A320, en-route, west southwest of Karachi Pakistan, 2018

A320, en-route, west southwest of Karachi Pakistan, 2018

Summary

On 5 March 2018, the crew of an Airbus A320 in descent towards Karachi observed a slow but continuous drop in cabin pressure which eventually triggered an excessive cabin altitude warning which led them to don oxygen masks, commence an emergency descent and declare a PAN to ATC until the situation had been normalised. The Investigation found that the cause was the processing of internally corrupted data in the active cabin pressure controller which had used a landing field elevation of over 10,000 feet. It noted that Airbus is developing a modified controller that will prevent erroneous data calculations occurring.

Description

On 5 March 2018, an Airbus 320 (A6-EIF) being operated by Etihad Airways on an international passenger flight from Abu Dhabi to Karachi as EY200 was in the cruise at FL 370 in day VMC when the crew noticed a slow rise in cabin altitude. Shortly before it reached the threshold for an excessive cabin altitude warning, the crew donned oxygen masks, commenced an emergency descent and declared a PAN to ATC until the situation had been dealt with. The flight continued on track to the intended destination and the remainder of the flight was without further event.

Investigation

An Investigation was carried out by the UAE GCAA Air Accident Investigation Sector (AAIS) using DFDR and CVR data and data read from the Non Volatile Memory (NVM) in both Cabin Pressure Controllers. Data from the QAR, which recorded cabin differential pressure and cabin altitude, neither of which were recorded on the DFDR, were also accessed.

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