How much frost...

[bflynn]

OP, you need to add the title "Test Pilot" to your resume.

The problem is that you took the first step in creeping toward the unknown edge of the envelope. You did it and you got away with it. if you keep going, one day you'll find that you have just enough lift to fly to the scene of the crash.

On top of which, it is illegal for a reason, the rule was written because someone died doing what you did.

 

[MauleSkinner]

On top of which, it is illegal for a reason...

Got a reg reference for that? The one that was posted previously doesn’t apply.

 

[Cap'n Jack]

I didn't think you could over load a Caravan..

Looks like frost in Juneau. Boy it can really get thick.

It looks like frost, but it was really what we describe as icing. It was deposited by visible moisture, not the deposition process which forms normal frost.

 

[kayoh190]

By the way, how do commercial airliners know whether there is ice or not? I saw a pirep the other day near Flagstaff of s A320 reporting moderate time at 14000

Generally we initially see it on the windshield wipers, and as it gets worse we'll see it begin to build on the outer edges of the windshield as well.

 

[bflynn]

Got a reg reference for that? The one that was posted previously doesn’t apply.

AC 91-74. Disregarding would be careless and reckless at a minimum.

Also, the FAA considers high relative humidity + freezing conditions to be "known icing". If your termperature/dewpoint spread is 0/0, such as when frost is forming, then you have known icing conditions. Flying with frost is 91.9, 91.13 and 91.103 according to the FAA's Bell letter. https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/data/interps/2009/bell - (2009) legal interpretation.pdf

Unrelated - Why do they call it reckless? Seems wreck-ful would be a better word.

 

[PaulS]

This seems to be the thought process by many, but I would argue while true with structural icing, it's just not the case with frost. The condition exists on the ground. You accelerate the airplane and see if it rotates and flies as normal. If not, you set it back down-unless you took off from a very short runway, which is the case in most of the accidents, or you panick and try to force it to fly when it doesn't want to, which pretty much covers the rest.

I don't disagree with the sentiment that you should clean the wing completely. Without getting too far off in the weeds, I was already behind and my choices were scrape the wings with a credit card, or wait a couple hours for the line guys to finish turning a 737 and help me. I am well aware that narrative sounds hauntingly like the beginning of an ASI video, which is what spurred me to start this thread.

If the shape, weight, and smoothness of the wing are minimally changed, what makes frost different from paint? That's a genuine question. I just haven't found evidence or even a convincing argument that it's not a manageable risk with lots of runway and an understanding of how your aerodynamics may be effected. It's plausible that smooth frost might have a higher coefficient of friction than paint.

For what it's worth, by the time I got home the frost had sublimated off.

Why take any risk at all? That's a valid point. In my mind flying a piston single at night was by far the biggest risk I took.

Why take any risk at all? Exactly, or more to the point, why take any unnecessary risk at all? I'm convinced that many accidents result from not one off, had a bad day behavior, rather they result from continual behavior, that you really shouldn't be doing, but works out most of the time giving the pilot the dangerous behavior really is manageable until it finally bites him.

Frost covers a wide range of conditions, from what is a flash glaze, very thin and easy to remove, to almost snow like quality almost an eighth of inch thick and much more challenging to remove. The conditions run the gambit between those extremes and, I'm guessing here, the effect on lift generation runs the gambit too. The question is, where is the line between "acceptable" and "unacceptable"? There is only one way to find out, one poster said that light rime in flight and frost are essentially the same and the airplane doesn't stop flying in light rime, so it won't stop flying with frost. That's probably true, if the frost forms in cruise, where you have a much higher margin from stall than when taking off. But the problem in taking off, is that you are at full power, slow, with a high angle of attack. If you have enough runway to mitigate these factors, maybe you'll be ok taking off, or maybe not. Why take the chance?

Some here are convinced it's not an issue, whatever it's your life, hopefully you don't carry passengers while doing this. I'll just shake my head every time I hear about it.

BTW, the rough paint analogy, I'm not buying that, not even close.

 

[LongRoadBob]

Shure it will.

one of the first things I think I asked on this forum kinda fits in with this. If you as a pilot were a passenger in that plane, and saw that, knowing what you know, would you speak up? Demand to get off the plane?

 

[EdFred]

AC 91-74. Disregarding would be careless and reckless at a minimum.

Also, the FAA considers high relative humidity + freezing conditions to be "known icing". If your termperature/dewpoint spread is 0/0, such as when frost is forming, then you have known icing conditions. Flying with frost is 91.9, 91.13 and 91.103 according to the FAA's Bell letter. https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/data/interps/2009/bell - (2009) legal interpretation.pdf

Unrelated - Why do they call it reckless? Seems wreck-ful would be a better word.

ADVISORY circular, not REGULATORY circular. Also, the FAA has since changed their stance on known icing, so that Bell letter is out of date/superseded.

 

[MauleSkinner]

AC 91-74

Says nothing about it being illegal.

Also, the FAA considers high relative humidity + freezing conditions to be "known icing". If your termperature/dewpoint spread is 0/0, such as when frost is forming, then you have known icing conditions.

No, they do not. That was part of the interpretation mentioned in the first part of your link below as being rescinded.

Flying with frost is 91.9, 91.13 and 91.103 according to the FAA's Bell letter. https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/data/interps/2009/bell - (2009) legal interpretation.pdf

I see nothing in there about frost.

Yes, careless and reckless always applies, but “it’s illegal” is a fallacy.

 

[Jeff767]

The stall aoa would remain the same. The airspeed you need to maintain to stay below that aoa becomes the question. A 10% increase in stall speed in my plane would be 5 knots...

The stalling AOA will not remain the same. Any change in airfoil shape will effect stalling AOA.

 

[steingar]

Says me if you have to ask...

 

[Jim K]

Frost does not change the basic aerodynamic shape of the wing,

The stalling AOA will not remain the same. Any change in airfoil shape will effect stalling AOA.

 

[Velocity173]

Generally we initially see it on the windshield wipers, and as it gets worse we'll see it begin to build on the outer edges of the windshield as well.

You all have an icing indicator in the cockpit?

 

[kayoh190]

You all have an icing indicator in the cockpit?

I've flown a couple planes with fancy ice detectors, but on my current bird we have a visual system installed called "The Bolt".

 

[Velocity173]

I've flown a couple planes with fancy ice detectors, but on my current bird we have a visual system installed called "The Bolt".

Ok. We had an ice rate meter on the Black Hawk. Wondered if you all have something similar.

 

[jordane93]

Ok. We had an ice rate meter on the Black Hawk. Wondered if you all have something similar.

We have an ice detector which detects different vibrations and that’s how it calculates if there’s ice buildup on the the probe. We get an EICAS message as well as amber illumination on our overhead panel when enough ice is detected and eventually goes away when enough the ice is shedded and it repeats the vibration cycle.

 

[Tantalum]

We have an ice detector which detects different vibrations and that’s how it calculates if there’s ice buildup on the the probe. We get an EICAS message as well as amber illumination on our overhead panel when enough ice is detected and eventually goes away when enough the ice is shedded and it repeats the vibration cycle.

Pretty interesting system, this is what the Avanti has

I just thought it was interesting that there was a pirep for moderate rime and was wondering how on Earth a commercial pilot would know to level of ice since those heated wings always seem super clean

 

[jordane93]

Pretty interesting system, this is what the Avanti has

I just thought it was interesting that there was a pirep for moderate rime and was wondering how on Earth a commercial pilot would know to level of ice since those heated wings always seem super clean

Like @kayoh190 said, we use our wipers or center window post as a representative surface to estimate the icing amount on our wings. We do have a procedure with deicing where if our holdover time is getting close to timing out, the FO will leave the flight deck and go to the exit row to inspect the wings!

 

[EdFred]

The stalling AOA will not remain the same. Any change in airfoil shape will effect stalling AOA.

Isn't a stall AoA almost always at around 17 degrees no matter the wing? The angle of incidence would vary based on airfoil shape.

 

[jspilot]

This seems to be the thought process by many, but I would argue while true with structural icing, it's just not the case with frost. The condition exists on the ground. You accelerate the airplane and see if it rotates and flies as normal. If not, you set it back down-unless you took off from a very short runway, which is the case in most of the accidents, or you panick and try to force it to fly when it doesn't want to, which pretty much covers the rest.

I don't disagree with the sentiment that you should clean the wing completely. Without getting too far off in the weeds, I was already behind and my choices were scrape the wings with a credit card, or wait a couple hours for the line guys to finish turning a 737 and help me. I am well aware that narrative sounds hauntingly like the beginning of an ASI video, which is what spurred me to start this thread.

If the shape, weight, and smoothness of the wing are minimally changed, what makes frost different from paint? That's a genuine question. I just haven't found evidence or even a convincing argument that it's not a manageable risk with lots of runway and an understanding of how your aerodynamics may be effected. It's plausible that smooth frost might have a higher coefficient of friction than paint.

For what it's worth, by the time I got home the frost had sublimated off.

Why take any risk at all? That's a valid point. In my mind flying a piston single at night was by far the biggest risk I took.

You may have a valid point about frost not changing much from an aerodynamic standpoint( especially limited amounts) but again, why take the chance. If the frost impacts the stall speed and lift of the wing, there is not a mathematical way to know by how much the speed is impacted. Therefore it becomes just a guess. Did the frost impact the speed by less than one knot, five knots? 10 knots?? who knows??? That's why I said frost is not the type of event you want to "guess and check with"

The FAA is overly cautious with it's guidelines. I'll agree with that but I just don't like the idea of people saying "well this regulation can be overlooked so then let's just ignore this one too." That's a slippery slope.

 

[nauga]

Isn't a stall AoA almost always at around 17 degrees no matter the wing? The angle of incidence would vary based on airfoil shape.

Depends on what you mean by "around" I suppose, but generally no, stall AOA depends largely on the shape and the condition of the airfoil and the wing. Incidence is a (usually) fixed geometric angle between the wing and some fuselage reference line.

Nauga,
tripped

 

[write-stuff]

I haven't tested one in a wind tunnel, but I'm pretty sure that the flat wing on a balsa glider toy reaches the critical AoA at much less than the "normal" 17ish degrees we see on most GA airplanes.

 

[Tantalum]

Funny... we hear so much about ice and frost... then you'll go rent a plane at a local mom and dad flight school and the amount of bugs and flaking paint you see on the wings plus those giant old school bolts and rivets it's funny to think that a sandpaper layer of frost will kill you

 

[dmspilot]

Isn't a stall AoA almost always at around 17 degrees no matter the wing? The angle of incidence would vary based on airfoil shape.

For popular airfoil designs I believe so. An airfoil with frost or ice is not a popular design.

 

[Velocity173]

We have an ice detector which detects different vibrations and that’s how it calculates if there’s ice buildup on the the probe. We get an EICAS message as well as amber illumination on our overhead panel when enough ice is detected and eventually goes away when enough the ice is shedded and it repeats the vibration cycle.

Ok. Sounds kinda similar to what we had. Basically a probe that detects and measures ice (trace, light, moderate, heavy) based on vibration. That measurement then works in conjunction with an OAT probe on the nose. The computer compares the two readings and decides how much heat to apply to the blades and how long.

 

[Sundancer]

OP, you need to add the title "Test Pilot" to your resume.

The problem is that you took the first step in creeping toward the unknown edge of the envelope. You did it and you got away with it. if you keep going, one day you'll find that you have just enough lift to fly to the scene of the crash.

On top of which, it is illegal for a reason, the rule was written because someone died doing what you did.

Yep, new rules are the best solution for accident prevention - or, maybe the OP has a brain, and isn't going to start down the inevitable slope to 'bad habits' based on a single occurrence of successful flight after noting minor frost on a wing that clearly handled it well. Geez, he might be smart enough to know he shouldn't apply that same evaluation to a different wing on a diffrent airplane, or accept just a little bit more frost the next time. Or start eating fatty food or take up smoking.

It bugs me that some, maybe most, people are inclined to make rules for other people; surely "we" wouldn't do dumb-ass things, or adopt bad habits, but someone else, those less-bright lights, need our oversight.

My take is dumb-asses aren't saved by ink stains, and the not so dumb-asses read the rules, then apply experience and common sense. But, instead, we get the FAA regs, written, in order of priority, to provide CYA for the FAA, give the FAA a hammer over pilots, and, lastly, bring some order to aviation. The third item is a lucky accident, and occurs as as unintended consequence of the first two.

I beleive someone who always obeys the rule is as big a fool as someone who always ignores them. Aviation, and the real world in general, are more complex than what can (or should) be articulated in regs.

Every pilot on this forum likely breaks a rule on every flight, for no other reason than movement in the physical universe isn't possible without doing so.

Before flaming: Yes, I know contaminated wings are serious. I also bet you all know it's a matter of degree, airfoil, ambient conditions, pilot experience, and other stuff that doesn't jump to mind right now. Rant complete.

 

[RyanB]

Look, my rationale on this whole event, was that I don't want to encourage the OP to think that because he got away with frosted wings once, he can do it again and again, which could ultimately lead to even worse decisions in the future. He had a few variables going for him on this instance, so it worked out, but implying that this sort of thing is 'no big deal' to a newly minted pilot just isn't a great idea.

 

[Sundancer]

And, the point is missed again. . .

 

[wsuffa]

The most horrifying element about ice in my experience has been how quickly it builds on the wings.. within a minute or two you can have a serious problem on your hands

It's even worse if you notice that you're picking up trace ice, and you're in C90 (Chicago Approach) territory. Sometimes they will have nowhere to put you (because they are determined to keep you out of the class B) even if you report icing and request a change. Going into ARR one night, I heard anothe guy on frequency asking and pleading for another altitude or turn to get out of icing. Approach kept telling him no. They handed him off before I heard the conclusion, but that would have been a time where the "E" word is your friend.

Dallas metroplex, approach, on the other hand is much much better at handling such stuff.

 

[Velocity173]

To me the the frost thing would be no different than if I decided to put grip tape all over the upper and lower surfaces of the wings and go fly to test the flight characteristics. I’d become a test pilot when there’s no reason to be a test pilot other than being lazy.

I clean bugs off the leading edge as well if they’ve gotten to be real bad. Especially on the canard. There have been a few cases of canards stalling at a much higher speed due to bug contamination. Most canards exhibit changes in lift just by going through rain. It’s also a proven fact that on rotor blades or windmill blades, bug contamination can significantly reduce performance. Basically, if there are enough bugs debris to simulate light rime ice, then why take off with it there?

 

[nauga]

To me the the frost thing would be no different than if I decided to put grip tape all over the upper and lower surfaces of the wings and go fly to test the flight characteristics.

Equally 'no different' as suggested in this thread would be a single 1/4" dot of grip tape close to the trailing edge at the root, maybe even on top of a protruding screw head. "The law (sic) says NO grip tape!" "Yer gonna DIE!"

I clean bugs off the leading edge as well if they’ve gotten to be real bad.

Smart move - but I don't think anyone is suggesting flying with frost is acceptable if "[it's] gotten to be real bad." If the only acceptable amount is "absolutely none" then what do you do about a single bug? A paint chip?

It wasn't all that long ago that canards were having issues with paint stripes close the the canard LE. Well, maybe it was exactly that long ago.

Nauga,
and the FUD walkdown

 

[dtuuri]

Wouldn't there be YouTube videos demonstrating the adverse effects of frost during wind tunnel tests if it supported the dire warnings? I can't find 'em if they're out there.

 

[nauga]

Wouldn't there be YouTube videos demonstrating the adverse effects of frost during wind tunnel tests if it supported the dire warnings?

Wind tunnel models often have leading edge grit or transition 'bumps' to trip laminar flow to turbulent to make it more representative of full-scale characteristics. You probably won't see any I'm familiar with on YouTube.

Nauga,
sanded

 

[danhagan]

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.

What you call west Texas, those of us IN west Texas call EAST or CENTRAL

I have absolutely ZERO experience with frost except cars left outside about 40 years ago ... we rarely get any here. The one time I thought I had it on a rental as a student as I approached, turned out to be dew ... so still zero experience.

 

[Matthew Rogers]

AC 91-74. Disregarding would be careless and reckless at a minimum.

Also, the FAA considers high relative humidity + freezing conditions to be "known icing". If your termperature/dewpoint spread is 0/0, such as when frost is forming, then you have known icing conditions. Flying with frost is 91.9, 91.13 and 91.103 according to the FAA's Bell letter. https://www.faa.gov/about/office_org/headquarters_offices/agc/practice_areas/regulations/interpretations/data/interps/2009/bell - (2009) legal interpretation.pdf

Unrelated - Why do they call it reckless? Seems wreck-ful would be a better word.

But what about most mornings, where the frost is already there, but no longer forming? Now there is no icing conditions, just blue sky and a solid dew point spread. This is the case in 99" of flights where you walk up to the plane and there is frost on the wings.

 

[RyanShort1]

What you call west Texas, those of us IN west Texas call EAST or CENTRAL

I have absolutely ZERO experience with frost except cars left outside about 40 years ago ... we rarely get any here. The one time I thought I had it on a rental as a student as I approached, turned out to be dew ... so still zero experience.

Borger, Boys Ranch, Amarillo, Lubbock, Midland, Wink, Orla are all places I'm in frequently, or semi-regularly. Many of those places I'm in every single week on photo missions. Don't get to El Paso as often as I'd like, but I'd still call them West Texas, and people I talk to at the FBO's call themselves West Texans, also.

 

[danhagan]

Don't get to El Paso as often as I'd like, but I'd still call them West Texas, and people I talk to at the FBO's call themselves West Texans, also.

Most of your list except Wink really aren't ... Midland Odessa is BARELY west Texas

 

[LongRoadBob]

This seems to be the thought process by many, but I would argue while true with structural icing, it's just not the case with frost. The condition exists on the ground. You accelerate the airplane and see if it rotates and flies as normal. If not, you set it back down-unless you took off from a very short runway, which is the case in most of the accidents, or you panick and try to force it to fly when it doesn't want to, which pretty much covers the rest.

I don't disagree with the sentiment that you should clean the wing completely. Without getting too far off in the weeds, I was already behind and my choices were scrape the wings with a credit card, or wait a couple hours for the line guys to finish turning a 737 and help me. I am well aware that narrative sounds hauntingly like the beginning of an ASI video, which is what spurred me to start this thread.

If the shape, weight, and smoothness of the wing are minimally changed, what makes frost different from paint? That's a genuine question. I just haven't found evidence or even a convincing argument that it's not a manageable risk with lots of runway and an understanding of how your aerodynamics may be effected. It's plausible that smooth frost might have a higher coefficient of friction than paint.

For what it's worth, by the time I got home the frost had sublimated off.

Why take any risk at all? That's a valid point. In my mind flying a piston single at night was by far the biggest risk I took.

I’m only guessing, theorizing, but the difference between paint and frost seems to me to be several.
Frost is a buildup which I think would be more susceptible to continuing to build up even after engine start and taxiing? Or even as you fly.
Paint is normally smooth and polished, and even when cracked isn’t as ragged as frost, which often covers a large expanse of the wing and leading edge. And should actually be repainted. Shouldn’t it? It degrades performance too doesn’t it, but it isn’t as irregular as frost buildup. Also frost has weight associated with it. The original paint was factored in, and the overall affect of it flossing off is it gets lighter not heavier.

Rivets (as some mention) are a necessary evil because of cost. And are stable...placed in rows, not covering the whole expanse. Also, are exaggerated even more by frost which turns a small river into a larger impediment. The airplane was tested with the rivers, not frost, for reliable airspeeds, vspeeds.

But what is the issue here? Shouldn’t a pilot be able to emo e the frost, as some have with anti freeze? Shouldn’t that be available and the time worth the effort?

Maybe it affects some types more than others, but also seems like people are focusing on normal flying, but if you get in a jam, where you need every bit of lift, that is when you’d want every factor in your favor.

 

[Tantalum]

continuing to build up

That's it.. and it builds up fast.. and unless you exit the conditions it's just going to keep building up. Trace -> 1/8th of an inch -> 1/4 inch -> 1/2 inch... etc. Next thing you know the plane stops flying and it's too late

 

[MauleSkinner]

That's it.. and it builds up fast.. and unless you exit the conditions it's just going to keep building up. Trace -> 1/8th of an inch -> 1/4 inch -> 1/2 inch... etc. Next thing you know the plane stops flying and it's too late

Frost is going to stop building when you fly. Ice can build on leading edges in flight, but conditions for frost are not related to in flight icing conditions.