Thunderstorm Avoidance

Every pilot knows not to tangle with thunderstorms, but weather is sometimes unpredictable and unexpected, and unfortunately, pilots can get caught in it. How can a pilot stay well informed about the weather along his route of flight? What weather factors should be considered before taking off, and reevaluated along the way? How does one plan for an "out" where a safe landing can be made if necessary?

Part 1 is a compilation of articles and publications from AOPA Pilot, AOPA Flight Training, and the AOPA Air Safety Foundation that includes information on how to anticipate and avoid thunderstorms along your route of flight.

Part 2 includes articles discussing lightning strike protection for aircraft.


Table of Contents

Part 1: Anticipating and Avoiding Thunderstorms

The Weather Never Sleeps
Boom and bust: Learning the life cycle of thunderstorms
By Jack Williams
AOPA Flight Training, April 2006

The cycle begins when warm, humid air rises and its moisture begins to condense into the tiny water drops of a cloud. If the air rises high enough it cools below freezing and the drops become supercooled. Eventually ice crystals begin forming. This is called the cumulus stage because the potential thunderstorm is a cumulus cloud. If conditions aren't favorable, the process can stop here as the cloud drifts with the wind, never dropping any rain before it evaporates.

Instructor Report: ASF Safety Spotlight
Some things are best avoided
By Kristen Hummel
AOPA Flight Training, August 2005

With the thunderstorm season here, it's important for pilots to understand the characteristics of thunderstorms — and avoid them. On June 14, 2002, the pilot of a Piper Malibu and his two passengers were killed after the airplane entered an uncontrolled descent while trying to navigate through convective activity near Osteen, Florida.

Wx Watch Squall-Line Lowdown
Not your typical convective mayhem
By Thomas A. Horne
AOPA Pilot, July 2005

It's challenging enough to cope with "garden variety" thunderstorms, what with all the extra preflight weather research and in-flight monitoring that safe flying demands in the convective season. To all that, factor in other brands of convective activity that require as much, or more, vigilance (see "Safety Pilot Landmark Accidents: Midlevel Mayhem"). We're talking about squall lines — a phenomenon that's all too often given short shrift in aviation weather texts. But while this violent weather may be mentioned only in passing, it can ruin your day if it catches you unaware.

Wx Watch: The Eyes Have It
Buy storm-avoidance gear, but trust your eyes
By Thomas A. Horne
AOPA Pilot, May 2005

Now that thunderstorm season is upon us, it's time to recall the prime directive for guaranteed storm-cell avoidance. It's a very important rule, and one that should be kept firmly in every general aviation pilot's mind, whether he or she is a neophyte or a grizzled high-timer with a logbook bulging with actual instrument time. Can you guess what it is? Don't worry, the answer isn't complicated. Here it is: Keep your distance from cumulonimbus clouds, and the clouds surrounding them.

Waypoints: Beating around the Bush
By Thomas B. Haines
AOPA Pilot, October 2004

All week, the weather forecasters had been calling for a band of strong thunderstorms to stretch from about Bradford, Pennsylvania, down into Louisiana. My route from Wisconsin to Maryland meant I'd either have to penetrate the line or take a detour to either Canada or the Gulf of Mexico. Neither sounded very appealing.

Learning Experiences: Holy shear!
Wind shifts not fun in the summertime
By Marc H. Greenstein
AOPA Flight Training, July 2004

Accidents often result from a series of bad judgments. Now I know this is true for close calls as well. I promised my visiting nephew an airplane ride, and I was determined to live up to my word. There were two storm pockets evident — one to the southwest and one to the north-northwest. Both appeared to be stalled in their current positions.

Wx Watch: Storm Season Insights
Checking out some bad neighborhoods
By Thomas A. Horne
AOPA Pilot, May 2004

We've all been there. You're at the airport or standing in your yard and you notice the dark, low-lying clouds rushing by on strong southerly winds. An oppressive humidity lends palpable moisture to the air. The temperature has sharply increased over the past few hours, too. There's a definite sense of imminence about this weather. What's imminent is usually one or more thunderstorms, probably of the severe variety.

Safety Pilot: Near misses with boomers
By Bruce Landsberg
AOPA Pilot, May 2004

It's thunderstorm season once again and throughout the magazine you will see plenty of references to why messing around in the big clouds is a bad idea (see "Wx Watch: Storm Season Insights," page 123). Searching AOPA Air Safety Foundation's database for accidents that occurred during the summer months will yield a number related to convective activity. Many of these accidents are fatal, but a number of pilots have just missed a storm and come back to tell stories about getting too close. In more than a few cases these pilots were staying what they thought was a safe distance away from storms when they got into trouble. A common thread is the speed at which conditions changed.

The Weather Never Sleeps: Spring's special storms
Winter's last gasp agitates April's air
By Jack Williams
AOPA Flight Training, April 2004

When April rolls around, winter is in full retreat across almost all of the United States, but it doesn't give up without a fight. And when the weather is in a fighting mood, pilots need to stay alert. In addition to new leaves on trees, blooming flowers, and pilots no longer freezing their fingers during preflight inspections, spring also heralds the arrival of thunderstorms.

Wx Watch: Super Storms
Big-time Convection
By Thomas A. Horne
AOPA Pilot, July 2003

When we think about thunderstorms, we often imagine an idealized representation of an air mass or frontal storm. You know, cauliflower tops, anvil clouds, scary radar signatures, one-hour life spans, and the other generalities and warnings that go with the adverse conditions associated with all convective storms. But there are other types of thunderstorms that are very, very bad news for any pilot of any airplane who ventures into their vicinity. As we all know, any type of thunderstorm should be avoided at all costs. But the ones summarized below — while they don't get a lot of press — can be the most dangerous of all convective systems. I mention them here precisely because they aren't widely addressed, but pilots should understand how they form, their life cycles, and their characteristic behaviors.

Wx Watch: Storm Vision
Surfing for safe outs
By Thomas A. Horne
AOPA Pilot, June 2003

Pilots have a built-in dread of inadvertently flying into thunderstorms. But there are some forecast tools that we should all be aware of — and use — in the convective season. Understanding them means fewer surprises, better flight planning, and less chance of stumbling into a storm. These forecast tools can be found on several popular Internet Web sites.

Too Close for Comfort
A DC-9 has a close encounter of the scariest kind
By Bruce Landsberg
AOPA Pilot, June 2003

It's been said that history has a way of repeating itself for those who do not heed past lessons. In April 1977 a Southern Airways McDonnell Douglas DC-9 tangled with a thunderstorm that smashed the windshield and flamed out both engines. That resulted in a dead-stick landing with heavy loss of life (see "Safety Pilot Landmark Accidents: Deadly Surprise," August 1998 Pilot). The crew misread the weather radar and flew into a cell with massive rainfall that literally snuffed out the engines. Twenty-one years later, on May 7, 1998, about 7:20 p.m. Eastern Daylight Time, another DC-9, operated as AirTran Airlines Flight 426, nearly replicated the earlier accident and, again, confirmed that thunderstorms should be given a wide berth.

Wx Watch: Dawn Patrolling
By Thomas A. Horne
AOPA Pilot, May 2003

Thunderstorm season has begun and, admit it or not, pilots fill with a certain dread. Anyone planning a cross-country flight of any duration has to wonder if thunderstorms will become a factor. Let me give you the single most important tactic in avoiding thunderstorms. This is simple advice, and it's almost foolproof. Plus, it has nothing to do with interpreting charts, convective outlooks, or other sometimes-confusing briefing tools. Ready to copy this advice? OK, here it is: Take off early in the day. So early that you'll arrive at your destination before noon.

The Weather Never Sleeps: Thunder and Lightning
By Jack Williams
AOPA Flight Training, July 2002

One of the main weather lessons that pilots learn is to "stay away from thunderstorms." Warnings about thunderstorm dangers usually focus on the horrendous winds — including the vertical winds called updrafts and downdrafts that can create turbulence and throw an airplane out of control. Surprisingly, little mention is usually made of the reason that thunderstorms are called thunderstorms — lightning.

Wx Watch: Storm Forecast Insights
By Thomas A. Horne
AOPA Pilot, July 2002

The morning surprise. That's what I call the shock that pilots get when they call flight service and hear of a sudden change — for the worse, of course! — in the day's forecast. This can be especially frustrating during the warmer months of the year. Yesterday, the briefers' forecasts were for a walk in the meteorological park, and featured mentions of severe-clear, light winds, and minimal turbulence. This morning the world changed, and now potentially severe air mass thunderstorms are heavily advertised. How could things have gone downhill so quickly?

Never Again: Wall of Water
By Randall E. Walker
AOPA Pilot, September 2001

According to the briefing, the front left a few lingering clouds in its wake. En route, we should expect just a layer of harmless cumulus at 4,500 feet with a few more clouds at lower altitudes and some scattered precipitation at the destination. Then came the first indication of what lay ahead — the briefer noted a slight chance of thunderstorms. "Should be widely scattered, no greater than Level 2 or 3; chances are good no storms will develop," he said.

Thunderstorms, Restricted Airspace, and a Dust Storm
By Greg Brown
AOPA Pilot, August 2001

Unpredictable as thunderstorms are, the secret to flying safely on such days is to lighten up on your mission objective. Don't get hung up on the final destination — just make sure you can proceed safely somewhere for landing, from any point where you elect to fly.

Flying Safe: The Weather Never Sleeps, Somewhere in the Middle
By Jack Williams
AOPA Flight Training, August 2001

Over the last couple of decades scientists have put a lot of effort into learning more about what they call mesoscale weather, which turns out to be the kind of weather that can cause pilots a lot of trouble.

Wx Watch: Surviving the Scare
By Thomas A. Horne
AOPA Pilot, July 2001

The worst has happened. Your plan to maintain visual separation from cloud buildups fell apart. After 20 nerve-wracking minutes of weaving around and through ever-darkening clouds, you never found a path to clear air. What looked like your last hope — squeezing through a narrow shaft of cloud-free sky toward a promising brightness — was instead a trap. The brightness was the sunlit flank of a towering cumulus cloud. And you just flew into it.

Landmark Accidents: Bowling Alley Blues
By Bruce Landsberg
AOPA Pilot, June 2001

The crash of American Airlines Flight 1420: Caught between a thunderstorm and a hard place.

Wx Watch: Preflighting for Storms
By Thomas A. Horne
AOPA Pilot, June 2001

The goal of the preflight process is to make a good, safe go/no-go decision. And sure, the weather is a big, big part of the decision. But the pilot and the aircraft are extremely important variables in the process that are often overlooked.

Never Again: Thunder in the Night
By David M. Tarlow, MD
AOPA Pilot, April 2001

A thunderstorm cell approximately 10 miles wide was traveling in a northeasterly direction. However, the briefer felt confident that this cell would not be a factor and predicted that it would pass west of my destination by the time of my arrival.

Waypoints: Weather Decisions
By Thomas B. Haines
AOPA Pilot, September 2000

Most pilots associate the worst and most fearful flying weather with the winter months. Normally, I would agree, but this spring and summer seem to be an exception.

Flying Safe: The Weather Never Sleeps, Supercell Thunderstorms
By Jack Williams
AOPA Flight Training, June 2000

Each spring the weather begins brewing the especially fearsome thunderstorms known as supercells. While they are best known for spinning out the strongest tornadoes, supercells also create other, less obvious hazards that even the best pilot in the strongest airplane should always avoid.

Waypoints: Using Weather Tools
By Thomas B. Haines
AOPA Pilot, September 1999

Few words from a flight service briefer gain the attention of a pilot faster than convective sigmet. When those were the very first words from the briefer, I knew it was going to be a most interesting weather day — and I would be at 8,000 or 10,000 feet dealing with it while the briefer finished his shift comfortably behind his computer console.

Safety Pilot: Landmark Accident: JFK
By Bruce Landsberg
AOPA Pilot, June 1999

On the anniversary of a major airline accident that occurred almost a quarter of a century ago, the issues of thunderstorm avoidance have not changed. Although the technology has improved, pilots should be as cautious as ever.

Weather Tactics: Weather, ATC, and You (requires Adobe Reader)
AOPA Air Safety Foundation, 1998

These pages will take you on "Operation Rain Check" tours of Washington Dulles International Airport (KIAD), the Washington Air Route Traffic Control Center (ZDC), and the Leesburg (Virginia) Flight Service Station. These facilities provide information that can help you make decisions critical to your success in avoiding hazardous weather.

In-Flight Emergencies: Flying in Storm Central
By Thomas A. Horne
AOPA Pilot, May 1999

Stumbling into a thunderstorm. It's the stuff of every pilot's nightmares. What makes the fear even more plausible for pilots of small general aviation airplanes are some of the inherent shortcomings bound up in this kind of flying.

Flying Safe: Learning Experiences, Thunderstorms and Microbursts
By Robert N. Rossier
AOPA Flight Training, September 1998

Conditions were VFR in Albuquerque, New Mexico (ABQ), for their May afternoon pleasure flight, but trouble was brewing all around. The ABQ Low Level Wind Shear Alert System (LLWAS) issued numerous wind shear alerts in all quadrants, virga prevailed in all directions indicating the potential for microbursts, and the westerly wind was 17 gusting to 37 knots under a 6,000-foot broken ceiling. Cumulonimbus clouds were reported northwest, and thunderstorms were boiling up to the northeast and south.

Safety Pilot: Landmark Accidents: Deadly Surprise
By Bruce Landsberg
AOPA Pilot, August 1998

Everyone knows that thunderstorms need to be avoided. Yet, to fly in the season we must operate with them around. But even for seasoned pilots Thor may have a few surprises — something that didn't appear in the rulebooks or a situation that looked so similar to previous circumstances that pilots were tempted to try a strategy that always worked before. Here are two accidents in which both aircraft had their windshields broken, with subsequent forced landings.

Flying Safe: The Weather Never Sleeps
By Jack Williams
AOPA Flight Training, August 1998

About 80 percent of the summer rain between the Rockies and the Appalachians comes from huge clusters of thunderstorms known as "mesoscale convective complexes" or "MCCs."

Wx Watch: Convective Calamities
By Thomas A. Horne
AOPA Pilot, June 1998

Case studies of how things go wrong in thunderstorm season. No theory here. We're talking about the realities surrounding thunderstorm accidents. The following accident synopses are instructive because they are so typical in their unfolding. And the lessons are so clear that there's no need for pontification.

Weather Strategies: Weather, ATC, and You (requires Adobe Reader)
AOPA Air Safety Foundation, 1998

"Weather Strategies," an AOPA Air Safety Foundation safety seminar, takes pilots through the planning portion of a flight that seems, at first glance, impossible to fly. But, is it? Join us as we study the weather, think about our options, and decide whether to go.

Summer Weather: Navigating Summer's Worst
By Thomas A. Horne
AOPA Pilot, June 1997

Summer's here, and with it come equal measures of pilot joy and dread. Joy, for long, warm days and trips to vacation spots. Dread, for the threat of thunderstorms, haze, mean fronts, and turbulence. But by preparing yourself with the right kind of preflight and in-flight weather information, you can keep those ugly weather surprises to a minimum.

Safety Pilot: Learning About Boomers
By Bruce Landsberg
AOPA Pilot, June 1997

Thunderstorm learning begins in earnest when pilots start to fly real, not contrived, cross-countries. The "warm-up" nature of most private pilot and instrument certificate curricula is not designed to cover the topic in detail. Limitations of aircraft and self are best learned early because thunderstorm entanglements, when they turn into accidents, are more than twice as deadly as the typical GA accident.

Wx Watch: Cold Facts About Cold Fronts
By Thomas A. Horne
AOPA Pilot, April 1997

A cold front is predicted to arrive soon or to be a factor in your flight. What does this mean to you? Perhaps nothing. Perhaps deviating a hundred miles. Perhaps canceling the flight altogether.

Wx Watch: Storm Warnings
By Thomas A. Horne
AOPA Pilot, April 1996

In the study period — from 1982 to 1993 — there were 204 accidents in which thunderstorm activity was named as a cause or contributing factor. In 77 percent of the cases, or 157 accidents, there were injuries. The fatality rate was 66 percent, meaning that of the 157 injury-producing wrecks, 135 involved one or more deaths.

Flying Safe: The Weather Never Sleeps: Cell Games
By Jack Williams
AOPA Flight Training, April 1996

Here are some of the basics of today's understanding of thunderstorms. The needed ingredients are as described in Aviation Weather: unstable air that will continue rising once it is given an upward shove; plenty of humidity to condense into clouds, rain, and hail, releasing heat that keeps the air rising; and something to give the air that initial upward shove.

Safety Pilot: Blown Away
By Bruce Landsberg
AOPA Pilot, June 1995

There were ill winds last July when a DC-9 and a Beech Bonanza became victims of thunderstorm wind shear. The two accidents recounted here are flip sides of the same coin. The phase of flight and the circumstances are different, but the aerodynamic and avoidance principles are the same.

Wx Watch: Steering Clear of Convection
By Thomas A. Horne
AOPA Pilot, June 1994

It's summer, it's prime time for flying, and everyone is eager to make those trips planned so enthusiastically during winter's gloom. Unfortunately, we all know that this time of year is also prime time for thunderstorms, one of aviation's most serious weather hazards.

Wx Watch: The Thunderstorm Accident
By Thomas A. Horne
AOPA Pilot, August 1993

Thunderstorms are especially deadly because of the violent turbulence and wind shear that they contain, and the fact that this mayhem often takes place in instrument conditions.

Thunderstorm Avoidance
By Archie Trammell
AOPA Flight Training, August 1990

Although this time of year provides some of the best flying days, it's also the time of thunderstorms. No one intentionally goes looking for these storms, and you can avoid them with careful preflight planning.

Part 2: Lightning Strike Protection for Aircraft

The Road Less Traveled: What It Takes To Certify an Aircraft in America
By Nathan A. Ferguson
AOPA Pilot, April 2003

Cirrus did its testing at the Frankensteinlike lab of Lightning Technologies Inc. (LTI) where engineers come up with worst-case scenarios. "No two lightning strikes are the same," says LTI senior engineer Ed Rupke.

Airframe and Powerplant: Simple but Strong
Composite airplanes are tough — easy to repair
By Steven W. Ells
AOPA Pilot, April 2002

Since Lancair airplanes comply with the lightning-strike requirements for certification by embedding nonwoven aluminum or copper mesh over the entire airframe, we learned how to use a portable vacuum bagging procedure to install new mesh over the repaired areas.

DA40-180 Diamond Star: Star Over Canada
By Alton K. Marsh
AOPA Pilot, March 2002

The aircraft has carbon-fiber wings and a fiberglass fuselage. Lightning protection is provided by embedded metal strips that direct the energy away from vital aircraft systems.

Launching Columbia: Lancair Shoots for the Stars
By Mark E. Cook
AOPA Pilot, October 1997

All Columbia models will be approved for IFR day and night flight, thanks to lightning-protection technology explored in a NASA-funded program using a Glasair III kitplane. The Columbia will employ an expanded-foil mesh under the primer coat, above the composite materials themselves.

FAR 23.867 Electrical bonding and protection against lightning and static electricity