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00:01Most plane doors aren't locked.
00:03There are no keys, no sensors or passcodes to secure them.
00:07If someone wants to pull the lever, they can.
00:10A man opened the emergency exit door and forced his way off the plane.
00:15And yet, with 40 million flights each year, these doors are virtually never opened in flight.
00:21So why not?
00:22It's self-preservation, surely.
00:24Common sense.
00:25Most people are, you know, smart enough to not mess with that.
00:30The real answer relies on where planes fly.
00:34How high do planes fly, approximately?
00:3610,000 kilometers, or is that overshooting it?
00:39I think that's overshooting it. I think you'd be in space.
00:4225,000 kilometers.
00:43That's the height of a plane flying.
00:45Is that way too low?
00:46It's too much. It's too much, too much, too much. Bring it in.
00:491,000 kilometers.
00:511,000 kilometers, still space.
00:5350,000 feet, I think.
00:54Some of them can go up to 43,000 feet.
00:5730,000 feet.
00:5838,000 feet.
00:59Yeah, yeah. Why do they fly that high?
01:02Uh...
01:03I don't know. Safety, I guess.
01:05Probably to avoid collision with other aircrafts and if there's high mountain ranges.
01:10I don't know, when storms or weather hit.
01:13My guess is to avoid a turbulent weather.
01:17I think that's a decent guess.
01:19Now, it's true that one of the benefits of flying at 30,000 feet is a smoother ride.
01:24This is high in the troposphere, the layer in which most weather occurs.
01:28So there's less turbulence and fewer storms to navigate around.
01:33But this is not the main reason that planes fly so high.
01:37The bigger reason, of course, is money.
01:40As you go up, the density of air decreases.
01:43And at 33,000 feet or 10 kilometers, the density of air is just a third of what it is at sea level.
01:50So flying at this altitude, the plane runs into a third of the air molecules it would closer to the ground.
01:56That means the plane can fly about 73% faster for the same amount of thrust.
02:02And as a result, you get to your destination faster.
02:05And since you spend less time in the air, you burn less fuel.
02:10It seems in a way that, like, climbing is wasted energy.
02:14Can you compare, like, the descent to the ascent?
02:17Do you essentially get the energy back as you fall down the other side?
02:20Yeah.
02:21When we climb, we burn about 80 kilos per minute.
02:24In cruise, we burn about 40 kilos per minute.
02:26And in descent, it's maybe 10.
02:29So it's almost negligible.
02:32Not only that, jet engines are more efficient at altitude.
02:36They work by compressing air at the intake, mixing it with fuel and igniting it.
02:41So the combustion products are ejected very fast from the exhaust nozzle.
02:45Now, this process is more efficient the colder the air is.
02:50And at altitude, the temperature is around minus 50 degrees Celsius,
02:54which is a lot colder than an average of plus 15 here at the ground.
02:58So flying higher means you burn less fuel for less time
03:03and avoid the weather and associated turbulence of lower altitudes.
03:07The other reason you want to fly high is to take advantage of the jet stream tailwinds.
03:12And the company likes people who do that because you're burning less fuel, so it's less money.
03:17But there is a problem with flying this high.
03:21The air up there is unbreathable.
03:23If you were suddenly teleported to the top of Mount Everest, a height lower than planes fly,
03:29you would remain conscious for only about three minutes.
03:33This is because in addition to density dropping with altitude, so does air pressure.
03:38Air pressure actually falls off faster because it depends on the weight of all the air above you.
03:43So at 10 kilometers, the air pressure is only a quarter of what it is at sea level.
03:48To be clear, the air is still 21% oxygen.
03:52But the partial pressure of oxygen, the pressure exerted solely by oxygen molecules,
03:57is around 5.5 kilopascals, which is a quarter of what it is on the ground.
04:03Now at this pressure, not enough oxygen molecules can force their way into your blood in your lungs.
04:09To function normally, humans need an oxygen partial pressure of at least 16 kilopascals.
04:15So all the cabins of airplanes that cruise at high altitude must be pressurized.
04:21A little bit of air is continuously brought into the cabin from outside.
04:25It actually comes in from the compression stage of the jet engines.
04:29That is what maintains breathable air inside the plane.
04:34The downside is that you are taking away a little bit of the efficiency of the engines.
04:38Now pressurizing the cabin required a radical redesign of aircraft.
04:43Before pressurization, planes would fly up to 10,000 feet, or around 3 kilometers,
04:49where the partial pressure of oxygen is 15 kilopascals, just at the limit of what people can handle.
04:55On these planes, doors opened outward, and there wasn't much concern about the seal around them,
05:01since the pressure was the same on both sides.
05:03But once planes were pressurized, all the doors were changed to be the shape of a plug.
05:09They're wider on the inside than the outside.
05:12That way, the higher pressure inside the cabin pushes the door into its frame, creating an airtight seal.
05:19How airtight is a cabin?
05:21It's pretty airtight, but not completely airtight.
05:24So you'll notice, for example, every time that someone flushes the toilet,
05:28you'll see some of the air pressure go down.
05:30So every time that happens, you can actually see the cabin altitude jump a little bit.
05:34And this is why plane doors and emergency exit doors don't need locks.
05:39The difference in pressure between the pressurized cabin and the low-pressure exterior is so great
05:44that no one is strong enough to pull the door inwards.
05:49And if someone had come up and turned that while you're mid-flight?
05:54Nothing.
05:55Even modern plane doors that open outward are shaped like plugs.
05:59They're just cleverly designed.
06:01The main passenger door on a Boeing 737 is both wider and taller than the frame it needs to pass through.
06:07But when you pull the lever, gates at the top and bottom fold in, reducing the height just enough.
06:14However, the sides are still too wide, so the door first has to pop inside and rotate.
06:20It's that movement inwards that is impossible at altitude.
06:24It would require a force equivalent to lifting 9,000 kilograms.
06:29And airplane cabins aren't even fully pressurized to the sea level pressure of 101.3 kilopascals.
06:37You may have noticed this if you take a bag of chips on a plane.
06:40It's easy to squish on the ground, but as the plane climbs, the pressure in the cabin drops
06:45and the chip bag seems to inflate like a balloon.
06:48I measured the pressure in my plane, and at cruising altitude the pressure dropped to 77 kilopascals,
06:55meaning the partial pressure of oxygen was only 16 kilopascals,
06:59the minimum required for people on the plane to feel normal.
07:03This has some unintended consequences.
07:06Do you think you fart more in a plane?
07:09If I did, I'd blame someone else.
07:13I feel like no.
07:15No.
07:16I can't let it rip nowhere in the world.
07:18Do you think you fart more in a plane than on the ground?
07:20100%.
07:21No hesitation.
07:23Sure, I mean, it's got to do with the cabin pressure, right?
07:26So as you go up, that cavity in here now expands, and the air wants to go somewhere.
07:33And the quickest place it can go is south.
07:37Bag of chips just part by itself.
07:43Now, the International Space Station is pressurized to sea level pressure, 101.3 kilopascals.
07:49So why are planes pressurized to the minimum extent possible to carry human passengers?
07:55Well, it's actually for a very good reason.
07:58In 1988, Aloha Airlines 243 was en route from Hilo to Honolulu, Hawaii.
08:05The cabin was being pressurized, as we've described.
08:08But unfortunately, this plane's fuselage had a small crack.
08:13And all of a sudden, at 24,000 feet, the crack widened and the whole roof tore off the front of the plane.
08:20Miraculously, the pilots were able to land safely and only one person was killed.
08:28The difference between the International Space Station and a plane is that the ISS was pressurized once and it stays pressurized.
08:36But a plane experiences a pressure difference every time it climbs to cruising altitude.
08:42So the fuselage is stretched and then relaxed with every flight.
08:47Stretched and relaxed, stretched and relaxed.
08:50The Aloha Airlines plane had the second highest 737 flight cycle count in the world, with nearly 90,000 in total.
08:58That's way more than it was designed for.
09:01This led to fatigue, cracking, corrosion and the eventual explosive decompression.
09:07So planes are pressurized to the least extent possible to minimize stresses and extend the life of the plane.
09:14But even 75% of atmospheric pressure should be plenty to prevent the doors from opening.
09:20So how did this happen in May 2023?
09:24The passenger panicked and actually managed to open an Airbus emergency exit in flight.
09:32They were on final approach then, they were quite close to the ground, so the pressure differential was very little.
09:37And because of him using all of his force, he actually managed to get the door open, which was crazy.
09:43And we didn't think that that was possible.
09:46But if you want something bad enough, I guess it is.
09:49Wow. Was he okay?
09:51He was okay. Everyone was okay in that case.
09:54That was a pretty serious mishap.
09:56So I guess the next logical question is, have any other passengers inadvertently caused a mishap by, say, forgetting to put their phone on airplane mode?
10:05When you're sitting there on the tarmac and they come on and tell you to put your phone on airplane mode, do you do it?
10:11And why, why do they get us to do that? What is the reason?
10:16Is there a reason?
10:17Obviously they wouldn't ask you to do it if it wasn't for some benefit.
10:21I am unfortunately a bit of a rebel and I don't follow the rules, and yep.
10:24But you're not worried about taking the plane down?
10:26I'd make sure my parents have their airplane mode on so I can have it off.
10:30I mean, yes I do, because I don't want it interfering with, like, the radio or whatever.
10:35Well, I think it's the communication interference.
10:38I feel like I've always been told, like, it messes up, like, instruments, but honestly, they're always just told to do it.
10:45So, you know, just gotta put your phone on airplane mode.
10:48In 1961, the Federal Aviation Administration, or FAA, found that some portable FM radios could interfere with plane navigation systems since they used neighboring radio bands.
11:00And out of caution, they banned almost all personal electronics on flights.
11:05But airlines could test any device for interference and overrule the FAA ban to allow it on board.
11:12Any device, that is, except a phone.
11:15Because another organization has jurisdiction over phones, and that's the Federal Communications Commission, or FCC.
11:24See, a phone on the ground with buildings and hills around it can usually only see one or two cell towers at the same time.
11:31But from the air, it could see 10 or 20 or more.
11:35The concern was that 200 phones traveling at 800 kilometers per hour in a plane could rapidly connect too many towers at once, overloading the infrastructure.
11:45At least, that's what the FCC thought could happen.
11:48So they banned cell phone use in flight in 1991.
11:52But there's a problem with this theory.
11:57A plane is a big metal enclosure, essentially a Faraday cage.
12:02So it should block almost all electromagnetic signals.
12:05That's why plane antennas are located on the outside.
12:08Your phone signals can only escape through the windows, which means they go horizontally out the sides of the plane.
12:15So they would have to travel long distances before reaching the ground.
12:19And the cell towers your phone is trying to connect to?
12:22Well, they are tilted downwards.
12:24You know, to collect all the signals from people walking around on the ground.
12:28So it's very hard to make a connection from the air unless you're flying really low.
12:33So phones could only conceivably disrupt ground networks during takeoff or landing.
12:38And the FCC never even tested if this was the case.
12:42In 2005, they went before Congress and said the rule banning 800 megahertz cell phone use in flight may not be needed in order to protect ground-based cellular networks.
12:54As far as we know, a mobile phone has never caused an air accident.
12:58All airplane mode does for sure is save your battery life.
13:02So why are these rules still around?
13:05I've been flying myself and where I've gotten interference.
13:08You know, when you're talking to air traffic control and you get that, you know, that signal.
13:14And that is because someone is either using their phone or the phone is on.
13:18Will one phone in an aircraft cause any problems?
13:22Probably no.
13:23Will 200 do something?
13:26Maybe.
13:27Rather than taking the chance of like, let's everyone update their Twitter profile at 500 feet.
13:33Rather than saying that, we're saying, no, you know, just keep them off, you know, enjoy the Wi-Fi up at altitude and that's it.
13:42But airplane mode might soon be a thing of the past.
13:45The EU actually no longer requires it and is pushing for airlines to provide 5G service on all EU flights.
13:52So we may eliminate that inconvenience, but we still have to deal with airplane food.
13:58What do you think about airplane food?
14:00I only eat the bedrolls. That's anything I can handle.
14:03Apart from that, everything tastes like mush.
14:05It can only be very good. It can be very terrible.
14:07Eh, blandish, different consistency.
14:10Do you think the food tastes as good in a plane as it would on the ground?
14:13No.
14:14But bad tasting food might not be all the airlines fault.
14:20See, the air that's pumped into the cabin at altitude is really dry.
14:24I mean, the Sahara Desert for reference has an average relative humidity of 25%.
14:29But inside an airplane cabin, it can be as low as 5%.
14:34This can dry out your nasal passages, hindering your sense of smell and therefore taste.
14:40The lower cabin pressure can also decrease sensations like the intensity of salt and sugar.
14:46But there is one flavor that appears to be enhanced in flight.
14:51What do you drink in an airplane? What's your drink of choice?
14:53Apple juice.
14:54Apple juice?
14:55Yeah.
14:56Interesting.
14:57I mean, Coke, that's default.
14:58Orange or apple juice?
15:00Gin and tonic?
15:01Maybe a Bloody Mary, for fair.
15:04You're the first one today.
15:05Really?
15:06Yeah.
15:07A German survey of a thousand flyers found that more than a quarter of them order tomato juice in flight.
15:14And what's really weird is that 23% of those people would never drink it on the ground.
15:20And would you drink Bloody Mary, would that be like a standard drink at the bar, or is it a special plane drink?
15:25I only have it on planes.
15:26So why is everyone ordering tomato juice?
15:29Well, it could be because of the noise.
15:32A 2015 study points to the corda timpani, a nerve that carries taste information from the tongue to the brainstem.
15:39It runs right past the eardrum, between the tiny sound conducting bones.
15:44So loud cabin noise might unintentionally stimulate it.
15:48This could produce an audio illusion that boosts our sense of umami, the savory taste you find in MSG, soy sauce, and, well, tomatoes.
15:58I always drink tomato juice, and I never knew why. It just felt like my plane drink, or like spicy tomato juice.
16:04Yeah.
16:05Like both of those are favorites of mine.
16:07Yeah.
16:08So next time you're on a flight, go for something extra sweet or salty, or maybe try the tomato juice.
16:15I feel like with how much people fly, our perspective of flying is still pretty distorted.
16:20So why is that?
16:21Yeah.
16:22I know that we talk a lot about accidents and incidents, and we dig into them really, really deep.
16:27And people might ask, why would you be doing this?
16:30Doesn't that just make people even more afraid of flying?
16:33But the fact is that this is one of the prime reasons why aviation is as safe as it is.
16:38The fact that we have hundreds of professionals that dig deep into these accidents means that we learn from them.
16:45So every flight becomes a little bit safer.
16:48That's actually a big reason that I started my channel, Mentor Pilot, in the first place.
16:53Because I promise you, the more you know, the safer you'll feel.
16:59Do you think that climate change increases turbulence?
17:04Depends on what people think, or the opinions.
17:07There's been a bit of that in news recently, hasn't there?
17:10Today, the media tends to prioritize sensationalized headlines over key details.
17:15Part of why airplane mode is still such a big deal today is because of the media frenzy it started in the 1960s.
17:21So it's more important than ever to look at all sides of the story.
17:25This is why we specifically asked Ground News to sponsor this video.
17:30Recent stories about the increase in turbulence come from a 2023 study that suggested a link to climate change.
17:37Yet this study was barely reported on by the media, totally eclipsed by other major events.
17:42But Ground News lets you see the whole picture.
17:45You can easily compare the coverage and verify the source of the information.
17:49If you look closer, you'll see that some of the outlets, like the Independent and the SCMP, argue that climate change is making flying more dangerous.
17:56While others, like the Free Press, paint a different picture by dismissing the study.
18:01That's why it's really important to look at all the information.
18:04But Ground News doesn't only highlight breaking news on things like science and aviation.
18:10They also specifically show blind spot stories the media isn't covering.
18:14Veritasium is all about getting to the truth.
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18:47Get back in the junkies.
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