How Are Airplanes and Ships Protected From Lightning?

Your assumption is wrong. They are hit by lightning. Try googling 'plane hit by lightning'.

Also, google 'faraday cage'.

They are hit. See #1

they aren't?? you kinda have to be grounded to complete a path

I've always thought the Starship was a very cool aircraft. I saw one fly as recently as two years ago. The acoustic signature on the ground is unique.

But it had a major flaw in that the props passed within a foot of the rear fuselage and the interior was VERY noisy.

It flew slow, was heavy, noisy, you can't stand upright as a passenger. But the cockpit was interesting with 19 color CRTs.

I think on the cover of AOPA magazine around 1986 was "It's a bird, It's a plane, It's a Dud" which pretty well killed it's life.

The aircraft had a major problem with the canard, as it had to add the complexity of a sweeping mechanism when the flaps were lowered. And Beechcraft engineering didn't want to work out the reduction of weight and material of the carbon fiber, so it was over weight. As well there was infighting (hear-say on my part) between Dick Rutan and the existing Beech engineers (they didn't like an outsider to teach them). The 3/5 scale model did not have the canard flight issues. Nice idea, should have been fully developed. It did introduce the lightning and HIRF issues, that now are de facto design considerations for all aircraft.

The last I heard, the 2 still flying could not be pried from the owners hands. Any offer of a KingAir trade was not acceptable. Beechcraft had to make 50 of them to get their tax abatement from the city (Wichita) for the assembly buildings for the autoclaves. They make a Premier I that has a "plastic" fusalage with aluminum wings, and is a small biz jet. And now a new owner, I think Cessna purchased them out of bankruptcy. I lost track of the China deal, but that must have been shut down by the state department.

The Italians have a very nice implementation with Piaggio P180 Avanti, conventional materials, very quiet, and takes off like a jet, but is a turbo pusher prop canard airframe.

They spent $50K USD on attenuating "barbells" attached to the interior of every aircraft to quiet the noise. Didn't help that much, I guess. Never flew in one.

We talked to Beech about building an electronic, active noise cancellation system for the cabin when I was working in noise and vibration cancellation. Never came to anything.

Headsets were cheaper.

I don't know what else was wrong with it, but it looked cool and sounds unique.

'...The Boeing 787 is the current only (commercial) 100% composite that I'm aware of that's certified...'

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Just to clarify... is that 100% of the structural components? skin? entire body?

It's not 100% composite.

You are behind the times, look here:-

http://aviation.about.com/od/Glossary/g/Composite-Materials-On-Aircraft.htm

I think we are using the term "composite" contextually incorrectly here.

I think the discussion here is referring to non-metallic "plastic" composites.

If you have a non-silver dime or quarter in your pocket you have composite material. This material is very conductive.

Wood composites are common, too.

100% composite aircraft are very, very rare, and my be limited to personal small "kit" aircraft only.

Southwest Flight 4013 (B737-700) is not such a composite aircraft, but it does have good brakes.

It's actually the thermal air masses....

http://www.sail-world.com/

http://coconuttelegraph.net/forums/showthread.php?8305-Lightning-Strike-Burns-Boat-in-Marsh-Harbour

Aircraft do receive lighting strikes. They almost never see damages because of these strikes. Now there has been some radios and other nav equipment that have gone south due to these strikes though.

As far as the air frames being made of composite materials, there are a lot of composite airframes flying every day and there has not been any issues to date recorded in the NTSB Files. This out of several million's of air hours.

The St-Elmo's fire that we see on ships and aircraft has no ill effect on any thing on these craft either. If you look on the trailing edges on almost any air craft flying in weather, you will see about 6" long wicks that are made to disperse this energy. Ship mast will also do the same thing. Flying for many hours over the years I have seen the props just glowing with fire. Quite interesting to see.

Several have provided good responses to the airplane portion of your question. As for ships, lightning protection is similar to tall structures on land.

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Lighting protection provides a preferred path for conducting a lighting strike between one or more points at the top of the ship and a conductive surface in contact with the water.

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There is a prevalent but disputed theory that the frequency and strength of lightning strikes can be be reduced through charge dissipation via multiple grounded sharp points positioned his on a structure. The idea being that if sufficient charge is bled from these points, that a strike might be avoided, and at a minimum the charge transfer during any strike would be reduced.

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Given the infrequency with which sailboats with grounded metal masts are struck by lightening compared to the ideal target they would otherwise seem to present, I tend to think charge dissipation can be significant at sea. It should be noted that the preceding comment has not been made without the significant assistance of anecdotal evidence, confirmation bias, and remaining relatively untainted by significant amounts off good data on the subject.

As a former small boat sailor, I would say that mast grounding was/is not commonly done and it's almost impossible to avoid contact with and stay away from the mast/boom/shrouds, etc anyway. The best tactic is avoidance. I was once advised to, if caught in a thunderstorm, capsize the boat and hang on in the water until the storm passed.

Every sailboat I've had with a metal mast, had the mast well grounded through-hull (or next to the swingkeel/center board penetration) to a conducting surface below the water line.

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It is advisable to avoid being in contact with metallic (also carbon or otherwise highly conductive) stays, shrouds, mast, boom, etc when chances of lightning are high. You really shouldn't be leaning on the stays and shrouds anyway and avoiding the boom is usually not too difficult after the first time someone gets clocked coming about.

I'm talking small - Sunfish and 13' Ghost. Anything bigger I sailed was OPB's - although I don't remember my friends's J-24 having a grounding plate (of course, capsizing it wasn't an option either).

For something like a Sunfish, there isn't much excuse (or likelihood) for putting yourself in a situation where you can't extricate yourself from the problem by beaching/docking and waiting out the lightning on land.

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Aren't most Sunfish equipped with fiberglass masts anyway? I know I've seen some with aluminum masts, but it seems like most are fiberglass.

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I guess I didn't understand that when you wrote '....mast grounding was/is not commonly done....' you were referring only to boats as small as a Sunfish (which shouldn't be caught out in lightning anyway). In fact it still doesn't sit completely straight with me...if you are referring only to boats as small as a Sunfish, where do the difficult to avoid 'shrouds' come in to play? I'm pretty sure Sunfish do not have shrouds.

The new ones (are they still making Sunfish?) may be, but mine was '80s vintage, and had aluminum mast and boom. It didn't have shrouds, but the Ghost did. On either one, it's hard to put much distance from anything (plus the Ben Franklin effect of the wet sheets). Fortunately, I never had to seriously consider the advice.

The Ghost looks like it must have been a fun little boat. Was it pretty quick to plane?

Here is a link to some recommendations of the ABYC on protecting a sailboat from lightning by grounding the mast.

I've noticed that misspelling a lot! ...and not always from those for whom English is a second language.

Also if you do not want to experience lightening, use birth control. Most of us men will never personally experience lightening.

I have always questioned why commercial aircraft can take a full on lighting strike without falling out of the sky yet they are worried that someones cell phone signal is going to take them down?

I saw Piaggio Avanti at a local airport. When I got home I started searching business jets on the internet. Couldn't find a thing. Then I searched for business turboprops and it was the first one to turn up. I wonder why it couldn't be scaled up for commercial use. It is 30-40% more efficient than a conventional airframe.

Consider a bird sitting on a 220KV transmission line. We all knows that nothing is happened to the bird, it simply fly away from the line without having any physical problem; this is because of the step voltage across its legs,when it is on the line conductor, is very less compared to the transmission voltage.

Lightning only strikes the object which has contact with mass earth. The aeroplane floats in the air. Let us think about a plane which happens to be in the path of a lightning strike. pls note that the lightning path is already established and the path is already ionised and the current is passing through the path. If the plane is exactly in the path of the lightning, the worst condition is that the body of the plane allows its way to pass the strike current through it. Nothing happens to the aeroplane; the step voltage acroos the plane should be very very less than the lightning Volt.

As an OT, What happens to car passing on driveway, during a thunder storm?; appreceate members input.

Lightning does not flow over the surface, it takes the lowest resistance path.

Your example of comparing power transmission to lightning is incorrect. The reason for the high voltage is to keep the current small, so the IR drop of these wires is kept minimal. So if you want to think of what would happen if the bird is sitting on this wire, and 200Kamps is flowing (not real world), and lets say it's feet are 5cm spaced on this wire, and this wire has 1 milliohm per cm resistance, the bird will get a differential voltage of 1000V between it's feet, and probably not survive.

You need to think of what the lightning current flow does in an aircraft. It does not just bring the aircraft to the lightning static potential. Current is flowing though the airframe. In an airframe, the IR drop from the current is calculatable, and it's not zero. There are 2 effects of lightning. One being the IR drop caused by the current flow, and another by the current flow through the lower resistance airframe structure, but parallel to aircraft wiring. This induces a voltage in the wiring via a single turn air-core transformer process.

So take the case of an aircraft that has 5 milliohms of resistance from the tail to the nose, and then use the 200000 amp nominal strike current. This will induce 1000 volts IR drop across the length of the aircraft. If you have an avionics box in the nose electronics bay, and one in the tail electronic bay, the wiring between them will have 1000 volts induced. This is call pin injection. The secondary effects of the current flowing through the airframe also creates induced voltages to the wiring, and the protection used is the same as for EMP.

Understand that small resistances with large currents will create an IR drop.This problem becomes real with composite airframes and components. The airframe designers have to ensure there is enough lightning current carrying metal in the airframe, and the avionics that are installed have to be able to survive the design calculated injection levels.

There are lightning direct effects issues, attaching to antennas, and this typically is very difficult to survive.

And the same issue of a single point upset event that disrupts or damages multiple systems at the same time, is a real safety concern. New aircraft designs are using fly by wire control systems. Think of seeing a lightning bolt 2 meters in front of you, the damn airplane better keep flying during the time the pilot is trying to recover eye sight, and bowel movement.

Agreed; and appreciate your vast knowledge regarding the subject.

Just for knowledge -has any lightning strike of Antenna been reported so far?

I never worked on VHF/HF/DME/VOR/GPS etc. radios, but from field service, they are a common target that results in damage to the radio boxes. These are low impedance connections from the exterior of the aircraft, and "let" the lightning into the connected boxes. Lightning strikes are not remote events. Single engine aircraft generally never see them, as they are not operated by their pilots in bad weather conditions. Air transport operations operate under scheduled conditions, the pilot does not try to fly into thunderstorms, but close by them, and they become a target for lightning, as they help induce the ion trail of lightning. The theory they have for the jagged path of lighting was that the discharge was using the ion trails of cosmic ions traveling in the atmosphere.

My personal experience with lightning was on one customers aircraft, who had a Falcon 50 biz jet. He did not like the look of the lightning diverter strips on the radome, and had them removed. Which technically made the aircraft non flight worthy. Our field service was changing damaged avionics continuously. This owner pilot contacted the president (he was a golfing buddy) and complained about the reliability of our products. So we looked at the history of the problem along with the Dassault airframe manufacture, and figured out what had been done by looking at aircraft maintenance log books. They replaced his radome, and us the avionics. I doubt if he had to pay for his stupidity. But hope he learned a lesson what the diverter strips are for. The damage was probably from several lightning strikes, but failure of equipment was not instant from each event.