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.
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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!