I Fell 15,000 Feet and Lived
uss-la-ca135.org
uss-la-ca135.org
The author's description of both not feeling his injuries until he tried to move as well as his own recognition of not being dead were spot on. I would have described it exactly the same way myself. I ended up with a broken foot and leg, but overall no lasting damage which was extremely lucky. Looking back on that experience is always incredibly surreal.
I was doing something real stupid - mid 30's, showing off to my wife, on a bike with Amerityres; I had just gotten those tires installed. They're great tires - solid tires, but feel like they are aired up. Well worth the price.
What I wasn't told was that you shouldn't do any kind of "jumps" with your bike...
So there I am showing off, and I decide to ramp off this one section of sidewalk (that actually made a good ramp). I landed, and that's when things went to hell.
Ya see, Amerityres don't deform like a regular tire does. Instead - they come off the rim. I went a$$-over-teakettle.
To this day I don't know all what or how I landed, but I do know my knee took the brunt for some reason. I came within inches of slamming my head into a concrete block retaining wall for the raised bed of the neighbor's lawn that was next to the sidewalk. The bike was totally mangled. My wife was horrified.
Now - I knew I had taken a good spill, but I thought "well, dust yerself off, laugh about it" - which I did. I told her I was fine, go home and grab my pickup so I can get home. As she biked off, I decided I would get up, and walk the bike home. I slung it up on my shoulder, and started to walk (note, this was a cheap walmart bike, and weighed a bit). Everything seemed ok. She eventually got to me, I put the bike in the back, then slumped in the passenger seat. We went home, then went inside.
We started to discuss what we were going to have for dinner (KFC, if I remember right), when I looked down at my knee...
...it was swollen to the size of softball! It didn't really feel that good, and I could barely walk on it.
We went to urgent care that night. They xray'd me and told me nothing was broken. Gave me a script for vicodin (yay), wrapped up my knee, and gave me a crutch. I hobbled around for a few weeks, and eventually all was better, with no problems in the leg since.
But in the immediate aftermath of the crash, I had no idea just how bad I was injured, nor the amount of pain I would feel. I was just walking along, carrying my bike on my shoulder, like no big deal.
I guess a lot of accidents are like that, if serious enough; probably some kind of survival holdover tactic to allow you to "get away" and to safety after an injury (or worse) a predator attack.
3 mins after, a ski medic was shuffling pieces of bone around in my shoulder and saying "i think its dislocated" all without any pain but feeling very badly winded. Adrenaline is impressive. Morphine is the best
http://www.tampabay.com/news/publicsafety/accidents/two-hurt...
Have you developed a fear of flying over this? Curious about the long term aspects at play here. Who was found at fault here? I'm assuming the boat captain.
1. Regarding solutions: This airport does not have a tower, so its up to the pilots to use the radio to announce intentions etc. To me, the core problem is that this does not loop in the boats and so there is no way to communicate. I think having the boats or some third party announce when a crossing is occurring would help. I also think, in response to this accident they moved the runway a few hundred feet further from the channel.
2. Regarding blame the NTSB actually ruled it pilot error, but I think that is myopic and only because there wasn't really anything else they could say since their jurisdiction doesnt extend into the rules of boats. Technically it is pilot error, but there were other errors as well from each side that all combined.
3. In terms of fear of flying, im actually okay. I had to fly twice per week for work for many years following this. Sometimes i'd have some flashbacks or bad thoughts, but overall don't have an issue. I've also been back up in a small plane just to do it. That said, I view commercial airplanes as completely safe and have no real fear with them. With small planes theres just so much can go wrong. The planes are not the issue, they are safe themselves. However, because of many small airports not having a tower, the lack of safety comes from having to deal with many other factors at play. I want to fly again later in life, its amazing and I have a love of planes. At this point though I feel like it would be pushing my luck so don't really do it.
[1] https://app.ntsb.gov/pdfgenerator/ReportGeneratorFile.ashx?E...
Mostly though, I think there just should have been much more regulation given the number of parties operating in the same space.
There are NOTAMs (Notice to Airmen) that tell us about new structures that have been erected that could be problematic. NOTAMs also tell us if parts of the sky are off limits, for example if an airshow is on.
Other than that, and I am generalising a lot, there is no air collision avoidance in the majority of private planes here in the UK. Your two best mechanisms of defence are your eyes, and keeping one ear on the radio to get a feel for where everybody else is. If they're not too busy air traffic control will warn you about other planes in your vicinity, but it is not mandatory. There are also TCAS (https://en.wikipedia.org/wiki/Traffic_collision_avoidance_sy...) systems you can bolt on to your plane, or might come with new planes, but they're not mandatory and I've yet to fly a plane that comes with one.
As for finding fault. That doesn't happen in air accident investigations. Air Accident Investigation Reports (https://www.gov.uk/aaib-reports) are specifically engineered to focus on the problem, and find a solution to prevent a repeat of it. They are not designed to apportion blame, but instead learn from the mistake and build mechanisms for ensuring that the same outcome is mitigated. That's not to say you won't be prosecuted but that's a separate process.
I am curious about how you remember your perception of time. This is a simple description, but it is "fast not fast" when it is happening to you. "Yep this is happening. Oh, they are going 25. Yep they are going to hit me, that is going to be scary, possibly hurt, and cost a lot to repair. I hope this doesn't hurt my neck. I should put my feet flat. Crunch. Okay, that didn't hurt. The airbag didn't deploy. ..." In about 1 second.
Watching the accidents it is sort of surreal, just sort of flat. Bang. Spin. Stop. Airbags deflate. I immediately check surroundings, move out of danger, call 911, try to recall safety things, keep people in place if their injuries seem serious and their vehicle isn't on fire, but it all feels "real time" watching things. It just doesn't register the same in my brain.
My direct memory is basically as follows:
1. Whoosh of pole, bang noise. 2. "Was that a sailboat" 3. See/feel the world rotate 4. "I think we are going to crash" 5. "I could die" 6. I don't actually remember the impact just flipping and all of a sudden seeing the ground above my head upside down 7. "I'm still alive...but its not over yet" 8. The glass shatters and we come to a stop 9. My friend asks if I am okay. I respond yes. 10. I quickly feel my face as i'm not sure how injured I am, there is some blood on my hands, but not a large amount. 11. I start to feel a burning sensation as some jet fuel and other chemicals are reacting with my skin 12. I start to panic as I realize the gravity of the situation and begin to call for help. 13. Just as I am beginning to really panic, I feel a hand reach in and the plane lifts up. 14. I undo my harness, as my leg moves for the first time, I realize a sharp pain in my foot. 15. I am pulled from the plane and dragged from under my arms with my legs facing the plane. I watch the plane get farther away as im dragged. 16. I am layed down and am instructed not to move until the paramedics come.
https://www.google.com/maps/@27.9136028,-82.4500183,1593m/da...
Can anyone explain the quote below? I don't really understand how the minesweeper understood the signal.
---
The Coast Guard amphibian gained altitude and flew off. (I learned later that he headed for a squadron of minesweepers that was returning to the United States from a tour of the Western Pacific. He was unable to tune to their radio frequency for communications. But this ingenious pilot lowered a wire from his aircraft and dragged it across the bow of the minesweeper, the USS Embattle. The minesweeper captain understood the plea, and veered off at top speed in my direction.)
That would be a totally unexpected behavior, which would give the minesweeper's captain the clue that it was a signal to change course to the given heading. The plane would have headed back to the pilot and circled, giving the minesweeper's captain assurance he had understood the signal.
In this case I'm guessing the wire was more like the second, confirming clue.
It is not a standard or anything, so abnormal enough to get the drift.
In general I'm don't think aviation have marine VHF and vice versa, except maybe the coastguard and other special cases.
and this one of a paraglider surviving a thunderstorm uplift: http://www.smh.com.au/news/national/dead-luck-ewas-flight-of...
Water, though, isn't the pencil dive the clear winner? Everything else would decelerate you so much faster that it would be bound to cause injuries. The only downside (relative to all other methods of impact) I can imagine is how far underwater you might end up.
I would be happy for someone to tell me otherwise, but this is my completely theoretical summation of a terminal velocity water-landing.
Basically, cross your legs, point your toes, cup your testicles with one hand, and cover your nose with the other.
The force of hitting the water will crush your testicles and rip your nose off your face. So, you cover them. You cross your legs to keep them together. You point your toes so you don't shatter your feet, ankles, or legs.
When your feet hit the water, immediately bend at the waist. You're going fast enough that you're completely in the water. You fold at the waist to make your depth more shallow. You then flip and swim to the surface.
This works at greater heights but survivability goes down at about 90'. You can practice at lower heights, if you want to learn it. I'm sure there are videos and whatnot.
When you do hit it, just relaxing will fold you up - by the way. You're going so fast that you won't relax before you're completely submerged and slowed. I forget the numbers but it means your dive is more shallow than if you'd stayed tensed. There's a ratio for it, but I've long since forgotten.
I suspect there's been a bit posted about this. My enlistment was a long time ago but I'm told they still teach it. There may be some modifications to it, or new data for survivability.
At least 5 redundancies failed: the Ram Air turbine, primary and secondary ejection sequences, the parachute, and his survival pack went missing. And yet Mr. Judkins survived maybe because he had spleen removed. Amazing.
My team is working on building one of these auxiliary generators right now, fun project.
Earlier this year I deployed a RAT by mistake (poor mechanical design) and I believe it died as we were flying too fast for it (poor electrical design)
https://en.wikipedia.org/wiki/Alan_Magee Alan Magee survived a 22,000-foot (6,700 m) fall from his damaged B-17 Flying Fortress. He was a ball turret machine gunner. Hit glass ceiling of a railway station which supposedly broke the fall.
https://en.wikipedia.org/wiki/Nicholas_Alkemade Nicholas Alkemade survived, without a parachute, a fall of 18,000 feet (5,500 m). He was serving as a rear gunner in a Royal Air Force Avro Lancaster. His fall was broken by pine trees and a soft snow cover on the ground.
About non-functioning parachutes. I was reading "Flying Low" by B.K. Bryans who became a US Navy Jet pilot around mid 1960's. When he was going through his training in propeller driven training planes, a fellow student pilot bailed out of a trainer but fell to his death when the parachute didn't open. The trainer plane had no ejection seat so the student pilot had bailed out the old fashioned way, which required pulling a cord of the parachute manually after exiting the plane. His parachute tragically didn't open.
The base commander dropped 10 randomly selected parachutes from the base and NONE opened. A rigger from another airbase nearby was brought in and all the parachutes were all repacked.
The debate is whether in this case what made the difference (apart the "luck" of landing on a snowy ravine) was that the pilot was unconscious (like in the Magee case), i.e. with all his body completely "relaxed", and this somehow mitigated the impact (in comparison to someone who "prepares " for the hit).
All of a sudden a wave about 20 feet appeared out of nowhere and almost swept us off the cliff.
I was recording a video of the waves. We looked back at the video later and you hear me go “oh shit”, pick up my wife, and run just to get pummeled by this thing from behind with water splashing over us. We got pretty far from the cliff and I’m not positive how much of it was running verse being pushed.
The end of the video is us soaked cracking up with broken flips flops and me saying “my phone got wet”. We absolutely don’t remember any of it. It was pure adrenaline the second we saw the wave.
I have a healthy fear of standing up in the ocean now...
Self-rescue is really, really rare unless you've been incredibly lucky enough to float towards the top of a shallow deposition zone in a small slide. Or you've been deposited on top. Even in a relatively shallow burial, 10-12" inches (or even less) means you're entombed in what might as well be concrete. If you're lucky, you'll be able to at least push away a cavity to breathe into while you wait for the rest of your group to dig you out before you asphyxiate. There's equipment that can help you improve your chances (airbag, AvaLung) beyond just the beacon, but they're not guarantees. If it's in your mouth and it isn't knocked out, an AvaLung might help you extend your air supply. An ABS airbag system will hopefully help you float closer to the top during the slide. It won't help you if you slam into a tree or other debris and break your back.
Whether it's in the snow, or in the water, mother nature is an uncaring mistress who demands respect. Even when you do everything right, she can still kill you. If there's one good thing about hearing these stories, terrifying and tragic as they often may be, it's that they can drive home that point. The outdoors are, more often than not, a continual exercise in risk management. We put up with it because there's nothing quite as breathtaking as seeing the sun peak over a snow-covered horizon from atop the mountain. Or as exhilarating as the ride down.
We underestimate it because we're used to water flowing around us at low speeds. But once you've got enough of it moving quickly, the viscosity and momentum really starts to matter.
The thing I think of to try to ground my intuition is to imagine someone throwing a gallon of water at me, still in its jug. Now imagine thousands of those hurtling my way. That's a big crashing wave.
I managed to walk/ski (one ski was still on me, but badly broken ) to a nearby village and driven on a stretcher to the hospital.
I am lucky to be alive. It is amazing though how clear you can think in life threatening situations. the moment I noticed the avalanche I knew exactly what to do and where to go. When I was buried I remember rocking back and forth to get some wiggle/breathing room and when it stopped I waited until my mind cleared up, struggling hard to defeat the panic and pain, until assessing g the situation.
Very nice to hear you survived such a bad accident.
>>I am lucky to be alive. It is amazing though how clear you can think in life threatening situations.
David Allen talks about these situations in this talk. In the moments of crises, the brain brings about all its focus to the highest priority task at focus. Its almost like crises commands the best kind of productivity.
The cherry on top: they can now spend the time until their next deadline thinking about the amazing grades they would get if they worked more than one night per month.
Source: me
Later on in life, plenty of companies try to make use of it, pushing people into long hours and short deadlines, and find that it doesn't work as well.
That is because you need some skin in the game. Nobody is losing sleep to work on a project whose success or failure has no disproportionate effect on the well being of the individual.
I had the same during an almost traffic accident when a truck wasn't giving me the right of the way from a side road. Brain just switched to autopilot and managed to go inches away from both truck and barriers on the other side of the road. No damage done. It was kinda amazing, being an observer only.
They can spit or pee.
[1]: http://articles.latimes.com/2012/feb/21/nation/la-na-nn-aval...
These serve the dual purpose of protecting your head and decreasing your density so you float to the top of the snow pack.
Yes, obviously there are big enough avalanches with huge slabs that will kill you in the ride, especially if you end up going through trees, but most skier involved avalanches are on more open terrain (thus why they slide) and are loose snow while moving.
This is tautological. Yes, few people survive killer avalanches, because that's what defines a killer avalanche.
Many avalanches encountered by backcountry skiers especially are not these giant killer ones, and can be survived either by skiing out of them or having the proper equipment and training. Your odds aren't great, but they aren't nothing either or people wouldn't bother carrying the gear. (beacon / shovel / probe / avy bag)
Anyways, this is sufficiently off topic, but your characterization of avalanches is movie-like-stuff. Huge avalanches happen but they aren't the typical case. Most are small / medium slides triggered by humans in the backcountry.
https://www.youtube.com/watch?v=NDEP15NTMgc
Some avalanches can destroy bridges or change landscape. It's truly just the survivor bias we see on videos making us think the worst cases aren't very common.
I actually understand skydiving, bungee jumping, or climbing Everest, because they are controlled risks, but white water rafting seems very chaotic.
Now, whether or not you've really accomplished anything if you've had a team of people babysitting you to the top is another thing altogether.
https://en.wikipedia.org/wiki/List_of_ski_descents_of_Eight-...
For basics, sure. Get into stacking, swooping, wing suit flying, CRW, XRW, BASE, etc and it gets extremely challenging to the point where dying is inevitable if you keep doing it.
I’ve been white water rafting maybe a dozen or more times in my life and have done CL5 / CL5+ rapids multiple times. I can assure you, no skydiving place I know of will let you get close to doing the activities I listed above with that little experience under your belt.
Edit: As an example, when I worked at LinkedIn we as a team outing did Class IV+ rapids and most folks had zero prior experience. I think the “coaching” was like a 15min briefing before setting off, where as for sky diving you have to do an all day ground school class before jumping with two instructors holding onto you virtually the whole time. Even after being certified, you still typically have to go through the class again if you haven’t jumped recently.
Did this happen to you or someone else? You switch from first to third person without explanation. "Riveting read" seems like a weird conclusion.
Did they just figure out something was wrong or is dragging a wire a common naval code?
The exit was my fault. To initiate a jump, the pilot would count down from three and then scream "GO". With the door open it was very difficult to hear. Clouds were forming and we had already aborted twice, with my partner pulling us back into the plane each time.
On the third attempt I misread the shouts and hand signals and exited the plane before "GO". I was taller and heavier than my tandem partner so he probably had no choice.
We tumbled into thick, gray clouds. Without a horizon this made me nauseous. My partner was screaming from the moment we left the plane. I'd catch a word or two but most of his instruction was lost to the wind. We were totally out of control.
We exited the cloud still tumbling, my partner still screaming. I remember the chute opening, but we were never properly in control.
The next few minutes were glorious, though still nauseous, and the landing was uneventful.
I didn't think much of the consequences back then... But no more skydiving for me :-)
Our "instruction" was a 30 minute VHS tape about how we couldn't sue for any accidents.
Sketchy indeed.
The Free Fall Research Page: Unplanned Freefall? Some Survival Tips by David Carkeet
http://www.greenharbor.com/fffolder/carkeet.html
Reading these articles is very personal to me, because I crashed my parapente on takeoff on what would have been my second solo flight. I still want to take up training again, but I need a new coach who I trust to tell me when the wind's strong enough.
A. Your coach. B. The most experienced pilot on site. C. You (the pilot). D. Parachuting club owner.
For paragliding there's USHPA ratings, feel free to study them: [1]. For example in 12-02.13 there's requirements for P1 (Novice Pilot) rating, and recommended operating limitations for them:
1. "Should fly only in steady winds of 12 MPH. or less."
[1] https://www.ushpa.org/legacy/documents/sop/sop-12-02.pdf
Why did I continue? There's no other English-speaking coaches in the south of Taiwan. Also, his training was the only one I could afford. I really want to learn to fly.
"I need a new coach who I trust" is more related to the other issues than the relatively minor incident where I ended up in a tree. I accept my share of the responsibility for attempting that takeoff, and I'm grateful that it didn't result in serious injury. When it happened though, it was an appropriate time to call off the course and stop that con man from trying to sell me unsafe equipment.
And, back to the topic, it means I have a personal sense of how terrifying it can be when a parachute doesn't inflate.
I wonder if this thought ever occurred to the pilot.
A fantastic read.
While this may sound insanely OCD, I remember thinking that I didn't have to get the number of counter-revolutions exactly right -- within a half-dozen or so should be "good enough".
I guess I was an imaginative child.
Greg Egan goes into such things at length in Permutation City.
Three different wingsuit pilots have survived unintentionally crashing into trees with no parachute out now:
https://www.youtube.com/watch?v=kp3YLdhraPw
https://vimeo.com/50817449 (view at 6:35)
http://www.basejumper.com/cgi-bin/forum/gforum.cgi?post=2994...
And then you have Jeb Corliss crashing full speed into a mountain and surviving:
Your chances of surviving a wingsuit, or any kind of BASE jumping accident are considerably worse than your chances of surviving a single round of Russian roulette with five rounds in the cylinder, even if you're the only player.
Like I say, your chances of surviving a wingsuit accident (basically impacting the ground, a cliff, a tree, whatever) are considerably worse than this.
Sadly a lot of it is down to chance - speed and angle he hit the water, for example - and would be very difficult to ever repeat.
Asked because of reading this article.
https://theaviationist.com/2014/09/15/f-15-lands-with-one-wi...
Interesting tidbit: they slapped a replacement wing on and returned the aircraft to service.
[1]http://gmauthority.com/blog/2017/09/one-tiny-crack-led-a-c7-...
A small crack, but not minor.
Bahia Bakari https://en.wikipedia.org/wiki/Bahia_Bakari https://en.wikipedia.org/wiki/Yemenia_Flight_626
Juliane Koepcke https://en.wikipedia.org/wiki/Juliane_Koepcke https://en.wikipedia.org/wiki/LANSA_Flight_508
there is a few similar posts here, but I always thought that the only known person who ever survived a fatal passenger aircraft crash, dropping out at high altitude, was this person:
https://en.wikipedia.org/wiki/Juliane_Koepcke
She was the only survivor of 92 passengers and crew in the 24 December 1971 crash of LANSA Flight 508 in the Peruvian rainforest. When the airliner broke up in mid-air, she survived after plummeting about 3 km (~10,000 feet) while still strapped to her seat, before crashing through the rain forest canopy and coming to rest on the forest floor.
Her injuries did allow her to walk for 10 days, until she was found. So you could say, it was mostly light injuries.
It is nowhere mentioned that she had a missing spleen btw.
someone else posted also this list: https://en.wikipedia.org/wiki/List_of_sole_survivors_of_airl...
The only countries not to use feet as a measure of altitude for aviation purposes are China, DPRK and Russia. They use metres.
PS: wow, interesting https://fr.wikipedia.org/wiki/Unit%C3%A9_en_aviation
French influence on aviation has been strong since the beginning (hence all the French words - aileron, fuselage, décalage, etc), but the unit of height/altitude is one where the Americans set the standard.
(Source: I fly an American-designed, French-built aeroplane to/through France semi-regularly.)
Aviation also measure speed in knots, and distances in nautical miles. But those don't have good reasons to be kept.
1 knot is equal to 1 nautical mile/hour, which is traditionally 1 minute of latitude. I assume they have been kept for tradition and also in the event of an emergency requiring manual navigation?
```“This is very serious,” I thought.```
This is balls of brass and nerves of steel combined.
But if you stay calm, despite thinking it is hopeless and take your small chances, once they arise - you might actually succed and survive ..
I believe that's a core part of the training for Navy SEALS.
They push you far past your "breaking point" to realize that it isn't where you thought it was, helping you learn to keep your head about you when in extreme situations.
I mean, I've obviously seen good storytelling from journalists and writers, but they've often spent lifetimes honing their craft.
I wonder if it's the focus and awareness that gives pilots such a potential.
[1] http://www.telegraph.co.uk/news/2017/10/04/army-sergeant-hav...
"Volume / Normalized: 100% / 53% (content loudness 5.5dB)"
> “This is very serious,” I thought.
“Some days you are the dog and others you are the fire-plug.”
I would assume the fire plug is the name of one of the things that failed while he refueled. Doesn't quite go together in my head, but once you understand the original quote it makes sense. Some days you're on the giving end, some days you're on the receiving end.
Then I later realized that this was a chapter from a book. Whew! the tale has got my heart pumping. This is some amazing narration of an amazing incident
Given the situation, he's got some balls.
en.wikipedia.org/wiki/List_of_sole_survivors_of_airline_accidents_or_incidents
I think it's even more amazing when it's a commercial flight and everyone dies except one person. I can't imagine what sort of psychological toll that would have.
https://www.futilitycloset.com/2017/07/10/podcast-episode-16...
How can someone be so calm in that situation?
Nerves of steel, bravo!
You want to maximize your surface area and protect your head. Let your body absorb as much of the impact as possible: Land almost horizontally, with your feet hitting first and your head hitting last. This way, you might only break every bone in your body instead of dying.
It sounds like his pilot chute and un-deployed main chute slowed him down just enough, and he landed well enough, that his body was able to take it. Lack of spleen helps too.
It also means that in a free fall spreading your body out horizontally to increase the drag forces, then re positioning just before landing would be the optimal choice. Not that you think of that in a free fall, but the physics are there.
I know it'd be basically impossible for a human to actually do this perfectly. But I wonder, in theory, how much one could reduce the impact energy. Maybe you could hit at 50mph instead of 120mph.
Will a passenger from a passenger airline survive if falling from 15,000 feet?
Bahia Bakari https://en.wikipedia.org/wiki/Bahia_Bakari https://en.wikipedia.org/wiki/Yemenia_Flight_626
Juliane Koepcke https://en.wikipedia.org/wiki/Juliane_Koepcke https://en.wikipedia.org/wiki/LANSA_Flight_508
Vesna Vulovic https://en.wikipedia.org/wiki/Vesna_Vulovi%C4%87 https://en.wikipedia.org/wiki/JAT_Flight_367
Here's a pic of the roof that saved one guy http://cdn2.fella.com/2016/06/20151717/Magee-11.jpg
I'm anxious about an event tomorrow, and this put me at ease.
Then again, I have a spleen...
There would be blame to go around as a result of this, and surely some op changes.
Re: Ejector seat, it could also have been pilot error, if he had forgotten to take the safety pins out of the ejector system during his pre flight check. They are there specifically to prevent the ejection rocket from firing while maintenance crew are working on the aircraft on ground, and should be removed (by either pilot or crew chief) before flight. I know that in Naval aircraft, the pilot has to replace these pins as one of the last things he does before leaving the aircraft after landing.
The 'odds' are not that there was some unlikely event.
The 'odds' are that someone/some group was not doing their job.
As in James Reason's famous "Swiss Cheese" model of accidents:
> In the Swiss Cheese model, an organisation's defenses against failure are modeled as a series of barriers, represented as slices of cheese. The holes in the slices represent weaknesses in individual parts of the system and are continually varying in size and position across the slices. The system produces failures when a hole in each slice momentarily aligns, permitting (in Reason's words) "a trajectory of accident opportunity"