When thunderstorm activity is forecast, limit
flying to VFR, since it’s difficult to avoid what
we can’t see. Avoid all thunderstorms by a
healthy margin—at least 20 miles for severe
thunderstorms—and avoid areas of vertical
buildups, rain shafts, and virga (rain that
doesn’t reach the ground). Virga signals powerful downdrafts and potential microbursts.
Look at the direction in which the top of the
thunderstorm is being torn by upper level
winds, forming the “anvil.” Give that side of
the storm an even wider berth, as this is often
the direction in which hail is thrown. Never fly
beneath a thunderstorm or near visible shafts
of rainfall. Avoid flying between cells, as these
areas can also have severe turbulence.
Ragged, dark bottoms of cumulus clouds
signal thunderstorms and other dangers,
including the potential for tornadoes.
Blowing dust and debris on the ground can
indicate the gust front of an approaching
thunderstorm. Never take off or land within
5 miles of a thunderstorm or squall line.
WORST CASE SCENARIO
For the unlucky pilot who gets caught in a
thunderstorm, the key to survival is knowing
what to do. The primary goal is to avoid
overstressing the airframe. If the airframe
fails, the ride is over.
At the first sign of turbulence, slow the
aircraft below maneuvering speed for the
actual aircraft weight, as flying fast in
turbulent conditions is a passport to peril.
Remember that the published maneuvering
speed is for maximum gross weight, and the
value decreases as the weight decreases.
Know the worst case maneuvering speed for
your aircraft—just you and minimum fuel—
and use that number when in doubt. Better
yet, keep a card handy listing maneuvering
speeds for a variety of weights.
Next, get organized and secure all loose
items in the cockpit. It’s going to be a rough
ride, and loose items can become projectiles.
Passengers should tighten their seat belts,
and tighten yours as well. Turn up the radio,
as pelting rain can make a tremendous
racket. At night, turn up the cockpit lights to
reduce the potential for being blinded by
flashes of lightning.
Robert N. Rossier, EAA 472091, has been flying for more
than 30 years and has worked as a flight instructor, commercial pilot, chief pilot, and FAA flight check airman.