What surprised me is how far back it was where the window was damaged, as seen in the this photo of the plane:



This would indicate that perhaps it was not the main turbine that failed or at least it was not the only part of the engine that was damaged. Generally speaking, if a problem occurs with the main turbine, like a blade breaking or coming loose, they will fly directly outward in a radial direction, which is why there are NO windows directly inline with the main turbine, which can be seen in the photo below between the "w" and "e" in the "Southwest" logo on the side of the plane.



In place of the missing window, the fuselage is wrapped with Kevlar.

John R. Baker, P.E. (ret)
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According to your diagram, the missing window lines up with the wing door. Sort of a secondary question is how far back does the engine go from the wing, and does the back of the engine line up with that window?

If so, does that indicate something from the rear of the engine, like a end turbine blade?
Not as likely as a forward turbine blade, but still possible.

One dead after being partially sucked out of the window. Keep that seat belt on, folks.

More likely scenario is that a piece of the engine nacelle broke and went over the top of the wing on a curved trajectory. Not a good idea to choose a window seat on SW!

Walt

The emergency doors over the wings are further back than where the missing window is located, and the engine is actually mounted such that most of it is not under the wing but rather ahead of it. And the actual 'jet engine' only occupies about one-half the length of the engine housing and that's mostly in the rear half. The front half is where the so-called 'fan' is located and it's that part of the engine where the largest blades are found and why there is that Kevlar shield around the fuselage.

As for SW and this particular type of engine, they're not the only airline using them. In fact, my wife and I are flying home tomorrow morning, from Detroit back to SoCal, on American Airlines. And we will be flying in a Boeing 737-800, the same model as the SW jet involved in today's incident, and they are using the same engines, the CFM56-7B.

John R. Baker, P.E. (ret)
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Irvine, CA
Siemens PLM:
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Blown or pushed, not sucked. No one says a champagne cork is sucked from the bottle.

pprune.org is showing photos that indicate the fan is generally intact, but the last one, in Aug 2016, was attributed to a single fan blade separation. Apparently the damage to a woman passenger was from shrapnel penetrating the plane. Reports are that some passengers were trying to block the hole from the missing window.

Previous accident analysis http://aerossurance.com/safety-management/uncontai...

For reference purposes, here's a cross-section of a CFM56-7B engine showing how it's positioned inside the engine housing:

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

Correction: The Southwest airliner involved in today's incident was a Boeing 737-700, not an -800. The -700 is about 20 feet shorter than an -800.

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

JohnR: Possible over-pressure of the cowl anti-ice system?

3DDave: No one says that liquid is being blown up a straw either *shrug*

That's because an external system is acting to locally lower the pressure on the soda straw. Since the pressure outside the plane at any altitude is essentially no different whether the plane is there or not there's no suction. It's pressurization inside the plane that does all the pushing. In addition, once the plane pressurization is relieved, so is the push.

The same thoughts about over pressure of deicing were brought up the last time this happened. But it was still a fan blade, separated at the root that got chucked forward and then out. In March of this year the French/Europeans issued an order to inspect all fan blades for this engine type within the next 9 months.

3DDave I get it now. The next time I am draining an aquarium via gravity and a fish is suddenly drawn into the orifice when it swims too close to it, I'll be sure to explain to everyone how it just got blown out of the tank. Thanks for setting me straight

Push or pull, however you want to look at it, it is the differential that matters.

The picture of the actual plane shows that the missing window is the fourth one back from the exit door over the wing.

I think John was referring to the as-designed skipped window, as opposed to the broken window.

TTFN (ta ta for now)
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The missing window look like it is behind the wing. If there is a place engine parts are supposed to impact the fuselage, they missed.

Quote (Hokie66)

If there is a place engine parts are supposed to impact the fuselage, they missed.

I'm sure part of the NTSB's findings will include suggested modifications to the Rapid Unplanned Engine Disassembly Component Collection Structure (RUEDCCS) of all future airliner designs.

Ok maybe not.

Wonder if what struck the window was a chunk of cowling.. My suspicion is that any part of the rotating assembly would leave the engine with enough force that it would impact the airframe in plane with where it had just been, or maybe just a little aft. A big piece of cowling would have its trajectory and relative speed influenced by airflow a lot more.

Jet engines have a Kevlar containment shroud inside the nacelle (cowling). In the photo the nacelle is now missing and the yellow containment shroud is visible. Propeller planes have the protection only on the fuselage for protection against detached blades. I have seen the specialized loom that is used to weave the fabric that is used for the shroud. The fabric is wound onto a spool that has the same barrel shape as the completed shroud. Test video here:https://www.youtube.com/watch?v=j973645y5AA

When a fan blade separates it is under both radial load from rotation and axial load from thrust production. It was theorized that there is a combination of the two that sends the blade forward from the fan-disk and out through the inlet. Others think that other blades just bash the loose one out the front. There is often extra damage to the fan and not enough fragments of the inlet to be certain about those few milliseconds. The blades aren't especially dense for the projected area they have and I expect they can deflect as they tear through the cowling. The last time a blade exited it left a considerable dent about mid-chord, just below a window, leading to a smaller leak. I think it was the blade as nothing in the inlet seems substantial enough to do the damage and that it just happened to shatter the window in an unfortunate trajectory.

There was an incident some years ago where a fan blade walked forwards out of the fan disk due to a resonant condition; This was in spite of a retainer and an estimated 113kips radial load. Since it was out-of-plane with the disk it lined up with a window when it went through the engine case; a sleeping, unbelted passenger was extruded out the window opening. I believe it was an 8.7 psi differential with a 16 * 10.6 window, so the passengers struggling to hold him needed to hold with nearly 1500 lbf; they were unsuccessful and I believe his body was never found. https://www.fss.aero/accident-reports/look.php?rep... Much more damage was done to the aircraft as the entire fan disk departed due to imbalance and numerous blades severed controls and fuel tank.

A person's chance is much better if they aren't a cork. https://en.wikipedia.org/wiki/British_Airways_Flig...

Although it seems pretty obvious who was fatally injured, it's not necessarily true that the passenger partially sucked out the window is the person who died, since they were pulled back inside and (presumably) offered oxygen. I will wait for clarification from the airline or NTSB, rather than jump to that conclusion. But of course it's pretty likely that's who it was. Also not clear at the moment is what led to the passenger's fatal injuries. If the assumption above is actually correct, there is still the question of whether debris or decompression dealt the fatal blow.

I once did a detailed decompression analysis on a jetliner, and I think it is safe to say that the decompression in a 737 fuselage, escaping through a window, would take just a few seconds to completely exhaust the cabin pressure down to the ambient pressure, but that's probably obvious to anyone. At 32,000 feet altitude, the atmospheric pressure is 4.4 psi, absolute (30 kPa,abs). The cabin differential pressure in a 737 is about 7.5 psi,gauge. The pressure differential would drop to about 50% in the first second of decompression, if the window was ruptured but unobstructed.

It's a pretty horrible event no matter where you sit, but I would not have expected the debris to take out a window that far aft from the engine nacelle.
There is design guidance from the FAA on this matter. Some of you may find it informative: FAA Advisory Circular 20-128A, Design Considerations for Minimizing Hazards Caused by Uncontained Turbine Engine and Auxiliary Power Unit Rotor and Fan Blade Failures.

Also studied by the US Navy: DOT/FAA/AR-04/16 Uncontained Engine Debris Analysis / Damage Assessment Model.

Note the Spread Angle ranges presented in Table 3-2 of the Navy report. The victim window in the SW 737 is at the extreme aft range of the predicted debris spread angle. It makes me wonder if some other event has occurred as a result of, or in conjunction with, this engine failure. The possibility is very small: Occam's razor says that it was the fan debris that ruptured the window, of course.

STF

A photo of NTSB examining the engine apparently shows a gap in the fan blades.

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.

The feel good part of the story.

http://www.foxnews.com/us/2018/04/18/former-ace-na...

"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....

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.

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 https://www.facebook.com/AmericanConcrete/

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.

https://www.theguardian.com/business/2018/apr/17/p...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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

This from a report this morning. "Passenger Jennifer Riordan, a Wells Fargo bank executive from Albuquerque, N.M., died from her injuries."
B.E.

You are judged not by what you know, but by what you can do.

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

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"

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

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.

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

Inspection records will be closely scrutinized for SW airlines. I hope an inspection was not missed or done poorly.

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.

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)
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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.

Quote (Spartan5)

No one says that liquid is being blown up a straw either *shrug*

As I understand, it gets pushed up...

Dik

zeus: I'm no expert on this but being a pilot I have read a fair bit about oxygen systems and such from my training. My understanding is that full facial coverage of the mask is important at high altitudes as the partial pressure of oxygen in your lungs is reduced. Thus, the mask needs to pressurize to some degree. This is in relation to pilot masks though, so I don't know if passenger masks have this function of providing positive pressure. However, I do know that partial coverage masks or cannulas are not to be used at higher altitude due to the fact that a few breaths not through the oxygen system can incapacitate a person (among other concerns like smoke like you indicated). For example, at 30,000 to 40,000 feet you have a minute down to fifteen seconds of effective consciousness, and as you get hypoxic you'll quickly loose all sense that something is amiss.

I'll fully admit that this risk could be a non-issue; perhaps it is fine to just wear it over the mouth for the few minutes the plane is in a dive to lower altitude. It appears to have turned out more or less okay for most passengers.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries https://www.facebook.com/AmericanConcrete/

Flight data shows that the aircraft descended from over 30,000 feet to 13,000 feet in five minutes. After that five minutes, there was no reason to use the oxygen masks any further although there may have been a side benefit to continued use - to occupy some passengers and to muffle those passengers that were crying and screaming. "Oxygen production cannot be shut off once a mask is pulled, and oxygen production typically lasts at least 15 minutes,"

Not putting the mask over the nose would be akin to snorkeling without a snorkel.

"Passenger oxygen masks cannot deliver enough oxygen for sustained periods at high altitudes. This is why the flight crew needs to place the aircraft in a controlled emergency descent to a lower altitude where it is possible to breathe without emergency oxygen."

Quote (https://en.wikipedia.org/wiki/Emergency_oxygen_sys...)

Wikiedia

" . . . place the mask over your nose and mouth and continue to breathe normally" is how I have always heard the instructions. Looks like the folks in the pic are placing them over their mouth and chin. Fitting each passenger for a respirator-class fit is hardly practical, so I have always assumed the fit is not critical to the function in typical usage scenarios (in contrast to typical respirator applications).

The oxygen generators work from a chemical reaction, sort of like an air bag or flare, so once they're on they will go to exhaustion. Also may account for passenger accounts of smoke in the cabin despite there being no obvious fire in the accident.

The chemical oxygen generators get very hot.

Quote (www.skybrary.aero)

The reaction of the chemicals produces a significant amount of heat and the generator canister in the overhead compartment can reach temperatures above 250°C. The effect of this is that an often-unanticipated burning smell may become apparent in the passenger cabin and cause alarm.

STF

https://flightaware.com/live/flight/SWA1380/histor...

Flightaware shows 3,743 feet/minute descent.

STF

There is only a tiny hose to the mask so it cannot possibly supply full breathing flow rates. That is the purpose of the inflatable bag, to store your exhaled breath which has been oxygen enriched, to be used again. But they do say that it is normal for the bag not to inflate. It would not inflate if the mask does not seal well.

A minimum oxygen flow of 2.5 liters per minute is what is required at 30000 feet. That's a large soda bottle in a minute. that tiny hose is more than capable of delivering that .
B.E.

You are judged not by what you know, but by what you can do.

A shallow breath is more than one liter. Say that under stress a persons respiration rate is one breath per second. That is 60 liters per minute. And so my point is that 2.5 << 60.

Quote (berkshire)

A minimum oxygen flow of 2.5 liters per minute is what is required at 30000 feet. That's a large soda bottle in a minute. that tiny hose is more than capable of delivering that .

Without looking I think 2.5 ltr / min might be FAR 23 aircraft, the Part 25 freighters all get 4 ltr / min for their passengers (legally supernumeraries). The typical output of the O2 generators is 4 ltr/ min for the first 2 minutes then tapering off to 0 by 7 minute mark, there some that last for 14 mintues but I think that is for the aircraft that fly one of those routes with extended distance over 10,000 ft plus ground level (Asian to Europe typically).

Quote (Compositepro)

A shallow breath is more than one liter. Say that under stress a persons respiration rate is one breath per second. That is 60 liters per minute. And so my point is that 2.5 << 60.

Tidal volume goes way down with rapid breathing, buried in an FAA doc on oxygen systems is a conclusion that it pretty much all comes out in the wash, total volume consumed is little changed. The bag only holds O2 that has flowed from the source while you are breathing out.


The bit that makes me think what if this had been a Boeing 787 on 330 minute EDTO (that's 5 & half hours from the nearest landing point) that had lost the window, would they have all frozen to death or be driven mad by the sound. There is a route coming from Perth, Australia to South America that goes straight over the south pole, it could be many hours before the aircraft could find air temperature above 0 deg C.

@TME

For the flight crew, what you say is spot on. The doctor at aeromed school 30+ years ago used to call anything over 33,000 ft 'bandit country' - even 100% oxygen doesn't give you an alveolar PPO2 equivalent to 10,000 ft (the killer is actually the constant 50 mbar PPCO2 which starts to dominate everything else). For sustained flight at cabin altitudes between 30,000 ft and 50,000 ft, you use a pressure demand regulator, work hard to breathe out, try not to say too much and try not to spend too long there (I think my B Cat ticket restricted me to 20 min above 30,000). Getting the mask to fit and seal well enough to hold that pressure is (literally) a pain - I had to shave my beard off before we went into the chamber.

To be honest, I haven't seen a really modern airliner flight crew mask - but the ones I worked with in the 80s provided 100% oxygen at ambient rather than pressure breathing. I think that's one of the reasons commercial jets don't fly any higher than they do - if there's a problem, you can still get below 30,000 ft before becoming too hypoxic.

For the passengers, the requirement is different: The emergency oxygen supply just needs to be sufficient to sustain life during the descent, there being no real need for rational thinking, peripheral vision* or physical coordination - so a yoghurt pot with a mesh vent at the bottom and a plastic bag economiser, all fed from an ambient pressure constant flow, is ample. Even with a perfect fit, you'll still get a lot of dilution through the mesh on the front of the mask. That dilution is deliberate: It's how you persuade people to keep the masks on without feeling they're being suffocated while there's only limited flow coming through the hose.

*The hypoxic loss of peripheral vision might even be beneficial - during an emergency descent, so many bits start sticking out the wings to keep the airspeed under control that it looks like the aircraft is about to fall to bits.

A.

and to help, CO2 is a respiratory stimulant...

Dik

FAA issues emergency airworthiness directive requiring ultrasonic inspection of fan blades within 20 days for all CFM56-7B engines having more than 30,000 flight cycles:
http://rgl.faa.gov/Regulatory_and_Guidance_Library...

It was recently reported that the engine manufacturer had recommended an accelerated UT inspection recommendation based on the 2016 incident with SW. The FAA, including SW or other airlines with similar engines, did not act upon this recommendation. So much for safety versus cost with major airlines, including SW.

By the FAA issuing something different than the manufacturer's recommendation, they are exposing themselves to major liability, IMHO.

Dik

Zeus: Fantastic details. Here's my understanding what a modern flight crew mask looks like:



That makes sense about the passengers that they're not too worried about keeping them at tip-top shape, but rather just keeping them conscious and alive.

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries https://www.facebook.com/AmericanConcrete/

JohnRB,
I haven't flown quite as much as you, only about 3 million miles in the last 30 years.
The only time that I have seen oxygen masks deploy was due to turbulence, not depressurization.
I was on a flight that had an engine failure. JAL out of NRT bound for Singapore in a 747.
On climb out one of the outboard engines chucked parts, then black smoke, then the white fire suppression smoke.
We didn't change climb rate and headed out over the ocean on a 5 hour flight. But then we were in a plane tared to climb on 2 engines and cruse on 1 engine.
The 747 has always been my favorite plane, great ride and safety.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

The 787 dreamliner is the best plane. Been on a 747 and 787, no comparison.

Most surprising to me was the passenger in window seat *was* wearing her seat belt -- and still got almost sucked out of the plane. Could it not have been "low and tight across your lap?" RIP Jennifer Riordan.

Roopinder Tara
Director of Content
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Southwest Airlines Flight 1380: an Uncontained Engine Failure? Article here https://www.engineering.com/Hardware/ArticleID/168.... JohnRBaker quoted.

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Director of Content
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My 15 minutes of fame

I've been quoted before, in a couple of professional journals and at least one book (on the history of CAD), but in those cases, I was contacted prior to the quotes/references being published.

John R. Baker, P.E. (ret)
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Irvine, CA
Siemens PLM:
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It's finding someone you can't live without

In future I'm sitting on the right side of the aisle only.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

A big enough hole would make your seat position irrelevant.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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I have to ask:
Why the RIGHT SIDE of the aisle?

assuming this is a right/left statement, and not a right/wrong statement

And if it is a right/wrong statement, what make one side or the other the CORRECT side?

You're trying to confuse me and it's working.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

If the disc bursts of the other side then the likelihood is that it will hit the fuselage below floor level, or that's the perception: I'm not sure whether that will actually be how it unfolds in reality. If the cowling or nacelle breaks up then the trajectory of the parts will be somewhat unpredictable. And as IRstuff notes, with a big enough hole the impact point won't really matter except to the crash investigators.

The Aloha Air accident suggests that the size of the hole is not proportional to the chance of a crash.

I used to always sit at the tail. Last part to hit anything :)

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Unless you're flying Air France....

3DDave - Interesting you brought up the Aloha Air accident. There is some evidence that this accident was a little more complex than just high-cycles, corrosion, and the thinner structure of an early model 737. A smaller hole opened up just above the stewardess, who then was propelled into the hole and stuck momentarily. Then the major portion of the front cabin ceiling ripped away. The suggested evidence is that it was a differential pressure air-rush burst effect, somewhat similar to a water-hammer effect.

Water hammer works best with incompressible fluids that are not self-cushioning. With re-compression, the air should have reached the stagnation pressure - which is the ordinary cabin pressure - less thermodynamic losses.

Most of the investigators discounted the theory. If nothing else, the aerodynamic forces applied to the flight attendant seem insufficient to lift her from the floor, and accelerate her to the opening overhead. It would mean that the rest of the structure, which could withstand the fully pressurized cabin was unable to withstand the lower pressure levels from the original, major leak.

The evidence was a speculation. Neither the flight attendant or the missing fuselage were ever recovered.

Comcokid,
Respectfully, you are repeating the "urban myth" of Aloha Airlines flight 243 accident. Please refer to the below:
NTSB Investigation Report

I will save you from reading all 267 pages. Widespread cracking damage was found in the fuselage skin, not only in the damage area but also near it. Each of the cracks was small but many were visually detectable (though they weren't found in previous inspections). Any individual crack would have been negligible, but in combination the total strength of the skin was reduced and continuing to diminish with every flight... There were enough cracks and they were stressed enough to slowly grow... until the inevitable. Detailed examination of almost EVERY 737 aircraft in the world revealed that many had similar cracking that could lead to similar accidents. Similar examination of other similar aircraft types revealed that some of them TOO had damage like this (not just a Boeing problem). It turned out to be a widespread inspection problem, and everyone had to do a better job of examining aircraft structure from then on.

That accident (and some similar ones) were held up as examples for reference that mandated a substantial change in which all aircraft of this class and larger are designed and maintained. Many fundamental things about the design philosophy were changed. The terms "Multi-site Damage" and "Widefield Damage" became familiar. Soon after, the design philosophy of "Damage Tolerance" became the basis of all new aircraft design. Quite a few old aircraft like the 737 were "fixed" with DT philosophy, too.

STF

You could also go back to the early 50's with the DeHavilland Comet where much of what we know today about metal fatigue and how to mitigate it's impact was was first being learned, unfortunately, the hard way:

http://aerospaceengineeringblog.com/dehavilland-co...

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

"...those of us who live on or near the prairie know that, indeed, the wind does suck."

While technically whether something is sucked or blown depends on the direction the pressure differential relative the atmospheric pressure (lower local pressure sucks, higher local pressure blows), we say the wind in Wyoming is strong because Montana blows and Colorado sucks.

More data released by NTSB
https://www.ntsb.gov/news/press-releases/Pages/NR2... and

full report at

https://www.ntsb.gov/investigations/Pages/DCA18MA1...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.