Thanks..

Always thought that they swung straight out.. but it would make sense to have that safety component.. After all this is an airplane door, and some sort of engineering design would go into it to make sure functions properly.. and not swing open inflight..

It is NOT impossible! A physicist with a bit of time to spare could calculate the force created on the door flying a 30000 feet, but it is not that great and the levered door handle provides enough force to break the seal in any case. One the pressure has equalised the door can be moved freely.

So can everyone confirm that there is no safety mechanism that prevents the door from being open, when a flight is in the air..

Do we have a maintenance / engineer that can confirm that the door does not have a latched safety mechanism.. perhaps controlled by the pilot..

As pointed out above, there is no lever that provides force to break the seal.

There's about a 7.5psi pressure difference between 8,000 feet and 35,000 feet.

http://www.sensorsone.co.uk/altitude...onversion.html

A door that's 6.5 feet by 2.5 feet is 2,160 square inches, which amounts to just over 16,000 pounds of force.

But the lever moves approx 1m to pull the door back from its seating by 1cm, so there is a ratio of 100:1, i.e. only 160 pounds of force is needed on the lever to move it away from the seal...

That was not my conclusion from reading the previous posts.

Its one thing to move the lever as roberino suggested..

Its another to actually pull the door back, and push it forward, as nerd analyzed..

You're under the false impression that the door handle provides some sort of exponential leverage. It does not. It only disengages the latches. With the pressure from inside the cabin pressing against the door and the pins it would take far more force than 160lbs to open a door inflight. I would suspect that the door handle would break before the door opened as they were not designed to be put under that much pressure.

The only item the flight deck crew has for the doors is indication of open or closed (outer handle unstowed on some doors). There is no mechanical or electrical system installed that remotely locks the door(s) from the flight deck (at this time). Any PA announcements related to arming or disarming the doors is related more for the emergency slides.

The size of the inner door handle is provided to allow for leverage to break the seal when unpressurized (if sticky), and to actuate the internal mechanism for engaging/releasing the locks and pins. Depending on design, the door may also move in some direction relative to the opening before being clear of any stops.

The force required just to actuate the mechanical locking system when the door is under load will be greater than can be applied to the handle irregardless of the force that will also be required to unseat the door to open it.

What about the lights on the door that say "cabin pressurized" and signs on the outside that say "don't open the door if light flashes"

What is the meaning of the phrase "doors to manual" - it implies, perhaps, that you can do nothing to the doors in flight.

I think it would be a brave person who could remain calm and logical in the event that someone seemed determined to open the door at 35,000 ft

In manual the emergency slide does not deploy when the door is opened. When doors are set to automatic the slide will deploy when the door is opened, such as in an emergency.

I'd be perfectly calm if some drugged up passenger tried to open the door midflight, because I know its not possible. A single human does not have the strength to overcome the differential pressure on the door. Bravery has nothing to do with it, it's knowledge. I have 100% confidence in the laws of physics continuing to work!

This explanation is correct about how exit doors function on many jets, particularly, the 757 involved in the incident.

Doesn't doors to manual.. signify a safey system switching gears to allow the doors to be manually opened as well?..

Meaning permission is given by the aircraft to unlatch the door, and having the door is possible?

I don't think anyone has to "ask" the aircraft to unlatch the doors. I don't believe there is any sort of computer control of door locks (not much point in having the doors lock like they do in a car).