Why Airplane Doors Stay Locked and How Planes Fly So High Safely

(brooding music) - Most plane doors aren't locked. There are no keys, no sensors or passcodes to secure them.

If someone wants to pull the lever, they can. - A man opened the emergency exit door and forced his way off the plane.

- And yet with 40 million flights each year, these doors are virtually never opened in flight. So, why not?

- Your self preservation, surely. - Common sense. - Most people are, you know, smart enough

to not mess with that. - The real answer relies on where planes fly. - How high do planes fly approximately?

- 10,000 km or is that overshooting it? - I think that's overshooting it. I think you'd be in space.

- 25,000 km. That's the height of a plane flying? - Is that way too low?

- It's too much. It's too much. Too much. Too much. Bring it down.

- Maybe yeah, 1,000 km? - 1,000 km, still space. - 50,000 ft, I think.

- Yeah, some of them can go up to 43,000 ft. - 30,000 ft. - 38,000 ft.

- Yeah. Why do they fly that high? Uhh...

- I don't know. Safety, I guess. - Probably to avoid collision with other aircraft and if there's high mountain ranges.

- I don't know, when storms or weather hit? - My guess is to avoid the turbulent weather. - I think that's a decent guess.

Now, it's true that one of the benefits of flying at 30,000 ft is a smoother ride. This is high in the troposphere,

the layer in which most weather occurs. So, there's less turbulence and fewer storms to navigate around.

But this is not the main reason that planes fly so high. The bigger reason, of course, is money. As you go up, the density of air decreases

and at 33,000 ft or 10 km, the density of air is just a third of what it is at sea level.

So flying at this altitude, the plane runs into a third of the air molecules it would closer to the ground.

That means the plane can fly about 73% faster for the same amount of thrust. And as a result, you get to your destination faster

and since you spend less time in the air, you burn less fuel. It seems in a way that like climbing is wasted energy.

Can you compare like the descent to the ascent? Do you essentially get the energy back as you fall down the other side?

- Yeah. When we climb, we burn about 80 kilos per minute. In cruise, we burn about 40 kilos per minute.

And in descent, it's maybe 10. So, it's almost negligible. - Not only that, jet engines are more efficient at altitude.

They work by compressing air at the intake, mixing it with fuel and igniting it. So, the combustion products are ejected very fast

from the exhaust nozzle. Now, this process is more efficient the colder the air is. And at altitude, the temperature

is around minus 50 degrees Celsius, which is a lot colder than an average of plus 15 here at the ground.

So, flying higher means you burn less fuel for less time and avoid the weather and associated turbulence of lower altitudes.

- The other reason you wanna fly high is to take advantage of the jet stream tailwinds and the company likes people who do that,

because you're burning less fuel, so it's less money. - But there is a problem with flying this high.

The air up there is unbreathable. If you were suddenly teleported to the top of Mount Everest, a height lower than planes fly,

you would remain conscious for only about three minutes. This is because in addition to density dropping with altitude, so does air pressure.

Air pressure actually falls off faster, because it depends on the weight of all the air above you. So at 10 km, the air pressure

is only a quarter of what it is at sea level. To be clear, the air is still 21% oxygen, but the partial pressure of oxygen,

the pressure exerted solely by oxygen molecules is around 5.5 kilopascals, which is a quarter of what it is on the ground.

Now at this pressure, not enough oxygen molecules can force their way into your blood in your lungs. To function normally, humans need an oxygen partial pressure

of at least 16 kilopascals. So, all the cabins of airplanes that cruise at high altitude must be pressurized.

A little bit of air is continuously brought into the cabin from outside. It actually comes in from the compression stage

of the jet engines. That is what maintains breathable air inside the plane. - The downside is that you are taking away

a little bit of the efficiency of the engines. - Now, pressurizing the cabin required a radical redesign of aircraft.

Before pressurization, planes would fly up to 10,000 feet or around three kilometers, where the partial pressure of oxygen is 15 kilopascals,

just at the limit of what people can handle. On these planes, doors opened outward and there wasn't much concern about the seal around them

since the pressure was the same on both sides. But once planes were pressurized, all the doors were changed to be the shape of a plug.

They're wider on the inside than the outside. That way the higher pressure inside the cabin pushes the door into its frame, creating an airtight seal.

How airtight is a cabin? - It's pretty airtight, but not completely airtight. So, you'll notice for example,

every time that someone flushes the toilet, you'll see some of the air pressure go down. So every time that happens,

you can actually see the cabin altitude jump a little bit. - And this is why plane doors and emergency exit doors don't need locks.

The difference in pressure between the pressurized cabin and the low pressure exterior is so great that no one is strong enough to pull the door inwards.

And if someone had come up and turned that while you're mid-flight? Nothing.

- Even modern plane doors that open outward are shaped like plugs. They're just cleverly designed.

The main passenger door on a Boeing 737 is both wider and taller than the frame it needs to pass through.

But when you pull the lever, gates at the top and bottom fold in, reducing the height just enough.

However, the sides are still too wide. So, the door first has to pop inside and rotate. It's that movement inwards that is impossible at altitude.

It would require a force equivalent to lifting 9,000 kilograms. And airplane cabins aren't even fully pressurized

to the sea level pressure of 101.3 kilopascals. You may have noticed this if you take a bag of chips on a plane.

It's easy to squish on the ground but as the plane climbs, the pressure in the cabin drops and the chip bag seems to inflate like a balloon.

I measured the pressure in my plane and at cruising altitude, the pressure dropped to 77 kilopascals.

Meaning the partial pressure of oxygen was only 16 kilopascals, the minimum required for people on the plane to feel normal.

This has some unintended consequences. Do you think you fart more in a plane? (interviewee laughing)

- If I did, I'd blame someone else. - I feel like no. - No.

- No - I can't let it rip, no way in the world. Do you think you fart more in a plane than on the ground?

- A hundred percent, no hesitation. Sure, I mean it's gotta do with the cabin pressure, right? - So as you go up, that cavity in here now expands

and the air wants to go somewhere, and the quickest place it can go is south. - Bag of chips just popped by itself.

- Now, the International Space Station is pressurized to sea level pressure, 101.3 kilopascals. So, why are planes pressurized

to the minimum extent possible to carry human passengers? Well, it's actually for a very good reason.

In 1988, Aloha Airlines 243 was en route from Hilo to Honolulu, Hawaii. The cabin was being pressurized as we've described,

but unfortunately, this plane's fuselage had a small crack and all of a sudden at 24,000 feet, the crack widened and the whole roof

tore off the front of the plane. Miraculously the pilots were able to land safely and only one person was killed.

The difference between the International Space Station and a plane is that the ISS was pressurized once and it stays pressurized.

But a plane experiences a pressure difference every time it climbs to cruising altitude. So, the fuselage is stretched

and then relaxed with every flight. Stretched and relaxed, stretched and relaxed. The Aloha Airlines plane

had the second highest 737 flight cycle count in the world, with nearly 90,000 in total. That's way more than it was designed for.

This led to fatigue, cracking, corrosion, and the eventual explosive decompression. So, planes are pressurized to the least extent possible

to minimize stresses and extend the life of the plane. But even 75% of atmospheric pressure should be plenty to prevent the doors from opening.

So, how did this happen in May, 2023? - A passenger panicked and actually managed to open an Airbus emergency exit in flight.

They were on final approach and they were quite close to the ground, so the pressure differential was very little.

And because of him using all of his force, he actually managed to get the door open, which was crazy and we didn't think that that was possible.

But if you want something bad enough, I guess it is. - Wow. Was he okay?

- He was okay. Everyone was okay in that case. - That was a pretty serious mishap. So, 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? When 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? And why do they get us to do that?

What is the reason? Is there a reason? - Obviously, they wouldn't ask you to do it if it wasn't for some benefit.

- I'm unfortunately a bit of a rebel and I don't follow the rules and yeah. - But you're not worried about taking the plane down?

- I'd make sure my parents have the airplane mode on so I can have it off. - I mean, yes I do because I don't want it interfering

with like the radio or whatever. - Well, I think it's the communication interference. - I feel like I've always been told

like it messes up like instruments, but honestly you're always just told to do it. So you know, just gotta put your phone in airplane mode.

- In 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. And out of caution, they banned almost all personal electronics on flights.

But airlines could test any device for interference and overrule the FAA ban to allow it on board. Any device, that is, except a phone,

because another organization has jurisdiction over phones and that's the Federal Communications Commission, or FCC. See a phone on the ground

with buildings and hills around it can usually only see one or two cell towers at the same time.

But from the air, it could see 10 or 20 or more. The concern was that 200 phones traveling at 800 kilometers per hour in a plane

could rapidly connect to many towers at once, overloading the infrastructure. At least that's what the FCC thought could happen.

So, they banned cell phone use in flight in 1991. (funky music) But there's a problem with this theory.

A plane is a big metal enclosure, essentially a Faraday cage. So, it should block almost all electromagnetic signals.

That's why plane antennas are located on the outside. Your phone signals can only escape through the windows, which means they go horizontally out the sides of the plane.

So, they would have to travel long distances before reaching the ground. And the cell towers your phone is trying to connect to,

well they are tilted downwards, you know, to collect all the signals from people walking around on the ground.

So, it's very hard to make a connection from the air unless you're flying really low. So, phones could only conceivably disrupt ground networks

during takeoff or landing. And the FCC never even tested if this was the case. In 2005, they went before Congress and said

the rule banning 800 MHz cell phone use in flight may not be needed in order to protect ground-based cellular networks.

As far as we know, a mobile phone has never caused an air accident. All airplane mode does for sure is save your battery life.

So, why are these rules still around? - I've been flying myself and where I've gotten interference,

you know, when you're talking to a traffic control and you get that (imitating a phone signal), you know that signal,

and that is because someone is either using their phone or the phone is on. Will one phone in an aircraft cause any problems?

Probably not. Will 200 do something? Maybe.

Rather than taking the chance of like, let's everyone update their Twitter profile at 500 feet, rather 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. - But airplane mode might soon be a thing of the past.

The EU actually no longer requires it and is pushing for airlines to provide 5G service on all EU flights.

So, we may eliminate that inconvenience, but we still have to deal with airplane food. What do you think about airplane food?

- I only eat the bread rolls. That's only thing I can handle. Apart from that, everything tastes like mush.

- It's can be very good. It can be very terrible. - Eh, bland-ish, different consistency. - Do you think the food tastes as good in a plane

as it would on the ground? - No. - But bad-tasting food might not be all the airlines' fault.

See, the air that's pumped into the cabin altitude is really dry. And the Sahara Desert for reference

has an average relative humidity of 25%, but inside an airplane cabin, it can be as low as 5%. This can dry out your nasal passages,

hindering your sense of smell and therefore taste. The lower cabin pressure can also decrease sensations like the intensity of salt and sugar.

But there is one flavor that appears to be enhanced in flight. What do you drink in an airplane?

What's your drink of choice? - Apple juice. - Apple juice?

- Yeah. - Interesting. - I mean Coke, that's default

- Orange or apple juice. - Gin and tonic. - Maybe a Bloody Mary, but...

- You're the first one today. - Really? - Yeah.

A German survey of a thousand flyers found that more than a quarter of them order tomato juice in flight.

And what's really weird is that 23% of those people would never drink it on the ground. And would you drink Bloody Mary,

would that be like a standard drink at the bar or is it a special plane drink? - I only have it on planes.

- So, why is everyone ordering tomato juice? Well, it could be because of the noise. A 2015 study points to the chorda tympani,

a nerve that carries taste information from the tongue to the brainstem. It runs right past the eardrum,

between the tiny sound conducting bones. So, loud cabin noise might unintentionally stimulate it. This could produce an audio illusion

that boosts our sense of umami, the savory taste you find in MSG, soy sauce, and well, tomatoes.

- I always drink tomato juice and I never knew why. It just felt like my plane drink. Or like spicy tomato juice-

- Yeah. - Like both of those are favorites of mine. - Yeah.

So, next time you're on a flight, go for something extra sweet or salty or maybe try the tomato juice.

I feel like with how much people fly, our perspective of flying is still pretty distorted.

So, why is that? - Yeah. I know that we talk a lot about accidents and incidents

and we dig into them really, really deep and people might ask, "Why would you be doing this? Doesn't that just make people even more afraid of flying?"

But the fact is that this is one of the prime reasons why aviation is as safe as it is. The fact that we have hundreds of professionals

that dig deep into these accidents means that we learn from them. So, every flight becomes a little bit safer.

That's actually a big reason that I started my channel Mentour Pilot in the first place 'cause I promise you, the more you know

the safer you'll feel. (closing music) - Do you think that climate change increases turbulence?

- Eh, depends on what people think about their opinions. - Yeah. - It's been a bit of that in news recently, hasn't there?

- Today, the media tends to prioritize sensationalized headlines over key details. Part of why airplane mode is still such a big deal today

is because of the media frenzy it started in the 1960s. So it's more important than ever to look at all sides of the story.

This is why we specifically asked Ground News to sponsor this video. Recent stories about the increase in turbulence

come from a 2023 study that suggested a link to climate change. Yet, this study was barely reported on by the media,

totally eclipsed by other major events. But Ground News lets you see the whole picture. You can easily compare the coverage

and verify the source of the information. If 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. While others like the Free Press paint a different picture

by dismissing the study. That's why it's really important to look at all the information.

But Ground News doesn't only highlight breaking news on things like science and aviation, they also specifically show blind spot stories

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