Blade Icing

[Dynamic Component]

In theory, if you start getting ice on you blades in the cruise you should notice it by a vibration to the aircraft and the airspeed should slow down with a fixed power setting to remain at the same altitude.

As I have never experienced this before, can someone out there tell me if this is only in theory or not??

[Ascend Charlie]

Even before you lose speed, the torque will go up as the drag on the blades increases.

Sikorsky has a very good video on blade icing (starring Pprune's resident ace from space, Nick Lappos) which I saw at FSI recently. Dunno where else you could see it.

It was enough to give me a scare, having always been told to watch for the first signs of ice on the Huey's wiper blades. By the time you see it there, you are already in deep 5h1t.

[Aesir]

I have encountered some unexpected icing in B-222, enough to cover the front window with rime ice and the nose and wings (wing stubs!) had 2cm (almost 1 inch) rime ice covering the leading edge.

This happened at about 2000´ca 10Nm from destination and the ice accumulation was over about 5 min period.

I never noticed any unusual vibration or decrase in airspeed and upon landing at destination there was NO ice at all on the blades.

So I´m pretty happy about flying the B-222 in ice prone areas, although I try to avoid it at all costs.

[Mikila1A]

ICING and how to deal with it...?

1. Place coffe in cup holder.

2. Place magazine on lap of non flying pilot, careful not to wake him.

3. Stretch.......one would not want to pull a muscle while performimg task # 4.

4. Reach down to those three little buttons on the left side of the pedestal and push them all in.

5. Resume with coffee and latest Helo mag, again careful not to wakin NFP.

BTW.... only follow these rules if your driving a de-iced 332.


if not, avoid the stuff,

[taxying]

ICING¡¦¡¦¡¦yikes ! Blade icing is the bad one

Unfortunately , the helicopter I fly ( a well established medium twin), does not have a BLADE de-icing or anti icing system¡¦.oh , I wish

I have experienced airframe icing but at the same time no blade icing. Conversely there have been times (not often) when I have picked up blade icing but hardly any airframe ice. On one occasion , years ago in a 61 , we picked up ice on the windscreen and its appearance was almost explosive. One minute it was clear, the next , completely white.

Referring back to my regular medium twin , its particular blade shape , I am told , is susceptible to icing. Another well known medium blade shape , not so.

I believe that it is extremely hard to predict icing conditions but particularly BLADE icing conditions.

I am led to believe that the friction of the rotating blade against the air causes an 8¢ª C rise in the blade temperature so that BLADE icing conditions will only be met when it is lower than minus 8¢ª at your altitude and you are flying in visible moisture. ie cloud.

So , in my area , we are forever being handed forecasts (in winter) that indicate enroute moisture and temps below minus 8. Note that this is FORECAST icing. Bear with me while we go to the dictionary. Forecast means ¡°estimate in advance , especially to predict¡¦..predict as in prophesize¡±

The Flight Manual of our medium twin referred above ¡°prohibits flight in KNOWN icing conditions¡±¡¦..and this is my point. We do not know , until we get out there and in it.. If we did not launch every time we were handed a FORECAST indicating icing conditions , then we would have to shut down over winter. Further more , I have flown regularly in these conditions and have not experienced blade icing ( or any other icing for that matter) when I was half expecting it. It is a real quandary.

In this particular medium twin , we set 62% cruise torque and watch it intently. If it starts to rise , we have flown into KNOWN icing conditions and we usually have two options. 1. Turn around and go back home or 2. Climb out of the cloud (moisture) and into the sunshine where the ice will burn off. Descending is not an option when sea level OAT was below minus 8 (and as low as minus 20). The decision to get out , must be made right NOW or you end up at 100% torque with IAS dropping and eventually the aircraft heading in the direction of down.

I have heard some real horror stories but what it boils down to is that manufacturers MUST fit those three buttons mentioned previously , if they are to sell their helicopters to cold weather operators.

[RDRickster]

HELIPROPS A.D.

If you subscribe to the free "HELIcopter PROfessional Pilots Safety Program" (HELIPROPS), there is a good article on page 7 about vibrations caused by icing in a UH-1. To summarize, while in IMC the ship experienced lateral vibrations that would build in intensity and then they would feel a jolt with no more vibrations. These events would repeat several times. Apparently, they were taking on ice and then shedding it off.

Although sponsored by Bell, the articles are focused on helicopter safety and include many other types (MD, Robinson, etc). It's free, it's pretty interesting reading, and you'll receive them about once a month or so...

Bell Helicopter Textron, Inc.
Jim Szymanski, HELIPROPS Manager
P.O. Box 482
Fort Worth, TX 76101

OR

Fax [phone]

OR

[email protected]

[Randy_g]

There are only 2 places I like ice:[list=1][*]in my drink[*]under my hockey skates (I'm Canadian, eh !!)[/list=1]



Cheers

[Aesir]

Good article "taxying" but surely you have not had these ICE experinces in Hong Kong as your homebase indicates!

Mikila 1A. I don´t know where you operate, but the Super Puma pilots I know who operate in very real icing conditions are not to happy about the de-icing function on the AS-332.
Do you really fly in "REAL" icing conditions and do you feal that the rotor blade & T/R de-icing works satisfactory? I have heard some horror stories.

On the other hand.. I have talked to Russian ğpilot who fly the Mi-17 in heavy ising conditions in Siberia and they were very happy about the de-icing/anti-icing capabilities of the Mi-17. They have a little indicator on the left side (Captains side in Russian ships) that shows the ice buildup. They say that when the indicator almost disappears (its about 4cm long) they start to worry, but mainly due to increase in weight, the blades stay clean!

[taxying]

quite right Aesir.....not in HKG....that is just my letterbox/rotation point.....

would be interrested to hear from the North Sea types and of course the Canucks from whom I have gathered the previously mentioned horror stories.

[Mikila1A]

Aesir,

My reply was meant in fun and please take it for that.....

but yes, we do operate in "Real Ice" and lets be honest, who really wants to operate in ice givin a choice. The de-ice gear will be installed on our a/c within the next month and will not be removed again until April, in the time frame we could not complete our jobs here safely and effectively without it.

Does it work...very very well.

The only other group of drivers i know that fly in more ice then us (amount and frequency) is the Icelandic Coast Guard. Talked to some of their drivers at the sim just last year and it was suprising how much more they will operate in, with little to no problems.


Although,
The tropics is much more appealing then the cold north atlantic at night in January with 60+ knots of wind.........know of any jobs?

[AirJockey]

If you encounter ice and are over, or near the ocean, get over it and go down to about 200-500`and your ice will in most cases melt of the blades.
If you fly innland and encounter ice, get down on the ground and wait out the weather. Freezing rain should be avoided at all times!!

To your main Q. The best way of recognising ice is the Tq. If you are temporaly in a cloud and expect to brake out in a few minuts, then leave the collective in it`s position as long as the Tq. is withing the green arc. This is done to have controll over the ice melting of the blades. If you lower collective, you will not have the same controll over how much ice you still have on the blades.
You will have to take in to consideration a lot of factors to do this, like aircraft weight, altitude, mountains, area clear of ice(FC). This is anyway how I was tought to do it from one of the pioneers in offshore flying.

Hope I helped a little......

[NickLappos]

Been in too much natural ice, mostly in the NE US. Also flew interesting trials at the spray rig in Ottawa.
Lots of information, but here is how I see it (PPRUNE comments are welcomed!):

1) Ice Forecasts are not necessary. Ice is almost always available in clouds below feezing temp. If it is visible moisture, and it is below freezing, you will probably get ice if you fly in it.

2) The ice on your blades can form even if you have no ice on your airframe. The blades are in a different environment, and the speed and shape of them can allow ice to form on them while your windshield and wipers are completely clean. And vice-versa, your windshield can get glazed over with thick ice, and your blades can be completely free. (Go figure!)

3) Be aware of the torque your engines are producing for the cruise collective setting, that is your only predictable cue to the formation of ice. When the blades get "ice cholesterol" (a wise guy term for clogged with ice) they get a brand new airfoil, invented by the weather, and it is not the airfoil the designer wanted. the drag will be higher and the lift will be lower, so the torque (MP) will start to climb up all by itself, for the same collective setting. Best way to find out if you are getting ice is to leave the collective alone, and just watch the torque. In ice, with constant collective and altitude, the torque will creep up while you are watching. New airfoils (like those on all newer helos) are more susceptable to loss of performance because they have lower drag than the old 0012 airfoil everybody used in the 60's and earlier.

4) If you are in ice, you are coming down unless you get lucky. The ice will grow if you stay in the ice cloud (it is actually a cell inside the cloud that might end in 100 meters, or might be miles long). If you get lucky, the ice will stop growing, and even sublimate into the atmosphere as you continue to fly (the torque will magically go down to the original torque). A 180 degree turn is a very nice option, if ice is forming and you catch it in time.

5) If you break out into the clear, the ice will probably sublimate. I escaped an ice situation once by turning toward a bright patch, and when I popped from the side of the cumulus I had been in, the bright sunshine and clear air cleared the ice in about 30 seconds. I went from absolutely no climb at Vy to normal cruise speed at the same power.

6) Ice will shed if it gets thick enough, but your performance will be nil by that time. If your flight performance is nil (lots of power, but you are descending) then you can bet your autorotative performance is also nil, could be that you can''t even hold the rotor in the green in autorotation at bottom collective.

7) Breaking out over warm water is a nice option, if you know the clouds don't go to the water, and that the air over the water is warm. This works in the North Sea, and is near suicide anywhere else.

8) Keep the engine protected with anti-ice whenever there is visible moisture near freezing temps. Never let it go off. Most engine installations are fully ice protected even when the rest of the aircraft is not, at least for Part 29 helos. Ice will kill an engine very fast.

9) Best way to handle helicopter ice is stay out of clouds that are cold. Period. If you fly IMC and expect that only forceast icing is a problem, you will become a PIREP in a heart beat.

10) De-iced blades is a great thing. In most parts of the world, as important as being equipped for IMC, I think.

[Mikila1A]

Whoa Nick.........

Ya took the words right outa my mouth.....

Last time (first time actually) we talked in person I was suppose to send you those photos of the 332 buried in ice.....

still want them?

[NickLappos]

Mak,
That would be great, can you email a few to me at work
N