU Master OFF with RPM below 10%
• C. APU running and Master ON with RPM above 50%
• D. APU not available and Master ON with RPM above 20%

Answer: (B)

The display on the electrical page shows the APU only when there is something to report about it—either the APU is available/hookable to the system or it is being commanded to run. If the APU is not available and the APU Master is OFF, with RPM effectively near zero (below 10%), there’s no active or potential APU operation to show. In that situation the system clears the APU indicator from the MFD because there’s no APU activity or readiness to report. That’s why this combination makes the APU indication disappear: the APU is not available and is not being commanded to operate (Master OFF), and it isn’t spinning. In other scenarios, such as when the APU is available and spinning or commanded to run (Master ON and RPM above a meaningful threshold), the MFD would display the APU status. Even if the APU isn’t available but Master is ON, the status would typically still be shown as not available rather than disappear, so the only case that clears the indicator is when there’s no APU activity to reflect.

The display on the electrical page shows the APU only when there is something to report about it—either the APU is available/hookable to the system or it is being commanded to run. If the APU is not available and the APU Master is OFF, with RPM effectively near zero (below 10%), there’s no active or potential APU operation to show. In that situation the system clears the APU indicator from the MFD because there’s no APU activity or readiness to report.

That’s why this combination makes the APU indication disappear: the APU is not available and is not being commanded to operate (Master OFF), and it isn’t spinning. In other scenarios, such as when the APU is available and spinning or commanded to run (Master ON and RPM above a meaningful threshold), the MFD would display the APU status. Even if the APU isn’t available but Master is ON, the status would typically still be shown as not available rather than disappear, so the only case that clears the indicator is when there’s no APU activity to reflect.