My worst experience with ice so far was last year en route to Amsterdam in November. I was about 1500ft below a cloud, when freezing rain started. Windshield was covered in seconds and after a minute I couldn't maintain level flight with full power. I turned pitot heat on and descended (I had no other choice anyway) straight ahead as aileron control was marginal. It scared the s**t out of me. I just didn't think of supercooled rain. I've been stupid as this idea never crossed my mind.
Freezing rain is very rare but I got it once, on the way into Bournemouth. The temperature was about -1C and I descended really quickly and nothing really stuck. But I had to abandon the approach and go out over the sea.
I turned pitot heat on
Should have pitot heat on all the time, especially anytime below about +5C
Should have pitot heat on all the time, especially anytime below about +5C
There is a counter argument that if you only use it when you need it, it is more likely to be there for your use.
I tend to switch it on if the IAS stops making sense. It clears it within 5 seconds.
While I am on, I have had icing in quite powerful twins (Cessna 404, PA31-350 Chieftain, Aztec) where the amount of ice has meant that with full power and Vy (ie best rate of climb) I have still been going down at 200fpm. That is really nasty.
I tend to switch it on if the IAS stops making sense. It clears it within 5 seconds.
But you do always switch it on during takeoff and approach?
I had icing at OAT +4 when entered cumulus cloud - rime ice formed on wings after few seconds - a leyer of 2-3 cm. Turning on airframe deicing cleared it in 30 seconds but it's still amazes me how quickly it can form. So for me below +5 means pitot heat on.
But you do always switch it on during takeoff and approach?
Only if there is icing evident.
I had icing at OAT +4 when entered cumulus cloud - rime ice formed on wings after few seconds - a leyer of 2-3 cm. Turning on airframe deicing cleared it in 30 seconds but it's still amazes me how quickly it can form. So for me below +5 means pitot heat on.
I would suggest, Emir, that you check your OAT probe accuracy.
They are often way out.
I have two probes (one original and the other on the GTX330). I have checked both against a precision thermometer, accurate to 0.1C.
In IMC, I have never seen the slightest trace of ice anywhere on my plane at +1C or above, but it is completely normal to see at least a little in -1C or below.
At the speeds you and I fly at, the aerodynamic heating (or perhaps cooling, due to expansion, e.g. on the wing upper surface) is of the order of 1-2C max. So if you were getting ice accretion at an indicated +4C, I think the probe must be out.
GTX330 probes are often out by up to 5C, which is totally outrageous, and there is no official adjustment for it.
A good crude check if departing IFR from a reasonably well set-up airport is to cross-check the OAT gauge against the ATIS. If the OAT gauge reads 5 degrees above the ATIS, then at first approximation, deducting 5 degrees from the reading in flight and assuming that's about right is a fair guess.
G
I would suggest, Emir, that you check your OAT probe accuracy.
I meant +4 outside cumulus, inside was sub-zero. OAT probe checked at annual - correct.
For me pitot heat on on the runway, off after landing. Obviously check it is working via current draw.