Have an Ice Day


by Alfred Scott

This article was published in the March 1991 Falco Builders Letter.

I was happily cruising along in IFR conditions when my engine sputtered, coughed and began to lose power. Thus began the most harrowing ten minutes I've ever spent in an airplane.

It was early March, and I was on a flight from my home in Richmond, Virginia, to southern Florida. The weather was mostly VFR along the east coast, except for a band of IFR weather around Raleigh-Durham. I intended to fly over the weather and land in Charleston, which was clear.

So I cruised along at 7,500 feet above the blanket of clouds which hugged the ground, but the clouds got higher and I climbed slowly to stay above them. I eventually found myself at 12,500 feet, still on top-but there were layers of cloud above me and things were deteriorating. The prospect of completing the flight in VFR looked doubtful, so I called flight service, filed an IFR flight plan to Charleston, and then switched over to Jax Center and stood by until they could fit me into the system.

It didn't take long, and I was soon settled down at 12,000 feet, comfortably scanning the gauges as the clouds began to nibble at me, and then I was swallowed in white cloud. I've always enjoyed instrument flying, and these were the best of conditions -- plenty of altitude, silky smooth air, temperatures below freezing and lots of cloud-filtered sunshine bathing the bubble-canopied cockpit of my Falco.

It may be -- as one Italian Falco owner once called it -- "the most ugly Falco I have ever seen" but it's equipped with a full panel of King radios, and there's a reliable 150 hp Lycoming up front. In its day, this Falco has flown all over Europe, across the Atlantic, and I've had it all over the U.S. in every sort of weather condition.

Thus it was that I wiggled myself down into the seat, relaxed and busied myself with the decision of when to switch tanks -- nothing much else to be concerned about. I had just finished switching tanks when the engine sputtered, the airplane shook and the propeller blades began to flick by irregularly. Fuel pressure was fine, so I pulled the carburetor heat knob and got immediate results. The engine coughed a bit and then began to run smoothly again.

Carburetor ice. No big deal -- I've had it hundreds of times, and carburetor heat has always cleared it up. I pushed the knob back in, and within a few seconds the roughness began again. This time when I pulled the carburetor heat knob, the problem did not clear up immediately. The engine continued to stumble and shake, and the rpm's were down to idle speed, so I dropped the nose to keep the propeller spinning, called Center and told them I had a serious case of carburetor ice and requested lower. I was immediately cleared to 11,000 feet.

But things didn't improve. The engine sputtered to life and died back down again, and then the airplane began to shake very badly as the engine coughed, sputtered, surged, shook, and then sputtered again. Surely, this thing is going to clear up, but it kept getting progressively worse, and the surges back to life were less and less frequent.

Ice began to form on the windshield and along the leading edge of the wing, and I got back on the radio with Jax Center and told them that my carburetor ice problem was extremely serious, that for all intents and purposes the engine was not even running, and that I needed lower altitude because I couldn't maintain level flight. Center said that I should contact Florence Approach and gave the frequency.

I missed the frequency and called back with "Say again that frequency" and the only response was the sound of the sputtering engine. By now the engine had settled down to rather violent shaking as ice formed on the propeller, and the engine showed simply no tendency to come back to life as it coughed and backfired.

We all imagine that in situations like this we'll be Yeager-cool and calmly chat with Center as we switch frequencies, twiddle knobs, deftly analyze the problem and fix it. But this problem isn't getting fixed, there's ice forming on the wings, I'm still in the clouds, and I keep calling back for that frequency and get no reply. Again and again I call for the frequency, and all during this time the plane continues to shake and sputter as fear begins to take hold. Your forehead becomes cold, your mouth is suddenly very dry and your palms are moist. Your vision becomes constricted, and you are aware of only the artificial horizon, the directional gyro, the stubbornly pessimistic tachometer and all that white out there.

It occured to me later to wonder if the engine was really turning fast enough to power the gyros; it must have because I'm still here, but I have no idea of the exact engine speed -- such is the nature of the small mental room that fear puts you in.

The altimeter continues to unwind, and I finally get through to Center and beg for the controller to give me the frequency again very slowly, and I again repeat the seriousness of the situation -- not that Jax Center or Florence Approach can do anything to get this engine running again. I dial in Florence Approach and, as the controller talks to me, I can hear other controllers talking loudly about me in the background.

This is not a good situation and as the altitude passes 8,000 feet, I ask for a heading to the nearest airport. The controller gives me the heading, and I stare hard at the DG and struggle to figure out which direction to turn. There's a strange numbness that creeps over you and which makes even the simplest of actions seem impossibly difficult. But I make the turn and focus all of my attention on holding the heading.

The nearest airport is Dillon, South Carolina-one of those small, off-the-beaten-path, land-and-get-gas strips that I prefer to big-city airports with their procedures and maintenance forms you have to fill out just to get some fuel. I've stopped there many times before, and I begin to fantasize about dead-sticking the Falco into Dillon, rolling out at the gas pumps and asking Mr. Price to take a look at my airplane.

Such pleasant thoughts are fleeting as the engine continues to cough, sputter and shake. The altimeter contines to unwind. Seven thousand feet, six thousand feet pass by and then things start to look just a tiny bit better: the ice on the windshield begins to soften and the engine begins to occasionally surge but then dies back again. My hopes rise and then crash again as the engine continues to stumble.

At 4,500 feet, I have decided to declare an emergency -- although what difference that would make completely escapes me now -- when I break out of the bottom of the clouds and into a layer of clear air. The engine surges, coughs, backfires, surges again, and then it begins to run smoothly.

Suddenly it is as though nothing had happened. The engine is smooth and is pulling strongly. I can scarcely believe it and flip through all cylinders on my 4-cylinder CHT/EGT -- everything's just where it should be. I begin to calm down, and the numbness and tunnel vision subsides. I talk to the controller and tell him that the engine is now running smoothly. As I approach Dillon, I decide to proceed on to Florence. The weather improves, my nerves settle down, and it's obvious that I can fly in clear air to Charleston so I decide to continue the flight.

In moments like this, there are no end-of-the-movie, sunset scenes with victorious music. Instead, you go through a long period of recovering from fear, you think of your family, and you wonder what in the world just happened to you.

North of Charleston, I encounter some of the worst turbulence I've ever seen. The Falco is thrashed about violently, the g-meter shows 3-G bumps, and I hunker down with both hands holding the stick so that my head does not hit the canopy-grinning from ear to ear that my problems are so small.

After landing, I found the carburetor heat system in good working order. It took a few weeks for it to finally dawn on me what had happened on that flight. Carburetor ice is caused by the cooling effects of the venturi of the carburetor and the evaporation of the fuel. With the right conditions of moisture, the temperature in the venturi can drop to freezing and ice forms. Those conditions are normally well above freezing -- say 50°F.

And on that day, I was flying in air that was well below freezing. I suppose that supercooled moisture in the clouds might have frozen in the carburetor throat from additional cooling, but I think it's more likely that the ice was caused by heating. Remember, ice formed on the airplane only a thousand feet or so below. In other words, heat the air a few degrees, and you've got icing conditions.

The carburetor is bolted directly to the bottom of the oil sump, and it's entirely possible that the heat of the oil warmed the carburetor enough to cause a very bad case of 'internal airframe icing', that worsened as I descended into the icing layer, and which was difficult to melt with the cooled-down exhaust pipes of my barely running engine.

Who knows for sure what happened? But henceforth I'll approach icing conditions with a bit more caution -- particularly from above the icing layer and with a carbureted engine.