TruTrak EFIS (8300-056) - Manual (Page 4)

TruTrak Flight Systems 2 EFIS Installation Manual
February 2009 8300-056 Rev B
THE DISPLAY
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 is a special case of a presentation used in the military called VELOCITY VECTOR.
This display has two advantages. The first is 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 this concept is that it makes holding altitude easier (not only in straight
flight but also in turns). It is a fact that next to AOA, airspeed provides the best warning of approaching a stall. For
this reason the airspeed pointer flashes red when a pre-set minimum airspeed safely above a stall is reached.
There are critics of this concept who believe that attitude is an indicator of approaching a stall. NOT SO, attitude
alone is not at all such an indicator.
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
same 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.
When a DIRECT TO or
FLIGHT PLAN is set
into the GPS this
display becomes an
HSI. The boldness of
this high quality display
in combination with its
location enhances the
flyability of the overall
instrument. Finally, the
HSI contains features that make functions available that are not found in other low cost systems. These are
described in other sections.
The analog presentations of airspeed and altitude are based on the belief that in some cases 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 white needle
moving around a black altimeter dial. 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. The difference is that in this system the dials rotate about
fixed pointers, but the relative motion retains the same effect as the moving pointer. In addition, the rotating
altimeter dial further enhances the motion factor. To satisfy personal preference the display can be switched back
and forth between round and rectangular, even in flight. Of those who have tried both the choices have been
almost unanimous in favor of the round.
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.