Fly through rain/snow mix?

[CJones]

I've read/heard discussions about flying through snow and have actually flown through snow myself with no ill effects.

What about a rain/snow mix? IIRC, the caveat to flying through snow was if it was a 'dry' snow, it won't try to stick to the airframe. I don't consider rain/snow mix to be a 'dry' snow, but I also have never had problems flying through rain by itself. Obviously the temps aloft would be a major deciding factor, but is the rain mixed with snow considered to be supercooled droplets that will freeze on impact regardless of the ambient temp?

Discuss amongst yourselves...

Edit: For more 'situational based' discussion, I am considering a flight from Ames, Iowa (KAMW) to Muscatine, Iowa (KMUT) on Tuesday evening with a flight from Muscatine, Iowa (KMUT) to Peachtree City, GA (KFFC) early Wednesday morning. Forecasts at this point are saying rain/snow mix moving through Ames on Tuesday (http://www.intellicast.com/Local/Weather.aspx?location=USIA0026) and arriving in Muscatine on Wednesday (http://www.intellicast.com/Local/Weather.aspx?location=USIA0604).

 

[dmccormack]

My guess would be the probability of icing would most likely be high if you're flying at an altitude where there is snow (below 32) and rain (not necessarily above 32).

I've flown through snow. I've flown through rain.

I would assume around here (SW PA) a rain/snow mix would portend icing.

 

[taters]

I've read/heard discussions about flying through snow and have actually flown through snow myself with no ill effects.

What about a rain/snow mix? IIRC, the caveat to flying through snow was if it was a 'dry' snow, it won't try to stick to the airframe. I don't consider rain/snow mix to be a 'dry' snow, but I also have never had problems flying through rain by itself. Obviously the temps aloft would be a major deciding factor, but is the rain mixed with snow considered to be supercooled droplets that will freeze on impact regardless of the ambient temp?

Discuss amongst yourselves...

Edit: For more 'situational based' discussion, I am considering a flight from Ames, Iowa (KAMW) to Muscatine, Iowa (KMUT) on Tuesday evening with a flight from Muscatine, Iowa (KMUT) to Peachtree City, GA (KFFC) early Wednesday morning. Forecasts at this point are saying rain/snow mix moving through Ames on Tuesday (http://www.intellicast.com/Local/Weather.aspx?location=USIA0026) and arriving in Muscatine on Wednesday (http://www.intellicast.com/Local/Weather.aspx?location=USIA0604).

In my exp. the precip usually is either one or the other.... . I have really only seen the mix at or near the ground... SLD are "big" tiny cloud droplets that cannot be seen by the eye usually in clouds...so IMO that wouldnt count. If you are seeing a rain/snow mix that would tell me you are at an ambient temp above freezing but icing conditions are probably above. Good luck!

 

[Cap'n Jack]

What is the outside air temperature at the altitudes you will fly at? Will I need to climb or descend into freezing temperatures containing liquid precipitation?

If above freezing, the snow is melting into rain.

 

[gismo]

If above freezing, the snow is melting into rain.

That matches my experience with mixed snow/rain, it was always when the air temp was just above freezing, and I don't recall picking up ice in such situations. I believe that if conditions are ripe for freezing rain/drizzle (warmer rain falling into below freezing air) there's not much chance for snow to exist because the snow would have to form under the rain cloud i.e. in the rain. It might be possible to have snow inside a cloud that contains unfrozen water vapor but I'd expect the band of potential icing to be extremely narrow (vertically ) under those conditions.

 

[flyersfan31]

When I hear rain/snow mix, I think "cold, wet --- not friendly conditions."

I'm not afraid of a little ice encounter, I've been there, but I'm reaaaaaaaally cautious when the air is wet and close to freezing. SLD is a scary concept.

 

[Geico266]

If you have a carb, make sure you use your carb heat when flying in snow. We lost an RV-6 last year due to snow icing the aircleaner and no alt air. When the engine quits carb heat is worthless.

 

[Everskyward]

When I hear rain/snow mix, I think "cold, wet --- not friendly conditions."

I'm not afraid of a little ice encounter, I've been there, but I'm reaaaaaaaally cautious when the air is wet and close to freezing. SLD is a scary concept.

I'm with you here. In some airplanes yes, in a small unprotected airplane I don't think so. I think there are too many variables.

 

[gismo]

If you have a carb, make sure you use your carb heat when flying in snow. We lost an RV-6 last year due to snow icing the aircleaner and no alt air. When the engine quits carb heat is worthless.

Technically, if the problem is impact ice on the air filter, "carb heat" will help even if there's no "heat" since it provides an alternate path for the air bypassing the clogged filter. Of course if you don't have carb heat or alt air, you're in deep doo doo.

 

[Geico266]

Technically, if the problem is impact ice on the air filter, "carb heat" will help even if there's no "heat" since it provides an alternate path for the air bypassing the clogged filter. Of course if you don't have carb heat or alt air, you're in deep doo doo.

The point I'm trying to make is turn the carb heat on at the first sign of snow.

 

[twdeckard]

I have always considered fluffly snowflakes at the surface a reassuring sign, but snow pellets discourage me from flying. The former is based on limited experience, the latter on superstition and 9th grade science class.

I did once take off in the snow (and come right back) after contamination during the taxi/run-up didn't clear and I had a messy wing. The unusual thing was that the arrow had sat in a stone hanger with one wing exposed to the sun and must have been warm enough to pick up the snow and keep it.

 

[Everskyward]

The unusual thing was that the arrow had sat in a stone hanger with one wing exposed to the sun and must have been warm enough to pick up the snow and keep it.

This brings up a good point. You need to consider the skin temperature of the airplane when making some of these decisions. Out here where the snow is dry it's sometimes better to leave the airplane where it is cold so that when it you get a little snow it doesn't stick. On the other hand if you have it inside a heated hangar and bring it out in the snow, the snow will melt on the surface and refreeze as soon as the skin temperature gets below freezing.

 

[poadeleted20]

If you have a carb, make sure you use your carb heat when flying in snow. We lost an RV-6 last year due to snow icing the aircleaner and no alt air. When the engine quits carb heat is worthless.

...but if the reason the engine quit is an iced-over air filter, pulling the carb heat knob will bypass the filter and get you running again. Just beware of pulling the carb heat when you have no induction icing symptoms, as in snow, that can cause carb ice to form with no way to clear it.

 

[gismo]

In 33-percent of icing accidents or incidents, snow was being reported at the surface. Snow falling from a cloud *may* reduce the risk of icing (especially at the bases), but doesn't always guarantee a glaciated cloud.

Snow grains or pellets reaching the surface are an excellent indicator of supercooled liquid water in the clouds. Frequently, both of these are often mixed with rain (typically freezing rain).

I thought that snow pellets were the result of snow falling through an above freezing layer and then into below freezing air closer to the ground.

 

[Geico266]

...but if the reason the engine quit is an iced-over air filter, pulling the carb heat knob will bypass the filter and get you running again. Just beware of pulling the carb heat when you have no induction icing symptoms, as in snow, that can cause carb ice to form with no way to clear it.

Capt Ron, I know of no carb heat system that bypasses the air filter. Alt air does, but any carb heat I've ever delt with, installed, or adjusted simply added heat to the intake air. I have not worked on every airplane, but any experimental I've ever worked on was this way. Alt air was a seperate system, usually auto matic as in a magnetic trap door at the bottom of the filer housing.

We must not be on the same page here.

 

[jesse]

Capt Ron, I know of no carb heat system that bypasses the air filter. Alt air does, but any carb heat I've ever delt with, installed, or adjusted simply added heat to the intake air. I have not worked on every airplane, but any experimental I've ever worked on was this way. Alt air was a seperate system, usually auto matic as in a magnetic trap door at the bottom of the filer housing.

We must not be on the same page here.

Carb heat bypassing the air-filter is very common on many installations. As to the percentage of the installations? I have no idea. But many/most of the certified airplanes I've flown are setup this way. Someone smarter than me can fill in the details...

 

[flyingcheesehead]

Interesting dichotomy here between some experienced pilots, and the weather god himself. I'd just say, having lived my whole life in WI, that I'll happily fly in rain (when it's plenty warm out), I'll happily fly in dry snow, but no way in hell I'd fly when there's pink on the radar. That stuff's sticky.

 

[twdeckard]

In 33-percent of icing accidents or incidents, snow was being reported at the surface. Snow falling from a cloud *may* reduce the risk of icing (especially at the bases), but doesn't always guarantee a glaciated cloud.

This is a valuable post. I didn't fill out my inference well enough. It was my experience that if I was standing at an airport and it was snowing big fluffy flakes that we could launch, and if I was flying along with the noselight on and you got the Millenium Falcon going to warp-speed view then there was nothing sticking to the airplane. Since I probably avoid cloud exposure when wearing gloves I have never run enough experiments to conclude the clouds themselves were always benign. I've never for example used surface observations along the route of snow fall to try to predict enroute icing probability while tooling along IMC. However, I'd have assumed that the snow fall must have implied crystalized clouds.

Thanks for the response. It probably goes to your weather education thesis. Many of us grow up in the system exposed to the weather a lot and like witch doctors we learn what works and what doesn't. But we are seeing symptoms and not causes ...

Todd

 

[Cap'n Jack]

Carb heat bypassing the air-filter is very common on many installations. As to the percentage of the installations? I have no idea. But many/most of the certified airplanes I've flown are setup this way. Someone smarter than me can fill in the details...

This has been my (limited) experience as well on carburated aircraft. My 1985 C-152 manual demonstrates this configuration. My understanding is that older (pre-fuel injection) C-172 aircraft and C-150s work the same as the C-152. I suspect Piper works the same way although my Piper Archer II Information Manual doesn't explicitly say so. This group of aircraft are still a large portion of the fleet.

Planes with fuel injected engines (such as later C-172) will have an spring loaded alternate air intake. My C-172S manual indicates I loose 10% power if this alt-air trips at full throttle.

Capt Ron, I know of no carb heat system that bypasses the air filter. Alt air does, but any carb heat I've ever delt with, installed, or adjusted simply added heat to the intake air. I have not worked on every airplane, but any experimental I've ever worked on was this way. Alt air was a seperate system, usually auto matic as in a magnetic trap door at the bottom of the filer housing.

We must not be on the same page here.

This suggests that experimental planes have different system configurations than certificated planes WRT carb heat. I suspect the planes with the spring/magnet loaded alternate air intakes were fuel injected.

 

[Geico266]

This has been my (limited) experience as well on carburated aircraft. My 1985 C-152 manual demonstrates this configuration. My understanding is that older (pre-fuel injection) C-172 aircraft and C-150s work the same as the C-152. I suspect Piper works the same way although my PiperArcher II Information Manual doesn't explicitly say so. This group of aircraft are still a large portion of the fleet.

Planes with fuel injected engines (such as later C-172) will have an spring loaded alternate air intake. My C-172S manual indicates I loose 10% power if this alt-air trips at full throttle.

I admit I do not (cannot) work on certified planes and I only work on RV's. This just does not make sense to my experimental brain. Did I just say that?

Why would you want to pull carb heat and have the air filter bypasses allowing direct access to the intake for debris?

 

[Everskyward]

Many of us grow up in the system exposed to the weather a lot and like witch doctors we learn what works and what doesn't. But we are seeing symptoms and not causes ...

I think the other problem is that while, theoretically, it might be OK to fly through a rain/snow mix because, theoretically, the the snow might be melting into rain, those conditions could only apply your location right now. But both the weather and the airplane are dynamic so unless you are going to stay in the pattern you will be exposed to changing conditions. You can make a best guess about what is going to happen but I wouldn't feel confident about that in an airplane with no deice/antice. You might get away with it or you might not. I have flown in potential icing conditions for a long time (in a FIKI airplane) without getting any then all of a sudden it is there. Those temperatures around 0C are in the worst range for potential icing too.

 

[Capt. Geoffrey Thorpe]

Why would you want to pull carb heat and have the air filter bypasses allowing direct access to the intake for debris?

Because it bypasses the air filter. In the event that the air filter is plugged with snow and/or ice, you can keep the engine running. Of course, one wouldn't want to run around with carb heat applied on the ground since you will be picking up dust and stuff.

 

[N801BH]

Interesting dichotomy here between some experienced pilots, and the weather god himself. I'd just say, having lived my whole life in WI, that I'll happily fly in rain (when it's plenty warm out), I'll happily fly in dry snow, but no way in hell I'd fly when there's pink on the radar. That stuff's sticky.

My thoughts exactly. I will fly with this pilot anytime.

 

[jesse]

Why would you want to pull carb heat and have the air filter bypasses allowing direct access to the intake for debris?

The air is reasonably clean up in the sky and if you get into some nasty icing conditions and the filter freezes over you'll appreciate it On the fuel injected airplanes you'll have that automatic spring loaded deal usually, but on the older carb'd engines it happens with carb heat.

 

[Geico266]

Because it bypasses the air filter. In the event that the air filter is plugged with snow and/or ice, you can keep the engine running. Of course, one wouldn't want to run around with carb heat applied on the ground since you will be picking up dust and stuff.

This is the point I was trying to make, turn the carb heat on when flying in snow to keep the air filter clear of snow. I can see the reasoning to by pass it. If you need to pull carb heat in flight due to a plugged filter or icing you are good to go. Got it!

The air is reasonably clean up in the sky and if you get into some nasty icing conditions and the filter freezes over you'll appreciate it On the fuel injected airplanes you'll have that automatic spring loaded deal usually, but on the older carb'd engines it happens with carb heat.

It is intersting to me that RV's are not built that way. Carb heat just heats the air.

 

[TangoWhiskey]

Because it bypasses the air filter. In the event that the air filter is plugged with snow and/or ice, you can keep the engine running. Of course, one wouldn't want to run around with carb heat applied on the ground since you will be picking up dust and stuff.

Yup, which is why the non-fuel-injected planes I've flown have "carb heat off" in the after-landing checklist. Learned the reason "why" in Rod Machado's private pilot handbook.

 

[twdeckard]

It is intersting to me that RV's are not built that way. Carb heat just heats the air.

This may not be absolutely true, at least not of all the RV models, or all the RV engine installations. I thought the carb heat was either a pure alternate air drawn from under the cowling (and thus presumed to be warm) or a mixture of a muff and an external air source.

I have never looked under the hood of one however ...

 

[gismo]

I admit I do not (cannot) work on certified planes and I only work on RV's. This just does not make sense to my experimental brain. Did I just say that?

Why would you want to pull carb heat and have the air filter bypasses allowing direct access to the intake for debris?

Because the certification rules require it? Actually, AFaIK, you could have a separate control from the carb heat to bypass the air filter, but every standard or utility category airplane with an air filter and carb heat I have ever seen (and that's quite a few) combined carb heat with the air filter bypass. One of the more unusual configurations I've seen is on the Bonanzas with pressure carbs, where the alt air actually closes a valve behind the air filter closing off that path. Then the spring loaded alt air door is forced open by the pressure drop in the induction system ahead of the carb.

 

[Ted]

My thoughts exactly. I will fly with this pilot anytime.

I've not flown with him, but I have played chess with him.

 

[Geico266]

Because the certification rules require it? Actually, AFaIK, you could have a separate control from the carb heat to bypass the air filter, but every standard or utility category airplane with an air filter and carb heat I have ever seen (and that's quite a few) combined carb heat with the air filter bypass. One of the more unusual configurations I've seen is on the Bonanzas with pressure carbs, where the alt air actually closes a valve behind the air filter closing off that path. Then the spring loaded alt air door is forced open by the pressure drop in the induction system ahead of the carb.

I talked to my local A&P yesterday, he does the annual condition inspections on my RV's. It is as suggested here that the carb heat in most certified planes does bypass the air filter. It is amazing to me that I did not know this, but I only work on RV's because they are experimental. It certainly does make sense from a practical stand point, one control does both. Live & learn!

 

[RogerT]

Carb heat bypassing the air-filter is very common on many installations. As to the percentage of the installations? I have no idea. But many/most of the certified airplanes I've flown are setup this way. Someone smarter than me can fill in the details...

The carb heat on my Titan bypassed the air filter. I used a Cessna 150
box when I built it.

RT

 

[gismo]

Live & learn!

Sometimes, particularly where aviation is involved it's more like "learn & live". I'm leaning new stuff about flying all the time, my goal is to learn faster than I forget.

 

[flyersfan31]

Sometimes, particularly where aviation is involved it's more like "learn & live". I'm leaning new stuff about flying all the time, my goal is to learn faster than I forget.

You said it!!!

 

[Cap'n Jack]

I talked to my local A&P yesterday, he does the annual condition inspections on my RV's. It is as suggested here that the carb heat in certified planes does bypass the air filter. It is amazing to me that I did not know this, but I only work on RV's because they are experimental. It certainly does make sense form a practical stand point, one control does both. Live & learn!

And here you thought Jesse and I were yanking your chain

Do RVs use mostly fuel injected engines?

 

[gismo]

And here you thought Jesse and I were yanking your chain

Do RVs use mostly fuel injected engines?

From what I've seen, many use pressure carbs (would be called throttle body injection in a car). Typically that setup is much less susceptible to carb icing than a conventional carb. But unless there's an effective inertial separator ahead of the air filter, impact ice (not to mention other debris like an unlucky bird) will always be a concern that is normally mitigated by providing some means of letting air bypass the filter.

 

[Geico266]

Sometimes, particularly where aviation is involved it's more like "learn & live". I'm leaning new stuff about flying all the time, my goal is to learn faster than I forget.

I'll second that! I love flying for that reason. Flying is like being a DR. in that you are practicing!

And here you thought Jesse and I were yanking your chain

Do RVs use mostly fuel injected engines?

I would guess most have carbs (cheaper) but all I've seen have carb heat though the filter. that is why I suggested pulling it right away to keep the filter clear.

From what I've seen, many use pressure carbs (would be called throttle body injection in a car). Typically that setup is much less susceptible to carb icing than a conventional carb. But unless there's an effective inertial separator ahead of the air filter, impact ice (not to mention other debris like an unlucky bird) will always be a concern that is normally mitigated by providing some means of letting air bypass the filter.

Usually, there is an automatic alt air flapper door (with a magnet) on the bottom of the filter housing that, in the absense of positive pressure from ice or said feathered fowl, would activate, opening the trap door, and keep the engine running with ambiant airpressure from the cowl area. This is assuming the bird makes it though the prop!

 

[Bravo]

I wanted to revive this post. That time of year and I would love to get some fresh looks on this weather situation. Any new words of wisdom? I have flown in the snow prior to getting my IR. Now I am petrified of the weather being more aware of the danger. I also feel I may not be flying when I could.

 

[peerlesscowboy]

Technically, if the problem is impact ice on the air filter, "carb heat" will help even if there's no "heat" since it provides an alternate path for the air bypassing the clogged filter. Of course if you don't have carb heat or alt air, you're in deep doo doo.

Brings to mind an IFR flight over the mountains between Spokane and Kalispell. In and out of cloud (mostly in) at 15,000'. Barely a trace of airframe ice, flying in snow. Cessna 170 with carburated Lycoming O-360, engine commenced to running poorly and losing power even with the throttle wide open I noted leaning the mixture smoothed out the engine and restored at least some of the power but soon it required even more and then more mixture leaning to keep it running smoothly. Eventually it occurred to me that I've got the mixture almost leaned to idle cutoff to keep it running smooth and I'm still not producing enough power to maintain altitude .....hmmmm, try the carb heat. Pulled the carb heat "ON" and the engine promptly quit. Pushed the mixture back in about halfway and the engine and my heart started up again, proceeded on to Kalispell and lived happily ever after
Later safely on the ground I'm pondering this chain of events and I believe;
The ram air filter was clogging up with snow causing the mixture to progressively enrichen with the filter acting like a choke. Leaning the mixture knob would restore the correct air/fuel ratio until the filter clogged up even more which required even more leaning. When I applied full carb heat and bypassed the snow cogged filter suddenly the engine is getting plenty of air and not enough fuel to support combustion.

 

[James331]

Yup, which is why the non-fuel-injected planes I've flown have "carb heat off" in the after-landing checklist. Learned the reason "why" in Rod Machado's private pilot handbook.

I thought taught carb heat off on short final, landing on dirt strip or dusty places it was nice to switch to filtered air while the air was still clean, also having max power down low is a good thing.

 

[skidoo]

Brings to mind an IFR flight over the mountains between Spokane and Kalispell. In and out of cloud (mostly in) at 15,000'. Barely a trace of airframe ice, flying in snow.

Just curious, what was your best out if you found that you did pick up significant ice? MEA at 13K still freezing?