What is tower control?
Tower control is air traffic control operating the airfield lighting from the tower HMI, choosing which lights are on and how bright, through the ALCMS.
At a controlled aerodrome, tower control is the normal way airfield lighting is operated. Air traffic control uses the tower HMI to select lighting groups such as runway, approach, taxiway and stop bars, set them on or off, and choose a brightness step to suit visibility, traffic and time of day. Controllers decide what pilots need to see, and the system carries out the decision.
The tower does not switch the lights itself. The command goes to the ALCMS, which checks access levels and interlocks and passes it through the network and field controllers to each CCR. Status and alarms return to the tower screen. Tower control works only while the CCRs are in Remote and the link is healthy. A CCR in Local ignores the tower, and a failed link can leave the screen out of date, so the tower must be told and the airport’s failure procedures followed. Functions, step names and rules differ by project and airport.
Frequently Asked Questions
Q1What is tower control in airfield lighting?
Tower control means air traffic control operates the airfield lighting from the control tower, normally through an HMI connected to the ALCMS. Controllers choose which lights are on and at what brightness to suit the traffic and conditions.
Q2Why does the tower control the lights?
Air traffic control knows which runway and taxiways are in use, and what the pilots need to see. Putting the operational decision in the tower means the lighting follows the traffic, while maintenance staff look after the equipment.
Q3What does the tower normally set?
Typically on or off for each lighting group and a brightness step chosen for visibility and time of day. Stop bars and taxiway routes are normally selected by controllers to match clearances. The exact functions available depend on the project and airport procedure.
Q4Does the tower control the CCRs directly?
No. The command goes from the tower HMI to the ALCMS, through the network and field controllers, to the CCR. The status comes back the same way. The CCR must be set to Remote to accept it.
Q5What happens if a CCR is in local or the system fails?
If a CCR is in local, tower commands for that circuit are ignored. If the link or ALCMS fails, the screen may be out of date and commands may not arrive. The tower should be told, and the airport's failure procedures apply.
Q6How does the tower know when a light circuit has a fault?
Alarms and status colours from the CCRs and monitoring reach the tower screen. ICAO Annex 14 requires lighting systems used for aircraft control purposes to be monitored automatically, with any fault that could affect the control function relayed to the air traffic services unit (check the current edition). Which other faults the tower sees, and what controllers must do about them, are set by the project design and the airport's own procedures.
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