Rotor anti-icing
 

Having no experience of a helicopter fitted with a rotor anti-icing system, I'm after some first-hand knowledge from people who have.

Are they mainly heater mat/ mast slip ring type systems?

Are they reliable, serviceablility wise?

Are they maintenance intensive systems?

Are there any operating limitations....such as electrical power consumption or aircraft performance?

Do they operate off of essential or main bus?

Thanks in advance for any information.

While I have no direct experience with these systems as a pilot, I have spent some time around them and may be able to answer a few of your questions.

Most systems do use electrical heater mats in the blades with mast mounted slip rings to transmit the power from the fixed to rotating system. The systems I am familiar do not use an anti-ice approach (like an engine inlet) which would require keeping the majority of blade warm all the time and would need an enormous amount of electrical power. A de-ice approach is commonly used where a limited of ice is allowed to build up on the blade leading edge and then a heater mat is energized, heat "melts" the bond of the ice to blade allowing the ice to "shed" due to Cf. The blades may be heated in zones and/or pairs to minimize vibration changes, torque rise and electrical power requirements. The frequency and duration of the heating cycles are adjusted by system based on the liquid water content (LWC) and temperature the aircraft is operating in (determined by ice rate sensors). Too much heat for too long could allow the melted ice to run back and refreeze on an unheated area of the blade or high temperatures could damage composite blades. Failure modes and impact (pun indented) of shed ice must be considered for certification.

As the brochure says "these are highly reliable, modern digital systems with built in redundancy, fail-safety and include manual mode backup to the fully automatic mode, self test and diagnosis capability." The operational reality, of course, is that controlling and moving significant amounts of electrical power through flexible wiring to heater mats in highly loaded whirling, flapping, flexing main & tail rotor blades while in a wet environment might provide the occasional engineering/reliability challenge. Or as the program manager says "we are constantly working to improve our highly reliable products".

Scheduled maintenance is relatively limited with brush block inspection / replacement, slip ring inspections, and perhaps bearing life replacement, wiring harness and blade heater mat checks. YMMV with unscheduled maintenance - a "simple" heater mat element failure could require blade removal/replacement & overhaul.

Aircraft performance can/will be effected by the de-ice system due to the decreased average aerodynamic efficiency of the blades as ice builds and then sheds (and other factors including the need to consider the built up of ice on the airframe). Any performance changes or other limitations will be defined in the RFM.

These system require significant electrical power, some operate on the #1 and/or #2 AC Primary Bus. Some aircraft are fitted with an additional generator for the de-ice system.

Thank you Hank.....very informative. What you have described sounds very similar to prop de-icing, with the added hazard of rotor imbalance and bits of ice flying off into who knows what. I've experienced the disconserting feeling of hearing ice coming off of turbo-props and impacting the side of the aircraft.

Is rotor de/anti-icing used on tail rotors also?

Any pilots with experience of such systems care to comment?

The tail rotor blades on many types are often naturally kept free of ice due to the heat from the exhausts so it's not so much of a problem. The Super Puma derivatives have a cowling to keep ice off the tail rotor control mechanism

Is there not a third generator on the 332's that have De-Icing capability?

Anyways, my friend who used to fly them out of St. John's once told me that the machine would start to yaw to the right as the ice started building, then violently kick to the left, every time the heat came on, which I believe was quite frequently...

Cheers
H.

I fly Mi-8/17 and I dont remember that we ever had problem with anti-icing.
main & tail rotor, front windsheeld & particle separator is electricly heated, engine inlet with warm air... :ok:

What type of ice detecting system does the S92 have? It looks like a vibrating probe type, but difficult to tell from the picture I have.

My memory doesn't serve me too well these days but I flew AS332L LN-OMI which had full de-icing and yes I believe there was a 3rd Alternator. If not a 3rd then beefed up 2 others. We also had a pneumatic leading edge on the horizontal stabilser which inflated and deflated sequentially which had a gentle but interesting attitude change. You would be flying along and the nose would go down a bit and you thought "well at least the stabilser boot is working!!".

Maybe those Norsk guys who worked out of Hammerfest could enlighten you more :)

John

The 332 only has two alternators. The standard version has two 20/30 KVa alternators, while the De-Ice version has two 30/40 KVa alternators.

The APU generator on the 92 produces 35 KVa continuous, and 45 KVa for 5 minutes.

The main generators produce 75 KVa.

speaking of midgets
 

The Merlin/Cormorant/EH101
...two 90 kVa gens
and the 25 kVa APU that can be tied into the the Ess Busses:ok:

some of that 15 tonnes comes in useful...

...especially with a little ice:E

The AW139 and EC225 also use heated mats & slip rings.

The AW139’s FIPS system uses one 45 kVa and one 25 KVa generator, plus Goodrich duratherm mats. The MRBs use a ‘zoned’ heater mat approach.

The EC225 uses 30/40 kVa alternators (like the SP), with the MRB heater mats’ heating ‘cycle’ varying according to the external temperature.

I/C

Thanks for all the replies...all the type of stuff I was looking for.

No need to go back to the books Ironcheffley, unless you want to that is.

The optical probe for ice detection was mentioned for the S92. What do types such as the AW139, S76 and the good ol' S61 use for ice detection?

I'm afraid I'm from the little brother brigade, where the uncommon event of ice detection is on the door hinges and the windscreen wipers. Oh yea....there was also that calibrated bar thing that stuck out the side of a Lynx.

.
Rotor icing research initiative at Penn State: Penn State Live - Lab focuses on new technology to prevent icing on planes, helicopters

I've been flying de-iced Pumas in icing conditions quite regularly for the past five years. There are two heavier generators, not a third, but there is additional AC buses (although I was told by my instructor (Aberdeen) that there is a third generator on the initial type course, but I highly doubt such a thing exists), and there is a slight increase in fuel consumption with the kit on. I've never seen nor heard of the kick mentioned earlier when encountering ice or putting the kit on, it's quite seamless. Operations dictate turning the kit on before flying into icing conidtions, ie punching into cloud below zero, but if you should encounter ice without the kit on, if you don't notice it on the wipers/mirrors first, you'll see a slight increase in torque, maybe 4% or so, and turning the kit on has the torque dropping to normal in seconds. I've seem some pretty heavy ice accumulation but the kit works flawlessly and I have never needed to go to the severe function, which reduces the time between heating blade elements for heavy conditions. We often launch in heavy snow/solid IMC/winter/below freezing and fly a four hour sortie in the clag with the kit going the entire time, and the aircraft doesn't appear to mind at all. It works very well, and everyone I know that flies in icing condition regulary develops alot of faith in the sytem. Coming off of the S61, everyone was quite wary at the start, venturing into conditions tentively with a solid out, but the kit just works. But being pilots, we still like to have options/outs in our back pockets.

.
Bladestrike: (A somewhat ominous username! ;)).

Which type of Puma are you flying and could you describe (for the uninitiated) the basic anti-ice system installed (ie: how it works).

Could you elaborate?

I think it was the late great John 'Chalky' White (ex-RN) who told me he flew Wessex in Norway on icing trials where the mrpm drooped so low so as to significantly exceed garment-soiling point! Or was that someone else?

Sav

Sav

Read an article a few months ago, cant remember source, but the issue was to do with de-iceing on rescue helicopters and their potential to fail at times. The article specifically flagged up the danger of flying through such conditions only for the system to fail, and then be effectively trapped on the wrong side of such weather trying to make good a return to safety but one that puts the aircraft now without any such operational system being forced into iceing conditions and the resulting dangers. Food for thought?

.
Bolkow: This question was precisely what I had intended asking Bladestike once he explained the basic operating system in use on the Puma he flies in his four-hour-long freezing-cloud-immersed sorties.

At the risk of looking like a 'plonker' what do they use .. heated elements on the leading edge of the blades?

Sav

Yes, which also means a slip ring (which will be heavy) at the head to pass the electric current and big generators.

Savoia,

That is why the designs have a backup incase one fails.

The Sultan