What is your icing strategy?

[Scott Dennstaedt, PhD]

Not talking about icing down your drinks or icing on your cake...what strategy do you use when it comes to minimizing your exposure to airframe ice?  We know that safe flying can be accomplished during the cold season when icing risks are high.  But we also know that "safe" flying doesn't necessarily equate to "risk free" flying.  

If you don't have an aircraft with a certified ice protection system (IPS), do you just avoid flying into visible moisture when environmental temperatures are expected to be below freezing?  How do you manage that risk?  What online resources do you use?  What are the key factors to consider?  Do you have sufficient knowledge or is it lacking?  Is most of your winter flying done under Visual or Instrument Flight Rules?  Is there an advantage to one or the other when icing is a concern?  What if you do manage to fly into moderate icing, what's your strategy to escape it?

No need to address any or all of these questions, but get a discussion going about minimizing your exposure to airframe ice. While an IPS does afford you a bit more time in icing conditions, many of the same questions arise. I'll add to the conversation where I can to augment your discussion.  I may be offering an online webinar in the near future to discuss some of these points.   

 

 

[MARZ]

Hi Scott - curious - what type of plane do you own/fly?

 

 

[N201MKTurbo]

I check the icing forcasts and avoid flying in clouds where icing is forecast. I keep a keen eye on my OAT gauge. If it is above 0 C there is no ice. It is a little harder on the cold side. It depends a lot on what the clouds are like. The rule of thumb is ice gets a lot less when the temp is below -10 C but I’ve picked up ice down to -20 C. I usually ask for pilot reports from center to see if anybody is picking up ice at my altitude. 

I have flown in clouds below 0 C and not picked up any ice. I have flown in clouds where no ice was forecast and picked up ice. The darker the cloud the more ice is in it.

If you fly in clouds below 0 C you better be prepared to deal with ice because you will eventually get some.

 

[Jeff_S]

With no ice protection on the plane beyond a heated pitot-tube, primary strategy is to stay out of clouds as much as possible.  Since my plane is not turbo, if I have to fly through any frontal system in the winter I will religiously use the government Forecast Icing Potential products which now come into ForeFlight, and couple that with general weather briefings looking for temps and other things that could cause icing.  I will plan for altitudes that show less icing potential, as well as keep in mind which altitudes (higher or lower) might offer an escape route. This means practically speaking that I wouldn't plan for any altitude higher than about 11,000', as if I did experience icing there I know I have enough power in the Ovation to get quickly up to 13,000 if needed, or of course could go lower.

[FoxMike]

Books are written on this subject so a few lines on the internet will always lack sufficient depth.  I have a FIKI airplane now but flew for years with just a pitot heater to fight ice.  A lot of preflight study is a good idea but knowing where the tops are or a reachable layer is the most helpful.  Normally aspirated airplanes can climb thru ice if the tops are low but you need a good climb rate and a good idea where the tops are.  To my mind the best piece of equipment you can have is a turbo , others might disagree but my turbo has bailed me out on several occasions.  I had a run-in with freezing rain one time.  The boots on T210 did not help much but the turbo saved the day.  The full story is quite a lengthy and involves a controller/CFI saving a nearby airplane with a panicked pilot.  If you fly IFR much you are going to bump into some ice.  It is a serious problem but with  knowledge of the weather system you are flying in you should be able to manage the situation.

[Scott Dennstaedt, PhD]

39 minutes ago, Mike Ropers said:

Hi Scott - curious - what type of plane do you own/fly?

 

 

I don't currently own an aircraft.  Used to own a Turbo Arrow IV and Cirrus SR22, but that was 15+ years ago.  I am a flight instructor, so I get to fly many type of aircraft but most of my time is in Cirrus (both models), Cessna (several models including the TTX), Mooney, Beechcraft and Pipers (several models).  

[Raptor05121]

Don't.

[L. Trotter]

A practical in flight observation.....If temps are +2C through about -25C and you see a nice aura around your shadow in the clouds, ice is a definite possibility.

[RobertE]

If I could toss in another question to this thread, it sounds as if using icing probability forecast products is important to many.  Does that mean that you knowingly fly into visible moisture that is below freezing if the icing probability is low?   If so, how low a probability is low enough?  I know that the answer probably depends on the “outs” you have available but this is the sort or real world advice I find really useful.

I’ve, heretofore, been pretty conservative and have never intentionally flown into a freezing cloud.  I’d like to hear if that’s being too darn conservative. Thanks.

 

[carusoam]

The approach I took towards icing...

Know the outs...

1) top of clouds, if I could climb above them...

2) warmer temps if if I had to go there...

3) The 180° turn if the first two didn’t avail themselves...

I was not a very strong IR pilot for very long...

But I do long to become one again someday...

Having a turbo and a spare pair of cylinders would be nice... 

Best regards,

-a-

[N201MKTurbo]

So, what legally prohibits us from flying? It used to be known ice. It wasn’t known until you had a PIREP of ice. About 20 years ago they changed it to forecast ice. So what is forecast ice? An AIRMET or SIGMET of ice is defenately a forcast of ice. Some blue on an icing probability chart may be a forcast of ice. But how blue does it have to be? Even with an AIRMET, does it apply to your altitude? What if there  are no clouds at your altitude? There is still a lot of room for pilot discretion. 

As long as it doesn’t become an issue nobody is going to give you any grief, but if you start asking for deviations in an AIRMET area you are treading on thin ice (pardon the pun). If it is not an AIRMET area ask away, it is now known ice. 

The biggest thing is the rate of accumulation, if it is building quickly, it demands immediate action. If you are getting a trace accumulation intermittently, you can play it by ear and try some different altitudes or drive around the clouds. Just have a good plan for your outs and know when it is time to throw in the towel and land or turn around.

[jaylw314]

2 minutes ago, N201MKTurbo said:

So, what legally prohibits us from flying? It used to be known ice. It wasn’t known until you had a PIREP of ice. About 20 years ago they changed it to forecast ice. So what is forecast ice? An AIRMET or SIGMET of ice is defenately a forcast of ice. Some blue on an icing probability chart may be a forcast of ice. But how blue does it have to be? Even with an AIRMET, does it apply to your altitude? What if there  are no clouds at your altitude? There is still a lot of room for pilot discretion. 

My understanding is that there is no standard definition of "known ice" nor is there any clear statement from the FAA as to what is and what isn't "known ice."  It is not simply a PIREP of ice, nor is it an AIRMET/SIGMET.

[Ned Gravel]

11 hours ago, RobertE said:

If I could toss in another question to this thread, it sounds as if using icing probability forecast products is important to many.  Does that mean that you knowingly fly into visible moisture that is below freezing if the icing probability is low?   If so, how low a probability is low enough?  I know that the answer probably depends on the “outs” you have available but this is the sort or real world advice I find really useful.

I’ve, heretofore, been pretty conservative and have never intentionally flown into a freezing cloud.  I’d like to hear if that’s being too darn conservative. Thanks.

 

Robert:  No one will tell you that you are being too conservative.  Be conservative and live to fly another day.  Simple.  People who face something they have not trained for or are not familiar with are just about guaranteed to make mistakes.  Many of those folks, in an activity that has the risks associated with ours, do not live to do it again.  

Don't do that.  Be risk adverse until you are confident that you can expand your own envelope.  

I use AIRMET info to show where icing is being forecast - in this case from 3,000' to 12,000'.

I use Foreflight icing predictions (US).  This one shows New England predictions for icing at 6,000'

I use Skew-T charts, such as this one for Syracuse New York, 12 hours from now.  It shows cloud bases at 3,200' and tops near 5,000'.  Higher layers probable near 20,000'.

There are now a couple of scenarios open to you.  If you can get a VFR climb to tops and not enter a cloud under these conditions, you MAY (not guaranteed) be able to stay out of icing.  That was my plan a couple of days ago and it almost backfired.  I had outs the entire way until I crossed the border to Canada, but I was much lower in Canada than in the US, reducing the possibility of icing.

In this chart, note that the 0 degree red diagonal line crosses the dew point temperature line (blue squiggle) at just over 5.000' and it crosses the actual temperature line (red squiggle) just under 10,000'.   Anything higher and more to the left on this chart means icing where clouds are.  Perhaps not where clouds are not - but not guaranteed.  

I would not do this flight under these conditions.  Although icing is forecast on the AIRMET, and while Foreflight predicts none at 6,000' the whole way home, the Skew T charts tell me that there will be cloud to fly through.  In the flight that I did, Ottawa was supposed to be clear below 9,000'.  The forecast was wrong.  It was not.

So be conservative.  If you are not comfortable with what your tools tell you now, trust your instincts.  They will keep you alive.

[Scott Dennstaedt, PhD]

12 hours ago, L. Trotter said:

A practical in flight observation.....If temps are +2C through about -25C and you see a nice aura around your shadow in the clouds, ice is a definite possibility.

That's called a glory!  Good sign of supercooled liquid water in the tops of the cloud.  If you see what looks like sparkles around your shadow, it's likely the cloud top contains mostly ice crystals.  I've seen it a few times, but much harder to photograph.  

 

 

[exM20K]

Scott, isn’t a glory indicative of liquid water regardless of temp? I am always alert when I see a glory below me and am in below freezing temps.  

-dan

[Bob - S50]

My strategy is as I mentioned in another thread.  Avoid flight in clouds at temps below freezing.

1.  Can I operate at the MEA and be below the freezing level?

2.  If not, will I be on top before I get to the freezing level?  If so, will I be below the freezing level before I enter the weather for my descent?

3.  If not, can I operate VFR below the weather?

4.  If not, stay home.

I use multiple sources to guesstimate the  cloud bases and tops including this new, nice app, WeatherSpork.

The Air Force used to use a couple rule of thumbs I remember:

1.  Icing USUALLY occurs from 2000' below to 10,000' above the freezing level.

2.  MOST lightning strikes occur within 5000' of the freezing level.

[Scott Dennstaedt, PhD]

9 hours ago, N201MKTurbo said:

So, what legally prohibits us from flying? It used to be known ice. It wasn’t known until you had a PIREP of ice. About 20 years ago they changed it to forecast ice. So what is forecast ice? An AIRMET or SIGMET of ice is defenately a forcast of ice. Some blue on an icing probability chart may be a forcast of ice. But how blue does it have to be? Even with an AIRMET, does it apply to your altitude? What if there  are no clouds at your altitude? There is still a lot of room for pilot discretion. 

As long as it doesn’t become an issue nobody is going to give you any grief, but if you start asking for deviations in an AIRMET area you are treading on thin ice (pardon the pun). If it is not an AIRMET area ask away, it is now known ice. 

The biggest thing is the rate of accumulation, if it is building quickly, it demands immediate action. If you are getting a trace accumulation intermittently, you can play it by ear and try some different altitudes or drive around the clouds. Just have a good plan for your outs and know when it is time to throw in the towel and land or turn around.

Legally, the limitation (and placard) that states "flight into known icing conditions is prohibited."  See FAR 91.9(a).  If you read this FAA legal counsel interpretation from 2009, it's quite clear (no pun intended) what known icing is from their definition.  However, it's a completely different story how to make that determination.  A G-AIRMET (legacy AIRMETs are not the operational product any more) along your route for widespread moderate nonconvective ice isn't always enough to determine "known icing conditions."  Clearly it's warning you of that possibility.  The key words used in the interpretation are, "If the composite information indicates to a reasonable and prudent pilot that he or she will be operating the aircraft under conditions that will cause ice to adhere to the aircraft along the proposed route and altitude of flight, then known icing conditions likely exist."

So if you were proposing a flight at 10,000 feet and there was a PIREP for moderate ice at 9,000 feet and another at 11,000 feet and the Current and Forecast Icing Products showed the potential for ice along with a G-AIRMET for ice, then it's likely you'd be flying in known icing conditions.   Icing is often very transient.  Certainly by the time you get the location of the PIREPs in two hours, icing in that area might be dissipating.   What if the PIREPs were missing (an early morning flight)?  Lots of possibilities.  

For example, using the Profile View in WeatherSpork, you can see that a flight departing from Evansville, IN at 1630Z today headed to Charlotte, NC is going to be somewhat challenging with respect to ice.  But could the flight be made legally and safely? Possibly.  If you climb to 9,000 feet (IFR), you will likely be at temperatures below freezing, but be between cloud layers between HNB and SDF and then be above the clouds until you reached 1A6 and LNP.  That's where you begin to face the potential for icing conditions (although there's no G-AIRMET later in the flight).  

This tends to agree with the data from the RAP model (the automated Forecast Icing Product is based on this model).  On the Skew-T diagram near SDF, you can see there are definite clear regions between layers, but just above 9,000 feet is the potential for icing.  So that gives me some confidence that somewhere between 7 and 9,000 feet there will be a dry layer.  But this is a very thin margin and without a certified ice protection system (IPS), being the reasonable and prudent pilot that I am, I'd feel obligated to make a no-go call at that altitude.

Never said it was an easy decision. 

[Scott Dennstaedt, PhD]

30 minutes ago, exM20K said:

Scott, isn’t a glory indicative of liquid water regardless of temp? I am always alert when I see a glory below me and am in below freezing temps.  

-dan

Dan,

Yes!  I was just making reference to this as if you were flying in subfreezing temps as an indicator of a possible encounter with icing if you descended into those clouds (assuming you were still in temps below freezing).  

[N201MKTurbo]

I think it is wonderful that we are having these rational discussions. It seems like every time in the past we tried to talk about icing it always degenerated to where anybody who even tried to fly a non-FIKI airplane IFR in the winter was a fool who had no business flying.

This is great!

[Scott Dennstaedt, PhD]

20 minutes ago, Bob - S50 said:

2.  MOST lightning strikes occur within 5000' of the freezing level.

Bob,

I like your strategy!  Just a clarification here with respect to lightning.  It turns out that most "aircraft induced" lightning strikes tend to happen with the aircraft at an altitude very close to the freezing level.  See my eTip that discusses this further.

[GLJA]

As I look out the window, and see snow falling for potentially the next 2 days.. I think to myself, "I guess it's okay that the plane still doesn't have the overhauled fuel servo installed". 

[N201MKTurbo]

40 minutes ago, CDNflyby said:

As I look out the window, and see snow falling for potentially the next 2 days.. I think to myself, "I guess it's okay that the plane still doesn't have the overhauled fuel servo installed". 

But there might be clear blue sky less than 1/2 mile away.

[GLJA]

17 minutes ago, N201MKTurbo said:

But there might be clear blue sky less than 1/2 mile away.

Not bloody likely!!!

[N201MKTurbo]

Ok, 4 miles away....

[Marauder]

14 hours ago, RobertE said:

If I could toss in another question to this thread, it sounds as if using icing probability forecast products is important to many.  Does that mean that you knowingly fly into visible moisture that is below freezing if the icing probability is low?   If so, how low a probability is low enough?  I know that the answer probably depends on the “outs” you have available but this is the sort or real world advice I find really useful.

I’ve, heretofore, been pretty conservative and have never intentionally flown into a freezing cloud.  I’d like to hear if that’s being too darn conservative. Thanks.

 

Robert - I flew for years in WNY back when "forecasted icing" was heard on every briefing. You would end up not flying the entire winter if you followed the forecast only. Today's tools for icing forecasts are much more robust and more importantly real time (i.e. not some FSS guy reading you the 8 am TAF). So, I tend to pay attention to them more closely. The important part of winter flying is what you mentioned, having an out. 

If I were flying from Buffalo to Syracuse in the winter today, I would use all of the tools available to me for icing with the intent to know; 1) where is the forecasted icing 2) how high the cloud tops were 3) where is the freezing level 4) what are the PIREPs showing? 5) where VFR conditions existed and 6) what kind of conditions I would be flying in during an approach to Syracuse.

I remember being told that "icing is where you find it". I recall a flight heading into Buffalo, I am about 10 miles behind a guy in a Piper headed to Buffalo, same altitude. He is declaring an emergency because he was getting rapid ice build up. He descends and is out of the icing. That is my plan, descend 2,000 feet to get out. I fly into the area he was in and got absolutely no ice at all. I attributed it to the faster speed but this is what you'll find in real life.