Frost

[I fLy pLaNeS]

When I think of frost I think of it affecting the upper surface of the wing. Is frost below the wing and also on the top of the fuselage a danger?

 

[Dr Pokenhiemer]

Frost GENERALLY affects the leading edges and the front 1/3 of the leading edges and control surfaces. When it forms, it's like little jagged peaks and creates parasite drag. This is the reason you cannot takeoff without "polishing" the frost smooth. All the frost does not need to be removed, just smoothed. The fuselage is not a a leading edge nor a control surface, however, depending on the size of the plane and the magnitude of the frost, you will have a little extra weight, but I've never heard of that being a factor.

 

[RipCurl]

Say I get all the frost off the wings with some glycol, but the whole fuselage is still frosty as can be. Would the extra drag be something to worry about?

 

[Dr Pokenhiemer]

Never was a problem for me. I flew cargo in a C210 during a couple of winters. Never deiced the fuselage. Even had to deice the Lear once and they just got the wings and tail to clear the freezing rain. The rest of the frost will sublimate off within a few minutes. Watch it on your windshield. Make sure to clear you view, but watch the rest of the frost disappear shortly after takeoff. MAKE SURE you students understand that they cannot take off with frost on the wings or control surfaces though as I explained earlier.

 

[groundpointsix]

Didn't the FAA come out with something last winter saying "polished frost" was no longer an acceptable method of operating and that the airplane had to be completely free of frost?

 

[Dr Pokenhiemer]

Section 91.527: Operating in icing conditions.

(a) No pilot may take off an airplane that has—
(1) frost, snow, or ice adhering to any propeller, windshield, or powerplant installation or to an airspeed, altimeter, rate of climb, or flight attitude instrument system;
(2) Snow or ice adhering to the wings or stabilizing or control surfaces; or
(3) Any frost adhering to the wings or stabilizing or control surfaces, unless that frost has been polished to make it smooth.

 

[avbug]

Frost can make an increadible difference in the amount of lift available. In a light aircraft, it may make the difference between being able to climb out of ground effect, or not. It may double or more, your takeoff distance. It may increase your stall speed considerably.

Frost on your fuselage may or may not be very detrimental to your performance, but many aircraft derive lift from the fuselage, too. Frost can act as a starting point for more ice, as well as aerodynamic penalties associated with the roughness.

Think clean airplane. Forget the notion that frost sublmiates. It may, or it may not, but it's a foolish thing to plan on. A little like assuming that engine roughness will go away. Any ice, even frost, can be very dangerous.

Stick to the clean airplane concept. It's always a good policy.

 

[I fLy pLaNeS]

Thanks for the info

 

[JohnE]

Section 91.527: Operating in icing conditions.

(a) No pilot may take off an airplane that has—
(1) frost, snow, or ice adhering to any propeller, windshield, or powerplant installation or to an airspeed, altimeter, rate of climb, or flight attitude instrument system;
(2) Snow or ice adhering to the wings or stabilizing or control surfaces; or
(3) Any frost adhering to the wings or stabilizing or control surfaces, unless that frost has been polished to make it smooth.

How does one "polish" frost?

 

[Dr Pokenhiemer]

Rub it with your hands or a cloth to make it smooth--just knocks the jagged tops off to reduce drag.

 

[Gulfstream 200]

Just an opinion:

If you find yourself needing to "polish" frost....just get deiced.

If you a wondering if you really need to get deiced....just get deiced.

Lets stop with this polishing nonsense. The only thing you should polish is your wifes/girlfriends backside after you safely arrive home, carried by a nice clean deiced wing.

just spray it - if anything, for peace of mind.

You're worth it.

 

[MauleSkinner]

Just an opinion:

If you find yourself needing to "polish" frost....just get deiced.

If you a wondering if you really need to get deiced....just get deiced.

Lets stop with this polishing nonsense. The only thing you should polish is your wifes/girlfriends backside after you safely arrive home, carried by a nice clean deiced wing.

just spray it - if anything, for peace of mind.

You're worth it.

Not that I disagree in concept, but "just" getting deiced isn't an option. Some places simply don't HAVE deicing capability, and the only other choice is to wait til spring, which is a long way off right now.

Personally, I'd polish frost, provided adequate margins in performance exist to make me (and my copilot, if applicable) comfortable with the operation.

Fly safe!

David

 

[Gulfstream 200]

Not that I disagree in concept, but "just" getting deiced isn't an option. Some places simply don't HAVE deicing capability, and the only other choice is to wait til spring, which is a long way off right now.

Personally, I'd polish frost, provided adequate margins in performance exist to make me (and my copilot, if applicable) comfortable with the operation.

Fly safe!

David

So you go into places that you have to rely on polishing frost in order to take off? or wait until Spring?

What if you had too much frost? or snow?

How does one determine when it is adequate to go? (Im serious) I wouldn't know.

 

[Dr Pokenhiemer]

The original post and the second question were from relatively new CFI's. I took the meaning of their questions to be about the first flight of the day on a morning with frost, in a C172 or something like that. So that's the way I responded to the question. Even in the Lear, while flying air ambulance, we would take a bedsheet, one person infront of the wing and one behind, and polish the frost by pulling the sheet back and forth like a crosscut saw. This method is perfectly acceptable, safe, and legal. It's a lot cheaper than paying for a service you don't need, however, cost shouldn't be your reason for not deicing. Freezing rain on the other hand requires de-icing. In any case, use common sense and if you don't feel safe about it-don't fly.

 

[9GClub]

I dunno about the frost-polishing stuff guys..... why not just get rid of it altogether? I'm sure there are creative ways to get rid of it without having to do the glycol thing. Sometimes the very act of "polishing" is enough to melt it and get rid of it if it's thin. Or hot water as long as you get rid of all the moisture afterwards. Coffee? Urine?


Don't piss on your plane. Coffee's probably not a good idea either. You get my point.


I'd spray glycol on aircraft all the time back when I was working the line, but in restrospect I didn't have much of a clue about the mechanics of icing. There was a "hit the leading edge real quick and you'll be fine" mentality that was kinda laissez-faire. Don't rely on the line guys to make your plane safe.

"Polishing" frost seems like a shortcut to me. This is one of those controllable factors that can prevent accidents as long as pilots take a little extra time on the ground.

 

[avbug]

Even in the Lear, while flying air ambulance, we would take a bedsheet, one person infront of the wing and one behind, and polish the frost by pulling the sheet back and forth like a crosscut saw. This method is perfectly acceptable, safe, and legal. It's a lot cheaper than paying for a service you don't need, however, cost shouldn't be your reason for not deicing.

Presumably you were operating a learjet with a newer "soft" wing. If you were flying an older lear without the upgrades, you might not be so quick to do that. In fact, you might not get off the ground.

You're right, cost shouldn't be your reason for not deicing. Put it in a hangar, if cost is the issue. The hundred bucks it will cost is better than the six hundred to two grand it can cost to deice.

Is polishing acceptable under certain circumstances? Yes, but not in all aircraft. Many aircraft specifically require a clean surface, and you should always strive to fly a clean surface.

I've been in remote locations where sawing show and ice off the wing with tiedown ropes and polishing frost has been essential; no hangars, no deice, no heat, and very limited resources. No way to stay long and stay well. However, in some aircraft, it's still not acceptable. Aircraft with laminar type surfaces can experience unacceptably high decreases in laminar flow, and movement forward of the separation point on the airfoil, such that performance degrades enough to make takeoff impossible, or climb low or non-existant.

You can get away with it on a Cessna, which is basically a barn door with an engine. You can get away with it on some aircraft with a lot of power, or some aircraft that are so draggy to begin with that the aircraft hardly notices any more. Conversely, when you're out of performance, you're out of performance. Any time deice is available, it's a far better choice than polishing frost or ice.

 

[Gulfstream 200]

all right, I can see bush flying or the sorts...

but no other reasons to do this polishing nonsense. Im worth the de-ice bill. especially on any kind of performance plane.

pains me to hear of accidents like Ebersoll in CO. That 2K worth of deiceing saved is going to cost many many millions and even worse, lives.