What are MALS, MALSF and MALSR?
The FAA’s medium-intensity approach lighting family — seven five-light bars every 200 ft, a 1,000-ft crossbar and green threshold lights, with sequenced flashers (MALSF) or runway alignment indicator lights out to 2,400 ft (MALSR) added at the outer end.
MALS, MALSF and MALSR are the medium-intensity approach lighting systems: an economy family that gives the pilot a white centreline path to the runway with fewer lamps and less length than the high-intensity ALSF systems. All three share one steady core — seven five-light white bars, the first 200 ft from the threshold and the rest every 200 ft out to 1,400 ft, a 1,000-ft crossbar about 66 ft long, and green threshold lights. There are no red bars or side rows.
MALS is that steady 1,400-ft pattern on its own, with no flashers. MALSF adds three sequenced flashers at the outer end, used where the approach area is hard to identify against background lights.
MALSR adds runway alignment indicator lights (RAIL): a line of sequenced flashers that runs out beyond the bars at 200-ft spacing and extends the system to 2,400 ft. The flash travels towards the threshold, so it leads the pilot in. MALSR is the FAA standard for Category I precision runways.
Frequently Asked Questions
Q1What are MALS, MALSF and MALSR?
They are the FAA medium-intensity approach lighting systems. MALS is the Medium-intensity Approach Lighting System, MALSF adds sequenced flashers, and MALSR adds runway alignment indicator lights (RAIL). All three share the same steady-burning core: seven five-light white bars on the extended centreline, a 1,000-ft crossbar and green threshold lights.
Q2How do MALS, MALSF and MALSR differ?
Only the outer end changes. MALS is the 1,400 ft steady pattern with no flashers. MALSF is the same pattern with three sequenced flashers at the outer end, used where the approach area is hard to identify. MALSR keeps the 1,400 ft pattern and adds RAIL, a line of sequenced flashers that extends the system to 2,400 ft.
Q3What do the letters F and R mean?
F means sequenced flashing lights are fitted. R means runway alignment indicator lights (RAIL) are fitted. The two are the same kind of lamp: when flashers sit among the centreline bars they are called sequenced flashers, and when they run out beyond the bars at 200-ft spacing they are called RAIL. The flash runs towards the threshold, so it acts as a rabbit that leads the pilot in.
Q4What is the core pattern of a medium-intensity system?
Seven five-light bars sit on the extended runway centreline, the first 200 ft from the threshold and the rest every 200 ft out to 1,400 ft. At 1,000 ft two more five-light bars sit either side of the centreline bar to form a crossbar about 66 ft long. Green threshold lights mark the runway end. There are no red bars and no side rows, which is a key visual difference from ALSF-1 and ALSF-2.
Q5How do they relate to SSALS and ALSF-2?
In layout the MALSF looks the same as the SSALF, and the MALSR looks much like the SSALR (also five RAIL flashers, but with wider-spaced lights and a 70-ft crossbar), which is the older system used when Category I conditions exist on a Category II runway with a dual-mode ALSF-2/SSALR installation. The medium-intensity systems are the economy family: fewer lamps, shorter length and no red bars compared with the high-intensity ALSF systems.
Q6Where are they used, and what minimums do they give?
MALS is the economy system for non-precision runways, and MALSR is the FAA standard for Category I precision runways. The visibility minimums come from the approved approach procedure and the lighting credit it allows, so follow the published procedure and the notices for the airport rather than inferring minimums from the system name.
Q7Is anything hazardous to work on?
Treat the circuit as live until it is isolated, locked out and proved dead under the permit-to-work. The flashers in MALSF and MALSR are normally capacitor-discharge units, so stored charge can remain after isolation; discharge as the manufacturer instructs before opening a head or cabinet. The structures stand in the runway protection area, so access and aircraft-movement controls also apply.
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