Since opening in 2008, not a single bulb has been replaced on its immense single-span roof, and in some areas up to 60 per cent of the lights have blown, making the concourse increasingly gloomy. And an email obtained by news website Exaro suggested that Terminal 5's owners had been unable to solve the conundrum for some time.
Having tried cherry-pickers and hydraulic boom lifts to replace the downlighters, none were deemed to be practical or safe enough.
But now, a team of specialist wire walkers has been given the job of preventing the lights going out completely.
The email, which was reportedly sent to staff by Vicki O'Brien, head of Heathrow customer service at British Airways, revealed that all the light bulbs will now be changed in a project lasting four months. She wrote: "As many of you will have seen recently, the departures concourse has been becoming darker than normal in the late afternoons/evenings, as well as in the early mornings. The reason for the poor light is that 60 per cent of the downlighters have failed, and until recently Heathrow had no viable way to replace them.
"Various things have been investigated in the past five years, but for a number of reasons none of these were practical or safe. The good news is that Heathrow has now identified a safe and robust way to replace all the light bulbs, and this is high-level rope work carried out by a specialist company."
The terminal is a vast building and houses the world's largest controlled-lighting system, with 120,000 light fittings and 2,600 sensors designed to switch them off when no motion is detected.
The airport's operators now plan to replace all the bulbs in one go with LEDs that are expected to last at least five years.
A spokesman for Heathrow said: 'The current lighting on the terminal 5 concourse is being replaced with environmentally friendly LED bulbs. Contingency lighting has been used on the concourse while a viable and safe solution for replacing the lights was being agreed.'
A spokeswoman for British Airways said: "We are working with the owners of Heathrow Airport to improve the lighting levels inside Terminal 5 due to concerns over the brightness of the terminal in the winter months.
"Work has already started on the lighting improvements and we are confident that it will be resolved to our satisfaction very soon."
She added that she could not confirm whether the email by Vicki O'Brien was genuine.
news.com.au 25 Nov 2013