Ok fellow air-travelers, I got a question for you!
What’s your favorite time during a flight?
The take-off, the landing?
Or maybe the moment your plane climbs just above the clouds?
Ahh, the view is magical.
But have you ever wondered what would happen if your plane starts to climb even higher?
Well, it's time to get some answers.
But first, please drop a comment below and let me know if you'd ever want to fly at higher
altitudes.
There are 3 main reasons why planes fly as high as they do.
One has to do with of course, saving money.
The higher it flies, the faster it goes, and the cheaper it is.
Air molecules are responsible for that.
When a plane flies higher, less air is pushing down from above – therefore the air molecules
spread out more, decreasing the air’s density.
(Boy I wish someone would decrease my density!
) When an aircraft flies through less air molecules,
it needs to adjust its speed in order to get enough air and lift itself.
A lack of speed and air can cause the plane to end up in a dangerous stall.
(No, not the kind of stall with wild horses in it, the other kind.)
But I’ll come back to that in a bit.
That’s when knots come into play.
(Actually you don’t play with these kind of knots like on a rope.
Heh heh).
Here, a knot is the unit used to measure wind speed.
Imagine you’re climbing right above 4,000 feet.
You can see in the meter that the airspeed is 250 knots.
When you reach 38,000 feet and you check the airspeed again, it’s still 250 knots.
But when we check the true airspeed of the plane - which measures how fast air is going
through the engine, it’s up to 450 knots.
So, when the plane travels rapidly at higher altitudes, it consumes less fuel while taking
you to your destination faster.
It’s a win-win.
Another reason is comfort.
Jet airliners usually fly at 35,000 to 42,000 feet.
The weather that we experience every day is active from the ground up to approximately
35,000 feet.
– Do you see where this is going?
All the turbulence, clouds, rain and bad weather in general, stay below the plane’s altitude,
so we can enjoy a smooth, non-eventful flight.
The last and most important reason is everyone’s safety.
Let’s say that the plane is at 39,000 feet, and suddenly something happens to the engines.
Pilots have more time to fix the problem and communicate with the controllers before they
make an emergency landing.
All modern aircraft have an excellent response when there’s an engine failure.
Most of us think that if an aircraft loses its engines, it’ll drop like a pin falls
onto the floor.
Fortunately, that’s not how it works.
When an aircraft loses an engine, it’ll glide.
For each meter it drops, it moves 53 - 56 feet forward.
During that period, pilots have plenty of time to get closer to an airport and perform
an emergency landing.
So, now that we know flying higher is more relaxed, more economic and safer, wouldn’t
it make more sense if an airliner flew even higher and faster?
Well, it’s a bit more complicated than that.
As I told you earlier, the airspeed of the plane will increase as the air molecules drop.
One of the main reasons a jet can’t fly higher is because there won’t be enough
air flowing through its engine.
Think of a real person visiting Mt. Everest.
The higher they climb, the less air they get into their lungs.
Without enough oxygen, the human body can’t function.
The same principle applies to the aircraft engine.
It needs enough oxygen to get mixed up with the fuel molecules to burn and produce thrust.
When the air density decreases, the engine thrust does the same.
Re-imagine the first time you boarded a plane.
When that beast was on the ground, you could hear its engines over-working.
But, when the same aircraft climbs above 35,000 feet; the engines barely produce enough thrust
to maintain the plane’s altitude.
Temperature can also be a problem.
When it’s a good 77° on the ground, it can drop down to -60° at high altitudes.
And with the temperature lowering, the speed of sound gets impacted as well.
So, the true airspeed comes to stir things up.
When both the speed of sound and temperature drop in high altitudes, the true airspeed
will increase.
And at some point, they’ll meet.
That’s what pilots call the coffin corner, and it’s as dangerous as it sounds.
If a plane reaches that point, and it decelerates, it’ll go into a low speed stall.
If it goes faster, it’ll end up in a high-speed stall.
Neither of those are safe.
All aircrafts have a critical Mach Number – which describes the speed of an object
approaching the speed of sound.
When that Mach number is reached, the airplane travels at supersonic speeds – and it can
break the sound barrier.
Planes usually fly at around Mach 0.7 or 70% of the speed of sound.
If an aircraft goes faster than that, it can cause shockwaves to form.
These shockwaves, in turn , will create a huge drag at different parts of the plane.
This can result in pushing the nose of the plane upwards.
If all these events happen in the coffin corner, it’ll break the aircraft into pieces.
That’s one of the reasons why pilots aren’t allowed to take the aircraft past their designed
Mach rate.
Granted, there are some planes intended to reach supersonic speeds, but they were created
for research and military purposes.
At certain altitudes, an aircraft has a minimum speed limit and a maximum speed limit.
In order to be safe, aviators fly the plane approximately 600 feet below its maximum altitude.
Though, sometimes, the unexpected happens; and pilots should know how to handle those
situations when a plane reaches either of those points.
Let’s say that an airliner flies at a higher altitude but lower speeds - which is a rare
occurrence.
But for the sake of the argument, let’s assume that the pilots are playing chess and
not paying attention.
The plane won’t start to lose speed on its own, but if there’s a problem with the throttle
or it fails, then it’ll begin to slow down.
The first thing that’ll happen is that the aircraft will warn the pilots using voice
commands and loud alarms.
Then the pilots will need to act immediately.
As the aircraft goes slower, the drag increases.
The slower the jet goes, the more thrust it needs to be controlled.
As the drag continues to rise, the plane could reach its maximum safe velocity, and everyone
on the jet will feel the impact immediately.
The airliner will start to shake, the wings of the plane will begin to stall, followed
by alarming turbulence.
The pilots need to act fast.
They should be able to identify the stall and get the plane out of it.
During that time, the airplane’s nose is lifted, and the wings are going against the
wind at an angle.
That can cause them to break.
First, they need to disengage the autopilot.
This will stop it from correcting the position of the plane.
Then, they’ll begin to lower the nose of the plane downwards.
While doing so, they add a little thrust to the action.
When it’s lowered enough, they add a bit more thrust to help the plane go faster.
Part of their training is to do these things slowly and steadily to avoid having a second
stall.
When it’s all done, the pilots will have full control of the plane, and they can continue
playing chess.
Hehe But the way they save a plane when it’s
approaching supersonic speeds is a whole different story – and this is actually a bit more
common.
Let’s say that an aircraft is flying over the Alps.
The change in temperatures impacts the airspeed.
The plane will again alert the pilots, but depending on the situation, they most likely
won’t disengage the autopilot.
Then, they’ll partially apply the brake.
While doing so, they’ll make sure they don’t go all the way to idle, because the low airflow
can cause the engines to stall for a whole minute.
So, they slowly bring the thrust back a little bit, and gradually raise the air brakes.
Everything is done in slow movements, because a sudden change can cause shockwaves that’ll
roll the plane.
Then the pilots make sure that the plane speed is decelerating, and at the same pace, they
lower the air brakes.
So guys, now you know how to fly a plane.
Heh.
All kidding aside, high altitudes, speed, and the coffin corner play a huge role in
our safety.
Now we have a clear understanding of how pilots might be saving everyone’s life during a
flight without even realizing.
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