Aces High Bulletin Board
General Forums => The O' Club => Topic started by: Motherland on March 07, 2010, 12:10:55 AM
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(http://i156.photobucket.com/albums/t5/AK_Comrade/willittakeoff.jpg)
HELICOPTER ON A TURNTABLE!!
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:rofl :rofl :rofl :rofl :rofl :rofl
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:rofl
BTW, it won't fly.
:bolt:
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:rofl
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No helicopters fly they merely beat the air into submission.
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Sure...
Of course the air beats back once the blades approach the sound barrier.
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If I understand correctly, a heli can only go as fast as it's retreating blade. IIRC, the fastest heli can push about 285 mph or so. IF that's the case, I wouldn't think the sound barrier would be an issue. Any input?
AAJagerX
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Know how a helicopter flys? They are sooooo ugly the Earth repels them....LOL
KAM
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If I understand correctly, a heli can only go as fast as it's retreating blade. IIRC, the fastest heli can push about 285 mph or so. IF that's the case, I wouldn't think the sound barrier would be an issue. Any input?
AAJagerX
I believe he was talking about the blade speed,not the air speed,once a prop aproaches the speed of sound,things happen that arent condusive to flight............. :lol
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I don't think a heli blade can get close to the speed of sound. The AF tried to go supersonic with a turbo prop plane, and the blades breaking the sound barrier created so much noise that ground crews would get nauseous. I'd have a hard time believing that a blade the length of a heli blade could spin that fast without snapping.
AAJagerX
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exactly,thats why the "not condusive to flight "statement was made............ :devil
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I don't think a heli blade can get close to the speed of sound. The AF tried to go supersonic with a turbo prop plane, and the blades breaking the sound barrier created so much noise that ground crews would get nauseous. I'd have a hard time believing that a blade the length of a heli blade could spin that fast without snapping.
AAJagerX
The advancing blade (on the right side) will approach the sound barrier when at cruising speed. That's why you hear the Wop-Wop-Wop-Wop when a helicopter flies overhead at cruising speed.
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Denholm is right. That's why Hueys have that unmistakable sound thanks to their long blades.
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Denholm is right. That's why Hueys have that unmistakable sound thanks to their long blades.
I absolutely love the sound of a huey in flight :aok
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You are correct sir, I just looked that up.
Quote:
Say you have a single-rotor helicopter with standard clockwise turn; The left-side (the honing side) will always be faster than the fuselage of the helecopter while the right-side (the lagging side) will always be slower!
As level speed increases, this honing and lagging also increase so the left side blades are going fastestl, the right-side blades slowest of all and the helicopter itself is somewhere in the middle!
The left-side blades will reach supersonic blade tip speed when the helicopter reaches approximately 350mph! But with the speed of the main rotor blades the left-side will reach supersonic speeds actually before that horizontal straight-line speed is reached. Should this happen the helecopter would most likely be totally unflyable; At transonic speeds the honing blades would be violently flexing as the shockwave attached itself to the top of the blades. As soon at the blades came around to the lagging side they would go subsonic but due to their lagging behind and the forward speed, they would make no practical lift at all.
My only issue is that no heli can get to 350 MPH, therefore, the blades would never break the sound barrier.
If I'm off here, let me know.
AAJagerX
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exactly,thats why the "not condusive to flight "statement was made............ :devil
Trim it out!
AAJagerX
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If I'm off here, let me know.
AAJagerX
You are off.
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Most of you are neglecting the RPM and blade length component in your though process....
A blade could go supersonic at 100 mph of forward flight or 400 mph, or any number for that matter depending on the two.
Strip
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You are off.
I can accept that. I just want to know the how's and why's of it. If you've got info, please share.
AAJagerX
EDIT: Nevermind, I found an explanation that shed some light on the subject for me.
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helicopters cant go over 200kts becase at that speed, the back rotors will loose lift. The only way to get past that is to us a counter-rotating coaxial pusher design like that of the sikorsky X2. Because the 2 rotors are rotating in oposite directions, the lift will never be lost. the X2 is suppose to be able to fly over 250kts, though its flight testing has just started and has only reached 106kts so far.
as for the sound barrier, helicopter rotors can easily go over mach 1.
a CH-47 chinook has rotor diameter of 60ft so its circumfrence is 188.4ft. if at 1000rpm, the blades' tips are turning at 188,400ft/min=11,304,000ft/hr
11,304,000/5280=2140mph. as you can see, its clearly above the speed of sound.
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I don't think a heli blade can get close to the speed of sound. The AF tried to go supersonic with a turbo prop plane, and the blades breaking the sound barrier created so much noise that ground crews would get nauseous. I'd have a hard time believing that a blade the length of a heli blade could spin that fast without snapping.
AAJagerX
The blades on the Tu-95 'Bear' go supersonic. That is why it is so noisy. I have heard it is the noisiest aircraft in the world.
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helicopters cant go over 200kts becase
Helicopter speed record:
August 11, 1986 John Egginton 249.1mph (216 knots) Westland Lynx 800 G-LYNX Fastest helicopter
Sorry you were saying?
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depends on the record your playing while the heli is on the turntable, maybe a little ACDC to kick it up a bit!
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You don't actually fly a helicopter. You take off and make a series of corrections..
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You don't actually fly a helicopter. You take off and make a series of corrections..
hopefully an endless series!
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The blades on the Tu-95 'Bear' go supersonic. That is why it is so noisy. I have heard it is the noisiest aircraft in the world.
Off-topic: Sub crews have said that the bears prop noise was so loud that they could be heard while submerged.
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Helicopter speed record:
August 11, 1986 John Egginton 249.1mph (216 knots) Westland Lynx 800 G-LYNX Fastest helicopter
Sorry you were saying?
in general helicopters cant go over 200kts. out of hundreds of helicopters that have been designed and made you have found one... and that was a one time deal. its designed max speed is only 201 mph. also, G-LYNX was also specially modified for that flight. so once again, no production helicopter is designed to fly over 200Kts
thats like saying the Convair 880 is a supersonic airliner because it broke mach 1 in a controled dive.
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in general helicopters cant go over 200kts. out of hundreds of helicopters that have been designed and made you have found one...
you said:
helicopters cant go over 200kts becase at that speed
I found one. Therefore your statement was invalid, whether it was 1 or 100.
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you said:
I found one. Therefore your statement was invalid, whether it was 1 or 100.
but its not a normal helicopter. it was a specially modified one. it also only happened once. so my statement is still valid. your just being obtuse and taking what i said out of context by using one example that has only happened once and under special circumstances. if that helicopter is able to fly at those speeds, then why doesnt it typically do it? also why is its max structural speed only 201mph?
thats like saying cars can go 350mph and then use a "car" that has a jet engine on it to proove the point.
so since you want to be so complicated, ill expand more on what i said for the second time... so... 99.998% give or take .1% of all helicopters cant hit 200kts or no production models can.
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but its not a normal helicopter. it was a specially modified one.
So is it a helicopter or not?
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I absolutely love the sound of a huey in flight :aok
Particularly when it's coming and not going!
:rock
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I never liked riding in helicopters because there's a fair probability that the bottom part will get going around as fast as the top part.
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Only if the tail rotor fails. But if it's any comfort. The G's encountered if the tail rotor fails and the helicopter actually begins spinning will cause loss of consciousness before impact. :D
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Dropkick… Ch-47D Chinooks travel 196 mphand the UH-60 Blackhawk can travel at 221 MPH They are the two fastest in the American Inventory.
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a CH-47 chinook has rotor diameter of 60ft so its circumfrence is 188.4ft. if at 1000rpm, the blades' tips are turning at 188,400ft/min=11,304,000ft/hr
11,304,000/5280=2140mph. as you can see, its clearly above the speed of sound.
Whoa, just a second here. 1000 RPM? A helicopter that size won't have a rotor head speed anywhere near that, more like 160rpm.
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Ok gents here is the specs for the CH 47 right from the Boeing web site:
http://www.boeing.com/rotorcraft/military/ch47d/ch47dspec.htm
Hopefully this answers any quetions
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Doing the math for Ch47 rotors given the rotor speed of 225 rpm from the previously posted website, you get a tip speed of ~482mph. Even with 200mph forward speed added, the advancing blades will still be traveling below the speed of sound at the tip.
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Which goes back to me mentioning complications once the blades break the sound barrier. From what I've heard, uncontrollable vibrations are encountered when helicopter blades constantly break and re-enter the sound barrier. These vibrations eventually crack and break the blades.