Perimeter lights define the edge of the landing area. They are the outline a pilot lines up
on, and because the helideck of an offshore installation is a platform surrounded by nothing,
that outline is the only thing distinguishing the landing area from the sea beyond it.
The specification is largely dictated by CAP437 rather than chosen, and Q-Aviation state the
requirements plainly on their own page: perimeter lights, spaced at intervals of not more than
3.0 metres, should be fitted around the perimeter of the landing area of the helideck, and they
should not exceed a height of 25 cm above the surface of the helideck. Both figures matter. The
spacing determines whether the outline reads as a continuous edge rather than a row of dots, and
so the quantity for a given deck follows arithmetically from its perimeter. The height limit is
a safety requirement - anything taller is an obstruction to the aircraft and to the people
working on the deck.
Q-Aviation's unit is a 50 candela LED steady-burning light, explosion-proof for hazardous
area offshore facilities and compliant with CAP437 and ICAO Annex 14. Steady burning rather than
flashing is the correct behaviour here: the perimeter is a shape to be perceived, not a signal
to be noticed, and flashing lights around an edge would make the outline harder to read.
The configuration options are the practical part of specifying these. Input power is
available as 100-240 VAC or 24 VDC, which lets the lighting follow whatever supply the deck
already has - and 24 VDC is what allows the perimeter to sit on a battery-backed supply, so the
outline survives a power event. Housings are offered in powder coated aluminium in RAL5015 with
borosilicate glass, or in SS316 powder coated. That choice is worth making deliberately rather
than by price: aluminium is lighter and adequate in most positions, while 316 stainless is what
survives a deck that is permanently wet with salt. Borosilicate glass is specified because it
takes thermal shock - a hot fitting hit by cold spray - without failing.
Being a deck-edge fitting, these are walked past, washed down, and occasionally struck. They
are driven as a group from the helideck control system, and on Q-Aviation's WEX4 and WEX5
control systems the perimeter circuit is one of the standard switched groups.
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