FAA Instrument Flight Instructor (FII)Instruments and SystemsMedium
An aircraft equipped with a glass cockpit primary flight display (PFD) and multi-function display (MFD) experiences a PFD failure while in IMC. What is the pilot's appropriate immediate action?
- ADisregard the failure since the MFD cannot display primary flight data
- BSwitch to the standby vacuum system to restore the PFD
- CDeclare an emergency and descend immediately below the clouds
- DSelect the reversionary (backup) mode to display flight instruments on the MFD
Show answer & explanationAnswer & explanation
Correct answer: D. Select the reversionary (backup) mode to display flight instruments on the MFD
Most integrated glass cockpit systems include a reversionary mode that allows the MFD to display essential flight instrumentation (attitude, airspeed, altitude, heading) if the PFD fails, maintaining situational awareness without needing to descend or declare an emergency solely for this failure.
Why the other options are wrong
- A. The MFD is specifically designed to assume PFD functions in reversionary mode.
- B. A standby vacuum system relates to mechanical gyro instruments, not electronic PFD failures.
- C. A PFD failure alone does not require an emergency descent if backup display capability exists.
Reversionary Mode (Glass Cockpit)
A backup display mode that allows the multi-function display (MFD) to present primary flight instrument data if the primary flight display (PFD) fails.
- Activated automatically or manually via a reversion switch
- Combines attitude, airspeed, altitude, and heading data on the MFD
- Distinct from standby (backup) instruments, which are separate physical gauges
Memory trick: PFD dies, MFD steps in — reversion mode saves the day.