Easyjet A319 near Birmingham on May 11th 2019, fumes and smoke in cockpit
Last Update: May 21, 2020 / 17:28:21 GMT/Zulu time
The AAIB released their bulletin concluding the probable cause of the serious incident was:
The aircraft had a smoke and fumes event that was probably a result of dust accumulation on its TRUs. The pilot’s oxygen masks misted up shortly after donning, due to a combination of the environment in which they were stowed, the crews’ breathing rate and the condition of the lenses. This left them unable to see the flight instruments, resulting in the commander removing his mask. Selecting the emergency pressure setting helps clear a mask and reduced exposure to any remaining smoke and fumes.
With respect to the source of the odour and smoke the AAIB reported:
Initially the operator’s maintenance control remotely diagnosed the source of the smoke as a faulty recirculation fan but, upon inspection, both fans were found to be in a “very good condition”.
As the source of the smoke was not positively identified, and based on previous experience with burnt smells in the cockpit, the transformer rectifier units (TRU) were suspected as being the source. In previous cases of electrical burnt smells in the cockpit, dust contamination of the TRUs was identified as the cause.
G-EZNM’s records showed neither TRU had been replaced since the aircraft was manufactured, since when it had accumulated more than 40,000 flying hours. Upon inspection, the TRU ventilation grids and hot air exhaust ducts showed light dust accumulation and no other abnormal findings. They were cleaned and reinstalled.
As a result, the aircraft manufacturer has introduced a cleaning procedure for the TRUs in the AMM. This was incorporated into the May 2019 revision of the AMM revision.
The AAIB analysed:
The crew experienced a smoke and fumes event in the cockpit and subsequently initiated and completed a successful diversion to Birmingham.
About 90 seconds after donning their masks both of the crew’s masks became obscured by condensation. The misting obscured the flight instruments leading the commander to remove his mask. While this decision was judged to achieve the greatest overall aircraft safety in the circumstances, it exposed the commander to potentially hazardous fumes.
Both emergency pressure selectors were found not to have been rotated to the emergency position. The commander was unable to recall if he had selected emergency. However, if they both had, even for a short period, it is likely the condensation would have been removed, enabling the commander to keep his mask on and breath 100% oxygen during the remainder of the flight. This would probably have improved the physiological condition he reported, which may have been caused by inhaling fumes. Removing the condensation in this way would also have allowed the co-pilot to properly monitor the aircraft’s flight path. The option to select emergency was stated in the QRH checklist. The Flight Crew Operating Manual (though not as readily accessible) contained the additional information that this selection would remove condensation.
The results of the fogging test conducted after the event were inconclusive because the simulator did not replicate the cockpit environment and the testers were not exposed to the stress and increased breathing rate probably experienced during the incident.
The masks are likely to have misted up during the event due to a combination of the cold stowage compartment, a relatively warm cockpit, damage to the anti-fog coating and the crews’ higher breathing rate.
This incident highlights the importance of fully understanding mask operation, including what selections are available and how to use them.
This article is published under license from Avherald.com. © of text by Avherald.com.
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