How does a jumbo jet take off?

Answer 1

The way a jet plane flies is quite different from a propeller engine plane. While a propeller type plane flies by forcing enough pressure below and lifted up from pressure on top of the wing, the jet flies as it reaches enough speed and top wing pressure and as the tail is tilted down at an angle the jets force is straight out the angle is changed thus forcing the plane to move up.

Answer 2

I'm going to make this simple as the physics involved can be quite taxing to get to grips with. However if youre asking this I'll have to use a few technical terms, bare with me. I'll also assume you mean a standard design like the Huey, or Squirrel, and not something unusual like a Chinook.

OK our helicopter has a set of spinning main rotor blades, and there is the tail rotor.

On the ground with nothing running the tail rotor and main rotors are linked together through a system of gear boxes and drive shafts. If you turn the tail rotors, the main rotors will turn, although this rate of turning is geared so a complete rotation of the main rotor blades will need several turns of the tail rotor. This will become apparent why a bit later.

Now beneath the main rotors is the Main rotor gearbox (MRGB). This usually accepts the power input from the engines, and sends drive down to the tail rotors. The rotor blades are to an extent flexible, and at rest will be drooping down. The actual shape of the blades when you take a cross section is that of an aerofoil, just like a planes wing. Just as a Planes wing generates lift so does a helicopters rotor blades.

Now as we start up the helicopter to go flying, the rotors that were drooping will spin out with centrifugal force, buch as you would expect, until the blades sit in a flat plane of rotation. As the blades are spun faster, they will start to develop lift, and will start to rise into a flattened cone. Once this point has been acheived as the blades spin faster and develop even more lift. Now the blades are all able to pivot about their root to alter the angle they turn round at. A steeper angle will give more lift, and a shallower angle will offer less lift. Infact Helicopters designed to be used from the back of ships usually have an inverse angle that acutally forces the helicopter onto the deck of the ship. So as the angle is increased to get more lift, when the lift force is more than the downward force of the weight of the aircaft, the helicopter will take off.

Now if you've watched the film "Black Hawk Down" you'll know that a helicopter with no tail rotor will just spin wildly out of controll, and trash a large area of the ground below. So whats going on there, obviously the tail rotor is the key to safe flight, but how is this done? Think of the black hawk with no tail rotor spinning, This is a phenomenon known as "Torque reaction", and is the same as a powerfull car being rocked side to side as the engine is gunned at the lights, or a motorbike doing a wheelie. So to counter this, the tail rotors are like a big fan that blows against this torque reaction. Changing the angle on these tail rotors will allow you to change the amount of air blown, and cosequently allows the helicopter to spin on the spot.

So a bit more angle on the main rotor blades and the helicopter will go higher.