What is intensity control?
Choosing how bright the airfield lights are — a step for the conditions, a current from the CCR — and checking that the lights actually follow.
Intensity control is choosing how bright the airfield lights are. The controller reads the conditions, such as daylight, dusk, night or poor visibility, and selects a brightness step. The CCR then sets the circuit current for that step, and because the lights are driven by current in a series circuit, a higher step means a higher current and a brighter light. A typical five-step 6.6 A circuit runs from about 2.8 A on step 1 to 6.6 A on step 5; three-step circuits (typically 4.8, 5.5 and 6.6 A) are also used.
Two ideas keep it practical. First, light output does not rise in proportion to current: a modest change in current makes a larger change in brightness, so the steps are spaced to give useful, distinct jumps rather than equal ones. Second, brightness is matched across systems. Related lights such as runway edge, centreline and approach are normally moved together, so the pilot sees a balanced picture and no system dazzles or masks another. Because intensity is set by a control command, it is confirmed the same way: the reported step and output current should match the step requested (see Equipment Status).
- Assess. Read the visibility, ambient light and the operation in force.
- Select. Choose the brightness step for those conditions, per the airport’s procedure.
- Set. The CCR adjusts the circuit current to that step.
- Match. Related systems are moved together so the picture stays balanced.
- Confirm. Check the reported step and current, and watch for the lights not following.
Intensity Control Explorer
Pick a brightness step on a five-step circuit
At the CCR TYPICAL 6.6 A CIRCUIT
What it means ILLUSTRATIVE
Teaching simulation. Step use is illustrative; the step for each condition is set by the airport’s procedures, and output shown on the bar is relative and approximate for a halogen lamp, not a measurement. LED fittings are built to the same step brightness set by their specification.
Frequently Asked Questions
Q1What is intensity control?
Choosing how bright the airfield lights are. The controller selects a brightness step for the visibility and time of day, and the CCR sets the circuit current for that step, which sets the light output.
Q2How does a step change the brightness?
In a series circuit the lights are driven by current. Each step is a different current, and a higher current gives a brighter light. Light output does not rise in proportion to current, so the steps are chosen to give useful, distinct brightness changes.
Q3Who decides which step to use?
The control position in charge, normally the tower, selects the step according to the visibility, ambient light and the airport's procedures. Maintenance staff set steps locally only for testing and work.
Q4Why are different lighting systems set together?
So the pilot sees a balanced picture. If one system were much brighter than its neighbours it could dazzle or mask other lights, so related systems are usually moved together, following the airport's procedures.
Q5Do lower steps extend lamp life?
For halogen lamps, yes. Running at lower current reduces filament stress. LED fittings are much less sensitive to this, but the step still controls brightness, so it is chosen for visibility rather than for lamp life.
Q6How do I know the step has really changed?
Check the feedback. The reported step and output current should match the step requested. If they do not, the command has not been confirmed, or the circuit is not reaching the required output, and the cause should be checked before relying on it.
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