Helicopter Static Charge?
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I have hooked loads onto the S61 on land and ships and in conditions ranging from hot and dry to cold and wet and found the "best way" to handle the shock if a ground pole was not available was to grab the strop as firmly and as hard as you could.
It still bites
but not as bad as tip-toeing around the spark.
It still bites
but not as bad as tip-toeing around the spark.
Quite agree - suck it in man! Grab it quick - what are you a man or a mouse?
Always a pleasure using the old chain, cable, hook method to ground the aircraft. Even better if you managed to convince the u/t pilot "helping out" that the best way to make sure that he didn't trip over the chain ........ was to put it in his pocket.
eeeeeek eeeek eeeeeek
Always a pleasure using the old chain, cable, hook method to ground the aircraft. Even better if you managed to convince the u/t pilot "helping out" that the best way to make sure that he didn't trip over the chain ........ was to put it in his pocket.
eeeeeek eeeek eeeeeek
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What limits
I think the physics is quite simple. Just like rubbing a balloon on your jumper, really. If it is simple, then........ (if not simple then someone who knows what they are talking about will be along shortly!)
The rotating blades impact molecules (like balloon and jumper) and the impact knocks electrons off the outer orbit of an atom. That molecule becomes + charged and the roter takes on a - charge. The one molecule is left behind, but the rotor hits more molecules and so builds a bigger - charge. The - charge then affects the whole airframe.
When the potential difference between the machine and earth is greater than the resistance of a path between the two, a spark runs up from the ground to the machine along the path of least resistance, earthing the charge on the machine. The longer between earthing, the more molecules to hit (eg rain) etc the bigger the - charge built on the airframe before earthing.
The spark has very high voltage but no amps - it is static electricity. Hence a BIG impact felt if it earths through the loader with little damage. The charge can get big enough, however, to create spark erosion type damage at the point where the charge earths from the airframe. I would guess that damage to electric components is theoretically possible if the charge is big enough but the size of the charge would be getting towards "Lightning" (same process) value.
I think the physics is quite simple. Just like rubbing a balloon on your jumper, really. If it is simple, then........ (if not simple then someone who knows what they are talking about will be along shortly!)
The rotating blades impact molecules (like balloon and jumper) and the impact knocks electrons off the outer orbit of an atom. That molecule becomes + charged and the roter takes on a - charge. The one molecule is left behind, but the rotor hits more molecules and so builds a bigger - charge. The - charge then affects the whole airframe.
When the potential difference between the machine and earth is greater than the resistance of a path between the two, a spark runs up from the ground to the machine along the path of least resistance, earthing the charge on the machine. The longer between earthing, the more molecules to hit (eg rain) etc the bigger the - charge built on the airframe before earthing.
The spark has very high voltage but no amps - it is static electricity. Hence a BIG impact felt if it earths through the loader with little damage. The charge can get big enough, however, to create spark erosion type damage at the point where the charge earths from the airframe. I would guess that damage to electric components is theoretically possible if the charge is big enough but the size of the charge would be getting towards "Lightning" (same process) value.
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The helicopter effectively forms a Faraday Cage around the electronics.
Same as a F.W. aircraft,= damage is extremely remote.
In-service aircraft are hit by lightning every day, somewhere in the world.
Damage is usually due to broken bonding straps between surfaces.
How come Helo's don't have "wicks" to dissipate the charge?
Same as a F.W. aircraft,= damage is extremely remote.
In-service aircraft are hit by lightning every day, somewhere in the world.
Damage is usually due to broken bonding straps between surfaces.
How come Helo's don't have "wicks" to dissipate the charge?
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Hmm I have managed to weld the static discharge lead to the deck of the ship that I am landing on, and have been in the un envious position of being unable to grab the rails of a boat... Got it ..nah shock... got it nah shock....got it nah shock.... lots of times! Static discharge leads do work, but I have been defibed more times than I care to think about!
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!!!
I find it depends upon weather . have been using a 500d for brash lifting here in Uk. Have moved 10000 bags 4 to 5 at a time, haven't had a belt at all although we haven't been flying in wet weather which normally seems to generate a charge
During a winchex in the 80's from a Sea King the winch man we were collecting after the first cct grabbed the harness assembly before it grounded. He collapsed and his heart stopped. He was resuscitated eventually and went on to a fullfilling career. They estimate a charge in excess of 40,000v can be generated in the right circumstances but obviously only with a small amperage.
I haven't heard of any (professional) unit that winches/hoists/sling loads without an earthing strop?
I haven't heard of any (professional) unit that winches/hoists/sling loads without an earthing strop?
H-53E can be really shocking
The static discharge from the C/MH-53E is very significant. The ground crews use a Sheppard’s hook with a grounding wire to ground the aircraft prior to touching the hook during load hook ups. The system also incorporates a grounding wire from the hook up the pendant providing a path into the airframe. There was at least one instance where the ground wire became detached as the pendant stretched during a 32,000 lb lift. In this case the crewman in the aircraft with his hand on the mechanical hook release was knocked on his butt.
The Chinook in dusty conditions builds a bit of Static.....well actually....enough to replicate Lightning almost.
In the infinite wisdom of the US Army, some innovative folks once put a static discharger on the side of the fuselage which was supposed to safely discharge static buildups.
There was a Pilot operated set of switches for operating the system and the default position on the ground was of course the "Off" position.
As Sod's Law prevails in the US Army (oh but doesn't it!).... along trods a young Soldier heading to his Bunker on the Flight Line to pull his Night Sentry Duty and like a Bolt from the Blue.....a huge arc of fire and brimstone flashed from the parked Chinook...to his Steel Helmet and then to ol' Mother Earth.
Wiser heads prevailed and the Static Discharging Systems were all removed from the Fleet.
A Golden Rule while hooking up sling loads.....always touch the lifting tackle to the Hook.....never hold the lifting tackle in one hand and touch the cargo hook with the other hand.....as it will sometimes be a thrill.
In the infinite wisdom of the US Army, some innovative folks once put a static discharger on the side of the fuselage which was supposed to safely discharge static buildups.
There was a Pilot operated set of switches for operating the system and the default position on the ground was of course the "Off" position.
As Sod's Law prevails in the US Army (oh but doesn't it!).... along trods a young Soldier heading to his Bunker on the Flight Line to pull his Night Sentry Duty and like a Bolt from the Blue.....a huge arc of fire and brimstone flashed from the parked Chinook...to his Steel Helmet and then to ol' Mother Earth.
Wiser heads prevailed and the Static Discharging Systems were all removed from the Fleet.
A Golden Rule while hooking up sling loads.....always touch the lifting tackle to the Hook.....never hold the lifting tackle in one hand and touch the cargo hook with the other hand.....as it will sometimes be a thrill.
In Papua New Guinea, late 80's, we had a ground-handler who had been working loads for about a week before he encountered the 'hook of shock'!
He was pretty efficient at hooking-up loads and would waste no time in reaching-out for the hook in order to slide the D-bolt 'shackle' (attached to the load ropes) through the hook's keeper.
As was the norm for the PNG highlands, rain showers abounded, and with less manoeuverability than would be so without a load, one sometimes couldn't avoid penetrating the edges of the lighter showers.
Returning from such a trip I sailed in to uplift a new load when upon arrival I saw the loadsman jump back after grabbing the hook followed by a sharp glance skywards where, even from 100ft, it was clear to see that he was not pleased.
Pressing on, the load was hooked-up and, 20 or so minutes later I was back for more when to my surprise the loadsman had armed himself with a stick and was now stabbing at the hook in a display which reminded me of the staircase sword-fighting scene between Errol Flynn and Basil Rathbone from 'The Adventures of Robin Hood' (1938).
It have to say that I had a wee chuckle at his expense but, thereafter landed and explained to him that the present weather was building-up a charge on the aircraft (not that I think he understood this) and that he should allow me to 'ground' the hook before he grabbed it.
On his day off he turned-up at the exploration camp in his full tribal regalia and of which visit I have a photo somewhere!
He was pretty efficient at hooking-up loads and would waste no time in reaching-out for the hook in order to slide the D-bolt 'shackle' (attached to the load ropes) through the hook's keeper.
As was the norm for the PNG highlands, rain showers abounded, and with less manoeuverability than would be so without a load, one sometimes couldn't avoid penetrating the edges of the lighter showers.
Returning from such a trip I sailed in to uplift a new load when upon arrival I saw the loadsman jump back after grabbing the hook followed by a sharp glance skywards where, even from 100ft, it was clear to see that he was not pleased.
Pressing on, the load was hooked-up and, 20 or so minutes later I was back for more when to my surprise the loadsman had armed himself with a stick and was now stabbing at the hook in a display which reminded me of the staircase sword-fighting scene between Errol Flynn and Basil Rathbone from 'The Adventures of Robin Hood' (1938).
It have to say that I had a wee chuckle at his expense but, thereafter landed and explained to him that the present weather was building-up a charge on the aircraft (not that I think he understood this) and that he should allow me to 'ground' the hook before he grabbed it.
On his day off he turned-up at the exploration camp in his full tribal regalia and of which visit I have a photo somewhere!
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I remember preparing for a RAS evolution from "Lusty" to some support vessels many years ago when I was the deck Supervisor for a MK6 sqdn. I duly briefed the lads on their duties and we got started. It was only when the lad was about to hook the sacru hook with his earthing pole that I noticed he had the earthing plate in his jacket pocket! Luckily I got to him before the helicopter.
Not strictly on topic but another incident back at Culdrose many years ago consisted of spotting an earthing cable from a static fuel dispenser on 706 sqdn line (being used) knotted together. The lad fuelling the aircraft said the tractor had driven over it and had snapped it so he "fixed" it to complete the refuel!!
Jack, you gotta love him.
Cheers
Not strictly on topic but another incident back at Culdrose many years ago consisted of spotting an earthing cable from a static fuel dispenser on 706 sqdn line (being used) knotted together. The lad fuelling the aircraft said the tractor had driven over it and had snapped it so he "fixed" it to complete the refuel!!
Jack, you gotta love him.
Cheers
Sling Loads
Has anyone had experience with static electrical build up on the airframe that presented an issue with the hook up individual, or use grounding prior to hook up?
Just been reading on the subject and see turbine aircraft build up there own static charge, CAP 426,
Never heard of that before, learn some thing new every day. Never engaged in earthing the aircraft prior to hook up myself, nor ever had the hook up chap say he got a jolt.
Just been reading on the subject and see turbine aircraft build up there own static charge, CAP 426,
The results when the exhaust gases contain a preponderance of ions of a particular polarity, leaving the aircraft charged with the opposite polarity. The magnitude of the effect varies widely between different types of helicopter; it is negligible in some but in others can cause voltages of 30 – 50kV to be reached within 1½ - 2 minutes. The process usually imparts a positive charge to the helicopter and is largely independent of weather conditions so that it leads to a persistent static problem which exists even under conditions where all other static charging mechanisms are absent.
Interesting about the engines.
Dust over blades and wings can also generate a huge static charge.
Essentially one needs to match the voltage between two items that are otherwise insulated either by air or the tires. The same voltage matching is seen in high-tension crews working from helicopters or bucket trucks.
I have heard of crews letting the new guy go and grab a sling and get knocked on his butt by the electrical discharge to teach them about the importance of voltage matching before touching.
Dust over blades and wings can also generate a huge static charge.
Essentially one needs to match the voltage between two items that are otherwise insulated either by air or the tires. The same voltage matching is seen in high-tension crews working from helicopters or bucket trucks.
I have heard of crews letting the new guy go and grab a sling and get knocked on his butt by the electrical discharge to teach them about the importance of voltage matching before touching.
Last edited by Senior Pilot; 14th Dec 2023 at 04:47. Reason: Threads merged
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sling loads
Has anyone had experience with static electrical build up on the airframe that presented an issue with the hook up individual, or use grounding prior to hook up
Quite a lot.Used to work in an industry where a lot of work was 4000-5000 feet or sometimes higher.Over snow it was not uncomman to get a belt or two. High altitude
cold air and a lack of water vapour in the air prevented the helicopter from naturally discharging
Quite a lot.Used to work in an industry where a lot of work was 4000-5000 feet or sometimes higher.Over snow it was not uncomman to get a belt or two. High altitude
cold air and a lack of water vapour in the air prevented the helicopter from naturally discharging
Surprisingly, only just come across this thread. One of our tasks at Thorney was to do trials with the Littlehampton lifeboat to allow a team from Farnborough to take measurements of helo static discharges. Chatting with the team afterwards and they mentioned figures in the range of 160,000 -180,000 volts (low current, of course !) Water/deck/land contact, when winching, was made less painful by keeping hands off the cable. On one notable occasion, I forgot to do so at the end of a particularly strenuous wet winching session in Holyhead harbour. I was winched onto the Marine Unit's pinnace and touched down with hand on the wire and mouth open, breathing hard. I have a 'collection' of amalgam molars, upper and lower and the inevitable static discharged across them - the taste, and smell, remained for several hours !
Interestingly we use a Hu 369D for Moorland restoration. Over past 11 years we have moved 75000 dumpy bags anything from single to 6's so one can imagine the number of lift cycles, Had no more than a handful of static belts ! Seems to happen when there is moisture in the air in particular snow. Just come back from 10 days and over 1100 cycles, ground crew who catch the hook didnt have any belts