If it’s because of wind tunnels that helps push the planes faster, how much slower would they be if they weren’t in those wind tunnels?
If the average flight from NY to London is 7H and 10M what would the flight time be?
In: Physics
Aircraft can go faster with less fuel in the thinner air of high altitude. At the same time, if they go too high, the air is so thin that maintaining altitude is difficult. 30000 to 40000 feet is the sweet spot where you can maintain altitude and fly most efficiently.
That the jet stream is operative at those altitudes, in some areas, is an additional bonus that can save you 10% to 20% of the total flight time, but only in certain directions. For example, NYC to London is about 7 hours, but London to NYC is about 8 hours.
No, it’s not the wind tunnels (or jet stream). Because those things, if you happened to catch one, will only help you in one direction. Like maybe flying from NY to London it pushes you along faster, but flying back from London to NY and it slows you down.
It’s because the air is less dense up high, meaning there is less wind resistance, less drag, meaning you can fly your plane faster and be using less fuel than if you were flying lower in the thicker air.
Imagine it like this: flying up high is like running on land just moving through the air. Pretty easy. Flying low is like running through a pool, that thicker, denser, water makes it much harder for you to move.
The main reason to fly high is to reduce air resistance. Air gets less dense at higher altitudes. This means the airplanes can fly faster and use less fuel. The same throttle settings give the same fuel consumption and might get the airplane up to 250 knots at sealevel but over 500 knots at cruise altitude. This means you get there in half the time and therefore burn fuel for half as long spending only half as much fuel.
Airplanes would have flown higher if it was not for the speed of sound. When you fly close to the speed of sound there are a lot of negative effects including higher air resistance. And flying higher and faster means you get closer to the speed of sound.
I think you mean jet streams. Wind tunnels are giant ducts with fans, used to test aircraft.
And no, while the jet streams sometimes help, they’re not the reason for flying so high. The reason is that air resistance is a massive drag (literally), so if you can get above most of the air, it saves a lot of fuel – more than what’s needed to get up there. Jet engines can handle this, because they have compressors that can easily squeeze that sparse air into something that supports combustion.
There are 3 big advantages to flying high. The air is less dense the higher you go so with the same amount of power an airplane will go faster. The other reason is that jet engines are more efficient at higher altitudes then lower altitudes so it takes less fuel to fly the same distance at 40,000 feet as it would at 15,000 feet. The third advantage is that “weather” meaning rain, snow, clouds and bumpy air currents happen at lower altitudes and flying at 40,000 feet you are flying above most to all of it. This makes the flight more pleasant and safer.
The jet stream may work for (tailwind) or against a plane (headwind). As you say that means a plane can fly 120 knots faster in a tailwind and 120 knots slower in a headwind. Similar to going along with the current in a river or against the current in a river.
The gains or losses depend on the current strength of the jet stream, the direction of travel, and the distance of travel.
Flying high (cruising altitude above 30,000 ft) means thinner air and more efficient flying at cruising altitude where jets are designed to be most efficient.
Additional advantages to flying at high altitudes: it’s above the clouds usually, less weather-related turbulence, and it takes a long time to glide down, giving pilots more options in emergency situations.
Air is squishy. At sea level, we have the weight of the whole atmosphere sitting on top of us, so it squishes the air to a higher density. Higher up in the atmosphere there is less air above, so the weight squishing the air down at that altitude is less. To push an airplane through the air you have to push the air aside and around it. Up high where the air is less squished, there is less air in the space a plane needs to move through, so it takes less effort to push it out of the way.
Because the air is thinner there, so going fast takes less energy.
Imagine if you had to compete in a swimming race, one pool is regular pool water, the other is full of jelly. Which would you be quickest in? The water, for sure.
Planes flying at higher altitude are much more efficient than low altitude. They use less fuel for the same speed and distance travelled.
Since we all like paying as little as possible to travel, it’s in our interest.s
The main thing really is that the troposphere is turbulent. It’s somewhat hazardous, but mainly just uncomfortable. A 10h of vomit comet is not fun. But if you rise above clouds to stratosphere, there is much less vertical airflow, almost no turbulence at all.
While engines are less efficient at high altitudes. Lower air density reduces drag at higher altitudes which is more than enough to overcome the inefficiencies.
Which is why each model has their own optimal cruising altitude for lowest fuel usage.
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