An illustration of engine failure during a flight |
An illustration of pilot loosing control over the plane whose engine has failed |
John Staughton
Most multi-engine planes can
fly for hours with a failed engine, although the plane’s altitude and
navigation may need to be adjusted.
If all engines fail, or all but
one engine fail on a four-engine plane, the situation is more dire, but skilled
pilots can still avert a tragedy even in those extremely uncommon scenarios!
Action movies are filled with
drama, suspense, action and danger, all of which are only heightened when the
events are happening at 30,000 feet!
While Hollywood blockbusters and
superhero movies may make it seem like flying in planes is a risky venture,
there are countless safety protocols and contingency plans if something
unplanned happens mid-flight — even if an engine fails!
While the idea of an airplane
engine not working sounds terrifying, engine failure is surprisingly common,
and there are numerous strategies and solutions to keep every passenger safe.
In some cases, the passengers
onboard don’t even know when an engine fails, although the pilots and crew
certainly will!
So, how does a 200,000-pound metal
tube manage to stay in the air if one of its engines fails?
The Physics of
Flight
Without going into too much detail,
it will be helpful to have a brief refresher on the physics of flight before
explaining the function of an engine — and the dangers when one fails.
Although we typically think of an
airplane as a single flying unit, the two key components are the engines and
the wings, both of which serve very different purposes.
At the simplest level, air is drawn
into an airplane’s engine, where it mixes with fuel and burns at a controlled
rate.
This air/fuel mixture expands,
which pushes on a piston, thus turning a crankshaft and propeller.
The pistons inside each cylinder
will build up force through a cycle of four steps — intake, compression, power
and exhaust.
An airplane’s engine is designed to
propel a plane forward at a very fast speed, but that isn’t the reason that a
plane can fly.
After all, plenty of things can fly
without an engine, such as a glider, or a paper airplane.
Once the engine(s) are propelling
the plane forward at a rapid rate, air is also rapidly moving over the wings.
The curved nature of airplane wings
is specifically designed to generate lift, the force that
keeps the plane in the sky.
As a wing moves through the air, it
deflects air above and below, thus affecting the air pressure.
The curved upper part of the wing
will lower the air pressure above it, while the flat lower part of the wing will
increase the air pressure below it.
This difference in pressure and
subsequent air speed is what allows a plane to move upward, whereas the engine
is what enables the plane to move forward.
What Happens When
An Engine Fails?
An engine failure sounds like a
catastrophic problem to have while cruising at 30,000 feet, but it doesn’t
necessarily mean a tragic crash.
In fact, there are about 150-200
accidents or incidents per year as a result of engine failure, but out of an
estimated 50 million flights per year (domestic, private, military etc.), those
are rather safe odds.
Engines can fail for a large number of reasons, such as
mechanical problems inside the engine, damage to the turbine or propellers, an
oil leak, fuel contamination, or even a foreign object entering the engine,
such as a bird!
While such failures are infrequent (as mentioned, about
1 in a million), pilots and flight crews must be properly trained to handle the
situation calmly and safely.
Interestingly enough, if a single engine fails, it isn’t
treated as a serious emergency, because it’s a very manageable problem.
On a four-engine plane, such as a Boeing 747 or an
Airbus 340, passengers may not even be informed of the problem, since the other
engines are more than capable of picking up the slack, per se.
In a two- or three-engine planes (i.e., Boeing 737 and
Boeing 727, respectively), losing an engine is also not an immediate emergency,
as some of these planes can manage to fly for 5-6 hours on a single engine.
Landing at an airport with adequate facilities to fix
the problem is often the goal in such situations, rather than making an
emergency landing at the first available airstrip.
While an engine failure is not a death sentence for
passengers onboard, it will require some adjustments from the pilot.
Losing an engine means that the plane’s maximum power will
be reduced, so the remaining engine(s) will be engaged to make up the
difference.
This will create an asymmetric force, causing the plane
to turn away from the functioning engine. If this isn’t compensated for by the
pilot through the use of rudder pedals, it can cause a loss of balance and
control of the plane.
Additionally, the decrease in power and airspeed means
that the plane will not be able to stay in the thin atmosphere of 30,000+ feet.
If the plane isn’t able to move fast enough, the thin
air higher up in the atmosphere won’t be able to sustain the lift.
A pilot can drop to a lower altitude, but will have to
do this quickly, typically decreasing to 15,000-25,000 feet, where a single
engine can sustain even flight.
Landing will also be a bit more of a challenge, as the
plane’s ability to abort a landing will be impacted.
For this reason, pilots need to carefully consider the
type of airport and the length of runways available if they need to change
their destination.
Finally, some of an airplane’s systems are powered by
the engines, so if one fails, there is a chance that it could affect the
hydraulic or electric systems.
There are often redundancies for these types of systems,
meaning that the other engine can take on the extra tasks, but some
non-essential systems could be compromised in the case of an engine failure.
As a passenger, it would be pretty terrifying to hear
that an engine has failed, but planes are designed to function safely with
fewer engines than it actually has.
In some cases, a pilot may even cut power to one or more
engines to perform an idle-glide, a means of letting the engine systems restart
or reset; you might not even notice this has happened, aside from the decrease
in engine volume from outside the aircraft!
What Happens If
All the Engines Fail?
First of all, the chances of
multiple engines on a plane failing in the same flight are incredibly small.
Most engine problems are rare to
begin with, and aren’t a systemic problem, but rather an acute issue in a
single engine (i.e., a fuel leak or a bird flying into the propellers).
However, if all the engines do
fail, it is definitely an emergency situation, yet still not one that is
impossible to overcome.
The same forces that allow an
airplane to fly will allow an airplane to glide without additional power.
The lack of forward thrust will
have to be replaced by losing altitude (as a form of energy), but this doesn’t
mean falling like a rock out of the sky.
By adjusting the wings and rudders,
a commercial plane can have a lift to drag ratio of 10:1, which means that for
every ten miles the plane “glides” forward, it will lose 1 mile in altitude.
In the case of an average
commercial flight at 30,000 feet (approx. 5 miles), the plane could glide for
50 miles without any engine power.
The plane will still be able to
turn left and right, and remain steady, but will no longer be able to pull up
or increase in altitude.
In the extremely unlikely event of
this happening, the pilot can hopefully find a runway in the glide range, or at
the very least, a relatively even stretch of land or body of water.
This was the situation for the
miraculous landing of US Airways Flight 1549 back in 2009, when both engines
failed after the plane encountered a flock of geese.
As stated before, this type of dual
engine failure is incredibly rare, perhaps only happening once per decade
somewhere in the world.
A Final Word
Flying can be a stressful
experience for many people, but even in those rare cases of engine malfunction
or failure, well-trained pilots and professional flight crews can handle the
crisis.
With redundancies and safety
protocols in place, adjustments to altitude and navigation can quickly be made,
so while the passengers won’t necessarily get to the airport they were heading
towards, they’ll be safely returned to the ground!
John
Staughton is a traveling writer, editor,
publisher and photographer who earned his English and Integrative Biology
degrees from the University of Illinois. He is the co-founder of a literary
journal, Sheriff Nottingham, and the Content Director for Stain’d Arts, an arts
nonprofit based in Denver. On a perpetual journey towards the idea of home, he
uses words to educate, inspire, uplift and evolve.
https://www.scienceabc.com/eyeopeners/how-can-a-plane-still-fly-if-an-engine-fails.html
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