Frost

[neilgeddes]

Hello, it's been a while since I took my Met exam and I'm trying to refresh my understanding of frost and it's effect on flying VFR. On days like this weekend, where there's frost forecast to say 11am, what's the implication of (air and ground) frost for flying a plane hangared overnight? Maybe I'd like to get the plane out around 9am, do my checks, fuel up and then depart an hour later. If I plan to avoid flying in cloud what should I be aware of regarding frost during preflight checks and departure? Thanks for your help.

[mm_flynn]

Make sure there is no frost on flying surfaces (wings and control surfaces).

Also, wear warm clothes make sure windshield defrost and cabin heat work.

Finally don't scrape the frost off and use care with anything you spray to make sure it is safe on aluminium and acrylic (or whatever your aircraft is made of)

[englishal]

Just make sure you have removed any frost from the wings AND TAIL before you go, and then don't worry about it.

[IO540]

Incidentally, is there a device which is say butane gas powered and which generates warm water? Using warm water is a good way to defrost a plane, without corrosive chemicals. Cold water (from a bucket) just freezes immediately....

[24Carrot]

Actually, I don't think warm water helps enough to be worth the extra hassle.

Every gram of ordinary water at say 5 degrees that gets frozen warms the wing by 85 calories (5 degs down to zero, then the 80 calories latent heat of freezing).

Using warm water at say 55 degrees raises that to 135 calories, which is 60% better. Or you could just use 60% more of the cold water!

[Say again s l o w l y]

Using water to defrost an aircraft is one of the more silly things I have ever read on here.

Just have a think why.

[IO540]

Well, it can re-freeze. That's why one would need a lot of it.

The other thing is that overly warm water can crack windows.

[Say again s l o w l y]

So, what are the problems with liquids freezing on aircraft? The answer "use more water" is neither correct nor sensible.

If I saw someone "defrosting" their aircraft using plain water of any temperature, then I'd hit them with sticks until they went and did some research into why it's such a bloody stupid idea.

Seriously, I cannot believe that people can even consider using water to defrost a cold airframe and then go flying into even colder temperatures...

[Jan Olieslagers]

Well, excuse my ignorance but I'd be glad for some explanations. "It is clean daft so you just don't do it" would have done in the bad old days of usenet; on the internet forums of the 21st century some explanation may be demanded.

For myself, I do see the restrictions that
-) as already said, thermoshock is a danger to be avoided, and transparencies are particularly prone to it so care would be needed;
-) an abundance of water might well leave remains in hidden hooks, that might refreeze, increasing weight, possibly beyond margins. So one would want to apply water sparingly - another reason to have it as warm as practical - and dry it off after application.

Agree on these two?
More arguments?

I'll admit I've never been in the situation, always having been able to rely on people more competent than myself, mostly instructors. Also, up till now I've only flown well-hangared club planes. So I'll be glad to learn, just wondering.

[24Carrot]

To be honest, I never thought further ahead than how I would feel looking at a wing covered in ice (and only marginally less ice if I used warm water), that minutes earlier had only been covered in frost. And how would I get the ice off.

If we are doing the guessing game:
It could be hard to dry the aircraft, and in cold conditions, the water wouldn't just evaporate, it would probably go somewhere you didn't want it to, and then freeze, possibly locking a control. Or contaminate a surface. The weight increase would not be an issue, but the lift/drag changes could be.

[Pilot DAR]

Applying water to a cold aircraft for the purpose of defrosting an aircraft it is a really bad idea. Letting alone all the aspects of it refreezing on the lifting surfaces, and being very much more difficult to remove, than the frost was to begin with, it will flow into, and freeze all kinds of other airframe parts - including controls system components.

There are proper deicing fluids for defrosting aircraft, or put it in a heated hanger if available. As a last, and least effective means, a soft brush or broom, but this is a lot of work, not entirely effective, and does put wear and tear on the painted surfaces. Best to prevent the frost in the first place, hanger the plane, or as a last resort, put on wing covers the night before.

[Say again s l o w l y]

I'm trying to let people work it out for themselves. It's an old instructor trick that helps to ensure people actually think about a problem rather than just parroting an answer without giving it some thought.

Seriously, it's not hard to work out why this is a bad idea. Or has no-one ever read that chapter in the text books?

Why do commercial aircraft use de-icing fluid rather than water for example? Especially given the cost?

[24Carrot]

I thought they did use water. Mixed it with anti-freeze though, to stop icing up the wings.

[Jan Olieslagers]

@SAS: The answer to your last point could simply be "to increase the bill".
Your other arguments I won't even try to answer - being a tutor myself, though in a quite different trade. If you prefer playing the Tibetan sage, why visit a forum at all? And yes, I did have consulted my ground school text books before asking.

[IO540]

I don't think the case is as clear cut.

With my TB20, if you were to pour water all over it, nearly all of it will run straight off. No pools of water will form anywhere. All that will be left will be a few droplets, and they can be wiped off.

On the TB20, no significant water enters the control surfaces and certainly none can enter where it might block control linkages.

Obviously this is not going to work in -20C but we don't get that in the UK - not when one might be flying anyway. Since 1969, the coldest I have seen on the south coast was about -8C. The coldest I have departed in, or tried to, in the UK, was -2C and water copes with that perfectly.

Except on the wing upper surfaces IF the fuel tanks are full, in which case it just freezes into ice, due to the huge mass of the -2C fuel the other side of the aluminium sheet. That is the main reason I have found water to be useless.

I have departed from Germany in about -6C but the aircraft had been put in a hangar prior to that so it was clean.

A hangar, never mind a heated one, available to a visiting aircraft, is almost never available in the UK.

[Say again s l o w l y]

I washed my car yesterday. I used hot water and then hosed it off. I then got a chamois out to dry it. The car iced up whilst I was doing it. Given that it was only just freezing and the car had been in the heated garage until I started to wash it. How sensible do you think it is to use plain water in sub zero temperatures as a de-icer?

No water can possibly enter control linkages on a TB20? Want to bet your life on that IO?

Jan. I've been banging the drum for flying instructors on this site for over 10 years. I am still stunned by the lack of knowledge that licensed pilots come out with. I've given up simply telling people what to do, as the same stupid questions come up time and time again.
So people should do a bit of brain work before coming up with something so ununtterably stupid as to make me wonder if they've suffered a massive blow to the head recently.

Whilst some people say "There is no such thing as a stupid question, just a stupid answer" that I'm afraid is nonsense. People should always ask if they are unsure about something, but they should also be self-critical and try and work out from basic principles themselves what they aren't understanding.

The thought of solely using water as a de-icer is to me as stupid kicking a lion in the pods and then being surprised when he bites your head off.

[ShyTorque]

If everyone was as clever as an instructor, he'd soon be out of a job... :E

[Say again s l o w l y]

Exactly. It's because so many instructors are so smart that we keep getting daft questions!

Err... Hmm... :}

[Blues&twos]

Melted frost/snow/ice re-freezing contributed to the Air Florida crash into the Potomac River in 1982 (admittedly, among other things!), according to the investigation.....

[mm_flynn]

For frost, I found the single best investment I have ever made was to go to B&Q, spend £10 on a small garden sprayer, then go to the airport and spend £15 with the tower on some deice fluid mix.

5 minutes with the sprayer and a towel (for slightly thicker bits)- all frost gone (makes winter flying so much nicer). Worked for me all last winter and I had enough left over to use it as an instant windshield de-ice this year (before I buy a fresh batch).

[Vanpilot]

10 points to the man above......easy method that works well on most planes. Have even used this method with the same B and Q de-icer. Takes a while but you can be assured you have de-iced properly and that you even have some hold over against further frost. ( read the label ). Use your fingers to check you have got it all off and if you have a hi tail, don't just spray it over the top and hope it does the job....get a ladder.
Give your self that extra time before your flight to complete these tasks without having to rush.

Safe flying guys

[24Carrot]

This:
Aircraft Icing Training - Courses (http://aircrafticing.grc.nasa.gov/courses.html)
has a lot of good stuff.

[Say again s l o w l y]

It's good to see some some sensible stuff on here at last!

The ONLY fluids that should be used for de-icing are the approved Type I to IV fluids. They should be applied in the manner that the manufacturer recommends.

Never ever use anything else. Especially not plain bl**dy water!

Now back to the original question.

Hello, it's been a while since I took my Met exam and I'm trying to refresh my understanding of frost and it's effect on flying VFR. On days like this weekend, where there's frost forecast to say 11am, what's the implication of (air and ground) frost for flying a plane hangared overnight? Maybe I'd like to get the plane out around 9am, do my checks, fuel up and then depart an hour later. If I plan to avoid flying in cloud what should I be aware of regarding frost during preflight checks and departure? Thanks for your help.

Why not get the aircraft fuelled the night before, do your preflight checks in the hangar, then just pull it out and go if you are worried about the aircraft icing up whilst parked outside.

Don't mess around with icing. If it's below freezing on the ground, then do everything you can to avoid getting any moisture on the aircraft.

If the relative humidity is high and the temperature is low, then think about using a deicing fluid that has a decent hold over time to protect you from frost and once airborne, keep a close eye on the areas of the aircraft that ice up first (places like the temp guage probe on a PA28 for example) to give you some pre-warning of icing issues and keep out of cloud and rain.

[TURIN]

Light a/c not my field but I would just like to know how you chaps heat your B & Q sprayed de-icing fluid?

The Winter operations training I do every year clearly state that it is the "HEAT" in the fluid that removes the ice, the fluid then remains unfrozen due to it's chemical properties providing the holdover time etc.

Just askin' as some of the comments above (to my non-light aircraft experience) are just plain scary.

[mary meagher]

Interesting flying gliders in this weather - if it is below freezing when we get them out of the hangar, they frost up pretty quickly.

The good news is that with an East wind, by the time it gets to the midlands the sun usually comes out. If the glider is parked sensibly in the sunshine, the frost simply sublimates. After 20 minutes or so off you go, dressed in snowboots, long johns, sweaters, ski suit, woolly gloves, scarf, Russian fur hat with ear flaps, aviator sunglasses, electrically heated socks - and a parachute.

The worst bit about flying gliders in this weather is driving the quad bike to tow the glider back to the launchpoint.

[IO540]

I washed my car yesterday. I used hot water and then hosed it off. I then got a chamois out to dry it. The car iced up whilst I was doing it. Given that it was only just freezing and the car had been in the heated garage until I started to wash it. How sensible do you think it is to use plain water in sub zero temperatures as a de-icer?Not if it has not worked; that I agree with :)

And in most cases it won't work on the wings.

No water can possibly enter control linkages on a TB20? Want to bet your life on that IO?Having been all around the aircraft, I happen to know where they are.

There are places I would not use water, or anything else. For example my elevator trim jackscrew was "lubricated" with some gunge, by a maintenance company doing the Annual. It froze at FL140, -20C or so. With an A&P, we dismantled it and cleaned it out, packing it with the right grease.

I am not talking about hosing an aircraft down, in sub zero conditions. But I would not hose down a simple GA aircraft with a de-icer solution either, all over, because the stuff will get into all sorts of places, displace lubricants, etc.

[Say again s l o w l y]

Water gets everywhere, you don't just have to get it into the linkages, you can stick surfaces together, get it into hinges etc.etc. Even by just chucking a bucket over it.

You simply never ever use water in an attempt to de-ice an aircraft. This isn't a debateable point really. There is too much history in this game to prove that it's an appalling idea.

De-icing fluid was designed for a reason, so use that! It's not cheap, but then again, what is in aviation?

I would suggest that you spray the stuff everywhere, especially into hinges and linkages. Aircraft de-icing fluid is designed not to damage aircraft. It's not got chloride salts in it for example. So just spray the aircraft and if it concerns you, then get it cleaned.

If you are worried about linkages getting blasted clean by hoses etc, then don't fly through any rain... If you were using a jet wash directly on the greased parts, then that would be stupid, but an ordinary hose pipe will do naff all. The linkages are greased regularly anyway to combat this sort of problem.

I'd be more worried about potential icing issues than a bit of grease being perhaps washed away anyway. A dry coupling will wear out quicker and cause problems over a period of time. Icing can simply kill you fast. It's a far more serious problem.

As for grease freezing up, it does happen, but was the grease used the correct one? Or was it just whatever happened to be in the workshop at the time? In cold conditions, then different lubrication should be used to help prevent issues like that. -20 isn't really that cold in aircraft terms, but using summer time lubricants at that temperature is asking for trouble.

I do hope you gave the company that did the annual a rocket for not using the right stuff.

[Stephen Furner]

The snow and ice of winter has arrived here in the east of England. Aircraft parked outside on the airfield now have a winter coating of ice on their exposed surfaces. What are the best methods for getting this ice off a C172 without harming the aircraft?

:confused:

[TURIN]

Some good stuff here..Frost (http://www.pprune.org/private-flying/435108-frost.html)

[MarkerInbound]

As in most things, there is an inverse relationship beween time and money.
1. Wait for the temperature to come up.
2. Pull the plane into a heated hanger.
3. Spray it with de-icing fluid.

[Say again s l o w l y]

Hi Steven. As already mentioned. Brush any loose snow off. Pull the aircraft into the sun (it aids ice removal enormously) then spray with de-icing fluid.

Mick should have some in the hangar, Victoria should know where it's kept. You don't want to be trashing EC's paintwork by scraping away at ice!

[Stephen Furner]

You are quite right SayItAgain it is EC I had in mind. John was going to give me a lesson on night flying EC this evening but we had scrub it due to ice all over the exposed parts of the airframe.

Some interesting discussions in the FROST thread. It includes a very useful URL for a NASA training module on dealing with ice.

Finding a good place where it can catch the sun and thaw the ice gets my vote at the moment. Splashing warm glycol about seems a great way of dealing with ice if there is hard standing everywhere with effective drainage. However, for aircraft parked on grass it is probably not good for the airfield since I suspect it would poison the ground.

[Say again s l o w l y]

Say hi to John for me when you see him next. (It's Ifor by the way!)

Glycol isn't ideal to be stuffing into the environment willy nilly, it's not the most environmentally friendly stuff (it's not lethal of course.)
In real terms though, I doubt very much whether a couple of litres will make the blindest bit of difference to anything, but like most things, it's the cumulative effect that's the problem. Though if it's only a one off thing, then I really wouldn't worry about the environmental impact too much. It really isn't that bad.

[IO540]

What do you use to get frost off, SAS?

Something 100% guaranteed to not cause aluminium corrosion.

It also needs to be safe to carry the spray kit in the back of the plane, for de-frosting it away from base.

I know the stuff which does that (I use it in the prop TKS system) but it cost me £200 for a 20 litre drum :)

[neilgeddes]

Some really good advice and thoughts. Thanks everyone for taking the time to reply.


Say again s l o w l y: Why not get the aircraft fuelled the night before, do your preflight checks in the hangar, then just pull it out and go if you are worried about the aircraft icing up whilst parked outside. Don't mess around with icing. If it's below freezing on the ground, then do everything you can to avoid getting any moisture on the aircraft.


Yes, I agree and will see what I can do.


mary meagher: Interesting flying gliders in this weather - if it is below freezing when we get them out of the hangar, they frost up pretty quickly.


This is a concern I already had. How can I predict the likelihood of this in advance? Thanks.

[DeeCee]

Once you are up the ground will look quite different with frost or snow.

[Say again s l o w l y]

What do you use to get frost off, SAS?

Something 100% guaranteed to not cause aluminium corrosion.

It also needs to be safe to carry the spray kit in the back of the plane, for de-frosting it away from base.

I know the stuff which does that (I use it in the prop TKS system) but it cost me £200 for a 20 litre drum

It depends where, but Kilfrost RDF is pretty good, if not cheap. Aeroshell 07 works well too. You don't have to heat it which is a benefit and it's fine undiluted through a sprayer.

It is safe on paintwork and aluminium and unlike generic car type defrost stuff, it's safe on perspex windows too. Though I have seen lorry deicer that seems to be the same as Aeroshell and a fraction of the price, but I haven't used it myself.

I've heard of some de-ice pellets from Kilfrost that you apply by hand too, though I've not used them. Has anyone any experience of them?

If you're paying £200 for a 20 litre drum of TKS fluid, then you're getting done!

[mm_flynn]

Light a/c not my field but I would just like to know how you chaps heat your B & Q sprayed de-icing fluid?

The Winter operations training I do every year clearly state that it is the "HEAT" in the fluid that removes the ice, the fluid then remains unfrozen due to it's chemical properties providing the holdover time etc.

Just askin' as some of the comments above (to my non-light aircraft experience) are just plain scary.

Turin,

We are removing a little bit of frost on a -2 kind of day , not trying to get a 747 clear of a 6 inch snow covering in Munich. The chemicals substantially reduce the freezing point of water (after all that is how TKS deice works!) so the frost melts even if you have not heated the backpack. The liquid has a reasonable hold over so it doesn't refreeze. However, I take a towel round the aircraft to mop up all the now liquid frost. Clearly a bit impractical on a 747 (unless you have a lot of hostiees!)


IO,

The stuff I get from the airport is a two part mix (which they do for me), I am 99% sure it is the Shell product and I have used less than 5 litres in a year.

[Stephen Furner]

My impression from reading the comments here is that warm water is not to be used for de-icing and that Cat 1 aircraft de-icing fluid should be used. This of course raises the issue of where this fluid can be bought retail in the UK. I had a look at the usual suspects – Transair, Adam’s The Flying Shop, Harry Mendelssohn and AFE – but no sign of de-icing fluid in their on-line catalogues. Anyone able to recommend a few favourite pilot supply shops that retail de-icing fluid?

[IO540]

Kilfrost RDF is pretty good, if not cheap. Aeroshell 07 works well too.

Aeroshell 07 can be bought from Silmid (http://www.silmid.com/Products/Lubricants/Aeroshell-Lubricants/Aeroshell-Other-Fluids/AC0720.aspx) and yes I may have got fleeced but hey this is aviation. £151.28+delivery so nearly £200 for the 20 litre drum.

The other small point is that unless you are built like Geoff Capes, the 20 litre drum is damn heavy, so one needs to decant the stuff into smaller more manageable containers. Of course these must not leak especially if carried in the plane! I carry a 2 litre prop TKS refill container of fluid #7, I bought a quantity of these (http://www.camlabworld.com/item.asp?itemid=27784&categoryid=683&key=&letter=&browsecategoryid=3054) HDPE bottles which are also safe for carrying IPA (for putting into avgas, 0.5% to 1%, for high altitude flights at -30C or below - not that I know of a single case of TB20 fuel icing, unlike the Aztec in which it is reportedly endemic).

There is a lot of other de-icing stuff around, much cheaper, but one needs to be careful with "car" chemicals. I know of a TB owner in the USA who wiped out his £3000 (?) windscreen by applying Rain-X to it :)

All that said, if you have to pay £200 for 20 litres of #7 and have to spray it all over the plane after a cold frosty night with no sign of the temps going above zero, it's going to cost a packet.

[1800ed]

'Plastican' fuel containers are also good at carrying TKS fluid in. (OK for re-filling your ice protection tanks, no good for de-icing your aircraft though).

[Say again s l o w l y]

200 litres should last you an age! I'd be more worried about it having an expiry date than running out of it to be honest! Especially if you mix it with hot water too.

Steven, try here to get some. LAS - Kilfrost Products (http://www.lasaero.com/site/products/article?id=P03GEFU1H)

Get a couple of containers, lock them away in the hangar with your name on and get a sprayer from B&Q. Borrow a step ladder from the fire shed and spray away!

[Stephen Furner]

Good lead sayitagain. Many thanks.

Killfrost has a new very interesting product in its range called Killfost sustain, which looks to be very well suited to aircraft parked out on grass. Kilfrost | Kilfrost Sustain (http://www.kilfrost.com/kilfrost-sustain)It has both a low energy production process and is biodegradable.

[mary meagher]

From your initial question, you do have time to spare. the next two suggestions from mm flynn and englishal I think really cover the situation nicely. As for buying antifreeze spray and gunk, that sounds like money for trouble later. Lavish use of water even in fine weather leads to corrosion.

Lucky you to have a hangar to keep the pride and joy safe.... refuel the day before, keep it full if possible (this prevents condensation accumulating in your tanks).

As for predicting frost on the wings and tail, your car in the morning will give you an idea of the problem! No hurry, you've done all the planning before you roll it out. Fog and low cloud? decide on some other activity. Cold bright sunny day, best of all. The improved performance will be a revelation.

[Windy Militant]

Obviously this is not going to work in -20C but we don't get that in the UK
It was -18ºc in mid Wales last night and I have seen indicated temps of -20ºc when driving in Scotland.
My niece had to be rescued this morning after a night shift at the hospital she works at as the brakes on her car had frozen solid. It was only -10ºc there!

[Pace]

SayItAgain slowly

While I agree with a lot of what you are saying about using water I cannot totally agree.

Water from a bucket is not the only way of the airframe getting soaked.

I can remember a difficult instant in a Seneca Where I was held in a torrential donwnpour at 3000 feet awaiting a climb clearance into CAS to FL120.

I got the clearance trimmed the aircraft in the climb. The rain diminshed as the aircraft climbed and on reaching FL120 I attempted to level.

The trim wheel had frozen solid and using power and a lot of out of trim forces I had to descend to warmer air until the trim wheel came free again.

This was a result of intense rain not from a bucket.

I have used warm water but only on the leading edges which are the most important bits and over the screen.

If used very carefully and away from any moving surfaces where water could get into the control lines etc it is a useful way of helping remove ice.

I totally agree the correct fluids are better if available but dont discount water if used with utmost care.

Pace

[IO540]

20 litres, not 200 litres, SAS.

[24Carrot]

After all this typing, I just saw that Pace made a rather better post. Oh well,

Say Again:

I believe water would work in the end, it's just the quantity that makes it impractical.

I did a few ball-park calculations for a C172 at -2 deg C.

If some 30 sq m of wing, fuselage, etc is covered in 1mm of frost, that is 30kg of ice at -2 deg.

The specific heat of ice is 0.5 kCal/kg/degC (also cal/g/degC)
so we need 2 x .5 x 30 = 30 kCals to get it up to zero.

Then we need the latent heat of fusion/melting, 80 kCals/kg/degC.
80 x 30 = 2400 kCals.

Then, to mop it up without it freezing, we want it at perhaps +3 degs, so with a specific heat of 1, we have
3 x 1 x 30 = 90 kCals.

So that's 2520 kCals to clear the ice and get it to a moppable temperature.

But we also have to warm the aircraft and fuel from -2 to +3, ie through 5 degs C.

Say 500kg of Aluminium at 0.2 kCals/kg/degC is:
5 x .2 x 500 = 500 kCals

Say 135kg of fuel at at 0.5 kCals/kg/degC is:
5 x .5 x 135 = 338 kCals

Which gives us a total of 3358 kCals required.

Ordinary water at 10 degs C will have 10 kCals/kg of useful heat for clearing the ice (which is most of the requirement), and then down to 7 kCals/kg for heating the airframe. So at least 335 litres will be required.

But with such small temperature differences the heat transfer will be poor (except for the very first water which freezes on contract) and I suspect we are talking about at least a tonne of water, very slowly and painstakingly applied.

Warm water does't help much because in thin sheets it evaporates and cools quickly, giving up heat to the atmosphere instead of the airframe.

So not very practical.

There is also the little issue of what happens to the water. Putting a tonne of ice on an apron may not be popular, nor making a huge muddy patch in a field.

[Say again s l o w l y]

Sorry IO, I was speed reading that and horlicksed it up!

Pace. I understand what you are saying. However, you flew into icing conditions and fortunately got out of it.

I've had plenty of experiences with in-flight icing, fortunately though it's usually on machines with proper kit. I remember one fight coming back from Le Bourget when we got caught up in the top of a growing CB. We picked up ice at a horrific rate, even though every bit of kit was going full bore.

We slowed by 30kts in a couple of minutes even though we were at max continuous power. The aircraft was empty and we had 2 PT-6's giving it the beans and that still wasn't enough.

We did a dirty dive into our home base and once we landed the amount of ice on the airframe was horrific. It was a couple of inches thick and I shudder to think what would have happened had we not been in an aircraft with full kit on it and all the excess power we had available. When you pick up ice, it happens fast.

At no time did we have any control issues though.

There is no need to take the risk with using water as a de-icing fluid. Proper fluid is easily available and isn't that expensive, especially not in comparitive terms to the other costs in aviation!

Pouring water of any temperature over a sub zero aircraft is silly. It will always leave a tiny bit of a layer behind it unless you rub away at it for an age an inspect it very closely and as we all know, ice begets more ice.

Use the proper stuff and totally de-ice the aircraft in the correct manner or don't bother going flying. It's not hard really! It's also a darn sight faster and easier than mucking about polishing the aircraft to get rid of every last bit.

Now, the FAA do allow ice polishing and then to go flying in certain circumstances, but the best solution is to rid yourself of all of the ice.

[IO540]

Great analysis, 24carrot :ok:

I have long forgotten how to do the latent heat of fusion calculations but the principles remain :)

It's actually not as bad, however.

I may need to get my coat after this but the areas from which one really needs to remove frost are the aerodynamic surfaces, the prop, and the windows. Frost on the cowling and the roof doesn't matter. I have flown my plane covered in spattered flies, and covered in firmly stuck-on grass cuttings (from landing in a field with ~ 10" grass) and it made no visible performance difference.

You don't need to warm up the engine etc etc to +3C. In fact with an OAT of say -2C (a pretty common UK morning scenario) the cockpit temp will be easily +5C once the windows are clear. I have done some RH measurements (to test the effectiveness of silica gel to keep an unpressurised and thus not well sealed cockpit dry) and the solar heating even in murky daylight is substantial.

+10C tap water applied to the airframe at -2C will simply not freeze. The frost comes straight off and the water runs off and that's it. The specific heat capacity of 1-1.5mm aluminium and window etc plastic is miniscule.

It is the wings which are the problem and that is what I found doesn't work. I don't think any practical quantity of water will warm up the wing tanks from the lowest temp seen the previous night (say -5C) to something positive.

I know a lot of people use car fluids but that is IMHO highly dodgy.

[Say again s l o w l y]

24 carrot. Don't waste your time calculating stuff like that. Spray the aircraft with de-icing fluid and leave the test flying to the pro's.

People often like to think they should reinvent the wheel in aviation, but I can promise you that the correct and prescribed methods for things like de-icing have come from years of long and bitter experience, often paid for by people's lives.

Don't p*ss about with ice or water. Buy the right stuff, apply it properly and you'll minimise the chances of killing yourself because of ice issues. If you haven't got the kit to do it right, don't be stupid, get back in the car, go home and then walk to the pub and enjoy a pint.

Cutting corners in aviation only ever leads to trouble. Keep It Simple.

Edit to add: I can assure you that it is more complex than simply looking at energy and things like latent heat. The airframe wouldn't cool or heat in an equal manner and there are a whole heap of different materials that have different thermal properties.

The problem with stuff like this, is that someone will read it and think that they know better than the usual teaching and then try it. These people are known as idiots, but there are plenty of them in the flying world.

[Pace]

Pace. I understand what you are saying. However, you flew into icing conditions and fortunately got out of it.

SayAgainSlowly

My arguement was to describe that in heavy rain the airframe is getting a soaking which could lead to water getting into the control linkages etc.

Obviously an aircraft is moving at 150 kts plus through the air while an aircraft on the ground is static when you pour your bucket of water over it.

That was the only occasion when I have ever had a control freeze. I have 3000 hours in Seneca Fives and have flown them all over the place in all conditions so know them pretty well.

On that occasion the rain was in plus temperatures and the aircraft flew up into freezing air. Strangely I did not pick up ice in the climb but water from the heavy rain lower down had obviously got into the controls and frozen solid.

Pace

[24Carrot]

Say Again Slowly:

If you read my post again, you may notice I did not recommend using water.

[Say again s l o w l y]

Which is as to be expected. Flying through water with a cold airframe will lead to ice problems. One of the reasons it is to be avoided.

[Say again s l o w l y]

24 Carrot. I saw that. I know you think it's a daft idea, but someone else might read it and then try it. They're the one's I'm worried about!

[JW411]

I would also avoid Type IV fluid unless you are prepared to thoroughly clean off any residue at the end of the flight.

We had trouble at work with it solidifying inside the mass balances on the elevator and causing vibration after a few applications.

[IO540]

So... what stuff is 100% safe - apart from Aeroshell fluid #7 which appears to cost £200 for a 20 litre drum?

[24Carrot]

IO540, could your wings, unlike the rest of the aircraft, be a lot colder than the minimum night time air temperature? Perhaps the ground, (which cools the air), and the wings undergo radiation cooling at different rates?

It is very noticeable that car roof tops frost over more than the sides of cars, unless the car is tilted (eg on a cambered road) when the part pointing at the sky is the most frosty. You can see similar effects when there is a tall building on one side of the car.

[Say again s l o w l y]

The only thing that is 100% safe is to not go flying if you have ice.

Other than that, use the Kilfrost or Aeroshell or A.N.Other approved fluid.

Could you imagine if something did happen to you and it was discovered that you'd used a non-approved de-icing method? Wave cheerio to any insurance payout for both the aircraft and yourself.

These fluids aren't a panacea and they do have to be used correctly, they can also add other problems as demonstrated by JW411. However, they are the most sensible way for people flying GA aircraft to clear ice as safely as possible, other than to hangar it and avoid the stuff in the first place.

Seriously though, when you have an aircraft worth a few hundred grand and running costs that would horrify sensible people, the cost of using the correct de-icing fluids is so small as to make it irrelevant. Especially given the potential problems that not clearing ice can lead to.

[IO540]

IO540, could your wings, unlike the rest of the aircraft, be a lot colder than the minimum night time air temperature? Perhaps the ground, (which cools the air), and the wings undergo radiation cooling at different rates?

It is very noticeable that car roof tops frost over more than the sides of cars, unless the car is tilted (eg on a cambered road) when the part pointing at the sky is the most frosty. You can see similar effects when there is a tall building on one side of the car.I think it is simply because the supercooled water droplets are coming down more or less vertically, unless modified by some local airflow, and then it freezes up to create frost.

That's why one doesn't get frost underneath the wings, IMHO.

The wing tanks will definitely be colder. If I turn up to fly at 9am and it is -2C, I bet the fuel will be at say -5C from the middle of the night.

it was discovered that you'd used a non-approved de-icing method

I thought that an American Express card was approved for this purpose; it seems to be widely used by instructors :)

Personally, I would use a Santander card - this is the most arrogant institution around today.

[Pilot DAR]

I just looked at my other plane (two planes, but only one hanger here) - it's covered in snow! So I decided to just leave it, and come and read PPRuNe.

I've just got done the recurrent exam on icing and the Cessna Caravan (a type found to be rather sensative to airframe ice). The proper de-ice fluid in a spray can is the way to go. You cannot convince me that sloshing the plane with plain water is a good idea. It is one thing if you fly through soaking condtions, then it freezes - that's a design failing. But, the plane was not designed to resist being sloshed by a pilot on the ground, who was unwilling to use the correct technique to deice a plane. You might get away with it for a while, but the time important things start freezing at altitude, and you have trouble controling the aircraft, the cost saving won't seem worth it any more.

Hands up, all those pilots who have suddenly found that the aircraft they are flying has had a control system completley jam, or found the stall speed is now 15 kts higher than you though it was.

Your effort as a pilot to keep the plane as close as possible to the configuration it was manufactured in, will afford you the least stressful flight. Looking at the plane safely tied down, waiting for another day, is also very low stress....

[Piper.Classique]

Some interesting stuff here. Does anyone know which if any of the de-icers are safe on fabric? Oh, and the aircraft colour will make a difference to how quickly it warms up in the sun, of course. Used to have a glider with a pale blue wing and a dark blue leading edge, did a fair bit of wave flying so it often got pretty cold. The leading edge ice/frost always melted first. Got a yellow aeroplane now, which lives in a hangar except when we are touring.

[mm_flynn]

Now, the FAA do allow ice polishing and then to go flying in certain circumstances, but the best solution is to rid yourself of all of the ice.

Not since January of this year FAA comment (http://www.faa.gov/news/press_releases/news_story.cfm?newsId=11003)


I think it is simply because the supercooled water droplets are coming down more or less vertically, unless modified by some local airflow, and then it freezes up to create frost.

That's why one doesn't get frost underneath the wings, IMHO.

No, Frost forms on the upper surface (normally at night) due to the surface radiating heat to the -265 ish degree black sky. This substantially reduces the skin temperature and it causes water vapour to freeze out of the air.

The bottom surface radiates to the roughly 0 ground and hence doesn't cool significantly.

[Say again s l o w l y]

Thanks for that mm_flynn. I wasn't aware of that having changed.

[rightbank]

That's why one doesn't get frost underneath the wings, IMHO.


Not true. The E135/145 is very susceptable to underwing icing. In fact the AFM (if I remember correctly) allows you to depart with up to 3mm of underwing ice. Nothing on the top surface though.

[mm_flynn]

Not true. The E135/145 is very susceptable to underwing icing. In fact the AFM (if I remember correctly) allows you to depart with up to 3mm of underwing ice. Nothing on the top surface though.

I would be very surprised to find the E135 collects FROST on the underside, but not top side when left out overnight (I am not considering cases such as having just landed after a good cold soak or in flight icing).

[rightbank]

(I am not considering cases such as having just landed after a good cold soak or in flight icing).



That is the point that you should consider as it really does exist. Have had it many times. Even overnight, given certain overnight temps, the top surface can be clear (melted), but the thermal mass of the fuel causes frost to remain on the underside. Unfortunately I don't have any pics of it, but I have seen it many times. Far more so than on any other aircaft I have flown. Check out the AFM for more proof.

[robert mailer]

Just what i was thinking, but where would i buy plane de icer,also do you mix it 50 50 with water?, look on web and could only buy in very large a mounts:confused:

[Say again s l o w l y]

Read the whole thread. You'll find the answer.

[Big Pistons Forever]

Most airplanes that are "frost" covered can be cleaned with a stiff broom. That is ceratinly what I would try first.

A truely ice covered aircraft should only be dealt with by using a proper heated aircraft deicing fluid or throughly warmed in a heated hangar. I would suggest that homemade deicing solutions should not be used as they can harm the paint or worse can be corrosive enough to damage control surface bearings, hingers, rod ends etc, or when they pool inside the sheet metal structure.

The bottom line however, is no amount of ice on a flying or control surface is acceptable.

[Stephen Furner]

Robert, clearly deicing is currently a popular pastime. Of the on-line retail suppliers I checked for Killfrost or other deicing fluid all were out of stock waiting for a new supply. The only fluid I could see available for purchase at the moment was direct from the manufacturer – Killfrost RDF is available in 25 litre barrels at around £150 including transport from their www site http://www.kilfrost.com/online-shop/general-aviation (http://www.kilfrost.com/online-shop/general-aviation)

[neilgeddes]

No frost to speak of this morning at Redhill. But broken cloud at 900' so flight to Barton cancelled. Light snow up there too.

Thanks for a very interesting and informative thread! :)

[IO540]

No, Frost forms on the upper surface (normally at night) due to the surface radiating heat to the -265 ish degree black sky. This substantially reduces the skin temperature and it causes water vapour to freeze out of the air.

The bottom surface radiates to the roughly 0 ground and hence doesn't cool significantly.

I am going to test that, with a thin sheet of copper or ally, which cannot possibly have different temperatures on top v. bottom. An interesting idea but I need convincing.

[Jan Olieslagers]

A thin sheet will not be representative, due to strong thermal conductivity between upside and downside.

Still I'm curious to see what ally you'll be using: légionnaires must slice much thinner than GI's, meseemeth.

[mm_flynn]

As jan says, the two surfaces must be thermally separate otherwise you just wind up at a plate with the net balance of heating from the ground, cooling to space and convection to the air. Even a plate bent 180 should have enough air gap (and the conduction at the edge will be much more limited than across the front to back.

[mary meagher]

Fibreglass glider left out overnight at Aboyne (Deeside Gliding Club). Use of credit cards for removing ice from flying surfaces the usual treatment.

One evening, warmer and a wee drop of rain, so no frost to contend with. Surfaces nice and clean. Bright day, sunshine, lenticular clouds beckoning. Warmly dressed, followed the Pawnee to 2,500' above site, pulled off in lift, worked the wave to 12,000' or thereabouts, when the ailerons declined to move any more. That's interesting, I said to myself. Turned gently with the rudder, that was okay. Airbrakes okay too. Just no aileron function at all.

Decided to descend, gingerly. Below 5,000 they freed up enough to do a safe approach and landing. I consulted with Dave Richardson, who easily diagnosed the problem; the aileron tape, still wet, had frozen. Simple, really.

Main thing, if something seems wrong, don't panic, work with what you've got left. I'm just glad there was no problem with the elevator.....

[24Carrot]

@Mary, that is still a scary story!

@The Science Club: I would love to hear the results of the experiment. Paradoxically, I would expect the upper plate to be warmer, the more ice that formed on it. The latent heat of deposition (vapour to ice) is 720 cal/g, so 1g of ice is enough to raise 3.6kg of Aluminium (Ally?) by 1 deg C. I would still expect the upper plate to be cooler than the lower plate though.

I was just listening to the head of salting and gritting for Leeds. He made the point that the ground temperature is lower than the air temperature. Which I think I learned somewhere. The ground cools the air, and that cool air stays put close to the ground, underneath the warmer air at 4-feet where the official air temperature is measured. So if the wings are radiation cooling, like the ground, they too can be colder than the lowest overnight air temperature.

[RatherBeFlying]

I once spent considerable time scraping off frost between the rivet lines on a C-172 and found that while the a/c did take off, the ravine at the end of the runway was most helpfully placed for building to a higher than book climb speed:uhoh:

If the approved fluids are not immediately available, -40C automotive windshield deicer applied with windshield scrubbing sponge and squeegee should do the job without damage to the paintwork -- but please test first on a small patch and remember that aircraft windshields and windows are especially vulnerable

Once the wing and tail are clean and dry, it does not matter how the result was achieved.

[IO540]

As jan says, the two surfaces must be thermally separate otherwise you just wind up at a plate with the net balance of heating from the ground, cooling to space and convection to the air. Even a plate bent 180 should have enough air gap (and the conduction at the edge will be much more limited than across the front to back.

Sure, but a single plate which frosts up only on the upper surface would disprove the assertion that it frosts up only on top due to the greater radiation heat loss into the sky.

[TURIN]

mmflynn
We are removing a little bit of frost on a -2 kind of day , not trying to get a 747 clear of a 6 inch snow covering in Munich. The chemicals substantially reduce the freezing point of water (after all that is how TKS deice works!) so the frost melts even if you have not heated the backpack. The liquid has a reasonable hold over so it doesn't refreeze. However, I take a towel round the aircraft to mop up all the now liquid frost. Clearly a bit impractical on a 747 (unless you have a lot of hostiees!)

A frost covered 747 in any temp will be deiced (as necessary) with a concentration/mix of de-icing fluid, probably Type II in UK, warmed to about +80C. It could be 50% or more commonly 75% mix of fluid/water to give a better hold over time. The chemicals in the fluid, as you say, substantially reduce the temp at which the water/fluid mix will re-freeze. But that is it's purpose, to stop the applied fluid re-freezing. It is not there to remove the ice in the first place, heat is the primary agent in removing ice/frost.
Type IV fluid is rarely, if ever, used in UK. It isn't necessary and as has been said, can cause more trouble if the excess fluid is allowed to build up in aerodynamically dead areas in hinges or control surfaces. It dries eventually and then when it gets wet again rehydrates and swells up only to refreeze as you climb to lower ambient temps. It has happened on several large a/c.

My point is that a/c size does not matter, the procedure should be well known by all operators and followed to the letter. It saves on messy paperwork. :ok:

Anti-icing is used if the forcast is accurate. Can that method be implemented on light a/c or is that too impracticle?

[Jan Olieslagers]

Further browsing the www on this subject, as nothing more useful seems to be possible under the present wx, I came upon

If on arrival you descend with an iced up aeroplane and windshield and cannot see, use the DV window.

Any suggestions as to the meaning of the "DV" window? Dorsal view? Dual visualisation? Direct ventilation?

The full document is at

http : //www .ebzr.be / LinkClick.aspx?fileticket=hEVd4RWiFrU%3d&tabid=40&mid=412

(a few blanks inserted to disable link expansion)

and seems to confirm most of what was said here, including the garden sprayer.

[Say again s l o w l y]

A DV window is a Direct Vision window. Usually something that you can open and so get a view no matter whether the main windows are iced up/shattered. Think the little window flap on the PA28.

[IO540]

warmed to about +80CThat is a helluva temperature. It would melt the windows in a light GA plane.

Re windows, some deiced planes have a little heated window on the front, so the pilot can see "something". It is a poor man's version of the £20k heated glass windscreen :)

With TKS you don't need it. In fact my prop-only TKS does a good enough job on the front window.

[Stephen Furner]

LAS Areospace Ltd now has Kilfrost RDF in stock according to their on-line shop, and it comes in at about £50 for a 5 litre container including VAT and delivery. Needless to say at £10 a litre the words "dilution with hot water" spring instantly to mind. Are there any reliable recommendations or guidelines about dilution of this type of de-icing fluid?

[dublinpilot]

Kilfrost have their own webshop which seems to sell it for £110 incl VAT & Delivery for 25ltrs. So while still expensive it's better value, though less easy to handle and store.