T-Storm Etiquette

Turn around or plunge ahead after an accidental thunderstorm encounter?


You may see it coming, a boiling black cloud looming in your windshield. Others will have pinned you in on either side, making penetration likely.

More likely you will not. Youll be in the clouds and pick up a little turbulence. Then a little more. Then the rain starts. It may be torrential, but you hang on, thinking itll soon be over. The sudden flash of lightning and instant crack of thunder suddenly slam you with the reality that youve gone and done something stupid.

Youve flown into a thunderstorm. Hang on, the ride is going to get wild.Tales of airplanes being ripped apart by thunderstorms are held up time and again by instructors warning the unwary against thunderstorm penetration. In the next breath, however, they admonish that if you do happen to fly into a boomer, just keep going. That sounds somewhat like warning a teenager to stay away from a gang of outlaw bikers, but if they do happen to meet up with one, go ahead and join it.

What gives?
Conventional wisdom is that the thunderstorm is probably small enough that punching right through to the other side will take less time than turning around. In addition, keeping the wings level and the airplanes speed under control will put less stress on the aircraft than turning around and minimize the chance of an upset.

That analysis has some truth as a generalization, but there are several dynamics to consider before blindly stumbling ahead into the fray.

The first step in any thunderstorm flying is to slow the airplane below maneuvering speed. Decrease power. In retractable gear airplanes, throwing down the gear will help manage speed.

Because of the wind shears inside a thunderstorm, you want to keep the load factor as low as possible to avoid overstressing the airplane. If the plane wants to climb or descend, let it to the extent practical. Obviously you should fight a downdraft if youre close to the ground, but dont worry about altitude excursions if youre up high. This is one time when youll get forgiveness, if not permission.

Turn off the autopilots altitude hold. Use the wing leveler if you want, or hand fly.

While fighting to keep the airplane in some semblance of control, consider your options. Your preflight planning should have alerted you to the possibility of thunderstorms, and its still not too late to put that information to use.

The type of storm youve penetrated can have a big influence on which strategy will work the best.

Air mass thunderstorms are generally the easiest to avoid. They are formed by thermals rising from heated ground. The sky may be filled with puffy cumulus clouds in perhaps a 1,000- to 2,000-foot thick layer, with thunderstorms dominating the air above. In an inadvertent encounter with one of these, tighten your seat belt and hang on for the ride. Fly straight through, because you probably will be through it in a short time.

Thunderstorms associated with fronts, such as squall lines, or mesoscale convective complexes cover much more ground and can be extremely powerful. The wrong move here and your wings may hit the ground in a different county than the fuselage.

Your preflight weather briefing should have given you some idea of where fronts or large scale thunderstorm activity was predicted to be. In addition, you should have been keeping up with weather enroute by using the variety of resources available through your radios. If you have on-board radar or a lightning detector, so much the better.

The extent of the bad weather, its direction, your direction relative to its shape, and the amount of notice you have before the severe turbulence, lightning and hail start will drive your next decision.

Turn Tail?
If youre flying into an area where conditions seem to be getting worse, and youre getting worried, think before you enter a turn.

Load factor in a 15 degree bank is 1.04 gs, but at 110 knots a 180-degree turn will leave you 1.3 miles to the left or right of where you started the turn.

If you were blundering through a canyon between towering clouds before you got suckered into penetrating one, youll be smack in the middle of what youd tried so hard to avoid.

Increasing the bank to 30 degrees will reduce the turn radius, so youll only be 0.6 miles lateral of your position, but youve increased the load factor by 10 percent to 1.15 gs. A 45-degree bank increases the load factor to 1.4 gs and should be avoided.

The shallower bank not only helps avoid overstressing the airplane, but also helps prevent an unusual-attitude upset and potential loss of control. For non-instrument rated pilots – and many with the rating – maintaining a coordinated turn under thunderstorm conditions is a lot to ask. The best option for aircraft so equipped may be to let the autopilot worry about the wings, while you worry about the elevator. If the autopilot executes turns at the standard rate (20 degrees), the g-force is an acceptable 1.06.

If, however, you entered a squall line that had been visible for much longer on one side of the airplane than the other, then a turn of less than 180 degrees can get you out if you turn away from the weather. In addition, continuing straight ahead could leave you flying through the line of thunderstorms the long way – an onerous possibility, indeed.

Clearly, situational awareness is critical in deciding whether to turn back or plunge forward. If you dont know which way a line of storms extends before you get to it, your fate is determined by the luck of the draw. Turn left, turn right or go straight ahead. Good luck. ATC may be able to help, but they may not.

The Air Safety Foundation reports that two-thirds of thunderstorm-related accidents end with fatalities. Those arent good odds. The wind shears can rip off tails. The hail can break windscreens and pummel wings. The turbulence and anxiety can lead to loss of control.

Thunderstorms are no place to play around. Although an inadvertent encounter wont necessarily end with your family collecting your life insurance, the possibility demands quick thinking and the relentless pursuit of weather information in flight.

Also With This Article
Click here to view “What’s Luck Got to Do With It? Everything.”

-by Ken Ibold


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