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The inoperative attitude indicator on the PFD in Figure 2-8 indicates the failure of the AHRS. By understanding which flight instruments are supported by which underlying systems (e.g., ADC, attitude heading reference system (AHRS)), you can quickly understand the source of a failure. It is important to be thoroughly familiar with the operation of the systems and the abnormal/emergency procedures in the pilot’s operating handbook (POH), aircraft flight manual (AFM), or avionics guides. 

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## PFD Failure 

The PFD itself can also fail. As a first line of defense, some systems offer the reversion capability to display the PFD data on the multi‑function display (MFD) in the event of a PFD failure. 

Every aircraft equipped with electronic flight instruments must also contain a minimal set of backup/standby instruments. Usually conventional “round dial instruments,” they typically include an attitude indicator, an airspeed indicator, and an altimeter. Pilots with previous experience in conventional cockpits must maintain proficiency with these instruments; those who have experience only in advanced cockpits must be sure to acquire and maintain proficiency with conventional instruments. 

## Awareness: Using Standby Instruments 

Because any aircraft system can fail, your regular proficiency flying should include practice in using the backup/standby instrumentation in your aircraft. The backup/standby instrument packages in technically advanced aircraft pro vide considerably more information than the “needle, ball, and airspeed” indications for partial panel work in aircraft with conventional instrumentation. Even so, the loss of primary instrumentation creates a distraction that can increase the risk of the flight. As in the case of a vacuum failure, the wise pilot treats the loss of PFD data as a reason to land as soon as practicable. 

## Essential Skills 

1. Correctly interpret flight and navigation instrument information displayed on the PFD. 

2. Determine what “fail down” modes are installed and available. Recognize and compensate appropriately for failures of the PFD and supporting instrument systems. 

3. Accurately determine system options installed and actions necessary for functions, data entry and retrieval. 

4. Know how to select essential presentation modes, flight modes, communication and navigation modes, and methods mode selection, as well as cancellation. 

5. Be able to determine extent of failures and reliable information remaining available, to include procedures for restoring function(s) or moving displays to the MFD or other display. 

## Chapter Summary 

The primary flight instruments can all be displayed simultaneously on one reasonably easy‑to‑read video monitor much like the flat panel displays in laptop computers. These displays are called primary flight displays (PFDs). You must still cross‑check around the panel and on the display, but more 

