equipment, and personnel equipped with radio if radio contact cannot be established. ATC personnel use a directive traffic control signal which emits an intense narrow light beam of a selected color (either red, white, or green) when controlling traffic by light signals. b. Although the traffic signal light offers the advantage that some control may be exercised over nonradio equipped aircraft, pilots should be cognizant of the disadvantages which are: 1. Pilots may not be looking at the control tower at the time a signal is directed toward their aircraft. 2. The directions transmitted by a light signal are very limited since only approval or disapproval of a pilot"s anticipated actions may be transmitted. No supplement or explanatory information may be transmitted except by the use of the "General Warning Signal" which advises the pilot to be on the alert. c. Between sunset and sunrise, a pilot wishing to attract the attention of the control tower should turn on a landing light and taxi the aircraft into a position, clear of the active runway, so that light is visible to the tower. The landing light should remain on until appropriate signals are received from the tower. d. Airport Traffic Control Tower Light Gun Signals. (See TBL 4-3-1.) e. During daylight hours, acknowledge tower transmissions or light signals by moving the ailerons or rudder. At night, acknowledge by blinking the landing or navigation lights. If radio malfunction occurs after departing the parking area, watch the tower for light signals or monitor tower frequency. TBL 4-3-1 Airport Traffic Control Tower Light Gun Signals Meaning Color and Type of Signal Movement of Vehicles, Equipment and Personnel Aircraft on the Ground Aircraft in Flight Steady green Flashing green Cleared to cross, proceed or go Not applicable Cleared for takeoff Cleared for taxi Cleared to land Return for landing (to be followed by steady green at the proper time) Steady red STOP STOP Give way to other aircraft and continue circling Flashing red Flashing white Alternating red and green Clear the taxiway/runway Taxi clear of the runway in use Airport unsafe, do not land Return to starting point on airport Return to starting point on airport Not applicable Exercise extreme caution Exercise extreme caution Exercise extreme caution 4-3-14. Communications a. Pilots of departing aircraft should communicate with the control tower on the appropriate ground control/clearance delivery frequency prior to starting engines to receive engine start time, taxi and/or clearance information. Unless otherwise advised by the tower, remain on that frequency during taxiing and runup, then change to local control frequency when ready to request takeoff clearance. NOTE- Pilots are encouraged to monitor the local tower frequency as soon as practical consistent with other ATC requirements. REFERENCE- AIM, Para 4-1-13, Automatic Terminal Information Service (ATIS). b. The tower controller will consider that pilots of turbine-powered aircraft are ready for takeoff when they reach the runway or warm-up block unless advised otherwise. c. The majority of ground control frequencies are in the 121.6-121.9 MHz bandwidth. Ground control frequencies are provided to eliminate frequency congestion on the tower (local control) frequency and are limited to communications between the tower and aircraft on the ground and between the tower and utility vehicles on the airport, provide a clear VHF channel for arriving and departing aircraft. They are used for issuance of taxi 4-3-20 Airport Operations