emergency because they are almost always
electrically powered, while the attitude and
directional gyros are often powered by a not-too-reliable vacuum pump.
Because of its decades-long status as the
savior for pilots who lose the vacuum pump
while flying in the clouds, the turn indicator
has special status for many. But when you
really think about what the instrument is
telling you, the information is very basic—
the airplane is changing heading and in
which direction, and the airplane is, or is
not, in coordinated flight.
Most PFDs simply put a colored line on
the compass rose showing that the airplane
is changing heading and in which direction.
Another mark shows what heading change
equals the standard rate turn.
To show slip or skid many PFDs use a
small box under the roll index pointer at the
top of the bank angle scale. This little box
moves left or right to show a slip/skid. Some
other PFDs put an actual “ball in a race” type
of slip-skid on the display that looks very
much like an electronic version of the actual
ball in the fluid. Either way, the information
presentation is pretty basic and simply
doesn’t take time to learn to understand.
FLYING THE FIRST PFD
I had the unique opportunity to be a guinea
pig with the first PFD certified in a civilian
airplane. It was a little more than 25 years
ago, and Gulfstream and Honeywell had cre-
ated the first PFD with its vertical tapes for
altitude and airspeed. There was no simula-
tor operating when I got to fly the prototype,
so my first takeoff would be on the glass and
for real. And as luck would have it the
weather was about 300 feet overcast. My
transition time to a PFD for real would be a
couple of seconds between rotation and
punching into the clouds.
