What happens when an aircraft is struck by lightning?
This is one of those questions that everyone has asked at one point or another. Whether you are a pilot or a passenger, we all have wondered what would happen if the airplane that I’m flying would suddenly be hit by lightning?
In private pilot ground school we learned that friction causes drag. What we may not have been told is that this same friction also creates static electricity. As an airplane flies through the air it continuously creates a static charge, especially on the aircraft control surfaces. This situation is only made worse when flying through any kind of precipitation or even worse, volcanic ash. Static wicks which are attached to the trailing edges of control surfaces are designed to help dissipate this charge to the surrounding air. Static wicks protect not only our flight instruments and radios but also the flight surfaces themselves. Without the static wicks attached, the static charge on the surface would try to “jump” the unconductive control hinges to the rest of the aircraft. This “jump” or arc could cause permanent damage to the surface itself if the static charge had the opportunity to build sufficiently. To further protect against this damaging “jump”, manufacturers also attach conductive bonding strips to keep the static build-up to a minimum.
We also learned in ground school that airplanes are primarily made of aluminum which we know is an excellent conductor. This conductive property of aluminum creates a “Faraday cage” around the airplane protecting its’ contents. I’m not an electrician, but the best definition I can give of a Faraday cage is that it is an electrical enclosure. This enclosure shields the contents inside the cage from the current that might be present on the surface of the Faraday cage. Although there is a lot of static electricity on the outside skin of an aircraft, the aluminum conducts the electricity away from the interior and towards those static wicks that I mentioned before.
Now some aircraft are not manufactured with traditional aluminum but with a high-strength composite material like the Beechcraft Premier or Cessna Columbia. Fortunately, engineers have designed strike protection into the composite material by making one of the layers a graphite cloth and aluminum ply. This ply, which is highly conductive, also serves to create the same “Faraday cage” affect that is found on traditionally manufactured airplanes. Some composite airplanes also have an additional layer of protection against lightning strikes by installing Metal Oxide Varistors (MOV) throughout the circuitry. MOVs are designed for failure. If an MOV senses a sudden surge of current (from say a lightning strike) than it is designed to break and protect the rest of the aircraft’s delicate electronic systems.
So obviously with all these various lightning strike / static electricity protection systems, engineers are designing aircraft with the assumption that aircraft stand a reasonable good chance of being struck by lightning. In fact, it is believed that most commercial aircraft are struck up to twice a year. Most of the time, a lightning strike is a minor event (thanks to those protective systems). The only evidence left behind in most strikes is a small lightning entry and exit point. In the photo below, you can see where lightning made a small entry point on the top part of the aircraft’s radome (nose) and you can see the exit point about 6 inches lower.
Ouch.
Sometimes aircraft damage from a lightning strike is more severe. Lightning has been known to pop circuit breakers (which fails aircraft systems), magnetize control surfaces, punch large holes through aluminum (although this is extremely rare) and flicker or even cause the failure of some glass cockpit displays. This leads us to the next question, has an airplane ever crashed as a direct result of lightning?
I wish I could say no, but accident investigation evidence says otherwise. The Flight Safety Foundation (FSF) through the Aviation Safety Network list several airplane accidents where lightning was a direct contributing factor in the accident. You can see the list for yourself. The most recent listing is a Dornier 228 that on December 04, 2003 took a direct lightning strike that the crew immediately reported. The lightning apparently damaged the rudder and made aircraft control very difficult. Fortunately, there were no fatalities although but the aircraft was totaled and considered a loss. There are older accidents listed as well by the Aviation Safety Network and some of these, although very tragic, have benefited travel safety today in the form of better design and engineering in aircraft systems.
What can I do as a pilot to avoid being hit by lightning?
Avoid thunderstorms! The Aeronautical Information Manual (AIM) states that the “probability of lightning strikes occurring to aircraft is greatest when operating at altitudes where temperatures are between minus 5 degrees Celsius and plus 5 degrees Celsius. Lightning can strike aircraft flying in the clear in the vicinity of a thunderstorm. ” Their advice to avoiding being struck by lightning? Avoid any thunderstorm identified as severe or giving an intense radar echo by at least 20 miles.
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Charlene Gervais on Jul 14, 2009
If avoiding a thunderstorm by 20 miles is good, then 50 to 100 miles of separation is GREAT.
I like to stay far, far away from that stuff…
Paul on Jul 14, 2009
Lightning has been know to move horizontally up to 50 miles from a storm. It has also been known to strike under clear skies. This happens when a thunderstorm is on one side of a mountain and it is clear on the other side. The lightning will literally follow the contour of the ridge up and back down until it finds a target. Scary stuff.
Your right though Charlene, best to keep your distance and stay far, far away.
Patrick Flannigan on Jul 14, 2009
I was expecting you to write something about that experience. No joke, that stuff can strike far from the actual storm. I was blasted right in the clear about a year ago. It really gets your attention!
Paul on Jul 14, 2009
People have asked me, “Was it really bright?” “Did it scare you?” etc. but the honest truth is that I barely noticed the flash at all. My feeling is that I perhaps got an electrical tangent from a cloud-to-cloud lightning strike rather than a full on direct hit.
Patrick, did you find an entry and exit point? Was anything damaged? Did you have to ground the airplane?
Patrick Flannigan on Jul 15, 2009
Oh yeah, I got hit at night and it blinded us! Had a big scorch mark and a crack in the flap fairing, and it blew one static wick off along with the corner of my winglet.
We had to fly it back to Memphis empty on a ferry permit the following morning.
Chris C on Jul 20, 2009
A minor correction on how static wicks and conductive bonding strips work (from a computer engineer): lightning hitting your plane will make your plane have an electrical charge. That charge will want to go somewhere, and will probably leave in the form of another bolt of lightning coming out of another part of the plane. Electricity leaving a charged piece of metal really likes to leave through sharp edges, and likes pointy bits even more. As you have shown in your pictures, the electricity can cause damage as it leaves your plane.
So a static wick is meant to be the pointiest bit poking out of your plane. It is placed on the trailing edge of your wing or tail since that is also pretty pointy, and the wick is hopefully pointier. Since the wick is the pointiest bit around the lightning will “prefer” to jump from the wick, which you don’t care about, instead of the plane, which you do care about.
The bonding straps gives lighning a really easy path for lightning to travel from the plane to the control surface (and then to the static wick). Without the bonding strap the lightning might jump through the air from the wing to the aileron — and when the lightning jumps to and from the air it creates a lot of heat, which tends to burn things (like the metal of your plane…).
Paul on Jul 20, 2009
Chris. Thanks for your comment and addition to this discussion. I do my best to compile information from various sources (printed and online) but having a knowledgeable expert add to the discussion is very helpful, thanks. I really appreciate it.
Lightening strikes revisited — Golf Hotel Whiskey on Jul 22, 2009
[…] case you are wondering what happens if a plane is struck by lightening, Paul of Ask a CFI.com has written a detailed post about lightening and the potential damage it can do to airplanes. As […]
B-Rad on Jul 22, 2009
Great post about lightning and flying. Pilots should also beware of lightning on the ground. As a line guy working in one of the most active lightning areas in the world, Orlando, I too often see pilots exiting their passengers in the midst of very severe thunderstorms on an open ramp(some with umbrellas). We suspend ramp service when lightning is within 5 miles but, pilots will berate us for not helping them. This is even after us informing them about the precaution.
Be safe, be smart,
B-Rad
Noah on Jul 17, 2011
Hello all, indeed this is a great post about Lightning. unfortunatelly lightning is hitting us in uganda badly these days. something i want i ask @ Patrick Flannigan, does a Radar detect lightning too?
Paul Ulrich on Oct 26, 2011
Weather Radar does detect lightning.
asad naq on Apr 21, 2012
Yesterday an airplane flying from Karachi to Islamabad Pakistan strucked by lightning (eye witnesses saw that). The plane belonging to Bhoja Air crashed instantly. The MET department reported intense storm with CB clouds were present near the runway.
MY question : if modern aircrafts have got tendency to absorb electric current then how it is possible that the plane crashed?
Please answer as all us Pakistanies(already shocked by terrorism in our beloved homeland) are shocked with the incident.
asad naqvi on Apr 21, 2012
Yesterday an airplane flying from Karachi to Islamabad Pakistan strucked by lightning (eye witnesses saw that). The plane belonging to Bhoja Air crashed instantly. The MET department reported intense storm with CB clouds were present near the runway.
MY question : if modern aircrafts have got tendency to absorb electric current then how it is possible that the plane crashed?
Please answer as all us Pakistanies(already shocked by terrorism in our beloved homeland) are shocked with the incident.
abhilasha on Dec 14, 2012
i took info from this website for my physics project. this made e think a lot and not just cut,copy,paste. I hope some day I will be able to do something like this.
Bayar on Apr 21, 2014
Back 1995 our local passenger plane was hit by lightning during the flight to Murun from Ulaanbaatar. I could see the kind of bluish lights traveling in between the windows over the passengers, all the suddenly the plane had very strange move as if its fallen down and in moments later 2 of the engines had some kind of start up sounds and plane had corrected its normal trip.
I was traveling with American documentary movie writer and the safety belts were off during that moments, but as the plane survived we noticed that both of us buckled our seat belts.