Do you get a little nervous before a flight? If you do, you’re not alone. Between 33% and 40% of people feel some form of anxiety when they board a plane.
While a giant metal object, flying through the air stuffed with people and cargo sure sounds precarious, planes are actually pretty steady. Not convinced? Let’s do an experiment. Here we have a Boeing 777. It’s a full flight. And we’re going to make all 500 passengers jump at once.
How much force would that exert? What is natural frequency? Why are sandbags used on a plane?
You are one of the 500 passengers on our Boeing 777. It happens to be the flight captain’s birthday, and the flight attendants want to pull a little prank.
They whisper the plan to everyone as they pass out complimentary snacks. You’re a little unsure of this prank, but hey, everyone else looks unphased. What’s the worst that could go wrong?
Balanced weight is extremely important for the safety of an airplane. An improperly loaded plane can be dangerous.
It’s not just too much weight that you have to worry about, but also too little.
When planes don’t have enough passengers and cargo, people have to be moved around the cabin to properly distribute weight. Sometimes, a flight crew will even have to add sandbags, weighing 23 kilogram (50 lb)
So what happens when a bunch of weight is displaced for just a second? Well, let’s get back to our flight and see.
The airplane has reached altitude and the seat-buckle light turns off. All the passengers, including you, rise from their seats.
The tallest people make their way to the aisle where there is a little more head room. You place your hands on the head rest of the seat in front of you to stabilize yourself.
The flight attendant gives the signal and everyone jumps. As people’s bodies leave the floor of the cabin, the plane loses 37,500 kg (82,500 lb) of weight. Because the plane is lighter, it will rise in altitude as passengers leave the floor.
Together, you and the other passengers exert the force of about 10 elephants, or 800 people. This sudden push of weight changes the plane’s trajectory and the captain loses control as the plane nosedives to your untimely death.
Wait, that doesn’t sound right. This sudden push of weight changes the plane’s trajectory, and, nothing really happens.
Because the plane is traveling at around 870 kilometers per hour (540 mph), this collective jump only created a minor change in trajectory. The captain can easily adjust, though he might be a little annoyed at all his pesky passengers.
Now, this is assuming that all 500 passengers have an average out to around 75 kg (165 lb) for a total weight of 37,500 kg (82,500 lb). It would be a different story if it was a flight full of 500 sumo wrestlers, who can weigh up to 200 kg (440 lb).
It would also be a much more dangerous stunt to pull during take-off or landing. The plane has a much lower velocity during those moments, which means that the shifting of weight could have a more drastic effect on the trajectory. And the captain might not be able to correct in time.
Now, if everyone decided to continue to jump in sync, and at a quick enough pace, you could create an unstable condition called flutter. This vibration originates from the airplane, causing unsteady aerodynamics which affects the natural frequency of the plane.
Natural frequency is the set of frequencies that an object vibrates at when hit. If the vibrations from passengers continuously jumping caused flutter, then the structure of the airplane could fail and you would drop out of the air.
But the coordination of this would be near impossible, so it’s not something you really have to worry about. Despite many people’s anxieties, flying is actually very safe. Airplanes are safer than both trains and cars.
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