Plz only technical answer?

who says they cannot ?

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http://au.com/80422151922AAWQVza

Who says they can not??

What do you think they do to get the plane from boarding site to runway?

Sometime they can while on the ground - turboprop often have a ''beta'' pitch setting for the prop that can be used for braking or even backing up. Jet is have reverse thrust, but it is generally to noise and produces too much jet blast to use fo backing up.
In the air, a plane uses it is forward motion through the air to produce the lift it needs to stay in the air. If you are not moving forward at considerable speed, you're falling, not flying.

2 words, reverse thrusters. In large airports planes are normally reversed by tugs or tractors and this process is called push-back.

Go to flightlevel350.com and enter 4567 in the ''Search Videos'' box. There, you will see a DC-9 backing up under its own power by deploying her ''clamshell'' thrust reversers.

It would be cost effcienct Whe you puse them less fuelAKA SHUTTLE FLIGHTS ARE PULLED TO THE PLATEFORM SO LESS FUEL

Airplanes CAN be moved backwards. You either push them by hand (small general aviation aircraft) or, if they are too big to hand push, hook ''tugs'' up to them to move them backwards.

Some a jet aircraft have reverse engine thrusters, but the pilot cannot adequately see to the rear of the aircraft because of the configuration of the fuselage.that is why engines are not used to move aircraft backwards.

They are, we use to back-up in the Herc all the time by putting the props in reverse pitch. We'd always have a ground guide as well as having the ramp open & the Loadmaster on the intercomn. The Flight Engineer would be in the bubble.

Many aircraft have reverse thrusters & pitch. Most of the time they r used on the runway during landing to decrease the landing roll.

For backing one must be careful, one fo the hazards is blowing over people or equipment in front of you. I've seen a few vehicles blown over in my time, forklifts being the vehicle of choice. I've also seen several cabs blown off of trucks.

The Harrier & Osprey can fly in reverse direction, I`ve seen it done. Someone here stated no aircraft fly in reverse.

All airplanes can be moved backward.

Airplanes cannot fly backward, if that is what u r asking, because the wings & controls work only in forward motion.

If u mean can they be moved backward on the ground, the answer is that it is done all the time. You just have not been paying attention. Light planes can be pushed backward by hand or by tractor (''tug''). Larger airplanes r moved backward with tugs or by reverse thrust. The latter is tricky because the pilot cannot see where she is going.

Most airline companies have policies prohibiting reverse taxiing.

If u want technical , ask a technical question.

when the planes back up, and all of the sudden, stops, the plane should tip backwards, because of the weight in the back is more than in the front!

Aircraft engines r designed to work in the following manner. They pull a lot of air in the front end, then they push it out from the back end. They push it out the back faster than they pull it in the front. Therefore, since momentum is defined as mass x velocity, momentum is added to the flow through the engine by the energy in the fuel & the work done by the turbines. The laws of physics demand that momentum of a system must be conserved. Therefore, momentum is added in the opposite sense to the airframe. This results in thrust, which moves the aircraft forward. It is like standing on a cart & throwing bowling balls off the back. The more u throw & the faster u throw them, the more the cart will move forward. Thrust reversers can be used to maintain the airflow into the front, but stop or divert the flow out the back. This has the opposite effect, i.e. it provides momentum in the aft direction, providing braking for landing.

Not in the air. That doesnt make sense. On the ground planes with reverse thrust can move backwards. This is not always the best things since it drives up debris & dust forward of the engine where the intakes r & increases the chance of ur engines ingesting it. You usuallyonly deploy reverse thrust when moving forward on the ground.
The military will often use reverse thrust in flight when an emergency descent is needed. l sat in a C-17 training session in a sim & the procedure was to depoly reverse thrust in flight with alot of pitch down to get the plane down without overspeeding.

assume you mean propel themselves backwards on the ground.

they can, but typically do not power back from an airport terminal to avoid possibility of damage to buildings/people/ground equipment.