Why the wheels of the big jets are not powered to drive them at the airport ?

Answer 1

Can you imagine how much torque you need to put in the tiny wheels of the plane (compared to its size) to be able to move the plane on the ground?

You would require a huge engine to do so. A huge engine would add weight to the already heavy body.

So the smarter way is to use the plane's own jet power to propel it forward. The only problem is reversing, and for that they have tug cars.

Cheers!

Answer 2

Actually, such a system does exist, and is in the process of being implemented right now.
The Chorus Motors corporation is in the process of working with Boeing to power the wheels of Boeing jets with electric motors when on the ground. These electric motors are to be powered by the APU (Auxiliary Power Unit) that supplies power for the rest of the plane while on the ground, and will be used to eliminate the use of both push back tugs, and the aircraft's jet engines when on the ground.
Just over a month ago, Delta Airlines signed an agreement with the "WheelTug" group to outfit a number of their 767s with these devices. The aim is to save the amount of expensive fuel burned on the ground, as well as eliminate the labor, equipment, and fuel needed to own and run pushback tugs at the airports.

Prior to now, airlines have dismissed such a system as being un-economical. They decided that the added weight and cost of a motor would be greater than the savings in fuel. With the ever-rising cost of jet fuel, Delta has apparently found that the fuel saved on the ground will be worth more than the cost to install the motors. The technology has been there all along, airlines simply didn't want it untill now.

Answer 3

Because the wheels don't need to be given any motive force at all.

Aircraft, even big jets, can only safely carry so much weight aloft. The difference between the gross take off weight of the aircraft and the empty weight of the aircraft is called the usefull load; that consists of pax, (passengers,) crew and cargo.

Since the airplane already has a motive force, (its engine,) capable of pushing it through the air with enough power to create lift, it can usually move around surprisingly well on the ground without any help. Adding additional means of powering the landing gear wheels not only increases the empty weight, thereby reducing the usefull load, is essentially guilding the lily.

Large aircraft can back up, back away from gates, using the same thrust reversers they use when landing if they absolutely have to. They typically don't because the pilots don't have a means to visually see what they're about to back into and because reversing that sort of thrust is typically not good for the structure they're leaving.

Thrust reversers, (TR's) also increase the possibility of foreign object damage to the engines by pushing ground debris off the ground and into the air that the engine is about to consume. As a handfull of gravel can demolish a million dollar engine, the practice is considered unwise.

Answer 4

Could be useful in saving fuel for ground maneuvering but the added weight makes it unattractive.

Answer 5

Good question. How come the propellers on big boats are not powered to drive them on the road?

Answer 6

They are, but it costs ALOT of fuel, so its cheaper to pull them.
But some jets land so fast so the mechanism would break down if they were connected to a motor and could crash the landing, which is a unessesary risk to take.

Answer 7

You're sitting there with something like 100,000 horsepower under your hand, so why add more? It works pretty well just like it is.

Answer 8

There's no need for it. It would be needless additional weight and just one more thing to maintain.

Answer 9

just a guess: extra unnecessary weight?