Instrument Student's Log
Part Five

Sat, Nov 2: In the Clouds.

Today was supposed to be a day off from training to make a trip down to Key West (EYW), the first long cross country in my plane. The ceiling and visibility were lower than we like (but still VFR). Since there was a CFII among us, he filed IFR so we could leave without waiting.

Before activating the flight plan, we did an airborne VOR check. Number two was fine, but one was about 30 degrees off, like the avionics shop said.

There was cumulus all around, and I was finally going to fly in some. I tried to maintain my heading and altitude regardless of whether the path would take us into a cloud. Several times there was a cloud directly ahead, then I'd notice that my altitude or heading was off, make a correction, and just barely miss the cloud. Whenever it was clear we'd be entering one, I tried not to look outside.

It was an odd experience, definitely harder than flying under the hood. One uncomfortable discovery was realizing that I couldn't tell in advance how long we'd be in the soup. Sometimes we'd be through the cloud in a few seconds, which was fairly easy, but any longer than that and I'd be all over the place. (Of course, if I had instrument flying down, it wouldn't matter if we were in clouds or not. It would be easier in the clouds with the hood on, since that would cut out the distraction.)

Part of the problem was that the clouds contained mild turbulence, and I'd immediately overcorrect. I didn't get into any unusual flight attitudes, but my heading and altitude were quickly off after entering a cloud. I probably didn't do any worse than anyone else their first time; at least I didn't really get disoriented.

A couple of times we were in the clear when it was time to make a turn, and the turn took us right into a cloud. That was a lot harder than my attempts to fly straight through one. We were near clouds most of the flight, but I only got about .3 hours in them.

We left Key West early enough to get back over land before it got dark. The conditions over the water were almost poor enough to be IMC. Climbing to 6000 feet, the plane climbed like we were much higher (i.e., poorly). It took us too long to realize why.

Every so often the engine sounded a little rough- not like it was about to stop, but enough to make it interesting, like the sound it makes when it's leaned too much. That was not the problem, because the mixture was fairly rich then.

Our route took us over Fort Myers (RSW), and by then I had flown about four hours for the day and needed a break, so we canceled IFR and landed there.

We had plenty of fuel to get home, but filled up again anyway since it was night, the weather in Tampa was getting worse as a cold front approached, and we might have needed to divert. The engine sounded fine on the ground; we did an extended preflight and runup before leaving on another IFR flight plan.

We were still wondering what the problem could be- did we get some bad fuel in Key West (we had checked it for water), since we'd had no trouble before leaving there? Since our engine roughness seemed to happen at higher altitudes, we asked for 4000 feet instead of 6000.

Above 3000, we heard the roughness again. Until today, I hadn't taken my plane above 3000 feet, since all I had done were short trips. But 3000 or even 6000 feet aren't really high altitudes; I've been above 12,000 in a 172 in Colorado. It takes a while to get up there, but the engine shouldn't sound different a few thousand feet up.

We continued home, and finally figured out what our problem must be. There was a lot of moisture (we were in IMC every so often), it was night, and it gets colder the higher up you go. What do you get when you combine moisture and cold air? Ice. Duh! (I like that explanation much better than "mysterious engine roughness", especially as an owner.)

We started using a minute or so of carburetor heat every few minutes, and each time we turned the heat off, the engine sounded great. When we got closer to home and descended below 3000 feet, we didn't need the carb heat until its normal use just before landing. When we got home, the ceiling was down to 1300 and dropping, and since our airport has no instrument approaches, we made it back just in time. I decided my 6.0 hours for the day was more than enough.

Glossary