Where do you people get the idea that it's outlined in the problem that the plane isn't moving/can't move WRT the ground? All it states is that the treadmill maintains the negative of the plane's velocity. As per that same statement, it doesn't even make sense that the treadmill would be moving at all if the plane wasn't.


Regardless, the plane is free to move WRT the ground. And it'll take off.



[Edited on November 21, 2007 at 10:46 PM. Reason : FUCK it only took a few hours to overcome my refusal to argue this further.]

11/21/2007 10:44:24 PM

Quote :

"He was talking about a 747 going transonic at landing....that shit is impossible."

Bullshit. I said no such thing.

I said there are two steps in designing anything from a safety standpoint.
Step 1 is to imagine the worst-case scenario. That scenario is a plane landing at full speed. In the case of a 747, that's around 500mph or something. Imagine if the flaps stopped working and the engines got stuck at full throttle and the pilots had to land on the Nevada salt flats. That's the worst case for landing.
Step 2 is to take that worst-case scenario and add an extra margin of safety. The extra 50% is something that the plane will never see in real life. The 747 will never hit the ground going 750mph because the damn plane can't go that fast. The engines don't produce enough thrust and the body creates too much drag. It's fucking impossible. You do know what a safety margin is, right? It's put in there for safety's sake - you sure as shit hope it never gets used. ... just checked your profile, and oh shit you're a senior in AE this year or next. Fuck, my degree has just dropped in value another notch. You remember what the structures guy on your team is doing? He's taking the customer requirement (6 g's) and ADDING 50% TO IT just in case you guys fuck up your construction. Fuck, the wings will stall before you hit 6 g's, nevermind 9. It's an impossible scenario, but you plan for it just to be safe.

11/21/2007 11:14:03 PM

max speed of a 747 is between 580-610 (depending on what model 747 is)

Those speeds are transonic, thanks for playing.

11/21/2007 11:25:58 PM

depends on the altitude

11/21/2007 11:33:37 PM

so does the plane take off or not

11/21/2007 11:33:49 PM

No

11/21/2007 11:34:30 PM

^^^^ What the hell is your point? My point is that the landing gear should be strong enough to handle well over 2x the takeoff speed. Yours seems to be that a 747 would have difficulty flying in the transonic regime with high air density. I can't figure out what your point has to do with anything.

^^ Yes.

11/21/2007 11:40:12 PM

My point is the Landing Gear would fail before takeoff is achieved.

The discussion if a 747 could handle a transonic landing is a tangent. However, since we're on the subject, lets talk about what its idiotic for a plane's gear to be designed to take a transonic landing.

1. The plane would be destroyed at that speed.

2. Should the Airplane be stuck at full throttle, you don't try to land the plane, you dump fuel, wait for the engines to die, and glide in.

3. Designing and installing a landing gear that can take that kind of landing is both costly and adds weight to the plane.

4. I know what a safety margin is and landing gear prolly have a good one, but the LANDING WILL FAIL AT THOSE SPEEDS.

[Edited on November 21, 2007 at 11:47 PM. Reason : a]

11/21/2007 11:46:39 PM

Quote :

"1. The plane would be destroyed at that speed."

You just said that the plane travels in the transonic regime 5 posts up. Are you specifically referring to the sea-level density being the reason the plane would be destroyed? That doesn't seem likely to me. It wouldn't be a happy plane, but I doubt the wings would get ripped off or anything.

Quote :

"2. Should the Airplane be stuck at full throttle, you don't try to land the plane, you dump fuel, wait for the engines to die, and glide in."

Every passenger on board who had fish for dinner will become fatally ill within the next hour. The cornfields, Ted, the cornfields!
It's called a worst-case scenario for a reason.

Quote :

" 3. Designing and installing a landing gear that can take that kind of landing is both costly and adds weight to the plane. 4. I know what a safety margin is and landing gear prolly have a good one, but the LANDING WILL FAIL AT THOSE SPEEDS."

Wing structures are designed to fail at 150% of stall loading. That adds a shitload more weight than a couple of extra bolts in the landing gear and costs a hell of a lot more, and it's just as impossible for the wings to experience those kinds of loads.

Quote :

"My point is the Landing Gear would fail before takeoff is achieved. "

Takeoff speed is what, 150mph? You think the treadmill doubling the speed to 300mph would cause the gear to fail? Judging from what I personally think is an acceptable safety margin design limit for landing gear, we're easily in the safe regime. Very easily in the safe regime.

Please define what you think would be an acceptable limit for landing gear limits. I don't know what Boeing decides for their planes, but I'd like to see your opinion on the matter anyway.

11/22/2007 12:05:27 AM

Quote :

"It's called a worst-case scenario for a reason."

Not all worst-case scenarios are prepared for either in equipment or pilot training.

11/22/2007 12:07:22 AM

Quote :

"Moron My reading of the original myth is that the plane stays static in real space and begins to fly, not that it wont roll down a treadmill. ie they are arguing that if a plan has to be moving 30 fps to takeoff, and you roll the treadmill 30fps the opposite way, and hold the plane still using only thrust from its engines, it will begin to fly. "

Yeah, it's obvious it wouldn't be able to fly in that situation. I don't think anyone is arguing that it would. The engines would have to be barely spooled up though, practically idling, to keep it still from an outside reference frame.

[Edited on November 22, 2007 at 12:15 AM. Reason : ]

11/22/2007 12:14:36 AM

Quote :

"My point is the Landing Gear would fail before takeoff is achieved. The discussion if a 747 could handle a transonic landing is a tangent. However, since we're on the subject, lets talk about what its idiotic for a plane's gear to be designed to take a transonic landing. 1. The plane would be destroyed at that speed. 2. Should the Airplane be stuck at full throttle, you don't try to land the plane, you dump fuel, wait for the engines to die, and glide in. 3. Designing and installing a landing gear that can take that kind of landing is both costly and adds weight to the plane. 4. I know what a safety margin is and landing gear prolly have a good one, but the LANDING WILL FAIL AT THOSE SPEEDS."

I'm not sure what flight sim you've been playing, but we all think your cock is huge. You can now stop arguing the complexities of aircraft engineering as if you knew what you were talking about because your aerospace professor dropped a few hypotheticals to demonstrate a base concept.

11/22/2007 3:47:50 AM

WHY IS THIS THREAD 8 FUCKING PAGES??????????????????????

11/22/2007 8:18:53 AM

Quote :

"What happens when you "land" an airliner at over 1000 feet per minute rate of descent? This MD-80 crew found out. This was a certification test flight in 1980 and was supposed to be a hard landing at about half that descent rate."

http://www.laurencescholte.com/flying/MD-80hardlanding.mpg

That landing gear looks pretty sturdy to me.

11/22/2007 9:54:46 AM

aww, I was proud of that video. I want to argue some more. Don't let my research slide off into oblivion.

11/23/2007 5:35:01 PM

ttt for that video

11/23/2007 10:22:35 PM

Now, it's a different kind of stress than would be administered in a double-speed takeoff, but I think if they're engineered to take a hit that hard, they're probably engineered to take a high speed roll.


ps - some awesome videos on that site: http://www.laurencescholte.com/flying/videos.html

[Edited on November 23, 2007 at 11:07 PM. Reason : ps]

11/23/2007 11:06:51 PM

bttt, tonight

12/12/2007 9:25:15 AM

oh snap, i need to record

12/12/2007 9:28:25 AM

I figured more people would be wanting to watch this tonight.

12/12/2007 11:11:06 AM

what time?

12/12/2007 11:12:32 AM

o snap

12/12/2007 11:14:15 AM

Quote :

"Quote : " http://community.discovery.com/eve/forums/a/tpc/f/9801967776/m/5321919039/p/1 Airplane Hour (Weds., December 12 at 9 PM ET/PT) Adam and Jamie find out if either of them can safely land a Boeing 747-400 on a runway in varying weather conditions. Meanwhile, Kari, Tory and Grant risk life and limb to investigate skydiving myths regularly featured in Hollywood action films. Is it possible to catch up with someone in freefall if that person jumps out a plane before you do? Can you really hold a conversation during freefall? And would you survive if you opened your parachute only a few feet off the ground? Finally, Adam and Jamie carefully navigate their way through a myth that has baffled everyone from web bloggers to pilots. If a plane is traveling at takeoff speed on a conveyor belt, and the belt is matching that speed in the opposite direction, can the plane take off? Extensive small-scale testing with a super treadmill and a nearly uncontrollable model airplane don't completely resolve the myth, so our flight cadets supersize the myth with help from a willing pilot and his Ultralight flying machine. ""

12/12/2007 11:14:36 AM

i'm definitely going to be watching

but, like most people said up here, the experiment is not really going to give the correct answer. something is going to be not exactly as the question says it should be, which will leave the discussion forever open.

12/12/2007 11:14:44 AM

i was explaining this to some people at work, and yea at first they were like no it wont then i explained a little and they said "what was the Q again" and they agreed with me.

its funny how people try to switch their answer around because they didnt hear it correctly.

12/12/2007 11:22:11 AM

this whole thread is people arguing over different things. you have one side saying that if the treadmill can hold the plane in place, it won't take off. then the other side is saying that the treadmill won't be able to hold the plane in place to begin with.

12/12/2007 11:24:41 AM

then you have people saying "well the bearings in a plane wheel cannot handle 20943w84 mph.

12/12/2007 11:33:00 AM

on in 3 hours

12/12/2007 5:46:53 PM

Its not going to take off. You people who think it will are fucking morons. As the plane moves forward along a runway, they are moving at say 180mph and are on the ground. If the runway were a huge treadmill that increased in speed the same amount that the plane moved forward, but in the opposite direction, the plane is going to be sitting still compared to everything around it. There is going to be no air flow over the wings. Its really not that hard to fucking understand people.

12/12/2007 5:50:35 PM

well no matter what happens tonight people will still argue about it

12/12/2007 6:02:50 PM

Quote :

"Its not going to take off. You people who think it will are fucking morons. As the plane moves forward along a runway, they are moving at say 180mph and are on the ground. If the runway were a huge treadmill that increased in speed the same amount that the plane moved forward, but in the opposite direction, the plane is going to be sitting still compared to everything around it. There is going to be no air flow over the wings. Its really not that hard to fucking understand people. "

Haha, you didn't read this thread.

You're going to feel like an idiot when the plane takes off.

12/12/2007 6:10:49 PM

this could easily be solved using basic dynamics

anyone up for it? instead of arguing like a bunch of dumbasses

12/12/2007 6:36:08 PM

someone needs to make a giant treadmill.

then we will find the real answer.

12/12/2007 6:39:20 PM

just dont let baonest on the plane.

12/12/2007 6:40:31 PM

haha.

12/12/2007 6:43:27 PM

^^^^^Oh I read the thread, every single post. And I am not going to feel like an idiot at all when it fails to take off.


Wheels are rotating at said speed in one direction, ground is moving at said speed in opposite direction. Its not going anywhere.

[Edited on December 12, 2007 at 6:44 PM. Reason : .]

12/12/2007 6:43:39 PM

dexter, with a name like that you better be smart.

12/12/2007 6:44:43 PM

seriously, you idiots really want to know the answer, do some math

12/12/2007 6:45:24 PM

The wheels aren't powering the treadmill. The treadmill is powered on its own. It doesnt matter where the wheels are getting their power from.

12/12/2007 6:46:30 PM

dude i added the terminal velocity and took the total away from the ground resuscitation theorem of Bucks law and came up with 3

12/12/2007 6:46:57 PM

terminal velocity of an airplane is zero. cause airplanes are parked when they're at terminals.

12/12/2007 6:58:58 PM

oh snap.

well i may have to change my answer then, or just wait for mythbusters

12/12/2007 7:05:36 PM

I predict they are going to say it won't take off. But some of you are gonna come on here and say how they fucked it up, and you know more than they do, and they were wrong. Can we just all agree to settle on what they decide without questioning what they find?

12/12/2007 7:06:51 PM

haha NO

you want the actual answer

DO SOME FUCKING MATH

[Edited on December 12, 2007 at 7:10 PM. Reason : ,]

12/12/2007 7:10:10 PM

i can't tell if Dexter is trolling, or a moron

12/12/2007 7:12:45 PM

I am being 100% dead serious.

12/12/2007 7:36:14 PM

12/12/2007 7:41:04 PM

bttt 10 minutes


Regardless of what happens on Mythbusters, I guarantee people are gonna be pissed.

12/12/2007 8:53:02 PM

uuuhhhhh


so that said nothing about it

12/12/2007 9:02:01 PM

you noticed that too

watch em spend like 2 minutes on it and screw it up

[Edited on December 12, 2007 at 9:04 PM. Reason : ]

12/12/2007 9:03:57 PM