Silent Helicopters

Originally posted by Mauser

Originally posted by ShatteredSkies
This might help im not shure, i might be wrong, but uhh the RAH 66 stealth copter hides its heat signature and the sound of its top rotor is a smooth almost silent whipering sound.

Indeed, a Stinger missile is no longer lethal to this new helicopter. That is because the tail rotor takes care of the heat by just blowing it away.

Following pic shows it:


Many of todays helicopters have their exhaust directly behind the main rotor, therefore they still are still vulnerable to heat seeking missiles.

hey i was watching the same program where you got the pic from! it is y i knew it off hand.

The zipped file is nothing but pink static when i played it

Originally posted by ShadowMan
The zipped file is nothing but pink static when i played it

Ow, i think it is because of your (.avi) codec. Click on the link below to download one of the best .avi codecs available:

www.afterdawn.com...

it should work now.

Most of the sound from helicopters comes from the tail rotor creating turbulence against the main one. Sound can be cut down 80% just by covering the inward edge of the rear rotor.

Just a fun fact

ive seen em once too they were taking off a heli pad near miami and then right after they took off they were SILENT....i was like wtf???? o.0

Here's a new unmaned helecopter they are testing.
The four-blade Hummingbird A160 vertical takeoff and landing unmanned aerial vehicle
It has the ability to fly using 50 percent of the power and 50 percent of the fuel consumed by similarly loaded conventional helicopters. As a result of the reduced power, the A160 is also substantially quieter, a benefit while operating in urban environments.
Maybe this is what you saw?
www.freepressinternational.com...

saw 3 interesting "objects" pass over last night going parallel SW to NE (towards the SAS base) completly silent, flashed every 3-6 seconds very brightly. very odd indeed..........

Speculation is futie.

I live on the coast of Florida, and approximately 3-4 weeks ago during the Hurricane Jeanne we were without power again, my girlfriend and I. We went outside and the normally well lit neighborhood was dark, which made for good skygazing, The clouds from the storm were passing and it was a nice night. That is when I saw a helicopter .

There was a ship with lights which I assumed was a helicopter by how it was moving, almost hovering, moving slowly from West to East and very low. As it started to pass over I realized I could not hear it. It was low, less than 500 or so feet. Now, in front and in back of this craft were two others, and I could see no rotor on either of these craft, yet they were gliding over with no sound. No lights on the two other craft, but you could plainly see in the moonlight they were there. Then as fast as they appeared they were gone. It was real eeire.

I wouldn't classify the A-160 Hummingbird as a silent copter. Its sound like a humming sound (hence the name) instead of the usual choppy sound, that way its noise blends in more with the surroundings.

I have never heard of a silent chopper, how do they get them silent? I think you people were looking at an Airship.

My colleauge Mr. Dreamstone is correct when he says that most of the helicopters' aural signature comes from the tail rotor, but even the NOTAR (no tail rotor, which patented concept is owned by Boeing and licensed to MD Helicopters) and the fenestron designs (enclosed tail rotors) are not completely quiet.

There are several ways to ameliorate tail rotor signature; the AH-64 A and D Apaches have their tail rotors offset (so that they look like an 'X' rather than a 90-degree cross).

Remember that there are three signatures important to helicopters; of these, the most important is IR signature, since most threats today come from shoulder-fired IR-seeking missiles. Most helicopters today have adoptedc the "black hole" technology, pioneered by the AH-64A back in the seventies, where by the heat signature from the engines is diffuesed through an external "heat-muffler".

Radar signature or RCS is of secondary importance; even the now-defunct AH-66 Comanche had a poor (i.e., overly large) RCS, especially when its stores carriage doors were open. since most radar "stealth" involves bouncing radar away from returning to the emitter rather than absorbing the signal, the physical construction of the aircraft is a tremendously important consideration. Unfortunately, with the rotors constantly moving, the helicopter simply cannot keep from bouncing back a signal to the emitter, and its RCS, therefore, is inherently large.

Aural signature for a military helicopter is probably the least important "stealth" aspect, since most of the new "fire and forget" air-to-ground missiles have an effective range far beyond the distance that the sound of the helicopter would carry. For civilian helicopters, aural signature is more important, since these thyically overfly cities and other built-up areas, and are subject to FAA and other regulations regarding noise pollution.

about 2 months ago i looked up of the deck of our house and i heard a
helicopter flying overhead but i could not see it
it was above my house pretty low but i couldnot see it
it didnt have any lights on it as well
it was really weird


[edit on 8-10-2004 by super64]

Go to google and type "rotor system having alternating length rotor blades....the fininshing paragraph sentence is "and positioning means therefor for reducing blade-vortex interaction (BVI) noise rotorcraft. That will take you to freepantents online....you might have to register to see the whole adobe PDF files and drawings. I printed off a long list of helicopter patent titles from braindex.com then went to free patents online, sign in then minimized free patents, went back to google and type the name from the braindex list. The reason for this is because there are so many patents that the free patents may not go straight to the one you want, but google does, but you have to be signed in to free patents to see all the patents. Just sign in and minimize then do everything from google.

Another is "active blowing system for rotorcraft vortex interaction noise reduction"
I'm not much into UFO stuff, although I have seen some weird stuff. Not sure about government cover ups..don't really care as long as they stay out of my yard and it's for the better of our country. Alot of people hate our government and i dislike some of the things they do too, but it's the most efficient government in the world. There's another web site you can get all the helicopter patents on CD-rom for $19 bones: www.braindex.com/products/280+-HELICOPTERS-&-HELICOPTER-PROPELLER-PATENTS

Just go to braindex.com and you'll find it. Hope I helped

I am a retired physician and quite an excellent rational observer. What I will relate is a real-world experience/observation witnessed by myself and two of my children while we were hiking in the Great Smokey Mountain National Park, Tennessee. The occurred fifteen years ago and I have kept it to myself for the sake of my country's security. We were hiking within Cade's Cove, an enormous remote valley surrounded by the park's mountain range. The valley is approximately 10 miles long and 4 miles wide. One of my sons grabbed my left arm as we were hiking east (parallel to the long axis of the valley) and asked me "Dad? What is that plane doing over there?" Up to that point the valley (early in the morning) was absolutely silent. We all turned to look left and observed a large, C-17-like, completely black aircraft with four external jet engines flying very slowly east without producing any audible sound. The aircraft was no more than one mile from where I stood. It flew slowly and smoothly, well inside the visual security of the valley. When it reached the western mountain rim of the valley it climbed over the rim and disappeared behind the mountains. It was clearly a military plane of substantial size and I was very proud of my country's ability to produce such an aircraft. I was MAGNIFICENT. So I can assure you we have or have had at least one large transport/cargo aircraft capable of flying with minimal or no sound.
Sincerely,

reply to post by chardrf


True. And don't forget Lotus and their sound cancelling technology of the 90's. The technology analyzed the engine exhaust noise and transmited 180 degree "noise' to effectivley "cancel" the annoying exhaust note. To what extent this can be applied to helos, I don't know. Check out the MD-500P. My father was envolved with SOG, LLRP's, Ravens, etc. as a FAC in the war. Also involved with "Igloo White", and other sensor deploying programs. He is aware of the "P" (for penetrator) being used in a mission deep in the North, to plant listening devices.