HOW IS A PLANE PROTECTED FROM LIGHTNING STRIKES

Discussion in 'Aviation' started by Airborne, Nov 8, 2007.

  1. Airborne

    Airborne Banned

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    Looking at the two photos makes one wonder how the aircraft could possibly survive such a hit. And yet they do. Virtually every day.

    The lightning and aircraft story.

    Shielding and surge suppressors

    Since the outer skin of most airplanes is primarily aluminum, which is a very good conductor of electricity; the secret to safe lightning hits is to allow the current to flow through the skin from the point of impact to some other point without interruption or diversion to the interior of the aircraft.
    Estimates show that each commercial airliner averages one lighting hit per year but the last crash that was attributed to lightning was in 1967 when the fuel tank exploded, causing the plane to crash. Generally, the first contact with lightning is at an extremity...the nose or a wingtip. As the plane continues to fly through the areas of opposite charges, the lightning transits through the aircraft skin and exits through another extremity point, frequently the tail

    Another related problem with lightning is the effect it can have on computers and flight instruments. Shielding and surge suppressors insure that electrical transients do not threaten the on board avionics and the miles of electrical wiring found in modern aircraft. All components that are vital to the safe operation of commercial aircraft must be certified to meet the stringent regulations of the FAA for planes flying into the United States.

    The Static Wick


    Most aircraft do not fly into lightning storms, or fly through storms or areas where lightning is likely to be present. What we see as lightning is really a massive flood of electrons seeking equilibrium, either from cloud-cloud or from cloud-ground. In both cases, huge amounts of electric charge build up at the edges of the cloud. The electricity finds it's way from one place to the other via what's called a "step leader".

    The sheer power of the cloud will start to attract electrons from the ground. These electrons will gather on anything that gathers charge (like a fence) or sticks up in the air (like a person), or that does both (like a telephone pole). That electric charge will start to work it's way through the air, ionizing it, until the leader working it's way down, and the leader trying to get up finally meet. When they do - there's lightning. An aircraft flying between the highly charged portions of a cloud will act as a conduit for step leaders, being able to produce one in each direction. If either of them meets a leader coming the other way... ZAP.

    The way an aircraft tries to dissipate these step leaders is through the use of something called a "static wick". A static wick is a piece of metal connected electrically to the frame of the aircraft, with one or two spikes or needles on the end. It is housed in a fiberglass rod to insulate it from the airplane. Because the spikes concentrate the electric charge around them, and they are connected to the airframe, they allow the airplane to dissipate any static electricity it may build up out into the air. Also - if lightning DOES strike the plane, the chances are that the electricity will go through the dissipator and not through the airplane.

    Also check out these losses due to lightning.

    Aviation Losses from Lightning Strikes - National Lightning Safety Institute
     

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  2. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    In some aircraft many of the moving components are also bonded to a common ground. East block aircraft are heavily bonded through out.

    BTW I've been through 3 lightning strikes - all very interesting....
     
  3. Aussie1001

    Aussie1001 Member

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    why would a plane suffer any damage if it is not "earthed" to the ground.....
    Please explain..
    thanks.
     
  4. Airborne

    Airborne Banned

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    Please read my post again fully Aussie mate,
    All latent damage is listed there. Avionics, fuel tanks etc.
     
  5. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    It can cause damage to electrical componants and radios and burn damage. We had a Blackhawk get hit by lightning back in 2006. The strike hit the Yellow blade and went out of the Black Blade (my color memory might be off) leaving large burnt areas to the tip caps along with holes in the tip caps. The Bifilars were also burnt and blackened. The aircraft also lost all its cockpit instuments and its radios went out.

    The crew successfully was able to make a blind landing basically in 0/0 Vis safely to the ground.

    As Joe said most aircraft (including the Blackawk that this accident happened to) are bonded and also have static discharge tubes and wicks that prevent serious damage.

    My aircraft itself was hit by lightning but it caused no serious damage. We continued the flight to the nearest airfield. The aircraft had some minor work done to it but it was an electrical nightmare after that. Even 2 years later when we were in Iraq it had electrical gremlins.
     
  6. plan_D

    plan_D Active Member

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    That one in 2006 being the one just before I got to Germany, I assume?
     
  7. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    Yes the one that I described up there is the one that happened right before you came to visit.
     
  8. DOUGRD

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    Whenever an airliner has a lightning strike it's pulled off the line until it goes through a lightning inspection. Every inch of the skin is looked at and all control surface attachments and pivot bearings are checked for pitting and welds. I haven't seen much damage in the way of fouled up avionics or electrical problems. Most strike damage shows up as small arc marks just like when you touch a live wire to a piece of metal. If it's small enough you can blend it out but if it's larger you might have to drill the spot and install a rivet or do a lap patch it there are several in one small area. the whole deal is a pain in the butt BUT not as bad as hail damage.
     
  9. Soundbreaker Welch?

    Soundbreaker Welch? Active Member

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    Does it say every single large passenger plane gets hit by lightning every single year?

    Wow.

    I wouldn't have suspected that. Wonder if the passengers even realize it?

    And Joe, was the flash bright enough to have blinded your eyes for a while?
     
  10. davparlr

    davparlr Well-Known Member

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    Composite aircraft such as the B-2 and new airliners offer a more challenging test to engineers in dealing with lightning strikes. Most of the B-2 avionics are impervious to lightning strikes due to its inherent hardness design. Physical damage to the airframe, however is a different issue.
     
  11. FLYBOYJ

    FLYBOYJ "THE GREAT GAZOO"
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    The first time I was stuck by lightning I was flying jump seat in a DC-9 that just came out of a C check. We were shooting an ILS and it was right after a front with thunderstorms cleared the area. There were still towering cumulus in the area but not in our flight path. We were struck as we climbing out of the missed approach. There was a light about as bright as a flash bulb, a "bang," and then a screeching sound you would hear like running your nails down a blackboard. When we landed we found a quarter size strike right under the co-pilots window that burnt the fresh paint. From that point there was a fine "scratch," almost as if someone took an exacto knife down the whole length of the aircraft. This scratch dissipated at the tail cone which is fiberglass and had static protectors embedded into it structure.
     
  12. davparlr

    davparlr Well-Known Member

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    I never had a lightning strike while flying but I did run into some small hail on an approach to McGuire AFB. That will get your attention. Sounded like machine gun bullets hitting the plane. No damage though, and those TF-33s were bullet, well, hail proof. I also saw an amazing display of St. Elmo's fire while clipping the tops of thunderstorms over Thailand. Looked like fingers of fire all around the windshield. Lots of squeal in the radio.
     
  13. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    I too never had a lightning strike. My aircraft was hit by lightning bur fortunatly I was not flying it that day.

    I did run into hail one time and took some damage from that. When we got hit buy hail we were flying through the Alps in Austria on our way to Kosovo. Turbulance was very heavy (obviously not heavy eneogh to keep us from flying though). Funny thing was we had a problem with our right Aux Tank because it would not seat right. Problem was not found until in flight. We made a stop at an airfield in Austria to try and fix the problem but could not. Decided to continue the flight but make an extra fuel stop. Anyhow the turbulance seated the Tank correctly for us and fuel started flowing properly and were were able to continue the flight as normal.

    :lol:
     
  14. DOUGRD

    DOUGRD Member

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    You guys were lucky!!!! While I was working for Northwest one of the 747-200's took off from Detroit and ATC directed it right through a hail storm. Amazingly the crew contacted ATC and told them what they saw on their weather radar but ATC told them to keep on course. They did and the aircraft got pummeled! The nose cone was totally destroyed, all 4 engine intakes, and all wing, horiz. stab. and vert. stab. leading edges had to be replaced. The pilots and copilots windshields were trashed too. The company decided to have the Boeing AOG team do the repairs. AOG stands for Aircraft On Ground. The Boeing AOG team is like the best of the best. These guys are the "experten" in all aspects of aircraft repair. They are amazing to watch.
     
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