OT, What would happen if...

[Geospark]

I saw a programme on National Geographic (Air crash investigation series) where they showed an aircrash involving a boeing aircraft, the fuselage had developed a large hole (at the top of the aircraft) due to structural failure, an air hostess standing directly underneath was sucked out...in fact she was the only casualty, the body was never found as this happened over the pacific ocean, but the pilot was able to land the plane safely...

So how do you explain the above incident ???...

With pleasure...

arbj,

I have explained briefly the different types of cabin decompression which may occur on an aircraft, but I'll summarize them again to be clear...

Explosive Decompression -
Huge breach in fuselage
Near instant cabin decompression - typically <0.5 sec
High risk of lung damage from sudden deflation of lungs
High risk of occupants or objects being forced from the aircraft
High risk of being struck by flying occupants or objects
High risk of exposure to extremely high wind speeds at minus temperatures

Rapid Decompression -
Moderate breach in fuselage (up to roughly 10" sq)
Fast cabin decompression - typically >0.5 sec
Lower risk of lung damage - decompression slow enough to allow the lungs deflate normally
Low risk of occupants or objects being forced from the aircraft
Moderate risk of being struck by flying objects
Moderate risk of exposure to extremely high wind speeds at minus temperatures

Gradual Decompression -
Small breach in fuselage
Slow cabin decompression - one minute to half an hour depending on altitude
No risk of lung damage
No risk of occupants or objects being forced from the aircraft
No risk of being struck by flying occupants or objects
No risk of exposure to extremely high wind speeds at minus temperatures
High risk of the gradual onset of hypoxia - leading to unconsciousness

I saw that program too and, as per the links (thanks Eric), it was concluded that the structural defects led to a violent and catastrophic explosive decompression, not rapid decompression. With explosive decompression all bets are off as to what the outcome might be.

...Rapid decompression doesn't start sucking people and seats out of the opening Hollywood style!...

What did I mean here?

I didn't mean that rapid decompression could never force an occupant from an aircraft. The Hollywood reference was to where you see a bullet supposedly fired in an aircraft cabin, or even a larger hole, and then you see passengers continuously clinging to a seat headrest with their legs dangling in mid air as though they are continuously being sucked toward the breach. This doesn't happen in reality.

Whether it's rapid or explosive decompression, they typically only last from hundreds of a second to a second or two. The only difference is the velocity at which the cabin decompresses during explosive decompression is much more dangerous for the occupants. Once the pressure in the cabin has equalized with the atmospheric pressure outside the aircraft, the vacuum effect stops. If none of the occupants have been forced from the aircraft during decompression, and all of the occupants now have oxygen masks on, and the pilots are able to maintain flight stability, then the only other dangers to the occupants are the high wind speeds at minus temperatures traveling in and around the cabin. This could blow unrestrained occupants, or objects through or out of the aircraft, or it can cause frostbite or hypothermia. On Aloha Airlines Flight 243, another stewardess was in the aisle unrestrained, but managed to hold on while lying on the floor until the plane landed.

A breach, from a normal split across the rivet holes on the outer skin, should stay confined to the 10" sq sections of ribbing and tear straps, should it give way. This contains the size of the possible breach to an acceptable level where only rapid decompression should occur.

Why did this breach elevate to an explosive decompression level?

The fact that there was a severely compromised outer skin, due to epoxy corrosion and metal fatigue across the rivet holes of several adjacent sections - caused by having been too long in service in a coastal area - the conditions for explosive decompression were created.

...an air hostess standing directly underneath was sucked out...

...I suspect the flight attendant may have been blown out, rather than sucked out...

It's actually a matter of perspective...

From inside the cabin she was blown out, from outside the aircraft she was sucked out. For me, I think the general consensus should be to look at it from where we are most likely to be i.e. inside the cabin. So I would prefer to say she was blown, or forced from the aircraft, but I do see a lot of references to occupants having been sucked from an aircraft. Unfortunately for them, blown or sucked, the results are the same.

George

 

[Geospark]

...if the door opened the plane would implode and there would be pieces everywhere where they had the last blip on the radar...

...there would be a bunch of pieces and parts of the plane everywhere if that happened, implode or explode it would come apart and there would be a large debris field at the last point of contact...

...You really missed the point...

git,

Now that you've made your point twice, I'm pretty sure I got it the first time, but I also see now that you've missed my point. I was just trying to explain the physics involved here and how what your thinking happens doesn't. I thought if I explained how an implosion is not what happens when the door opens, you would think about this scenario's outcome differently, and perhaps come back with a different slant on things? You're sticking to your original statement, and that's ok my friend.

I'll come at it another way...

In your first statement,

a) You're stating that the plane would implode and there would be pieces everywhere.

b) You're stating that every time this action happens, the opening of an emergency door mid-flight, an implosion will occur, breaking the plane up.

In your second statement,

a) You're stating that whether the plane implodes or explodes, it would come apart and there would be pieces and parts of the plane everywhere, scattered across a large debris field.

b) So you're obviously still stating that every time this action happens, the plane will basically be torn apart.

Where I feel you're missing my point is that an implosion and an explosion are two very different and opposing actions, and have very different and opposing reactions.

As I already pointed out, for the aircraft to implode, the atmospheric pressure outside must be far greater than the pressure inside. This is not the case with an aircraft cabin, but let's assume it is. When the cabin fuselage is somehow opened, the enormous external pressure will cause the aircraft to implode inward on itself. The effect is such that the aircraft will crush inward with tremendous force, causing it to crumple up into a much smaller mass like crumpling a crisp bag in your hands. Certain materials by their nature, such as the glass from the windows and windscreen, will shatter as this happens and may be forced violently outward, but the rest of the aircraft, and its contents, will continue to be reduced to whatever size the external force of pressure exerts on it until the two opposing pressures have equalized. Depending on what the original differential pressures were, the aircraft could be reduced to half its original mass, or even smaller. The point is that, as a result of an implosion, the aircraft is reduced to just one considerably smaller mass, and will then simply fall from the sky. If it lands in the ocean it will most likely just sink, if it lands on land it may or may not break apart. The crushing pressure of an implosion would most likely have squeezed the aircraft so tightly that the mass would be very difficult to separate again.

So hopefully we can now set aside the notion that an implosion could possibly happen here, and also the notion that if it could happen, the plane would break apart into several pieces. So that leaves the explosion theory.

If there was a large enough explosion, yes of course it would tear the aircraft into many pieces and they would most likely end up scattered over a wide area.

But I also feel that you're missing a more important point here, your b) statements above. Just because the door has been opened does not automatically create an explosion that would tear the aircraft apart into pieces. The door is not a bomb, or a detonator. It's acting like a plug, keeping the higher internal pressure inside the cabin. If it were to fail open somehow, an explosive decompression would occur, but this is is not an explosion in the incendiary sense of the word. This is the explosive release of pressurized air from a pressure vessel i.e. the cabin. The door would be blown away and, if structurally compromised, any surrounding parts of the fuselage near the door may be blown out. In most cases where the surrounding structure is sound, only the door and whatever the explosive decompression may have also blown out from inside the cabin will be ejected. It's the collateral damage which may occur during, or after an explosive decompression which may end up causing the downfall of an aircraft, such as debris being sucked into engines, starting a fire, causing a fuel leak, severing vital services running under the floor, sucking the pilot out the windshield, it's happened! As I said, with explosive decompression, all bets are off, but it still doesn't mean that every case of rapid, or explosive decompression will result in the aircraft exploding into pieces.

Here's a funny, but informative take on some of aviations major misconceptions about flight disasters and Hollywood's role in promoting them.

Peace

Now dear, where did you say you wanted to fly to this summer?

George

 

[Ken Roach]

The closer I get to the manufacturing side of commercial airplanes, the more I want to cross the ocean on something safe and sturdy, like a rowboat.

 

[Geospark]

I need to stop watching National Geographic and The Discovery Channel...but right now...I need to go to bed!

Good news is though, I have today off!

G.

 

[harryting]

One of my brother used to fly the A330, now he's flying the 777. Airbus and Boeing have very different control philosophy and both have their pro and cons. Airbus like to say their plane is pilot proof (until the Air France 447 incident).

there's also one incident that has received no attention from the general public. That when all three AOA sensor froze up during a climb on a Airbus, the plane's computer would think it's about to stall and push the nose down. This is bad since the plane would dive right into the ground regardless of pilots' input. Yes, this actually happened once.

http://news.aviation-safety.net/201...rgency-ad-on-a330a340-angle-of-attack-probes/

Back to the event at hand, the most likely scenario I can think of is that one of the pilot is involved or someone who has knowledge of piloting a plane.

 

[Lancie1]

GIT,

I see that you have greatly expanded your business and are now offering repairs to some Allen Bradley PLC parts. That is a great service! Congratulations to one of our own!

http://www.plccable.com/allen-bradley-repair/

 

[geniusintraining]

GIT,

I see that you have greatly expanded your business and are now offering repairs to some Allen Bradley PLC parts. That is a great service! Congratulations to one of our own!

http://www.plccable.com/allen-bradley-repair/

Hi Lancie1,

Thank you very much... a lot of my products are from people that come here and I have built my business from what I have read here or from what the members have asked me to make, I sell 3 product lines now that are directly tied to 3 plctalk members I am a big supporter now of small business after I see how they are affected and how it impacts others that are trying to better themselves

Its a great since of accomplishment to think back when I first joined this website I was just trying to figure out how to edit a DL06 (Thanks Bernie!) and started a business from that and thanks to people like yourself and others that enjoy helping I am now able to help others (and make a living doing it)

git, ....

George, you just have way to much time on your hands

 

[Geospark]

George, you just have way to much time on your hands

I wish git! Some of these posts can take me the length of the day to compose. I start then have to leave it, come back later do another bit, eventually rap it up. Some can take a couple of days. My real problem is my attention to detail, I just can't reply off the cuff. I actually don't have enough time to contribute here as much as I'd like to, but when I can, I try to make it count.

I had a look at your website too. Nice selection there and well done.

G.

 

[geniusintraining]

Hi George

Thank you very much...

I often speak from 'off the cuff' like imploding of a air plane... I do know when I wrong I will be correct by my friends


-------------------------------------

Back on topic (OT)

As the plot thickens... I hope there is a happy ending for the family's that wait to hear news or I hope there is at least an ending, I could not imagine the pain they are going through

 

[baldone]

One of my brother used to fly the A330, now he's flying the 777. Airbus and Boeing have very different control philosophy and both have their pro and cons. Airbus like to say their plane is pilot proof (until the Air France 447 incident).

there's also one incident that has received no attention from the general public. That when all three AOA sensor froze up during a climb on a Airbus, the plane's computer would think it's about to stall and push the nose down. This is bad since the plane would dive right into the ground regardless of pilots' input. Yes, this actually happened once.

http://news.aviation-safety.net/201...rgency-ad-on-a330a340-angle-of-attack-probes/

Back to the event at hand, the most likely scenario I can think of is that one of the pilot is involved or someone who has knowledge of piloting a plane.

The Air France 447 incident is particularly mind boggling to me.
I have about 100 hours in a C172 and the last thing I would do if I did not trust my airspeed indicator would be to pull up. Level out and set throttles to where you are pretty sure you will keep flying.

Commercial airliners for the last 10+ years have had GPS which even though it would only indicate ground speed should have been enough to keep you flying until you figured out what was wrong.

The pilots really FUBARed.

 

[RheinhardtP]

Too many smoke screens in BS information being put out there. Will ignore this story till someone starts talking sense!!