Wx Watch: Cloud Busting

Why you should avoid cumulus clouds

November 1, 2001

Flying over, under, or near clouds, what pilot hasn't thought, "I wonder what it's like in there?" It's a natural curiosity, and one that instrument-rated pilots have the opportunity to indulge. But does that mean barging into any old cloud is a smart or safe thing to do? No way. How do I know? Let me take you back to 1977, when a newly minted instrument pilot with an urge to build actual instrument time flew into what looked like a small, benign, fair-weather cumulus cloud.

For the most part, good VFR weather conditions were along the route from Washington Dulles International Airport to my destination, the Dare County Regional Airport in Manteo, North Carolina. I filed IFR anyway, to get more practice in the system. My clearance took me and my Cessna Cardinal RG along vectors to the Brooke VOR (no GPS back then), to Tappa Intersection, then down Victor 213 to Hopewell VOR, and on to the Franklin and Elizabeth City VORs via Victor 260 and Victor 266. After Elizabeth City, V266 takes you right to Manteo.

It was late morning — about 11 o'clock, as I recall — when I passed Hopewell. Up to then there were some scattered clouds below my cruise altitude of 7,000 feet. But now it seemed to me that the clouds were expanding horizontally and a few cloud tops up ahead were rising to my altitude. No fronts were in the area, so I assumed — correctly — that convective heating of the surface was causing the puffy cumulus on that spring day.

V260, I soon realized, would take me straight through one of those puffies. I'd drill a hole right through its midsection. Oh, well, I'm instrument-rated, I assured myself, and I badly wanted more actual time.

Who knows how close I was when the first turbulence began. A mile? A half-mile? All I know is that this cloud was surrounded by invisible zones that I think of as rings. The outer ring, the one with the first turbulence, gave but a forewarning of what was to come.

This first turbulence was — how can I describe it — like a nibbling sensation. Yes, that's it, a few tentative mini-bumps and ever-so-slight bobbles in pitch and roll. I think of the way a fishing rod might transmit a fish's first bites on a lure, before the hook is set. I was that lure.

Getting closer, the turbulence increased. I'd call it good, solid shots of moderate turbulence. The kind that make the stall horn give a sudden, sharp bleat and send your head crashing into the headliner.

I moved to tighten my seat belt after this, then looked up to see that I was about to enter the cloud. Did it seem much larger than it had a minute or two ago, or was it just that I was closer?

Then I was in the cloud, and the next jolt of turbulence caught me just as I was reaching to tighten my seat belt. It made me miss the belt. My fingers caught the latching mechanism by mistake. Click. It was with near-disbelief that I realized that I had unlatched my seat belt.

Floating free, my head slammed hard into the aluminum above the headliner. At the same time all my charts flew away — most to the backseats — and my headset was knocked askew. More turbulence.

I looked at the instruments and saw that I was in a 60-degree bank, with the airplane's nose pointing at the moon. After frantic, weightless groping, I found the seat belt's latch and metal tongue, put them together, and yanked it tight. I looked up and saw that I was rolling 60 degrees — no, more — the other way. I heard a tremendous rushing sound, saw the airspeed indicator pushing redline, and yanked all the power off. In spite of my new, extreme nose-down attitude I saw the altimeter winding up like a hyperactive clock. Just like in the movies, the hands spun around and around in a near-blur. Where is the top of this cloud? I passed through 10,000 feet and was still in it, and the altimeter was still winding up.

Then it got dark. Ominously so. The instruments were a blur, but through the windshield it was a dark, dark gray. Or was it? The color seemed now pearlescent, then a sickening, electric green. I tried to get a message off to ATC but had trouble keeping my finger on the transmit button. Finally I managed to say, "Center, this is Cardinal 35914…unable to hold altit — …," and hit my head again. The airframe groaned after a fresh shot of turbulence.

First things first. Back to the gauges. Concentrating became more difficult. First it was the turbulence, now it — oh, no — a sudden, fiendish hammering was felt on the airframe. It must be what a bullet hit sounds like. But it wasn't bullets. It was rain. Or hail.

By now I was beyond concerned. I was venturing into the early stages of panic. Just when would this cloud spit me out the top? Would the airframe hold up? Back to the gauges. Heading down now, the airspeed was still well within the yellow arc, the power still off, the altimeter spinning downward. Rolling at wild angles. Rain on top of rain. Rain coming in the sliding, wing-root "orange juice cans" that serve as cabin fresh-air inlets, just gushing in, and spraying all around the cockpit. On the gauges. On the avionics. In my face.

Still another jolt. The stall horn went off. I then felt what must have been at least a three-G force. I was on the roller coaster again, and going back up. More Gs. Then back down again. This time I saw the attitude indicator banking past the 90-degree mark. I thought about yanking on the ailerons to roll the airplane upright, but worried too much about overstressing the airframe. I was convinced that the airplane was about to roll inverted.

A second passed and the rolling subsided to a mere 60 degrees. I remembered something from a textbook, and extended the landing gear in an attempt to damp the rolling and slow the airplane. I say attempt because I was still in unusual attitudes, and still distracted by the jolts and the rain. A final jolt, a final yank on the yoke to correct it, and I came out of the bottom of the cloud. I was at 4,300 feet. In clear air.

I righted the airplane and left the demon cloud on a southerly heading — only to later find out that the heading indicator was way, way off after all those gyrations. I synched the heading indicator to the magnetic compass, intercepted V260, and flew away. The turbulence subsided. All of a sudden, it was a nice day. I no longer had charts but didn't care — and I didn't dare risk groping around in the back, for fear of once again getting hit by unanticipated turbulence.

After I checked in with ATC and assured them that I was truly on my way and back at 7,000 feet, I looked back, turning the airplane to get a better look.

There it was. The cloud that had terrorized me. It was a towering cumulus. A hard, sharp edge of billowy white etched against the deep, blue sky. And the sharp edge was still climbing. Within 15 minutes it was a full-blown thunderstorm. I know because I kept turning to watch its progress.

Flash forward to last year. I'm teaching an aviation weather course and a student asks, "What if there's a storm along my route and my clearance takes me through it?" He thinks that if he's on an IFR flight plan he must adhere to his route or clearance, no matter what.

"Ask for a deviation. You'll probably get it. If you don't, deviate anyway, explaining the situation to the controller," I answered. Then I told him that I diligently try to avoid all cumulus clouds, whether I'm flying VFR or IFR.

Now you know why.

E-mail the author at tom.horne@aopa.org.