The Kopp-Etchells Effect (Helicopter Light Scintillation Halo)

Brandon

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[Admin: Thread split from: https://www.metabunk.org/posts/46747

Or is it just friction? Friction creating heat, just like an engine. I don't know, but I know airplane wings don't get hot. I'm just guessing here. It's not static. Static looks like the pic.

Static from a rotor wing is really colorful and pretty and I can't believe there aren't better pictures than this popping up on google images. I had a job in the army that had me standing under helicopters that were hovering so low I could touch them (they were that low so I could touch them), but I never took pictures.

How's my science sound, Mick?
 

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That's static electricity in the picture. It has nothing whatsoever to do with sand. If you think rotor blades hit sand and that makes sparks or flashes of light or whatever, you're wrong. I would love to see actual scientific evidence that what you're claiming is even possible.
 
Well, your image is a helicopter in a sandstorm, basically sparks from friction of the sand hitting the blades. Not static.

http://sciencebasedlife.wordpress.com/2012/11/01/the-kopp-etchells-effect/

That's static electricity in the picture. It has nothing whatsoever to do with sand. If you think rotor blades hit sand and that makes sparks or flashes of light or whatever, you're wrong. I would love to see actual scientific evidence that what you're claiming is even possible.

It actually seems like the cause of the light is unknown, the photographer himself says a pilot said it's "static", the article I linked says pyrophoric sparks, possibly it's triboluminescence (which is itself not really understood. Whatever it is, it's cool!
 
It actually seems like the cause of the light is unknown, the photographer himself says it's "static", the article I linked says pyrophoric sparks, possibly it's triboluminescence (which is itself not really understood. Whatever it is, it's cool!

Anyone who's done any grinding knows what happens when you hit metal with fast moving sand - you get very hot sparks!!

Try the explanation here



In the middle of a desert, a military helicopter creates a stunning show while initiating an impossible static electrical discharge, spectacular phenomenon for all the lucky viewers of PDF.
...
[h=3]This is what exactly happens[/h]Helicopter RRPM is pretty much constant through out whether it be airborne or on the deck*
When the aircraft is coming in to land/slowing down and is near to the ground, it tends to have a larger vertical downward component of air (induced flow) coming through the top of the disc being pushed out through the bottom (easily seen when landing in dust or sand). As the aircraft gets near to the ground, air is sucked up all around the aircraft (recirculation). In sandy or dusty areas, this too is sucked up around and then dragged back down through the disc. Most modern helicopter rotor blades are of a composite construction but usually tend to have a stainless steel or similar leading edge abrasion strip to help prevent wear to that part of the blade. The tip of the blade has the highest velocity and would tend to have the most amount of shit hitting it. Some theories suggest scintillation is caused by certain types of sand or dust (types with a higher ore or metallic content) striking the leading edge.
One reason why you dont tend to see scintillation when an aircraft has landed is because even though the RRPM is pretty much still the same, we have no induced flow coming in through the top of the disc dragging or sucking the air (and any particles) in.
As well as making the aircraft more visible to the enemy, there are issues of this bright glow around the disc affecting NVG (partially shutting them down at a fairly critical stage of flight!)
...

[h=3]Here’s the official US Army’s description:[/h]REDSTONE ARSENAL, Ala. — The “corona effect” is characterized by distinctive glowing rings along metal or fiberglass rotor blades operating in desert conditions.
The glowing rings are made up of numerous small sparks resulting from grains of sand striking a normally-operating rotor blade, meaning the corona effect can be seen only at night.
The corona effect has been seen from about a half mile away on a CH-47 Chinook hovering at about 1,700 feet, said Mike Hoffman, and that without the aid of night vision goggles.
Content from External Source
 
What's crazy is that I never looked into that corona effect before, at least not reading about it, and now that I have I found bunk. That kid who claims there are pieces of metal flying off rotor blades has succeeded in spreading that disinformation across the entire web. I've stood under 1,000 helicopters, with a static discharge probe and rubber gloves, saw that halo 1,000 times, and I've never been in a desert.

One thing that kid completely made up was a metal covering for rotor blades. I read a bit of his site, and it seems like he's a creationist or something a bit crazy.

I always assumed it's static electricity, since helicopters generate a good deal of it, it has to be generated by the rotor blades and you get shocked when you touch a hovering helicopter. It happens all the time too.
 
The UK's MOD does not know what it is:

http://www.iom3.org/news/call-proposals-rotor-blade-scintillation

The UK's Ministry of Defence is calling for research proposals on helicopter rotor blade scintillation.Scintillation, also known as 'the halo effect', occurs when particles stirred up by the rotor downwash interact with the blades. This is a particular problem in sandy or dusty environments. Little formal research has been conducted in this area, but possible causes include triboluminescence, chemiluminescence and electroluminescence.
Proposals are sought to investigate the physics of this phenomenon and how to eliminate it.

16 Feb 2010
Content from External Source
 

Indeed they can be seen on civil turboprops too - the "silver" strip along the leading edge of a "black" blade - the blade is composite on a metal spar, and the leading edge is usually nickel alloy - one of the places I worked as a QA Engineer was a little maintenance outfit SAFE Air, in Blenheim New Zealand, who have a fairly large prop overhaul shop handling props from all around the Pacific. Replacement of these strips was "steady work".

All composite blades on aircraft require them because the composite material is too soft to withstand even "gentle" impacts.
 
Well, your image is a helicopter in a sandstorm, basically sparks from friction of the sand hitting the blades. Not static.

http://sciencebasedlife.wordpress.com/2012/11/01/the-kopp-etchells-effect/
Is.

Screen Shot 2013-05-30 at 23.05.39.png

The dust in the air is a transferable insulator, and the helicopter is a giant Wimshurst machine when it meets a sandstorm.

Screen Shot 2013-05-30 at 23.17.18.png

http://en.wikipedia.org/wiki/Wimshurst_machine

I have shot-blasted in the past and never saw a spark. None of the leading edge materials make sparks.

And Pete - the incredible pressures involved in sonoluminescence aren't created by impacting sand grains.

It is also the effect experienced by the jumbo that accidentally flew at night through the ash cloud of an erupting Indonesion volcano.

They were surrounded in static-induced light. The engines streamed light like searchlights - before they expired.

[video=youtube_share;vPs6XVvrY1c]http://youtu.be/vPs6XVvrY1c[/video]
 
Is.

Screen Shot 2013-05-30 at 23.05.39.png

The dust in the air is a transferable insulator, and the helicopter is a giant Wimshurst machine when it meets a sandstorm.

Screen Shot 2013-05-30 at 23.17.18.png

http://en.wikipedia.org/wiki/Wimshurst_machine

I have shot-blasted in the past and never saw a spark. None of the leading edge materials make sparks.

And Pete - the incredible pressures involved in sonoluminescence aren't created by impacting sand grains.


I'm assuming all items were grounded, that's why you didn't see any sparks.
 
I have shot-blasted in the past and never saw a spark.

Indeed - but shot blasting occurs at a much lower velocity than the ends of helicopter blades move at - shot blasting typically uses velocities of 65-110m/s, A Chinook blade tip, radius 9.15m, rotating at 225 rpm, does about 225m/s - twice the velocity, 4 times the potential impact.

also most shot blasting uses relatively soft shot in order to remove surface materials such as paint or loose materials such as corrosion, and so as to not damage the underlying strata. Shot that does seek to work the underlying material, such as for shot peening, is generally in the form of round particles, so as to "hammer" the material, not cut it.

the sand will probably have sharp edges and be very hard.


None of the leading edge materials make sparks.

titanium and nickel can certainly spark - one of the ways of telling what metal something is made of is to grind it a little and see what sparks come off - titanium gives very hot white sparks, nickel gives dark red ones of short duration.

on the balance I'll still put a $ on hot metal sparks :)
 
on the balance I'll still put a $ on hot metal sparks :)
Well those blades do wear away very quickly in sandy conditions.

But also the static-inducing effects of particulates are very much stronger and permeate through all aspects of atmospheric interactions. I wonder how that helicopter would have appeared at night. Erupting volcanoes are very interesting in the dark.

justanairlinepilot said:
I'm assuming all items were grounded, that's why you didn't see any sparks.
True. And the cabinets were well lit, which wouldn't have helped. But even at the time I was curious enough to look for it, as I expected some static to be there. Sometimes shot blasting was external to cabinets. But there again, Hampshire was a pretty damp place in the early sixties...
 
Jazzy - I do believe the pictures of the chinhook were all taken at night. The camera settings just make it look more light out than it is to our eyes as the camera sensor is more sensitive.
 
Jazzy - I do believe the pictures of the chinhook were all taken at night. The camera settings just make it look more light out than it is to our eyes as the camera sensor is more sensitive.

Yes, the phototgrapher, Michael Yon, says:
http://www.michaelyon-online.com/the-kopp-etchells-effect.htm

The pilot comes in fast, to the dark landing zone, lighted only by “Cyalumes,” which Americans call “Chemlights.” The sensitive camera and finely engineered glass make the dark landing zone appear far lighter. The apparent brightness of the small Cyalumes provides reference.
Content from External Source
He's used a Canon 5d MkII, with some fast glass, $10,000 worth of gear. Possibly one that was modified:

http://www.michaelyon-online.com/camera-auction.htm
2) Special Canon Mark II 5d (full spectrum): I had this one specially modified for shooting in low or zero ambient light. The sensor is sensitive to infrared and is “full spectrum.” It will pick up invisible IR lasers from rifles, Predators/Reapers (Taliban use cell phone cameras to see these lasers), IR sources, including the IR flash I had specially modified. This camera is in perfect condition but the body has dueling scars. This camera is also great for daylight. It will have the IR look and images are usually better with post-processing. Images with this camera can be phenomenal. Also good nighttime surveillance work. Various filters can make it useful for forensics, scientific, or astronomy work.
Content from External Source
He also says
In motion, the halos spark, glitter and veritably crackle, but in still photos the halos appear more like intricate orbital bands.
Content from External Source
So it would seem this is considerably different to how the scintillation would appear to the naked eye.
 
Yes, I gathered it was after dusk somewhat, but not using a special camera.

Particulates in fast moving air always generate static electricity. Hence explosions in coal mines and flour mills, or wherever the powder is combustible. The only way I know to rid that potential from a dusty area is to use that Evergreen jumbo to drop large amounts of water from above the area in advance of the helicopters. Cheaper than a million hippie ionizers?

"Veritably crackle" isn't static, eh? :)
 
[Admin: Thread split from: https://www.metabunk.org/posts/46747

Or is it just friction? Friction creating heat, just like an engine. I don't know, but I know airplane wings don't get hot. I'm just guessing here. It's not static. Static looks like the pic.

Static from a rotor wing is really colorful and pretty and I can't believe there aren't better pictures than this popping up on google images. I had a job in the army that had me standing under helicopters that were hovering so low I could touch them (they were that low so I could touch them), but I never took pictures.

How's my science sound, Mick?

I have over 1500 flt hrs in CH-47 Chinook helicopters. Been deployed to Iraq in 2005 and have seen this many times. The leading edge of each rotary wing blade is composed of an aluminum D-shaped spar. When spinning at 225 RPM, sand is swept up into the air and hits the rotor blade across most of it's length. Aluminum doesn't sparkle but, the key here is that the outboard 36 inches of each rotor blade has a titanium cap bonded to it to protect the spar from.... yeah sand and, it is that cap that is sparkling as the sand hits it. Actually any small, particulate debris will cause this effect.
 
I was 13Bravo Field Artillery in the United States Army and we would sling load our artillery pieces, (howitzers) and have to hook them up to the bottom of ch47's (chinooks) and uh60's (blackhawks) we would use what we call a q tip, specially insulated to connect the howitzer slings to the a tip (looks like a q tip) and the a tip connects to the bottom of the helicopter that has and electric winch like connection that closes around the q tip and. The helicopter hovers directly above the soldier while other soldiers hold the legs of the soldier rigging the howitzer so he doesnt get blown by the turbulence wind from the propellers of the helicopter. I have dobe this hundreds of times at night and even more in the day. What you see in the rotors and propellers of a helicopter is what we call a static load. The q tip is insulated and in winter the howitzer also may need to be grounded into the dirt so that the STATIC LOAD doesn't shock the soldier. This is not a big mystery nor debatable about what it is you see. No spooky phenomenon or anything unusual at all. The propellers spinning in the air itself causes a static charge and that charge can zap you and even kill you if the helicopter is not grounded and you touch it while it is in the air hovering above you. All Artillers soldiers know this as common knowledge. Look at any video online and search, "sling loading towed artillery piece" or "towed artillery helicopter sling load" . It is actually pretty cool to see and can be very dangerous; however, not uncommon at all.
 
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