BS: The Mythbusters airplane takeoff problem

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: gnu
Date: 05 Nov 12 - 06:00 PM

"When Brittania ruled the waves, you could have sent an invasion force to make us all do it your way...but those days are long over, my good fellow. Learn to live with it. ;-)"

Long over? You read a newspaper lately? Iraq? Afghanistan? Libya? Egypt? Syria?....

And, don't chore me with "details" about why you think I am wrong. Britannia makes the waves. Sail with her or drown.

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Bobert
Date: 05 Nov 12 - 08:08 PM

Okay, LH... No air speed, no lift... You don't get air speed sittin' on a friggin' treadmill unless the plane has a stall speed of zero... Lowest stall speed I know of is in the 20 mph range...

BTW, speakin' of airplanes... "My Poor Brother"... Remember him??? Well, first of all he ain't never been "poor"... But he has gotten himself into a pickle or two but this ain't one of those...

Reckon about 25 years ago he got this idea that he was gonna be a stunt pilot and was learnin' aerobatics and we were just out bombin' (not literally) over the area where his farm was in a Cessna 172 and reckon he just wanted to scare me so he stalled it at 5000 feet... Big deal... The plane shudders and then a warning sound starts tellin' ya' that yer air speed is too slow to fly the airplane... Like I said, "Big Deal"...

Now every pilot in the world knows that you put the nose down and all is well, right...

So "My Poor Brother" decided, "What the Hell... Think I might as well scare the hell outta the Bobert" so he puts a danged rental Cessna into a purdy serious dive and this plane ain't really up for that kinda stuff but I guess his aerobatics instruction musta told him what kinda ridiculous air speed a 172 could handle... So I'm lookin' at the air speed indicator and watchin' as he hit 100, 110, 120, 130, 140 and we've dropped 3000 feet in what seemed like seconds...

Now, I didn't let on but at a buck forty I was beginning to think, "Hmmmmmm, Poor Brother gonna fuckin' kill us" but I didn't let on... No, I was scared shitless at that point then I look over and this Cessna is diving fast 150 miles per hour... That is fast in a Cessna 172!!! Very fast... These shit boxes ain't F-16s... At about 800 feet he pulls up on the yoke and this Cessna is vibratin' & shudderin' and levels out at no more than 300 feet...

"Uh huh" I was thinkin', "I'll get even one day for that little scare"....

'Bout 5 years later we were flying down to Kitty Hawk, NC (yup, that one) in a rented Cessna 210 Turbo and low clouds kept up bumping along at 115 mph at 1500-1700 feet 'cause "My Poor Brother" ain't instrument rated and that meant no cloud punchin'...

So we're somewhere over the "Northern Neck" in Va and had an hour or so before we had to swing west to avoid restricted air space around Norfolk/Newport News so brother says,' "I'm kinda sleepy and gives me a heading, says "Your plane" and pulls down his ball cap to take a nap...

Well, folks... There are those times in life where the rule that "Get-backs are Hell" and this was going to be one of those days...

I wanted to be sure that "Poor Old Brother" was in downtown sleepsburg as I plotted my egt back and I kept lookin' over for signs and then saw his head kinda fall to one side without any jerkin' so I knew that the bases were loaded...

I wasn't sure I had the balls to do it but...

...WTF???

So I pulled up on the yoke ever so slightly... Felt it fightin' as I put that 210 into a full stall and the plane was vibratin' and shudderin' and then the warning alarms went off...

That was all it took to get poor brother outta his nap...

"What's happening, Bobert?"... "What the hell you done???"... "My plane, brother"... "Shit..."

So I let him put the nose down and take us out of stall... He was pissed... Who cares???

We laugh about it these days....

Get backs are Hell...

B;~)

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Little Hawk
Date: 06 Nov 12 - 01:18 AM

That's right, Bobert. No air speed, no lift. However, the wheels on the plane spin freely, unlike the wheels on most vehicles. The static inertia of the airplane means that when the treadmill starts moving East, the plane doesn't move east with the treadmill. It sits where it is, due to its own inertia, and its wheels spin. Now you start up the propellor. The plane will want to move west due to thrust pulling the plane through the air. The wheels will spin even faster while in contact with the moving treadmill. Presently the plane will start moving west because the prop is pulling it in that direction. If its wheels were resisting the treadmill, as the wheels on a car would, then the treadmill would cancel out the plane's westward movement, but the wheels aren't resisting the treadmill's eastward motion. They're spinning freely. The plane will move west regardless of the treadmill, and the wheels will spin ever faster as long as they are in contact with the treadmill. Presently the plane will reach a westward rate of speed sufficient to take off, regardless of what the treadmill is doing.

***

fossil - you're right about the RAF not providing parachutes to their unfortunate airmen during almost all of WWI. The Germans provided parachutes to theirs by about halfway through, and many German airmen's lives were saved by bailing out of stricken aircraft.

Hamsters, however, have to make and provide their own parachutes whenever they use them, even German hamsters! Therefore the RAF policy in this regard was irrelevant in the case of wheel hub riding hamsters. A sensible wheel hub rider didn't need a parachute, because he would leap off just as the plane was leaving the ground...but a tiny parachute would be a good emergency backup in case the hamster for some reason did not jump off soon enough, as could happen with rotational intoxication!

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Bobert
Date: 06 Nov 12 - 10:43 AM

If the treadmill accelerates equal to that thrust of the props then those wheels can spin as fast as they want... That was the original information, no??? If that is the case then no air speed is created and therefore no lift... The plane has to actually move by one of two ways:

Sufficient air speed over and under the wings or because the prop is out dueling the treadmill or...

...there is one heck of a lot of headwind that day that allows sufficient air moving above and below the wings...

That's the way I see it but, hey, seein' as I wrecked a Piper J-3 Cub on my 16th birthday, I ain't gonna say that I'm in Charles Lindbergh's league... lol...

B~

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Little Hawk
Date: 06 Nov 12 - 12:39 PM

Bobert, take a diecast toy car whose wheels spin freely (like those on an airplane). Put it on top of a treadmill. Move the treadmill rapidly east. Does the toy car move along smoothly in the same direction with the treadmill? No, it doesn't. Its own weight (inertia) causes it to want to remain where it is, and its free-spinning wheels allow it to do just that, despite the moving treadmill. If placed exactly in line with the treadmill (so its wheels are perfectly aligned) it will tend to remain in its original position geographically, regardless of the treadmill.

The same is true of the airplane.

But....If you now add propellor thrust pulling it west, the vehicle will move in the direction the propellor is pulling it...to the west...you will get the necessary airflow over the wings...and you will generate lift sufficient to allow takeoff.

Any hamster with a degree in mechanical engineering could figure this one out! ;-)

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Bobert
Date: 06 Nov 12 - 12:41 PM

Oh, I get it... Duhhhh...

Yes, of course the plane would take off... Might burn up the bearings in the wheels but the treadmill would not counter the props...

B~

Subject: RE: BS: The Mythbusters airplane takeoff problem
From: Little Hawk
Date: 06 Nov 12 - 12:53 PM

Yup. Those wheels would spin like hell. It would make an extra-thrilling ride for a thrill-seeking, wheel-hub-riding hamster.