Aviation Safety Letter 3/2003
Take Five Tear-Out: Thunderbolts and Thunderstorms
Seen as the most spectacular part of a thunderstorm, thunderbolts do not pose a serious risk to aeronautics: "in a metal airplane, the crew is sheltered from the direct effects of an electrical discharge:"
- A flash of lightning can temporarily blind the pilot.
- The radios and electronic equipment can be damaged, and the thunderbolt's "tracks" can be left on the aircraft's fuselage.
- Serious accidents caused by lightning are extremely rare.
- However, lightning is a good indication of the force of the thunderstorm.
- The more frequent the flashes of lightning, the more violent the thunderstorm may be, and therefore should be avoided.
- Conversely, when the frequency of the flashes of lightning decreases, the thunderstorm is starting to dissipate.
There are certain requirements for a violent thunderstorm to occur:
- unstable air from the surface to high altitude;
- high relative humidity at low levels;
- dry air at high altitude;
- a lifting factor such as a mountain or cold front.
"A thunderstorm can contain all the dangerous meteorological conditions known to aviation:"
- low ceilings and poor visibility;
- hail, icing;
- wind, wind gusts, microbursts (wind shear effects);
- squall lines;
- thunderbolts (lightning).
Recommendations when there is a thunderstorm:
- Do not takeoff or land: turbulence may cause a loss of control.
- Flying under a thunderstorm, even with good visibility, is dangerous because of the effects caused by wind shears and turbulence.
- If a thunderstorm covers more than half of a region, by pass it visually or with a radar.
- Frequent lightning flashes indicate a violent thunderstorm.
In a thunderstorm (when it cannot be avoided):
- Fasten your seat belt and secure all loose objects in the cabin.
- Plan your route so that you spend the least amount of time possible in the thunderstorm.
- To avoid the worst icing conditions, determine a path where the temperature is below -15°C.
- The carburetor and Pitot tube heating must be activated.
- Turn on the lights in the cockpit to reduce temporary blindness by the lightning flashes.
- Concentrate on the aircraft instruments.
- Do not modify the instrument adjustments; maintain a reduced cruising speed.
- Avoid any unnecessary manoeuvring through turbulence; corrections will only increase the strain on the structure of the aircraft.
- Never turn around once you have entered a thunderstorm.
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