What are side-row bars?
The two rows of red barrettes either side of the centreline in the inner approach — the ICAO side rows to 270 m and the FAA ALSF-2 red side-row bars — that give the pilot roll and lateral cues in low visibility.
Side-row bars are two rows of short red barrettes, one each side of the centreline, in the inner part of a Category II and III approach lighting system. They are what sets that pattern apart from Category I, which has the same white centreline but no side rows.
In the ICAO pattern the side rows extend 270 m from the threshold, with barrettes 30 m apart to match the centreline. The innermost lights sit at the same lateral spacing from the centreline as the touchdown zone lights. In the FAA ALSF-2 they are red bars of three lights on each side at nine stations, 100 ft to 900 ft from the threshold.
Their job is to outline the corridor: with only a short length of pattern visible at a low decision height, the red rows give the pilot a roll reference and show how far down the approach the lights have reached. The FAA names them in its operating rule for descending below 100 ft above the touchdown zone.
Frequently Asked Questions
Q1What are side-row bars?
They are the two rows of short red barrettes that run either side of the centreline in the inner part of a Category II and III approach lighting system. Each barrette is a short bar of closely spaced red lights set across the line of flight. Together they outline the corridor the pilot is flying down and give roll and lateral-position cues when only a short length of the pattern is visible.
Q2How are the ICAO side rows laid out?
There are two side rows, one each side of the centreline, extending 270 m from the threshold. The barrettes are spaced 30 m apart, matching the centreline lights, which gives nine stations on each side. Each barrette has several red lights, and the lateral spacing of the innermost lights from the centreline is set equal to that of the touchdown zone lights, within the range the standard gives. The 150 m crossbar fills the gap between the centreline and the side rows.
Q3What are the FAA ALSF-2 red side-row bars?
ALSF-2 has red side-row bars of three lights on each side at nine stations, 100 ft to 900 ft from the threshold, which is about the same extent as the ICAO 270 m. They replace the separate red pre-threshold and terminating bars that ALSF-1 uses. ALSF-2 also has a 500-ft bar of white lights beside the centreline.
Q4Why are they red?
Red separates the edges of the inner pattern from the white centreline and crossbars, so the pilot can read it at a glance. It also gives a visual reference that the FAA operating rule specifically names: below 100 ft above the touchdown zone, a pilot may not rely on the approach lights alone unless the red terminating bars or red side row bars are distinctly visible.
Q5Which approach lighting systems have them?
The ICAO Category II and III pattern and the FAA ALSF-2. The ICAO Category I pattern, MALSR, SSALS and ALSF-1 do not have side rows. ALSF-1 has red bars near the threshold instead, and an ALSF-2/SSALR dual-mode installation loses its side rows when it runs as SSALR in good weather.
Q6What must be right when installing them?
Station spacing, lateral position and alignment. The barrettes must be symmetrical about the extended centreline and set square to it, at the spacing and lateral position the standard gives, so the pilot reads a straight, even corridor. The red colour, intensity steps and aiming follow the standard and the manufacturer's instructions.
Q7What does a failure look like to the pilot?
A run of out-of-service barrettes on one side distorts the corridor and weakens the roll cue. A side that is dark or patchy while the other is complete is exactly what the inspection and photometric checks are looking for. Keep the series circuit arrangement in mind: a circuit fault can take several stations out at once. Treat the circuit as live until it is isolated, locked out and proved dead under the permit-to-work, and discharge any capacitor-discharge flashers as the manufacturer instructs before opening a head or cabinet.
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