Low-flying helicopters. Black and unmarked

a reply to: buddah6

These were both low flying helicopters. Probably 200ft.

I am finding nothing relevant on Nadic, but that scheme will not work based on physics as I explained. I also doubt this technology was used on the bin Laden chopper.

originally posted by: Sammamishman
a reply to: gariac

oc·cult

/əˈkəlt/

verb

past tense: occulted; past participle: occulted

cut off from view by interposing something.
"a wooden screen designed to occult the competitors"

•Astronomy
(of a celestial body) conceal (an apparently smaller body) from view by passing or being in front of it.

Oh yeah, I had looked it up before doing my post.

a reply to: gariac

I didn't say this technology was used on the Bin Ladin raid. My point was it was too heavy for its use on helicopters and that's why older technology was used on the "stealth Blackhawks." They used modified rotor blade tips, slower turning tail rotors, retractable landing gear and a blended body fuselage. This scheme was good enough to fly 160 miles into Pakistan, with a load of SEALs, in a moderately protected airspace and to egress without losses due to enemy action.

I am not a physicist just an old military guy though I have taken physics in college. I can't tell you why these technologies work or why they don't...this was above my paygrade. I like to read studies that are interesting from DARPA, MIT, Carnagie-Mellon and Nadic labs to watch the technologies that I do understand. I'm the nuts and bolts guy that gets things to work when BAD systems were given to me to use. This does require a fundamental understanding of most of the physics involved.

What do you know about the helicopters used on the Bin Ladin raid? I would like to know and have you explain it to me. Where are you getting your info from Nadic and what do you think they do there? So educate me!

a reply to: buddah6

What do you know about the helicopters used on the Bin Ladin raid? I would like to know and have you explain it to me. Where are you getting your info from Nadic and what do you think they do there? So educate me!

All I know about the stealth chopper was that article from Aviation Leak. However, I know the reasons why all these so called visible stealth schemes don't work. If they actually worked, you would be seeing this technology everywhere. There are all sorts of papers on technology that really don't work in real life. It is all a matter of how you write it up. Eric Davis of "Warp Drive Metrics" is the classic example of a publisher of dubious science.

You can debunk most visual stealth quite easily, at least the type that emits light. First of all, if you are emitting light, that can be detected since light is energy. But the idea is your light is supposed to match the background light. But as I explained, the object that you light will be like a point source. It will follow the physics of the point source. You can't fight the laws of physics.
Inverse square law
The background light is very diffuse and planar. It doesn't have much of a falloff since since it already far away. So to match the background light, you need to know the distance to the observer and use the square law accordingly. That means you can only be visually stealthy over a very small zone.

This doesn't mean you can't set up artificial testing conditions and achieve a visual stealth. You have your test subjects in one location, you pick the light just right, and they have a hard time seeing it. The trouble is someone in a different location will have an easier time seeing your aircraft because it is emitting light that doesn't match the background for their location based on distance.

Forums like ATS will spew thousands of posts on visual stealth, much like they do on large underground complexes. My rant on underground complexes is they are generally not really underground but in mountain sides since that soil is more stable. But that is another topic.

The shroud on the tail rotor could possibly be to diffuse some of the heat from the rotor bearing and transmission. If you watch a blacked out helicopter with night vision, the heat from the tail rotor puts out enough infrared light that you can see it glow.

The tail rotor is the Achilles heel of helicopter technology. Lots of research goes into getting rid of it. I suspect using one is the cheapest solution since the alternative designs are less popular. The tail rotor is great for making noise to warn the enemy of your approach. It has a different pitch than the main rotor. The tail rotor is higher pitched and easier to locate by ear. [Higher frequency sound is more directional.] The main rotor is louder, but lower in frequency making it harder to tell where the chopper is located. Besides, you really need the main rotor. You can design out the tail rotor. I've had the Coast Guard Eurocopter notars approach me a few times and you just can't locate them ear easily until they are on top of you.

The deal with the stealth chopper not being seen by Pakistan had to do with the direction of their early warning radar. Pakistan uses their resources to snoop on India. I'd have to reread all the bin Ladden raid data again, but if I recall correctly, they also use a Chinook in the raid. There is nothing more familiar to the ear that the Chinook dual rotor sound. That thing is loud loud loud. I'm sure it isn't very stealthy either.

Incidentally, in this India-Pakistan conflict, Pakistan is usually the aggressor. It really POd me that the US was giving Pakistan so much aid when the country is mostly a source of destabilization in the region. The US intelligence sources deliberately didn't warn Pakistan about the raid because all indications were that Pakistan was aiding bin Ladden. The design of the compound, according to leaked intelligence, was such that bin Ladden didn't have a "plan B" to escape. Thus the US intelligence believed that bin Ladden believed he would get some advance notice of a raid. That isn't much of a stretch since bin Ladden got advance notice of the missile attack on his compound that Clinton launched. The US had to alert Pakistan of the missile launch because it would look like India was attacking, which could start a counterstrike.

a reply to: gariac

Thank you for your input! I'll need to digest this post a bit to grasp it's finer details.

i think the dyson ring bladeless fan tail rotors will get rid of that issue no? i see a v22 style dual dyson bladeless aircraft right around the corner too, something like the old CnC orca maybe?

originally posted by: gariac
a reply to: buddah6

What do you know about the helicopters used on the Bin Ladin raid? I would like to know and have you explain it to me. Where are you getting your info from Nadic and what do you think they do there? So educate me!

l zondetected since light is energy. But the idea is your light is supposed to match the background light. But as I explained, the object that you light will be like a point source. It will follow the physics of the point source. You can't fight the laws of physics.
Inverse square law
The background light is very diffuse and planar. It doesn't have much of a falloff since since it already far away. So to match the background light, you need to know the distance to the observer and use the square law accordingly. That means you can only be visually stealthy over a very smale.

This doesn't mean you can't set up artificial testing conditions and achieve a visual stealth. You have your test subjects in one location, you pick the light just right, and they have a hard time seeing it. The trouble is someone in a different location will have an easier time seeing your aircraft because it is emitting light that doesn't match the background for their location based on distance.

Forums like ATS will spew thousands of posts on visual stealth, much like they do on large underground complexes. My rant on underground complexes is they are generally not really underground but in mountain sides since that soil is more stable. But that is All I know about the stealth chopper was that article from Aviation Leak. However, I know the reasons why all these
so called visible stealth schemes don't work. If they actually worked, you would be seeing this technology everywhere. There are all sorts of papers on technology that really don't work in real life. It is all a matter of how you write it up. Eric Davis of "Warp Drive Metrics" is the classic example of a publisher of dubious science.
You can debunk most visual stealth quite easily, at least the type that emits light. First of all, if you are emitting light, that can be another topic.

The shroud on the tail rotor could possibly be to diffuse some of the heat from the rotor bearing and transmission. If you watch a blacked out helicopter with night vision, the heat from the tail rotor puts out enough infrared light that you can see it glow.

The tail rotor is the Achilles heel of helicopter technology. Lots of research goes into getting rid of it. I suspect using one is the cheapest solution since the alternative designs are less popular. The tail rotor is great for making noise to warn the enemy of your approach. It has a different pitch than the main rotor. The tail rotor is higher pitched and easier to locate by ear. [Higher frequency sound is more directional.] The main rotor is louder, but lower in frequency making it harder to tell where the chopper is located. Besides, you really need the main rotor. You can design out the tail rotor. I've had the Coast Guard Eurocopter notars approach me a few times and you just can't locate them ear easily until they are on top of you.

The deal with the stealth chopper not being seen by Pakistan had to do with the direction of their early warning radar. Pakistan uses their resources to snoop on India. I'd have to reread all the bin Ladden raid data again, but if I recall correctly, they also use a Chinook in the raid. There is nothing more familiar to the ear that the Chinook dual rotor sound. That thing is loud loud loud. I'm sure it isn't very stealthy either.

Incidentally, in this India-Pakistan conflict, Pakistan is usually the aggressor. It really POd me that the US was giving Pakistan so much aid when the country is mostly a source of destabilization in the region. The US intelligence sources deliberately didn't warn Pakistan about the raid because all indications were that Pakistan was aiding bin Ladden. The design of the compound, according to leaked intelligence, was such that bin Ladden didn't have a "plan B" to escape. Thus the US intelligence believed that bin Ladden believed he would get some advance notice of a raid. That isn't much of a stretch since bin Ladden got advance notice of the missile attack on his compound that Clinton launched. The US had to alert Pakistan of the missile launch because it would look like India was attacking, which could start a counterstrike.

a reply to: gariac

The stealth helicopter doesn't use "visible stealth" unless you are referring to the ability to detect "see" aircraft by radar. This is measured in radar cross section (RCS) which is the reflectivity of the radar signal returned to the radar receiver. Helos are and have always have had high RCS by virtue of it angular components like rotor masts, shafts for main and tail rotors, landing gear and air intakes. The "stealth helicopter" Is not invisible to radar it just reduces what the radar sees (RCS) as much as "practical." Practical means that the modifications to decrease the RCS doesn't reduce the ability to carry out it's assigned mission. The RCS is "measured" on a test range using various frequency radars to determine the helicopters "actual" radar cross section. With the RCS known the helicopter can approach the radar transmitter closer before detection. By knowing there the radar stations are and it's RCS the helo can navigate in and around the country without radar detection. The helo can also use terrain features to mask it's "noise signature" to aid it approach to it's objective. This technique works for non stealth aircraft as well (read Chinook). Radar is "line of sight" meaning is can't "see" through forests or around terrain features like hills or mountains or over the horizon is understood even by non stealth pilots.

It would seem that you think that aircraft/stealth aircraft go blundering into a hostile airspace with the thought that only stealth will protect them. This couldn't be farther from the truth! All incursions into a hostile airspace are planned in great detail. All military commanders know what his aircraft are capable of doing and is the final approval of any mission. He would not permit a mission launch without a high probability of success.

You are correct in that the helicopter industry doesn't like the tail rotors since 20% of helicopter accidents are caused by tail rotor failure or contact with something. The tail rotor causes a good amount of the total noise signature of the helo but unfortunately they are still more effective than NOTAR or the fenestron. To date only smaller helos use these devices.

I can tell that you haven't been around many helicopters. Your statement about the Chinook being loud, loud, loud is incorrect. You hear the transmission noise much more than the rotor or engine noise.

You statements about undergound bases have me totally confused and needs further explanation.

I'm familiar with the inverse square law from high school physics but maybe you are seeing something that I'm not saying. Further explanation required!

a reply to: buddah6

They also use EW to help mask their signature. There are some EW systems that instead of just blotting out the entire spectrum, it will prevent a signature from being seen is the best way I can put it. Highly effective systems, and work wonders with a reduced RCS.

originally posted by: buddah6
a reply to: Zaphod58

The exhaust kits that I referred to was just a tube bent 90 degrees that attached to the engine exhaust pipe and it wasn't a blower. This did two things, first redirected hot engine gas up into the rotor wash which cooled it to a point where an IR missile had difficulty locking on to the helicopter. Second, the shape of this tube blocked direct viewing by an IR source below and behind the helicopter from the ground perspective. This was use on the Huey and Cobra helicopters. This concept was designed into the modern helos...Blackhawks and Apaches.

gariac, Helicopters flying blacked out doesn't mean you can't see them with NVG. It just means you see them for a shorter period of time. The helicopter crew can change the time you see and hear them by adjusting their altitude and flying "Nape of the Earth" which is 5 to 50 feet height. One other thing that you need to consider is the vast majority of modern armies still don't have NVG let lone NVG for every soldier like the US.

The Nadic Labratories has new technologies that makes aircraft 95% invisible by photographically imaging the sky above the aircraft and displaying it on the bottom. Unfortunately, this technology is too heavy for use on helicopters. This is why you see helicopters like the one that crashed on the Bin Laden raid.

I believe this is what you guys are referring to... The UES (upturned exhaust systems) for the blackhawk program.

originally posted by: buddah6
a reply to: gariac

The stealth helicopter doesn't use "visible stealth" unless you are referring to the ability to detect "see" aircraft by radar. This is measured in radar cross section (RCS) which is the reflectivity of the radar signal returned to the radar receiver. Helos are and have always have had high RCS by virtue of it angular components like rotor masts, shafts for main and tail rotors, landing gear and air intakes. The "stealth helicopter" Is not invisible to radar it just reduces what the radar sees (RCS) as much as "practical." Practical means that the modifications to decrease the RCS doesn't reduce the ability to carry out it's assigned mission. The RCS is "measured" on a test range using various frequency radars to determine the helicopters "actual" radar cross section. With the RCS known the helicopter can approach the radar transmitter closer before detection. By knowing there the radar stations are and it's RCS the helo can navigate in and around the country without radar detection. The helo can also use terrain features to mask it's "noise signature" to aid it approach to it's objective. This technique works for non stealth aircraft as well (read Chinook). Radar is "line of sight" meaning is can't "see" through forests or around terrain features like hills or mountains or over the horizon is understood even by non stealth pilots.

It would seem that you think that aircraft/stealth aircraft go blundering into a hostile airspace with the thought that only stealth will protect them. This couldn't be farther from the truth! All incursions into a hostile airspace are planned in great detail. All military commanders know what his aircraft are capable of doing and is the final approval of any mission. He would not permit a mission launch without a high probability of success.

You are correct in that the helicopter industry doesn't like the tail rotors since 20% of helicopter accidents are caused by tail rotor failure or contact with something. The tail rotor causes a good amount of the total noise signature of the helo but unfortunately they are still more effective than NOTAR or the fenestron. To date only smaller helos use these devices.

I can tell that you haven't been around many helicopters. Your statement about the Chinook being loud, loud, loud is incorrect. You hear the transmission noise much more than the rotor or engine noise.

You statements about undergound bases have me totally confused and needs further explanation.

I'm familiar with the inverse square law from high school physics but maybe you are seeing something that I'm not saying. Further explanation required!

I didn't bring up visual stealth. The other poster did.

I know about RCS.

I have been on the ground when Chinooks flying low. I know exactly what I am talking about. They are very loud.
My photograph of a CH-47 on the Nellis range

Chinooks terrorize town

Quoting Army Col. H. Charles “Chuck” Hodges Jr.:

The helicopters — Hodges said they were four CH-47 Chinooks, twin-engine, tandem rotor heavy-lift helicopters, “big, heavy machines, they make a lot of noise especially when they operate near water” — were over Port Angeles from about 11:15 p.m. to shortly before midnight Thursday.

The application of the inverse square law is obvious, and I explained it well. I'm not really sure I can dumb this down any more than I have. Let us look at a similar situation, namely the photo flash. If you examine a photograph done with a flash, it is obvious that objects closer to the flash get more light than distant objects. The flash is a point source, and the illumination suffers from the inverse square law. You will see professional photographers try to make the lighting look more like a plane (not aircraft, but as in planar). If you had an infinite plane light source, there would be no fall off. Obviously you can't do that, but you can use large light panels to get close.
light panel
Now the sky is approximately an infinite plane light source. When you light an object to attempt to match the intensity of the sky, you are doing so with a point source. Thus you can only match the intensity for an observer at a specific distance. You have to adjust your light output using apriori knowledge of the distance to the observer. In the mean time, you have made the plane brighter than the sky for other observers not in the target zone.

I brought up underground bases because it attracts the same amount of useless drivel as active visual stealth. [Note I am not saying there are not passive ways to make aircraft less visible.] The underground base fanatics envision digging holes in the ground big enough to fight air wars, i.e. the never ending Dulce BS. In reality, not all soil is suitable for doing anything underground, or not with a lot of concrete and rebar. Typically what is done underground are small chambers or tunnels, which is a structure that is easy to reinforce. [Cylinders distribute their stress along their surface.] Most actual underground structures are really in hill sides and preferably mountains. Mountain soil is strong else it wouldn't be a mountain in the first place. If the mountain soil was poor, the soil would have eroded into the valley.

originally posted by: Zaphod58
a reply to: buddah6

They also use EW to help mask their signature. There are some EW systems that instead of just blotting out the entire spectrum, it will prevent a signature from being seen is the best way I can put it. Highly effective systems, and work wonders with a reduced RCS.

Can you quote a specific designation of equipment?

Georgia Tech has a series of engineering books on RCS, and they go into how to make radar lose lock. The books are censored a bit for security reasons. They are also targeted for electrical engineers, not the general public, though I don't consider the text to be very complicated. Nothing like Maxwell's equations in point form.

I think jamming is more effective than stealth, especially if the jamming occurs a bit out of the battlefield, such as with the Growler/Prowler.

But I wouldn't call jamming masking.

a reply to: gariac

At least one of them that I've heard of isn't in general use. EW is more than jamming though. It has been used in the past to paint false targets, as well as other things to confuse radar. Jamming is jamming, but true EW uses all kinds of different features to fool radar.

a reply to: gariac
Please tell me that you don't read those books! Those books are like watching paint dry and guaranteed to put you sleep with in 30 seconds. lol!

When EW is used in a modern airspace it is like ringing the doorbell telling everyone that we're coming. Most of the time it is used on a strategic level and rarely on a tactical one. A good example is the first Iraq war when the USAF jammed all Iraqi military communication frequencies the night before hostilities started. The Iraqis were shooting at everything including seagulls after dark. For the guys up at 30k felt secure but for us who flew at and below 15k it was one hell of a ride. Army guys usually fly below 1500 ft EW is of little use due to terrain. The only advantage is the ability to break radar missile lock...nuf sed

I have seen a ton of activity in western North Carolina in the past month and atleast 1 to 2 times per week.... 2 weeks ago I had 8 kiowas and 4 apaches fly over my house then about an 30 min to an hr they came back over with 2 chinooks... I was in the military and got out 5 yrs ago and I can guarantee you I did not see one marking to help identify them... They too were flying around 500 - 1000 ft max and the kiowas had been upgraded

a reply to: buddah6

You guys keep thinking jamming. There are EW systems that can spoof radar and not let anyone realize they're in the system.

originally posted by: Zaphod58
a reply to: buddah6

You guys keep thinking jamming. There are EW systems that can spoof radar and not let anyone realize they're in the system.

And specifically the designation is??????

a reply to: buddah6

I am a ham and have a MSEE. Those books are great reading material, especially radar lock schemes.

Maybe Pakistan has poor early warning, but I think any 1st world country will see you coming. Jamming sounds like a good plan to me. Radar return path loss is enormous. It doesn't take much RF to put up fake targets.

a reply to: weavty1
This is exactly what that I was referring to but on the Blackhawk. On the Huey it is just an up-turned extension of the engine exhaust.

a reply to: buddah6
Zoph,

Sorry, I just get emotional when I think about that night...lotsa big stuff shot at me.!!

You are 100% correct about the EW. It is a great asset when used with low RCS aircraft.