They seem to be so small and unstable, thinking about the weight of the airplane, especially filled with passangers and luggage. How do they carry the weight, as well as being able to accelerate and break and everything?
In: 1057
Planes aren’t designed to be on the ground. That is why they look off and wobbly when taxiing. They have to land, so they have ground equipment, but they are built for flying. A happy plane is an airborne plane.
Planes are light relative to their size. For example an average passenger plane like an Airbus A321 weighs less than a battle tank. They’re designed to be as light as possible for their size because that enables them to carry heavy loads. Their wheels may appear small relative to the rest of the plane but they’re probably the hardiest parts of the whole aircraft. They can take the repeated abuse of take off and landing which produce immense forces. They use hydraulic shock absorbers much like cars but they’re turned up to 11. They’re very thick, very sturdy, and their tires are rated for extreme loads.
They may look small but they’re not.
They must carry the weight. They do not need to be able to accelerate; the engines push air. Braking is a “nice-to-have.” Cornering ability at anything much above walking speed only needs to be sufficient to navigate the turns on a, um, runway.
So the main requirements are:
– holds the weight of the airplane
– withstands spinning at full takeoff speed
– has *some* traction
That’s basically it. The main question here is about weight.
It’s not actually the tires that hold the weight. It’s the air inside the tires. The tires simply hold that air in place.
Let’s say you have a plane that weighs 200,000 pounds. A 757, say. If your tires are inflated to 200 psi you’ll need a total “contact patch” of 1000 square inches between all the tires. That sounds like a lot but there are ten tires. Each one needs 100 sq in or about a ten inch square of contact patch, at high air pressure, to hold that weight. That’s pretty doable.
You want the smallest and lightest tires that can hold enough pressure to support the weight. Rather than going with monster tires, you generally add more tires. (A little Cessna has 3 tires; a 737 has six; a big 747 has eighteen tires.) The goals being, the tires need to be compact enough to stow inside the plane and light enough to carry, yet strong enough to land on. The best tire for the job is not the biggest!
They must carry the weight. They do not need to be able to accelerate; the engines push air. Braking is a “nice-to-have.” Cornering ability at anything much above walking speed only needs to be sufficient to navigate the turns on a, um, runway.
So the main requirements are:
– holds the weight of the airplane
– withstands spinning at full takeoff speed
– has *some* traction
That’s basically it. The main question here is about weight.
It’s not actually the tires that hold the weight. It’s the air inside the tires. The tires simply hold that air in place.
Let’s say you have a plane that weighs 200,000 pounds. A 757, say. If your tires are inflated to 200 psi you’ll need a total “contact patch” of 1000 square inches between all the tires. That sounds like a lot but there are ten tires. Each one needs 100 sq in or about a ten inch square of contact patch, at high air pressure, to hold that weight. That’s pretty doable.
You want the smallest and lightest tires that can hold enough pressure to support the weight. Rather than going with monster tires, you generally add more tires. (A little Cessna has 3 tires; a 737 has six; a big 747 has eighteen tires.) The goals being, the tires need to be compact enough to stow inside the plane and light enough to carry, yet strong enough to land on. The best tire for the job is not the biggest!
Planes aren’t designed to be on the ground. That is why they look off and wobbly when taxiing. They have to land, so they have ground equipment, but they are built for flying. A happy plane is an airborne plane.
Planes aren’t designed to be on the ground. That is why they look off and wobbly when taxiing. They have to land, so they have ground equipment, but they are built for flying. A happy plane is an airborne plane.
1). Airliner tires are made with several layers of soft rubber interlaced with Kevlar. They are very strong.
2). Airliner tires only need to work about 200 miles or so before they are replaced. Roughly every 200 landings. Truck tires go thousands of miles.
3). They are ablative. That means they are designed to wear in a predictable, controlled way. That’s why runways have all those black stripes down the middle from tires.
1). Airliner tires are made with several layers of soft rubber interlaced with Kevlar. They are very strong.
2). Airliner tires only need to work about 200 miles or so before they are replaced. Roughly every 200 landings. Truck tires go thousands of miles.
3). They are ablative. That means they are designed to wear in a predictable, controlled way. That’s why runways have all those black stripes down the middle from tires.
1). Airliner tires are made with several layers of soft rubber interlaced with Kevlar. They are very strong.
2). Airliner tires only need to work about 200 miles or so before they are replaced. Roughly every 200 landings. Truck tires go thousands of miles.
3). They are ablative. That means they are designed to wear in a predictable, controlled way. That’s why runways have all those black stripes down the middle from tires.
Is this a real post? #Brake
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