Frost
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Frost
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.
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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)
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)
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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....
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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!
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!
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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...
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...
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.
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.
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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.
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.
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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 hangar 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, hangar the plane, or as a last resort, put on wing covers the night before.
There are proper deicing fluids for defrosting aircraft, or put it in a heated hangar 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, hangar the plane, or as a last resort, put on wing covers the night before.
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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?
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?
@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.
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.
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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.
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.
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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.
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.
Last edited by Say again s l o w l y; 27th Nov 2010 at 19:35.
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If everyone was as clever as an instructor, he'd soon be out of a job... 
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.....
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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).
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).