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Comment by pc86 | Hacker News Reader

Remember what we always say when there is a news article - especially local news! - about anything technical. Don't forget their tenuous relationship with logic and facts when reading this article.

> A Southwest Airlines flight landed safely in Philadelphia Tuesday after the jet violently depressurized when a piece of an engine flew into and broke a window, according to passenger accounts

Violent is relative.

> The plane descended by more than 3,000 feet per minute until the pilots leveled out around 10,000 feet.

3000 fpm is nothing crazy, especially for an emergency descent with a depressurized cabin. I'm glad they included the following line:

> Arthur Wolk, an aviation expert, said that is a modest rate of descent and indicated that the pilot had control of the aircraft.

The plane was never "going down" as one passenger is quoted saying.

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Indeed, "rapid" depressurization would be the preferred term. (I'm an instructor.)

I try to be empathetic of the flying public when reading about in-flight emergencies. For passengers, a shredded engine and a broken window are terrifying. The deck angle at 3000 fpm is steeper than they've ever seen. I can understand why a passenger might use the phrase "going down."

Obviously for pilots, engine failure and rapid depress are so textbook as to be boring. The captain practices responding to these emergencies every time she's in the sim.

I don't envy the reporters. Balancing these two perspectives has got to be a hard job. And I can see how it's easy to get swept up in the emotionality.

The window went missing (https://imgur.com/a/5Adjd) at 31,000ft (https://www.flightradar24.com/data/flights/wn1380#1111bb4d). "Violent" may be a poor descriptor, but I'd be very surprised if it wasn't quite dramatic.

What is interesting is the similarity to http://www.star-telegram.com/news/business/article101413922....

Same airline, same engine. Ryanair have put plenty of hours on CFM56's without blowing any up, so what are Southwest doing different?

Don’t compare hours, compare takeoff/landing cycles. That’s when most of the stress on the airframe occurs.

Ryanair doesn't do any long haul flights as far as am I aware of, so the number of cycles should be pretty much comparable if not larger for Ryanair.

I can't find solid numbers, but what I found suggests Southwest flies twice the number of flights Ryanair does. Don't know about this specific plane though.

Southwest has 511 737-700s (what 1380 was), and 712 planes total. Ryanair only uses 737-800s, and has "over 300 aircraft in operation"[0]. Close, but still different. Ryanair operates ~600k flights yearly to Southwest's ~1.25 million.

The math gets pretty bad when you try to average all that out but if you ignore that and do it anyway (science!) then you get 1,743 yearly flights per plane for Southwest and 1,503-1,993 for Ryanair (fleet size of 301-399 respectively). So they're likely very comparable, which makes sense because neither airline could likely afford to have its planes sitting around idle for any more than absolutely necessary.

[0] https://www.ryanair.com/us/en/useful-info/about-ryanair/flee...

And on the engine, which was likely the point of failure in this incident. Although you have a different cycle count for engines since you can run it up without taking off.

Could it be the regulators that are different?

>violently depressurized

If we get to use this when a plane's window breaks, what do we say about the Byford Dolphin incident?

> Hellevik, being exposed to the highest pressure gradient and in the process of moving to secure the inner door, was forced through the 60 centimetres (24 in) diameter opening created by the jammed interior trunk door by escaping air and violently dismembered, including bisection of his thoracoabdominal cavity, which further resulted in expulsion of all of the internal organs of his chest and abdomen, except the trachea and a section of small intestine, and of the thoracic spine. These were projected some distance, one section later being found 10 metres (30 ft) vertically above the exterior pressure door.

We're nearing the ceiling of available acronyms with "violent." I guess "catastrophic" could apply?

https://en.wikipedia.org/wiki/Byford_Dolphin#Diving_bell_acc...

Diving has pressure differentials of potentially hundreds or thousands of atmospheres.

Flying has a absolute ceiling on the pressure differential of one single atmosphere - and you have to be in space to get it.

This means that an airplane depressurization event can exert a maximum of around 14 PSI. A diving depressurization event at 100 feet is 50 PSI.

EDIT: Re-reading your comment, I'm helping prove your point. So, there's that. :D

> Diving has pressure differentials of potentially hundreds or thousands of atmospheres.

That's not true.

100 atmospheres is about 1000 meters.

~300 meters (~30 atmospheres) is the world records reached with Scuba equpment.

An ADS got a navy diver down to ~2000 feet (60 atmospheres).

And the deepest a human has gone in a submersible vehicle is 35,858 which only barely clears 1000 atmospheres (~1060).

14,000lb per sq inch, good god engineers are cool.

>helping prove your point

Not necessarily! I thought the route you were going down was that, relatively speaking, this was near the "maximum decompression threshold" of the context - airplanes. As in, "it doesn't really get more 'violent' than this for airplanes, so violent is the right word."

Thanks for giving me more diving nightmares though lol

-Hundreds or thousands may be exaggerating a bit; IIRC the deepest commercial dive took place at some 600m/2000ft/60bar/850psi or so.

In the Buford Dolphin accident, the pressure differential was 9 bar/130psi.

Well, considering that most airlines operate at around 5-8psi (to reduce stress on the pressure vessel), I could argue that hundreds is still a valid measure.

But that would just being pedantic; it is an exaggeration.

Or, relatively speaking, the Aloha Airlines with fuselage damage https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243

Well, that's something I wish I didn't read this morning on HN. Did he.. survive?

> Did he.. survive?

Well, let's see:

    √ "violently dismembered"
    √ "bisection of his thoracoabdominal cavity" (i.e, body cut in half)
    √ "expulsion of all of the internal organs"

Spoiler alert: no. All four divers were killed, along with one of the tenders outside the diving bell.

You aren't living too long with your internal organs "explosively" removed from your chest. From the wikipedia article:

>Hellevik was about to close the door between the chamber system and the trunk when the chamber explosively decompressed from a pressure of nine atmospheres to one atmosphere. One of the tenders, 32-year-old William Crammond of Great Britain, and all four of the divers were killed instantly; the other tender, Saunders, was severely injured.[10]

The fourth diver was dismembered and mutilated by the blast forcing him out through the partially blocked doorway and would have died instantly

No!

According to wikipedia, the difference between explosive/violent decrompression and rapid decompression is if the air is able to safely exit the lungs. On an aircraft that means that decompression that takes less than half a second (or a tenth of a second depending on the pressure differential).

https://en.wikipedia.org/wiki/Uncontrolled_decompression#Exp...

>acronyms

adjectives?

Synonyms! I think he's looking for different words with a similar/same meaning

Both works, but I did mean adjectives!

Sidenote, I've noticed a lot of "wrong word" choices when I read through my posts here. There's no reason for it as far as I can tell... native english speaker, usually posting with a keyboard, hell I have a creative writing degree.

But I keep catching slipups like that. Super weird.

Probably pretty unnerving nonetheless, but here's some fun(1) nerdery. If you convert the probable horizontal airspeed (500 MPH ballpark) into feet per minute, it's about 45,000. Which means the plane went about 15 feet horizontally for each foot it dropped vertically. (Just very rough here, gimme a break.) The slope of its path would've been around -0.067 which is like a 6.7% highway grade. This is allowed on state & federal highways in mountainous areas of the US, though a "steep grade" warning sign is typically required for trucks' sake. The angle of descent would be 3.8º off the horizontal.

EDIT for additional nerdery: NYC and Philly are about 80 mi apart, so keeping that assumption of an airspeed of roughly 500MPH, they were in the air about 10 minutes.

(1)YET ANOTHER EDIT: Just heard somebody on the flight died, so using the word "fun" above isn't quite right to do. But I'm leaving it, with this note.

> The plane was never "going down" as one passenger is quoted saying

- they lost an engine

- the cabin depressurized rapidly

- there was unknown damage to the slats

- there was possible other structural damage to the aircraft

- someone nearly got sucked out of the plane

Given all that it seems like a major exercise in backseat driving to conclude that the plane was 'never going down', at that point in time passengers should be excused for thinking that might happen.

After all the only reason you are writing this is because you know that they landed more or less in one piece but that wasn't a given at that point in time.

Losing an engine in an airliner is as close to a non-event as you can get and still declare an emergency. It's practiced literally every time a pilot steps into a sim. It's practiced very often in actual planes if you're not flying something as expensive as an airliner. If you're flying a multi-engine prop plane, there's a better than 50/50 chance your examiner/instructor will cut fuel flow to one of the engine and not say anything to you about it.

The only reason I wrote that is because I think it helps us to keep in mind that journalists don't necessarily know any more about this subject than they do about technology, although there are no glaring issues with this article in particular. Just take any technical/engineering/process points with a grain of salt, that's all.

The plane's engine didn't lose power, it exploded and breached the hull.

The journalist didn't say the plane was going down, the person on the plane said it and the journalist quoted them, accurately.

Since this article yesterday there have been many more quotes by passengers on that plane who thought they were going to die.

There's zero reason here to claim shoddy journalism, not for this article specifically, nor any reason to bring up journalism in general. Yes journalists are not engineers. The flip side is also true -- engineers are bad at relaying the big picture story because they nitpick details that are misleading or unimportant, and completely miss the primary points as they relate to other people. I'm guessing you are not a journalist? This wasn't a modest event, and this wasn't a non-event, so as far as I'm concerned the only grain of salt here is being reserved for you.

> Violent is relative.

Violent seems entirely accurate, the pressure was enough to pull someone halfway out the window, and the poor woman is in critical condition. It was literally violent.

> The plane was never "going down"

If I were on a plane that experienced an engine explosion, hull breach, and depressurization, I'm sure I'd assume it's going down. It was terrifying enough to give someone a heart attack.

It's also hard to claim definitively that the plane was never going down. Multiple safety systems failed, and the hull was breached. This could easily have brought down the plane. They were lucky it wasn't worse.

> Don't forget their tenuous relationship with logic and facts when reading this article.

I don't see any tenuous logic or facts here... everything quoted appears accurate. I doubt the expert commentary from the ground that the situation was modest is much comfort to anyone who was on the flight.

> 3000 fpm is nothing crazy, especially for an emergency descent with a depressurized cabin.

Definitely not. Some quick googling suggests that 7000 fpm is not uncommon in emergency situations, and really you are only limited by the comfort level of the passengers (as you come back to a lower pressure-altitude). If they drop spoilers and go for ground you can probably be on the ground within 5 minutes flat, assuming a nearby airport.

(and with a depressurized cabin, the damage is really already done in terms of passenger comfort)

A friend was on a flight where a passenger had a heart attack in-flight, he said it was like being on an elevator and his inner ear was screwed up for days.

Contrast this to a more factual approach: http://avherald.com/h?article=4b7725fb&opt=0

I actually think this was one of the better articles on aviation related topics. ;)

BTW, 3000fpm is quite a lot since the plane was not pressurized.

There’s 5200 feet in a mile, so they’re descending about 1/2 mile per minute, or 30mph in the vertical direction—-a little higher than school zone speed. Considering the jet would be flying 250-500mph at that point, it doesn’t seem too drastic.

The direction of movement is important.

To compare, GA (small) planes typically descent at 500-700 fpm (my wife complains if I descend faster than 1000 fpm :) ). Jets usually do 1000-1500 fpm. Elevators in skyscrapers can go up to 1500-2000 fpm. The limiting factor is that for many people feeling partially weight-less causes nausea. Not to mention the pressure change (especially for kids and sick/old people).

Maybe the fact that the woman is dead[1] will put the tragedy in perspective?

[1] https://www.cnn.com/us/live-news/southwest-flight-emergency/...

Do we know yet who died? I don't see it there.

My point is that to deconstruct the article on merits of audaciousness is unfairly critical considering a fatality took place.

It's terrible that she died. Facts don't change because of a medical outcome and I resent the implication that we should be less critical of factual errors (of which there were none) under any circumstances. I was simply providing more context, which most people here seemed to appreciate.

There are fatalities on uneventful flights too. It's not a good measure of mechanical stress.

I don't understand what you mean. The premise of his argument was that newspapers/articles exaggerate events. Nothing seems exaggerated in this case, a person actually died.

Was the cause of death "violent" depressurization?

If a piece of shrapnel flies through the window and impales the person on the other side, you can have a fatality at sea level, no depressurization needed.

Someone just went through an experience where, during a flight, they heard a loud bang, then a window exploded and a woman was partially sucked out of it. They'd be forgiven for thinking that was violent.

Uhm... this is a very serious accident by any standard.

Nah shrapnel breaking out a window, engine exploding, and someone possibly dying. All in a days work when I'm flying.

"Violent is relative."

Yeah, but maybe while it's not violent to you, it certainly seems violent for someone that hasn't experienced this before.

The violent part was the depressurization, not the decent.

That's some serious nitpicking.

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