Flight in Icing Conditions
"icing conditions" is a term often thrown around without a lot of definition. You can fly in cloud for years at -20C to +2C and never pick up ice. You can have the sponsons and wipers caked with ice and never see the torque change. Do we want to talk about potential icing conditions, forecast icing, known icing....? Give the manufacturers and regulators some rope on icing language and you'll guarantee you'll never fly.
Are you talking about RFM limitations or what actually happens on a day to day basis?
At -30 and -40 the air is dry and not usually much of an icing problem. Supercooled ground fog can be a problem as it can build up on the blades pretty quick. Not much flying goes on when it gets below -40. Old aircraft like the 212 and 61 fly IFR in the arctic and antarctic all the time. The 76 too, although it can't carry the ice a 212 can. By comparison, I've never seen any of the 139 guys poke into a cloud when the OAT gets less than +2. I hear they want to operate a 139 out of Tuk this winter so we'll finally see how that type carries ice. With all that power I expect it would do pretty well.
Airframe icing has never seemed to be a problem to worry about with any type. Its the stuff building up on the main rotor blades and driving the TQ up that gets your attention.
Are you talking about RFM limitations or what actually happens on a day to day basis?
At -30 and -40 the air is dry and not usually much of an icing problem. Supercooled ground fog can be a problem as it can build up on the blades pretty quick. Not much flying goes on when it gets below -40. Old aircraft like the 212 and 61 fly IFR in the arctic and antarctic all the time. The 76 too, although it can't carry the ice a 212 can. By comparison, I've never seen any of the 139 guys poke into a cloud when the OAT gets less than +2. I hear they want to operate a 139 out of Tuk this winter so we'll finally see how that type carries ice. With all that power I expect it would do pretty well.
Airframe icing has never seemed to be a problem to worry about with any type. Its the stuff building up on the main rotor blades and driving the TQ up that gets your attention.
Pretty sure blackhawk and seahawks have de ice for the main and tail rotor blades and are certified for flight in icing conditions (not sure about minimum temperatures though).
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One of the little known issues about icing is that the approval is only for droplet sizes smaller than 50 microns - that's the size of a 0.5mm mechanical pencil. This is pretty small.
Anything larger than 50 microns is freezing precipitation, and there is no approval for flight in that.
Not many people know this.
Freezing precip is much nastier than the stuff that is tested and approved.
Even fixed wing aircraft have serious problems with freezing precip.
As far as cold weather as separate from icing, lots of helicopters are cleared to the colder temps.
Anything larger than 50 microns is freezing precipitation, and there is no approval for flight in that.
Not many people know this.
Freezing precip is much nastier than the stuff that is tested and approved.
Even fixed wing aircraft have serious problems with freezing precip.
As far as cold weather as separate from icing, lots of helicopters are cleared to the colder temps.
We fly deiced Super Pumas in ice all the time, it's certified as long as it's not freezing rain/drizzle/heavy icing. It's really something to shoot an approach to mins in a snowstorm at night, the transition to visual is some of the hardest flying I've done, I almost preferred flying the S61 where you couldn't be out in that stuff, but it does beat scud running. It doesn't get below -20 C here on the East Coast, but I've had ice in cloud from -2ish down to -15 C, I think in colder temps you just might get some at the tops. With the Puma, there's really no need to try to get out of it, to climb on top or descend below, it chugs along happily with steady build up. I was doubtful when experienced deiced Puma pilots told me you just don't worry about it, but after a few winters under my belt, I'm sold.
Last edited by Bladestrike; 28th May 2008 at 21:05.
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S92 icing certification
On another note,I was talking recently to a man who was involved with the S92 icing certification.The S92 was flown behind a tanker which released water into the path of the encoming 92 which would then build up ice on the airframe for evaluation.I was fascinated.
Then I wouldn't recommend applying for a job on Canada's East Coast. The customer has people and platforms in a very harsh enviroment, they are willing to pay a great deal of money for the capability to fly when it's required. I don't know the stats but a non-deiced bird was not getting the job done. There are aircraft capable of flying in icing conditions when the demand calls for it. I didn't like the idea at first either, despite what I was told by everyone flying these things, but we eased into it and it has proved very capable. So to answer the original question, yes there are Western aircraft that will fly in icing conditions, there are limits of course.
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Don't let anyone tell you you can not get blade ice at -40. Although Malabo is right, USUALLY the air is too dry, that may not be the case over open water.
Also, the most dangerous temp for a helicopter is approx -7 and below depending on blade length and RRPM. I used to have the formula that would determine blade temps in relation to length and RPM, but I burned it along with my parka when I left the arctic
As the temp decreases from zero ice will start to build on the head and move outward. You will not notice too much of a problem with Q until it starts to affect the outer 1/3, again around -7. Of course if you need to autorotate the inner 1/3 is pretty important as well
Also, the most dangerous temp for a helicopter is approx -7 and below depending on blade length and RRPM. I used to have the formula that would determine blade temps in relation to length and RPM, but I burned it along with my parka when I left the arctic
As the temp decreases from zero ice will start to build on the head and move outward. You will not notice too much of a problem with Q until it starts to affect the outer 1/3, again around -7. Of course if you need to autorotate the inner 1/3 is pretty important as well
When I was flying the Lynx(which is 11 years ago now 
), it was cleared for 30mm of clear ice and 60mm of rime. I think that the most I ever had was 6mm of rime.
), it was cleared for 30mm of clear ice and 60mm of rime. I think that the most I ever had was 6mm of rime.
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my experience for icing conditions:
332L : certified and very capable
212, 61, 76, 412 : uncertified in decreasing order of capablility from good to horrible
not certain of actual minimum temperatures for certification but I remember it being an issue in the 412 below -40.
the 332L doesn't like being shut down in those conditions without a nice comfy hangar and ground power.
hope that actually answers your question.
332L : certified and very capable
212, 61, 76, 412 : uncertified in decreasing order of capablility from good to horrible
not certain of actual minimum temperatures for certification but I remember it being an issue in the 412 below -40.
the 332L doesn't like being shut down in those conditions without a nice comfy hangar and ground power.
hope that actually answers your question.
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I have a very vivid memory of sitting tight in Unst while another 'braver' pair of chaps went off in their 61 on a not so fine morning. Their assurance that they could get rid of any ice by hovering over the sea didn't really convince me that either of them, experienced as they were, really understood what was about to happen.
About 30 minutes later they re-entered the crew room, where I had cosily sat with a fresh cup of caffeine. Both were grey and quite jittery. I asked a simple question.
"If hovering over the sea will get rid of ice building up on your blades, how come ships accrete ice like a lollipop in arctic waters?"
About 30 minutes later they re-entered the crew room, where I had cosily sat with a fresh cup of caffeine. Both were grey and quite jittery. I asked a simple question.
"If hovering over the sea will get rid of ice building up on your blades, how come ships accrete ice like a lollipop in arctic waters?"
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Certified for known Ice!
Is the question which helicopter is "certified for known ice" at -50?
As we can see it just takes a certain person to push these limits, so it seems the list is endless (unless you look at certfied temps, most being -45C as a lower limit).
I cannot find one helicopter that would be certified in "ice" at -50C.
not Puma nor 92 as temps limit this operation.
As we can see it just takes a certain person to push these limits, so it seems the list is endless (unless you look at certfied temps, most being -45C as a lower limit).
I cannot find one helicopter that would be certified in "ice" at -50C.
not Puma nor 92 as temps limit this operation.
