I have one experience with icing which I remember quite clearly in my TB21 (only TKS prop anti-ice).
Coming to a close on an otherwise uneventful flight crossing Poland south to north, high above clouds over the Baltic sea and descending toward EKRK over Sweden as the sun set. Cloud layer below between 1500ft and 7000ft. I started the descend from FL180 over Bornholm and entered cloud at 7000 ft descending to 4000 ft per ATC.
Now almost dark, I saw what I thought initially was rain running back over the windscreen. Had turned on the TKS on the prop just to be sure.
Smooth ride with no turbulence but IMC in stratus, did not notice anything special. After a few minutes I looked to the left wing and to my surprise I saw a approx. 3 CM ice on the NAV light. Temp was about -4C. Immediately recognizing the potential danger I requested 3000ft due to ICE. 3000ft did not take me out of the ice which continued to accumulate. Now the airspeed had dropped from 150 IAS to 100 IAS. I requested 2000ft got 2100ft which was MSA. That took me to 0C and the Ice accumulation stopped, but the existing ice did not melt away either. Also with a headwind I had significantly reduced range and made only something like 80 KTS groundspeed even with increased power and fuel burn. I flew like this for 30 long minutes notifying tower of the ice problem and the did a highspeed half flap landing not to change the configuration much that had worked so far. Taxied to the hangar and sat in the aircraft for some minutes to reflect on my flight. Pushed the aircraft in the hangar and ice of the leading edges started falling off in bits to the hangar floor.
This event really got my attention to the potential danger of icing. I was quite close to declaring an emergency having to go below MSA if the accumulation had not stopped. I knew the terrain below was flat so it would have been possible to go down another 1000 ft but still not pleasant.
I was also really surprised how quickly the ice accumulated, and the airspeed speed came off. And to the fact how a little ice at the leading edge is really needed to dramatically increase drag. I went over my initial flight planning again and had not paid enough attention to the temperature’s vs MSA. There should have been a bigger spread. A few degrees can make a big difference. Another thing I took notice of was that plenty of airlines around in the air at the time and for them obviously the icing was not a problem, not even worth a mention on the radio. Served to me as a remainder just how much more carefull we as small plane GA pilots have to be because we don’t have the hardware to cope as easy (proper deice, automation, range/speed, reliability, pressurization, radar, co-pilot ect.). There is not much margin for error in GA flying unfortunately.
The turbocharged engine of the TB21 makes enroute flying over icing conditions possible most of the time which is a big advantage, but during the descend (potentially with a many hours old forecast) things can quickly go bad if you don’t have an escape. I also concluded that climbing back up from the 4000 to 7000ft even with the turbocharger would not have been realistic given the decreased airspeed and rate of accumulation. Also there would be no way around having to go through it again a short time later.
Lesson learned, without full de-ice protection (and potentially even with protection), be very cautious of having an escape route down to non-freezing conditions that is above MSA if flying in potential icing (cloud from freezing to -25C or so). Don’t expect to be able to outclimb icing in a GA aircraft. Turning back is potentially an option in some cases, but on longer A-B IFR flights and getting to the descend/arrival stage it would often be pointless. Not claiming to be expert in ice flying/conditions – just my personal experience.
Thanks for sharing, for A to B flights, I tend to be conservative on freezing altitude corridors and MSA for en-route while planing, these tend to have reliable forecasts compared to forecasting cloud base/tops and moisture but this still leave one with some risk regrading the conditions of the approach
Yes, if climbing is an option, one has to do it very early before getting into solid/moderate imc…
I guess once you started to see ice on the wings or airspeed drop it is probably too late to try any climb? the only way is down if MSA allow it otherwise a turn back (I don’t believe MSA-500ft is enough to melt anything)
Anyone has an external mounted device that measures outside dew point or moisture/humidity?
Ibra wrote:
I guess once you started to see ice on the wings or airspeed drop it is probably too late to try any climb?
Not necessarily. If you catch the ice accumulation early, while it is still small (say less than a 1 mm or so) you should be able to climb almost as usual.
Not necessarily. If you catch the ice accumulation early, while it is still small (say less than a 1 mm or so) you should be able to climb almost as usual.
I guess this i true in some cases. But rate of accumulation I think is a big player here. The icing I have gotten from other incidents was alot slower. Also consider that during an approach in IMC in a busy airspace there is a lot to do on comms and navigation. Do you see it right when i happens? I did not. I also think the accumulation can be alot quicker. This accident of a TBM is a good example, the airlines in the area accumulated 4-6 inches of ice in a few minutes.
Just watched this video.
This just shows that, in IMC and in the right temp range, you never know what icing you will get and where. Forecasts are of limited value. PIREPs of airliners getting mod ice would be very serious (because they have great ice protection) and while this TBM pilot would have had access to PIREPs (but seemingly either didn’t access them or disregarded them), they don’t exist in Europe, and ATC have no general awareness of weather such that they could proactively help aircraft.
I don’t know the temp range in which he collected that ice. If the G1000 display in that simulation is right, it shows -19C just at the point where he lost control
but he may have got a fair bit of it a lot earlier. I have seen -5C at FL160 and, as expected, lots of icing; the TKS was only just clearing it with it on max flow. It worked, which is the bottom line, but you would want an escape route to be exercised well before the TKS runs out.
How do you check that TKS is doing the job as expected? Visual look on the wings or just from flow rate & temps?
In the video the comment on the AP is interesting, if you push AP ON you will have more time to look at the wings for ice but you drop precious aerodynamic feedback while if you handfly with AP OFF you will rarely do a proper look outside,
I had the pax one day looking for ice specifically while I was handflying, he was not noticing as much as I saw or imagined, so my default assumption: if in cloud bellow freezing temp, then you are picking ice in the next 15min unless you prove otherwise but I never budgeted that could be as short as 1 or 2min?
Ibra wrote:
How do you check that TKS is doing the job as expected? Visual look on the wings
Yes. Just like you do with any deicing gear.
The largest giveaways for picking up ice when handflying on instruments are the the drop in airspeed and the gradual pitch up to maintain altitude. When flying on autopilot, the airspeed drop it the more noticeable of the two.
So whenever you find yourself trimming nose up repeatedly is the time to have a close look at the wings.
