Lightning Safety Stumper: Newsletter Challenge (August 2018)

I would say you are safer in an airplane, unless it is an antique made from wood and fabric. Almost all airplanes are made of a metal skin that would conduct current around the occupants. The voltage gradient inside the airplane where the occupants are is close to zero since the metal surface of the plane acts as a Faraday cage.

"The turbulent storm is more likely to cause a plane to crash than a car."

I'm not sure of that. SE mentioned falling limbs. Flying airplanes don't hydroplane. If a driver gets blinded by a lightning strike or by a sudden downpour, there is a pretty high chance of losing control, whereas a plane can just keep going until the vision clarifies.

The question is far too vague to allow for a definitive answer. It says "during a thunderstorm"; it says nothing about how close to the center of the storm either vehicle is traveling. At any given instant, there are dozens of thunderstorms occurring somewhere, so every time you drive or fly, it is "during a thunderstorm".

True, it could be a trick question, but the title does say "Lightning Safety"...

Planes are tested for lightning strikes with up to 200,000 amps. Typical lightning is only a fraction of that.

"An average bolt of negative lightning carries an electriccurrent of 30,000 amperes (30 kA), and transfers 15 coulombs of electric charge and 500 megajoules of energy. Large bolts of negative lightning can carry up to 120 kA and 350 coulombs."

https://en.wikipedia.org/wiki/Lightning

The statistics are that the average airliner gets struck almost once a year.

GA!

Thanks for the Panthera link. It appears that they were testing composite aircraft skin materials., with the "protected" ones presumably including some form of conductive layer near or on the outside surface.

One possible caveat: they appeared to be testing sparks traveling from an electrode above the skin to one below the skin, corresponding to a spark passing from outside the aircraft to some conductive part on the inside of the aircraft. If the skin is acting as a Faraday shield to protect the occupants, then the spark would have to enter on the outside of the skin at one point, travel a relatively large distance along the skin and through the protective layer, and exit at a different point, also on the outside of the skin.

Testing that properly would require a totally different setup than the one I saw in the video, and would require a much larger sample of the skin.

Dammit, Rixter (), I was reading this yesterday and pondered composites. Seems they are interwoven with conductors. Thus far, thus good, but how does that play out with stealth aircraft. I went way offtrack reading on that, and it seems that it is not too big a deal. For sure, stealth aircraft have been grounded but by and large it's because 'no-fly' happens during storms. There have been mishaps, but nothing that would not have happened to other jets. I could not find out how embeded conductors are compatible with stealth, just as well since I have no desire to stifle you .

I'm voting to be in the air, but the question is ambiguous. A noble tradition on CR4.

There's a lot more to stealth technology than composite materials.

https://en.wikipedia.org/wiki/Stealth_aircraft

My guess is that if embedded conductors in composites are detrimental to stealthiness, a compromise might be made. Being detected by radar might be a greater danger to a stealth aircraft than being struck by lightning.

I suspect you have read up on this as I did. The situation comes down to risk assessment, though evaluating $billions of aircraft cost and pilot training must be hard to say the least. Something like 300k for the pilot helmet alone.

I agree that this is likely a trick question. One of the tricks can be how one defines a "safer" scenario. Is a "safer" scenario one that an accident is less likely to happen at all or that death is an unlikely outcome of an accident? Another trick would be how likely lightning itself will create an accident or harm to an individual in each scenario. Then there are all of the other more subtle tricks.

I say both scenarios are just as safe from lightning for the automobile and the airplane used their mobility to avoid the thunderstorm.

I am sure an aeroplane is much safer than a car.

The voltages encountered in a lightning can easily create a spark between the earth and the car, resulting in electrocution of all the inmates in a car. In a aeroplane, even if all the passengers attain a high voltage, there can be no earthing, and unless the lightning is a bolt, where the aeroplane forms a part of the circuit, closing it with the earth, little damage could be expected.

A spark caused by lightning between Earth and a car does NOT usually result in electrocution of the occupants! Look up "Faraday Cage".

Earthing has nothing to do with it! What matters is the potential difference between two different points on the human body, and the resulting current flow through that human body. Both a metal car and a metal airplane body direct the current around the occupants. As someone already pointed out, the window openings tend to be larger in cars, which would reduce the level of protection somewhat.

Now that they are building a lot of airplane bodies from composites, I'm not at all sure what will happen when one of them gets struck by a lightning bolt, but I'm betting they are significantly less safe.

Birds perching on high tension wires are not electrocuted. On High tension electric wires there are a set of people called 'HOT' workers that move on a contraption that does not get 'earthed' and they are safe. The same thing is likely to happen to passengers in aeroplanes.

I heard of bird strikes that ground an aircraft, but not lightning strikes. May be, I am ignorant about such strikes.

I would say an airplane has a greater risk of being struck by lightning, but both are relatively safe...and everybody knows air travel is statistically safer than riding in an automobile, so I would have to say being in a flying airplane is safer....most airplanes will avoid lightning storms by flying over them....and it doesn't say "in" a lightning storm, it says "during"....

While it is true that the statistic says that driving in a car is less safe it is also true that this statistic has not been made for the condition: In a lighting storm!

This will mean that Brave Sir Robin could be correct.

In my opinion I would feel safer in the car than in a plane.

Let us not discount falling tree limbs, a hazard confined to ground dwellers...

Isn't that what conked out Dorothy? There's no place like home, there's no . . .

Would a flying house be considered an airplane or vehicle? In any case I think it happened on the ground....

I think the tree limb hit the window frame knocking it loose and into Dorothy's head...

Nice find! My recollection was only slightly flawed this time. It's usually much worse.

I can attest to the danger of Sudden Branch Drop <https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=14&cad=rja&uact=8&ved=2ahUKEwjXv8ejlO3cAhVB4VQKHaKLCj0QFjANegQIThAC&url=http%3A%2F%2Fjoa.isa-arbor.com%2Frequest.asp%3FJournalID%3D1%26ArticleID%3D1877%26Type%3D2&usg=AOvVaw1v4XvgMCO8F5BtcV3KGe3j> I forgot my tape measure and went to the garage to retrieve it. While I was away a 14" diameter limb fell from a 22" DBH Big Leaf Maple. There was a 5 - 10 mph wind at the time. I've not been that close to disaster while either piloting or driving.

Interesting: in the attached report the author says "Limb failure on hot afternoons is an anomaly", but, I'm not clear whether he means that.

1.) this anomaly normally happens on hot afternoons.

OR

2.) It can happen anytime, but is particularly surprising on hot afternoons.

I would have thought that recording the time of day for these "calm summer branch drops" would help considerably in determining the causes.

What time was your event?

I've had several black oaks (Quercus Kellogii, I believe) fall near my house over the nearly 50 years I've lived here. These were entire trunks, not branches. In all but one case, they were apparently where several trees came up very close to each other, so at maturity they look like a tree with multiple trunks, Each tree seems to prevent the others from forming roots on its side of the group, so the root system is weak on the side toward the other members of the group, and they eventually fall outward from the group.

The last one fell about a month ago, during a calm early afternoon. It was fully leafed out, and around 2 feet in diameter at the base, although once it fell, it was obvious that it was only supported by around a 6 or 8 inch diameter of good wood. It failed due to root rot. I apparently heard an echo of the actual sound, because I looked in the wrong direction, and didn't see it. My wife happened to be outside at the time, and was in a better position to hear the direct sound, so I found the tree fairly easily, although it is not visible from our house.

I only actually heard the fall of one other. It too fell in calm weather, but was 20 or so years ago, and I don't recall the time of day

Early on a late July afternoon in well above normal temperatures for Western Washington--as has been the case since mid-July except for three short interludes of below normal temperatures.<https://www.wrh.noaa.gov/climate/yeardisp.php?wfo=sew&stn=KOLM&span=Water+Year&submit=Water+Year+Charts>

Thanks both.

On that small statistical sample it looks like:-

1.) This anomaly normally happens on hot afternoons.

There have been instances where the lightning strike on modern aircraft has significantly disrupted some of the electronic navigation and other systems which are installed in the aircraft skin and have wiring running just below the skin simply because of induced voltages as the lightning strike current flows through the aircraft skin.

I would tend to think that this is likely to become more of an issue with composite materials used in the fuselage and wings.

There was an instance of a Helicopter in the UK ferrying oil workers to a rig where a strike blew a hole in a rotor blade .... I do not remember the outcome ......but the blade did have metallization to protect it against lightning strike!!!

By 'safer' do you mean from electrocution?.

I would say they are both Faraday cages - but choose car - mainly because I would be worried about the 'electronics' being zapped and disabled by lightning - and the consequence of crashing.

At least there is a chance of stopping the car safely.

But I guess there are statistics about this - if one knew where to look.

One of the Apollo rockets was struck by lightning shortly after liftoff (Apollo 12, iirc), but continued on and successfully landed on the Moon and returned.

Airplanes are struck fairly often, but the people and equipment inside are protected by the faraday cage effect of the airplane's skin. Lighting is seeking a 'ground', and since the airplanes aren't connected to ground the lighting just keeps going.

The same faraday cage effect protects the people and equipment in a car, but the lighting will discharge through the tires as it reaches 'ground' and the heat generated can cause collateral damage to the car.

I would say that you are safer in the airplane, but not for any of the reasons previously mentioned.

A friend of mine was recently driving through a lightening storm and we were talking about how safe it was. He was going west on interstate 40 between Texas and New Mexico. The conditions started out as lightening, then after about an hour it became a thunderstorm. My understanding, flawed as it may be is that a lightening storm is where you see and are surrounded by so much lightening that it could be " seen " as rain. And a thunderstorm storm could have more or less of some components : thunder, no lightening or rain, thunder and lightening and no rain, or all three at once, in varying degrees of intensity. Examine the car and the plane : ( the question says, in a car and a flying airplane, versus a moving car and a non flying airplane ) a car is surrounded by windows and in a plane there are large windows in front. The car driver momentarily blinded by flashes, could inadvertently hit a stationary or another moving object, whereas the pilot of a plane, also blinded, would be less likely to hit an object.

Technicalities aside, more people die in cars when a lightning storm is going on. It's a plain statistical fact.

Answer is now posted.

And if the Saturn V with all of its rocket fuel was ever struck by lightning things would blow up, or would it just trip something?

Just watched a documentary about Apollo 12. They talked about getting hit by lightning. The next thing they talked about was the recitation to ground control of all the systems that were tripped. That included something like power bus A, power bus B. You'd think that an Apollo space capsule, sealed up pretty good against the vacuum of space, would be an excellent Faraday cage. So what tripped the power?

The facts are that cars, airplanes, and space capsules are only approximate (kind of poor) Faraday cages. They still have a lot of openings, like windows, and conducting penetrations, like exterior light wiring. They still allow things like cell phones and garage remotes operate while they are inside the car. Seems like a Faraday cage would be radio silent inside.

The amount and kind of energy that gets inside a Faraday cage depends on the size and proximity of the openings. In a car there are large openings (windows), right next to you. In an airplane the windows are a lot smaller and there may be someone else sitting in the window seat.

This leads me to believe that being in an airplane is somewhat safer than being in a car. As for me, I'd rather be at home, reading a book, when the other vehicle gets hit by lightning.

Not a very convincing answer!

The last sentence: "If the current reaches the fuel tanks then they may explode." is actually more pertinent to cars than to jet airplanes, as Gasoline is considerably more volatile that Jet Fuel.

The arguments in my post #9 remain valid, though hardly conclusive.

Surely there must be some statistics to support or refute the "answer"'s hypothesis. (and without those statistics, I consider the "answer" only a hypothesis) ...but then which statistics? I'd suggest "Deaths per million passenger miles due to lightning strikes", or something similar.

EDIT: I just did a search, and found "http://lightningsafety.com/nlsi_lls/avaition_losses.html"

They list a total of 9 aviation crashes attributed to lightning strikes, since 1959!

Here is an answer that itself needs an explanation.

A. The current remains " in " the exterior of the car. Exactly how is the exterior of a car on the " in " ? Wouldn't the exterior be on the " out " ?

B. If your car has a plastic body. Please provide an example of a car with at 100% plastic body.

C. If an airplane is made of non conducting material. How does current flow through non conducting material ? Is there a reason why copper wire is covered with a non conducting material such as plastic, vinyl or rubber other than to prevent current from crossing a threshold ?