The Force of Thunderstorms
June 2010
Traveling near thunderstorms ain't like dusting crops, kid. If you don't take the right precautions, you'd fly right into a cumulonimbus, or bounce too close to a supercell, and that would end your trip real quick, wouldn't it?
Thunderstorms combine all the hazards of aviation weather: turbulence, strong winds, reduced visibility, hail, ice, lightning-wielding Sith lords (sorry, lost myself). These handy packages of danger crop up suddenly, forming from clear skies in minutes, or they can build and surge for hours at a time along a strong cold front.
The FAA Aeronautical Information Manual (AIM) gives the following time-tested recommendations for flying in thunderstorm season:
Don't land or takeoff in the face of an approaching thunderstorm. A sudden gust front or low level turbulence can cause loss of control.
Don't attempt to fly under a thunderstorm, even if you can see through to the other side.
Don't fly into clouds in areas of embedded thunderstorms without airborne radar, and the training to use it.
Don't trust the visual appearance of a cloud to be a reliable indicator of the turbulence inside a thunderstorm.
Do avoid severe storms by at least 20 miles to avoid turbulence and hail. This is especially true under the anvil of a large cumulonimbus.
Do clear the top of a known or suspected severe thunderstorm by at least 1,000 feet altitude for each 10 knots of wind speed at the cloud top. This exceeds the altitude capability of most aircraft.
Do avoid the entire area if the area has 6/10 or more thunderstorm coverage.
Do regard any thunderstorm with cloud tops above 35,000 feet as extremely hazardous.
Always in motion, the future is. If you follow your plan and your avoidance plan still fails, before you face the thunderstorm's full force, consider these additional pointers from AIM:
- Tighten your seat belt and shoulder harness, and secure all loose objects.
- Hold a course to take you through the storm in a minimum time.
- Turn on pitot heat and (if you have it) carburetor heat.
- Set power for the turbulence penetration airspeed recommended in your aircraft manual. Lower retractable landing gear to increase aircraft stability.
- Turn up cockpit lights to their highest intensity to lessen temporary blindness from lightning.
- Disengage an autopilot's altitude hold and speed hold modes. These modes increase structural stress in turbulence.
- If using airborne radar, tilt the antenna up and down occasionally. This will permit you to detect thunderstorm activity at altitudes other than the one being flown.
Once you're in the storm:
Do keep your eyes on your instruments. Looking outside the cockpit can increase danger of temporary blindness from lightning.
Don't change power settings. Maintain settings for the recommended turbulence penetration airspeed.
Don't attempt to maintain constant altitude. Let the aircraft "ride the waves."
Don't turn back once you are in the thunderstorm. A straight course through the storm will most likely get you out of the hazards most quickly. In addition, turning maneuvers increase stress on the aircraft.
Trust your gut, and use your knowledge of the force of thunderstorms. If your avoidance plan fails, follow the teachings of those who came before to avoid the dark side of thunderstorm encounters.
Avemco® does not provide technical or legal advice. Content contained herein is for general information and discussion only, and is not a full analysis of the matters presented. The information provided may not be applicable in all situations, and readers should always seek specific advice from the FAA and/or appropriate technical and legal experts before taking any action with respect to matters discussed herein.
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