And dimmed the lights in my apartment, and drowned out my radio with static.
Helicopters fly over where I live all the time. ( I live close to Falcon Field, a municipal airport in Peachtree City “the Bubble” in Georgia).
But this was the first one to cause that type of disruption.
I’m just curious.
I know we have helicopter experts here. (JohhnyLA? Yeah, I’ve been lurking awhile)
How do helicopters deal with static electricity generated by ther rotors? Fixed-wing aircraft have “static wicks” on the wing trailing edges. How do they discharge it?
Was this 'copter somehow malfunctioning in this regard/
The static electricity of a heli discharges when it lands. I’ve heard stories, of military hazing of the new guy when they’re traing to load on to a hovering helicopter. In this situation, the heli hovers and drops a hook. The first thing to do is ground the hook, then you attach the load to it and the heli flys off. If you fail to ground the hook first, I’ve heard the static discharge can knock you off your feet. Sometimes they “forget” to tell the newbie this the first time.
I don’t know if that’s what caused the disturbance, but the static electricity is there.
The rotor disk of a helicopter is a great static building device. The rotor disk acts like a big capacitor until it can sluff off the electrical charge. On wheeled helicopters like the CH-47 there are “whiskers” on the alighting gear to discharge the rotor system when the wheels come in close proximity to the ground.
If you’ve ever seen a helicopter hovering near the ground at night, the water spray, sand, or dry grass swirling in the rotorwash will ionize and spark creating a faint glowing sparkling haze around the rotors. The size of this will vary depending on the humidity, air temperature, and amount of debris being kicked up (NVG’s give a great view of this). It will give you a good visual understanding of what’s happening, because when the helicopter touches the ground or is discharged by personel performing hook operations… poof! the halo of light and sparks around the rotor system will just vanish.
The bigger the system the bigger the charge. It’s not that funny when someone “forgets” to use the static discharge pole with really large helicopters like the 47. I’ve been at the controls during night slingloads when I’d see a huge flash from under the helicopter. I’m talking about a flash that would rival car headlights at high beam for a fraction of a second. And the next day you’d hear about someone getting knocked unconscious. Then it’s time to fill out paperwork… great.
But why is it so important for large fixed-wing aircraft to discharge their static electrical charges while in flight, but helicopters don’t discharge until they land?
When airliners land, no one connects any mechanical means for discharging static electricity.
The major components of large aircraft are bonded together by means of <ahem> “bonding wires” to direct the path of static charges to the “wicks”, where they are bled off in flight.
Why do helicopters carry their static charge until landing?
Couldn’t that be dangerous?
What if their was an arc to a component that wasn’t properly bonded?
Since helos are capable of generating a high potential discharge on landing, what prevents that potential from moving from one component to another inflight, and causing damage?
Ok I’m guessing on this part. I think the reason that helicopter avionics don’t arc in flight is because it’s all one charged unit. Imagine if you were standing on a huge positive terminal of a battery. As long as you don’t touch a ground terminal you won’t arc to yourself.
The charge doesn’t slosh around like a glass of water, so the electronics (if they are wired properly) should only ground to predetermined points of the helicopter.
They were just on their way to Schlotsky’s for a nice hot corned beef on seeded rye with Goulden’s Spicy Brown mustard and a crisp pickle. Pay 'em no mind.
If the static build-up is that significant, what happens to portable electronic devices worn or carried inside said helicopter? I hate the things but have shot out of a few in my career. Nobody said boo about the risk to my pricey broadcast video camera from the static discharge. :dubious:
I flew in a lot of choppers in VN, Navy, Marines, Army and ARVN, but I never gave this much thought, even though I often had to make a rapid exit/entry. I do recall hearing that the static charge could be dissapated by keying up an onboard radio. Any truth to that?
There was a static discharge mishap in the CG a few years back. The H-60 Jayhawk was conducting hoist training with a boat. The helo lowered a polypropylene trail line which is connected to the hoist basket. Boat crews normally don’t ground the trail line as, theoretically, it should not conduct electricity. They will, however, ground the basket with a grounding wand once it’s in reach. The boat crewman reached out and grabbed the poly trail line which was wet with salt water and got zapped.
According to the report, the crewman fell to the deck and was unable to move or speak for about 90 seconds. As you could guess, a lengthy investigation followed to determine the cause as the air crews had never heard of this happening before.
Oh hell yes they do. . . especially when refueling! I can’t cite it, but I would think that engineers would have included a grounding strap on the landing gear similar to what DustyButt suggests. I know quite a few maintainers though, so I’ll ask at work.
On the other hand, a fixed-wing A/C has two surfaces that move through the air. A rotary-wing has two or more, that have a helluva lot more airflow over them than the fixed-wings (rotating wings vs. stationary ones). Anyway, by the lift mechanisms of 'em, the helicopters would generate a lot more static than the airliners. . .
Static is discharged from fixed wing aircraft while airborne from discharge wicks normally attached to the trailing edges of the flying surfaces. I’ve never seen any kind of grounding system other than that used for fuelling. I’ve never closely inspected a large jet though. I also havn’t had a static shock while getting out of an aeroplane the way I have with a car. I’m pretty sure the discharge wicks are effective and so no other system is necessary.
I’m not an aircraft mechanic or anything similar to it, but I had a project involving the installation of jet bridges at a new airport terminal. At each jet bridge there was a grounding device - a hook attached to a large copper cable which was bonded to ground. IIRC, it was labeled “Static Discharge Device” or somesuch. I assume it is for discharging the plane’s static charge prior to attaching services to the plane. I accept the possibility that I may be wrong and look forward to enlightenment.
Its a story/urban legend I’ve heard in Northern Ireland a lot (along side army helicopters frightening lots of sheep and cows to death)
My Grandparents’ house is on the highest level of their town, just about overlooking the police station below. Quite a few years ago, just as a helicopter flew low over their house, the television (allegedly) fused in some manner and they blamed the helicopter for it. I’m not sure if they were compensated or if it was proven in any way.
Oh yes they do! I used to work at a major manufacturer of executive jets and they were forever attaching grounding lines whe they were working on them.
Don’t believe anything they are saying! It’s all part of the government conspiracy using the black helicopters! The mind control rays that keep us from overthrowing the government were miscalibrated and caused the electrical problems. Get yourself a good tinfoil hat and you’ll be safe.
In the film version of Tom Clancy’s Hunt for Red October this happens when they’re trying to lower Baldwin onto the USS Dallas (he swings into the XO before he can hook him with the pole and gets knocked out by a big zap of static). Even though Scott Glen’s character mentions this could happen beforehand, most people don’t really notice it…
