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Southwest Airlines flight experiences engine explosion but makes a safe landing in Philadelphia... 5
- Thread starter JohnRBaker
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LittleInch
Petroleum
Sparweb,
I'll take your word for it, but I am surprised that such a relatively large volume like a 737 with a relatively small differential pressure ( the word guage is not required for differential pressure, but I'm being picky) exiting through a relatively small orifice such as a window can reduce the pressure by 50% in one second. Any sort of a calculation or graph you can share?
Sure we're not talking probably more than 15 seconds before the flow becomes quite low, but that just sounds too fast to me.
I was in a pressurized aircraft one time which purposely de-compressed quite rapidly ( about 5 seconds) at about 18,000 ft ( we were jumping out) and the air inside turned opaque due to the water vapour dropping out to the extent you couldn't see your hand in front of your face. I'm surprised that wasn't mentioned by people, but maybe my situation was different.
I always sit with my seat belt on...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
I'll take your word for it, but I am surprised that such a relatively large volume like a 737 with a relatively small differential pressure ( the word guage is not required for differential pressure, but I'm being picky) exiting through a relatively small orifice such as a window can reduce the pressure by 50% in one second. Any sort of a calculation or graph you can share?
Sure we're not talking probably more than 15 seconds before the flow becomes quite low, but that just sounds too fast to me.
I was in a pressurized aircraft one time which purposely de-compressed quite rapidly ( about 5 seconds) at about 18,000 ft ( we were jumping out) and the air inside turned opaque due to the water vapour dropping out to the extent you couldn't see your hand in front of your face. I'm surprised that wasn't mentioned by people, but maybe my situation was different.
I always sit with my seat belt on...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
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1
- #23
The feel good part of the story.
"Spartan 5,
The person reported dead was a man who had a heart attack , the woman sucked/blown into the window is in critical condition.
B.E. "
All the news reports seem to say that it was the woman sucked out the window who died, I haven't seen mention of a heart attack victim, but who knows? These things are very dynamic.
As to the whole suck/blow thing, should we now refer to the wind sucking instead of blowing? The answer my friend, is sucking in the wind....
The person reported dead was a man who had a heart attack , the woman sucked/blown into the window is in critical condition.
B.E. "
All the news reports seem to say that it was the woman sucked out the window who died, I haven't seen mention of a heart attack victim, but who knows? These things are very dynamic.
As to the whole suck/blow thing, should we now refer to the wind sucking instead of blowing? The answer my friend, is sucking in the wind....
ornerynorsk
Industrial
Off point a little bit, but those of us who live on or near the prairie know that, indeed, the wind does suck.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
TehMightyEngineer
Structural
A public service announcement; the above is not the proper way to wear an oxygen mask.
Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
LittleInch
Petroleum
This report is fairly clear it was unfortunately the lady partially sucked / blown out of the aircraft who has died. Given the report says people were performing CPR on her, she may also have suffered a heart attack as a result of injuries or the event and therefore confused the issue.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
EdStainless
Materials
I doubt that the air fogged in this plane on de-presurization, as it is low humidity inside.
We have to remember that this is the most common plane and engine in the world.
There are more flight hours on this combination than any other, and it is extremely reliable.
This is really an outlier event.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
We have to remember that this is the most common plane and engine in the world.
There are more flight hours on this combination than any other, and it is extremely reliable.
This is really an outlier event.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube
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1
- #31
LittleInch,
Your surprise is understandable. I shared the same feeling as you, once.
The simplified form of the calculation involves forcing the known density of cabin air through the area of the window at the local speed of sound. There is a discharge coefficient to consider but the size/shape/edge of the hole in this case is so clean that I'd say it's pretty close to 1; say 90% if I'm throwing darts. The air density with a cabin altitude of 8000 feet is about 1 kg/cubic meter, and the speed of sound is about 340 meters per second. Note that speed of sound that matters in this case is the speed inside the cabin.
From that I get about 37 kilograms per second flow out the window. The total volume of the entire fuselage (a cylinder 21m long and 1.9m diameter) is 230 cubic meters. About 25% of the volume is filled with stuff (seats baggage people etc) and another 15% with wing carry-through structure and flooring, so there is about 138 left of air volume. The density being about 1kg/cu.m, then the air mass is also 138 kilograms.
Subtract 37kg from 138kg and you get 101kg of air left in the cabin. 101/138 = 73%
Isentropic flow dictates the change in pressure is NOT 78%. It's actually (0.73)^1.4 so the final pressure ratio is 0.64.
So the absolute pressure in the cabin would drop by about 35% (4.2 psi) in the first second. Deducted from the GAUGE pressure of 7.4 psi and yeah, it's about 50% the relative pressure.
Depressurizing by pushing buttons in the cockpit is very gentle in comparison. In most planes, pushing DEPRESS = A valve that is already open, is told to open more.
STF
Your surprise is understandable. I shared the same feeling as you, once.
The simplified form of the calculation involves forcing the known density of cabin air through the area of the window at the local speed of sound. There is a discharge coefficient to consider but the size/shape/edge of the hole in this case is so clean that I'd say it's pretty close to 1; say 90% if I'm throwing darts. The air density with a cabin altitude of 8000 feet is about 1 kg/cubic meter, and the speed of sound is about 340 meters per second. Note that speed of sound that matters in this case is the speed inside the cabin.
From that I get about 37 kilograms per second flow out the window. The total volume of the entire fuselage (a cylinder 21m long and 1.9m diameter) is 230 cubic meters. About 25% of the volume is filled with stuff (seats baggage people etc) and another 15% with wing carry-through structure and flooring, so there is about 138 left of air volume. The density being about 1kg/cu.m, then the air mass is also 138 kilograms.
Subtract 37kg from 138kg and you get 101kg of air left in the cabin. 101/138 = 73%
Isentropic flow dictates the change in pressure is NOT 78%. It's actually (0.73)^1.4 so the final pressure ratio is 0.64.
So the absolute pressure in the cabin would drop by about 35% (4.2 psi) in the first second. Deducted from the GAUGE pressure of 7.4 psi and yeah, it's about 50% the relative pressure.
Depressurizing by pushing buttons in the cockpit is very gentle in comparison. In most planes, pushing DEPRESS = A valve that is already open, is told to open more.
STF
Just following on EdStainless theme.
The reliability of the modern jet engine is such that most airline captains in a life time career never experience an engine failure in flight for real.
But with thousands in the air around the world a failure is inevitable because stuff happens. That is one of the reason that airline captains get paid the big money. You can have all the systems, procedures , checks etc but things still go wrong for various reasons and its up to the captain to sort out the mess and bring it home safely.
The Captain in this case did a good job, but that is what she is there for and paid to do.
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"
The reliability of the modern jet engine is such that most airline captains in a life time career never experience an engine failure in flight for real.
But with thousands in the air around the world a failure is inevitable because stuff happens. That is one of the reason that airline captains get paid the big money. You can have all the systems, procedures , checks etc but things still go wrong for various reasons and its up to the captain to sort out the mess and bring it home safely.
The Captain in this case did a good job, but that is what she is there for and paid to do.
Regards
Ashtree
"Any water can be made potable if you filter it through enough money"
Regarding the oxygen masks...
In my experience the pre-flight demonstration usually shows the fitting of the mask in a fraction of a second and I don't ever remember the attendant actually "wearing" the mask - instead simply holding it in front of their face with one hand and stretching the elastic with the other.
Now, I assumed that they fit over the mouth and nose and everyone else knows that, but in the pictures NO-ONE is wearing them like that, which is wrong.
To me that suggests that the design of the mask isn't good enough. It should be absolutely obvious how a piece of emergency equipment that you've never handled before (and are doing so in a very distressing scenario) sits on your face.
Normally breathing masks are triangular and fit easily over the mouth and nose, but in the pictures they look more conical and, frankly, on the small side.
I'm reminded of a documentary about the Millennium Dome in London which originally had an exhibition about the human body in it.
In trials of one of the interactive exhibits, the public used the items provided in a way that the designer hadn't envisaged and he got quite upset that, with no instructions, the public didn't behave the way he had designed it to be used. I'm surprised that, considering all the work that the airline industry do to combat emergency situations I'd never seen this before.
"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams
In my experience the pre-flight demonstration usually shows the fitting of the mask in a fraction of a second and I don't ever remember the attendant actually "wearing" the mask - instead simply holding it in front of their face with one hand and stretching the elastic with the other.
Now, I assumed that they fit over the mouth and nose and everyone else knows that, but in the pictures NO-ONE is wearing them like that, which is wrong.
To me that suggests that the design of the mask isn't good enough. It should be absolutely obvious how a piece of emergency equipment that you've never handled before (and are doing so in a very distressing scenario) sits on your face.
Normally breathing masks are triangular and fit easily over the mouth and nose, but in the pictures they look more conical and, frankly, on the small side.
I'm reminded of a documentary about the Millennium Dome in London which originally had an exhibition about the human body in it.
In trials of one of the interactive exhibits, the public used the items provided in a way that the designer hadn't envisaged and he got quite upset that, with no instructions, the public didn't behave the way he had designed it to be used. I'm surprised that, considering all the work that the airline industry do to combat emergency situations I'd never seen this before.
"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams
LittleInch
Petroleum
We don't know at what stage that photo was taken. The oxygen supply for the passengers is limited to between 5 to 10 minutes only - basically just long enough to allow the plane to descend to circa 10,000 ft when you don't need Oxygen long term. However until someone from the crew tells you to take it off then I would imagine most people are somewhat reluctant to completely remove it.
Normally the pilots first aim on de-pressurisation is to get the plane down to low level PDQ, i.e. slows down, full flaps, air brakes and sometimes wheels down and just heads down. A lot of passengers assume this is the precursor to a crash so get very worried, but it's all part of the drill.
I did see a flight radar plot on one website but can't find it now, but it descended pretty rapidly - probably in the realms of 5- 8,000 ft/minute. That's a pretty good dive.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Normally the pilots first aim on de-pressurisation is to get the plane down to low level PDQ, i.e. slows down, full flaps, air brakes and sometimes wheels down and just heads down. A lot of passengers assume this is the precursor to a crash so get very worried, but it's all part of the drill.
I did see a flight radar plot on one website but can't find it now, but it descended pretty rapidly - probably in the realms of 5- 8,000 ft/minute. That's a pretty good dive.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
From Canadian Press, "Last year, engine maker CFM International and FAA instructed airlines to make ultrasonic inspections of fan blades of engines like those on the Southwest jet.
PHILADELPHIA — A preliminary examination of the blown jet engine of the Southwest Airlines plane that set off a terrifying chain of events and left a businesswoman hanging half outside a shattered window showed evidence of “metal fatigue,” according to the National Transportation Safety Board."
Dik
PHILADELPHIA — A preliminary examination of the blown jet engine of the Southwest Airlines plane that set off a terrifying chain of events and left a businesswoman hanging half outside a shattered window showed evidence of “metal fatigue,” according to the National Transportation Safety Board."
Dik
I believe the engine on the SW flight did not have the number of cycles that the bulletin set. If I'm remembering right the bulletin was for 15,000 cycles and the SW flight engines were at 10,000. It looks like the FAA is recommending all CFM engines in 737s get a closer inspection of the fan blades. Apparently CFM engines are used in Airbus aircraft as well; I wonder if the reason this has hit 737s twice is the asymmetry of the inlet providing slightly more cyclic loading on the blades.
Of all the US airlines, SW seems like the least likely to have oversight problems. They fly only one series of planes so their mechanics and inspectors get much higher familiarity with the aircraft than other airlines. In addition, they seem to encourage bottom-up suggestions for improvement, rather than corporate board-room white-board edicts.
Of all the US airlines, SW seems like the least likely to have oversight problems. They fly only one series of planes so their mechanics and inspectors get much higher familiarity with the aircraft than other airlines. In addition, they seem to encourage bottom-up suggestions for improvement, rather than corporate board-room white-board edicts.
- Thread starter
- #38
JohnRBaker
Mechanical
In all of the miles that I've flown, something like 5 million over about 45 years, I've only experienced a single engine failure. This was back in the late 70's flying out of Oakland, CA, on a United 727, heading to Chicago. Something happened about two minutes after takeoff and the first indication that there was something wrong was that the plane never climbed out to cruising altitude but rather started to make a very large circle. About that time the pilot came on the PA and announced that there was a problem that required that he shutdown one of three engines and that we were being directed back to, in this case, San Francisco Airport (later we learned it was because there were more flights there leaving for Chicago that the passengers could be re-booked on and I assume also because the San Francisco Airport probably had a better equipped maintenance facility than did the Oakland Airport). Note that there were no indications that whatever the problem was that it caused any significant mechanical damage as there were no vibrations or unusual sounds, just one of the engines shutting-down, so it may have been something that while it required them to shutdown the engine didn't do any significant damage, or at least anything that could be felt or heard from inside the plane.
Now I did SEE a more dramatic one happen from the ground. This was in the early 70's and I was in Dallas and was waiting for a flight home to Saginaw. I was in the terminal watching planes take off and this American Airlines 727 had just applied full throttle to start it's take-off roll when the center engine blew. A big puff of black smoke came out of the engine and the pilots immediately aborted the take-off with no apparent problems other than seeing a bunch of airport emergency vehicles leave their stations and follow the plane as it taxied back to the terminal. I couldn't see where it finally parked so I didn't see any of the aftermath of what happened, and of course, the LAST place that you will ever hear about any sort of airplane incident in while waiting in an airport ;-)
John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:
The secret of life is not finding someone to live with
It's finding someone you can't live without
Now I did SEE a more dramatic one happen from the ground. This was in the early 70's and I was in Dallas and was waiting for a flight home to Saginaw. I was in the terminal watching planes take off and this American Airlines 727 had just applied full throttle to start it's take-off roll when the center engine blew. A big puff of black smoke came out of the engine and the pilots immediately aborted the take-off with no apparent problems other than seeing a bunch of airport emergency vehicles leave their stations and follow the plane as it taxied back to the terminal. I couldn't see where it finally parked so I didn't see any of the aftermath of what happened, and of course, the LAST place that you will ever hear about any sort of airplane incident in while waiting in an airport ;-)
John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:
The secret of life is not finding someone to live with
It's finding someone you can't live without
I probably doesn't matter very much that the masks weren't covering people noses - the aim with these things is to oxygen-enrich the air that people are breathing, not to exclude cabin air completely. As long as people are breathing through their mouths (and, in a scary situation, it's hard not to), they'll get the benefit. If you provide shaped masks, then you have to make passengers put them on the right way up, and find a way to make them fit every shape and size of face from baby on up.
The masks provided for the flight crew are a different story: These do need to exclude fumes - but "one size to fit all" is easier there since they don't employ two-year-olds as crew members (although the older I get, the more it starts to look as if they do).
A.
The masks provided for the flight crew are a different story: These do need to exclude fumes - but "one size to fit all" is easier there since they don't employ two-year-olds as crew members (although the older I get, the more it starts to look as if they do).
A.
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