An electronic flight display, EFD, consists of a primary flight display, PFD, and a multifunction display, or MFD. The PFD displays information traditionally displayed on the flight instruments, along with some other information such as navigation and frequencies. The MFD displays other supporting information, such as moving maps, nearby detected traffic, engine and systems data, weather, and terrain. The MFD can also be used as a PFD in the event there is a display failure.
An aircraft using electronic flight display will also likely be equipped with a few analog instruments as an emergency backup. These analog instruments are the airspeed indicator, attitude indicator, and altimeter, which are essential for maintaining aircraft control by reference to instruments.
The PFD will show the same information to the pilot as traditional instruments. The presentation is more intuitive and readily translated into a mental picture. The PFD is also easier to scan than a set of traditional flight instruments. The display shows an airspeed tape on the left, airplane attitude information in the center, and an altitude tape on the right.
Just to the right of the altitude tape is the vertical speed indication. Since the vertical speed is generated by an air data computer, it is instantaneous. Traditional vertical speed indicators have some lag time as the pressure difference sets up between case pressure and static pressure. With an EFD, this lag is gone.
The HSI is located bottom center. In addition to acting similar to a tradition HSI, it will also display rate of turn via a trend vector. Marks to the left and right of the current heading depict half and full standard rate. In a turn, a trend vector will extend to indicate the rate of turn.
In addition to the heading trend, trend vectors are also displayed for airspeed and altitude. These trend vectors extend when the associated data is changing and usually show what the associated instrument indication will be 6 to 10 seconds in the future. The specific values and colors used vary between manufacturers.
Turn coordination is indicated by the slip/skid indicator, located just below the roll pointer of the attitude indicator. When coordinated, the slip/skid indicator sits right under the roll pointer. If it slides left or right it informs the pilot that left or right rudder is required for coordinated flight. It is used the same way as a traditional inclinometer.
An instrument student is still susceptible to developing the same scan errors when learning on an EFD equipped airplane. Care should be taken to use all the information presented on the display without emphasizing certain data over other.
Attitude instrument flying can be accomplished using the same primary-secondary technique discussed for use with traditional instruments. The arrangement of information on a PFD might lend itself to another method of instrument flying known as the control and performance method. Which of the two methods used is a matter of preference between the student and instructor. The control and performance method can also be used with traditional instrumentation, as well.
The control and performance method consists of four steps used any time a change in attitude is required. First, the pilot changes the pitch, bank, and power as necessary to establish the airplane in the desired maneuver. Next, the pilot trims the airplane. A retrim is required anytime you change airspeed. Some pilots also prefer to retrim during long turning maneuvers, such as steep turns. The pilot then cross checks the displayed information before lastly, making any necessary adjustments. Adjustments should be made in small increments.
Should an instrument failure occur, EFD systems are designed to remove erroneous data from the display and cover the instrument with a large red x on the display.