Icing and sublimation

On Friday, when I was flying back from Fredericton to Ottawa, I picked up a splash of clear ice in a cloud top over Maine.

I use my Outside Air Temperature (OAT) probe as an early ice detector, since thinner surfaces collect ice before fatter ones (like a wing). Here’s what I saw:


I immediately climbed higher, even though the air was colder (-12°c), because I knew that the sunlight would cause the ice to sublimate, passing straight from frozen to vapour without ever thawing. These pictures show what happened over the next half hour:





Sublimation is much slower than thawing, so if you have the choice to descend into warmer air, do it. When there’s just a trace, though, and you can get safely above the clouds, sublimation isn’t a bad option.

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Four digits


Earlier this month, after passing another 2-year IFR flight assessment, I discovered that my total flight time added up to 999.9 hours. This morning, as soon as the wheels left the runway, I finally joined the four-digit club, a couple of years later than planned, but still with a smile on my face.

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Diagnose this: rough engine on approach

Airplane: Piper Warrior II (O-320 engine)
Airport: CYGK (north shore of Lake Ontario
Time: afternoon
Weather: CAVU; 15°c OAT; prevailing westerly winds, but airport in local light lake breeze from the south

About five miles back from landing today, I noticed the engine running rough whenever I reduced power — it was fine above 2,200 RPM, but started vibrating at any lower setting, enough that the plane (carbureted) shook noticeably. I accepted the vibration, landed, and taxied to the ramp, with the plane still shaking. I switched mags while taxiing and tried different mixture settings, with no difference. When I tried to shut down with the mixture lever, the engine kept running (even at full lean), and I had to stop it with the mags.

Your diagnosis? (I’ll post the answer in a day or two).

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Personal IFR minima

One big source of stress around flying is indecision: if all things (people, weather, and equipment) are perfect, it’s an easy choice to fly; if something’s clearly awful (you have the flu, there’s freezing rain, the plane has a major mechanical problem), it’s an easy choice not to fly. If it’s somewhere in the middle, the stress starts — is it really worth letting yourself or other people down because of a forecast for a chance of X or Y that probably won’t happen?

To reduce that stress, I’ve long wanted to put together sets of personal weather minima. Here’s my first draft, for IFR flight in a Piper Cherokee.

Personal day IFR minima

  • Destination forecast meets standard alternate minima for ceiling or visibility, or a nearby larger airport does.
  • Freezing level forecast at least 2,000 feet above MEA.
  • No worse than scattered CB forecast along route.
  • No severe turbulence forecast along route (at my altitudes).
  • Always within 60 minutes of a usable diversion airport.

Personal night IFR minima

  • All day IFR minima.
  • Freezing level forecast at least 4,000 feet above MOCA.
  • No worse than isolated CB, TCU, or ACC forecast along route.
  • Always within 45 minutes of a usable diversion airport.
  • No CB or TCU forecast at destination.

I don’t want the minima to be so lengthy that I ignore them, so strict that I start making exceptions, or so lax that they don’t really help me make the fly/no-fly decision. I’m very interested in feedback from other pilots — please let me know what you think, good or bad.

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Pilot advice on OurAirports?

I’m still hoping to do a responsive redesign on OurAirports if I can wedge some free time into my schedule. I’ve also been thinking about how to make the site less CRUDy (browsing lists of things) and more generally useful (helping people do stuff).


Yesterday, I was playing around with a new METAR parsing class, and I realized how easy it would be to start offering advice to people based on the weather and other information. The advice would be fairly generic, and couldn’t (in most cases) take into account local special conditions, but there’s still a lot you can do with a small amount of information:

  1. You can mark the conditions generically as VFR, MVFR, IFR, or LIFR.
  2. You can warn pilots to keep an eye open for icing (freezing precip or low ceiling in low temps), wind shear (big difference between winds aloft and surface winds), strong winds, unforecast fog (small temp/dewpoint spread), unforecast convective activity (high dewpoint), etc.
  3. You can warn passengers to check for weather-related delays based on some of the above, combined with how busy the airport is.
  4. You can tell passengers whether there might be a bumpy ride on approach or climb-out
  5. You can check the available runways to see if there will be strong crosswinds.
  6. In a fancy implementation, you could look at the surrounding DEM and suggest whether the ceiling might be low enough to hide surrounding hills (etc.), even if conditions are otherwise VFR.

Is this a good idea?

Does this sound interesting to you as a private pilot, commercial pilot, or airline passenger? It wouldn’t be meant to replace real pilot weather briefings, but rather to give you a single-glance overview on your computer or smartphone screen before you start the real prep. For passengers, it would give them an idea of when to expect problems at airports, before the delays start showing up on the big screens.


I was even thinking of creating two personalities, an Airport Old-Timer in a rocking chair on the FBO porch (pilot advice) and the Frequently Flyer in a business suit (passenger advice), but that feels a bit too much like resurrecting Clippy.

How else might I take OurAirports past a data repository to something genuinely useful to pilots and airline passengers? Advice is welcome, even from talking paperclips.

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Link: Private pilots pushed out of hangars at Toronto island airport


Porter contends that the Q400 turboprop planes it flies qualify the airline’s activities as general aviation.

I love Porter as an airline, but that statement (if accurately reported by Macleans) is BS of the worst kind. Porter is trying to claim that it’s a general-aviation operation because the tripartite agreement governing CYTZ calls for the preservation of GA at the airport, and Porter has been working to squeeze out resident GA (though they’re great with transients).

Porter knows perfectly well, though, that it doesn’t operate under the sections of the CARs (Canada) or the FARs (US) that govern GA, but is regulated as an airline, just like Air Canada or Westjet.  Let’s hope the Toronto Port Authority isn’t as stupid as Porter assumes.

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Less noise in the cockpit

I took this morning off and went for my first flight of 2013. Something was wrong with my Bose headset or its batteries, so I had to do without noise cancellation, but it was a wonderfully-quiet flight in a different way.

Toys or no toys?

Normally, I mount a Garmin 696 portable GPS on my yoke, with a full-colour moving map, terrain and obstacle alerts, live satellite weather, nearby traffic alerts fed from a Zaon XRX, and even XM satellite radio. For a long cross-country flight, that stuff is very helpful, letting me see and plan for what’s happening 200 miles ahead and listen to the BBC to kill the long hours. It does, however, require a yoke mount and a complex series of power, antenna, and audio wires threaded carefully out of the way around the cockpit.

I had planned to reinstall all of that before flying (I removed it for the plane’s annual last month), but then I looked at the beautiful, simple panel with its analog “steam” gauges, looked up at the blue sky, and asked myself “why bother?”

I took off and followed frozen rivers around Eastern Ontario at 2,000 ft. I started without the map, but pulled it out for fun to identify towns and villages whose names I didn’t know (for the bigger ones, I just read the water towers).

After 2 1/2 months without flying, my pre-flight skills were a bit rusty (I forgot to remove the pitot cover, and had to shut down and restart on the taxiway), but my stick-and-rudder skills were surprisingly good — the altimeter seemed to stay pegged on 2,000 ft even when I was distracted enjoying the scenery, wind-correction angles set themselves, etc.

Too much information?

I don’t think I suddenly became a better pilot, especially after almost a full season away from the cockpit. My only conclusion is that I was less distracted. I’ve never been one of those fools who flies head-down playing with the toys instead of looking out the window, but still, every piece of information available to me is something my brain has to process, whether I’m consciously focussing on it or not. Without the GPS hurling groundspeed and heading at me, without the traffic system telling me there was another plane 2 miles away, without pictures of airports and airspace scrolling across a colour screen a couple of feet from my face, I simply didn’t have as much to think about.

Modern avionics are great, and in many situations — complex airspace, IFR, etc. — they actually lower the workload. But for an easy VFR flight in familiar airspace, I think that leaving it packed away made me a better pilot.

Further reading: Eight years ago, as a fairly new pilot, I posted about something similar for the instrument scan in Analog Flying. I strongly suspect that’s the best article — and possibly the only truly useful one — that I’ve posted in this blog.

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