Everything Explained: Thunderstorm Avoidance, Penetration and Survival

Avoid the anvil (downwind) side of a thunderstorm by at least 1 mile for every knot of wind at that flight level. Avoid any thunderstorm by at least 20 miles. Getty Images

Thunderstorm Avoidance without Onboard Radar:

  • Maintain VFR conditions on top as long as possible to observe and avoid buildups. If getting on top is impossible or becomes impossible to maintain, the best option is to descend as low as possible to what may be VFR conditions below the clouds.

  • Maintain VFR conditions below the bases to observe obstacles and avoid the rain shafts. Never fly directly below a cell.

  • Daytime: Don't go where the sky is dark. Talk to ATC and get pireps.

  • Night: Don't go where the lightning is. Talk to ATC and get pireps.

NTSB Safety Alert: In-Cockpit Mosaic Imagery

The actual age of Nexrad data can differ significantly from the age indicated on the display.

The NTSB cautions pilots to be aware that in-cockpit next- generation Nexrad information can be as much as 15 to 20 minutes older than indicated on the display. Relying on such information for separation can be hazardous when aircraft are transiting fast-moving weather systems.

In-cockpit Nexrad displays depict where the weather was, not where it is. The age indicator does not show the age of the actual weather conditions but rather the age of the mosaic image.

AIM 7-1-10 — "[Flight information services] aviation weather products [iPad/cockpit display] [e.g., ground-based radar depictions] are not appropriate for tactical (less than 3 minutes) avoidance of severe weather, such as negotiating a path through a weather-hazard area. FIS supports strategic (typical time frame of 20 minutes or more) weather decision- making, such as route selection, to avoid a weather-hazard area in its entirety."

The flight information services — broadcast (FIS-B) datalink weather (Nexrad radar) you receive on your MFD or iPad is always outdated weather — potentially many minutes old.

You should not rely on FIS-B weather as a substitute for onboard weather radar. You should not use this old weather to try to weave your way through a fast-moving area of severe weather. People have died trying.

Put down that iPad and look out the window. If you don’t like what you see, turn around or land and wait it out.

Inadvertent Thunderstorm Penetration and Survival:

  • Choose the best altitude, as low as possible.

  • Tighten seat belts and secure your flight bag (so it doesn't hit the roof and deposit its contents onto your head).

  • Pitot heat, prop de-ice and/or engine anti-ice: on.

  • Cockpit lights: highest intensity. Keep your eyes on the instruments, not on the light show outside.

  • Slow down. Establish a power setting to maintain maneuvering speed (Va), but do not chase altitude or airspeed excursions.

  • Extending the landing gear can help to slow and stabilize the airplane.

An encounter with extreme turbulence is serious business. The pilot’s only job is to slow down and keep the wings level. That’s all. Nothing else really matters. If you actually do somehow manage to lose control, don’t be afraid to throw the gear out, even if you might find yourself considerably above gear-extension speed. You may shed a gear door, but that’s far better than losing a wing. It’s pretty certain the landing gear will not fall off.

  • Tell ATC — calmly and professionally, of course — that you are in extreme turbulence and you are climbing or descending right now. Do not waste time requesting permission. This is a bona fide emergency. Tell them what you are doing. ATC will automatically treat it as an emergency. You are the pilot in command. §91.3(b): "In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency." It does not say you must first get permission. Do not allow ATC to fly your airplane. You are in charge.

  • Keep the wings level. It is too late now to turn back. Load factor increases enormously in a turn.

  • Do not attempt to maintain a specific altitude in severe updrafts or downdrafts. Concentrate on keeping the wings level and the airspeed somewhere in the neighborhood of maneuvering speed.

**Extreme Turbulence **

The aircraft is being violently tossed about and is practically impossible to control. This may cause structural damage if the pilot doesn’t do something about it immediately. The airspeed indicator is usually unreadable because of extremely erratic needle fluctuations and the violent movement of the pilot’s eyes within their sockets (not to mention the movement of the pilot’s head and that flight bag bouncing off the ceiling). Extreme turbulence is undeniably an emergency. It has the potential to destroy an airplane. You do not need ATC’s permission to do something about it right now.

One more time — all together now — slow down, keep the wings level, do not attempt to maintain a specific altitude.

When you can get a few words out, tell ATC you’re in extreme turbulence and you are unable to maintain your assigned altitude at this time. Chances are there will be very few other pilots foolish enough to have put themselves into that same cloud.

After you survive the encounter, make a note to self: Never, ever put yourself in that same position again. Ever.


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