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Thread ID: 117893	2011-05-09 10:21:00	Helicopters	Poppa John (284)	PC World Chat

Post ID	Timestamp	Content	User
1200876	2011-05-09 10:21:00	Hi All. A bit puzzled is all. The big blades on the top are for lifting. the small blades at the tail are to stop the m.c spinning on its axis. On one of the bin Laden reports it said that a special stealth tail tail rotor was fitted to cut down the 'whump, whump' noise. I always thought that this noise came from the main rotor blade as they were moving so fast that the tips were breaking the sound barrier. Am I right or wrong. At Wanganui we have an Appache copter that does flight training etc. Damned noisy brute. Always makes me laugh. When it comes towards you it is very loud, as it passes overhead & moves off you can hardly hear it. So one of these is flying over a Vietnam forest, giving the enemy advance warning of its approach. Very humane. PJ.	Poppa John (284)
1200877	2011-05-09 10:32:00	The trick is to land the helicopter far enough away so that it cannot be heard then walk the rest of the way.	Bobh (5192)
1200878	2011-05-09 10:40:00	"On one of the bin Laden reports it said that a special stealth tail tail rotor was fitted to cut down the 'whump, whump' noise" The report as you surmise is wrong. en.wikipedia.org	Terry Porritt (14)
1200879	2011-05-09 10:46:00	"On one of the bin Laden reports it said that a special stealth tail tail rotor was fitted to cut down the 'whump, whump' noise" The report as you surmise is wrong. en.wikipedia.org I would not know but looking at your link Terry, it appears that a shroud may be fitted to direct noise sideways as evidenced by the pic on the right partway down the page. en.wikipedia.org	Snorkbox (15764)
1200880	2011-05-09 10:50:00	They used Chinooks they don't have a tail rotor as such. They have big rotors back and front and they do have a very distinct noise very different to normal helicopters. They sound like the rotors are fighting each other. So if they could cut this noise they would since only the West mainly America uses Chinooks	gary67 (56)
1200881	2011-05-09 10:50:00	I would not know but looking at your link Terry, it appears that a shroud may be fitted to direct noise sideways as evidenced by the pic on the right partway down the page. I should have expanded and said the comment about reducing the wump wump was wrong. The tail rotor sound frequency as indicated in the link, and by common sense and observation is very much higher. The higher frequency sound is also more directional.	Terry Porritt (14)
1200882	2011-05-09 11:04:00	Hi All. A bit puzzled is all. The big blades on the top are for lifting. the small blades at the tail are to stop the m.c spinning on its axis. On one of the bin Laden reports it said that a special stealth tail tail rotor was fitted to cut down the 'whump, whump' noise. I always thought that this noise came from the main rotor blade as they were moving so fast that the tips were breaking the sound barrier. Am I right or wrong. At Wanganui we have an Appache copter that does flight training etc. Damned noisy brute. Always makes me laugh. When it comes towards you it is very loud, as it passes overhead & moves off you can hardly hear it. So one of these is flying over a Vietnam forest, giving the enemy advance warning of its approach. Very humane. PJ. The report about the tail rotor making the thump thump thump noise is wrong. It is the main rotor that makes that noise. :)	Trev (427)
1200883	2011-05-09 11:11:00	I should have expanded and said the comment about reducing the wump wump was wrong. The tail rotor sound frequency as indicated in the link, and by common sense and observation is very much higher. The higher frequency sound is also more directional. No worries. I did think that those who wanted to take the tail assembly of the crashed 'copter away and the USA wanted it back seemed to indicate that there may have been modifications made to the said assembly. Or not as the case may be.	Snorkbox (15764)
1200884	2011-05-09 18:46:00	The Thump-Thump that comes with the Iroquois is due to its twin blade set-up,with the forward travel, its the leading blade that momentarily breaks the sound barrier with the thump being the mini sonic boom	Lawrence (2987)
1200885	2011-05-09 20:12:00	The Thump-Thump that comes with the Iroquois is due to its twin blade set-up,with the forward travel, its the leading blade that momentarily breaks the sound barrier with the thump being the mini sonic boom The Cong had plenty of notice the yanks were coming to kill them.	prefect (6291)
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