TruTrak ADI - Manual (Page 3)

ADI Operation
The artificial horizon, when needed is without a doubt, the most important instrument in the panel. For this reason, the
display must be easy to fly and the instrument very reliable. To achieve this, the ADI combines modern solid state
technology with an easy to see uncluttered mechanical display. In the basic instrument flight panel it is intended for
installation between an airspeed indicator and an altimeter. It is also well suited as the conventional backup in panels
incorporating one of the large glass displays.
The ADI is easy to fly partly because it contains in one instrument, roll, pitch, and direction. Beyond this, it is the
content of each of these displays that make this instrument easy to fly.
The direction display is located in the center of the instrument just below the rotating horizon mask. As is often the case
with an inexperienced pilot caught in IMC, the instrument may be viewed with tunnel vision. For this reason it is good
to have the direction in the center of the tunnel. Of more importance is that this display is track instead of magnetic
heading in that the modern way to navigate is to fly track. When track is presented as a gyro display, the numbers move
sequentially one degree at a time. Experience is showing that direction control with this digital DG placed immediately
below the horizon mask is as easy to fly as the conventional vertical card DG in combination with the conventional
horizon placed nearby.
The bank angle display is driven in a manner similar to that used in the pictorial turn
and bank. The only difference is that in this instrument the display shows bank angle
instead of turn rate. The advantage of this is that the presentation is instantaneous
data only. It cannot drift to accumulate error as is possible with the more complex
AHRS driven systems. It shows bank angles of up to +/- 45° while the requirement
on conventional gyro horizons is +/- 100°. To compensate for this, in the 3 1/8” size
only, flashing red arrows point in the direction the stick is to be moved to level the
aircraft when the bank exceeds +/- 30°. Note that when flying on instruments the
object is to stay level or at least in shallow banks. This instrument is therefore
designed to keep the pilot out of trouble.
The pitch display is perhaps the most beneficial feature of the ADI when compared with conventional horizon
indicators. For short term or immediate movement of the nose up or down, this instrument responds and is flown like
any other gyroscopic pitch indicator. The difference is that after the display has moved in response to an attitude change
the deflection is sustained by the resulting vertical speed. As compared to a pitch attitude display, the vertical speed
display makes it easier to hold altitude and to maintain stable climbs and descents. Also, the movable airplane symbol
does not have to be adjusted to compensate for the angle the fuselage flies when vertical speed is zero. It is recognized
that an aircraft when at the limit of its altitude capability can fly at an ever increasing angle of attack when vertical
speed indicates zero. For this reason an airspeed warning in the form of the letters “A-S” flashing in the DG display is
provided. The answer to this situation is then to observe the airspeed indicator. For stall prevention airspeed is the best
information short of an angle of attack indicator. (Better than attitude)
Another plus regarding this display is that when the airplane is going straight or not turning a wing level presentation is
shown. With this presentation one can disregard the effect of the rudder being out of trim (ball off center) just as
crosswind is not a factor when flying GPS track for direction. This is easier than trying to fly straight with the display
showing a wing down as is the case with a conventional horizon display when the rudder is out of trim. To sum it up, all
of the features described above, in combination, provide what we believe to be the easiest to fly artificial horizon.
TruTrak Flight System 1 ADI Flight Instrument Installation Manual
December 2009 8300-016 Rev B