static electricity
 

Recently whilst in New Zealand i had a coversation with a crewman from the venison recovery deer culling days of the 70's. He remembers a number of time being badly shocked with static electricity whilst hooking loads on H500's, some had static straps fitted to stop this. No word of it when I did my hook/sling endorsement a couple of years ago. Any comment??
helibiz:cool:

Helibiz,
Whoever did your sling endorsment should have covered this. It's a common occurance in sling / winch op's to get static buildup on the line. This static charge will "go to ground" at the first opportunity (ie: through the loadmaster / rescue crewman) if the hook is not grounded before they touch it. Normally, allowing the hook to briefly touch the ground first will cause sufficient discharge, also a well insulated person is less likely to recieve a shock. Dry & dusty environmental conditions will normally make static buildup more likely too.

Not only in dry and dusty conditions. It's a real bitch in the snow. We used a length of light bath plug type chain screwed to the skid at the front crosstube. Didn't touch anything on the helo until the chain "landed" otherwise you'd be on your back.


STL

Zap!
 

When I started training for my CPL, I was asked to hookup a load for a 206 that was going to do some slinging practice. It was a very cold day and nobody warned me about static electricity. So
when I touched the ring on the net to the hook on the ship I got really zapped. Afterewards when they landed - oh, I forgot to tell you...you've done this before haven't you?

When Brisbane sank under the waters of a cyclone and a king tide back in 1974, the RAAF was using Hueys from 9 Sqn to rescue people from all sorts of places. One group of 6 was on the roof of a service station, and the rescue crewman went down first, and got a kick from landing on the steel roof.

He stayed there and helped hook the victims into the sling, and each time he grabbed the flailing wire (still cyclonic winds) he got a boot. The worst thing for him wasn't the kick, but the anticipation of what was going to come each time he reached for the hook.

On a nearby roof were two cows, which had swum up there, and when the waters receded, they were still there. I guess they died when they eventually fell off.:(

It is worse on some types than others.

The old Whirlwind gave off a kick powerful enough to drop the winchman to his knees on touching a boat.

Yes, they did make me go down the wire without warning me :ooh:

In the right conditions (night, dry, etc), you can actually see the static electricity build up on Blackhawks just before touchdown. A little St. Elmo's will develop in a ring on the outer edge of the blades. Usually, this dissipates when the PIC keys his mike. For sling loads, we usually had a grounding hook (attached to wooden pole) that we would touch the line with first... THEN, we'd attach the load.

Not according to you know who.
 

To: RDRickster

You had better watch out our othewise you will incur the wrath of NickLappos. He said a visible discharge doesn't happen on the Blackhawk or on other helicopters either.


:E :E

Let's not start THAT debate again!! ':('

Killed an aircrewman in the late 70\'s I seem to remember (RN - S61). It was determined after an autopsy that his heart was \'dicky\' and the static did the rest.
It\'s at its worst in damp conditions.
It is now a compulsory briefing point during emplaning/deplaning (under health and safety).

A BK117 self incinerated at Buttonville early in the 80's ,there were a whole wack of SB's concerning grounding after that incident. Do composite blades pick up more static than metal ones ?.

Back in 1963 in Culdrose some static tests were done on a Wessex MK5.
From memory up to 100000 volts were generated in less than 1 second. Obviously the current was minute otherwise I'm sure there would have been some big problems. This meant that after you earthed the hook, if you let go, the static would be back within 1 second. This meant you either had to re-earth or have a line attached to prevent build up.
On one occasion when I was in a low hover, a Royal Marine sergeant jumped out but held onto the door handle. He performed a beautiful double summersault with pike on landing! The build definitely varied with both surface and weather conditions but I don't recall anyone being injured. I've had worse shocks off my car engine spark plug leads.
Small helicopters never seemed to be a problem and thick rubber gloves seemed to do the job.:cool:

widgeon,

Conductance of structures is an important part of the qualification process, especially with lightening. Look at the bonding straps, and the underlying conductive mesh or film that we use on composites to assure that they behave electrically as if they were metal.

I think that the static electricity build up is a function of the mechanical static charge generation in dry snow or heavy sand. The ground crew should alsways use a grounded insulated wand to draw off the charge when they hook up loads. Letting the hoist hook touch first is also SOP.

The voltage numbers are impressive, it takes 25000 volts to make a spark that jumps 1 inch, for example. But voltage is only the measure of the electrical pressure that has built up, and does not tell us what is the amount of electricity that can flow. The charge (total amount of electricity) is quite small, so the net damage this spark can cause is small.

Really bad cases of charge build-up cause St. Elmo's fire, which is beautiful. I have had this on airplanes in clod dry snow, and it is beautiful but harmless (unless it affects the radios enough to blank nav and comm!)

This subject is often mixed up with the sparks seen on NVG films (or described by NGV wearers). Those sparks are not static caused, they are piezoelectric, caused by the sand crystals emitting when they are bounced off the blades. Crystals do this as their internal electron balance is shuffled when they are deformed. These electrical effects are why crystals are used on the tips of phonograph needles, where their small voltages are amplified as music, for example.

I managed to poleaxe a camera man whilst passing a film upto my heli in Sweden.
The clearing being covered in snow and hidden tree stumps my wescam cameraman lent out of the door to retreve the film. there was a bang my cameraman had discharged through his finger to the man in the snow. (Bet his girlfriend loves him!). Man in the snow now lying on his back with that look of whats just grabbed my up the **se. (Without the smile)
Now having problems hovering as the crew were laughing so much.
Only after the event did i remember the Dry cold Air effect on Heli's.
Lesson learnt!

It doesn't matter how much emphasis you put on the static problem when briefing a new ground crew, they always forget. Always keen to be the first to catch the hook, the new groundcrewman will reach out, grab the hook then snatch his hand back as the shock hits him- lesson learnt - they don't do it again.

I was caught out myself during a session with 4 pilots doing underslung training. The ground crewman was complaining that despite having a static discharge pole he was still getting shocked. I volunteered to go on the ground and "show him him how to do it". Holding the static pole in my hand, the aircraft (AS332L) came to the hover above my head. I touched the hook with the pole to discharge the static, put the pole down and holding the strop (which was touching the ground) I reached up to grap the hook. Although the aircraft had been earthed less than 5 seconds before, the charge that had built up gave me a hell of a shock. The only way round it was to keep the aircraft earthed with the pole in one hand until the strop was hooked up.

One of the funniest moments was when picking up a package from a site where we couldn't land. We came to a low hover and my crewman leant out the cabin door to pick up the package from a man on the ground. There was a scream from the back as the aircraft's static charge earthed itself. The aircraft had earthed itself across the gap between the crewman's microphone and his lips and then through his body to the man on the ground. My crewman couldn't speak coherently for about ten minutes as he cussed and sweared about the burn on his lips. My ability to hover accurately was totally lost whilst I and the rest of the crew dissolved into hoots of laughter.

I've seen GIs knocked completely off 2.5T trucks by the static charge from CH47s if they failed to discharge the static buildup. It's quite a fall from the top of a fully-loaded truck to the ground, but airborne troops cannot admit pain. :} I used to do lots of sling work in 206s in the GOM, and always briefed the roustabouts about hitting the hook quickly with the becky, but some never learn, and got a jolt even down here in the humidity.

A little spark will go a long way...
 

Some helicopters are designed so that the static buildup on the rotor blades is carried directly to the airframe bypassing the transmission. On some helicopters that have elastomeric teeter bearings the charge can not get to the airframe nor can it pass through the transmission. This is true for the Cobra models like the AH1-J and the Bell 214. On these helicopters the static charge forms a torroidal magnetic field around the rotor disc with this field centered on the main mast. This causes magnetization of the mast and the steel parts on the rotorhead. This can also happen on the Bell 412. The level of magnetization is far in excess of that allowed in the Bell overhaul manuals when a part is Magnafluxed and then degaussed. This can result in minute electrical charges flowing across gears and bearings in the transmission causing spark discharge erosion. This also happens on those helicopters where the static charge is drained to the fuselage through the transmission.

:E :E

Helicopter Static Charge?
 

I was watching one of those most amazing video shows and they showed a helicopter doing a rescue from a car that was stuck in a flood. As the guy got off the helicopter and on the car then got back on it said he got shocked a little because the helicopter builds up a static charge. What's the deal with this? It was an MD500 if that makes a difference.

Thanks

No I dont think its a 500 thing, just a helo thing.

When I was required to repel from helos both Huey's and Blackhawkes & get winched into them, we were always reminded to make sure that the shackle was stomped into the ground to discharge the static built up by the rotors.

If we didnt ground it enough, we would recieve one hell of a kick that removed any feeling of that hand/arm/shoulder for a few days.

Some times there would be more static or it built easier when the air was dry and dusty ( Australia you say ...no.. really? ) and that also made it harder to earth by stomping it into the ground.

Some times the Loady would yell/ hand signal at us to ensure we kicked the !!!! out of it so that we wouldnt get shocked.

Some times one of the boys was a little too impatient to kick it in good and would pay the price.
It happens when you have a lot going on and your on a warm excersise simulating that 2 way rifle range.

( it can happen when the ground is really dry and doesnt conduct so well ).

I have not been booted but can attest to friends not being able to hold their own rifle/kit and complain about their hand etc throbbing really bad and loadies :E like a school boy.

No burns that I saw, just a lot of un happy chappies.

I made the mistake when in briefing of asking pilots what happens to us when we are being slung underneath and they have an engine failure ( 1 or both depending on how many it had ) and the answers were always " Don't worry mate, we will look after you".

See now being under the helo at 50 odd foot and us being more than 50 off the ground always made me think that we are going to get an early flying lesson as no one would ever tell me what their plan was.
I assumed we would be cut away and they would attempt an auto ( whilst being right in the middle of the HV curve) & hopefully the spinning separating parts are further from us.

Any one able to elaborate on this?


Cheers HF

Saw the spark once when in drizzle conditions the ole mate on the ground hooked me onto a load in the MD500 ...didn't laugh honest !!:oh:


SL

Yes, the kick is real. Doing flood relief, we winched the rescue crewy down to a rooftop, and he then had to load the stranded people onto the hoist each time we sent the horse collar down to him. In the drizzling rain, he got a huge kick every time the collar came down - he had to grab it in the gusty winds, no chance to let it earth itself.

He took it 6 times in that sortie, we recommended him for a bravery award at the end of the week and he was rewarded with a medal.

On the other question about a "tea-bag" when the engine fails:
The briefing was to let the tea-bag touch the ground, then use the cable cutter to let him go, so he won't get dragged away by the aircraft.:sad:

That's assuming the aircraft predicament allows enough time for the crewman to operate the cutter before other things overtake him.

Working on a Lama operation in Scotland I watched in horror as a new loader (Australian)
was catching the incomming ag buckets on a very wet day . His eyes were almost lighting up and his hair was standing on end.

I went to tell him to desist and allow the buckets to earth out before touching them.

I was stopped by the other loaders (New Zealanders) who apparently had told him that they all had to do it and were enjoying the show!!!!!!!!!!!!!!!!!!!!!!!!


Wet humid days are the worst and composite blades seem to generate a larger charge than metal.

The worst shock I saw was caused by a 365C which was enough to throw the loader several feet.

(Addition)

I spoke to the guy who got zapped above. It was actually an S58T that did the damage (shows how the memory plays tricks). He said that it felt like he had been hit by a pickaxe handle. Apparently the 58 would build up static so fast that just earthing it out momentarily would not work.

When I was doing my training I volunteered to hook up a sling to a 206 on a very cold winter day. Even though I had gloves on I got a real jolt when the hook on the machine touched the ring on the line which I was holding.:{

No one ever heard of using a zapper snapper then? A simple piece of wire attatched to the winch hook that dangles below the winchman to dissipate the static before he does.

The charge varies with helicopter size and ambient conditions. When there is lots of dust in the air, rain or high humidity the chances of being shocked are much higher due to the increased friction. But operating with a mid sized helicopter like a S76 the average shock rarely exceeds something you may get off a car door. Being paranoid about the shock off a wire is not smart if you are in the water awaiting rescue as you may only get one chance to grab the strop in bad weather, and waiting for it to be earthed nicely alongside you may take a while.
The technique of ‘stomping’ the hook into the ground with your foot will certainly remove a charge, but is not the best practice for a very thin piece of live saving wire that is about to haul you to safety.
Watching three crew members in a submarine conning tower back away from my out stretched hand one day would have been amusing had I not known how hard the boys were working to get me onboard in the reasonable swell and fading light. After about the fourth swing past and one smash into the side of the conning tower, I pulled a shot-bag from my leg pocket that was connected to 15’ of H.I. line. I hurled this at the occupants and when it bounced off one of their heads and into the tower I yelled, “its Fu@ki@g well earthed now!” The bloke we were going to get was then recovered with just a few more heartbeats depleted.

Try using a section of broom handle,with 4-5 ft of thin chain attached.As the hook comes in,make sure the chain is touching the deck,with the pole making contact with your hook etc BEFORE grabbing it,or guess what.......you'll end up like the ready brek man!,especially in hail/damp conditions.:eek:

syh.

Just reading the title of this thread cracked me up!! I spent 8 years logging/fighting fire underneath helicopters in BC Canada in everything from 206, A-Star, 500, K-Max,61, KA 32, 107's etc. Especially in the rain or with thunderheads nearby it got really bad. Sometimes under the bigger machines, a perfectly delivered hook would arc at you from 6 or more feet! would put you on your knees sometimes. Turned out in that kind of crazy work it was a right of passage...when the machine costs so much, you better hook up asap!

With experience you would find that sometimes the 5-6 foot chain dangling from the bottom of the hook would fall/rip off throught the timber...you would learn to set yourself up in or nearby a bush and let it hit that first and then quick as a bunny lunge toward the hook. Sadly not even that worked all the time. It got really funny with the rookies when they got their first arc...they would arc out and then pull back, only to let the hook charge up again and BAM. repeat as necessary LOL.:} You knew it was really bad if you were in blowing snow and you could sometimes not see the helicopter 1/2 a klick away but you knew where he was cause of the blue arc nailing the guy on the ground!!! Show's up really well in the snow.:eek:

Last but not least try this...often when breaking in a new hooktender and finally letting him at the hook we would wait untill a good wet rainstorm. We would set him up high and in the open on a big stump with a handfull of steel chokers in his hand.:E Being the keener he usually was (including yours truly) he would slam those chokers towards the hook only to get blown off his feet by the charge. It was funny back then. The saying always went "Real Men Take the Arc!" :ugh:

Those times have since past and I being a responsible pilot towards my customers, always remind them of the tricks I learned then cause boy o boy do they get pissed when they get a kick! I'll put it on the ground too sometimes, especially when it's really dry, or really snowy.:) Customer relations and all that

BWB

I guess there is no Health and Safety Executive in Canada then:)

Crab old Man,

The Nanny State syndrome does not exist in all parts of the world....and as is proven by many posts here.....we continue to thrive and even enjoy a bit of a laugh while at our workaday employment.:rolleyes:

If you were a swimmer in water being rescued and the hook touched the water would the shock be great enough for you to feel it just by being in the water?

If your the one being rescued, you wouldn't feel the zap unless the hook / basket hit you first. The zap is not that strong as to travel to body in the water.

If you are the rescuer on the hook going into the water and the conditions are right for increased static electricity, you will feel it. Some times you might even bite through your tongue as a result of the zap.

Beware!

A zapper snapper is a good idea when the conditions warrant it. (Have been using our three metre length of old hoist cable for years but never had a name for it until now - Thanks [email protected])

Regards
Breeze

A friend of mine in Norway who used to fly Lynx Mk. 86's once told me a story of a SAR Swimmer who was jumping out of the machine in a low hover to straighten the main wheels for taxiing.

He forgto to undo his helmet cord, and promptly started jumping up and down with a "AHHH!" every time he hit. And the helicopter was hovering in nice wet snow falling...

My friend was struggling to keep the helicopter in control as he watched the SAR swimmer keep up his show, until the F/E got the cord unhooked...

He did survive it tho.


As to Canada and Health and Safety in the workplace, it seems that "production" and "Speed" are more important than safety sometimes. Have on numerous occasions mentioned the "broomhandle with cable touching the hook and ground", but have been over-ruled as it seems this would take valuable seconds away from the work...

Cheers
W.

Easy there Winnie,

What I expressed were my experiences as a young lad doing a job which very few do or have done, nor do I recomend it in my later years (just a few more than you but not by much) We were by no means special forces but tough bastards all the same and earned our money the hard way. After 8 years I only know of one man that died doing it on the ground and it was NOT from the "arc". On the other hand I know a few pilots that have passed on doing anything but "production" work as most of us here do. To put it bluntly my experiences on the ground are by no means a reflection of the aviation (ie Pilots/Engineers) community in Canada and our commitment to safety. It was not my intent to give you all a false representation of a cowboy attitude. It's just that a few of us that have worked both sides have a different perspective as I bet your SAR Tech does now after his experience.

Fly Safe All

BWB

Apologies to you BWB, I did not put it clearly that those were my opinions, not reflections on you!

I meant as a sweeping generalization that things here (and in my country of origin too unfortunately) production, fast, quick are words that go before safety and comfort.

I know nobody has been killed because of static discharge, but it is DARN uncomfortable, and can be easily avoided. But that takes time.

Again, sorry, not directed at you.

Cheers
Winnie.

Point taken and thanks

BWB

We were lifting 40ft Containers in East Timor with the Mi26 and had a few Local guy's trained(As best we could) to do the hook up's. One of the boys forgot to ground the hook and it Blew him off the container and straightened his Curls...Very Funny!!!:):):)

In the AAC we used a home made hook, cable and spike system where as the loader gets under the machine he simply whacks the spike into the ground under the machine and puts the hook over the back of the skid thereby grounding the aircraft prior to hooking up the load. If we didn't have one then you just hang onto the plastic sheathing on the stropp and touch it to the hook first before touching the machine. Once saw a RAF loady get zapped off the top of a truck by a Chinook - not funny!!!!:eek:

In submarines we used to do helo transfers to the top of the fin (conning tower to non submariners). We had to have a man with an earthing pole grounded to the boat to remove the static charge from the winch cable before the person being winched touched the metal submarine. If we really didn't like the person on the winch strop all sorts of offers of money beer and rum would be made to the man with the earthing pole to touch the visitors leg, body or delicate areas with the pole, causing the charge to be earthed through the body part touched and thus extreme agony in the nether regions for the next week or so! :D

Helicopter Electro-Static Discharge
 

Anyone know of any good online articles explaining this phenomenon.

I am researching this as one of our aircraft suffered a big discharge the other day causing some damage.

Your ground hook is your friend.

http://hedge36.smugmug.com/photos/141347179_Jb43s-L.jpg