How is it, that a boeing 747 can go full throttle and still be stationary.I've seen this several times on TV.

Question

Just one of those things I just need answered.

Answer 1

They propably only throttled up one engine. Even more propably the inboard, as so to reduce the moment. The Parking Brake can easily handle just one engine.

Answer 2

Brakes!

Answer 3

The brakes can hold the airplane still even with all four engines at full throttle.  This is part of a takeoff procedure that is sometimes used.  You may see any airplane holding at full throttle, including turboprop and piston airplanes.  It is a routine procedure, and the brakes can easily handle it.

Answer 4

its the same as power braking a rear wheel drive car.. you simply apply the brakes and give it full power.. The 747 is an old plane and has somewhat small engines compared to the new 777 engines.. if you ever watched a 747 take off, you would see that it gets off to a rather slow start.. brakes would easily stop it from moving, even at full power.. on the other hand, if the plane was traveling down the runway and almost at rotation speed, it would be hard to stop it cuz it would have so much momentum built up.. just like a car trying to slow down for a stop sign

Answer 5

First in respond to that nozzle story above, if pressure is decreased, velocity of the airstream is increased.

2nd there are 16 brakes engaged (in case of a 747) each fastened with 3000 PSI. Where a car has 1 braking disc and a claw, creating the friction, an aircraft has a package of stator and rotor braking discs. With 3000 PSI of hydraulic pressure engaged, those rotor discs are immobilized between the stator discs, preventing the aircraft to start rolling off. Since the aircraft doesn't move, the anti-skid system does not disengage any of the pressure.

It's just like trying to push away a car with the parking krake engaged, you yust lack the power to overcome the friction generated by it.

One piece of advice, don't try this on a frozen runway, otherwise you start gliding over the runway (not kidding this happened one time) and you will get 16 flat tires because they aren't designed for that.

Answer 6

Brakes

Answer 7

On the Mythbusters show, where they flipped the school bus, the aircraft was tied down to a run-up pad, and only two engines were actually running at full power, creating thrust.

Answer 8

On the rear of each engine, built into the exhaust cone is an adjustable nozzle (ConvergingDiverging). As well as the brakes holding the aircraft still, the nozzles can be adjusted right open. By increasing the size of the nozzle, the hot exhaust gasses which create the thrust are exiting the engine at a lower pressure, which creates less thrust. By closing the nozzles the area of the exhaust is a lot smaller, creating a lot more exit pressure and much more thrust.

It can sit at full throttle with the brakes on and the nozzles open quite easily. If the nozzles were closed at full throttle, the airframe would be under quite a lot of stress and the brakes would start to fail.

Answer 9

Just sitting on the runway,brakes on,full throttle power ready for take off roll.

Answer 10

Parking brake, but if the 747's engines are on 100% throttle for more then 15 seconds, the ground will start to disentergrate, it was on top gear

Answer 11

Brakes and weight on wheels. the brakes will hold it stationary provided enough weight on the aircraft, usually in the form of fuel. If the fuel level is low or not enough ballast the B747 with all 4 engines at full throttle will move even with brakes applied.

Answer 12

where did you see that on TV?