Adjustment of Baffles on LED PAPI (LHA)

Purpose The integral baffles on the LED PAPI narrow the beam signal to prevent interference from obstructions. Adjustment screws are located on each side of the Light Housing Assembly (LHA). Important: Because the lensing system inverts the signal image, adjusting a screw on one side affects the beam cutoff as viewed from the opposite side.

Step-by-Step Instructions

1. Prepare the LHA
   • Remove the top cover of the LHA.
   • Set dip switches to Test Mode 1:
     • SW1-6: ON 
     • SW1-8: ON
     • SW2-8: OFF (This ignores tilt or communication failures during adjustment.)
2. Loosen Mounting Hardware
   • Loosen the top flange nuts on each mounting leg (front and rear) to allow tilt adjustment.
3. Temporarily Raise the Rear for Observation
   • Raise the rear of the LHA (using the rear leg adjustment) until the display indicates a glide slope of approximately 0.00°. This positions the beam for clear observation of the cutoff point downfield.
4. Position Observer
   • Station a qualified observer downfield along the desired cutoff angle (where the beam should be narrowed/blocked due to obstruction).
   • Ensure clear two-way communication (radio/hand signals) with the observer.
5. Adjust Baffles
   • Identify the side(s) requiring baffling (based on obstruction location).
   • Remove the screw(s) from the side(s) opposite the desired baffling area (due to image inversion).
   • Thread the jam nut all the way down the baffle adjustment screw (to allow full adjustment range).
   • Install and gradually turn the baffle adjustment screw until the downfield observer confirms the correct level of baffling (beam narrowed appropriately without excessive cutoff).
6. Secure the Adjustment
   • Tighten the jam nut firmly against the housing to lock the baffle adjustment screw in position.
7. Return to Desired Glide Slope
   • Lower the rear of the LHA until the display indicates the desired glide slope angle (e.g., 3.00° or as per site specs).
8. Secure Mounting
   • Tighten the three top flange nuts and any associated jam nuts on the mounting legs.
   • Make minor final adjustments if needed to maintain the exact glide slope reading.
9. Restore Normal Operation
   • Reset dip switches to Normal mode:
     • SW1 positions 6, 7, and 8: OFF
     • SW2: All OFF
     • SW1 positions 1–5: Return to normal field settings (per site configuration).
   • The system will resume full functionality, including tilt and communication monitoring.
10. Finalize
    • Replace and securely fasten the top cover.
    • Verify system status on the display.
    • Conduct a functional check (e.g., observe beam from approach end) and log the adjustment.

Additional Notes

• Always adjust baffles conservatively—over-baffling can reduce signal visibility for pilots.
• If multiple LHAs are present, repeat for each unit and ensure uniformity.
• Document before/after observations, observer feedback, and final display readings.
• If issues persist (e.g., unstable readings), recheck power, connections, and dip switch settings.

 

Airport Lighting Company | L-880(L), L-881(L) Precision Approach Path Indicator Lights (PAPI)