EFIS Information

Consider first the pitch display. Motion of the pitch display short term is gyroscopic as it must be to fly in IMC. Long term it is VSI. This display has two distinct advantages, the first being that it provides an instantaneous vertical speed presentation. The second is that when the reference airplane is on the horizon the aircraft is neither climbing nor descending. This eliminates the need for adjusting the position of the pitch reference airplane to compensate for the angle the fuselage is flying. The resulting benefit of the concept is that it makes holding altitude easier.

The HSI is placed below the horizon as in the larger more expensive displays. It is in the form of an ellipse for two reasons. First, an ellipse when compared with a circle of the height provides a broader scale at the top where it is read. Second, it looks as a circle would when laid out on the ground ahead of the aircraft. The boldness of the high quality display in combination with its location enhances the flyability of the overall instrument.

The analog presentations of airspeed and altitude are based on the belief that round is better. It will be noted that after having tried other presentations the automobile industry is back to round instruments. Nothing in the modern world of vertical tapes compares with the dynamic effect of a round altimeter dial rotating about a fixed pointer. As a target altitude is approached it is natural for the pilot to slow the needle velocity so as to arrive at the altitude without overshoot.

Within the bank angle scale, indicators are inserted, which show the angle for a standard rate turn. These indicators move outward on the bank angle scale as airspeed increases. Placed above the bank angle scale is an inclinometer that looks just like a conventional ball in a curved tube.

Still another convenient feature is the optional presentation of important engine data, in the pilot’s direct field of vision, displayed across the top of the instrument.

A flight director is standard even in the basic flight instrument. Like our autopilots, when the power setting is not sufficient to comply with altitude or vertical speed commands, the flight director transitions to an airspeed mode in which airspeed is held at or above a minimum value pre-set to the specific aircraft. The result is the highest level of safety.

The automatic arrival transition is also included in every EFIS. This is a feature that will help even the experienced pilot when approaching an unfamiliar airport. To initiate the arrival transition click CRS – set the HSI course pointer to the selected runway direction – press APPR – using the flight director or autopilot, fly the arrival path to the selected runway. This will work from any direction. See graphic on opposite page.