Fewer lockdown flights blamed for incidents of smoke in aircraft cabins

The Air Accidents Investigation Branch filed a ‘serious incident’ report following the two occasions in June and July last year.

Aurigny took immediate action to rectify the suspected problem, attributing the incidents to aircraft not having been used much because of the pandemic, and a high amount of gaseous and suspended salt in the atmosphere resulting in corrosion forming on part of the engine air-switching valve, preventing it from closing fully.

With the valve partially open, contaminated air from the engine was able to enter the cabin.

Demand for flights slumped during the pandemic, but Aurigny worked its schedules to fall into line with the engine manufacturer’s recommended practice for running the engines, flying at least every 14 days.

The first incident on 29 June involved the G-OATR aircraft flying to Southampton, with six crew and 50 passengers on board.

It had last flown 10 days prior.

After being pushed back from the stand, the senior cabin crew member called the flight crew to say there was a ‘faint haze or smoke’ in the cabin which was increasing in intensity.

No smoke or haze was visible in the cockpit.

The commander turned off the cabin air recirculation fans when he was first alerted of smoke in the cabin and when he was informed that the intensity was increasing, he shut down both engines.

With no procedure in the checklist for ‘smoke on ground’, passengers were rapidly disembarked.

Three weeks later, a similar thing happened with the G-ORAI aircraft, which had four crew on board and 42 passengers.

Following the G-OATR event, Aurigny suspected that the low utilisation was affecting the performance of the environmental control system.

Therefore, the maximum interval between flights was decreased from 14 days to seven.

Despite G-ORAI having flown five days prior, the senior cabin crew member again reported a slight haze or smoke in the cabin after both engines had been started and the aircraft had been pushed back. Passengers were disembarked again after the engines were shut down and the propellers stopped rotating.

Aurigny then further reduced the interval between flights to three days. If an aircraft did not fly within three days, engine ground runs would be required. New, more regular, inspections of the air switching valve were introduced.

The AAIB report noted the safety action taken by Aurigny to help prevent corrosion forming on the valve and to amend the engine start procedure to reduce the risk of contaminated air entering the environmental control system.