|Written by Jon Reed|
Hello again from my world of flying! Quite a bit has happened since the last update. I got my CFII after taking my time to get comfortable instructing, learn the local area approaches and getting some actual instrument time. The checkride went very well and I have been lucky enough to currently be instructing a few instrument students. The weather has been great for instrument flying with relatively high freezing levels and a few weeks ago I doubled my actual instrument time in just one week. Oregon is a great place to build instrument experience and confidence as well as judgment regarding the go- no go decision. I have learned some valuable lessons, in particular about icing, which is the focus of this months article.
I had my first encounter with icing, which luckily I was able to get out of, however the fact that I allowed myself to get into that situation shook me up and really made me rethink my go-no go decision. Legally I had covered myself. No known icing (no pireps), the forecasted freezing level was at 7000 ft, and temperature at 6000ft was forecasted at plus 2 degrees C. I got two briefings and had current information on DUAT. What I neglected to take into account was that the MEA on my route of flight was 6000 (the altitude which I filed and still below the freezing level) and although on a westerly heading (even thousands) ATC in the area prefers to send departures up to 7,000. I took off with my student and one additional passenger, and got sent up to 7,000 as soon as I contacted approach. I studied the temperature probe and was relieved to see it still above freezing. We were about 500 feet above the layer and it was clear skies above. It was my first instrument x-country with a student and it was a beautiful flight to the coast. I relaxed a bit and took in the amazing sea of clouds below us and blue skies above. That's when things started turning against us. The tops started forming from a nice stratus layer to stratocumulus as we approached the coast range. The clouds marched higher and as we prepared to enter the first top I advised my student to focus on the attitude indicator and increase his scan rate.
The ice formed at an incredible rate. Large water droplets hit the windshield, ran for about 2-3 inches and then froze solid. I looked over at the temperature probe, which was now suddenly below freezing. We broke out of the first tops and looked ahead at even higher dark gray cumulus clouds. The first thing in my head was the numerous articles about not climbing out of freezing in GA aircraft because of the slow climb rates. We were already heavy with 3 passengers and full fuel, were picking up ice and all I could think about was ' Plus two degrees C at six'. I called approach, told them we had icing and asked for lower. They responded and gave me 6,000ft. We descended nervously down to 6,000 and almost instantly began to accumulate clear ice. The windshield was solid ice and the tire and strut were covered. I knew I had to get out of there, but as I called approach, I was thinking 'how did I let myself get into this, my student and passenger trusted me, what did I do wrong?' I quickly pushed those thoughts out of my head and put all my efforts into the task at hand: getting out of this situation, flying the plane and going home safe. I called and advised control of our situation and started back out of the icing conditions. I received a clearance to head back the opposite direction at 6,000 and at this point I was at nearly full power to maintain altitude and airspeed. I knew we had to go back through what we just came out of and I frantically searched with my student for a MOCA (lower altitude), unfortunately would not hit one for another 14 NM. We were over the mountains, accumulating clear ice, with no way to go lower. I was teaching an instrument ground school at the time and had just covered ATC vectors and obstruction clearance. I knew we were on radar so I quickly called approach, updated our situation and requested Minimum Vectoring Altitude. They came back and luckily go us down to 4,000 within a few minutes and I watched with great relief as the ice chunks started breaking off. As we touched down safely back home, I started second guessing myself, 'should I have climbed above the layer' or 'did I just violate every FAR in the book?' or 'how was I stupid enough to put other peoples lives at risk?' The only thing I knew for sure was that I was going to make sure that I figured out how to avoid putting my passengers or myself in that kind of situation again.
Since that time, I have spent a lot of time studying icing conditions, avoidance techniques and conditions that have high risks of encountering structural icing. According to AC 00-6A Aviation Weather, there is a greatly increased chance of icing over mountain ranges as the moisture is forced upslope and forms super cooled water droplets. As well, the two conditions necessary for ice to form are visible moisture and the temperature at the point where the moisture strikes the airframe to be 0 degrees C or colder. Aerodynamic cooling can lower the temperature of an airfoil to 0 even though the ambient temperature is a few degrees warmer. Severe icing is more likely near the tops of the clouds due to increased moisture levels.
The bottom line is always have an 'Out'. Foolishly I didn't have one. A MEA of 6000ft and forecasted freezing of 7,000ft is not a sufficient buffer. I learned a valuable lesson that day, it is not enough to simply use the forecasted weather or freezing levels, we must learn to anticipate the situations and conditions which will lead dangerous situations and act accordingly. A factor was my failure to see the big weather picture and my lack of 'local knowledge'. Luckily I am at a school were everyone feels comfortable to admit their mistakes, determine the factors involved and learn from them. I made deliberate and careful decisions that I thought were best and luckily turned out OK but it easily could have gone the other way. By far the most prudent decision would to have not put my passengers or myself in that kind of situation without a planned escape route.
At the end of the day, icing is where you find it, and if you do, you need a way out of it ahead of time.