LESSONS MY COMANCHE TAUGHT ME
ICE IS NOT JUST FOR WINTER
by Glenn Plymate, ex-ICS 02658
November to March! This is when us cautious Comanche aviators north of the Mason-Dixon line think twice before venturing aloft into clouds where ice might be lurking. And for good reason. The Comanche wing, designed to fly fast, is probably as bad as there is for hauling ice. Mother Nature can turn Mr. Piper's beautiful laminar flow airplane into a lumbering ice wagon in an instant with just a swish of her frosty wand.
How do I know a Comanche makes a rotten hauler of frigid freight? Because, even with my wary eye and extra wintertime caution, I've been caught more than once in my red-wing 1959 PA-24-250. Each time, it's been IFR, in wet clouds, but not always in the wintertime. In fact, only one of my Comanche ice encounters has been in that four-month season we think of as winter.
"No ice in the forecast"
Great news; the words I love to hear. It was on a day in early November. We'd filed an IFR flight plan and were cleared to maintain 11,000 feet for the first leg of a three-hour flight to Oakland, California.. We were in clouds headed south between Eugene, Oregon and Medford. Tops were expected to be 13,500 (according to pilot reports over Medford) and there were no reports of icing.
South of Eugene, oxygen on and at cruise altitude, it was not supposed to happen but ice began forming on our leading edges. Pitot heat was already on. I immediately advised Center and asked for higher. We were given 13,000 and began our climb. It was slow going since we were picking up more ice on the way. At 13,000 we were still solidly imbedded in clouds and there was no sign of tops. It was hard to tell but I thought we were still getting ice, so asked again for a higher altitude. I had already considered my options: (1) abort the trip, turn around, and head back toward lower terrain and warm air, or (2) climb above the wet clouds and continue on course.
Center cleared us to 15,000. We started up again but we no longer had our sprightly Comanche with its 20,000 foot service ceiling; we had an experimental airplane with an unknown airfoil and who knows what for gross weight, c.g., or stall speed. The controls had to be handled very deftly to avoid too high an angle of attack lest we risk getting ice on the bottom of the wing to slow us down even more. We passed 13,500. No tops! Where were they? I asked center again for the tops report. Same thing: 13,500, but over Medford, not where we were … 50 miles north. At 14,500 we started to see light spots to our left. I told Center I was deviating east of course as I wallowed around looking for those tops. By this time Center must have sensed the difficulty we were having, as the controller cleared me to, "do anything you have to do to stay in the air." I was very touched by the compassion in his voice; and it was a relief to know the people on the ground had such an interest in helping us along. We finally clawed our way to 15,000 after avoiding the darkest, most menacing portions of the clouds but we were still solid IFR. Several long, long minutes later, going about 120 mph, we finally chugged out of the clouds, on top, in brilliant sunshine, about 20 miles north of Medford.
We still had lots of ice. Even under a bright sun, it melts very slowly when the temperature is below freezing. But those red wings are so pretty trimmed with a white leading edge. The ice lingered for a good half hour as we continued on to Oakland and an uneventful culmination of that memorable experience.
Better luck next time?
What went wrong? First, the tops report over Medford was not a report of tops between Eugene and Medford. The tops to the north could be expected to be higher ... and they were. They sloped up from the south to well above where we could climb to. At least, heading south was better than heading north into a higher cloud layer. Second, ice in clouds can be anticipated by reviewing the temperatures included in the winds aloft forecast. For example, if the forecast temperature at 9,000 feet is +1, and at 12,000 feet, -3, you can expect the freezing level to be around 10,000 feet. Be alert, and have your pitot heat on if you are in or near any clouds when the temperature is near freezing.
As we came out of the clouds with our leading edges coated with ice, I was prepared for the possibility of a sudden change in flight characteristics like we'd had on a flight one day in May, headed south between North Bend (OR) and Crescent City (CA) over the coastal mountains. Similar scenario: Cloud tops sloped up to the north from the south; but the freezing level was lower, about 6,500 feet. We were cleared at 7,000. We began getting ice. Fast! I asked Center for higher. There was a "stand by" delay. By the time a clearance would have been available, I had too much ice, unable to climb. So, I asked for lower. No dice! It was not available since I was already at the minimum enroute altitude for the sector. I still had some options: (1) do a 180; (2) continue on; or (3), if unable to maintain altitude, advise Center I was turning right, and descend over the ocean to get below the clouds and into warmer air.
But we kept going, knowing the weather south was clear. We were going pretty slow by the time we came out of the clouds but we were in bright sunshine, with the sun on the right side of the airplane and the temperature still below freezing.
As the sun worked on the ice, we could see it getting slushy on the right wing but the left wing was still cold, icy, and firm. The ice began to slip off the right wing, when, all of a sudden – Whoosh! -- ALL the ice on that wing let go!
Instantly -- we had more lift on the right side. A great way to start a left snap roll!
Too bad there was no one around to watch our little air show.
We went from wings horizontal -- to wings vertical -- to wings horizontal – all in the blink of an eye! A very impressive lesson in what ice can do to your airfoil!
It was several minutes of holding right aileron before our lift was balanced once again by iceless wings on both sides.
Stay alert … and keep an Ace in the hole!
I've learned that ice is not just for winter; it can be a problem any time of the year. My log book shows non-winter icing encounters in May(3), June(1), July(1), September(1), and each was an experience ... a story to tell. Wintertime encounters have been the exception; perhaps because I'm more wary when the days are short and the temperatures cold. But you have to be on the alert at all times. Review temperature aloft forecasts before venturing into clouds; always ask for pilot reports on icing; and always have a way out ... every time!