Riding The Storm Out

Adverse weather is one of the hazards aviators always must contend with. It could merely be a stiff, 90-degree crosswind at your destination airport, or ceilings right at minimums for the best approach. In-flight icing. Hail. Thunderstorms. From early in our training, we are taught—or should be taught—to avoid extreme weather conditions by flying around them, under them, over them or by not flying at all.

To help with our decision-making, we have near-real-time, detailed, hi-def color graphics on a tablet in the cockpit showing us where the poor conditions are. On the ground, we can simply pick up the phone and talk with Flight Service to get their opinion on your plans. There’s also the area forecast discussion. All of these resources can help us figure out why the conditions are as they are and where they’re going to be a couple of hours from now, when we get there. We also have the Mark I, Mod 1 eyeball we should be using when we’re up close and personal to hazardous weather to avoid the worst conditions. As we’ve said many times before in these pages, the best way to avoid entering a thunderstorm is to stay in visual conditions and navigate around them. Or land and wait them out. Period, full stop.

But there you are, droning along, fat, dumb and happy, in IMC and on an IFR flight plan, when all hell breaks loose. It almost doesn’t matter how you got here. Almost. But here you are, in a thunderstorm. The chances of getting out of it in one piece, literally, aren’t great. What can you do to maximize them?

Don’t Try This At Home

Before I get into the meat of this discussion, let me state unequivocally that I am by no means advocating flight into—or even close to—a thunderstorm. This includes rainshowers, virga and even tall cumulonimbus clouds, which are almost guaranteed to have unpleasant and dangerous turbulence in and around them. A personal airplane—even if it’s a 747—has no business there. Sorry—if you thought flying your brand-new WhizBang 1000 twin turboprop with all the bells and whistles means your airplane is immune to weather, someone needs to take you aside and explain why that’s not the case.

And I don’t care if you think you’re the embodiment of the Wright Brothers, Chuck Yeager and Neil Armstrong all rolled into one—you’re not, and even they wouldn’t knowingly fly into a thunderstorm. In fact, Scott Crossfield, the first pilot to fly at Mach 2, died when his Cessna 210A inadvertently entered a thunderstorm, thanks in part to poor ATC performance, and came out the bottom in more than one piece. So, no, you’re not good enough to deliberately fly into a thunderstorm and realistically think you’ll be able get out of it. So don’t even try.

Preparation

The FAA Advisory Circular AC 00-24C, Thunderstorms, has some recommendations if you’re unable to avoid penetrating a thunderstorm:

Tighten the safety belt, put on the shoulder harness (if installed) and secure all loose objects.
Plan and hold the course to take the aircraft through the storm in minimum time.
To avoid the most critical icing, establish a penetration altitude below the freezing level or above the level at which OAT is -15 degrees C.
Verify that pitot heat is on and turn on carburetor heat/alternate air or turbine engine anti-ice. Icing can be rapid at any altitude and cause almost instantaneous power failure and/or loss of airspeed indication.
Establish power settings for the turbulence penetration speed recommended by the manufacturer (see the sidebar on the opposite page).
Don’t change power settings; maintain settings for the recommended turbulence penetration airspeed.
Maintain a constant attitude. Allow the altitude and airspeed to fluctuate.
Turn up cockpit lights to the highest intensity to minimize the risk temporary blindness from lightning. Focus on the flight instruments, not outside.
If using an autopilot, disengage altitude-hold and airspeed-hold modes. You don’t want to try to maintain either altitude or airspeed; doing so will increase structural stress.
If using airborne radar, tilt the antenna up and down occasionally. This will permit the detection of other thunderstorm activity at altitudes other than the one being flown.

We’ll add one more: Let ATC know you’re going to be off your altitude; maybe ask for a block a couple of thousand feet higher and lower than your current altitude.

Maintaining Control

As always, the pilot’s first task is to maintain control of the aircraft. The idea here is to keep the wings and pitch attitude level and accept variations in both altitude and airspeed. Although the FAA’s guidance advocates for a constant power setting, there are airspeed extremes we want to avoid. The only way to do that may be to adjust power.

The rest of it is basic stick and rudder skills. The least stress on the airframe is achieved in 1G flight, but that may not be possible. One thing you definitely don’t want to do is abruptly apply control inputs, especially in the pitch axis, as if you’re trying to maintain altitude or airspeed. These values must be allowed to fluctuate with the storm’s up- and downdrafts. If anything, you want to fly as gently as you can, slowly applying only enough control inputs to level the wings and nose. Fly the attitude indicator, not the vertical speed indicator or altimeter, and accept the climb and/or descent rates you encounter.

Please Don’t Do This

A few years ago, a Pilatus PC-12 came apart in the flight levels while penetrating a thunderstorm over central Florida, dramatically killing all aboard, a young family. It was a local news story for a couple of days, focusing on the family members. Several weeks later, I was at an event with my own extended family and was asked about it: “What happened?” I responded, “The guy flew into a thunderstorm. What did he think was going to happen?” And that’s probably the same answer they’ll be giving a few days later at your accident site.

I subscribe to email alerts from the FAA Air Traffic Control System Command Center’s Aviation Information System, which advises system users on the operating status of the nation’s largest airports, including delay information. It’s a service designed mainly for commercial operators, although it’s useful for frequent travelers. Adverse weather like thunderstorms regularly result in lengthy terminal, regional and national delays. That shouldn’t come as a surprise.

What should interest you, however, is how seriously the FAA, ATC and commercial operators take thunderstorms. Frequent ground stops are put in place throughout the system to prevent the kind of congestion and delays airline passengers rarely understand but uniformly loathe. Some of it is about managing ATC’s workload, but a lot of it is about avoiding severe weather and safely completing the flight. When the big boys are taking thunderstorms seriously, shouldn’t you? Prevention is the best cure.

Turning Around?

The FAA-recommended way to exit inadvertently entered instrument conditions is to turn around: Using the flight instruments, enter a level standard-rate turn and perform a 180-degree course reversal immediately. By definition, it takes one minute and will have you headed the other way, most likely out of the weather you just entered. The same can be true of a thunderstorm. Maybe.

In Advisory Circular AC 00-24C, Thunderstorms, the FAA specifically recommends not turning around: “A straight course through the storm most likely will get the aircraft out of the hazards most quickly. In addition, turning maneuvers increase stress on the aircraft.”

We’re in the “it depends” camp on turning around. To us, it’s a flip of the coin whether the shortest path out of the storm is ahead of you or behind. Note that a standard-rate 180-degree turn always will take a minute to perform. It could be the longest minute of your life. Of course, you need to be alert and proficient enough to both recognize you’ve entered a storm and perform the level 180-degree turn. The accident record tells us that can be a challenge for many pilots. Successfully performed, the 180 should get you back into clear air, where you can put some distance between you and the storm, then figure out what to do next and where to go.

Regardless, you shouldn’t wait very long before executing the turn. It’s a pilot’s nature—and the FAA’s apparent policy—to think the storm won’t be that large and can be quickly transited to clear air, and he or she can maintain control while waiting to pop out the other side. It’s reminiscent of a line from a Dirty Harry movie: Do you feel lucky?

A final caveat is that you probably should slow down, way down, first. As the sidebar on the opposite page discusses, you need to be at or below your airplane’s weight-adjusted maneuvering speed (V_A) or maximum gust intensity speed (V_B), if one is published.

What Speed To Fly?

There’s a reason your airplane has no V-speed specifically designated for thunderstorm penetration: No manufacturer with a legal department would publish such a recommendation. Instead, they have something else. For example, Cessna’s POH/AFM for the 1979 T210L Turbo Centurion includes weight-adjusted “maximum recommended turbulent air penetration speeds” which are identical to the maneuvering speed (V_A) found in the same document. Beechcraft’s POH/AFM for the F33A Bonanza merely lists a single maneuvering speed, which it says is “the maximum speed at which application of full available aerodynamic control will not overstress the airplane.” Regardless, the speed at which you fly your typical small airplane in a thunderstorm should be lower than the published maneuvering speed at maximum weight. Why?

When a single maneuvering speed is published, it’s the one to use at the airplane’s maximum gross takeoff weight. But we’re never really at that weight while airborne, since we’re lighter after some fuel is burned off. How much lighter depends, of course, and is something the pilot will need to compute. As discussed in a March 2022 article, there’s a way to figure the new, lower-weight V_A using calculus and another one using a rule of thumb. The latter is almost as accurate as the one requiring math, and easier to do while holding onto the yoke at 180 knots. Using the rule of thumb, maneuvering speed should be reduced by half of the percentage decrease in weight.

As an example, presume an airplane with a 3000-pound maximum gross weight and a 130-knot V_A. Further presume its actual weight is 300 pounds lighter, 2700 pounds, or 10 percent of the gross. Half of 10 is five, so we reduce the gross-weight V_A by five percent. Five percent of 130 is 6.5 knots, so our new weight-adjusted V_A is 123.5 knots. The rule of thumb tends to err slightly on the high side, so we’d establish 122 knots as our new maneuvering speed. But remember, we want to be below V_A, so let’s use 120 knots as our weight-adjusted maximum turbulence-penetration speed.

One thing typically omitted from these discussions is how slow we can fly. This article’s main text goes into greater detail on airspeed and attitude management, but we’d establish the airplane’s best-rate-of-climb speed (V_Y) as our minimum speed to fly in turbulence. Why? Because we don’t want to get slower and risk a stall.