SSALS

SSALS (Simplified Short Approach Lighting System) is a basic approach lighting system for non‑precision runways. It consists of a single row of steady‑burning white lights extending from the runway threshold into the approach area, for a distance of 427 metres (1,400 ft) under the FAA standard — effectively a truncated, high-intensity ALSF‑2 configuration with no crossbar or flashers. SSALS is a shorter, medium/high-intensity configuration designed for airfields with lower approach speeds and less demanding operational requirements than a full precision system. It provides pilots with a visual centreline reference during final approach, enhancing safety during night operations and marginal weather conditions without the complexity and cost of full precision approach lighting systems.

SSALS exists to bring a basic centreline visual reference to smaller airfields where the traffic volume, approach speeds, and operational demands don't justify the length, or the cost, of a full-length approach lighting system. Its shortened configuration reflects a deliberate scaling decision: since lower approach speeds and simpler traffic patterns at these fields mean pilots need less lead distance to establish and confirm alignment, a shorter system still achieves the core purpose — giving a clear centreline reference during night and marginal-weather approaches — without the installation and maintenance burden of the full-length system. Its purpose is therefore about matching lighting infrastructure to the actual operational profile of smaller airfields rather than under-serving them with no system at all.

SSALS systems are installed at airports that support non‑precision approaches. They are typically used on:

• Non‑precision runways with VOR, NDB, or GPS approaches
• Regional and general aviation airports with lower traffic volumes and smaller aircraft
• Smaller airfields with budget constraints for AGL infrastructure
• Military airfields with basic approach requirements
• Runways with visual approaches that benefit from enhanced night guidance
• Airports where a shorter approach lighting system is sufficient due to terrain or approach speed considerations

Fixtures are mounted on lightweight frangible stands set out along the extended runway centreline at 30 m (100 ft) spacing, running from the threshold out to 427 m (1,400 ft). With no flashing circuit or crossbar structures to coordinate, the array is wired as a single steady-burning series circuit, with cable run in duct from each stand back to the regulator. Its shorter 427 m length keeps the number of stands and the total cable run smaller than a full ALSF-2 installation, which suits smaller airfields with tighter budgets. Elevated piers are needed only where the extended centreline crosses a road, ditch, or similar minor obstacle. Setting-out is tied to the runway centreline extended and threshold survey.

The SSALS system operates on a simple principle: a row of lights provides a visual centreline reference for the pilot:

• Single Row of Lights: A row of steady‑burning white lights at 30m (100 ft) spacing extends from the runway threshold out into the approach area for 427 metres (1,400 ft), providing a visual centreline reference.
• Shorter Length: At 427 metres (1,400 ft), SSALS is a truncated version of the ALSF‑2 pattern, making it suitable for smaller airfields and lower approach speeds.
• Lateral Guidance: The row of lights helps the pilot align the aircraft with the runway centreline during the final approach segment.
• Distance Reference: The spacing of the lights provides a rough distance reference, helping the pilot judge the approach path.
• Intensity Control: The lights are typically controlled by a CCR with intensity steps (usually 3‑step or 5‑step), allowing the ATC to adjust brightness for visibility conditions.
• Simplicity: The system has no flashing lights, crossbars, or complex sequencing, making it simple to install, operate, and maintain.

SSALS runs on a single series circuit loop with no crossbar branch and no sequencer stage — every fixture along the shorter 427 m row is wired into the same loop and switches and dims together as one system, exactly as with the full-length ALSF-2 it truncates, just over a shorter run. An Airfield Lighting Control and Monitoring System (ALCMS), operated by the tower or an automated visibility-linked routine, selects the required brightness step; this command is passed to the CCR, which regulates the entire row to the corresponding fixed current. Every fixture, via its own isolating transformer, draws from the same current and therefore burns at the same intensity simultaneously — there is no way to command an individual light, or a section of the row, independently of the rest. Because the array is shorter than the full ALSF-2, the loop carries fewer fixtures and a lower total load, which is one of the reasons SSALS suits smaller airfields, but the control principle is identical. Fault detection follows the same loop-based principle used across the AGL series circuit family: the CCR continuously monitors loop voltage against the commanded current, and a voltage rise at constant current signals increased circuit impedance, typically an open-circuit lamp or a failed isolating transformer, reported to the ALCMS as a loop fault rather than pinpointed to an exact fixture without further sectionalised testing.

Each fixture follows the same die-cast aluminium construction as a standard SALS unit: an LED array or 45–100W halogen lamp behind a toughened, gasket-sealed lens rated IP67/IP68, mounted on a frangible aluminium or composite stand bolted to a shallow footing or ground screw anchor. With no flasher stage or crossbar structures, all stands are wired into a single steady-burning series circuit through L-823 connectors and individual isolating transformers, with cable run in duct back to the regulator. Because the SSALS configuration is shorter than a full SALS array, the total number of stands, transformers, and cable runs is correspondingly smaller, reducing both material cost and installation time — a deliberate design trade that suits smaller airfields with tighter budgets. Stainless-steel fasteners and corrosion-resistant finishes are used throughout for continuous outdoor exposure.