Any body ever experience blade icing?

[tiercel]

During flight school, I was taught that anytime the temperature gets within a couple degrees of freezing, you have to worry about icing, yet here in Montana, I have seen the local life flight (AS 350 B3) flying through mixed rain and snow and snow squalls. What kind of meteorological conditions would constitute a no-go situation?

[Future206Pilot]

I have seen the local life flight (AS 350 B3) flying through mixed rain and snow and snow squalls. What kind of meteorological conditions would constitute a no-go situation?

 

If thats out of St. Pat's in Missoula thats Marc D's chopper... You could ask him...

[tiercel]

If thats out of St. Pat's in Missoula thats Marc D's chopper... You could ask him...

You know, I just might. I'll be working there for the next couple of months. Thanks.

[NorCalHeliKid]

In flight school you fly helicopters with carbureted powerplants and no anti-icing or de-icing equipment besides carb heat...whooptie doo! The AS350...is a REAL helicopter.

[FinR]

In flight school you fly helicopters with carbureted powerplants and no anti-icing or de-icing equipment besides carb heat

Now how does the powerplant effect on blade icing??

Any body ever experience blade icing?

Yes, multible times (shame on me...). It's a dangerous situation and things could get very bad, very quickly. I suggest to stay away from icing. All conditions below freezing and with visible moisture ("dry" snow is an exception) are possible conditions for icing. That's in any helicopter without blade de-icing system, alltough there are some differences in models. Some blades/ helicopter types are more sensitive for icing than others, but don't bush your luck... Just stay away.

Edited March 16, 2008 by FinR

[NorCalHeliKid]

Now how does the powerplant effect on blade icing??

 

Yes, multible times (shame on me...). It's a dangerous situation and things could get very bad, very quickly. I suggest to stay away from icing. All conditions below freezing and with visible moisture ("dry" snow is an exception) are possible conditions for icing. That's in any helicopter without blade de-icing system, alltough there are some differences in models. Some blades/ helicopter types are more sensitive for icing than others, but don't bush your luck... Just stay away.

 

I don't recall saying that a carburetor has an effect on blade icing... I was simply stating that there are no anti or de-icing sytems on training aircraft (besides carb heat) and that is the reason for the preaching about staying away from it. Usually all we have to work with in Robbies is the carb heat, thats only when the knob is actually working though.

Edited March 16, 2008 by NorCalHeliKid

[helonorth]

In flight school you fly helicopters with carbureted powerplants and no anti-icing or de-icing equipment besides carb heat...whooptie doo! The AS350...is a REAL helicopter.

 

It may be a "real" helicopter, but I don't think there's an Astar made with blade deicing. Just

as dangerous as anything else in icing conditions.

[relyon]

... The AS350...is a REAL helicopter.

OT - If you're flying higher and/or faster than you care to jump out any helicopter is real.

 

Bob

[southernweyr]

Good one relyon.

 

I have seen ice start to form on the bubble so I am assuming blade icing was present. It was a quick decent to a lower altitude that solved the problem. I was actually flying next to Flathead lake at the time. Ah, brings back memories.

[Kelly N.]

I don't recall saying that a carburetor has an effect on blade icing... I was simply stating that there are no anti or de-icing sytems on training aircraft (besides carb heat) and that is the reason for the preaching about staying away from it. Usually all we have to work with in Robbies is the carb heat, thats only when the knob is actually working though.

 

I'm not going up in a carberated helo if the carb heat isn't working. I haven't flown much but I've heard enough about carb icing to know that if the pre-flight check of carb heat fails, I'm shutting down if the conditions are conducive to carb icing.

 

On a related topic, although Robinson's published range for carb icing is 20-70deg F (R-22 POH), I've heard that Lycoming says 20-90deg. I would tend to play it safe but, would be curious if anyone else uses the Lycoming numbers for conditions conducive for carb icing as their guideline instead of Robinson's. Anybody know why the discrepancy between the two published ranges?

 

Thanks,

Kelly

[NorCalHeliKid]

I'm not going up in a carberated helo if the carb heat isn't working.

On a related topic, although Robinson's published range for carb icing is 20-70deg F (R-22 POH), I've heard that Lycoming says 20-90deg. I would tend to play it safe but, would be curious if anyone else uses the Lycoming numbers for conditions conducive for carb icing as their guideline instead of Robinson's. Anybody know why the discrepancy between the two published ranges?

 

Thanks,

Kelly

 

First, let me make it clear that I have never and would never fly with the absence of carb heat in an R22....I agree with you, I would shut down if it didnt work. I made the statement because Ive watched Robinson's sit on the ground more than once for failed...everythings. They do it well. From what I know the "conditions conducive" to carb icing can be affected with temperature yes, as it effects the amount of moisture a parcel of air can hold, but the moisture part is the other factor to consider. Where does Lycoming publish a different range for temp for the O-360 J2a?

[Kelly N.]

First, let me make it clear that I have never and would never fly with the absence of carb heat in an R22....I agree with you, I would shut down if it didnt work. I made the statement because Ive watched Robinson's sit on the ground more than once for failed...everythings. They do it well. From what I know the "conditions conducive" to carb icing can be affected with temperature yes, as it effects the amount of moisture a parcel of air can hold, but the moisture part is the other factor to consider. Where does Lycoming publish a different range for temp for the O-360 J2a?

 

Hey NorCalHK,

 

 

Like I said, I haven't flown much and am still learning (and didn't mean to imply that you were flying with a broken anything). I was just stating that the carb heat is a particular worry of mine. I have just come across the different numbers in the past (both in publication listed and in my ground school) and have wondered what constituted the difference.

 

They mention the different range in reference to all carberated engines (not O360J2A specifically) in their Key Operations pdf found at

 

http://www.lycoming.com/support/tips-advic...0Operations.pdf (It's a reprint from their Flyer publication).

 

You are correct obviously that humidity plays a factor, however, since OAT is a more readily available measurement while flying, my understanding is that using the temperature is the safe way to play it operationally (unless you're absolutely sure that the conditions are below 50-60% relative humidity and will be for the entire flight - not sure about how comfortable I would be with that assumption).

 

 

Safe flying,

Kelly

[West Coaster]

During flight school, I was taught that anytime the temperature gets within a couple degrees of freezing, you have to worry about icing, yet here in Montana, I have seen the local life flight (AS 350 B3) flying through mixed rain and snow and snow squalls. What kind of meteorological conditions would constitute a no-go situation?

 

Apart from obvious IMC icing conditions, the thing that usually constitutes a go no-go situation is the pilot's experience. As you gain experience during your career you'll see pilots who fly in conditions you won't, and visa-versa. As always trust what your gut is telling you.

 

If you're ever out in questionable conditions remember to set your torque to a cruise setting and leave it alone, and have a way out if need be. If it starts creeping up even a little, get as low as possible as your blades have ice building up on them. If you can't get low enough... land now!

[Darkhorse]

I'm sure it is a little different for different types of helicopters but I notice ice first start to form on the windshield wipers. Also keeping a constant power setting and having to creep in torque. How bad can it be? I have been in a CH-47 with 5k pounds of ice built up on the airframe (4 inches thick in some places) based on the % of torque being pulled. Weather came in fast and we could not descend or land nearly as fast as we wanted to. Another aircraft would have MAJOR problems no doubt but could maybe have found a suitable landing spot. One blade shedding ice and the other/others not will give a ride not soon forgotten.

[blave!]

On a related topic, although Robinson's published range for carb icing is 20-70deg F (R-22 POH), I've heard that Lycoming says 20-90deg. I would tend to play it safe but, would be curious if anyone else uses the Lycoming numbers for conditions conducive for carb icing as their guideline instead of Robinson's. Anybody know why the discrepancy between the two published ranges?

 

Thanks,

Kelly

 

 

The difference is in probable (20-70 deg, high humidity) vs possible (20-100 deg as low as 50% humidity) icing conditions. The 2nd set of numbers make sense when you factor in a carb temp drop of up to 70 degrees with vaporization. Considering many of the northern latitudes experience these conditions virtually year round better safe than sorry. Given that as you mentioned we don't alway have exact humidity numbers readily available in flight, a difference in the spread of less than 11 deg is a good rule of thumb for caution.

[th67]

I just wanted to add a few comments to the previous posts. The original question was "anybody ever experience blade icing?" From my personal experience the answer to that question is no and I hope that it stays that way. I have, however experienced very small amounts of ice that build up on the bubble though. I fly heliskiers in the winter and I am exposed to conditions that are not always ideal. Icing is a very real and very dangerous situation that I try to avoid at all costs.

 

There are many variables that have to be taken into account when it comes to icing. For me first and foremost is the temperature. Next-is the amount of moisture in the air or the RH and also the type of moisture in the air. Flying through rain at 0C is much different that flying in snow. The type of snow that you fly in is also important. Dry snow is not a problem but heavy wet snow is a different story. I have found that when we are flying in temps of -10C and lower that the chance for icing as much less than when the temps are -5C to just above freezing. Now I have to say that I am flying strictly VFR and not IFR which means that I am not intentionally flying in clouds. But I will also tell you that when you are flying in the mountains all day from 7-10,000 feet during the dead of winter that you are going to encounter visible moisture. There are many times that I have to fly through vary thin, wispy type clouds. I always maintain my VFR and more importantly my 135 limits of a 1/2 mile visibility but I do encounter visible moisture at times during the flight.

 

Like I said before the temperature for me is the most important when these conditions exist. I really start to pay attention at about -6 to -5C for any, and I mean any amount of ice build up on the dead spot of the nose of the aircraft and also the metal strip that divides the cockpit bubble. This is where I find that the ice will form first on my aircraft (BH407.) As soon as I detect any ice build up in this area it is either time to find a new place to fly the skiers or to terminate the day and take everyone home. I don't mess around with ice and I guess my point is,like in many situations, i.e. settling with power, retreating blade stall and so on, you need to be able to listen to, feel and in this case, see the hints and clues that your aircraft is telling you. If you can be ahead of the game rather than playing catch up, it is much easier to get yourself out of a bad situation before it ever happens.

 

It doesn't matter if you are flying an R22, an AStar, a Huey or and Air Crane, blade icing can have catastrophic results. Avoid it at all costs. There are very few helicopters that are actually certified to fly in icing conditions. I don't know what percentage of civilian helicopters are equipped with blade de-icing capabilities but my guess is that it is less than 5%. Do whatever you have to to not accumulate ice on your blades. Whether that means to descend to a warmer air temperature, turn around and get out of whatever it was that you got into or simply land and wait for better weather. It is much better to be on the ground wishing you were in the air than to be in the air wishing you were on the ground.

 

I will say this though. Just because you notice a small amount of ice building up on the bubble or nose of the aircraft does not necessarily mean that ice is building up on your blades. Like I said before, if you can pick up on the hints and clues and take the necessary action before it gets any worse you won't have to worry about the possibility of it eventually accumulating on your blades. Take into consideration the speed at which your rotors are turning through the air. At nearly 400 RPM's there is a certain amount of friction caused by the blades and with that friction there is a certain amount of heat being produced. Ice on the bubble builds up first because of the dead air that is present and that seams to be one of the coldest parts of the aircraft. Take this into consideration. On the nights that I leave the aircraft outside I cover it up with all manner of covers. I completely cover each blade individually. The temps at night can get well below zero. -10 to -25F are fairly common temps in the winter. Each morning when I uncovered my ship, there was almost always a small layer of frost, not ice but frost on the blades. Top and bottom. Prior to the guides and clients showing up I would start up the aircraft and ground run it for up to ten minutes to get everything warmed up and ready for the day. At the end of the ground run, after shutdown, I would do a walk around and check for any frost that remained. Not once was there any remnants of the frost. Each and every time the blades were completely free of any frost that may have been there in the morning. The heat produced from the blade friction was enough to melt any frost that had accrued during the night. So my point is that just because there is ice forming on the aircraft doesn't necessarily mean that the blades are accumulating the same amount of ice. Think about the CH-47. There is no way that that aircraft, as big and as powerful as it is could have continued to fly if the blades were covered with up to 4 inches of ice like the airframe was. The engines couldn't produce enough power to overcome the increased weight of the blades along with the drastic decrease in the efficiency of each blades ability to produce lift due to the dramatic changes in the shape of the airfoil. It could fly with the airframe build up of ice and it could handle that change in weight but there is no way that it could have continued flight with that much ice on the actual blades themselves.

 

One more thing. I know that this response is very long winded but I have one more thing for the newbies out there. Especially the robbie pilots. I wouldn't fly an R22 without a functional carb heat either. I had one fail which resulted with me having to ditch an R44 into a lake in the middle of winter. Trust me, it was not one of my better days. But the point is, is that carb heat or ENGINE anti-ice, not blade anti-ice will not prevent ice from building up on your aircraft or your blades. All that carb heat or ENG anti ice is designed for is to prevent the formation of ice building up in your fuel so not to choke off your fuel supply to the engine. Try to keep that in mind.

 

I hope that some of my personal insight will be helpful. I don't have any experience flying in Alaska or in the North East which are entirely different conditions but every bit of advice can help.

[Jeff]

I'm not going up in a carberated helo if the carb heat isn't working. I haven't flown much but I've heard enough about carb icing to know that if the pre-flight check of carb heat fails, I'm shutting down if the conditions are conducive to carb icing.

 

 

Thanks,

Kelly

 

You should shut down whether the conditions are conducive to carb icing or not. Let's say you pull out on the carb heat knob during the pre-flight check, and you get no drop in rpm (or increase in carb temp). How do you know whether the carb heat is off and won't come on, or on and won't go off? Plain and simple, you don't! Even if it is off and won't come on, how do you know that it won't come on--at least partially--while you're in flight? If the carb heat is on and you don't realize it, you won't have as much power available as you might think.

 

Just something to think about...

 

Jeff

[Kelly N.]

I just wanted to add a few comments to the previous posts.

 

 

I hope that some of my personal insight will be helpful. I don't have any experience flying in Alaska or in the North East which are entirely different conditions but every bit of advice can help.

 

 

Wow, a lot of good info. Thanks for taking the time to post it.

 

Kelly

[Kelly N.]

You should shut down whether the conditions are conducive to carb icing or not. Let's say you pull out on the carb heat knob during the pre-flight check, and you get no drop in rpm (or increase in carb temp). How do you know whether the carb heat is off and won't come on, or on and won't go off? Plain and simple, you don't! Even if it is off and won't come on, how do you know that it won't come on--at least partially--while you're in flight? If the carb heat is on and you don't realize it, you won't have as much power available as you might think.

 

Just something to think about...

 

Jeff

 

 

Good points.

 

Kelly

[Jeff]

 

 

It would seem to me that much colder temperatures would be necessary for ice to accrete on the outboard ends of the blades than on the inboard ends due to the speed of the blade tips through the air and the air's compressibility and its associated temperature increase (near the tips). The outside air temperature is not as important as the temperature of the aircraft's surface. For instance, airliners, notwithstanding their highly-capable anti- and de-icing systems, experience less icing problems than smaller airplanes because of the speeds at which the airliners operate. Above about 200 knots, compressibility of the air becomes significant in raising the temperature of the wings and the air near the wings by a few degrees. This, in and of itself, is enough to keep ice from forming on the wings in many instances. (And no, I'm not saying that anti-icing equipment is unnecessary! Just making a point.) I'm guessing that the speed of the last few feet of a rotor blade exceeds 200 knots. This means that lower temperatures would be required to get icing on the rotor blades than on the fuselage. But my thesis does not account for the probability of ice accretion on or near the hub of the rotor blades, which is also dangerous.

 

~Jeff

[goromadgo]

I provided Predator coverage for recovery of a Chinook that went down last year in Afghanistan due to blade icing. Lost a few guys to that, but it was amazing that anyone was able to walk away from the wreck. Wasn't much left to pick up Helos were grounded at night due to icing conditions for awhile after that.

[Gomer Pylot]

If you get blade icing, either you haven't been paying attention or you're in a really bad icing situation. The blades will be the last place ice will form, because they're much warmer than the rest of the aircraft. Their speed through the air warms them considerably - just touch one immediately after shutdown on a cold day, and you'll find it's fairly warm. You'll start getting ice on the fuselage, usually the bottom of the windshield and parts sticking out, well before you start to get blade icing. If you do get blade icing, you're in a very dangerous situation, and had better get on the ground right away, if you have time. You probably already have many pounds of ice on the fuselage, and the extra weight, plus the deformation of the airfoil shape will cause you lots of problems, and if you get asymmetric shedding, you're dead right there. The transmission and everything attached to it will depart the aircraft before you can blink.

[tiercel]

I just wanted to add a few comments to the previous posts. The original question was "anybody ever experience blade icing?" From my personal experience the answer to that question is no and I hope that it stays that way. I have, however experienced very small amounts of ice that build up on the bubble though. I fly heliskiers in the winter and I am exposed to conditions that are not always ideal. Icing is a very real and very dangerous situation that I try to avoid at all costs.

Thanks for your well thought out response. I myself have not experienced blade icing and wanted first hand knowledge of what it's like and what its indications would be. As SIC, I've had ice on the windshield during a ferry flight when I was on the controls, but could not discern any change in sound or vibrations. I will keep your advice in mind in the unlikely event that I ever get to fly in marginal conditions again. Thanks.

[th67]

I am by no means an expert an aircraft icing. I am just passing on a few of my personal experiences with it. I did a little research and this is what I came up with. "A pilots guide to in-flight icing" was the name of the course that I found on a NASA web site. It is worth while to check it out if you have time and want to know more about the subject. A couple of things that were noted was 1. "Icing is most frequent when the static air temperature (SAT) is between +2C and -20C, although ice can accrete outside this range." and 2. "For ice to accrete on an aircraft in flight, there must be sufficient LIQUID water in the air. Water in the form of vapor, snow or, ice will generally not stick to an airplane's external surfaces and contributes little or nothing to the overall ice buildup. If there is sufficient liquid water in the air to pose an icing threat, it will be visible in the form of a cloud or liquid precipitation."

 

Another article that I read was published by the AOPA. It had a little chart that showed the risk of icing based on temperature and type of moisture. Cumulus Clouds were rated as HIGH risk when the temps were between 0 to -20C, MED from -20 to -40C, and LOW at <-40C Stratiform Clouds were a HIGH risk from 0 to -15C, MED from -15 to -30C, and LOW at <-30 and a HIGH risk when flying through rain and drizzle when the temps are 0C and below.

 

Different sources will state different temperature ranges for the formation of ice so take it for what it is worth but it does show that the colder the temperature, the risk for encountering icing decreases. I think that the major thing to emphasize here is what was stated in the NASA article. There has to be "sufficient liquid water in the air!"

 

From what I have read the vast number of aircraft that encountered icing came from flying through freezing rain/drizzle, SLD (supercooled large droplets), or through very wet clouds under the right temperature conditions. Lucky enough for me, during the winter in Wyoming, I don't have to worry about SLD or freezing rain. The majority of the time that I am flying in the mountains the clouds are relatively cold and dry. It is during the spring time, when the temps start to warm up to near freezing or slightly above and the clouds contain more moisture that I really start to pay attention to the possibilities of accumulating ice.

[Parafiddle]

NASA puts out a good video titled "NASA In-Flight Icing Training for Pilots". It is available from Sporty's for $10.00. It is geared for FW pilots (I didn't see any mention of helicopters), however, they have a lot of test footage showing how different types of icing develops, etc. Knowledge is power.