switch that automatically opens the circuit when released. This feature enables you to
flash the selected color or to hold the toggle switch down when a steady color is
desired. The portable traffic light is normally installed in control towers from the
overhead by means of a cable that is on pulleys and counterbalanced by weights. This
feature keeps the light within reach for instant use and out of the way when not in use.
Capabilities and Limitations of the Control Light
You should be thoroughly familiar with the limitations of the traffic control light and
evaluate its capabilities when you anticipate its use. Table 5-4 shows the advantages
and disadvantages of the traffic control light.
Requires no radio equipment in the
The pilot may not be looking at the control
aircraft; therefore, all aircraft can be
tower at the time a signal is given.
controlled whether or not they possess a
Provides an emergency method of control
The information transmitted by a light
in event of radio failure either in the tower
signal is limited. You may transmit only an
or in the aircraft
approval or disapproval of the pilot s
anticipated actions since no explanatory or
supplementary information can be
Table 5-4 -- Traffic control light advantages and disadvantages
Use of Control Light
You should not hesitate to use light signals to control traffic, but you must be careful
when using the light gun (see Figure 5-12). You must transmit signals in a deliberate
manner so the pilot will know the exact nature of the message. For instance, if the pilot
was to start across the runway and you give a fast flashing green light, it might, on
occasion, appear as a steady green light. The pilot in that situation would think that you
were giving a takeoff clearance instead of a taxi clearance. The result would be a
conflict with other traffic on the crossing runway.