Description

On 29 April 2017, a Boeing 787-9 Dreamliner (G-ZBKF) being operated by British Airways on a scheduled international passenger flight from London Heathrow to Delhi with an augmented crew was in the cruise at FL350 in unrecorded day flying conditions when an EICAS indication of increasing cabin altitude occurred. Due to despatch with one Environmental Control System (ECS) inoperative, a descent was initiated, a PAN and then, as cabin altitude exceeded 10,000 feet, a MAYDAY was declared and an air turnback was made to London Heathrow without further event.

Investigation

A Field Investigation was carried out by the UK AAIB. Relevant recorded data was available from the duplicated Enhanced Airborne Flight Recorders (EAFR), flight data for the entire flight and CVR audio from climbing through FL110 eastbound until the end of the flight. Useful data were also available from the aircraft’s Central Maintenance Computing Function (CMCF) and from the Aircraft Health Monitoring (AHM) system, a ground-linked service that generates messages which can also be accessed by a flight crew but do not on their own require any action by them.

It was noted that the 50 year-old Captain had a total of 14,200 flying hours of which 1238 hours were on type. The experience of the First Officer was not documented.