Cirrus SR20 Icing Encounters

by Philip Greenspun in January 2006

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My first encounter with ice in the Cirrus occurred in the summer of 2005 climbing out of Kugluktuk, Nunavut, on the Arctic Ocean in West-Central Canada. A system of bad weather with warnings about ice had passed overhead the evening before. It was above freezing on the ground, the terrain was flat, the ceiling was almost 2000', the tops were supposed to be around 6000'. I didn't like the idea of being in clouds that were below freezing, but figured that if I picked up ice, I could simply descend back towards the ocean

Starting at around 6000', the clouds looked thin above but I began to build up some ice on the leading edge of the SR20. The climb rate at Vy (95 knots or so) fell to 400' per minute (power lever firewalled for maximum prop speed), then 300 fpm, then 200 fpm. I was about to give up and go back down when I broke out at around 8000'. The plane had just a little protrusion of ice all along the leading edge, maybe extending half an inch from the plastic.

The plane was able to hold altitude and cruise speed was only reduced by perhaps 5 knots. The outside air temperature was about -10C and it took at least 30 minutes for the ice to sublime off.

Encounter Two

Here's a story that I wrote up for my Weblog (general audience, so I went light on the aviation jargon):
My friend Julian and I decided to do a little instrument training flight yesterday [January 4, 2006] in our Cirrus SR20.  The ceilings were perfect for practicing instrument approaches:  a layer of clouds from about 1000' above the ground to 3000' above sea level.  Wintertime instrument flying, however, requires being careful about icing.  It was below freezing on the ground.  The weather briefer told Julian that it was a beautiful day for practicing instrument approaches.  There were no airmets out for icing.  There were no pilot reports of icing.  There was supposedly an inversion with warmer air aloft.

After an hour on its electric block heater, we pulled the airplane out of the hangar and noticed some red brake fluid seeping out from an inspection panel on the inboard right wing.  Fortunately, I had some good karma built up with the mechanics at East Coast Aero Club and Rob Brigham zipped over to lie down on the ground, remove the panel, and tighten a hydraulic fitting.  Given the spate of Cirrus pilots who've managed to set their planes on fire with the brakes, and the fact that we'd never seen a leaking airplane braking system, we were a bit concerned about this.  But we pushed on the brakes and Rob didn't see any more fluid coming out.

We took off and did an uneventful ILS 11 approach into Worcester, going missed at 200' above the ground and climbing back up into the clouds for Lawrence.  We were directed to climb up to 5000'.  With the extra delay of getting the brakes tightened, it was beginning to get darker and colder.  We stepped down from 5000' to 2000' for the approach into Lawrence.  Julian was doing a bad job of holding altitude.  The plane should hold 105 knots and altitude with about 50 percent power.  He kept cranking up the power to almost 75 percent.  The plane began to vibrate a bit.  I had spent the first part of the flight checking the wings for ice every few minutes, but had become complacent.  We looked at the wings:  about 3/8" of ice.  Then the windshield began to ice up.  "Your airplane," said Julian, who had been flying up until now.  I was in the right (copilot's) seat, looking sideways at the instruments on the left side.  I asked Julian to engage the alternate air intake so that the engine wasn't trying to suck air through a potentially iced-over filtered inlet.  Our pitot heat was already on, which prevents the airspeed indicator and altimeter from becoming useless and freaking out pilots.

We reported the ice to the Lawrence Tower, but there was really nothing to do differently because we'd already been cleared for the approach and were planning to descend as soon as we intercepted the glide slope.  One thing that I remembered about icing is not to use the flaps, which increase the risk of a tailplane stall and a steep pitch down of the nose.  We didn't know what our stall speed would be with the new wing shape, so we kept our speed up at 100 knots until just short of the runway, then slowed down to 85 knots for a no-flap not-particularly-great landing.  Two things were in our favor during this landing:  (1) the ceilings remained high (1000'), so we didn't build up a lot of ice in the final minute or two and we didn't have to fly the approach down to minimums (200' above the ground), and (2) the runway at Lawrence is 5000' long, so you can have lots of extra airspeed and still stop well before reaching the end.

It was getting on toward 5:00 pm in Lawrence, but the guys at Eagle East Aviation were there.  They had done some maintenance work on my old Diamond Star, and I would always stop in whenever I was in Lawrence.  Tim Campbell, one of the owners, cleared some planes out of his maintenance hangar and helped us pull the Cirrus in over the icy ramp.  Then he cranked up one of the big overhead heaters and we went into the office to hang out and wait for the ice to melt off the wing leading edges and prop.  My primary instructor, Hal Spector, happened to be there.  When you do something unnecessary and stupid, why is it that your teacher must always be present?

After 30 minutes, we had the ice off and the ceilings were still more than 1000' and there was no precipitation.  Despite the darkness, we decided to go VFR under the clouds rather than IFR through the clouds back to Bedford (a 10-minute flight).  Lawrence was calling itself IFR, so we needed a "special VFR" clearance to get out (at night, this is available only to instrument-rated pilots with instrument-equipped planes).  I don't like to scud-run at night, but we wanted to get home (a dangerous tendency in itself) and we knew that we didn't like the clouds.  Visibility underneath the cloud layer was good and the trip back to Bedford was uneventful.  We put the plane away, checked for more brake fluid leaking (none found), and stopped at Jet Aviation to have some chocolate with the gals working the desk.

My previous encounters with ice were all in situations where it was warm at lower altitudes and those were altitudes where it was legal and safe to fly instruments, i.e., I could have at any time descended and melted the ice off the plane.  In this case, we were at all times close to airports with instrument approaches, but the surface temperature was below freezing and we would be forced to fly the plane all the way to the ground with whatever ice it had picked up.

So... what did we learn?  Don't fly a feeble non-deiced airplane through a cloud in the winter, even if the briefers say that no ice or precip is forecast, unless there are a few thousand feet of warm air over the ground.

Conclusion

Due to paranoia, a lot of deferred flights, and some luck, I have not encountered too much ice in my 1300+ hours of flying. Nonetheless, comparing the Cirrus SR20 to my old Diamond Star DA40, I have to say that I think the SR20's performance degrades more quickly.

If you are going to use a plane for point-to-point transportation, live anywhere other than Arizona, and hope to keep to a schedule, there is no substitute for an airplane that is approved by the FAA for flight into known icing (FIKI).


Text Copyright 2006 Philip Greenspun. Photo copyright 1992.
philg@mit.edu

Reader's Comments

My recent (October 2006) encounter with ice in my DA40:

http://www.flyingsummers.com/2006/10/07/excitement/

Autumn in Southern California. Still too warm on the ground to keep the canopy closed during taxi.

-- Colin Summers, October 13, 2006

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