Most Dangerous Aspect Of Icing, For a light aircraft Options

[AName]

So I just finished with the AFOQT (Air Force Officer Qualifying Test) and ran into a question on one of the pilot sections.

The question read something like "What aspect of ice buildup on the exterior of a light aircraft is the most dangerous?" Then lists answers like:

• Added weight
• Disrupted airflow
• Frozen control surfaces

..and two other I can't remember. I don't remember ever learning a "most dangerous aspect" of icing. I remember someone asking which one was worse and was told "that's like asking if a lion is more dangerous then a tiger...it doesn't really matter cause they will both kill you." Unfortunately, that wasn't any of the answers. Is there a question like this on any of the FAA's written exams?

[AirRabbit]

So I just finished with the AFOQT (Air Force Officer Qualifying Test) and ran into a question on one of the pilot sections.
The question read something like "What aspect of ice buildup on the exterior of a light aircraft is the most dangerous?" Then lists answers like:

• Added weight
• Disrupted airflow
• Frozen control surfaces

..and two other I can't remember. I don't remember ever learning a "most dangerous aspect" of icing. I remember someone asking which one was worse and was told "that's like asking if a lion is more dangerous then a tiger...it doesn't really matter cause they will both kill you." Unfortunately, that wasn't any of the answers. Is there a question like this on any of the FAA's written exams?

Well, I was going to say that THE most dangerous aspect of ice buildup on light aircraft is the degree of hurt you feel at the bottom of the fall ... but since that wasn't one of the answers (unless that was one of the one's you couldn't remember) I'd opt for disrupted airflow. Since most light aircraft have direct control of the control surfaces (cables) that means that you probably could really give the controls a hard input and crack any ice that might have formed - however, since control surfaces are on the trailing edge of lifting surfaces - and ice is normally built up on the leading edges of lifting surefaces, I wouldn't think that would be an answer. Of course added weight could always be a problem, but, depending on the existing passengers, baggage, fuel, etc., there would have to be quite a bit of ice build up and I'd worry about air flow disruption long before the weight became a problem. When ice does form on the leading edge of the wing or tail it changes the shape of that lifting surface; and changing the shape changes the lift characteristics and just MAY cause some or all of the wing - maybe only one wing (? or perhaps the tail) to stall. THAT would be an aspect that would be uncomfortable, at the very least - and some would say "the most dangerous." But... without knowing the other alternatives, this would be just a "best guess" of the remaining alternatives.

[AName]

The other two were like, lost comm and forward visibility. I didn't consider them dangerous enough to factor in with the others (and wasn't even aware ice could cause lost comm ).

I am a bit relieved that you came to the same "best guess" I answered on the test though.

[Harmattan96]

Structural icing, aftermath interview

This 5mn interview will give you an idea of how bad things can get with structural icing. here the amount of icing was light, proving that the first treat is not the weight. The fact that they could fly the airplane also shows that frozen control surfaces is unlikely to be the first culprit.
In this video we are solely discussing airflow disruption.


Here is also the other less well known bigger issue on larger airplanes (namely your transport category turboprops), 23mn long, but well worth the time.
Tailplane stall due to icing

[AName]

Very interesting. Thanks for the info and links.

I still don't see how knowing which aspect is most dangerous would help a pilot though. Especially in a light aircraft, shouldn't all aspects of icing should be taken seriously.

[Harmattan96]

shouldn't all aspects of icing should be taken seriously.

Yes indeed, we should all take all aspects of icing with the respect that it will potentially kill us. Yet, knowing what aspect is the most likely to bite you first or second is critical in understanding a few things:
-Firstly. How to look for it?
-Secondly. Where to look for it?
-Thirdly. Each type, will likely require a different method in surviving this event, shall it happen during flight. A good example was the tailpane icing, which requires the most counterintuitive recovery method in the stalling of said tailplane surfaces.

And, last but not least, it goes along with the basic principles of understanding the aerodynamics of the flying machine, and furthers your education in the "stick and rudder" type of flying I advocate regularly. Of course there is a high chance that you could very well carry on a long life without knowing all of the above; yet, when icing strikes (and you might have seen from that first interview how fast if goes), you better be prepared to make a quick assesment of how serious your condition is and what your options are, both in terms of how far you can go, but also in what it is that you cannot afford to do.
I like to compare an iced-up plane to one that just went through an Anti Aircraft Artillery flight flight interdiction shoot out. Wouldn't it be nice to have somewhat of a clue of what your airframe is still capable of doing by knowing what kind of shell just pushed a hole in your aircraft, as well as, where did it punch a hole in your aircraft.
Here is an example of bad choices that could be made from a pilot undereducated in regards to icing.
You are aviating along in a high performance light twin, say a Beechcraft baron. While at night, you fly through one of those clouds that potentially covers your aircraft in freezing rain pellets in a matter of 3-10 seconds. trust me you'll know, there won't be any clear windshield left, and you can potentially deduct that the rest of your aircraft s the same.
What do we have here? Disrupted airflow is the first concern, those airfoils are not as smooth and lift inducing as they once where, but you are still flying. The weight of such ice has increased the total mass of the aircraft. Finally if the amount of ice is significant enough, we can reasonably assume that it made it's way over those gaps between airfoil and controlling trailing edge (elevator, ailerons, flaps, etc...)
Here is what your undereducated pilot is going to do, once the first moment of panic passes. Reach ATC, declare and emmergency, request vectors for the nearest runway capable of sustaining his aircrafts landing. (In the case of a Baron, that's basically any airport).
Five minuets later our pilot is now on a long final to his emmergency airport, he starts to slow down the airplane for the purpose of extending flaps and gear. The added weight and disturbed airflow due to icing, will likely mean two things, one he cannot fly as slow as his airplane manual once promessed him, two he will have to increase the AOA to a much higher pitch to generate the normal amount of lift required to stay aloft. He is slowly working itself towards a stall, chances are that once the aircraft starts to buffet, he won't quite believe that it is a stall, considering the amount of airspeed that he carries. If he does stall and tries to recover, the potentially forezen controls might not have enough freddom to travel, to allow a recovery, and our pilot stalls and spins on a 2 miles final. Let's assume that he does realize and decides to make a faster approach for his own sake, he now decides to lower flaps or gear, which could be partilly frozen and not come out. Maybe understanding this at first would have allowed him to search for a place to try his equipement at a safe altitude, instead of finding himself on final at an airport. Let's assume the flaps actually come down. Those trusty flaps, which once allowed the airplane to carry the same amount of AOA for a slower airpspeed are know void of any warranty, because no one really knows what flying caracteristic they are going to offer. The added weight of ice on the aircraft could also be a factor there. They could work exactly as advertised, or they could just be iced to the point that they now stall and spin this airplane to the groudn on a 1 1/2 mile final. Note also that if said flaps are indeed iced, the amount of travel on the control surfaces, once again, might not be enough to allow recovery of a stalled condition.
Note our pillot has died twice already.
But this is a good day and our pilot, gets both the gear and the flaps down, all of which do not induce him to become a test pilot, and he just glides the remaining mile left to a full stop on the promessed runway.

Air rabbit pointed out the most likely issue with icing, particularly on a GA aircraft, and as you can see from this scenario (which could sound like a nice fiction, but is actually exactly how pilots kill themselves, and possibly others),airflow disruption is your biggest ennemy. Knowing why does it affetct your aircraft, and how does it affect your aircraft, will allow you to become a good test pilot the day that you are forced to become one.





N.B: I apologize for the blatant mistakes in spelling and ponctuation. I see run-on sentences, capital letters missing, and other figures of style. I had very little sleep last night, and will come back to edit this "exposé" to a more appropriate FL350 format in a not so distant future. Thank you for reading this while waving a noodle strainer in front of your screen in the meanwhile! Very dark sunglasses work as well.

[AName]

Ah, great points. I see the reason for the question and knowing the answer now. Thanks

[Becky_KSTS]

Harm...once again I am very impressed by your knowledge and your willingness to share it. Thank you! That interview was a bit chilling but thankfully they aborted the take-off. Working at an FBO, I will be diligent to watch other planes (Kingairs included) when we have icing conditions. As far as me flying in icing conditions are concerned? I am WAY to much of a chicken to fly our Cessna 172 in that kind of stuff. I know that I will be certain to fly about as high as chickens do...if I get lucky.

[Piltdown Man]

Wings covered with light frost grains the size of 240 grit may increase your stall speed by as much as 20%, your take-off run by 50% and decrease your stalling angle by 5 degrees. Fine dust will do the same. In gliders, bugs on the L/E of some models (DG500) have a simillar affect. The same for Long-eze/Quick-eze drivers - clean the bugs off the canard before flight. I'm with Harm - Answer - Distrupted Airflow. The rest are still correct correct, but the one that has killed the most is this one. Solution - fly clean wings only (or go to the pub).

PM

[AirRabbit]

Wings covered with light frost grains the size of 240 grit may increase your stall speed by as much as 20%, your take-off run by 50% and decrease your stalling angle by 5 degrees. Fine dust will do the same. In gliders, bugs on the L/E of some models (DG500) have a simillar affect. The same for Long-eze/Quick-eze drivers - clean the bugs off the canard before flight. I'm with Harm - Answer - Distrupted Airflow. The rest are still correct correct, but the one that has killed the most is this one. Solution - fly clean wings only (or go to the pub).
PM

I quite agree ... although I would fly with clean wings only and then go to the pub. I don't see the need to choose one or the other - just make sure you get the order correct!

[Fast Jet]

So I just finished with the AFOQT (Air Force Officer Qualifying Test) and ran into a question on one of the pilot sections.

The question read something like "What aspect of ice buildup on the exterior of a light aircraft is the most dangerous?" Then lists answers like:

• Added weight
• Disrupted airflow
• Frozen control surfaces

..and two other I can't remember. I don't remember ever learning a "most dangerous aspect" of icing. I remember someone asking which one was worse and was told "that's like asking if a lion is more dangerous then a tiger...it doesn't really matter cause they will both kill you." Unfortunately, that wasn't any of the answers. Is there a question like this on any of the FAA's written exams?

You know the answers anyway, right? Rain Ice will provided too much weight for the aircraft.

Rime Ice will break off in chunks from its honycombe design on your leading edges. The chunks are uneven and disturb the airflow over the wing(s). Aircraft left on the ground where there is a lot of moisture, like rain, can have water lock in the hinges of the control surfaces like the elevator, moving this control surface can bust the hinge or do other damage, same with the aileron(s). You cannot see Rain Ice normally, the sheer weight of the stuff is a problem and getting out of the Rain Ice situation is quite another loo-loo too. As you will invaribly be flying under a warm front (which is where a lot of rain ice is found) therefore, unles you know the alignment of the front you have to either climb above the rain in the Front, or away from the front or down to a lower level subject to MSA, high ground, terrain, etc., etc., etc. the latter is not the best of escape routes, as the water (from above) is supercooled and its just looking for your cold little aircraft to hit and change to ice. Obviously warmer level are preferable, but if the rain ice came from the typical Nimbo-Stratus cloud, then your viz will be margina to nill until down to the lower levels, if you are lucky, with the drizzle includedcould be as low as 800 feet or lower...!!!! Also, make sure you are not flying along the Front itself, because you would them be subjecting yourself to a continous bombardment of rain ice, not good. So I would rank Rain Ice as the Nimbo-Nastiest - because with Rime Ice, at least you can see it, get scared and do something about it.

[BMeister]

Oooh Awesome Subject I love it, especially seeing as the colder season is here!!

Question what is 'rain ice' Im familiar with 4 types of Ice, Clear Ice, Mixed Ice, Rime Ice & Frost, however frost only occurs on the ground right? so rain ice? are we talking about Ice Pellets?

that's where rain/precipitation falls from a higher altitude (where it's warmer) through a lower altitude (where it's cooler) and freezes = Rain Ice/ Ice Pellets?

Also Im not sure if you you all noticed, but the link given above also has a tutorial/lesson section on Cold Weater operations: http://aircrafticing.grc.nasa.gov/courses/ground_icing/

Happy Thanks Giving.

[Fast Jet]

Oooh Awesome Subject I love it, especially seeing as the colder season is here!!

Question what is 'rain ice' Im familiar with 4 types of Ice, Clear Ice, Mixed Ice, Rime Ice & Frost, however frost only occurs on the ground right? so rain ice? are we talking about Ice Pellets?

that's where rain/precipitation falls from a higher altitude (where it's warmer) through a lower altitude (where it's cooler) and freezes = Rain Ice/ Ice Pellets?

Also Im not sure if you you all noticed, but the link given above also has a tutorial/lesson section on Cold Weater operations: http://aircrafticing.grc.nasa.gov/courses/ground_icing/

Happy Thanks Giving.

Yeh ok, and Happy christmas too. Clear Ice is Rain Ice. Ok? Thats what I meant. I don`t think its warmer up there, more like below freezing (!) for Clear Ice/Rain Ice, its very cold and the water droplets are supercooled - which may mean that although they are below freezing they stay liquid - ((unlike one`s credit crunch banks)). They remain in this liquid state until they hit something solid and a freezing cold aeroplane is just what it wants - as it hits your wing 8/10ths of it flows back onthe surface of the wing as the first bit of the drop freezes on impact - its solid and it sticks tight and is transparent and heavy, alright? you all should know this . . . stuff, cos one day if you are not looking for the conditions, its gonna bite you on the **I have a dirty mouth**.

Hoar frost is the twinkly white frost on the surfaces of the wing after it has been standing overnight outside. It looks harmless enough and almost festive... but the airflow will be disturbed over the upper surface of the wing and you might not get enough lift for takeoff. It is particularly importnat becaue your mind will try to invent many reasons why you do not want to freeze your fingers by scraping it off the upper wing surface, during pre-flighting on a cold and frosty morning, full of coffee, and dying for a P. But is must be done as there are many light aircraft that have arrived in the bottom of the ditch at the end of the runway - de-icing fluid also helps, for the rich and lazy.

You see the ice developing on the spar, like little crystals of sugar that you find on cakes. Note this for when it happens. For this is the start of icing. If on an approach and you START to pick up ice then tell ATC right away and they will give you a lower level - they won`t hang about - good service. If en-route and you get icing then get out of IMC as quick as possible, preferably descending provided you have no high ground, no high ground, so watch your MSA - love your MSA - worship the knowledge of your MSA, know your MSA. All in all, for a light aircrat, which is what this post is about - STAY OUT OF ICING CONDITIONS by planning to stay out of icing conditions during your pre-flight planning - when you get up to IMC level of flying then you must pay especial attention to this. Moisture/IMC and at or below freezing DO NOT MIX you will get ice. While we are here watch out for carb icing too - but this little baby will happen in supposedly clear conditions, indeed, whilst at idle, on a nice hot summers day, on the airfield - it will also occur, when good clear days give fluffy white clouds and you are flying in between them well away from them in good VMC, how nice, how lovely but Carb ice is just around the corner. As you know, and you don`t need me to tell you, always use carb heat when throttling back and throttling back for the descent. Also, aircraft not cleared for flight into icing conditions - are not allowed to fly in icing conditions - so you not only may die but you get to become a criminal too!

In short and in answer to your question - Rain/Clear Ice is the most dangerous, because A/ You can`t see it very well, except for a slightly shiny shhen over the upper surface of the wing and B/ It cannot be got rid of by the use of de-icing equipment which is usually, only installed into the the leading edges of the wings and leading edges of props - this works for rhime ice. All icing is dangerous on light aircraft as most do not have de-icing equipment such as pneumatic boots or electrical heating elements installed. Your option being to get out of it, by doing a 180 or descending bearing in mind the MSA, MSA, MSA or clearing to another area where there is no ice. Avoid is the best option.