Prism Cleaning Kit

A Prism Cleaning Kit is a purpose-assembled set of cleaning materials and tools used to maintain the optical clarity of AGL fixture prisms, lenses, and optical windows. The kit typically includes:

• Optical-grade cleaning solution (non-abrasive, streak-free, compatible with glass and acrylic)
• Lint-free microfiber cloths for gentle wiping without scratching
• Foam-tipped swabs for reaching recessed optical surfaces
• Soft-bristled brushes for removing loose debris before liquid cleaning
• Anti-static wipes to reduce dust attraction after cleaning
• Storage case to keep all items clean and organized

Proper cleaning of prisms is critical for maintaining the photometric performance of AGL fixtures, ensuring that light beams meet ICAO and FAA intensity and color specifications.

The prism cleaning kit exists to protect the photometric integrity of the fixture over its service life. Dust, oil film, rubber deposits from tyre contact, and de-icing chemical residue all scatter or absorb light at the optical surface, silently reducing the intensity a pilot actually sees even when the lamp or LED array itself is performing to specification — a fixture can fail a photometric inspection purely due to a dirty lens. Because the kit is purpose-matched to the optic (non-abrasive solution, lint-free and foam-tipped applicators), it removes contamination without introducing the scratches or haze that a generic cleaner or cloth would cause, which would otherwise create permanent, uncorrectable light loss. In this way, routine use of the kit is what keeps the beam pattern and colour a fixture was designed to produce actually reaching the pilot's eye in service, not just at the point of manufacture.

Prism cleaning kits are used during routine and corrective maintenance on all AGL fixtures with optical components:

• Runway Lights: Edge, centreline, threshold, end, and touchdown zone lights
• Taxiway Lights: Edge, centreline, and stop bar lights
• Approach Lighting: Barrette lights, crossbar lights, and sequenced flashing lights
• Visual Approach Slope Indicators: PAPI, VASI, and APAPI units
• Obstruction Lights: Beacons and obstruction markers with optical windows
• Sign Boards: Internally illuminated sign faces

Cleaning is performed as part of scheduled preventive maintenance (e.g., quarterly or bi-annually) and also after events that cause heavy contamination, such as rubber deposit buildup from aircraft landings or de-icing operations.

The kit is kept in its own padded case in the maintenance vehicle or workshop tool store, with solutions, cloths, and brushes segregated to prevent cross-contamination between abrasive and non-abrasive materials. Cleaning solutions are stored within their manufacturer-stated shelf life and away from direct sunlight or freezing temperatures, which can affect their chemical stability, and microfibre cloths are laundered separately from other shop rags to avoid picking up grit that would scratch optical surfaces on the next use. Crews carry the kit out to the fixture location rather than the fixture being brought to the kit, and consumable items (cloths, solution) are restocked after each maintenance round so the kit is always ready for the next scheduled or corrective cleaning task.

The cleaning process involves several steps to safely remove contaminants without damaging the optical surfaces. The technician first uses a soft brush to remove loose dust and debris. Then, a small amount of optical-grade cleaning solution is applied to a lint-free cloth or swab. The cloth is gently wiped across the prism or lens surface in a single direction, avoiding circular motions that can trap particles and cause scratches. For recessed or delicate optics, foam-tipped swabs are used to reach tight areas. After cleaning, a dry lint-free cloth is used to buff the surface to a streak-free finish. The entire process is designed to restore the original light transmission and beam pattern, ensuring that the fixture meets its photometric specification.

The cleaning solution is specifically formulated to dissolve oils, rubber residues, and de-icing chemicals without attacking the optical coating or the substrate (glass or acrylic). Anti-static wipes are then used to reduce the attraction of new dust particles.

The cleaning kit has no control system of its own — it is a manual maintenance tool, and any "logic" involved is procedural rather than electronic: a fixed sequence of steps (debris removal, solvent application, one-directional wiping, dry buffing) is followed in a specific order because reversing or skipping a step risks trapping grit against the optic and scratching it. Its place in the wider architecture is as an input to the maintenance and quality-assurance workflow rather than to the electrical control system: cleaning is typically triggered by a scheduled maintenance interval or by a photometric test bench flagging reduced output, and the result is verified afterwards by re-measuring the fixture's intensity on a photometer or goniophotometer rather than by any feedback from the kit itself.

The kit is carried in a rigid, moulded polypropylene or aluminium case with a foam cut-out insert that holds each item in a fixed slot, so contents can be checked at a glance and nothing rattles loose in a service vehicle. The cleaning solution ships in a sealed, light-resistant bottle with a fine-mist or dropper applicator to control the amount applied to a lens without over-wetting the fixture's seals. Microfiber cloths are packed in a resealable, lint-trapping sleeve to keep them free of grit between uses, since a single trapped particle can scratch a prism during wiping. Foam swabs, soft-bristle brushes, and anti-static wipes are individually wrapped, and the case includes a small compartment for a torch or inspection mirror used to check the cleaned surface for residual film or lint before the fixture is closed back up.