Thunderbolts:

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.

Thunderstorms:

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);
• turbulence;
• squall lines;
• tornadoes;
• 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.