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Icing (merged threads)

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.

EGBE - Coventry

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

Administrator
Shoreham EGKA, United Kingdom

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.

EGKB Biggin Hill

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.

LDZA LDVA, Croatia

But you do always switch it on during takeoff and approach?

Only if there is icing evident.

EGKB Biggin Hill

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.

Administrator
Shoreham EGKA, United Kingdom

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

Boffin at large
Various, southern UK.

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.

LDZA LDVA, Croatia

For me pitot heat on on the runway, off after landing. Obviously check it is working via current draw.

EGTK Oxford
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