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Another flying blonde?

Discussion in 'General Motorcycling Discussion' started by incitatus, Nov 21, 2005.

  1. "Woman tries to leave plane mid-flight. A drunken French tourist with a fear of flying tried to open an Australia-bound jet passenger door in mid-flight to have a cigarette, a Brisbane court has heard."

  2. PMSL...
    Sounds like she was sleep walking... or stressed and out of her mind (in a not so funny way).
  3. What an idiot :LOL:

    Bit tough getting a conviction recoreded bc of it tho
  4. Wouldn't say so, really. She did endanger all those aboard the aircraft. If you can get a conviction endangering half a dozen (at most) doing 200km/h on the streets, then you can get a conviction endangering a couple of hundred trying to depressurise an international flight. :LOL:
  5. She wouldnt have the physical strenght to open if even if she
    really wanted to


    If so, where is the danger?
  6. The article states that she is 34 and a smoker. Is that what you're basing your presumption on?
  7. Neither would you, or anybody else, unless they had first 'armed' the door. Next time you fly, listen to the commands the Captain gives the cabin crew.

    Just before takeoff he will call "Cabin crew disarm doors and cross check", the cabin chief will then turn off the solenoids that permit unlocking of the doors, making it impossible to open them. After the aircraft lands he will call "Cabin crew arm doors and cross check" and the solenoids will be turned back on for exit.
  8. bullshit. The differential pressure across the door amounts to a minimum (at cruise) of something of the order of 10000' or 9" of mercury or 36kPa. (this is cruising at 20000' - most cruise at 30000 or 40000' increasing the pressure difference)

    For an average aircraft plug door (door bigger than the hole in the plane) of about 2 square meters, load on the door is about 36000N/m2*2m2 = 72000N or 7300kg. With a lever that short, good luck to any of you!

    The 'arming' doors routine is keying the release mechanism for the escape sliderafts. The disarm is so that when you open the door at the terminal... I think you can guess the rest.
  9. I thought they armed the doors at takoff and disarmed them after landeing. I presumed it was so they could blow them if they need to, but what bonox states seem possible.

    So Bonnox, why is there a possitive pressure on the side door of an aircraft? And isn't the area above the wing a low pressure zone?
  10. to avoid the requirement for supplementary oxygen, passenger aircraft cabins are maintained at what is known as a 'pressure altitude' no greater than about 10000 feet. This is the pressure at which most of us can breath fairly normally for short periods as long as we are not engaged in physically demanding work. Think of it as climbing a mountain - the effective pressure in the cabin is kept at a mountain height of no more than 10000 feet (a little less than half the height of mt everest)

    We can happily survive in lower pressure environments, but since the ability of haemoglobin molecules in our blood (the ones that carry oxygen) respond to the partial pressure of oxygen available, the lower the pressure, the more concentration you need - ie at anything above about ten thousand feet, when oxygen concentration is about 18% (same as sea level), to get enough into your blood to do the job, the concentration in the gas you are breathing needs to rise up to 100% oxygen at about 35000 feet.

    At above 42000 feet however, even with 100% oxygen supply you can't breathe at all because the partial pressure of carbon dioxide you are breathing off is greater than the pp of oxygen so the haemoglobin never gives up the C02 for 02. (coincidentally, at very low pressures, you blood will start to boil). This is the reason high altitude craft (and spacecraft) have pressurised cabins and suits.

    The pressure maintained in an aircraft cabin aims to avoid all of these problems, and the masks that drop from the ceiling during a depressurisation are to provide enough O2 for you to not black out in the time it takes for the plane to come down to a low enough height that you can breathe the air outside. The consequence of this is that as you go higher in the atmosphere, density (and pressure) fall, so the aircraft cabin becomes a giant gas cylinder with a higher pressure inside than outside. It is this differential pressure than means there is no need for door locks on passenger aircraft - you couldn't possibly open the door even if you had help.

    Just to be clear, there are no pyrotechnics on passenger aircraft to 'blow doors off'. The escape slides are all powered by compressed nitrogen or C02 - the 'disarm' merely stops you pulling the triggers on the gas bottles in the doors.
  11. Pressure at sea level is 14.7 psi, at 40,000 2.72psi, a differential of 11.98psi. Since the door opens outwards, and the pressure is 11.98psi higher in the cabin, this would actually make it very easy to open the door. (for simplicity I have ignored the fact that the cabin is not pressurised at exactly 1 atmosphere).

    The above is also true, the functions are simultaneous. However in normal operation the door lever does not directly operate the lock, it functions as described, using a geared motor and locking solenoid. In the event of total power failure, a 'dead man' mechanism will allow the door to be opened using mechanical advantage only. see below,

    http://www.abrahamassociates.com/Graphics/Arming lever.jpg

    I am always open to critique, but sometimes the 'engage brain before operating mouth' rule can be your friend, especially when bandying around words like "bullshit".
  12. more bullshit - passenger aircraft doors are all mandated to be what are know as plug type doors - the door is bigger than the hole, and they all open inwards.

    The outward type you see have complicated mechanisms to fold the top and bottom of the door, bring it into the plane, and then twist it out through the hole (eg boeing 737, 747 etc). Others open inside only (eg 767).

    Moreover, because of fatigue and stress levels in aircraft, the plane is never pressurised to sea level air pressure at 40000' - the vehicle would be so heavy you'd never get it off the ground - another reason you won't ever find LPG powered aircraft.
  13. PS, incitatus

    abraham make cabin training simulators, nothing to do with real doors! FAA regulated emergency exit doors prohibit reliance on anything other than mechanical release.

    PPS: the introduction of mandatory cabin vents was introduced with the fire and subsequent deaths of all aboard because fire crews were unable to open the doors due to the unreleased pressure inside the cabin.
  14. Incorrect. "plug-type" doors are not "mandated". I have flown numerous types with conventional wedge doors. It is in any case a moot point since your original argument was based on a pressure differential that was 180deg in error, and that was what I was responding to.

    Please read my posts before responding. Quote "for simplicity I have ignored the fact that the cabin is not pressurised at exactly 1 atmosphere".
  15. and how many of these FAR25 aircraft you've flown on (ie the pressurised commercial passenger transporters with greater than 10000 foot operating ceilings capable of flying hong kong to brisbane) have wedge type doors?

    I hate to say it, but RTFM


    look for regulations, current regs, FAR25, access doors.

    My posts are all in relation to the original new post - smaller wedge type doors often come with electronic cockpit operated door locks, but these a/c are NOT PRESSURISED.
  16. hmm, cockpit is automatically filtered :D

    what else would you call the flightdeck of a small plane?
  17. I am aware of that, but couldn't find a better picture. As to "reliance on anything other than mechanical release" I have already described the 'dead man' mechanism that meets that requirement.

    I realize that you are intent on impressing everyone with your knowledge. But my original point was that the door is electronically locked during flight, and unlocked on arrival. Do you take issue with that point? Secondly, the issue of whether an aircraft is fitted with plug or wedge type doors is irrelevant to the above.
  18. You've got to love these forums... :LOL:
    Netrider is a wonderful educational resource - and not just for motorcycles. :LOL:

    Where else would you find a heated discussion on the design of aircraft cabin doors?

    :LOL: :LOL:
  19. Indeed.
    The story was posted simply to comment on the fact that someone TRIED to open a plane door, not so people could theorise about whether or not it was possible.
  20. How is it not relevant? The comment was about opening doors in flight of a cathay pacific pax transport! Reasons I have given!

    I'm not intent on impressing anybody - as a professional aerospace engineer involved in oxygen and cabin environmental systems on a large range of a/c operated by australia's largest airline and was involved in similar for BAE systems and airbus, why would i not take umbridge at statements that are blatently crap?

    This thread is turning to pox - who's up for a ride?