MALS

MALS (Medium Intensity Approach Lighting System) is a non‑precision approach lighting system that provides enhanced visual guidance for pilots during final approach. It typically consists of seven five-light bars spaced at 61m (200 ft) intervals extending 427 metres (1,400 ft) from the runway threshold, with a single crossbar (two wing bars) at the 305m (1,000 ft) point. MALS offers greater intensity and improved visibility compared to basic SALS, making it suitable for airports with higher traffic volumes or more demanding weather conditions. Unlike precision systems (ALSF‑1/2), MALS does not include sequenced flashing lights, but it provides a robust visual centreline and distance reference for night and marginal VFR operations.

MALS exists to give airports with meaningful traffic volume or more demanding weather a stronger visual approach reference than a basic single row of lights can provide, without introducing the sequenced flashing components that come with additional cost and complexity. Its optional crossbars at intermediate points add a depth and lateral reference along the row, letting a pilot judge distance and alignment more precisely than a plain unbroken line would allow, while stopping short of the dynamic directional cues that RAIL or SFL provide in the MALSR/MALSF variants. Its purpose sits deliberately between the most basic SALS-class systems and the flashing-augmented MALSR/MALSF configurations, offering airports a middle-tier upgrade path matched to their actual traffic and visibility demands.

MALS systems are installed at airports that support non‑precision approaches but require enhanced visual guidance. They are typically used on:

• Non‑precision runways with higher traffic volumes or more demanding weather conditions
• Regional airports serving commercial turboprop and regional jet operations
• Military airfields where basic approach lighting is insufficient
• Runways with moderate approach speeds where longer lead‑in is beneficial
• Airfields transitioning from basic to enhanced lighting without the cost of precision systems
• Locations where terrain or obstacles require improved visual reference

Fixtures are set out on lightweight frangible stands along the extended runway centreline at the standard 61 m (200 ft) spacing, running from the threshold out to 427 m (1,400 ft). A single crossbar stand pair is placed laterally at the 305 m (1,000 ft) point. Because MALS carries no sequenced flashing lights, the array is typically fed from a single steady-burning series circuit, with cable run in duct from each stand back to the regulator vault. Stands are sized for the lower loads of a medium-intensity system, and elevated piers are used only where the extended centreline crosses a road, ditch, or other minor obstacle. Setting-out is tied to the runway centreline extended and threshold survey.

The MALS system provides enhanced visual guidance through a combination of features:

• Single Row of Lights: Seven five-light bars, steady‑burning white, spaced at 61m (200 ft) intervals, extend from the runway threshold out to 427 metres (1,400 ft), providing a visual centreline reference.
• Crossbar Lights (Optional): A single crossbar (two five-light wing bars, one either side of the centreline bar) is located 305m (1,000 ft) from the threshold to provide distance reference and improve depth perception.
• Medium Intensity: Higher intensity than basic SALS, with better visibility in marginal weather and brighter ambient light conditions.
• 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 and optional crossbars 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 5‑step), allowing the ATC to adjust brightness for visibility conditions.
• Simplicity: The system has no flashing lights or complex sequencing, making it simpler and more reliable than precision systems.

MALS runs on a single series circuit loop, with no sequencer or flasher stage to coordinate — the centreline row and, where fitted, the crossbar lights are all wired into the same loop and therefore switch and dim together as one system. 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 MALS loop to the corresponding fixed current. Every fixture on the loop, centreline or crossbar, draws from the same current via its own isolating transformer and therefore burns at the same intensity simultaneously — there is no independent control of the crossbars or of any individual light along the row. Because MALS has no flashing stage, its control logic is the simplest of the approach lighting family: one command, one loop, one intensity for the whole array. 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.

MALS carries seven steady-white light bars locked to a flat 61m (200 ft) spacing over the full 427m (1,400 ft) FAA length, rather than a single continuous row. The real functional addition is the single crossbar at 305m (1,000 ft) — two five-light wing bars either side of the centreline bar that give the pilot a depth-perception reference the row alone can't provide.

Each light stand is a frangible aluminium or composite pole bolted to a shallow concrete footing or ground screw anchor, sized to break away cleanly if struck while still holding the fixture head steady in wind. The fixture head is a die-cast aluminium housing containing an LED array or 100–200W halogen lamp behind a toughened lens, gasket-sealed to achieve an IP67/IP68 rating, mounted so the beam projects uni-directionally toward the approach. Where the optional crossbar is fitted, three to five fixture heads are ganged on a rigid horizontal bar carried on its own pair of frangible stands, wired as a branch off the same series circuit as the centreline row. Internal wiring runs to L-823 primary connectors sealed for direct burial, terminating at the isolating transformer housed at the base of each stand or in a nearby ground box, with cable run in duct back to the regulator vault. Stainless-steel fasteners and corrosion-resistant coatings are used throughout to withstand prolonged outdoor exposure over unprepared or unpaved approach terrain.