Icing encounter

Submitted by on Mon, 01.04.2013 - 21:48

“Well, that’s not what I expected!”

Have you ever heard yourself mutter these words while flying?  I have! On numerous occasions I have heard and seen the “seasoned” pilot with 200 hours under his/her belt whip together a flight plan (based on guesstimate numbers) and thunder out the door to fly to a favorite airport, with the mindset of “get home-itis”.

 Weather can be a strange thing, as most of us have discovered on our travels. What is forecast might not be what we encounter, as I found out recently on a trip from CYWG (Winnipeg) to CYND (Gatineau) in a pressurized twin.  This encounter happened in winter on a domestic IFR flight plan.  The trip took us from CYWG to YQT (Thunder Bay VOR), YSB (Sudbury VOR), YYB (North Bay VOR) V316 YOW and home, with “no forecast icing along the route.” Sounds like a pretty straightforward route, right? Wrong.

 We learned that the route would take us out over Lake Superior for a bit and then back over land. Weather was forecast to be FEW 030 with tops to 050. Awesome, let’s go!

 En route we were getting PIREPS (although there really is not much air traffic between CYWG and CYYB).  No one was reporting anything significant, and Winnipeg Center was being very helpful in passing along visual observations of high level traffic (at FL180 and above). As we cruised along at 9,000 feet we noticed that the tops of the clouds were getting progressively higher and thicker. OK. We continued. Now we were over Lake Superior and the cloud tops were getting up to our flight level. OK, decision time. Climb up above. Good thought. The problem was that we were not pressurizing properly, a bad situation. We were limited to 10,000 feet and could get up to 13,000 feet for only 30 minutes, and were now in the cloud, picking up light icing. 

 As we continue along at 9,000 feet, just skimming the tops of the cloud, I watch the airspeed indicator start dropping fairly rapidly and eventually stop at 0. Oh my God, this is it! Why has this happened?We've had the pitot heat on during the trip! A look at the wing of our aircraft definitely shows signs of icing and glancing forward of the wing tells us that the pitot tubes have frozen over. This is unheard of, a dual pitot heat failure! What do we do now? 

 Well, the decision was made to start a descent down to get VFR and do the thing that no pilot wants to ever do: declare an emergency and squawk 7700. Winnipeg Center was in receipt of our transmission and asked all the information such as “souls on board, fuel on board as well as any dangerous goods.”  

 We continue down, flying partial panel and using ground speed as our saving grace. Now the big decision. Once we get out of the ice what then? The aircraft is flying OK with the ice on it, now in a descent with lots of air going over the wings, but what will happen when we level off in cruise? The controls are getting a bit sloppy but still controllable. OK, where are we going to? Let’s check Dryden.  The AWOS is advertising IFR. Let’s check Marathon. IFR (all these were forecasted to be VFR with scattered cloud during our flight.). OK, let’s check CYQT (Thunder Bay 140nm away).  Advertising BKN at 050. Perfect. Let’s go! GPS direct!

 As we proceeded to CYQT we arrived at our MEA and were still in the cloud. Down to MOCA we went. At that point we were 2700’ASL and the MOCA was 2500’ASL. At 2600’ASL we picked up the ground but visibility was poor. Not just from the fact that our windshield was completely covered in ice but also from the fact that there was light to moderate snow falling. As we leveled off we were OK. The aircraft was sluggish, but we could maintain altitude and a consistent 160kts ground speed. 

 We tuned the ATIS in CYQT and they were now advertising 1200’ overcast in light snow. What could have changed the weather so drastically? A slight wind shift from the south west, apparently, which caused an on-shore flow of moist air over cold land: the lake effect. For a hundred nautical miles, all I could hear was Mike Masek’s voice, talking about lake effect.

 The controller advised us that a Porter flight which had just landed in YQT was visual just after passing the Final Approach Fix (FAF) on the ILS 07. From the direction we were coming, the controller advised us that we would probably have to do a full procedure for the ILS 07. A quick answer followed:  “UNABLE”. (As pilots, you always want to accommodate ATC, but in an emergency situation do not accept something that you are uncomfortable with, especially if you are iced up like we were.  They are there to service the aircraft and pilots, not the other way around.) We received vectors to final and, sure enough, there was a runway in front of us which we could only see from either side of the aircraft. 

 We landed and taxied off the active and requested to shut down there for a few minutes while we examined the aircraft and cleared the windshield with a credit card.

 All ended well, this time.  But after looking at Nav Canada’s website and reading about flight around that region, it soon became clear that this is not uncommon. 

 So if you are ever taking a trip to an area of the country that you are not familiar with, be sure to read up on the weather patterns and peculiarities associated with it. It will save you stress and quite possibly your life, one day.

 Mark Braithwaite

Assistant Chief Flight Instructor

Rockcliffe Flying Club