Name: 航空宇宙工学の教授だけど「航空機」について質問ある？| Tech Support | WIRED Japan
Uploaded: 2025-02-27T09:00:06.000Z
Duration: 16 min 22 s
Description: 【看影片學英語】數萬部 YouTube 影片，搭配英漢字典即點即查，輕鬆掌握單字發音與用法，長久累積看電影不必再看字幕。

I'm Bill Crossley, Professor of Aerospace Engineering, and I'm here to answer your questions from the internet.

Yeboi Nath asks, Why do commercial planes fly at 35,000 feet?

So at about 35,000 feet, the air has less density, which means less drag, so you need less thrust to push the airplane through the air.

However, the higher you get, the less density there is, the less thrust the engine can produce.

So we try to balance the thrust the engine can produce with the drag on the airplane and try to find the best cruise altitude.

Onion Time E says, As a planologist, I have the know-how to explain the difference between models.

For example, a 747 is 10 more planes than a 737.

So Boeing started with the 707, did the 727, then the 737, 747, 767, 777, and then 787.

Some people think the number of the model means a bigger airplane.

It's just the order in which they came to market.

How does g-force work and what causes a pilot to pass out?

So when you're flying in an airplane and the pilot pulls back on the stick to make the airplane go up, the people and the pilot sitting inside the airplane want to keep going in the same direction, but the plane pushes up on them.

So while the plane is pushing up, all the blood is going to rush down, and that's what the g-forces are.

How much that force is, number of g's, is relative to gravity.

So I'm sitting here in my chair, it's one g.

The pilot pulls back a little bit, maybe it's two g's max you'd ever see in a commercial airplane.

Fighter pilots sometimes pull four, five, even six g's.

That's what causes them to black out is when that blood is running out from their brain into their feet and their legs.

There's g-suits that actually squeeze their legs to help keep the blood up in their head.

And some pilots even learn tricks to grimace and scrunch themselves up to keep from passing out when they do high g maneuvers.

Next up, Sentient Sadist says, Don't try telling me that statistically airplanes are safer than cars.

Well, statistically they are safer than cars.

The chances of you having a fatal accident in an airplane is something like one in 120 million trips, which is far safer than traveling by car or any other means of transport.

Aviation has gotten safer and safer every single year.

We've gone from having a couple of fatal accidents a year to recently having one every couple of years.

There's been a huge improvement in safety.

One of the reasons that they're safer is because the aviation industry, we've got two trained pilots that have gone through lots of training on board.

The aircraft have to be certified and are redundant systems, multiple things.

So if one system fails, other ones back them up.

And the whole air traffic management and inter-transport system is set up so that we know where the airplane is at all times and it's staying away from other airplanes.

So from a non-statistical point of view, all that extra stuff we do for aviation makes airplane flying safer than driving your car.

Oof Doof Oof Oof asks, What happens when there's a bird strike?

Depends on how big the airplane is and how big the bird is and the relative mass of the two objects.

Bird strikes have caused aircraft or helicopter windows to break.

They sometimes get ingested into engines.

We actually design the engines to handle a bird ingestion.

One of the bird strikes that's probably most famous is the Miracle on the Hudson, where the Airbus ingested lots of geese into the engine.

So both engines went out and Captain Sullivan landed it on the Hudson River safely.

I still don't believe that airplanes can fly.

I understand the science of it, but how can the wings generate that much lift?

The simple answer is the shape of the wing, the speed of the airplane, and the angle of attack of the wing change the momentum of the air going past the airplane.

It pushes down on the air and the airplane pushes up.

Creighton RSS asks, can a plane fly within one engine?

Actually, the way aircraft are designed, if you have more than one engine to be certified, they all have to be able to operate with one engine out.

There's an interesting thing you've probably noticed in commercial aviation.

Most of the airplanes operating today, commercial aircraft, only have two engines, even the ones flying across the ocean. 747 had four engines.

That was because if one engine went out, you needed the three engines to get all the way to your destination or to come back to somewhere safe.

As engines have gotten more reliable and more efficient and bigger, we're able to make aircraft with just two engines that can operate with one engine if one goes out to make it to a safe destination if one of the engines goes out.

TangerineMaximum2976 asks, why is commercial aviation not improved in the last 50 years?

I think one of the things that if you're looking at the airplanes, the airplanes don't look a whole lot different, but they have been improved a huge amount.

The engines they use are much more reliable.

We've moved from having multiple engines for trans-oceanic flights to having two engines for trans-oceanic flights.

The electronics on the airplanes are much, much smaller and much more reliable, and so that makes the airplanes lighter.

Our impact on the environment, because the airplanes are lighter and the engines are more efficient, has gone down a huge amount in the last 50 years.

When the airplane flies over you on approach to the airport, you hear it, but it's not the roar you used to hear from the older turbojet engines that look like skinny cigarettes underneath the wings.

Now we get the big, fat turbo fans, which are much quieter.

So commercially, aviation has improved a huge amount in the last 50 years.

The part about the air passengers' experience, that's not the aerospace engineer.

That might not have improved much in the last 50 years.

Next up, RGB says, What if airplanes were made of the same material black boxes are?

Since black boxes generally survive plane crashes, the plane might be intact too.

The black boxes are made of really strong material, but the really strong material is really heavy.

And as aerospace engineers, we have to figure out what's the right material to be strong enough to do everything we need it to do and be reliable enough to make many, many flights over its lifetime, but also be light enough for us to pick it up off the ground.

Aircraft designers have settled on aluminum and composite fiber-reinforced plastic are the two main things that aircraft are made of these days.

HSN407 asks, Can I ask a flight attendant to change to an empty seat?

There's all kinds of reasons why you might not be allowed to.

Airlines often use the different seats to generate revenue, so you might not be able to move to a seat you didn't pay for.

On some airplanes, if there's not a whole lot of passengers on them, if you move to a different seat, you change how the weight is distributed in that airplane, and the pilots want you to be in a certain spot so the aircraft is easy to fly and stay safe.

Viper says, Hey, Aviation Twitter, I have a question for you.

If both the pilots of a commercial airplane are compromised, can't air traffic control take remote control of the aircraft?

The answer today is no, they can't, because they don't have the equipment on board.

But actually aerospace engineers have been working for quite a while to fly airplanes that have a lot of autonomous operations and are remotely piloted.

The military regularly flies the Predator and Global Hawk without a pilot on board.

The pilot or operator sits well off, and they can do that.

To put this into commercial airlines would require a huge amount of upgrade to the equipment, and it'd be just an expensive endeavor at this point, not to mention the certification issues.

Some new entrants in urban air mobility are pushing really hard at having more autonomous or perhaps even autonomous flights around a city where you don't have a pilot on board.

NowMinox asks, Is severe turbulence really safe?

At least from an airframe point of view, from the aircraft point of view, most of the turbulence will be rapid up and down accelerations.

And so the airplane may drop and may climb during the turbulence, but it's usually you're so high in altitude, it's not going to throw you into the ground from a cruising altitude.

There is a concern about something called wind shear.

If you encounter that as you're coming close to an airport, that can actually push the airplane down.

And there was a really well-known accident at Dallas-Fort Worth when an airplane hit this wind shear, and it actually crashed short of the runway.

We as an industry have put in sensors and better meteorological devices to make sure we're measuring, so that if that's going on around the airport, we don't fly into that.