The aircraft was being flown from Exeter to Faro in Portugal and whilst passing FL275, cleared to FL280, the ALT warning illuminated on the flight deck. The passenger oxygen masks dropped down and the passengers successfully put them on. The pilot had difficulty donning his mask, which had become entangled on items behind the pilot’s seat. He informed ATC of the situation and carried out an emergency descent to FL100 and diverted back to Exeter, which was also the operator’s maintenance base. The return to Exeter was uneventful and a normal approach and landing was made on Runway 26. On shutting down the aircraft, the pilot felt unwell but he thought this may have been a result of the incident.
The maintenance organisation identified two sources of cabin pressurisation loss; the outflow valve and a landing gear seal. Both were replaced and an air test confirmed the problem was rectified. The operator issued a notice to aircrew reminding them to ensure the oxygen mask was unobstructed before flight, and a new mask holder was installed in the flight deck roof to ensure its unimpeded use.
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Published 8 February 2018