Flight Level 180
We had just finished an amazing trip of business, family and food, typical to a Vegas anything trip.
We were level at FL180 on our flight home from Las Vegas for about 1.2 hours when we saw these out the window.
I will never again look at clouds like that without the feeling of respect. These clouds looked fairly typical to me but at the time I only had about .5 hours as an official ice pilot time logged. That of course is tongue and cheek about flying in the ice so much you end up logging it. I was flying a, new to me 1977 Cessna 414. I had been flying with a mentor pilot for the previous 40 hours and we had put the plane and myself thru it’s paces but nothing like I was about to experience.
As we continued into the cloud layer we started picking up light mixed icing. At first it was somewhat cool seeing the boots blow off the ice and watching in amazement as the front windows covered with a thick ice coating. I contacted ATC and gave a pirep letting them know we had light mixed ice and we were good at the moment.
10 Minutes later I was becoming all too aware of my boot cycle as it went from approx every 5 min down to about every 1.5 min. At this point I should have known, but was lacking the experience to climb or descend. I continued my journey until the 30 second cycle on the boots was no longer adequate to clear the ice off the 414.
Me: “Center, we need immediate clearance to vacate FL180 for severe icing”
Center: “What your your intentions”?
Me: “I would like to climb FL210”
I assumed I would be out of the ice, after all I was told that ice is almost never very thick. Starting the climb I had to start increasing power and the plane was only able to pull about 250fpm for the climb. At FL200 I was still not out of the ice and the plane was approaching blueline.
Me: “I need clearance for as low as you can let me go” –
ATC: “Cleared to 10,000ft.”
I pointed the nose over, blowing the boots every 30 seconds and headed for 10,000 ft. At 10,700 we came out of the clouds and the plane was a block of ice. I was shocked at the amount of ice on the tip tanks, tail section, etc.
As we continued to fly with clean leading edges, the rest of the plane started to melt and the ice started to break away. We could hear large block and chunks of ice coming off the fuselage, tail, wings, tanks, spinners, antennas, etc. The sound was like someone shooting the plane with a shot gun and for the first few times was a bit unnerving. This process took approx 20 min to shed the ice off the entire plane before we proceeded to head home on the final leg of our trip. That day Sept 29th 2013 at approx 3:00pm was a day that changed my flight planning forever!
Icing has to be one of the scariest things about flying short of losing your engine in a single engine over the mountains at night. There is no doubt both can kill you. However, for icing you have a few tools to use to help you plan your trip with the ability to know more about where you might encounter icing.
Let me first clarify that I was and still am a detailed flight planner. I have never jumped in a plane without a detailed and thorough plan. I typically spend hours researching weather charts, looking at area forecasts, digging into all the PIREPS, AIRMETS and SIGMETS along my route of flight as well as getting a solid briefing. I calculate every aspect of my XC options, alternates, outs along with payloads, fuel options, etc. So in retrospect I actually had covered all my bases with one exception.
Skew-T (p) log, are rarely taught outside of advanced aviation weather training can be a real powerful tool for you as an IFR pilot. This chart shows a very interesting data point that I had not previously known about. The connection of the two points.
Lets’ break down the chart. You can learn more about reading Skew-T (p) log diagrams here
Far left side (Isobar lines) – equal pressure.
Red Line on the left (dewpoint)
Red line on the right (Temperature Curve)
When the Dewpoint line and the Temperature Curve line meet, at that pressure (isobar) you would expect to see ice if the temperature (bottom axis is 4c or below. You can see on this chart is is about -12c.
Granted there are all kinds of lines on this chart including lapse rate, dry, moist, super, etc. But, just a quick looks would show you that around 580 isobar (14,600) is where you see the intersect. It happened that 16,000-20,000 was the sweet spot for the clouds and ice in the particular area I was in. Keep in mind this chart is not a perfect depiction. It’s a snapshot from weather balloons released from fixed locations that may or may not be along your route of travel and at times that may not be exact to your travel.
[divider]More Skew-T (p) Log Data[/divider]
Lets take another look at a Skew-T (p) log from AvWxWorkshop.
The sounding analysis (Above) from the RUC for Nashville clearly shows (see below) that a fairly deep saturated layer from 5,000 feet down to 1,000 feet was present.
This sounding analysis is very similar to what was forecast the night before with the lowest freezing level around 3,000 feet with saturated conditions to about 1,000 feet MSL. Even without a pilot report, there are clear indications of the potential for clear icing from 1,000 feet through 3,000 feet.
None of the standard icing products such as AIRMET Zulu and CIP do an adequate job showing the potential for structural icing on a descent into Nashville. The advantage of using the Skew-T log (p) diagram is that it will show a continuous profile of both the temperature and dewpoint giving you the best opportunity to identify hazardous weather, including icing.
I know that I was fortunate to have experience teach me a lesson and let me ask the questions once I got back on the ground. It’s too often situations like that lead to accidents and death and I’m very thankful that we made it out safe and sound with experience notched in my belt.
Pictures of later icing encounters on approaches which were totally normal and the plane handled very well.