KOLKATA: Seasoned pilots of commercial airlines are unable to comprehend how the crew of Jet Airways flight 9W 697 from Mumbai to Jaipur forgot to switch on the cabin pressurization system when their ears would have clogged and aircraft would have falshed a warning in the cockpit.“I don’t know how the pilots could have ignored the error. As soon as the climb begins, the pilots will themselves feel the effect with the ear drums beginning to hurt and the ears getting clogged due to the pressure surge. They will also begin to feel the heat as the pressurization and airconditioning system are integrated. After a while, they will be breathless. All this will happen in the cockpit before it does in the cabin. In addition, a caution will flash 120 seconds after takeoff. A louder warning will sound when it climbs 10,000 ft. I don’t see how two pilots can ignore them. I suspect a pressurization failure in the aircraft,” a veteran pilot said.The pressurisation system as well as the AC in the aircraft works on bleed air or compressed air from the engines. This hot air is cooled and fed to aircraft’s environment control unit that controls the cabin’s temperature as well as pressure. When the bleed switch is off, the AC also stops functioning.A pilot of a private airline said it wasn’t uncommon for pilots to forget switching on the AC pack immediately after takeoff, occuring in 2 out of 100 takeoffs. But in nearly all the cases, the pilot switches on the first AC pack when the ear gets clogged or the flight system sounds a caution.“There are two AC pack switches on the overhead panel. In several airlines, there is a ‘packs off-take off’ policy. This means the environment control system is switched off so that the plane can use maximum thrust on takeoff. The thrust reduction altitide for Airbus aircraft is 500-800 ft. That is when we switch on AC pack 1, followed by AC pack 2 after 10 seconds,” he pointed out.After takeoff, a plane climbs at the rate of 2,000 ft per minute. But pressurization ensures the cabin’s climb rate never exceeding 400 ft per minute. Thus when the plane cruises at 40,000 ft where air is extremely rarified, the cabin pressure maintained is at 8,000 ft, an altitude slightly lower than Tiger Hill in Darjeeling.In August 2005, a Helios Airways flight from Cyprus to Greece failed to correctly set the pressurization system. This caused all crew and passengers to suffer hypoxia. The pilot and others fell unconscious. The aircraft crashed when the fuel got over, killing all 121 on board. Investigators believe Malaysia Airways flight MH370 that disappeared also crashed in a similar manner.

Stay updated with all the Kolkata Latest News headlines here. For more exclusive & live news updates from all around India, stay connected with NYOOOZ.