Plane & Pilot
Tuesday, June 21, 2011

Lightning!


Lightning may not be a major hazard for aircraft, but it’s the most spectacular manifestation of our archenemy the thunderstorm



SEVERE WEATHER. While general aviation aircraft are less likely to attract a lightning strike, thunderstorms are killers, and it's always better to land and wait them out.
Perhaps the most active thunderstorm area of the world is Darwin, Australia. The curious collusion of meteorological conditions necessary to generate lightning seems to be near perfect in and around Darwin. The area is so volatile that international weather researchers make regular treks to Darwin to study the violent conditions that seem almost normal in that part of Australia. A single storm in 2002 produced an amazing 1,634 lightning strikes.

The city perches near the top of Australia, roughly 12 degrees south of the equator on the Timor Sea. A combination of humidity, temperature, ionization and frontal weather presents the area with thunderstorms six months of the year.

Everyone I know who has been through Darwin tells stories about incredible lightning storms, and I've made two trips through Darwin myself under the same conditions. Back in the days when Cessna was cranking out dozens of airplanes a day in the Wichita area, I used to witness violent Kansas storms during domestic ferry flights, but none compared to the sheer violence of Darwin's perpetually wild weather.

I remember standing on the porch outside my hotel room in Darwin one January night at 1 a.m., watching the most amazing light show I had ever seen, multiple slashes of lightning covering the horizon, illuminating muscular cumulonimbus clouds storming across the sky. The display went on until just before sunrise, when the clouds magically dissipated to near-clear conditions.

I was reminded of that time recently by Barry Andrews, a client whose A36TC Bonanza I ferried to Singapore a dozen years ago. During that trip, Barry arrived in Darwin the morning after I flew in from the Solomon Islands, and we departed a day later for the 1,800 nm leg up to Singapore. The forecast had been for reasonable weather most of the way, but by the time we passed Surabaya on the island of Java, we knew we were in for a rough ride.

Fortunately, Barry had radar and a Stormscope installed in his airplane, so we were able to keep tabs on the worst weather as we tracked up the Indonesian chain toward Singapore, lightning flashing in the clouds around us. I don't fly to Indonesia that often, but those who do tell me lightning and thunderstorms are regular occurrences.

Like most pilots smart enough to know better, I don't fly in thunderstorms when I can avoid it. Africa also is infamous for its frequent Cb activity, but we usually have the option of waiting out the weather or diverting if it becomes untenable on the Dark Continent. There have been instances over the ocean (mostly in and around the equatorial ITCZ) when I've been forced to ad-lib for a few hours in ugly atmospherics, simply because there was no other place to go than my destination. In 45 years of flying, I've watched lightning brighten the sky inside my cloud several times, but I've never been hit by it.

In contrast to the tremendous power of lightning (a typical ground strike can carry as much as one billion volts), the consequences of a strike on an aircraft are usually benign, because an aluminum fuselage is an excellent conductor, channeling the energy harmlessly through the aircraft's outer skin. In fact, it's estimated that virtually every commercial airliner is struck at least once a year, and hardly any suffer major consequences to people or systems.



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