How much frost...

Jim K

Jim K

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Flew to my neighboring airport yesterday afternoon. I expected to be departing before dark, but wound up not getting back to the plane until 5:30 (I hate winter). Did a brief pre-flight, and found that there was already a light coating of frost on it.

I would say it felt like maybe 400-600 grit sandpaper, and was thin enough to easily see through. I remembered reading in the PHAK how I'd instantly die a fiery death if I attempted takeoff with frost on the wings, but I reasoned that it didn't seem worse than the film of dust on the wings (airplane needs a bath) when I left home, I was 200lb under max gross, and I had an 8000' runway. If she didn't want to rotate & climb like normal, I should still have a mile to put her back down.

Everything went as expected. So.... how do I tell how much frost is an issue? Did I make a poor decision and get away with it? If so, I'd like to know so I'm not tempted to push further next time.
 
I knew a CFI once that while teaching would routinely tell his students that they could safely take off with frost as long as they "polished it", i.e. smoothed the rough surface with a piece of rope, or something similar. That practice was discontinued when he and a student ended up in a river off the departure end of the runway. Fortunately they both survived with minor injuries.
 
First off, this was a very dumb move. Do not attempt that again! You should definitely not attempt flight if there is frost on the windows that would affect visibility, or on any of the wings or flight control surfaces.

An FAA bulletin on this topic says “frost the size of a grain of salt, distributed as sparsely as one per square centimeter over a wing's upper surface, can destroy enough lift to prevent the airplane from taking off.” Continuing to just forego what you’ve been told about frost, will likely make you a statistic one day, sorry to be so blunt.
Luigi said:
I knew a CFI once that while teaching would routinely tell his students that they could safely take off with frost as long as they "polished it", i.e. smoothed the rough surface with a piece of rope, or something similar.
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Some aircraft are prohibited under 91 Subpart F from polishing frost smooth - they must remove all of it prior to takeoff. Even though our light GA airplanes don't fall under this rule, it only makes sense to comply with it. Our wings are just as susceptible to the reduction in lift and increase in drag caused by ice and frost.
 
A lot depends on the particular airfoil - some are more sensitive than others. Some of the early laminar wings on sailplanes would give an obvious loss of performance from rain. The original airfoil on some Rutan designs would provide a significant pitch down from rain on the canard.

But in any case, one is pushing towards the edge of the envelope.
 
Reg:

§91.527 Operating in icing conditions.

(a) No pilot may take off an airplane that has frost, ice, or snow adhering to any propeller, windshield, stabilizing or control surface; to a powerplant installation; or to an airspeed, altimeter, rate of climb, or flight attitude instrument system or wing, except that takeoffs may be made with frost under the wing in the area of the fuel tanks if authorized by the FAA.
 
I always remove frost from my plane prior to takeoff. Too unpredictable. 135.227 (helo) has got me covered for work as well. I have taken off a few times with frost back in my dumber military days. A bit different than an airplane though because I think the rotors sublimate the frost quite quickly...or at least that’s what we told ourselves.;)
 
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It varies from one airplane model to the next, but don't play around with frost. It can seriously degrade your aircraft's climb performance. Similar thing with sticky pollen (like we have here in the southeast).
 
I’d probably not do that again. Get rid of all the frost on the critical areas
 
"Frost the thickness of sandpaper can reduce lift by 30% and increase drag 40%."
 
Ok, so I fly a 150. In the summer it flies and climbs like a sack of bricks if fully loaded. In the winter it climbs at full gross straight up like it is light as a feather (comparatively in both cases). I flew it all winter and certainly had frost on the wings with little to no degradation in performance. And certainly performance was better than anytime in summer.

Those wings are covered in screws, exposed rivers, rough paint, fuel caps, panel seams, and (not much on mine, but on a lot of others) ripples and bumps in the skin. I agree that laminar flow wings are affected, but the C150 wings are already far from smooth on a good day and a bit of frost that feels like 400-600 grit would make mine feel smoother than they are right now!

I do have a bottle of RV antifreeze that I spray or splash on the wings when the frost is real thick or if snow and ice get stuck. Works well and melts it all off quickly. But a patch or two here or there that I missed never made any difference.
 
We're doing a series of seminars right now and this issue of frost is covered in one interesting case story. I'll skip the narrative here, but the end result was that I managed to get the frost off the airplane at a mountain airport. Clean everywhere >except< over the fuel tanks. My lift production was so decreased that I rejected the takeoff. These two rectangular areas still covered in frost had a dramatic effect.

If you're on a nice long runway with no obstacles or rising terrain, a small amount of frost might not be much of an issue. If climb performance IS an issue, don't fug around with frost.
 
Thin, relatively smooth frost hasn’t stopped me. Thick, rough frost is clearly a no-go.

Sublimation is an excellent frost remover. Frost dissipates quickly. Clear ice that forms under wing covers takes longer.
 
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Jim K said:
Flew to my neighboring airport yesterday afternoon. I expected to be departing before dark, but wound up not getting back to the plane until 5:30 (I hate winter). Did a brief pre-flight, and found that there was already a light coating of frost on it.

I would say it felt like maybe 400-600 grit sandpaper, and was thin enough to easily see through. I remembered reading in the PHAK how I'd instantly die a fiery death if I attempted takeoff with frost on the wings, but I reasoned that it didn't seem worse than the film of dust on the wings (airplane needs a bath) when I left home, I was 200lb under max gross, and I had an 8000' runway. If she didn't want to rotate & climb like normal, I should still have a mile to put her back down.

Everything went as expected. So.... how do I tell how much frost is an issue? Did I make a poor decision and get away with it? If so, I'd like to know so I'm not tempted to push further next time.
Click to expand...

It is one thing to take off with an inoperative radio or flight instruments, but taking chances with the basic flying surfaces is not worth the risk. I have used antifreeze spray to melt off the frost. You were on the ground, and presumably no zombies were chasing you. so staying put would have been the best choice. The fact that it worked out this time might tempt you to push the envelope next time, which is probably the bigger consideration.
 
/sarcasm on

Just pour hot water on it to melt the frost

/sarcasm off

Seriously, it depends on the plane and the airfoil among other things. Like inflight icing, not something you want to knowingly mess with. Personally, on the plans I've flown and owned, I wouldn't do it.
 
Jim K said:
Flew to my neighboring airport yesterday afternoon. I expected to be departing before dark, but wound up not getting back to the plane until 5:30 (I hate winter). Did a brief pre-flight, and found that there was already a light coating of frost on it.

I would say it felt like maybe 400-600 grit sandpaper, and was thin enough to easily see through. I remembered reading in the PHAK how I'd instantly die a fiery death if I attempted takeoff with frost on the wings, but I reasoned that it didn't seem worse than the film of dust on the wings (airplane needs a bath) when I left home, I was 200lb under max gross, and I had an 8000' runway. If she didn't want to rotate & climb like normal, I should still have a mile to put her back down.

Everything went as expected. So.... how do I tell how much frost is an issue? Did I make a poor decision and get away with it? If so, I'd like to know so I'm not tempted to push further next time.
Click to expand...

Beware of the strong advice by guys with no experience!

The danger of too much frost is similar to other dangers like being over gross or out of CG. Getting airborne in ground effect works. Climbing out of ground effect may not. Having an abundance of power helps, and my frost pirep is in airplanes with lots of power, especially in cold air. Taking off a long runway toward no obstacles is different than taking off a short strip surrounded by obstacles and rising terrain. Judgement comes from experience. Experience comes from good judgement.
 
Good to remember accidents are usually 2-3-4 things stitched together causing calamity. Wonky mixture control not good, but likely no issue. Over weight or forward CG, not good but it happens.

Add frost to any one or two of the above, and fate is severely tempted.

It’s the risk taken with the unknown lurking is why many pilots steer clear of any risk in the first place.
 
My crew has a weekly photo mission that we are devoted to like the Pony Express. Frost is a no-go based on our experience to date in West Texas where it can get mighty frosty.
 
Luigi said:
I knew a CFI once that while teaching would routinely tell his students that they could safely take off with frost as long as they "polished it", i.e. smoothed the rough surface with a piece of rope, or something similar. That practice was discontinued when he and a student ended up in a river off the departure end of the runway. Fortunately they both survived with minor injuries.
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If it was cold enough for frost to form then that must have been an awfully chilly swim in the river. Wonder if there were any aftereffects from hypothermia?
 
Ryanb said:
Reg:

§91.527 Operating in icing conditions.

(a) No pilot may take off an airplane that has frost, ice, or snow adhering to any propeller, windshield, stabilizing or control surface; to a powerplant installation; or to an airspeed, altimeter, rate of climb, or flight attitude instrument system or wing, except that takeoffs may be made with frost under the wing in the area of the fuel tanks if authorized by the FAA.
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Pretty sure he's not flying...

Subpart F—Large and Turbine-Powered Multiengine Airplanes and Fractional Ownership Program Aircraft
 
EdFred said:
Pretty sure he's not flying...

Subpart F—Large and Turbine-Powered Multiengine Airplanes and Fractional Ownership Program Aircraft
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Reference my post above :
Ryanb said:
Some aircraft are prohibited under 91 Subpart F from polishing frost smooth - they must remove all of it prior to takeoff. Even though our light GA airplanes don't fall under this rule, it only makes sense to comply with it. Our wings are just as susceptible to the reduction in lift and increase in drag caused by ice and frost
Click to expand...
 
Ryanb said:
First off, this was a very dumb move. Do not attempt that again! You should definitely not attempt flight if there is frost on the windows that would affect visibility, or on any of the wings or flight control surfaces.

An FAA bulletin on this topic says “frost the size of a grain of salt, distributed as sparsely as one per square centimeter over a wing's upper surface, can destroy enough lift to prevent the airplane from taking off.” Continuing to just forego what you’ve been told about frost, will likely make you a statistic one day, sorry to be so blunt.

Some aircraft are prohibited under 91 Subpart F from polishing frost smooth - they must remove all of it prior to takeoff. Even though our light GA airplanes don't fall under this rule, it only makes sense to comply with it. Our wings are just as susceptible to the reduction in lift and increase in drag caused by ice and frost.
Click to expand...

Actually the wings on most legacy light GA aircraft are not as susceptible, but if you think they are ask yourself why you see so few Aztecs and Barons with any ice protection and about every SR22 you will see has it.
 
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Can I have a raise of hands for anyone who has actually experienced the difference first hand of taking off with some frost on the wings? Because I only have enough C150 experience and I can tell that a little frost does not make much difference at all. Much less than the difference a hot day makes. So while I am not saying that it is safe for you to take off with a little frost, I know that some light frost, knocked down with my glove, on my wings is less concerning that that 95-100 degree day in the summer.

Our club president looked over two weeks ago and questioned me about going flying - Frost! wow, are you sure? This coming from a guy with 15,000+ hours, recently retired American captain, and owner of a Stearman. But also little experience flying an old Cessna in winter. His thinking was all about the hours on the 757, laminar flow wings, and OPS procedures prohibiting flying with any frost. I am just a low time pilot, but I few through the winter and had better performance with some light frost than in the summer heat. I don't take it lightly, it is something to always look at and consider, just not quite the same way as an airliner due to the old rough wings of the old forgiving plane.
 
Keep in mind that if frost is still forming, polishing or removing it isn’t going to last very long, either.
 
Matthew Rogers said:
Can I have a raise of hands for anyone who has actually experienced the difference first hand of taking off with some frost on the wings? Because I only have enough C150 experience and I can tell that a little frost does not make much difference at all. Much less than the difference a hot day makes. So while I am not saying that it is safe for you to take off with a little frost, I know that some light frost, knocked down with my glove, on my wings is less concerning that that 95-100 degree day in the summer.

Our club president looked over two weeks ago and questioned me about going flying - Frost! wow, are you sure? This coming from a guy with 15,000+ hours, recently retired American captain, and owner of a Stearman. But also little experience flying an old Cessna in winter. His thinking was all about the hours on the 757, laminar flow wings, and OPS procedures prohibiting flying with any frost. I am just a low time pilot, but I few through the winter and had better performance with some light frost than in the summer heat. I don't take it lightly, it is something to always look at and consider, just not quite the same way as an airliner due to the old rough wings of the old forgiving plane.
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I've probably 100 hours in a C-150/152. About the same in C-172. I usually just got to the airport a little early. If I found frost, I just untied the plane and turned it so the sun would shine on it, go back inside, and have another up of coffee. By the time I came out, the frost was gone. No need to become a test pilot. It's probably fine, but I never felt the need to test the hypothesis.
 
timwinters said:
Plus the OP had 8000' freakin' feet of runway in front of him and a plan. Some folks really shouldn't even get out of bed in the morning.
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Depends on the conditions. If the plane is already frosted over and there is a potential for icing then that’s a no-go for me. Only time I encountered frost/snow was in Denver with 9000 feet of runway. But I also had my wife and a few days worth of luggage in a 160 hp 172. I swept off the snow and waited a few hours for the sun to do the rest.
 
Matthew Rogers said:
Ok, so I fly a 150. In the summer it flies and climbs like a sack of bricks if fully loaded. In the winter it climbs at full gross straight up like it is light as a feather (comparatively in both cases). I flew it all winter and certainly had frost on the wings with little to no degradation in performance. And certainly performance was better than anytime in summer.

Those wings are covered in screws, exposed rivers, rough paint, fuel caps, panel seams, and (not much on mine, but on a lot of others) ripples and bumps in the skin. I agree that laminar flow wings are affected, but the C150 wings are already far from smooth on a good day and a bit of frost that feels like 400-600 grit would make mine feel smoother than they are right now!

I do have a bottle of RV antifreeze that I spray or splash on the wings when the frost is real thick or if snow and ice get stuck. Works well and melts it all off quickly. But a patch or two here or there that I missed never made any difference.
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I’ll get your back on this one, but it depends on the airfoil. Cessnas are covered in warts and rivets and antennas, dust and mud and cow **** (in my case) and a little bit of frost is going to make the plane plummet out of the sky? Uh no. Have I ever flow with frost? Well, of course not, but I have heard my friiiiiend has and lived to tell about it.

On a different airfoil, though... Lancair? Cirrus?

No one should ever fly with frost on their wings. It’s not legal, first of all, but if you think frost the size of one grain of salt per square centimeter is going to result in a smoking crater with your average dirt and grime covered Cessna, you’re not sharing the same objective reality as I am.

But really, don’t mess with frost.
 
What the rules say, and what happens. . .yep, airfoil dependent. I flew 172s & 182s with big red stripes on top of the wings for some years; that part of the wing shed frost fast in the sun, and it worked out OK quite often, though frost was still on the white sections of the wings.

Some things are more important than others, in diffrent aircraft - 100 pounds over gross isn't nearly as critical as being out of CG range in older GA aircraft.
 
Man, flying around the Great Lakes all my life I had to make decisions about this a lot. It was an every day occurence in the winter. I don't have any solid advice to add here other than each case is unique. If the whole wing is contaminated, you need deice fluid or a warm hangar if it's ice or frost. Snow? A push broom, but be DAMN careful any metal parts don't scratch the plexiglass or even come close to the surface. Small areas? Rub off with your gloved hand. Don't forget to check the top of the stabilizer and elevator as well as the wings. A heated hangar is my best choice, but expect to pay big $$$ at any Jet Center. A garden sprayer for deice fluid is the economical choice if the job is not too big for one.
 
dtuuri said:
Snow? A push broom, but be DAMN careful any metal parts don't scratch the plexiglass or even come close to the surface.
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But...if it’s dry snow it’ll blow off, right?

(I happen to know the answer to that one, and it’s a resounding “Hell NO!”)
 
Part 135 used to allow polishing, and that worked for us. (still alive)

But if there was a heated hangar, we would put it in for an hour........load our pax in the hangar and be towed out for departure. When it is snowing, it is best to be quick on starting and departure. Should be ready for takeoff when the last red flag on the gyros is retracted.
 
Matthew Rogers said:
Can I have a raise of hands for anyone who has actually experienced the difference first hand of taking off with some frost on the wings? Because I only have enough C150 experience and I can tell that a little frost does not make much difference at all. Much less than the difference a hot day makes. So while I am not saying that it is safe for you to take off with a little frost, I know that some light frost, knocked down with my glove, on my wings is less concerning that that 95-100 degree day in the summer.

Our club president looked over two weeks ago and questioned me about going flying - Frost! wow, are you sure? This coming from a guy with 15,000+ hours, recently retired American captain, and owner of a Stearman. But also little experience flying an old Cessna in winter. His thinking was all about the hours on the 757, laminar flow wings, and OPS procedures prohibiting flying with any frost. I am just a low time pilot, but I few through the winter and had better performance with some light frost than in the summer heat. I don't take it lightly, it is something to always look at and consider, just not quite the same way as an airliner due to the old rough wings of the old forgiving plane.
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You might be right. After all many pilots fly with bugs on the wings in the summer. But the point is, it is not only against general advice, it is also against FAR 91.527. It is like many other things in aviation - dipping below minimums on an instrument approach, or tapping into your fuel reserve because you know you can stretch it to the next airport, or flying through a little bit of icing. If these become habits rather than exceptions, all it takes is one more thing to go wrong. If you flew through all winter with frost on the wings, then definitely this has become a habit. That 15,000 hour pilot didn't make it that far by taking unnecessary risks. Flying itself is a risky business, don't add more into the mix.
 
Get the frost off, don't be a dope. What works one day may not the next. Plus it's not legal to take off with contamination.

I've found that if you turn the airplane so that the frost areas are exposed to the sun, the frost melts within about 20 minutes. Frost on an airplane is a no go for me, mainly because it is so easy to fix.
 
PaulS said:
Get the frost off, don't be a dope. What works one day may not the next. Plus it's not legal to take off with contamination.

I've found that if you turn the airplane so that the frost areas are exposed to the sun, the frost melts within about 20 minutes. Frost on an airplane is a no go for me, mainly because it is so easy to fix.
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Exactly right. Some here seem to think you need significant experience testing this theory to see if it’s actually true before advising others not to attempt it. If you like to be a test pilot, then by all means...
 
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