Icing in the California Coast

If you are like most of us you don’t think about icing when you think about flying on the central coast of California. That would go against everything we know about the warm California sun. The palm trees, the warm white sand beaches. Well although that’s true most of the year, there are those days that the weather isn’t perfect. It just so happened that my student and I decided to go flying on one of those days.

She is working on her instrument rating and we had gotten some rain the past few days. The rain had passed but there were some lingering clouds hanging around. If you aren’t familiar with the Watsonville airport it’s an uncontrolled airport that sits a few miles away from the ocean. When we take off from runway 20 we are over the water within a few minutes after takeoff. Its a great runway to take off from. When we take off sometimes the marine layer is approaching or is over the airport. A student will takeoff and immediately be in what I consider to be safe instrument conditions as it’s not turbulent, it’s nothing but white. The student will immediately get to see what it’s like to be inside the clouds and just when they start to freak out and feel uncomfortable they break out and they get the blue skies above and the while cloud layer below, it’s quite the experience.

However clouds are not quite the same. With clouds you go in and out of the clouds depending on how thick the clouds are. You aren’t sure how long you will be in the soup or out. It’s more of a challenge for a student but she’s been doing it for a while and it would be a great experience for her.

We were scheduled for an earlier than usual flight as she had some things she wanted to do later in the day. I’m sitting at my kitchen table the night before looking at the weather and going over the lesson so that I can be prepared for any questions that might come up before or during the lesson. When I noticed that the freezing level was going to be at about 5000’. That was going to be a bit of an issue. A good portion of the approaches into the local airports have us flying between 5900’ and 7100’ to get to the initial fix. The bases of the clouds where between 700’ and 1600’ depending where in the area we were flying around and the tops of the clouds were well above the freezing level.

What conditions are needed to create ice on a plane?

Two conditions are needed for structural icing in flight. The aircraft must be flying through visible moisture. The temperature at the point where the moisture strikes the aircraft must be 0 degrees Celsius or below, aerodynamic cooling can lower the temperature of the airfoil to 0 degrees even though the ambient temperature can be warmer.

So we didn’t have to go all the way up to 5000’ to be at the freezing level and be at risk for accumulating ice.

So what do we do? Do we go shoot the precision approaches that had us flying at high altitudes and risk icing? Of course not that would be irresponsible of me.

What’s the big deal about Icing?

Icing is one of the major weather hazards to aviation. All its effects tend to want to bring the airplane down. It increases its weight, reduces its lift, decreases thrust and increases drag. What is happening is that the airplane is getting slower and being forced downward. None of this is what we want when we are flying.

How we kept flying safely.

We did the approaches that kept us lower to the surface and still give us the experience of flying in the clouds without the risk of accumulating ice. The localizer into Watsonville keeps us at 3000 feet for a short while and the VOR into salinas also keeps us at 3000’ for a few minutes. Luckily ATC gave us 2500 for most of our flight time.

It’s not something that is usually encountered or considered but should definitely be thought about this time of year. Make sure you get a weather brief before your flight and more importantly make sure you understand what the weather brief is telling you and how it can impact your flight.

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