Cross Country? Cold temps

[MrBrightside]

Ok so I am supposed to be doing my solo cross country tomorrow but I don't think this will be happening if it is anything like todays temperatures. Am I correct in thinking if I want to cruise at 2000ft and the OAT is -1 this would be a daft thing to do in a non anti-icing equipped aircraft?

cheers
MB

[Lister Noble]

Sorry ,lost in mists of senility,but doesn't humidity have a significance?

[ShyTorque]

Cold temperatures by themselves do not mean icing conditions. However, combine them with cloud or precipitation then icing conditions do exist and yes, avoid them!.

[Lister Noble]

SHYTorque,does that mean humidity?

[2high2fastagain]

Depends on the moisture content as Lister says. Water droplets landing on a subzero airframe isn't nice. Also, flying through clouds in subzero conditions is asking for trouble.

That said, my aircraft loves it when it's cold. Gin clear blue sky, nice cold dense air and low humidity - wonderful.
If you're in a 150/152, look for ice build up on the leading edge of the strut, that's where I notice it.

[MrBrightside]

The humidity level forecast is giving it to be 64%. The OAT at 2000ft today was -1. I am also in C152, never had any icing issues thus far (thank goodness).

[ShyTorque]

SHYTorque,does that mean humidity?

Yes but humidity isn't the full answer (note that TAFs or METARs don't state humidity).

It's possible to have low humidity and still get precipitiation and icing (depends on what air mass it's falling through).

[CanAmdelta1]

Just be sure to preflight pitot heat, and windshield defroster. Check fuel @ the belly drain and stay clear of clouds.

I T/O today @ below zero temps and landed this afternoon @ below zero temps. No problems but I stayed well away from clouds and cycled the carb heat a few times.

Enjoy your x/c and have a great time.

[Gertrude the Wombat]

If you're in a 150/152, look for ice build up on the leading edge of the strut, that's where I notice it

I was told in a 172 to look at the tyres, as white ice on black rubber would be more visible than white ice on white struts. So far I have managed not to fly in clouds below zero (or in rain; snow didn't seem to matter, apart from the difficulty of picking out where the grass runway was).

[Jan Olieslagers]

(note that TAFs or METARs don't state humidity).

Hm. Don't know about your place, but down here METAR's do give an indication of measured humidity. Which does not say everything, not by a long way, indeed. I particularly liked the M00 bit... what's the difference between 00 and M00?


FIR: EBBU


METAR
METAR EBBR 242250Z 25008KT 9999 FEW010 SCT012 03/01 Q1006 TEMPO BKN012=
METAR EBOS 242250Z 29012KT 9999 FEW018TCU SCT045 05/M00
METAR EBCI 242250Z 22006KT 6000 NSC Q1006 TEMPO 4500 SHRAGS= 00/M02 Q1006 NOSIG=

TAF FC
TAF EBCI 242004Z 2421/2506 23008KT 9999 SCT015 BKN040 PROB40 TEMPO 2421/2506 BKN012 PROB30 TEMPO 2502/2506 2000 -SHSNRA BKN004=

TAF FT
TAF EBBR 241720Z 2418/2524 23008KT 9999 SCT015 BKN040 PROB30 TEMPO 2418/2518 4500 SHRA SCT008 BKN012 PROB30 TEMPO 2502/2509 3000 -SHRASN BKN008 BECMG 2517/2520 04010KT =
TAF EBOS 241720Z 2418/2524 30013KT 9999 SCT015 SCT040 TEMPO 2418/2518 4500 SHRA BKN014CB BECMG 2515/2518 05017KT =

[ShyTorque]

Jan, Yes obviously dew point is given in the METAR (not the TAF though), so some idea of the relative humidity can be found from measurements taken at the airfield, but once airborne this is not the full answer for a pilot about icing conditions at cruise level.

Met Form 214 is of more help, but in practice a forecast temperature is often not quite accurate enough.

[Jan Olieslagers]

A forecast? Accurate enough? This must be a sample of the famous British tongue-in-cheek humour.

[Pilot DAR]

My personal record is a ferry flight in a C 172 from central Quebec, where the OAT at takeoff was -41C - no problem (though make sure you have lots of warm survival gear aboard).

Avoid any visible percipitation at close to freezing temperatures, but other than that, go and have fun, the plane won't mind. If you blunder into icing conditions in a 150/2, 172, or 180 series Cessna, you will most easily see ice accumulate on the upper portion of the windshield, which has the shape of the leading dege of the wing. If you see ANY accumulation there (or elsewhere on the aircraft), turn around, and get out. If there is a trace there, and no more accumulates, use caution for a slightly higher stall speed, but the plane will fly fine.

If you need pilot heat or winshield heat in the aforementioned model of Cessna, you are in icing way too deep, and have been careless - get out without delay!

In 34 winter seasons of flying VFR in the winter, it has never occurred to me that I really needed pilot heat on a single Cessna. I really think Cessna just put the heated pitot tube, beacuse it looked much more cool than the silly 1/4" tube pitot tubes found on the older Cessnas! While flying Aztecs IFR in icing, I can confirm that you want every single de icing system working perfectly!

Enjoy winter flying, though I'd rather enjoy it in -10C OAT than -1C

[jackx123]

Dew point

Caution if dew point spread is 3c or less.

Weather

[frangatang]

Just dont go into any cloud/rain and make sure you have a heater that works..unlike mine the other day.

[englishal]

SHYTorque,does that mean humidity

The key is "visible moisture"...i.e. clouds. 99% humidity won't cause icing. But icing is a whole topic on its own because at very cold temps ice can't form anyway.

Cold crisp clear days are great, you get better performance as the air is denser so more air molecules to flow into the carb or over the wings..

[Mariner9]

Guys, all this talk of moisture, temp/dewpoint spread, etc is confusing and completely unecessary information overload for a student about to undertake his first solo XC.

The simple answer is icing will not occur so long as you avoid clouds/mist/fog. Given that students have to avoid all 3 anyway this shouldn't be an issue. Enjoy the flight MrB

[24Carrot]

I particularly liked the M00 bit... what's the difference between 00 and M00?

The difference is both 00 and M00!

In the report, I would bet a computer program is rounding a small negative number like -.2 to M00, and a small positive number like +.2 to 00. The "C" "printf" function is easily formatted to produce -0 and 0, and it annoys accountants, so it is definitely the right way to do it.

[24Carrot]

The simple answer is icing will not occur so long as you avoid clouds/mist/fog. Given that students have to avoid all 3 anyway this shouldn't be an issue. Enjoy the flight MrB

Clouds are OK, (on the outside), its the wet stuff coming out of them you want to avoid. Otherwise, I agree.

Caveat: You can get frost forming outside cloud and precipitation, if the aircraft is colder than the moist air around it, eg descending from height. But this QXC is at 2,000ft so I cannot see that happening.

[Mariner9]

In the report, I would bet a computer program is rounding a small negative number like -.2 to M00, and a small positive number like +.2 to 00. The "C" "printf" function is easily formatted to produce -0 and 0, and it annoys accountants, so it is definitely the right way to do it.

Well that may be the answer in computer geek language (I've no idea whether it is ) but the simple answer is that an ICAO METAR rounds temperature to the nearest whole degree. "M00" signifies a temperature somewhere between -0.5C and (just below) 0, "00" signifies a temperature somewhere between 0 and (just below) +0.5C. Simple.