Airplanes are mysterious things: unimaginably
heavy metal giants soaring through the sky, jam-packed not only with people but also all
kinds of electronic gizmos, and overhead bins stuffed with their oversized luggage – and
perhaps children. No not really. What confuses me the most however, is the
airplanes tires. Yeah really. I mean, look at them compared to the plane’s
body – they're tiny! How can they withstand all that weight and
speed? Okay, let's check out what's happening when
a plane is preparing to land on the runway. While still in the air, its speed is becoming
lower... and lower... That's when you might feel your ears getting
congested. You also sense that the plane has seemingly
started crawling at a snail’s pace, when just a second ago, it was moving at breakneck
speed. In their flight deck, the pilots are slowing
the plane down even more and getting ready to lower the landing gear (which is often
called the undercarriage). That's a complex mechanism that consists of
structural components, energy-absorbers, brakes, hydraulics, and, of course, the wheels and
tires. From your seat, you can hear a distinct robotic
noise - that's the landing gear and wing flaps being lowered. Then, when the airplane is about to land,
its nose starts pointing upward. If it seems counterintuitive, think about
water-skis. When a skier is moving across the water’s
surface, their skis are always inclined upward. Otherwise, both the skier and the skis would
go under the water. The same approach goes for planes: pilots
must point the aircraft nose toward the sky just before landing so that they don’t stall
the machine. Plus, exposing all that large surface area
on the wings and belly will help slow the speed of descent. Anyway, several seconds later, all 300 tons
of your airplane touch the ground while still going 170 mph. Imagine your typical 2-story house, fully
furnished, dropping to the ground as fast as a flying arrow - that must be quite the
impact! And STILL, those tiny (comparatively) little
tires don’t pop under the tremendous pressure? This incredible feat has to do with the materials
airplane tires are made of, the gas that fills these tires, and the way they're inflated. To make an airplane tire, producers use a
mix of different kinds of synthetic rubber. It makes aircraft tires so strong that each
of them can easily deal with a 38-ton load. “Um, didn’t you just say 300 total tonnage?” Hey good memory, yes I did, but remember,
there can be anywhere from 14 to 22 tires on one jumbo yet! They’re durable too – a plane can touch
the ground up to 500 times before its tires will need to be covered with a new layer of
rubber. But what makes tires so tough is mostly nylon
cords under the tread and special aluminum steel reinforcements. Then there’s the gas they have inside – it’s
not oxygen! At very low temperatures, oxygen can turn
into ice right inside the tires. Of course, the temperature must be extreme
for this to happen, about -360°F, but you never know with air travel! As for high temperatures (like during braking),
they can trigger a reaction between oxygen and rubber. When those two mix, the rubber becomes weaker. And nobody wants weak airplane tires - they
can explode! That's why the gas that fills aircraft tires
is nitrogen. It doesn't react with rubber, which makes
it a much safer choice for airplanes. It also doesn't leak through the rubber as
fast as oxygen does, meaning tires that are filled with 95% nitrogen remain inflated a
lot longer. And it's good news because in this case, wheels
need less maintenance which saves the airline's money! Now, the pressure in plane tires is 6 times
bigger than the pressure in your car tires. It's 200 psi (which stands for 200 lb per
square inch), and that's what you’d feel if you took a dive 450 ft underwater. Or rather, you WOULDN'T feel because the maximum
pressure a person can withstand is only 50 psi. But if we speak about airplane tires, such
high pressure makes them strong! It's next to impossible to overinflate a tire
to the point that it explodes. It's true that overinflating can reduce traction
and put more pressure on airplane wheels. But if a popped tire situation happens, it's
mostly because of the thing being underinflated. Even if it did happen on your flight, chances
are you wouldn’t even notice. Remember, there can be plenty of wheels on
large airplanes, like an Airbus A380 or Boeing 747. And if one of the tires fails, the plane will
still land safely. There’s one more reason why aircraft tires
MUST be strong and durable. When a plane touches the ground, its tires
aren't rolling at first - they're just skidding. In other words, the plane is dragging them
along the runway until it slows down enough for the wheels to be able to rotate. This is when you can see the tires smoking
after the touchdown - at this moment, they're accelerating to catch up with the landing
speed. This whole landing situation also led to tires
having grooves cut in them. If they had block patterns, like the ones
car tires have, these blocks would simply fall off as soon as the plane wheels touched
the ground. The most serious tire-wear happens exactly
when the rubber comes into contact with the runway. By the way, have you noticed how tiny and
skinny (compared to the huge fuselage) airplane tires are? Don't worry, they’re just the size they
need to be! Larger tires would be pointless since they
wouldn't make landing more effective or safer. But they would add extra weight. You probably know that the heavier a plane
is, the more fuel it uses, and the more money an airline loses. So, engineers try hard to make wheels as small
and, at the same time, as safe as they can be. After plane tires are produced, they always
get tested. Manufacturers create computer simulations
that check how tires will behave if they're pushed past their speed limit or get overloaded. They must be able to withstand pressure that’s
4 times stronger than their usual one and should cope with this situation for at least
3 seconds. As for the strongest tires, they shouldn't
blow out even at a landing speed of 288 mph! The same computer programs figure out how
tires will react to standard landings, takeoffs, and even taxiing, and then prototypes are
created. And still, airplane tires aren't entirely
safe from bursting. Accidents did happen in the past, and planes
did skid off runways because of one of the tires exploding mid-landing. There were also cases of tires bursting mid-air. If it's just an exploded tire, it's nothing
too bad. But tire fragments can get into the engine
or cause serious damage to the fuselage. That’s when the incident immediately becomes
more dangerous! Besides, when a plane lands with one or several
damaged tires, the load gets uneven, and it puts stress on the landing gear. In the worst-case scenario, all tires (even
good ones) might need replacing after such an incident. You can't argue that airplane wheels are cool,
but sometimes, they need additional help. I'm talking about hydroplaning - a situation
that occurs when the runway is covered with a layer of water preventing a landing plane
from braking and stopping in time. The aircraft just keeps skidding forward,
unable to find traction. (The same can happen to your car on a rainy
day, by the way!) That’s why some airports have grooves on
the runway. Water flows into these grooves, making the
surface not so slippery and dropping the chances of hydroplaning. Pilots claim that the difference between grooved
and non-grooved runways is dramatic. And all that sounds pretty groovy to me. Hey, if you learned something new today, then
give the video a like and share it with a friend! And here are some other videos I think you'll
enjoy. Just click to the left or right, and stay
on the Bright Side of life!
