CHAPTER 2. Electronic Flight Instruments

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

  • Correctly interpret flight and navigation instrument information displayed on the PFD.
  • Determine what “fail down” modes are installed and available. Recognize and compensate appropriately for failures of the PFD and supporting instrument systems.
  • Accurately determine system options installed and actions necessary for functions, data entry and retrieval.
  • Know how to select essential presentation modes, flight modes, communication and navigation modes, and methods mode selection, as well as cancellation.
  • 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 information is available in a smaller space in easier to read colors. These convenient displays receive data from sensors such as magnetometers or magnetic flux valves to determine heading referenced to magnetic north. The attitude (pitch and roll) of the aircraft is sensed by the attitude heading reference system (AHRS) and displayed as the attitude gyro would be in conventional instrumentation. The altitude, airspeed, and outside temperature values are sensed in the air data computer (ADC) and presented in the PFD on vertical scales or portions of circles.

The multi-function display (MFD) can often display the same information as the PFD and can be used as a backup PFD. Usually the MFD is used for traffic, route selection, and weather and terrain avoidance. However, some PFDs also accommodate these same displays, but in a smaller view due to the primary flight instrument areas already used in the display. You must learn and practice using that specific system.

It is important to be very careful in the selection (programming) of the various functions and features. In the event of failures, which have a large impact on flight safety and situational awareness, you must always be ready and able to complete the flight safely using only the standby instruments.

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