Lightning and Planes : Captain Meryl Getline

From a column in USATODAY.com
Captain Meryl Getline answers some faq about lightning striking planes.

Question: Do planes ever get stuck by lightning? If so, how often and what happens to the plane and people on board?

—Erik Herberholz, Westland, Mich.

Answer: The answer may shock you, but the lightning won't. An airplane being struck by lightning is apparently a somewhat common concern judging by the volume of mail I get on the subject. Let me start out by saying if you're going to be involved in a lightning strike, an airplane may be one of the safest places to be.

It has been decades since commercial airlines sustained any real damage from a lightning strike, even though statistically airliners experience an average of one to two strikes per year per plane. You would probably be hard-pressed to find an experienced pilot who hasn't experienced at least one or more strikes somewhere along the way.

Lightning strikes on aircraft occur when negatively charged electrons encounter positive charges from the surface of the plane, and when they do, ZAP!—lightning occurs. Airplanes create charges in both directions and act as a conduit for lightning.

There are stringent FAA requirements for lightning certification. Surge protectors and shielding are installed to protect avionics.

With the help of their dispatch and meteorology departments, airline pilots do their best to give a wide berth to areas where there's intense storm activity. Pilots don't particularly fear what a strike will do to their airplane because usually there are no lasting effects from a lightning strike. Still, the very notion of a lightning strike is intimidating — the noise from the strike can be loud and startling, and static electricity building up on the airplane can cause aural static on our communications radios, making it difficult to hear at times.

My own worst strike was when and where I least expected it: In the early 1990s, just after departure from Oakland, while flying a B-727, my crew and I were shocked (not literally) when we took a hit. There were no storms anywhere nearby—just some rain.

This was at just 7,000 feet on departure. The noise was akin to a cannon being shot off in our cockpit. My copilot was leaning forward, reaching for a knob or something, and was knocked back into her seat. She said later she felt she'd been smacked on the chest.

Our lights blinked off and on again, and I looked back at the flight engineer's panel to see all three of our generators had "tripped" or fallen offline. I asked our flight engineer to check to see if our electrical system was still okay, which it was, so she restored electrical power to its normal configuration.

After a quick radio call to our maintenance facility, with all power restored to normal, it was decided to continue our flight to Denver. Upon arrival I got up on a ladder with a mechanic to see about forty of what looked like cigarette burns on our nose (some of which I had been able to see from the captain's seat in flight). Those superficial pinpricks in the skin are the telltale signs of a lightning strike, not that we could have possibly missed it.

The boom had been so loud that our flight attendants immediately called the cockpit to ask if we were all right, which of course we were. I made an announcement to our passengers just a few minutes later to assure them that it had sounded a lot worse than it was and that we were just fine. This is the typical scenario of a strike: a loud noise, maybe a temporary power failure, then everything comes back. It doesn't always go that way, but I've never had any experiences any worse than this either as a passenger or as a pilot.

So what happens when lightning actually strikes the airplane? It's important to note that lightning has one mission in life and that is to find a path to the ground. It usually strikes an extremity like the nose or wingtip, and from there it passes harmlessly around the outside of the aircraft and exits off the back of the wings with the help of "static wicks."

These look like little spikes sticking out off the back edge of the wing, the tail and wingtips of aircraft, as illustrated in this photo. They're so unobtrusive my guess is most people have never noticed them. Next time you fly, see if you can get a view of the trailing edge of the wings of your own aircraft, or try to get a look at some other aircraft while you're taxiing.

Static wicks are made of metal but housed in fiberglass and are electrically connected to the aircraft's frame. They're designed to allow static electricity to dissipate, and if lightning does strike, these wicks "encourage" the electricity to exit through them.

Static wicks don't prevent lightning strikes but give the electrical charges an easy exit point. There are a minimum number of static wicks required to be on the airplane and if any are missing, they must be replaced before flight.