Subject:  Re: Apeks & English grammar |
Author:
Lim Khoy Hing
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Date Posted: 12:49:36 06/21/09 Sun
Author Host/IP: NoHost/118.100.199.104
In reply to:
Little Grasshopper
's message, "Re: Apeks & English grammar" on 04:42:12 06/21/09 Sun
>Captain,
>
>I take my hat off to you, for a very readable article.
Thanks Grasshopper,
In fact I reposted the article in the June issue by mistake for NBH to read and not the April one. So here is the previous one on "Of Pressures and Flying". Sorry Insp Kluso...
Of Pressures and Flying
Recently, whilst scanning through the cockpit for the closed-door indications prior to departure, my eye caught something unusual. Someone was attempting to open the emergency exit door on the ground! I immediately alerted my SFA (Senior Flight Attendant) to find out what could have triggered the warning. He confirmed that a mischievous passenger was playfully testing the handle and it actually opened the emergency door. He had probably been briefed that he would act as the “able-bodied-man” to assist the opening of the door in the event of an evacuation as he was occupying the emergency seat.
The SFA gently cautioned the passenger who then sat meekly down whilst we completed the boarding and took off with the emergency door firmly shut.
Can the cabin doors be opened in flight?
A fearful flyer once asked me whether the doors of the plane could be opened during flight should a passenger be mad enough do so. The answer is No. The smaller emergency exits are prevented from opening during flight by the outward-pushing forces of a pressurized cabin. These doors are like drain plugs that open inward and any person, out of his mind, would not be able to overcome these forces until the plane is depressurized.
In the case of the larger cabin doors, they are safely secured by a series of locks that are subject to the similar outward-acting pressure that prevent any attempt to open them.
Even though it is impossible to open the cabin doors in flight, I wouldn’t recommend anyone to mess around with the door handles as it would not only be futile but this crazy guy would be answerable to the security at the destination.
Why the cabin is pressurized?
A jet plane is designed to cruise at a higher altitude in order to save fuel. However, flying high comes at a cost - a lack of oxygen. So, in order to ensure that there is enough oxygen for the passengers to breathe at such high altitudes, the cabin must be pressurized.
Very simply, as one climbs, the air becomes thinner and the amount of oxygen decreases. So when the cabin is pressurized as the plane ascends, it has the effect of squeezing the air back together and recreating the denser oxygen-rich conditions found closer to the ground.
For instance, when flying on the Airbus A320, the cabin altitude is set to ground level when you are at 20,000 feet and 6,500 feet when the plane is actually at 35,000 feet. Pressurization also makes it more comfortable as it allows for gradual equalization of your ears as the plane climbs to the cruising altitude.
Do you know that when you are in a pressurized cabin, it is almost like as if you are inside a balloon? The cabin expands slightly when pressurized by the air from the engine compressors but it is nevertheless regulated by valves to ensure that it maintains a safe and comfortable environment.
Cabin depressurization
On 27 July 2008, a 17-years old Qantas Boeing 747 flying from London to Melbourne suffered depressurization when, according to the investigators, an exploding oxygen bottle probably ripped a hole the size of a mini-van on the right side of its body, forcing it to make an emergency descent from 29,000 feet to 10,000 feet at Manila.
Do not let that worry you, as all pilots in AirAsia are diligently trained on the emergency descent procedures. It takes about 5 minutes to descent from 35,000 feet to 10,000 feet where oxygen is no longer required. The oxygen from your drop-down mask will last approximately 15 minutes and you will still have about 10 minutes to spare!
It is therefore important to pay careful attention to the emergency demonstration while you are flying on Air Asia Airbus A320 (all planes are almost brand new) on the use of these oxygen masks as they drop down from the ceiling during an emergency descent, as this could save your life and those around you.
Why is there a need to offload unaccompanied bags?
Losing pressurization is not by itself dangerous (as shown by the Qantas Boeing 747 above where there were no casualties) but what is most damaging is depressurization caused by explosive devices.
Yes, depressurization due to explosive devices is a different kettle of fish. On June 23, 1985, one Air India flight operating on the Montreal-London-New Delhi route exploded over the Irish airspace. Investigators found that one of the passengers had checked in his bag (with explosives) at Vancouver International Airport but failed to board the flight.
So there are times when passengers have checked-in their bags but forget to board as they got too engrossed with shopping or misread their departure times. In these situations, if they still fail to board after several announcements, instructions would be issued to the ground handlers to offload every single checked-in bag for the above reason.
Remember, the next time you are shopping at the airport whilst waiting to board, make sure you keep an ear out for your boarding announcement, or you will end up causing great annoyance to your other fellow passengers for the delayed departure!
Wish you a safe flight!
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Captain Lim Khoy Hing is an AirAsia pilot who has logged more than 23,000 flight hours to date. When he’s not flying the Airbus A320, he generously shares his opinion on aviation issues and the benefit of his experience with others. For more air travelers and aviation stories, you can visit his website at www.askcaptainlim.com
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