Icing

[Arbiter419]

Yup, opening the whole can of worms.

I consider myself to be a fairly proficient instrument pilot. This winter is the first time I've had the chance to legally be faced with the proposition of ice. Two days ago, I was flying the 172 I rent at home from N79 to KBVI to sell my car for parts...damned thing let me sit 5 hours from home. Anyway, half the flight was IFR, I ended up filing a pop up around University Park because at that point it was marginal due to the flurrying snow showers. Anyway, beaver was, and was forecast to be VFR for my arrival. As I passed Butler, then Zelienople, they were both very VFR so I knew I had some outs behind me.

Long story short, 10 miles from the IAF, approach told me Beaver just issued a special information, overcast 600, visibility 1/2 mile, blowing snow, crosswind 10 gust 16. Told them I'd continue with the approach, it is a squall after all. By this point, I had picked up just a frosting of ice, first noticed it on the tires then the fuel overflow on the left wing. As I started the approach, I noticed a little more, then a little more. Somehow I did manage to make it in, I saw the runway just as I was about to bag it. The plows only had 50 feet of the 150 foot wide runway "plowed", and even that had about 2 inches of snow on it. Made a nice crosswind landing and tower had me roll to the end because that was the only turnoff they had plowed. From the end of the runway I could just barely make out the tower, so good timing I guess.

After I got out of the plane, I inspected to see just how much ice we'd picked up. I wish I'd taken a picture, but there was a little buildup on the first 6 or so inches on the innermost part of the prop blades, and a thin line along the leading edge of the wing, about 3/4" "tall" and no more than 1/4" thick.

So, the purpose of this thread...did I pick up what's classified as a trace amount? Light amount? Was it just a little impact ice? The airplane didn't feel different. I want to know all I can about ice. What does a light amount look like on an airplane? What does moderate ice look like?

Anything you folks have to offer, I'd love to hear about it. And I know, ice isn't something to mess around with. Especially in a 172 with no deice equipment.

Fly safe people.

 

[Ted]

It sounds like you had a trace ice encounter. On a 172, I'm not surprised that you didn't notice a difference. Planes that have the aerodynamics of a brick are usually not impacted as much by ice accumulation (read: Aztec). So you had good outs, and made it there fine. Good job.

That said, you and I live in roughly the same area, and this is where most of my ice experience is. In my experience, if you fly IFR when it's below freezing around here, you WILL get ice in some form or another. It'll typically start as soon as you enter the clouds at that freezing point, and it will continue until you get out of the clouds. How quickly it accumulates varies, but remember that an icing area that I go through in 10 minutes will take you 15 minutes to go through, assuming no wind.

Before I started flying de-iced planes, I took the advice of experienced pilots in the area and just stayed out of clouds when it was below freezing. That served me well, and now that I fly de-iced planes, I am glad that I did that. A 172 just doesn't have a lot of options if you get icing, and around here you're not looking at an easy descent below the clouds normally, plus a lot of places that you don't want to be forced to ditch a plane.

I know a number of people in the midwest fly in IMC in the winter and don't get icing there regularly, as opposed to my luck which is getting it always. I suspect that has to do with lack of mountains that push the air and moisture upwards here, as well as the lack of water. The worst icing I have gotten has always been flying over terrain (which, annoyingly, is the last place I want to ditch).

Be careful out there.

 

[TMetzinger]

The definitions of ice (trace, light, moderate, heavy) are textually the same, but they mean different things depending on the airplane and it's equipment.

I would call what you had light ice, but I can see Ted calling it trace. To me, when it gets beyond the frost stage in an airplane without any de-ice, I call it light. Moderate is when I get an airspeed drop of more than 10% to maintain altitude, and I'm ready to use the E-word to get a route, altitude change.

So far I've never hit heavy.

A really interesting discussion at http://www.tc.faa.gov/its/worldpac/techrpt/ar01-91.pdf

 

[Everskyward]

The definitions of ice (trace, light, moderate, heavy) are textually the same, but they mean different things depending on the airplane and it's equipment.

Also keep in mind that in some airplanes you can't see many unprotected surfaces. We can only see the heated wings and the windshield. Only a small strip of the windshield is not heated. If ATC asks for a PIREP and I can see small particles of ice on the strip I'll call it light. But there is no accurate way to tell.

 

[olasek]

TTo me, when it gets beyond the frost stage in an airplane without any de-ice, I call it light.

So Tim, asuming you fly aircraft with no de-ice, how worry you should be when picking up more and more frost and how quickly you should contemplate some change of plans, perhaps a 180 degree turn when it is impractical to go lower? (I will read the doc.)

 

[Ted]

The definitions of ice (trace, light, moderate, heavy) are textually the same, but they mean different things depending on the airplane and it's equipment.

Well, although the same icing conditions will have a different result depending on airframe (i.e. Lancair will handle ice much worse than a 172), the resulting PIREPs should be the same.

Typically what I see happen is a 172 or 182 (some plane with no de-ice at all) reporting severe icing. Then I see another PIREP right next to it of something that has de-ice reporting light. My guess is the former is the pilot panicing, and the latter is realistic.

I would call what you had light ice, but I can see Ted calling it trace. To me, when it gets beyond the frost stage in an airplane without any de-ice, I call it light.

I'm basing it mostly on the estimated amount of time he was exposed to ice and the amount he reported. What I look at is the accretion rate.

Moderate is when I get an airspeed drop of more than 10% to maintain altitude, and I'm ready to use the E-word to get a route, altitude change.

If you're in trace icing for an hour (because you decided it wasn't anything to worry about) and end up building up enough to create what you are now defining as moderate icing, it doesn't mean you're in moderate icing. It means that you were in trace icing, and didn't do anything about it.

Hence why I look at accretion, not total for my PIREPs and describing the kind of ice.

Now, the total is what actually impacts aircraft performance, and what you need to work with.

 

[flyersfan31]

As far as I know, there are no awards issued for flying into icing.

I have a FIKI turboprop, and my spidey-senses still start tingling any time I hear a report of ice. I've never seen more than what I would consider light icing. Hit it once in a T182T and really noticed performance degradation - just kept losing airspeed. Went down to get out of it.

If I think it might be in the area, I start thinking of options.
If I start getting traces of ice, I start acting on those options.
If I hear there is liquid precip in near-freezing conditions, I stay on the ground.

My personal opinion is that I would be nervous in anything less than a jet transport in anything more than light icing. I've heard one too many horror stories about rapid ice accumulation.

 

[AcroBoy]

I seem to recall that the icing terms refer to the rate of accretion, and not the amount.

 

[poadeleted20]

All that stuff in the AIM about more than 60 minutes or less than 60 minutes is too subjective to matter very much. From a practical standpoint, the four levels of icing don't have much meaning except in a FIKI-certified plane. In an unprotected plane, they all mean about the same thing -- stop what you're doing and get somewheree that there isn't any icing. Think in those terms, and you will live long prosper.

 

[Fearless Tower]

From a practical standpoint, the four levels of icing don't have much meaning except in a FIKI-certified plane. In an unprotected plane, they all mean about the same thing -- stop what you're doing and get somewheree that there isn't any icing. Think in those terms, and you will live long prosper.

That's pretty much the way it has been explained to me - that the different levels of icing are dependent on the ability of the FIKI equipment to handle it.

If you don't have FIKI....you shouldn't be there.

 

[denverpilot]

Also keep in mind that in some airplanes you can't see many unprotected surfaces. We can only see the heated wings and the windshield. Only a small strip of the windshield is not heated. If ATC asks for a PIREP and I can see small particles of ice on the strip I'll call it light. But there is no accurate way to tell.

I pointed out the "ice light" on the engine nacelle (pointed at the wing) on the Metroliner the other day to a non-pilot who was with us for the "airplane tour".

He was a little surprised that it was such a simple device but quite critical to the safety of a flight in known icing on that aircraft.

Can't see it, can't tell if the boots are working, etc.

 

[TMetzinger]

Well, although the same icing conditions will have a different result depending on airframe (i.e. Lancair will handle ice much worse than a 172), the resulting PIREPs should be the same.

Typically what I see happen is a 172 or 182 (some plane with no de-ice at all) reporting severe icing. Then I see another PIREP right next to it of something that has de-ice reporting light. My guess is the former is the pilot panicing, and the latter is realistic.



I'm basing it mostly on the estimated amount of time he was exposed to ice and the amount he reported. What I look at is the accretion rate.



If you're in trace icing for an hour (because you decided it wasn't anything to worry about) and end up building up enough to create what you are now defining as moderate icing, it doesn't mean you're in moderate icing. It means that you were in trace icing, and didn't do anything about it.

Hence why I look at accretion, not total for my PIREPs and describing the kind of ice.

Now, the total is what actually impacts aircraft performance, and what you need to work with.

I look at accretion too, and if I lose 10% of airspeed in 5 minutes of icing, that's moderate. If I'm in icing conditions for an hour in a NON-FIKI airplane, I'm an idiot.

When I get ice, ANY ice, in a NON-FIKI airplane, I start my "out" decision and the dialogue with ATC. I report I'm getting a trace/light/whatever, and ask for higher/lower/left/right/etc based on what I have planned my escape route to be. Sometimes I've had to wait as long as 20 minutes. Once I declared an emergency and started my descent earlier than ATC would have liked. In all cases I could tell ATC wanted to get me out of the situation, in all cases I did get out of the situation, and in no case was there ever any repercussion from the FAA.

In the OP's situation, once starting the approach I think continuing and landing was the best choice. But I probably would have diverted or asked to hold, before reaching the IAF, since the weather report given would lead me to suspect icing on the approach. That to me could make the approach a "must land" situation, and I'd rather avoid them. Just something to consider, this is NOT an attack, hindsight is 20/20. But if we can apply 20/20 hindsight to the things we do and that others do, maybe we'll be able to recognize a similar situation in the future and make better choices as a result.

 

[Ted]

I look at accretion too, and if I lose 10% of airspeed in 5 minutes of icing, that's moderate. If I'm in icing conditions for an hour in a NON-FIKI airplane, I'm an idiot.

Agreed.

When I get ice, ANY ice, in a NON-FIKI airplane, I start my "out" decision and the dialogue with ATC. I report I'm getting a trace/light/whatever, and ask for higher/lower/left/right/etc based on what I have planned my escape route to be. Sometimes I've had to wait as long as 20 minutes. Once I declared an emergency and started my descent earlier than ATC would have liked. In all cases I could tell ATC wanted to get me out of the situation, in all cases I did get out of the situation, and in no case was there ever any repercussion from the FAA.

True, but you did have an interruption in the system to some degree (perhaps you just annoyed the controller) because you flew into conditions with an aircraft not properly equipped for the situation. I never take off with a plan of action for the flight of "declare an emergency" based on conditions I know exist. We all should be prepared to do so, but if you're taking off into icing conditions in an aircraft not properly equipped, you're basically setting yourself up for it.

Not an attack, just my opinion.

In the OP's situation, once starting the approach I think continuing and landing was the best choice. But I probably would have diverted or asked to hold, before reaching the IAF, since the weather report given would lead me to suspect icing on the approach. That to me could make the approach a "must land" situation, and I'd rather avoid them.

The problem is that you're then holding in icing conditions, and prolonging the situation. Think of it like having an engine failure in a twin that can still fly on one engine. Yes, holding is an option. Yes, doing a missed approach is an option. But there are very few instances when I would do either.

 

[TMetzinger]

Agreed.



True, but you did have an interruption in the system to some degree (perhaps you just annoyed the controller) because you flew into conditions with an aircraft not properly equipped for the situation. I never take off with a plan of action for the flight of "declare an emergency" based on conditions I know exist. We all should be prepared to do so, but if you're taking off into icing conditions in an aircraft not properly equipped, you're basically setting yourself up for it.

Not an attack, just my opinion.



The problem is that you're then holding in icing conditions, and prolonging the situation. Think of it like having an engine failure in a twin that can still fly on one engine. Yes, holding is an option. Yes, doing a missed approach is an option. But there are very few instances when I would do either.

Well I didn't give all the details about my declaring. Suffice it to say that I'd asked for an altitude change as soon as I picked up icing, and when ATC wouldn't give it to me right away I picked an airspeed that would be my limit, and when I hit that limit about 6 miles earlier than ATC told me to expect the descent, I declared and descended. No complaints or anything from ATC and he didn't have to alter any other airplane flight paths.

For your second point, I wasn't advocating holding in icing conditions (that's REALLY stupid in a non-fiki plane, and as we saw at Roselawn it's not always a good idea in a fiki plane either). I got the impression from the OP that he was not yet in icing conditions at that point, but only got into them during the approach. My point was that the weather at the airport would lead me to worry about icing on the approach itself, and since it seemed to be localized, if I was not in icing where I was, I'd either divert or ask to hold somewhere ice-free and let the squall blow by.

Things that are clear to the author when he writes are not always clear to the reader when he reads.

 

[AcroBoy]

The op asked if the amount he had accumulated was "trace". The correct answer is that the definitions are determined by the rate of accretion, not the amount.


The wisdom and judgement issues are separate questions, and the rest is all pontificating by "experts".

 

[TMetzinger]

The op asked if the amount he had accumulated was "trace". The correct answer is that the definitions are determined by the rate of accretion, not the amount.


The wisdom and judgement issues are separate questions, and the rest is all pontificating by "experts".

I don't intend to pontificate. It's laying out your thought process in the hope that you may learn something from others on the basis of their response, and perhaps others may learn something from you.

I'm glad for Ted's opinions as he's got LOTS of experience flying airplanes that I think of as "barely-FIKI" when compared to transport planes in cold clouds safely.

I don't consider myself an expert, but I've flown non-FIKI piston singles in clouds, I've gotten ice on them, and I've managed the encounters successfully. If hearing about those experiences helps someone who's never picked up any ice ever, great.

I know my first winter as an IFR pilot I was so afraid of icing I didn't fly in clouds at all. But I had a chat with a CFII I respected and we went flying on a cold day, and he taught me things about planning ahead and managing an inadvertent ice encounter. Beats the heck out of having no plan at all doesn't it?

 

[AcroBoy]

Wasn't pointing to any specific responder, just the general trend and tone of a lot responses.

 

[olasek]

Wasn't pointing to any specific responder, just the general trend and tone of a lot responses.

I think the general trend is very informative, I am learning a lot just reading the stuff, I thank our resident experts for all the bits of wisdom in this important area in GA.

 

[gismo]

After I got out of the plane, I inspected to see just how much ice we'd picked up. I wish I'd taken a picture, but there was a little buildup on the first 6 or so inches on the innermost part of the prop blades, and a thin line along the leading edge of the wing, about 3/4" "tall" and no more than 1/4" thick.

So, the purpose of this thread...did I pick up what's classified as a trace amount? Light amount? Was it just a little impact ice? The airplane didn't feel different. I want to know all I can about ice. What does a light amount look like on an airplane? What does moderate ice look like?

Anything you folks have to offer, I'd love to hear about it. And I know, ice isn't something to mess around with. Especially in a 172 with no deice equipment.

Fly safe people.

First of all, the different levels of ice accretion are based on the rate of accumulation, not the amount on the leading edges in flight or after landing. Based on the time I'm guessing you were in icing conditions, the rate you experienced would qualify as "Light Icing". Trace icing means the ice isn't getting thicker, it's sublimating as fast as it adheres.

Moderate icing implies that it's building fast enough that activating the deice equipment periodically (e.g. every few minutes) is necessary to prevent a buildup on the protected surfaces. Severe is when the ice is building so fast that the maximum effort deice operation can't keep up. So technically once it gets beyond "trace" it becomes severe on any airplane that has nothing but pitot heat to shed ice.

It's also widely accepted that relatively fat wings suffer less loss when coated with the same amount of ice than thin ones (and ironically, thin ones accumulate ice faster). "Laminar flow" wings like those on some high performance composite airplanes (e.g. Lancair) typically suffer significantly greater performance losses with small amounts of ice than less slippery designs.

 

[Everskyward]

I pointed out the "ice light" on the engine nacelle (pointed at the wing) on the Metroliner the other day to a non-pilot who was with us for the "airplane tour".

He was a little surprised that it was such a simple device but quite critical to the safety of a flight in known icing on that aircraft.

Can't see it, can't tell if the boots are working, etc.

It beats a flashlight!

 

[LearDriver]

Did your experience leave you feeling like you would want to repeat it again or not make that mistake again?

 

[Ted]

I'm glad for Ted's opinions as he's got LOTS of experience flying airplanes that I think of as "barely-FIKI" when compared to transport planes in cold clouds safely.

I'd agree with the "barely-FIKI" assessment. You have neither the equipment to shed it very well (think hot wings if you really want that), nor the power to get out of situations very quickly.

As with anything, the key comes to knowing your equipment and your plane, and planning accordingly. I've had good success with the Aztec, 310, and Navajo. Each plane has its strengths and weaknesses when dealing with icing, and as such my planning for the Aztec would be different than the 310 would be different than the Navajo (potentially).

 

[flyingmoose]

I'd agree with the "barely-FIKI" assessment. You have neither the equipment to shed it very well (think hot wings if you really want that), nor the power to get out of situations very quickly.

As with anything, the key comes to knowing your equipment and your plane, and planning accordingly. I've had good success with the Aztec, 310, and Navajo. Each plane has its strengths and weaknesses when dealing with icing, and as such my planning for the Aztec would be different than the 310 would be different than the Navajo (potentially).

What exactly would you plan differently between the models?

 

[Ted]

What exactly would you plan differently between the models?

The full details of that would require a lot more detail, but here's the summary:

Primarily it has to do with what level of expected icing I'm willing to tolerate (i.e. accretion rate) and also what my planned mode of action is are. The Aztec can carry ice very well, but can't climb through it well (less power), and doesn't like as high of altitudes. It also sheds ice the best out of the three (at least for the particular ones I fly). So, I need to plan a route through that will keep me at lower altitudes.

The 310 can't carry the ice as well, but has more power and likes higher altitudes better, so it can climb through ice better, and keep doing so. Therefore, I can plan a higher-altitude route. But I better be able to get on top of it, since I run out of power (and thus climb) as I go higher, and it won't tolerate building up ice very well. Keep in mind the 310 I fly has the Colemill conversion that gives it IO-520-Es rated at 300 hp a side (285 hp continuous).

The Navajo has a more consistent climb rate (turbos), but not as good of a climb rate as the 310. It carries ice somewhere between the Aztec and the 310, a bit closer to the 310. So I'll plan for it more or less similarly to the 310, although I can keep my climb rate going (or at least the power), which gives me some more options.

A turbo Aztec would be a nice option for dealing with ice, doubly so if it could have 300 hp TIO-540s or TSIO-520s. My friend's RAM T310R with the 335 HP TSIO-520s is a very nice package for, well, most weather.

 

[BillTIZ]

Ok, I've read all the ice information. But let's get back to the OP about, "picking up ice on the fuel overflow" on the left wing.

It's not really an overflow, although fuel will leak from there. There is a check valve. It is designed to let air into the tanks. It is supposed to be tucked behind the wing strut to protect it from icing over. If you got ice on it, then it may not be properly positioned. Have your mechanic check it's positioning.

If it ices over and blocks the air flow, you might find the engine getting deathly quiet before you get to MDA. No air into the tank, a vacuum develops in the tank that can decrease or stop fuel flow to the engine.

 

[Arbiter419]

Thank you everyone for the replies...I apologize for the late response, I just got moved into a new place out at school. Living with my own kind now...pilots.

Anyway, I perfectly understand that the general consensus is to stay the hell out of the stuff, especially in the stuff I'm flying now. I love discussions like this because I pick up so much out of it. Still not done digesting it. Again, thank you.

Ok, I've read all the ice information. But let's get back to the OP about, "picking up ice on the fuel overflow" on the left wing.

It's not really an overflow, although fuel will leak from there. There is a check valve. It is designed to let air into the tanks. It is supposed to be tucked behind the wing strut to protect it from icing over. If you got ice on it, then it may not be properly positioned. Have your mechanic check it's positioning.

If it ices over and blocks the air flow, you might find the engine getting deathly quiet before you get to MDA. No air into the tank, a vacuum develops in the tank that can decrease or stop fuel flow to the engine.

Hmm...interesting. I was always under the impression that valve was there to relieve pressure from the tank when cooler fuel is pumped from underground into a comparatively hot wing to keep stuff from busting when the fuel expands. I thought the holes in the top of the fuel caps replaced burnt fuel with air as the fuel levels go down. I'm trying to find a picture, I'm pretty sure we're talking about the same thing. It's farther outboard on the wing than the pitot tube, tucked in right about where the strut attaches to the wing.

 

[TMetzinger]

Thank you everyone for the replies...I apologize for the late response, I just got moved into a new place out at school. Living with my own kind now...pilots.

Anyway, I perfectly understand that the general consensus is to stay the hell out of the stuff, especially in the stuff I'm flying now. I love discussions like this because I pick up so much out of it. Still not done digesting it. Again, thank you.



Hmm...interesting. I was always under the impression that valve was there to relieve pressure from the tank when cooler fuel is pumped from underground into a comparatively hot wing to keep stuff from busting when the fuel expands. I thought the holes in the top of the fuel caps replaced burnt fuel with air as the fuel levels go down. I'm trying to find a picture, I'm pretty sure we're talking about the same thing. It's farther outboard on the wing than the pitot tube, tucked in right about where the strut attaches to the wing.

I think that's the vent, not a check valve (which implies it permits a one-way flow), and it basically is a standpipe up into the wing at a level that's higher than full fuel, but still allows air to flow. When fuel is drawn into the engine the vent allows air into the tank (they're cross connected so one vent is sufficient) to replace the volume of fuel burned. When fuel expands (fill up cold and let the wing warm) the vent allows the fuel to go overboard rather than let pressure build up in the tank.

Either way, if it's blocked, it's bad.

 

[BillTIZ]

I had a fuel flow starvation loss of power on takeoff with a dead stick emergency landing back on the airport, opposite direction. T-41B, which follows closely to the standard Cessna fuel system. Part of the tech order trouble shooting included testing the valve in the tank vent system, yes that tube tucked behind the wing strut, left side. Also part of the tech order was measure to check the proper placement behind the strut to protect it from icing and other airflow contamination.

We eventually found that the fuel strainer drain pin was not properly seating. It would seat and no drips, but at full power fuel flow on takeoff, fuel injected 210HP, the drain pin would unseat and allow air to be sucked into the fuel system and starve the engine.

 

[denverpilot]

The under-wing tube vents on Cessna singles are the primary way to replace the volume of fuel burnt with an equal volume of air. Some systems have one vent and cross-over vents between left and right. Others have two vents, and still have cross-overs.

They have a check valve in them at the top to supposedly keep them from leaking when the tank is full. There's a pinhole vent in that check valve that allows for cold fuel expansion, but because of the siphoning effect of surface tension, they'll run like drains if there is a static pressure pushing fuel from one wing to another -- typically parked on an unlevel surface with one wing higher than the other. This the POH admonition to place the fuel selector valve in a position other than Both when on the ground.

Unfortunately through a bunch of design changes to try to get fuel to feed evenly from both tanks on the Both setting, Cessna employed so many cross-vents and flows that it's impossible to completely stop fuel from flowing between the left and right tanks when fuller than the top of the upper interconnecting vent line.

Thus, after a top-off if you park the airplane on a non-level surface, it'll siphon off fuel until there's a static suction in the tanks of a very low value. Unfortunately...

Now on to the fuel caps. The caps have a soft seal valve in them in case of a blockage of the one or two vent ports.

They're intended to be sucked inward if a tank is feeding the engine and the main air vent is also plugged. (Ice, bug, failed check valve, whatever...)

Especially important that they work in that case or the suction/vacuum in the tank will starve the engine of fuel.

Back to the leaking/siphoning problem. Many fuel caps are neglected. The $4 rubber gasket vent is loose and lots of air can get in. It doesn't take much suction to open the valve/rubber.

In this "slightly bad" condition, the caps still do their job but they're also leaking air in and contributing to the vent fuel leak on the ground.

They're probably not letting in air during flight at this stage because the real vent under the wing creates positive pressure in both tanks with ram air and seals them shut from below.

In the fully-failed state, they blow out and the positive pressure in the tanks from the vent and the lower pressure on top of the wing conspire to suck the fuel right out of the hole in the gas cap in flight.

It'll drain most of a tank pretty quick.

Gravity will win for some of the fuel but if you don't notice the streamer of fuel behind you and don't check your admittedly poor fuel gauges in flight, you could be in for a nasty surprise.

It's a $5 fix that gets overlooked by far too many people and bites them. The lucky ones wonder where the blue streaks on top of the wing came from and why their fuel flow calculations are off.

 

[TMetzinger]

<snip>
In the fully-failed state, they blow out and the positive pressure in the tanks from the vent and the lower pressure on top of the wing conspire to suck the fuel right out of the hole in the gas cap in flight.

It'll drain most of a tank pretty quick.

Gravity will win for some of the fuel but if you don't notice the streamer of fuel behind you and don't check your admittedly poor fuel gauges in flight, you could be in for a nasty surprise.

It's a $5 fix that gets overlooked by far too many people and bites them. The lucky ones wonder where the blue streaks on top of the wing came from and why their fuel flow calculations are off.

Thats one of the scenarios I use with folks in MSFS... They go flying along and I use the instructor console to reduce their fuel, simulating an overwing leak. Since the scenario already had them close to minimums to start, if they don't catch the situation their airplane will go silent. They sure start paying more attention to crosschecking the fuel gauges with their flight progress after that scenario!

This is also a situation where a totalizer/fuel-flow meter won't detect the error, as the fuel is not passing through it, it's going overboard.

 

[denverpilot]

This is also a situation where a totalizer/fuel-flow meter won't detect the error, as the fuel is not passing through it, it's going overboard.

Damn. I never thought of that. Insidious!

 

[TMetzinger]

Damn. I never thought of that. Insidious!

Yep, even on the super-duper G1000, trust, but verify. I've seen cases where the totalizer was set for full fuel but the airplane was filled to the tabs, and the range ring showed a circle that was too big.

If we put in decent fuel level sensing systems, then something like the G1000 could alert if there was a big discrepancy between the fuel level sensed and the amount in the totalizer. It would nag to to set the totalizer after refueling, and if you sprung a leak inflight.

 

[flyingcheesehead]

Ok, I've read all the ice information. But let's get back to the OP about, "picking up ice on the fuel overflow" on the left wing.

It's not really an overflow, although fuel will leak from there. There is a check valve. It is designed to let air into the tanks. It is supposed to be tucked behind the wing strut to protect it from icing over. If you got ice on it, then it may not be properly positioned. Have your mechanic check it's positioning.

If it ices over and blocks the air flow, you might find the engine getting deathly quiet before you get to MDA. No air into the tank, a vacuum develops in the tank that can decrease or stop fuel flow to the engine.

Reading the OP, I didn't take it to mean that the hole on the vent tube was iced over, but that the front of the vertical part of the tube was. Since it's one of the smallest-diameter curves visible outside on a Cessna, it's a great place to look for ice buildup.

 

[Arbiter419]

Reading the OP, I didn't take it to mean that the hole on the vent tube was iced over, but that the front of the vertical part of the tube was. Since it's one of the smallest-diameter curves visible outside on a Cessna, it's a great place to look for ice buildup.

Absolutely correct. I didn't notice any buildup on the actual hole, just the leading edge of the vertical part.

 

[BillTIZ]

Absolutely correct. I didn't notice any buildup on the actual hole, just the leading edge of the vertical part.

And how do you know the inside diameter of the tube was not constricted or obstructed from ice that forms on the back inside bend of a tube?

 

[gismo]

And how do you know the inside diameter of the tube was not constricted or obstructed from ice that forms on the back inside bend of a tube?

I had that happen once in a Bonanza when I was flying in trace icing for a couple hours. Total accumulation on the leading edges was less than 1/4 inch but the left main tank vent plugged up completely including the bleed hole in the back of the bend.