The smartest way to avoid thunderstorms is to keep your distance, and never fly through embedded thunderstorms. Thunderstorms can cause aircraft structural failure and fatal accidents. But if you do find yourself in a thunderstorm, here's what you should do...

Should You Fly Straight Ahead?

According to the FAA's Instrument Flying Handbook, you should avoid turning to deviate out of a thunderstorm. When you enter bad conditions, your workload will dramatically increase as you focus on simply flying the airplane safely. It's better to maintain a straight course through the thunderstorm rather than turning around. You can, and should, declare an emergency with ATC if you get stuck in embedded thunderstorms. It will open up a new set of resources for assistance.

A straight course minimizes the amount of time in the thunderstorms and turning only increases structural stress on the aircraft (FAA).

Keep in mind, this advice is somewhat subjective. If you encounter a large, deep band of storms and your equipment (or ATC) informs you of the storm's size, you may want to find a quicker exit. A full 180-degree turn may not be the best way to exit the storm, so take in all available outside information to make your decision. Long story short, this advice by the FAA is broad and doesn't cover every situation.

Slow To Turbulence Penetration Speed

Based on the recommendations in your POH, slow to an appropriate turbulence penetration speed, which for most GA aircraft is Va. Once you reach VA, try to minimize your power adjustments, and don't "chase" the speed. Because of turbulence, it will most likely be difficult to maintain an exact airspeed, so try to stay on the slow side of your Va.

Va adds an extra level of protection if you're flying through moderate to severe turbulence in a thunderstorm.

Disengage Altitude/Speed Hold On Your Autopilot

Focus most of your attention on maintaining a level attitude, and allow your airspeed and altitude to fluctuate.

If your autopilot is engaged, consider disengaging altitude or speed hold modes while you're in rough air.

Why? Because these modes will only increase aircraft maneuvering as the autopilot tries to re-capture its altitude and speed parameters. The resulting structural stress is exactly what you're trying to avoid.

So instead, allow airspeed and altitude to fluctuate while maintaining a level attitude.

Turn Your Icing Equipment On

With convective activity, there's an increased potential for icing conditions. As soon as possible, activate your anti/de-ice systems. Icing, especially in storms, can be rapid and unpredictable.

If There's Lightning, Don't Look Outside

Lighting has serious potential to temporarily blind pilots. When flying around storms, especially at night, keep your eyes focused inside the cockpit. And at night, turn up flight deck lights to the highest setting to help avoid being blinded by lightning.

You're in IMC anyway, so there's really no advantage to looking outside at this point.

Staying Clear Of Thunderstorms

The smartest way to avoid thunderstorms is to keep your distance, and never fly through embedded thunderstorms. Thunderstorms can and do cause aircraft structural failure and fatal accidents.

Keep a safe distance, and you'll never need to use this advice. But if you do find yourself in bad weather, get out of it as quickly and safely as possible, and use all of your resources (including ATC) as soon as you can.