What is a smart PAPI?
A precision approach path indicator that keeps its red and white glide-path signal — and adds monitoring that reports the health of each unit and warns if its aiming angle drifts.
A smart PAPI is a precision approach path indicator paired with monitoring, built into the units or fitted beside them. The PAPI still shows the red and white glide-path signal exactly as before, while sensors check each unit and report its state, with its identity.
Between inspections, a failed lamp or a unit knocked out of aim can go unnoticed; with monitoring, the exact unit is shown on the control system, and some designs warn when the aiming angle drifts. But the signal pilots see is still set and verified to the PAPI requirements, and a sensor reading is a warning, not proof. The reporting path needs cyber-security, and an engineer confirms an alert before acting. It supports the maintenance programme and does not replace it.
- Signal. The units show the red and white split that gives the glide path, set and verified as required.
- Monitor. Sensors check lamp or LED state, intensity step and, on some designs, the aiming angle of each unit.
- Report. Status travels over the circuit or a separate link, through a gateway.
- Show. The ALCMS lists each unit and raises an alarm for a failed unit or a drifting angle.
- Check. The engineer inspects the unit and confirms or re-sets the aiming by the approved method.
- Confirm. After the fix, the status shows the unit is healthy again.
Shows the standard glide-path signal, and sensors also report each unit’s state and warn if its angle drifts.
Shows the signal with no reporting. A failed lamp or a shifted unit is found by inspection, measurement or a pilot report.
PAPI Signal
The PAPI signal is the red and white split that gives the pilot the glide path. A smart PAPI keeps this signal exactly as before, and the signal is still set and verified to the PAPI requirements. The added monitoring only reports the state of each unit and, on some designs, warns when its aiming angle drifts. A sensor reading is a warning, not proof, so an engineer confirms an alert before acting.
Frequently Asked Questions
Q1What is a smart PAPI in airfield ground lighting?
A precision approach path indicator that keeps its normal red and white signal and adds monitoring. The system reports the state of each unit, its intensity setting and, on some designs, its aiming angle, so the control system can see the health of the whole PAPI.
Q2Does a smart PAPI give pilots a different signal?
No. Pilots still read the same red and white split that shows the glide path. The smart part sits behind the units: sensing, reporting and control. The signal, its angles and its sector transition are still set and verified to the applicable requirements.
Q3What does a smart PAPI report?
Typically whether each unit is lit and working, and sometimes lamp or LED condition, intensity step, temperature, an alarm state, or a tilt or elevation reading, with the unit’s identity. What is reported depends on the system and supplier.
Q4Can a sensor tell that a PAPI is misaligned?
It can warn that a unit’s angle has drifted from its set value, for example after an impact or settlement. It cannot prove the signal is correct. Aiming is still confirmed by measurement and, where required, by flight inspection.
Q5How does the information reach the ALCMS?
Depending on the system, over the series circuit itself or over a separate communication link, through a gateway to the control system. The method and protocol vary by supplier and must suit the existing circuit and the site’s cyber-security rules.
Q6Does it replace PAPI inspection, testing and flight checks?
No. Visual checks, cleaning, electrical tests, aiming checks and flight inspection still follow ICAO Annex 14, the national regulator and the aerodrome’s approved procedures. Monitoring helps find faults sooner and focus the visit, and an engineer confirms an alert before acting.
See It. Understand It. Then Learn How to Engineer It.
Recognising an AGL system visually is the first step. The next step is knowing how to design, install, test, commission and maintain them correctly.
Build Practical AGL Engineering Skills
Go deeper with structured training from Precision AGL Academy, covering:
Learn how each light, sign and circuit works as part of a complete airport lighting system, not just as an isolated diagram.