Precision Approach Path Indicator (PAPI / APAPI) (Signalight-made)

Signalight's Precision Approach Path Indicator range covers both the four-unit PAPI system used on conventional runways and the two-unit APAPI configuration suited to heliports, constrained sites, and smaller aerodromes. Both variants serve the same function: presenting a red/white colour split to approaching pilots that encodes whether the aircraft is above, on, or below the correct approach slope. The design philosophy emphasises minimum maintenance burden — each unit carries an integrated electronic clinometer that self-monitors the installation angle, automatically switching off and triggering a relay-output fault signal if the tilt deviates by more than half a degree from the factory-set calibration. This self-checking behaviour protects against the silent drift failures that have historically undermined PAPI reliability in sandy or thermally active environments, relevant to GCC airport operations. Units are machined from aluminium alloy with a powder-coated finish (RAL 1004 aviation yellow), a hardened glass diffuser for sand-blast protection, and an anti-glare visor in RAL 9005 black to suppress stray light toward the airfield. Optical output uses OSRAM red and white LEDs with custom-designed optics to match ICAO Figure A2-23 isocandela diagrams. The PAPI accepts CCR input at 2.8–6.6 A while the AC-powered APAPI connects directly to 110/230 V mains; both units draw up to 50 W per lamp head at maximum intensity. The system is certified against ICAO Annex 14 Volume 1 (7th Edition, 2016) including photometric and chromaticity requirements. Optional solar powering is available for off-grid or contingency deployments.