Pilots fail to check switch left in off position by ground staff

A preliminary report by the Directorate General of Civil Aviation (DGCA) into the Jet Airways incident of cabin air pressure drop on-board a Jaipur-bound flight has indicated a lapse by on-ground maintenance check staff and the cockpit crew.

While the engineering staff on night shift are said to have left the switch in a wrong position, the pilots who arrived later failed to follow a check list, which could have possibly identified the ‘wrongly positioned switch’ and prevented the incident. Four Jet Airways staff — two pilots and two engineering staff — have been off-rostered from duty pending the DGCA investigation.

DGCA officials said the aircraft, a Boeing 737, had undergone a regular overnight maintenance check in Mumbai. “It was found that the engineering staff had left the switch in off position. The pilots later did not put it back in position as it remained untouched. Hence, it appears to be a case of a lapse at two levels,” an official said.

On September 20, VT-JGS, an 11-year-old aircraft, operating as flight 9W 697, was flying to Jaipur from Mumbai when nearly 30 passengers suffered nosebleed and many complained of headache during takeoff.

The drop in cabin pressure forced the pilots to return to Mumbai airport, where five passengers underwent medical examination. There were 166 passengers on board and five had to be taken to hospital.

According to aviation regulator officials, turning on the bleed switch results in release of air from the engine used to maintain oxygen inside the aircraft. Similarly, the packs are used to provide temperature conditioned air. “The initial lapse appears to have happened on ground hours before the flight. How and why it happened is being looked into. The Digital Flight Data Recorder is being studied to understand this,” an official said.

The aircraft which was cleared for flying a day after the incident had flown to Mumbai from Bengaluru on the midnight of September 19-20. Air Traffic Control records of Mumbai airport show that the aircraft had landed at 12.29 a.m. on September 20. For a five-and-a-half-odd hours till 6.12 a.m., when it took off for Jaipur, it remained on ground and was checked by engineering personnel, two of whom handled the cockpit.

The probe will also look into what the pilots did in the moments after oxygen masks dropped down, and if the cabin crew followed due process when the masks fell at 11,000 feet. “We will be examining every second of the flight. Since oxygen masks fell and passengers had to be hospitalised, this would include announcements made during the flight as well. This is done so that in the event of lapses, the DGCA can recommend a refresher training or any other requirements in following the standard operating procedure for the cabin crew, cockpit crew, and engineering personnel,” the official said.