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]

Caution if dew point spread is 3c or less.

Weather (http://virtualskies.arc.nasa.gov/weather/4.html)

[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.:D

[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 MrBClouds 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 :ok:) 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.

[Jan Olieslagers]

[[ OFF - TOPIC ! ]]

Take a look at http://users.skynet.be/fa348739/image/gps_screen3.jpg and - knowing 't was all done in C - you'll see I'm enough of a geek to have some idea of printf and its "unexpected possibilities" aka non-documented features. Yes, yes. There was indeed no need to point out to me how the M00 came about, still it did look funny.

NB during that flight I had consumed neither alcohol nor any white powder nor an excess of coffee. I was merely learning not to blindly trust a magnetic compass, especially not in a cheapo microlight.

[24Carrot]

Jan, I never doubted you knew, and the M00 was funny.

All through my PPL my tracks all looked a little like that one. After a practice skills test, no less, my FI was pressed for time and flew back while de-briefing me. Looking at his track afterwards, it was a straight line. Until then, I had simply never imagined that could be possible, and my DI scan was, ahem, episodic.

Fortunately, it was just in time for the test.:ok:

Apologies, this is even more off-topic.:uhoh:

[Fuji Abound]

I am slightly bemused by the question and most of the answers.

If this is your qualifying cross country you have had it drumed into you to stay out of cloud. Moreover you will not be allowed to go on a day where there is a risk of your entering cloud (or exceptionally very moist air with below freezing conditions).

In reality it is extraordinarily rare to accumulate ice in clear air and even then the accumulation will be very slow. I have had it happen once at night in VMC (in fact very good VMC). I think it was a combination of rapidly cooling conditions (as night set in) precipitating water vapour and a cold soaked airframe. The aircraft was FIKI so it was not an issue and only a few short runs of fluid were required to deal with a problem that probably would not have been much of a problem even without FIKI.

In short if your instructor says it is good to go you will not have a problem as long as you stay out of cloud (which you know you must). That aside as others have said winter flying can be some of the best you can get and during cold spells like the current one the air more often than not is dry and clear.

Enjoy.

[ShyTorque]

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.

Never heard of rain ice then? Relatively (and thankfully) quite rare in UK but by far the most dangerous of all to light aircraft and helicopters.

Falling rain occurs from a relatively warm layer of air, lying above a cold sector. The precipitation becomes supercooled as it falls then finds your cold aircraft toodling along below as a freezing "nucleus".... nasty!

I cancelled two days flying here in UK last winter because of forecast rain ice, so did the other operator I was supposed to be working with on the same job.

A true story to consider: About 25 years ago, in winter, an RAF Wessex helicopter was practicing underslung load work at RAF Gutersloh in Germany, hovering and flying low level circuits on the south side of the airfield. Suddenly, rain began to fall and clear ice began to form on the aircraft. The pilot terminated the training and asked for permission to return to dispersal, a couple of minutes hover taxying away. It didn't make it. The rain/clear ice built up so quickly that it was soon over it's max gross weight. Combined with the ice on the blades destroying lift it would no longer fly and it basically landed itself.

There was a photo of the front of the aircraft on the RAF incident report - scary stuff. Clear ice was encrusted inches deep, all over the helicopter.

I was based at Gutersloh sometime afterwards. One winter's day we walked to lunch, using the back path from the hangar through a small pine wood. Moderate to heavy rain began to fall from an encroaching warm front and it froze as it hit the ground, or anything else. Half an hour later, very large branches were being ripped off those pine trees by the sheer weight of the ice on them. Walking back to the hangar by the same route was almost impossible and highly dangerous!

Needless to say, all RAF flying for the day was cancelled.

If the OP needs further advice, he must obviously take it from his supervising instructor on the day of the flight. :)

[Pace]

ShyTorque

Freezing rain - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Freezing_rain)

In all my flying I have only experienced icing out of visible moisture (cloud) a handful of times.

With an aircraft flying fast in a straight line I have found the area of such precipitation to be small.

Noted in the Helicopter incident and the ATR-72 crash featured in the above link both appear to have remained in a confined area the ATR in a hold.

A student is unlikely to be sent on a solo cross country where he is likely to inadvertantly enter cloud or on days with CB activity.

As in any icing get out fast and beware of days when you know you will carry it down to the ground.

Pace

[englishal]

I think that if one picks up ice then there has to be visible moisture around, and you just didn't see it.

Clouds are visible moisture, as is mist, haze, rain etc. I can imagine one could be flying VFR in conditions where the vis is really bad due to haze and a high humidity, and in actual fact this is visible moisture - half a degree colder and cloud / fog would form.

[lotusexige]

I do remember my own PPL cross country. It was about this time of year and we had had quite a bit of snow a few days earlier. I went off without a jacket and my though on the way back was how the hell I would stay warm if I had to force land for any reason.

[Mariner9]

Never heard of rain ice then?

Yep, rain from relatively warm air falling into a colder layer below. Not however the kind of weather where a solo stude would be sent off on his first solo xc in my view.

However, I should on reflection have included precipitation in my list.

Stay clear of cloud/mist/fog/precipitation and you will be fine regardless of a sub-zero OAT.

[Fuji Abound]

Never heard of rain ice then? Relatively (and thankfully) quite rare in UK but by far the most dangerous of all to light aircraft and helicopters.




Skytorque

I guess my point (and others) was we can dream up circumstances where icing might occur but we are discussing a QCX, the student is under the "supervision" of his instructor and flying over a short distance - he really doesnt and shouldnt need to worry about icing because his isntructor is not going to place him in a situation it is remotely likely to occur.

I think he wants reassurance, and I think we can reassure him, while agreeing that once he is on his own there are some useful observations in this thread of exceptional circumstances where ice could be an issue even in VMC.

[ShyTorque]

Mariner9,

I concur, see post #3.

IMHO, As far as airframe icing (and carb icing where appropriate) are concerned, they are both potentially very hazardous, so it's well worth knowing all one can about the subject. My future was once nearly decided for me by severe engine intake and airframe icing in a military jet at night. It's not something I'd like anyone else to experience.

Pace, we've disagreed about icing before, IIRC. The subject aircraft here are not fast and obviously are more badly affected and cannot often climb above the conditions; the longer the aircraft flies in the conditions, the more ice accretion is likely to be.

Fiji,

Yes, the OP can undoubtedly be reassured that his instructor will look after him and decide if a particular day is suitable, but from what I've seen and read, teaching of the real dangers of aircraft icing seems a rather neglected subject, at least in UK. I wonder why instructors aren't addressing this subject already, bearing in mind the recent weather forecasts? These questions about icing do come up with some regularity....

[Pilot DAR]

Falling rain occurs from a relatively warm layer of air, lying above a cold sector. The precipitation becomes supercooled as it falls then finds your cold aircraft toodling along below as a freezing "nucleus".... nasty!


Yes, this I have encountered, and it is very bad. It is visible as you approach it though, as it is percipitation.

I have hit it twice, thinking it was only rain. On both occasions, the engine stopped within seconds, as the air filter ices over (alternate air fixes that adequately) and the winshield ices over (which takes much longer to get running again!)

You'll have enough time, and good motivation, to do a 180 and get out. The airplane will remain suitably safe to fly, as long as you're gentle. The airframe ice you pick up is clear, which is not a lift destroying as rime. Don't linger there though!

Nothing in the foregoing is an endorsement of flying into any kind of freezing percipitaion, or other form of icing conditions, unless completely equipped and qualified. It is simply a reassurance that doing so is not immediately fatal, if you get right out, and keep your head about you.

Three times I have been falling out of control, because of airframe ice (I eventually learned - it was just more than one lesson). Once in a C150 at night over the mountains as a pre student passenger (more than one lesson there!), Once in a Twin Otter over the south of France, on a nice August day (yup, lesson there too), and the third time flying a very new Cessna 303, which was fully serviceable, and fully deiced for known icing. It was the AD forbidding flight into icing, in that model aircraft, which had not been properly placarded, and was thus unknown to me. (lesson on placarding and AD compliance there). Each time luck exceeded skill and judgement, so I'm here writing. A dear friend did much less well, and told me (12 hours after the crash) that in his Piper Dakota (235HP), with full power, the best he could manage was 70 knots, as he decended at 2200 FPM. He hit the trees that way. Unforecast icing conditions between layers at night - he had not been attuned to slowly degrading performance, which had given him lots of warning. He survivied - that time...

If you can't see what you're flying into, don't fly VFR into it. Use extra caution near freezing, and at night (and over the south of France). If you have good visibilty, and no percipitation, use good judgement, but go and enjoy a nice winter flight!

[IO540]

I came across freezing rain just once, flying into Bournemouth, through some TCUs. It was raining but the OAT gauge was showing -2C so I immediately descended a couple of thousand feet (told ATC and got on with it, mostly OCAS) and by the time I looked outside again, in VMC, the OAT was about +1 and I could not see any ice sticking.

Re structural icing in clear air, I have never had this but have had some kind of effect on the IAS i.e. the pitot tube. That's why one should have pitot heat on anytime below about +5.

Structural icing in IMC flight is a big subject. My take is that you will pick up ice eventually anytime the OAT is between 0 and say -10C (in non-convective cloud) and down to a lot colder in other types of cloud. But it is very random; you could fly for 30 mins in IMC and get no ice at all and then Bang and you get 5mm within seconds.

[Iwasoneonce]

Aircraft and engines love cold temperatures. Just stay away from visible moisture at those temperatures.

Freezing rain is not to be endured by any aircraft, certainly not, for t/o.

[Big Pistons Forever]

While getting icing in a cruise flight while flying clear of cloud is a theoretical possiblle a more practical consideration is getting the engine started when it is cold out. With ground temps at 0 deg C proper primeing is essential for a successfull start and the engine should be allowed to warm up at idle before the runup and takeoff is performed. Also carb fires at start up are more likely with cold temperatures so you should make sure you know the drill.

[I Love Flying]

Useful advice BPF. I had exactly that problem on my QXC - I couldn't start it initially and so my instructor had to for me (I was terrified of draining the battery by keep trying).

I then was petrified of not being able to start it subsequently after my first and second land-aways (I did indeed have trouble, but thankfully got it started each time).

I'm not wanting to worry the OP, but do make sure you are familiar with the best starting procedure on the aircraft that you will fly on the day.

Good luck!:ok:

[Pilot DAR]

Beautiful flights in 3 different aircraft today, in -22C. Clear and crisp, and you could see forever... Winter flying is great!

[spitfires rule]

Winter flying is great!
Winter walk arounds not so much :E