An investigation report by the Directorate General of Civil Aviation (DGCA) on the mid-air cabin pressure failure in an Air India flight from Mumbai to Kochi last year, has blamed faulty flow control valves which led to alarm bells going off at 39,000 feet and oxygen masks being deployed.
Emergency landing
The incident on February 27, 2017, saw the aircraft with 58 passengers and crew undertake an emergency landing in Mangaluru. This was followed by an investigation by the DGCA’s Air Safety Directorate for lessons that may help prevent such future incidents.
The report said the pilot declared an emergency during cruise when there was a rapid increase in cabin altitude due to cabin pressurisation failure.
“The decision to divert and land the aircraft at Mangaluru was appropriate. The pilot made a safe emergency landing. There was no injury to any of the aircraft occupants and also there was no damage to the aircraft. Thus flight crew qualification and operations of the aircraft is not considered a contributory factor to the incident,” the DGCA report said.
The report added that weather did not contribute to the incident either.
No pre-departure snag
The report said there was no pre-departure snag and the cabin pressurisation failed during cruise, which led to declaration of emergency and deployment of oxygen masks. It explained that upon inspection, flow control valve no.2 was found to be sluggish and was confirmed to be faulty.
“The aircraft was being served by only one pack for air conditioning. There was also a fault message for flow control valve no.1. The snag on this flow control valve could however not be confirmed on inspection. This anomaly in serviceability of flow control valve is possible as environmental conditions are not the same at higher altitude (39,000 feet) and on ground. Flow control valve no. 2 malfunctioned and [bled] through flow control valve no.1, which was not sufficient to maintain pressurisation in the cabin at higher altitude. Insufficient bleed led to depressurisation of the cabin,” the report concluded.
Following the incident, Air India carried out detailed checks and snag rectification procedures, replacing control units and flow valves that were tested again and found to be satisfactory.
