Crosswords4 mins ago
hi
how does a plane stay in the air with the weight of it
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a plane is held in the air by the lifting forces exerted on the wings caused by the air travelling over the wing surface which has a special profile. if you look at a cross section of a wing profile you will see that the bottom is nearly flat but the top has a humped shape...this causes the air to travel faster over the top of the wing than it does below the wing. this doesn't create lift below the wing as most people think but creates lift from above the wing due to the air pressure being lower above the wing....kind of like a vaccuum effect! as long as the wing surface is large enough to provide more lift than is needed for the total weight of the plane and the plane is moving forward fast enough to provide the required airflow,the whole lot stays up in the air!:)
Nothing will move anywhere unless there's a force making it move. The force which makes something 'drop to earth' is weight which, of course, is always present wherever there's gravity. However, the air moving across the wings of an aircraft creates an upward force, called 'lift'. When the two forces, lift and weight, are the same, the aircraft remains at a constant height. If weight is greater than lift, the aircraft will descend. If lift is greater than weight, the aircraft will climb:
http://www.raes.org.uk/raes/careers/education/ education_planes.htm
Chris
http://www.raes.org.uk/raes/careers/education/ education_planes.htm
Chris
(With apologies to Garlandk9 for clogging up the thread)
Mushroom25:
Imagine that there's a deep crevice, which goes down hundreds of metres but is only 1 metre wide. If I held you above the crevice and let go, you'd plunge to your death. However, you could easily jump over the crevice and, midway through your leap, you'd be in exactly the same place where I (with my murderous intent!) had planned to let go of you.
The difference is that, in mid-jump, you'd have sufficient momentum to return you to a safe position. Exactly the same is true of an aircraft 'looping the loop'. It's momentarily in an 'unsafe' position but there's sufficient momentum to return it to safety.
Chris
Mushroom25:
Imagine that there's a deep crevice, which goes down hundreds of metres but is only 1 metre wide. If I held you above the crevice and let go, you'd plunge to your death. However, you could easily jump over the crevice and, midway through your leap, you'd be in exactly the same place where I (with my murderous intent!) had planned to let go of you.
The difference is that, in mid-jump, you'd have sufficient momentum to return you to a safe position. Exactly the same is true of an aircraft 'looping the loop'. It's momentarily in an 'unsafe' position but there's sufficient momentum to return it to safety.
Chris
Chris is pretty close on this one. However, if you notice, at air shows for example, when a small aerobatic aircraft is flying upside down, the nose of the aircraft is fairly high on the horizon and the aircraft creates an arc from the start of the manuever to the end. That is, it's flight path is curved, especially descending towards the end. The reason is that the wing of the rather underpowered aircraft is more symmetrical than a standard small aircraft wing that gonzo00 described. It can fly almost equally as well upside down, but not quite as good as right side up (due to a lot of drag caused by being upside down). Therefore, as the continued upside down flight continues, the aircraft, to maintain the minimum airpseed required for inverted flight, trades off some altitude witnessed by the arc and descending flight. (Normal flight, by the way, is also dependent on Newtonian downward thrust of the air as it moves aft off the wing).
This doesn't apply to high-powered jet fighter aircraft. They have so much excess power that, in effect, their small very thin wings are more like stabliizers than actual lift providing surfaces (although they do that as well).
There are many older aircraft that are used in airshows that weren't really intended for inverted flight. Their fuel and oil systems weren't designed for it, but more importantly, the fairly thick wings can only provide a small amount of lift inverted if the nose of the aircraft is abnormally high in relation to the horizon. This has some analogy to the skipping of a rock in a pond. It keeps skipping until enough of its speed is bled off and then it sinks. The aircraft would too, in an inverted stall if allowed to proceed very far inverted....
Want to know how an airplane flies straight up?
This doesn't apply to high-powered jet fighter aircraft. They have so much excess power that, in effect, their small very thin wings are more like stabliizers than actual lift providing surfaces (although they do that as well).
There are many older aircraft that are used in airshows that weren't really intended for inverted flight. Their fuel and oil systems weren't designed for it, but more importantly, the fairly thick wings can only provide a small amount of lift inverted if the nose of the aircraft is abnormally high in relation to the horizon. This has some analogy to the skipping of a rock in a pond. It keeps skipping until enough of its speed is bled off and then it sinks. The aircraft would too, in an inverted stall if allowed to proceed very far inverted....
Want to know how an airplane flies straight up?
I should have guessed that Clanad would post a reply here ;-)
(He's an airline pilot).
Clanad:
Thanks for your answer. Physics was a subsidiary subject for my mathematics degree (and I've taught the subject to teenagers) but I must admit to having always had difficulty with understanding some of the 'finer points' of flight.
However, I remain confident that, in some cases, there's little more than momentum that keeps a plane in the air while looping the loop. During World War II, my late father worked as ground crew on a RAF base. On VE Day,one of their pilots decided to celebrate by looping the loop. His chosen aircraft was a Lancaster bomber! He successfully completed the manoeuvre, with the only damage being caused by the Elsan toilet which smashed through a bulkhead :-)
Chris
(He's an airline pilot).
Clanad:
Thanks for your answer. Physics was a subsidiary subject for my mathematics degree (and I've taught the subject to teenagers) but I must admit to having always had difficulty with understanding some of the 'finer points' of flight.
However, I remain confident that, in some cases, there's little more than momentum that keeps a plane in the air while looping the loop. During World War II, my late father worked as ground crew on a RAF base. On VE Day,one of their pilots decided to celebrate by looping the loop. His chosen aircraft was a Lancaster bomber! He successfully completed the manoeuvre, with the only damage being caused by the Elsan toilet which smashed through a bulkhead :-)
Chris
Great story Chris!... (Those darn toilets...)
A loop, however, is a lot different than inverted flight. Actually, a well performed loop shouldn't impose anymore than about 1 G force on an aircraft. However, the problem arises when the inexperienced pilot attempts one and about half way through when the aircraft is on its back at the top of the loop and control forces are reversed the pilot tends to revert to one of the Laws of Learning... i.e., The Law of Primacy... he's always been taught and experience confirms that pushing forward lowers the nose, but inverted one has to push forward on the elevator control to raise the nose. This usually results in the novice "falling out of the loop"... disastrous if there isn't sufficient altitude for recovery...
A loop, however, is a lot different than inverted flight. Actually, a well performed loop shouldn't impose anymore than about 1 G force on an aircraft. However, the problem arises when the inexperienced pilot attempts one and about half way through when the aircraft is on its back at the top of the loop and control forces are reversed the pilot tends to revert to one of the Laws of Learning... i.e., The Law of Primacy... he's always been taught and experience confirms that pushing forward lowers the nose, but inverted one has to push forward on the elevator control to raise the nose. This usually results in the novice "falling out of the loop"... disastrous if there isn't sufficient altitude for recovery...
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