Posted on 01/26/2016 10:33:19 AM PST by MtnClimber
Say what you want about them, but the team from Mythbusters which air on the Discovery Channel do have some great and entertaining experiments. From blowing stuff up to trying to walk on water, they skillfully test everyday myths people believe and make or break them. During this show, they did something our circle would really appreciate.
One of these engines produces 54,000 lbs. of thrust and a Boeing 747 has four of them.
Jet plasts are extremely strong, no matter what plane we're talking about. However, for effect these guys managed to get their hands on a Boeing 747, the second largest passenger plane in the world. Propelled by four 7R4D2 engines which cause quite a commotion on the back end of them they effectively demonstrate exactly what force these engines produce.
First, they positioned the plane at an end of an empty runway and drew a line on the grass which marked 100 ft. They started slow by first driving a taxi in the back of the plane while the engines were going full throttle. It got blown away like a matchstick. Then it was time to test out the bus. We won't give out the results here though. Enjoy the video.
(Excerpt) Read more at worldwarwings.com ...
Wow, don’t walk behind a 747!!! That bus went flying!
Jet blast is SRS BZNS!
cool
Geez Louise haha
Blown away!
With all that enormous thrust, how did the plane’s brakes hold?
A d-link snagged on something, saving him from death or serious harm, along with an alert fellow crewman that signaled the pilot to cut the engines before anything holding the suckee from the turbine blades could fail.
So much for Bullitt laying under a 707 at SF airport...
In this case, it appears that only one of the 747’s jet engines was running (you can see the grass laying flat behind only that single engine). Aircraft brakes can hold against some enormous levels of thrust, though.
It’s pretty simple, really. The plane is very heavy, and friction between the wheels and runway depends on the weight of the plane/vehicle. Lots of weight = lots of friction on a rough surface such as a runway. (Ice is a whole different discussion!)
There are lots of wheels, so the brake on each wheel only has to hold a fraction of the thrust. My car couldn’t hold that much back, but those airplane brakes are much bigger and designed to do just that.
You might also look at the same thing comparing the amount of power to each pound (or ton) of airplane. Big planes need big engines, and the plane is not easy to move, even with a lot of thrust. (Notice it takes a lot of time to get them rolling fast.) If it’s not easy to move, it’s not that hard to keep it from moving.
Top Gear did something like that many years ago. IIRC a Citroen 2CV was obliterated.
Awesome and nice break from all the political
On U-Tapao, there was ALMOST always one maintenance van (bread truck), in it’s rush to get off the tarmac, that would run the gamut behind all the KC135’s. And yes, there were a moment or two, when the dice came up wrong. The driver was never terribly injured (phew!), but the van was blown over.
That was a pretty old episode.....
In more recent events they have collapsed a railroad tanker car with a vacuum truck.
Not to mention the Iranian vehicles chasing the 747 down the runway in “Argo”.
Probably lots of movies with airport chase scenes with this error.
Thanks to both of you for your cogent replies. Plenty to mull over. The fact that only a single jet engine was in use blows me away, along side with that taxi and school bus.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.