[Narrator] Every time a plane lands,
each tire leaves around
one and a half pounds of rubber on the runway.
Tires are stationary until touchdown,
when sudden contact with the ground
causes friction,
quickly bringing them up to speeds
of more than 150 miles per hour
and producing temperatures
around 500 degrees Fahrenheit.
That temperature makes the tread rubber melt
and bond to the runway
and lights that guide pilots.
The Airbus A380 is the largest passenger plane
in the world and it has 22 tires.
That's over 30 pounds of rubber lost per landing,
equivalent to the amount of rubber
in two of your car's tires.
So how does all of that rubber get removed,
and what's so dangerous
about it building up on runways?
- [Mohammed] There is two things
you need to consider when we're talking
rubber removal from the runway.
There's the rubber removal
from the actual tarmac itself,
but the other process is to remove the rubber
from the lights.
- [Narrator] At London's Heathrow Airport,
where Mohammed works, an average of 650 planes
with 10 tires each touchdown every single day.
That's 10,000 pounds of rubber daily.
A buildup in rubber
can make the surface of a runway smooth,
decreasing the friction needed to land.
This can impact braking and control
and increase the risk of hydroplaning
in wet conditions.
And runway lights used to guide takeoff,
landing, and taxiing, especially at night
and in low visibility conditions,
are dimmed by the melted rubber bonding to them.
Within the United States,
the Federal Aviation Administration recommends
that rubber deposition be checked weekly
for any airport with at least 210 daily landings.
The process for checking rubber buildup
isn't as simple as checking for skid marks,
and it requires the use of specialized
tests and instruments.
- So for the runway, we have something
called the friction test.
It's like a machine that has a wheel
and someone will drive down the runway
and that wheel will come down
and it'll actually measure
how much friction there is on the runway.
The key to our runway is you want it
to have a lot of friction.
You don't want it to be slippery at all.
So that measurement of how much friction
that wheel feels on the surface of the runway
will tell our teams when to go out there
to remove the rubber.
Now, to do that, we have specialized machinery,
which is like a massive truck
with a Hoover on top of it.
And so it's high pressure water, basically,
but very hot and it blasts the tarmac
and then it just sucks up
everything that comes off it.
- [Narrator] And then there's removal
of rubber from the lights.
Landing technology alone isn't enough
for pilots to bring planes in safely.
- Of course, they use ILS systems,
they use the Instrument Landing System,
when coming into land,
but they still need a visual reference.
So from a safety perspective,
the pilots physically
won't be able to see those lights.
And I once spoke to a pilot
who was flying in from Scandinavia.
And I remember I always go to the pilots
and speak to them about this stuff afterwards
because I want to get their perspective.
And I said to him, "What's it like to fly a plane
at an airport and land a plane at an airport
which doesn't maintain its lights very well?"
He said, "It's like trying to fly a plane
into a black hole."
So for the lights themselves,
we do a test where we measure
how much light output comes out of the lights.
So we have this trailer
that hooks on the back of a car
and the sensors on the back of this trailer
will tell you exactly how much light
is coming out of every single light.
And then you get all that data and you can tell
which lights have rubber on them.
So the lights are really important
and they need to be bright.
So to do that, we have another machine,
which uses dry soda and it has somebody
on the back of the lance and they go
from one light to another
and they point this thing at it
and they shoot powder, this soda powder,
at the actual lens of the light
and they get rid of all the rubber
that is on those lights
- [Narrator] From when the last plane
takes off at night
to when the first plane takes off in the morning,
there's a small window of time.
- Our runways need to close, so we need to wait
until the last plane departs,
and then after the last plane departs
that's when our teams can come on.
So if you wanted to clean
every single light on the runway,
you can't really do it all in one night,
because there's that many of them.
So for the lights themselves,
we remove it at least twice per week.
This is something that people
don't ever really think about
but there's a whole team of people
whose responsibility is to make sure
that these runways are cleared.
And actually, people benefit from this job
all the time because the only way
that they're able to go on holiday
and enjoy the world is by using
these strips of tarmac called the runways.