Lingering in icing

[Scott Dennstaedt, PhD]

On 7/13/2022 at 3:22 PM, Danb said:

As Paul mentioned it involves all four forces of flight are compromised negatively. Increased drag, reduced lift, increased weight reduced thrust. 
 

 

Weight is usually not an issue with airframe ice unless you are accreting it on all aircraft surfaces (e.g., freezing rain).  Leading edge ice which is the most common (and why certified ice protection systems area located there) will usually only add 50-100 lbs to the overall gross weight. It is the disfiguring of the airfoil and increase in the stall speed that is the biggest concern. Drag slows you down and eventually your "new" stall speed and airspeed meet up.    

[Scott Dennstaedt, PhD]

On 7/13/2022 at 7:38 PM, M20F said:

As AA4184 showed everyone. 

That was a clear case of non-classical SLD.  

[Fly Boomer]

5 hours ago, Scott Dennstaedt, PhD said:

Just to point out that there's some bad or incomplete guidance in this article.  

Thanks!

[hais]

9 hours ago, Scott Dennstaedt, PhD said:

Weight is usually not an issue with airframe ice unless you are accreting it on all aircraft surfaces (e.g., freezing rain).  Leading edge ice which is the most common (and why certified ice protection systems area located there) will usually only add 50-100 lbs to the overall gross weight. It is the disfiguring of the airfoil and increase in the stall speed that is the biggest concern. Drag slows you down and eventually your "new" stall speed and airspeed meet up.    

Is the 50-100 lbs assuming a certain duration? Or does the ice start to break off beyond that accumulation?

[Scott Dennstaedt, PhD]

43 minutes ago, hais said:

Is the 50-100 lbs assuming a certain duration? Or does the ice start to break off beyond that accumulation?

A different question would be, "at what point does the disfiguring of the airfoil take over before the weight becomes an issue?"

Essentially, you can expect to start to develop issues controlling the aircraft due to the increase in stall speed and drag vs the increase in weight on the leading edge. Most of the icing incidents and accidents occur when the angle of attack increases...this means changing flap configuration, climbing or increasing/decreasing power. This doesn't happen because of weight.    

[GeeBee]

Typically disfiguring of the airfoil comes in the form of a "dog bone" occurring on the leading edge. Fat airfoils like the Bonanza form "dog bones" more rapidly than a Mooney, once icing begins. However the fatter the airfoil the slower it is to begin to ice. Skinny airfoils like the Mooney will start collecting ice before a fat airfoil. So an Aztec for instance will deform more than a Mooney, but the Mooney will be the first to collect ice. Aztecs are among the slowest to ice. With the center of lift on a non-laminar airfoil closer to the leading edge, it will stall out fairly quick due to deformation. That is why you need to be aggressive with ice mitigation on these airplanes. Airplanes which collected ice fastest in my career was Aerostar 601 and the DC-9/MD-80 series, which of course had skinny airfoils.

[hais]

1 hour ago, Scott Dennstaedt, PhD said:

A different question would be, "at what point does the disfiguring of the airfoil take over before the weight becomes an issue?"

Essentially, you can expect to start to develop issues controlling the aircraft due to the increase in stall speed and drag vs the increase in weight on the leading edge. Most of the icing incidents and accidents occur when the angle of attack increases...this means changing flap configuration, climbing or increasing/decreasing power. This doesn't happen because of weight.    

Indeed.

I was wondering though whether there's a time limit to unprotected surfaces - suppose anti-icing is keeping protected surfaces clean, and that you are in moderate conditions, and that these don't change. Will weight and drag on fuselage/cowling eventually exceed available power/lift?

From answers so far, the opinion appears to be no. But I suppose those answers are assuming short exposure. Perhaps there's no easy analytical way to get an answer other than a wind tunnel test.

[hais]

12 minutes ago, GeeBee said:

Typically disfiguring of the airfoil comes in the form of a "dog bone" occurring on the leading edge. Fat airfoils like the Bonanza form "dog bones" more rapidly than a Mooney, once icing begins. However the fatter the airfoil the slower it is to begin to ice. Skinny airfoils like the Mooney will start collecting ice before a fat airfoil. So an Aztec for instance will deform more than a Mooney, but the Mooney will be the first to collect ice. Aztecs are among the slowest to ice. With the center of lift on a non-laminar airfoil closer to the leading edge, it will stall out fairly quick due to deformation. That is why you need to be aggressive with ice mitigation on these airplanes. Airplanes which collected ice fastest in my career was Aerostar 601 and the DC-9/MD-80 series, which of course had skinny airfoils.

I suppose this statement can be generalized to propellers?

[GeeBee]

Props will typically shed at the outer ends and accumulate closer to the hub which is why all the protection is located there. The primary protection is RPM and centrifugal force for the outer length of blades.  I used to fly Aztecs and Navajos in the Cascades at night. Typically, a quick RPM increase can shed all but ice on the hubs when the prop heat was weak or inop. I came to really appreciate the alcohol or TKS prop protection because it runs down the entire blade and coupled with RPM keeps things really clean.

On  jets the inlets and sometimes the bullet are heated to protect ice from building up and breaking off into the fan. The only thing that protects the fan is RPM which is why manufacturers require periodic run ups on the ground to shed ice from the blades. I know a certain airline in SLC that toasted 4 757 engines in one day during freezing fog and the pilots forgot run ups, then applied take-off power only to FOD them out with ice.

[MikeOH]

10 minutes ago, GeeBee said:

 I know a certain airline in SLC that toasted 4 757 engines in one day during freezing fog and the pilots forgot run ups, then applied take-off power only to FOD them out with ice.

Ouch!

How's their new careers at Burger King working out?

[GeeBee]

11 hours ago, MikeOH said:

Ouch!

How's their new careers at Burger King working out?

At most airlines there is only three things that will get you fired. 

On duty intoxicated

Theft

And the one that gets most pilots fired, lying.

If you screw up just raise your hand and take the foul. The line will back you up.

[glenn reynolds]

Much of this thread doesn't relate to how my TKS equipped mooney handles ice.  the comments here are in response to the full three pages of prior comments where folks have commented about icing.  As this is a mooney thread, my comments are about how the mooney CAV tks know ice system works for me, your experience is likely to be different.   

The prop slinger keeps the empennage ice free in appropriate conditions (which is to say explicitly, any airplane can be overwhelmed and thus I always assume this can happen and I have plan B). The weeping wings keep my wings clean, not just the leading edges (same appropriate condition comment).  My last moderate ice encounter was on the approach to Victoria airport in Canada as the number four plane in the que.  i refused lower clearances three times from ATC approach, which meant I had surplus altitude by the time it was my turn to land.  I didn't need this altitude but had the tks system failed it would have been my plan B.  ATC wanted me lower so they could stack planes above me.  I stated "unable, in icing meteorological conditions".  I landed after a king air and we both arrived at the same ramp.  his leading edges were clean, his props were clean and his entire airframe had two inches of ice.  My landing light lenses were carrying two inches of ice, my entire airplane was clean (my gear only came out on very short final)  Why: because the tks fluid is a glycol film which mixes with the ice/water and films everything it touches.  The king air had boots which only cleared his leading edges.  The system does have redundancy in that I have two tks pumps, i have two alternators so I can keep power on to keep a pump running.  If a panel fails it only affects one section, not the whole airframe.  if the nose slinger fails I have a windshield system so there is some level of redundancy.  However there is nothing redundant about an airplane.  If my engine fails so does the plane.  if a tire fails, my landing will not be pretty so there is no level of redundancy which makes flying a zero risk activity. 

The only time limit on TKS operation is that of tks gallons remaining.  The TKS system allows a fast pumping rate and slow pumping rate.  The amount required depends on what weather you are flying in.  This is a lot like how we should plan for our fuel, how much did you start with?  How much are you consuming per hour? what is the time to your alternate?  Do you have a plan B? a plan C?  Are you monitoring headwinds?  I would suggest that flying in weather requires a higher level ok knowledge than flying on a calm wind sunshine day.  Is the possibility of a thunderstorm a no fly limitation?  it depends if your a novice: likely yes.  If you have a couple thousand hours flying the tropics and understand how far away from T storms to be safe, then the answer is no.  So if there are no hard and fast rules for how much crosswind or gusts, or darkness or clouds, then each pilot must set standards which they back up with study, ongoing learning and a desire to stay alive.  i think it's important to be realistic.  There are VERY hard and fast rules about how much gas you MUST have and yet fuel exhaustion crashes far more airplanes than almost any other item.  so this leads to my closing statement, don't let a fancy piece of equipment take the place of knowledge.  An airframe parachute doesn't preclude needing to know how to handle inflight failures; A twin engine airplane doesn't assure safer flight; on board weather data doesn't guarantee safe flight with T storms, and a certified known ice airframe doesn't make a plane iceproof.  I enjoy learning and thus weather flying adds a layer of learning which I accept and embrace.  

[GeeBee]

I would add that airplanes like the King are better off with boot due to their center of lift being further forward. A laminar wing like the Mooney benefits from a TKS system over boots and can ultimately experience harsher conditions with a safe outcome.

 

[glenn reynolds]

55 minutes ago, GeeBee said:

I would add that airplanes like the King are better off with boot due to their center of lift being further forward. A laminar wing like the Mooney benefits from a TKS system over boots and can ultimately experience harsher conditions with a safe outcome.

 

that is an excellent point and points out that wing shape is almost never discussed when it comes to Icing.  Well done GeeBee

[carusoam]

This thread has earned the ‘Holy Cow!’ Award….  

I’m betting Hais, the OP, was expecting a more simple answer…

What we have learned… there is no simple answer to icing…. 
 

To cover it for Mooney related flying still takes a Holy Cow amount of info… 
 

Soooo… it sounds like a question on a government test…

Can we linger, or not….

 

Most training for things like icing is three fold….

1) how to avoid it… followed by…

2) how to get out of it… then…

3) Once you’ve done it…. How to get the newly designed wing, with an inefficient prop, with weight and balance changed in unknown ways…. With a new unknown stall speed… Safely on the ground…

4) Imagine using your FAA issued license to try and scrape a peep hole out on the windscreen… 
 

Once you have spent some time in mild freezing conditions and see how quickly ice builds up on the leading edge….

It is safe to say this is an English test…

We have gathered great insight on everything to know about icing…

And simply define the answer as Do Not Linger….

There is nothing like super cooled rain drops that are large…. They are liquid and immediately freeze as they crash onto the airframe…

The time frame for immediate… is more like parts of a second…the water has time to spread and freezes at the same time…

 

Keep in mind… it is really hard to see most of the airplane from the pilot’s seat…

The weight gain can be measured in pounds per second… which can be a lot of pounds over time….

 

Put that in the same category as the yellow arc on the tach…. “Not for continuous operation”….

Don’t linger there either….

 

Great insight everybody!

Thanks for sharing it all….

+1 for TKS and FIKI systems, and the knowledge to use them….

Go MS!

Best regards,

-a-

[Pinecone]

My point was and is, no matter what you have, TKS, boots, hot wing (jets), there is no reason to LINGER in ice.

Use your anti ice to deal with any icing you encounter, but try to get out of the ice as soon as practical. 

Your anti ice could be overwhelmed, you could have a failure.  And then you are in trouble.

[Scott Dennstaedt, PhD]

21 hours ago, glenn reynolds said:

As this is a mooney thread, my comments are about how the mooney CAV tks know ice system works for me, your experience is likely to be different. 

Agreed that the TKS system has some distinct advantages.  I was interviewed by CAV many years ago that you can read here. 

However, every certified ice protection system has only been certified for penetration into small drop icing scenarios. It is the large drop environments that are the dangerous to these aircraft. Unfortunately, the ones that most pilots are taught about in their primary training are actually the exception, not the rule.  

21 hours ago, glenn reynolds said:

So if there are no hard and fast rules for how much crosswind or gusts, or darkness or clouds, then each pilot must set standards which they back up with study, ongoing learning and a desire to stay alive.  i think it's important to be realistic. 

What I see is that the definition of "realistic" has an unfortunate bad side to it.  No pilot would turn and head toward a supercell thunderstorm on purpose...but it's not the supercell storms that are likely to bite you.  It is the benign-looking low-topped convection that is the biggest threat to aviation.  A typical rain shower is the threat I worry the most about.

 

21 hours ago, glenn reynolds said:

I enjoy learning and thus weather flying adds a layer of learning which I accept and embrace.  

Yes, I have a lot of learning yet to do in this area.    

[Greg Ellis]

On 7/14/2022 at 9:25 PM, N201MKTurbo said:

That shouldn’t happen, you open the carb heat and you get hot unfiltered air.

That being said I’ve worked on a couple of planes where the carb heat was so FUed and mis rigged that it wouldn’t save anybody’s ass.

I think he was saying that the filter on the front of the cowl will clog with wet snow.  Carb heat does not affect this since it is on the front of the cowl and not in the carb venturi inlet where ice can form as well.

[Greg Ellis]

3 hours ago, Scott Dennstaedt, PhD said:

What I see is that the definition of "realistic" has an unfortunate bad side to it.  No pilot would turn and head toward a supercell thunderstorm on purpose...but it's not the supercell storms that are likely to bite you.  It is the benign-looking low-topped convection that is the biggest threat to aviation.  A typical rain shower is the threat I worry the most about.

 

Looking forward to going to your talk on Tuesday at Airventure on the Dangers of Low-Topped Convection.

[N201MKTurbo]

2 hours ago, Greg Ellis said:

I think he was saying that the filter on the front of the cowl will clog with wet snow.  Carb heat does not affect this since it is on the front of the cowl and not in the carb venturi inlet where ice can form as well.

Yes, but carb heat doesn’t draw its air through the air filter. It will bypass an iced over air filter.

[kortopates]

Yes, but carb heat doesn’t draw its air through the air filter. It will bypass an iced over air filter.

all true, but i think what the NTSB reports show is that Mooney pilots aren’t primed to use it right away; especially when already at a high DA in the mountains with very little terrain clearance. They find themselves unable to maintain altitude looking for an escape route. Carb heat is hardly ever used by Mooney pilots as it is, so not on a pilots mind when they have so little time to fix it. Cessna pilots though are accustomed to using it on all landings and much more likely to recognize what’s going on and turn it on sooner. Just my opinion from reading NTSB reports.

The early 231’s has a very similar problem with the intake being an ice magnet. It brought down several K’s flying high to lower altitude with warmer temperatures where it self corrected. these early k’s didn’t have automatic opening of the alternate air doors, but these events led to a SB with a mod to fix that so that they all have it now. No pilot action required now.


Sent from my iPhone using Tapatalk

[M016576]

On 7/13/2022 at 7:56 PM, Schllc said:

Anyone who has had a real encounter with icing, has no desire to relive the experience. 
Even asking the question seemed somewhat crazy to me, but then I realized not everyone has had the experience.

Those who have not are probably pretty sure, as I was, that there was some embellishment, and/or exaggeration.

My experience took all of about 3-5 seconds to go from completely clean to accumulating 3”+ on the wings, enough to completely block the windshield, and cut my rate of climb by two thirds. I saw rain drops on the windshield, looked at the wings, looked back at the windshield which was completely covered in ice, looked back at the wings to see the 3”+. It took me longer to type this than it did to actually happen. 

I can honestly say it was the scariest experience of my life, and the thought of “lingering” in conditions that could reproduce that experience is just unfathomable. 
I would NEVER intentionally take a single engine piston, with or without FIKI knowingly into icing conditions. 
But to each their own….

^Yes- this.

icing has taken down airliners, TBM’s, Cirrus’s… you name it, icing has taken it out.  About the only thing I haven’t seen icing take out is a fighter jet, although, I’m willing to bet it’s happened.  I do know of a 4-ship of twin engine fighters that “lingered” in icing conditions just to see if they could find “work-able airspace” and ended up 6 of 8 motors fodded out (I think the damage was somewhere near $8 million).   That’s with engine Heat that’s supposed to help prevent that sort of damage.

if your aircraft doesn’t have a turbine engine… or even if it does… “lingering” in known icing conditions is increasing your risk tremendously, regardless of what some words printed on paper about “certified” say.

that said- a de-icing system is a very useful tool in the event the weather isn’t what you thought it would be, and need an “out.”  This sort of weather system is all too common in the north west.. and it helps with risk mitigation to have a de-icing system.

[carusoam]

Reminder…

Know your alternate air source… not all are very well understood.

 

The M20C has the unmarked alternate air source… hidden using the name Carb Heat…

It is technically alt air and carb heat…. At the same time.

 

As an alt air source… it is a bit constricted, and heated…. Which kind of limits the power production….

Soooo…. When departing at MGTW…. And cruising under clouds…. It is possible that the limited power may cause some challenges…..

 

Consider getting a carb temp indicator to allow for partial carb heat…. 
 

Seeing if @Hyett6420 is around…. He ran into an intake icing challenge with his M20J over the cold Atlantic one day….

 

Best regards,

-a-

[hais]

@Scott Dennstaedt, PhD thanks for http://avwxworkshops.com/ ! 

[Mooney in Oz]

2 hours ago, carusoam said:

Reminder…

Know your alternate air source… not all are very well understood.

 

The M20C has the unmarked alternate air source… hidden using the name Carb Heat…

It is technically alt air and carb heat…. At the same time.

 

As an alt air source… it is a bit constricted, and heated…. Which kind of limits the power production….

Soooo…. When departing at MGTW…. And cruising under clouds…. It is possible that the limited power may cause some challenges…..

 

Consider getting a carb temp indicator to allow for partial carb heat…. 
 

Seeing if @Hyett6420 is around…. He ran into an intake icing challenge with his M20J over the cold Atlantic one day….

 

Best regards,

-a-

A good reminder that if Ram Air is accidentally left open in icing conditions, ice can enter the unfiltered induction system and stop your engine even before heavy accumulation on the wings.

The engine won’t restart until the aircraft is out of icing conditions. You don’t want to be above high terrain if it happens. 

Shortly after I purchased my J, I had the Ram Air system removed in accordance with Mooney SI 20-93 for this very reason.

With regard to turbines, here in Australia, two Cessna 210 Sliver Eagles were brought down by ice blocked engine inlets. One occurred sometime in the 90’s resulting in two fatalities and the other was only less than 3 years ago, which resulted in at least 1 serious injury.

That last particular occurrence was the result of the pilot leaving it too late to escape icing conditions. During the descent, he switched off the de-icing systems, including the heated engine inlet in order to achieve more power due to decaying airspeed, ending in a blocked inlet and total engine flame out.

DO NOT LINGER