Corona discharge revisited....

[Lu Zuckerman]

I just got this in my E-mail. I sent the question in four or five months ago and they finally answered my question:

Dear Lu,

Sorry to be so late in responding. Just came across your note last week. Your definition is correct. Each particle (any particle) striking the blade adds a small charge to the blade. In turn, this is discharged, typically as a corona discharge, and may be visible to the eye and certainly with night vision goggles.

The piezoelectric event mentioned is new to this writer. (This was in response to what Nick and several others said) Striking a crystallized structure (sand) can generate energy. i.e. a piezoelectric reaction with this one crystal. Imparting a static charge though is assumed to be the prominent phenomenon here, i.e. static charging of the blade which in turn is discharged.

Best regards,
DAYTON GRANGER, INC.
Karl H. Blomgren
Director of Marketing
TEL: [phone]
FAX: [phone]

(Please, no snide remarks about the writer of this E-mail message)

[helmet fire]

Lu,
What a great defence of your superbly reasoned arguement.

Just a few small questions if I might.....

What was your question to him? How did you represent the discussion to him? Who is this man? Will this devolve into another "but Frank Robinson said...."?

Basically, I could sumarise the above with: What are you on about?

I have a good feeling about this thread!

[Lu Zuckerman]

What am I on about? If you don't know by now I'll have to spell it out.

To: helmet fire

What was your question to him? How did you represent the discussion to him? Who is this man? Will this devolve into another "but Frank Robinson said...."?

First of all this has nothing to do with Frank Robinson although under the right atmospheric conditions it could.

I presented my arguments posted on the previous thread along with the arguments of my detractors including those of NickLappos who said you could not see the corona discharge with the unaided eyeball.

Who is this man? He is the Director of Marketing for Dayton Granger the largest manufacturer of aircraft radio antennas as well as the largest manufacturer of static discharge wicks used on aircraft and helicopters.

If you don't believe me in that I originally stated that I could see the corona ring around the rotors of the B-214s and the AH1-Js while in Iran then his contact information is indicated above. Ask him what the mechanics of corona build up and discharge are.

[IHL]

I discharged several Coronas; just last night.

Good beer!

Sorry I couldn't help myself.

[belly tank]

IHL!

I was thinking the same thing then i got to your post!!...

technically though i think you discharge after you've had too many coronas!!

sorry Lu didnt mean to take the light off your post, interesting though

BT

[Hilico]

On Discovery I've seen pictures of a Blackhawk landing at night, seen through a night-vision camera (everything is a shade of green), and most certainly there seem to be streaks of fire constantly flickering round the disk. Thanks for explaining it.

[Sailor Vee]

Lu '

We certainly used to get this effect, both on UH1s and 214Bs, that was in SOAF.

The effect was a lot greater in damp atmospherics, (during the khareef (monsoon) and landing on an area not far from a beach).

[NickLappos]

So Lu, you write the guy who sells static discharge equipment to continue your crack-pot ideas that the sparkles we see on NVG pictures of helos is static electricity discharge. This thread is about 2 years old, I guess you never forget, do you? You are wrong, yet again.

Sailor Vee, the reason why you saw the lights near the beach is that sand is the best stuff for piezoelectric sparkles. Note your comment about wet conditons, which also prove that it is not static electricity. In wet conditions, the static wicks off through the atmosphere easily.

To review: The flashing light seen on rotor blades in NVG's is almost entirely due to the impact of sand/stone particles on the blades when they are struck by the blade. The sand/dust is made of crystals that react to mechanical disturbance by creating light, one of the properties of the electrically bonded crystal lattice. It is this piezoelectric effect that is why a phonograph needle works. The needle is attached to a piece of crystal that has wires attached. As the needle bumps in the record groove, it disturbs the crystal, which emits tiny voltages that are amplified. Those voltages and the tiny light flashes are made by the crystal's internal electron balance, which is reshuffled when the distances between atoms in the crystal change.

Here are two photos that show the effect, please note that the effect is only there when the aircraft has dust around it, because it is glowing dust that we see, not glowing air. Note in the below photo how the particles are flying around the blades, and only at the high speed tips, where the disturbence is enough to make the dust glow? If it were static electricity, it would be a neon glow in the air around the entire blade, not just the tips. In some photos I have seen, the glow can be seen as a discrete bunch of glowing tiny particles. Those particles are the sand glowing extremely faintly after having been struck by the blades. See the dust swirling around reflected in the landing lights, it is this dust that causes the light.






Here below is proof it is not static discharge. The aircraft in this picture is on the ground, where the static electricity is dscharged thru the landing gear, but it still has the glow. No static electricity on the ground LU, None. Note the dust around the aircraft. Dust = sparkly lights, not static electricity = sparkly lights (BTW, the Black hawk has very very good blade electrical bonding straps to conduct lightning away from the blades, the static discharge on the ground is excellent)




Here is a link that explains the effect, and discusses how to do it at home wth sugar cubes and wintergreen lifesavers (I can't make this up!!)

http://www.geocities.com/RainForest/9911/tribo.htm

And to beat this very very dead horse (but this link is worth it!) here is a qucktime movie of a guy scratching a crystal with a nail, the sound is the nail, note the light flashes. Remember, goggles are monochromatic, so the color wont match):
http://mywebpages.comcast.net/jtozou...minescence.MOV
according to the US Army, "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."
http://www.rdecom.army.mil/rdemagazi...dec_boots.html

[zeeoo]

the truth revealed :

army already uses MHD plasma parietal accelerators !

end of the joke

[Lu Zuckerman]

In response,

I sent this entire thread to Dayton Granger for their comment.

In reading the comments of the engiineer at Redstone Arsenal it appears that he saw the corona discharge on a CH-47 at some distance away. You can see the effect with the unaided eyeball.

[NickLappos]

Not Static Electricity, Lu. Not They are sparks from rocks being hit.

[Lu Zuckerman]

I couldn't think of a title.

To: NickLappos

Nick if you go back to my original postings on this subject I alluded to an energy exchange when the blade is impacted by an airborne particle. If what you say about the piezoelectric effect causing a spark maybe that is true. However the fact that a spark has been generated the electrical energy is transferred to the blade and if the charge can't be dissipated through a discharge via the fuselage then it will be dissipated from the blade tips forming the corona around the disc.

Not Static Electricity, Lu. Not. They are sparks from rocks being hit.

If it is not static electricity then please explain the following. The rotorheads on the Bell 214 and the AH-1J are mounted on elastomeric bearings. There are no static dissipation ground lines on the rotorhead so whatever charge on the rotorhead stays on the rotorhead. This static electricity forms a torroidal field around the rotor and is centered on the mast causing it to magnetize. The level of magnetism is many times that allowed after degauss following Magnaflux ™

The magnetic properties effect the gears and bearings in the gearbox as well as effecting the VOR equipment on the helicopter as well as effecting the standby compasses. Would this be happening if the sparks were only a piezoelectric effect caused by miniature rocks and dust impacting the leading edge of a rotorblade?



.

[NickLappos]

Lu,
See the picture of the Black hawk above. It HAS all the bonding you could ask for. It is on the ground, statically grounded to the earth. Yet it shows the "corona"

Why don't you explain that.

[RDRickster]

The outcome on this one will be interesting!

Once upon a time, when I spent my evening hours carrying various machine guns, this phenomenon was quite common when working in tactical conditions. From my limited observations, I would agree with both Lu and Nick (maybe for the wrong reasons which will hopefully show themselves on this thread).

No doubt that sand and other particles will cause the effect. Nevertheless, I've seen the ring WITHOUT light amplification devices. Furthermore, I've seen this ring of visible light DISCHARGE when the pilot has keyed the microphone BEFORE wheels down (UH-60 example). No landing area has been "clean," but I've seen the visible light over concrete areas as well as jungle clearings and desert areas.

Now, I'm confused as to what I was looking at. In any event, the site of an incoming Blackhawk during extraction was enough to give Viagra a run for it's money each and every time. Ah, memories...

[zeeoo]

hi gentlemen,

i hope you dont mind my posting ?
look down. a little voice coming from a little knowledge..sorry.. you re so high for me..

i saw these pictures and was amazed....

ok i know the quartz properties on 3 axis, due to my earlier electronics school..

but some questions if you please...

- if sparks come from impacts, why no spark on tail rotor ?

- did you try to take a piece of blade and sandblast it with a fine
silicium powder?

- can this only be due to tribolumin. ?
Because WintOGreen Lifesavers are naturally fluorescent, now step two can take place. The "lightning bolts" give off invisible ultraviolet light you must have good eyes gentlemen to see that

- arent the blach hawk blades made of composites with a titanium leading edge of somthing like that ? do you think the friction with air could ionize the surface then it could produce a discharge, BTW the sea air has alot of Iode and salt, great for electricity.. not talking about plasma.. but isnt there a marine phenomena apearing on vintage boats on it's metal parts called "st elme' fire" the ancients mariners took for chance sign because the came after tempests?

- was this effect searched in a clean room and dry air

excuse my poor arguments and questions gentlemen... i just cant believe sand strikes can do this...

thank you

[zeeoo]

i think i was not so wrong on my intuitions....
after a little search i post this in french and the same in english :

Comment se produisent les feux de Saint-Elme?

Dubois Sip Scache

Le feu de St-Elme se manifeste par des lueurs apparaissant aux extrémités des mâts des navires certains soirs. Ce phénomène est une manifestation de «l'effet couronne», qui se produit lorsque le champ électrique à proximité d'un conducteur est assez fort pour provoquer une décharge dans l'air ambiant et ainsi exciter les molécules d'air qui émettent alors une lumière caractéristique. Expliquons maintenant plus en détail.

Si on charge un objet conducteur, les charges électriques vont se répartir à la surface de l'objet, de manière à annuler le champ électrique à l'intérieur de l'objet. La densité de charge électrique (par unité de surface) n'est pas uniforme sur toute la surface de l'objet, mais est beaucoup plus grande sur les aspérités et les pointes. En particulier, si l'objet est un navire, la charge électrique est concentrée sur les pointes des mâts et des vergues. Malgré les apparences, un navire est un objet assez conducteur, même s'il est en bois, car ce bois est recouvert d'eau, et l'eau de mer est un assez bon conducteur. De plus, le navire est en quelque sorte une pointe sur l'océan, lui-même une surface conductrice. Le navire peut donc facilement accumuler une certaine charge électrique, car l'océan possède une charge induite en surface du fait qu'un champ électrique vertical considérable (typiquement 100 volts/mètre) règne entre le sol (ou la mer) et la haute atmosphère.

La forte densité de charge accumulée sur les pointes donne naissance à un champ électrique important dans le voisinage de la pointe (ce champ est proportionnel à la densité de charge par unité de surface). Ce champ électrique accélère les quelques électrons libres qui se trouve dans le voisinage (il y a une faible concentration de molécules ionisées par des rayons cosmiques) et ces électrons peuvent acquérir suffisamment d'énergie cinétique pour à leur tour ioniser d'autres molécules de l'air au voisinage de la pointe, libérant d'autres électrons qui sont accélérés à leur tour, et ainsi de suite. Il existe donc un faible courant qui passe de l'atmosphère vers la pointe (normalement les électrons sont repoussés par la pointe car la charge induite à la surface de la Terre est négative). La recombinaison des électrons avec les ions s'accompagne de l'émission
de photons (de lumière) et c'est cette lumière qui est le feu de Saint-Elme proprement dit. Pour que le phénomène se produise, le champ électrique doit être suffisamment fort pour accélérer les électrons à une vitesse minimum avant que ceux-ci n'entrent en collision avec les autres molécules, sinon celles-ci ne peuvent être ionisées. C'est pour cela qu'on observe le phénomène à proximité des pointes seulement.

from an online translator : i changed some "funny" words

How occur the fires(lights) of Saint-Elme? Dubois Sip Scache Le fire(light) of St-Elme shows himself by lights appearing to the extremities of the masts of the certain ships in the evenings. This phenomenon is a demonstration(appearance) of " the effect crown " [translate : corona effect], which occurs when the electric field near a conductive is rather strong to provoke a discharge in the pervading air and so incite the molecules of air which emit then a characteristic light. Let us explain now more in detail. If we load a conductive object, the electric loads are going to divide up on the surface of the object, so as to cancel the electric field inside the object. The density of electric load (by unit of surface) is not uniform on all the surface of the object, but is much bigger on the harshness and the points. In particular, if the object is a ship, the electric load is concentrated on the points of masts and yards.
In spite of appearances, a ship is a rather conductive object, even if it is wooden, because this wood is covered with water, and the sea water is a rather good conductive . Furthermore, the ship is in a sense a peak on the ocean, itself a conductive surface. The ship can accumulate thus easily a certain electric load because the ocean has a electric load on its surface due to the fact that a considerable vertical electric field (typically 100 volts / metre) exists between the ground (or the sea) and the high atmosphere. The strong density of load accumulated on points gives birth to an electric field mattering in the neighborhood of the point (this field is proportional in the density of load by unit of surface).
This electric field accelerates some free electrons which is in the neighborhood (there is a weak concentration of molecules ionized by cosmic rays) and these electrons can acquire enough kinetic energy to ionize in turn the other molecules of the air in the neighborhood of the point, releasing the other electrons which are accelerated in turn, et cetera. There is thus a weak current which passes of the atmosphere towards the point (normally electrons are pushed away by the point because the load on the surface of the Earth is negative). The recombination of electrons with the ions comes along with the emission of photons (light) and it is this light which is the Saint Elmo\'s fire strictly speaking. So that the phenomenon occurs, the electric field must be enough strong to accelerate electrons in a speed minimum before these collide with the other molecules, otherwise these cannot be ionized.
It is for it that we observe the phenomenon near points only.


thank you for your attention gentlemen

BTW corona with a lemon slice ....mmmmm i d like to revisit it !!

[NickLappos]

St. Elmo's fire is a true corona effect, and is remarkable and looks like an envelope of glowing gas, because that is what it is. I have seen it on the wings of my airplane once, it is beautiful and ghostly. Note that the explanation of St. Elmo's fire discusses the need for the ship to build a strong electric field relative to its environment. This is what Lu has been saying, and is one possible source of light, were the aircraft not grounded.

The stuff that we see in night dusty operations is not St. Elmo's fire. The bright sparkles are each discrete particle of sand emitting light when it is struck by the blade. The blade is going about 450 knots in a hover, quite enough to shock the sand into glowing (which also hits the blade hard enough to erode it harshly).

Note the flashes at the rotor while the aircraft is grounded. St Elmo's fre is quickly wicked off when the bonding system of the aircraft is touched to ground. Look at the left landng gear to see the grounding wire. Also, note that the flashes only occur when enveloped in the sand.
In many events that I have observed (and in the posted photos) you can actually see the scintillation from each grain because the lights are not a gas corona but rather a sparkling mass of points of light, each a particle of sand that is emitting light.

The scratched crystal in the site I posted is a direct example of this type of light.

[Lu Zuckerman]

In response to your question.

To: NickLappos

See the picture of the Black hawk above. It HAS all the bonding you could ask for. It is on the ground, statically grounded to the earth. Yet it shows the "corona"

One answer to your question is that the static charge is building at a rate faster than it can be dissipated.

On a cargo pick-up or drop off the man on the ground has to ground the static charge on the airframe and he must maintain the ground. If he doesn't and he touches the cargo hook he can get knocked on his ass. The same is true when making a hoist pick-up over water. The winch cable must be dipped in the water to drain the charge. If the pilot lifts the helicopter up a bit in the hover and the hoist cable comes out of the water and the person in the water touches the cable he can be rendered unconscious. That is how fast the charge can be built up. In the case of the Blackhawk in the picture I can assume the grounding cable was on dry earth with minimal conductivity allowing the charge to build up.

Now, I have answered your question (right or wrong) I would like you to comment about the torroidal magnetic field around the 214 and the AH-1J

[zeeoo]

nick, with respect to you, i just knew who you are..

but i still asking, why not on the tail rotor? and have tests been done in a lab to confirm that ?

has it an great importance except for erosion ?
BTW if a quartz cristal emits light it also emits electricity, or am i wrong ?

thank you

victor

[NickLappos]

zeeoo,
I have seen the tail rotor excite the particles at night, also. the photos I pulled off the net don't show it.

The effect I describe is actually also electric, in that the crystal glows because its electrons are disturbed and flow within it to make the light (and also some electricity, as I described in how a phonograph needle works).

Lu thinks the charge builds up faster than it is carried off, but that is dead wrong, because otherwise the way we ground helos for load pickup wouldn't work either. Lu can never drop his point, so I will stop debating this about now. It takes photos, a US Army web site that says "The glowing rings are made up of numerous small sparks resulting from grains of sand striking a normally-operating rotor blade", a guy scratching a crystal and Lu still prattles on about it being static electrcity. I can wait another 2 years for you to fnd a letter from a company that sells oat meal cookies, and they can help your case, perhaps.

Lu, I do not know what the hell a toroidal magnet on a Bell has to do with your mistaken belief that we see the sparkles on a rotor blade because the rotor is drinking Corona beer. Pray, don't tell me, let me remain forever uninformed!