locked. When the landing gear moves the contact
of three back-mounted indicators. A series of limit
of S2 to the down position, the indicator shows
switches in the landing gear control circuit control
the landing wheel. This says the wheel is down
these indicators. The wheel instrument (fig. 6-72,
and locked. Each switch connects to a solenoid
view A) gives a ready indication of the landing
in the indicator. As the solenoids energize, the
gear position. There are three positions on a drum
indicator element moves to reveal the position of
that move about an axis. One position of the drum
the aircraft landing gear. When the landing gear
has a landing gear wheel symbol. The center
is moving, both the up lock and down lock
position has a diagonal barber pole (black and
switches release. This opens both circuits to the
yellow warning lines). The other position has the
corresponding indicator, causing the black and
word UP. The miniature wheel shows that the
yellow barber pole to show. It also causes the
wheel is down and locked. The UP indicator
warning light in the landing gear handle to
shows the wheel is up and locked. The barber pole
illuminate. Figure 6-72, view B, shows a schematic
shows the wheel is somewhere between up and
for a complete aircraft landing gear position
down, or not locked in position.
indicating system.
The position indicator operates through the
landing gear limit switches in the wheel wells of
Flaps
the aircraft. When the landing gear moves the
You can show the aircraft flap position in a
contact of S1 (fig. 6-72, view A) to the up
manner similar to the landing gear. These
position, the indicator shows the wheel is up and
Figure 6-71.-Three-wire dc synchro system.