haz777
Topic Author
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Joined: Tue Oct 23, 2018 1:33 pm

Explosive decompression question

Tue Oct 23, 2018 1:44 pm

Hi, I have a question regarding explosive decompression, particularly in cases following an onboard explosion. How can explosive decompression rip an aircraft apart after, for example, a bomb detonates? Does it tear of the fuselage section's bolts that hold it together? I have trouble imagining just a small hole being able to take down an airliner.

I know there have been explosions at low altitudes and the aircraft has remained structurally intact and I know there is Phillipine Airlines 434, but in that case there was no damage to the hull. My second question which I am dying to know is has there ever been a case when an aircraft has survived a high altitude bombing (28,000 + feet) and also sustained damage to the fuselage without disintegrating in mid air? Or a 10 inch hole at high altitude seal an aircraft's fate. I have tried searching far and wide but couldn't find what I was looking for so thought I'd ask on here since it's bugging me

Many thanks

Harry
 
GalaxyFlyer
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Re: Explosive decompression question

Tue Oct 23, 2018 3:04 pm

Depends greatly on where the explosive is located on detonation, see PAA 103 where are rather small charge did enough skin damage to let the 340 knot slipstream do the rest.

A bomb went off in an airliner in the early 60s, B707 IIRC, the plane survived the explosion, but in the ensuing haste to descend came apart in the teens as the IAS built up. Now, if damage cannot be confirmed, emergency descent is done at the indicated airspeed at the time of the explosion or structural damage.

GF
 
BoeingGuy
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Re: Explosive decompression question

Tue Oct 23, 2018 4:12 pm

GalaxyFlyer wrote:
Now, if damage cannot be confirmed, emergency descent is done at the indicated airspeed at the time of the explosion or structural damage.

GF


To be specific, an excerpt from the Boeing QRH procedure for CABIN ALTITUDE (decompression) is:


Without delay, descend to the lowest safe altitude or 10,000 feet, whichever is higher.

To descend:

•Move the thrust levers to idle
•Extend the speedbrakes
•If structural integrity is in doubt, limit airspeed and avoid high maneuvering loads
•Descend at Vmo/Mmo


So there is guidance on possibly limiting airspeed if structural integrity is in question.
 
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Balerit
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Re: Explosive decompression question

Tue Oct 23, 2018 6:59 pm

Aircraft structure is designed to carry the load should something small pierce the pressure hull. What a bomb does is damage this redundancy causing several stringers or frames to give way. Just remember that a fuselage under pressure is like a balloon waiting to pop. Structural failure, ie metal fatigue causes the exact same result. There are some who believe that all the B747 so called bombings were in actual fact section 41 structural failure.

There was recently an A320 that suffered a bomb blast and made it safely back to the ground, think it was Air Egypt or something like that. The bomber was the only casualty.
Licensed Aircraft Maintenance Engineer (retired).
 
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litz
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Re: Explosive decompression question

Tue Oct 23, 2018 7:36 pm

There have been a few aircraft that suffered non-explosives related explosive decompression, too ... Aloha and UA (737 and 747, respectively) being the most newsworthy due to the extreme fuselage damage.

There have also been a couple of SWA 737s that had much smaller "blowouts" as well.
 
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Francoflier
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Re: Explosive decompression question

Tue Oct 23, 2018 11:58 pm

Maybe it's paranoia talking here, but does a very specific question about bombs and airplanes from a new user whose very first post it is seem suspicious to anyone else?
I'll do my own airline. With Blackjack. And hookers. In fact, forget the airline.
 
haz777
Topic Author
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Joined: Tue Oct 23, 2018 1:33 pm

Re: Explosive decompression question

Wed Oct 24, 2018 12:21 am

Thanks for your answers guys, the incentive for my question was Pan Am 103 and the recent Metrojet bombing. I am trying to get my head around these disasters as it seems so horrific that such a strong jet can break apart in mid air and kill so many people. If only we could find a way to prevent these disgraceful events. Hopefully airlines will adopt the recently developed kevlar bomb bag. Thanks for your answers BoeingGuy, GalaxyFlyer and Balerit, very interesting responses. Btw Balerit, that was a Daallo airlines a321 on the way to Djibouti, I was impressed by the aircraft's structure but the captain said if it had happened at cruise altitude the jet could have crashed. Is there any chance that jet could have survived a bomb at cruise altitude considering it tore a hole in the cabin? I am hoping it could tbh thats why I'm kind of asking this question. Is there any chance a jet can survive if the hull is pierced at high altitude, I want to believe the aircraft structure can take such a load but tbh it is the first thing on my mind when I fly.
 
haz777
Topic Author
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Joined: Tue Oct 23, 2018 1:33 pm

Re: Explosive decompression question

Wed Oct 24, 2018 12:27 am

Francoflier,

I created this account because I often read this site as well as enjoy its many helpful and informative posts, and want reassurance that the next time I fly there is a chance that if some deranged person or terrorist decides to put a bomb in the cargo hold that there is at least a tiny chance of survival. I am afraid I cannot understand that mindset and I do not wish to even be spoken about in the same sentence as those animals
 
GalaxyFlyer
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Re: Explosive decompression question

Wed Oct 24, 2018 2:11 am

Yes, an explosion could be survivable, but a lot of luck is involved. The 707 might have survived had the crew been trained as we are today, as opposed to reverting to rapid descent training. A C-141 many moons ago had an aft door complex let go, as close to a bomb as possible to recreate. The crew, save the co-pilot lost consciousness, but the co-pilot reacted corrected and saved it.

GF
 
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zeke
Posts: 12887
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Re: Explosive decompression question

Wed Oct 24, 2018 6:08 am

haz777 wrote:
Hi, I have a question regarding explosive decompression, particularly in cases following an onboard explosion.


Sounds like a bad case of Delhi belly, it is sure to cause an explosion and rip something apart. Frequently causes discomfort to other passengers.

:roll:
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
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Balerit
Posts: 583
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Re: Explosive decompression question

Fri Nov 02, 2018 11:23 pm

Have look here at what a fuselage looks like showing the stringers and frames and in the Daallo case only a few stringers were damaged and none of the frames:
[url]
http://www.zoombd24.com//wp-content/upl ... ctures.png[/url]
Licensed Aircraft Maintenance Engineer (retired).
 
strfyr51
Posts: 3123
Joined: Tue Apr 10, 2012 5:04 pm

Re: Explosive decompression question

Sat Nov 03, 2018 6:59 pm

Francoflier wrote:
Maybe it's paranoia talking here, but does a very specific question about bombs and airplanes from a new user whose very first post it is seem suspicious to anyone else?

Actually?? Yes! Now that you mention it.
 
strfyr51
Posts: 3123
Joined: Tue Apr 10, 2012 5:04 pm

Re: Explosive decompression question

Sat Nov 03, 2018 7:11 pm

haz777 wrote:
Thanks for your answers guys, the incentive for my question was Pan Am 103 and the recent Metrojet bombing. I am trying to get my head around these disasters as it seems so horrific that such a strong jet can break apart in mid air and kill so many people. If only we could find a way to prevent these disgraceful events. Hopefully airlines will adopt the recently developed kevlar bomb bag. Thanks for your answers BoeingGuy, GalaxyFlyer and Balerit, very interesting responses. Btw Balerit, that was a Daallo airlines a321 on the way to Djibouti, I was impressed by the aircraft's structure but the captain said if it had happened at cruise altitude the jet could have crashed. Is there any chance that jet could have survived a bomb at cruise altitude considering it tore a hole in the cabin? I am hoping it could tbh thats why I'm kind of asking this question. Is there any chance a jet can survive if the hull is pierced at high altitude, I want to believe the aircraft structure can take such a load but tbh it is the first thing on my mind when I fly.

At Altitude a hole in the fuselage depending on the size is not fatal. However? it depends on Where the Hole is and the size ot it that makes the difference. I've seen 3 in my lifetime up close and personal..
Nove of the 3 breached the main longitudinal spars. but they did damage circumfrentail stringers. so the airplane didn't come apart.. I ssrillhold the Theory that TWA's center fuel tank hadn't a damn thing to DO with that crash. I still submit that a Navy Missle went through that fuselage and that WHOLE deal was a cover-up. all of this Center fuel tank Inerting stuff is a bunch of Hooie !! Tea was almost Broke and after that incident bought a bunch of Brand NEW B757's Are you kidding me??
 
Yikes!
Posts: 300
Joined: Sat Oct 13, 2001 4:51 pm

Re: Explosive decompression question

Mon Nov 12, 2018 5:08 am

Francoflier wrote:
Maybe it's paranoia talking here, but does a very specific question about bombs and airplanes from a new user whose very first post it is seem suspicious to anyone else?


This is exactly the type of topic that should not be discussed nor commented about here.

Have posters learned nothing since prior to 9-11 where some believe THIS FORUM provided information to the 9-11 hijackers in advance of their heinous actions?
 
WKTaylor
Posts: 33
Joined: Mon Jul 25, 2016 9:36 pm

Re: Explosive decompression question

Mon Nov 12, 2018 5:46 pm

No much 'out-there', RE sudden aircraft decompression: design philosophy/info/etc.

Interesting engineering perspective in 'SAE AIR5661 Compartment Decompression Analysis'
 
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CALTECH
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Re: Explosive decompression question

Wed Nov 14, 2018 4:56 pm

The gun is a precious Symbol of Freedom
Criminals are the deadly cancer on American society
Those who believe otherwise are consumed by an ideology
That is impervious to evidence of tyrants who disarm their citizens
 
WIederling
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Re: Explosive decompression question

Thu Nov 15, 2018 12:02 pm

Yikes! wrote:
Francoflier wrote:
Maybe it's paranoia talking here, but does a very specific question about bombs and airplanes from a new user whose very first post it is seem suspicious to anyone else?


This is exactly the type of topic that should not be discussed nor commented about here.

Have posters learned nothing since prior to 9-11 where some believe THIS FORUM provided information to the 9-11 hijackers in advance of their heinous actions?


Quick!

Duck and cover:
Image
https://www.hastac.org/sites/default/fi ... k=mHRcH2u2

explosive decompression is a follow up result.
The primary explosion breaches the pressurized hull.
---> explosively depressurizes.

similar effects from losing a cargo door
( United Airlines Flight 811, Turkish Airlines Flight 981)
or windows
or structural failure like the Hawaiian Cabriolet.
Murphy is an optimist
 
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TSS
Posts: 2725
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Re: Explosive decompression question

Thu Nov 15, 2018 1:51 pm

Yikes! wrote:
Francoflier wrote:
Maybe it's paranoia talking here, but does a very specific question about bombs and airplanes from a new user whose very first post it is seem suspicious to anyone else?


This is exactly the type of topic that should not be discussed nor commented about here.

Have posters learned nothing since prior to 9-11 where some believe THIS FORUM provided information to the 9-11 hijackers in advance of their heinous actions?

I suspect the flight school the hijackers attended in Florida provided them with far more information than this forum did or ever could.
Able to kill active threads stone dead with a single post!
 
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SuseJ772
Posts: 777
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Re: Explosive decompression question

Sat Nov 24, 2018 2:21 am

Yikes! wrote:
Have posters learned nothing since prior to 9-11 where some believe THIS FORUM provided information to the 9-11 hijackers in advance of their heinous actions?


Where was this site ever implicated in providing knowledge to the 9-11 hijackers. I never saw that nor can find any evidence currently about it.
Currently at PIE, requesting FWA >> >>
 
Yikes!
Posts: 300
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Re: Explosive decompression question

Mon Dec 03, 2018 3:15 am

Ignorance is bliss. This is a topic that should not be discussed here.
 
Yikes!
Posts: 300
Joined: Sat Oct 13, 2001 4:51 pm

Re: Explosive decompression question

Thu Dec 06, 2018 3:45 am

SuseJ772 wrote:
Yikes! wrote:
Have posters learned nothing since prior to 9-11 where some believe THIS FORUM provided information to the 9-11 hijackers in advance of their heinous actions?


Where was this site ever implicated in providing knowledge to the 9-11 hijackers. I never saw that nor can find any evidence currently about it.


Search posts from 1997-2000. They're there.
 
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TSS
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Re: Explosive decompression question

Thu Dec 06, 2018 4:42 pm

Yikes! wrote:
SuseJ772 wrote:
Yikes! wrote:
Have posters learned nothing since prior to 9-11 where some believe THIS FORUM provided information to the 9-11 hijackers in advance of their heinous actions?


Where was this site ever implicated in providing knowledge to the 9-11 hijackers. I never saw that nor can find any evidence currently about it.


Search posts from 1997-2000. They're there.

SuseJ772, I think I know what Yikes! is talking about. Some time prior to 9/11, a poster here asked what would happen if you flew a modern airliner into a skyscraper. I've never read that original thread, so I don't know if that question was the genesis of a thread unto itself or if it came up in a thread discussing the incident when a WWII-era bomber crashed into the Empire State Building. Either way, the poster who originally asked that question was interviewed and cleared by the FBI post-9/11, or so he said in a thread years later when someone brought up the subject of his eerie yet apparently entirely coincidental prediction of the events of 9/11.

Good luck searching for either thread if you choose to do so. If memory serves, the title of the later thread was something along the lines of "Whatever happened to the poster who predicted 9/11?" and it may have appeared in the Non-Aviation forum.
Able to kill active threads stone dead with a single post!
 
747Whale
Posts: 121
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Re: Explosive decompression question

Sat Dec 08, 2018 6:41 am

Loss of pressure is the primary threat in the case of an explosive depressurization; I say "explosive" not to invoke the use of explosives, but in reference to a rapid, violent loss of pressure. It's typically due to some form of structural failure which could be anything from a bomb to a door opening, to a loss of a portion of the structure (think the Hawaiian Airlines convertible 737 --AQ243).

A structural failure can do minimal damage, or considerable; it really depends on what has failed. Consider the depressurization of JAL123, which resulted in the loss of the vertical stabilizer, hydraulics, and much of the control capability of the aircraft. In that case, the pressurization wasn't the problem. In other cases, such as a high altitude loss of pressurization, the time of useful consciousness may be measured in seconds; this applies specifically to the crew, which will also be battling sinus and other physiological problems, as well as the loss of air pressure.

The specifics of a bomb on a flight should not be discussed here; it's safety sensitive information. Each crewmember is aware of a designated location on a flight which represents the point of least damage, should an explosive device be detonated there. Conversely, the point of maximum damage has too many variables and is not taught, nor discussed; it's a circular discussion.

Rest assured, however, that in the event of air piracy, response on board has changed from what it once was. There was a time when crewmembers were instructed to avoid confrontation and to meet demands to protect the safety of the flight. Today, crewmembers are responsible to use every means at their disposal, up to and including destruction of the aircraft, to prevent its use as a weapon, and passengers are far more inclined to respond aggressively to prevent a hijacker or terrorist from getting to that point. It's not hard to find reports in the news of flights that get turned around because of an off-hand comment, a disturbance, or a suspicion, and passengers are much more likely to report.

In the US, an elevated air marshall presence has been implemented since 09/11, as well as numerous security measures which are both visible to the public, and many which are not. Cockpit doors are strengthened. Some crewmembers are armed.

As to the original question, why would a structure experience damage beyond the original blast, think of a balloon. An aircraft, when pressurized, is much like a balloon. A balloon with very low pressure, barely inflated, might take a pin prick easily, and slowly deflate, while a stressed balloon inflated to capacity will often rip to pieces. An inflated structure may act somewhat the same way, depending on the damage and where it occurs.

It should also be noted that hollywood promotes some wild ideas about holes in the structure. It's often seen in a movie where a window gets blown out, and the aircraft has an explosive depressurization. This doesn't typically occur. The bleed air system pumps air from the engine compressor sections into the structure continuously to pressurize the aircraft; this air has to escape somewhere, and to regulate pressurization, an "outflow" valve, or valves are used; these open and close in varying degrees to regulate the amount of air released. In the case of a small hole, such as a passenger window, in a large airplane like a 747, the effect will hardly be noticed as the outflow valves are each bigger than passenger windows; the valves would simply close more. There would be a fair amount of air escaping and flowing out the window; typically at altitude the airplane is pressurized at about 7 lbs/square inch. At that level, a 10 X 6 inch window has 60 square inches of area, and 420 lbs of force. Anything that gets between the window frame and the airstream, if the window fails, will face the same force, and a lot of airflow; a continuous flowing force.

I have had several rapid depressurizations over the years, the last one of which was some years ago and involved the separation of the pilot side forward windscreen. It was very rapid and took the. aircraft flight manual with it, a checklist, the top of the glareshield, some of the interior, and the headset. It was quite loud. The cause was a structural failure of the pane itself. Another case was a failed door seal. Recently I had a bleed valve problem, and simply secured that bleed valve in accordance with the checklist. I have had airplanes fail to pressurize, which is fairly straight forward.

In the off chance someone posting these questions is remotely considering doing something stupid, is is looking for information to achieve that end, know that your odds are very slim and the probability very high that it won't work well in your favor. A lot of very dedicated people with very high motivation are working tirelessly to ensure that's so. Reconsider and find another line of work.

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