What is the HMI?
The human-machine interface is the screen where an operator sees airfield lighting status, sends commands and acknowledges alarms.
The HMI is the part of the ALCMS that people actually use. It normally shows a graphical layout of the airfield with each lighting circuit marked by a status colour or symbol, and it lets the operator select a circuit, choose on, off or a brightness step, and confirm before the command is sent. An alarm list shows faults, which the operator acknowledges. HMIs are found at the tower, at a maintenance station and sometimes on a local panel at the CCR or substation.
The HMI does not switch the lights itself. It sends the command to the ALCMS, which passes it on to the field controllers and CCRs, and it displays the status that comes back. Login and access levels limit what each user can do, and confirmation prevents accidental changes to lighting that pilots rely on. Screen layout, colours and names depend on the manufacturer and the project, and if a link fails the screen can be out of date, so the real status is checked at the CCR or in the field.
Frequently Asked Questions
Q1What does HMI stand for and what does it do?
HMI means human-machine interface. In an ALCMS it is the screen or panel where an operator sees the status of the airfield lighting circuits, sends commands such as on, off or a brightness step, and acknowledges alarms.
Q2Who uses the HMI?
Air traffic controllers use the tower HMI for operational lighting commands. Maintenance staff use their own station for status, alarms and diagnostics. What each person can see and do depends on their access level.
Q3Why does the HMI ask for confirmation before a command?
The lights are relied on by pilots, so an accidental touch or wrong selection must not change them. Selecting the circuit, choosing the setting and then confirming makes the operator check what is about to happen.
Q4Does the HMI control the CCRs directly?
No. The HMI sends the command to the ALCMS, which passes it through the network and the field controllers to the CCRs. The status comes back along the same path and is shown on the screen.
Q5What do the colours and symbols on the screen mean?
They normally show states such as on, off, dimmed and fault, but the scheme is set by the manufacturer and the project. The screen's own legend and the project documents are the reference, and a colour should never be assumed.
Q6What if the HMI shows something different from what is in the field?
Treat it as a possible fault or loss of communication. Check the actual status at the CCR or in the field, tell ATC as the procedure requires and follow the failure flow, because a failed link can leave a screen out of date.
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