Helicopter blade deicing ideas

[Higgler]

Wondering if anyone has experience with helo blade icing problems and some of the deicing sytems used?

Not allowed in the deicing solution;
1) heated wires on the blades, too much power and it can damage carbon fiber.
2) liquid deicing techniques stored on board, too much extra weight.

I've seen and read some ultrasonic solutions, seems like a direction to go. Or maybe plungers built into the forward edges.

Some thoughts my novice brain has;
1) Is the primary problem at initial starting, whereby ice has formed overnight or is it in flight ice buildup?
2) I realize that blades must be balanced, but do they start up an iced helo blade at low rev's to knock off ice, or do they need to be perfectly ice free to intialize the blades?
3) Are two different deicing systems needed,
a) inflight front edge of blades
b) preflight deicing of entire blade (once snow has been cleared)
4) If one was to modify and add a deicing system to the front of the blade, what's involved with modifying the blade? i.e. mechanical drilling, sealing, etc. I'd expect an entirely new blade design, test, etc....costly..

any thoughts would be appreciated, plus sources of info.
Thanks,


kch

 

[Higgler]

I wish I could go to Spain. I'd like to see where the rain mainly falls. It would require a plane trip.
Kevin
PS: Been on travel alot lately.

 

[IRstuff]

psst... mainly on the plain...

TTFN

FAQ731-376

 

[SAITAETGrad]

I still think the bleed air (or exhaust gas) has merit. Simply leave proviles for air to move close to the surface, spanwise to the tip.

 

[IRstuff]

Holes and hoses accumulate water, which once frozen, requires a heater. Gee, weren't we here already?

For those non-believers, we had a system that sat on the mast of various ships. The system constantly accumulated water INSIDE the housing, just through simply respiration through its so-called "seals." One time, we got up to 5 inches of standing water, supposedly accumulated over the course of several months. Had nighttime temps dropped below freezing, we would have had a literal frozen popsicle.

TTFN

FAQ731-376

 

[kenvlach]

What about hydrophobic coatings, e.g., Teflon®?
If not durable enough on its own, some rotor bladea with aluminum leading edges are hard anodized, and the anodizing can be Teflon®-impregnated.

 

[Higgler]

We researched hydophobic coatings for shipboard radomes. The US Navy didn't like the 6 month re-application timetable so they nixed it. I don't think we discussed ice formation.

I would think it would work pretty well if it could handle the air pressure, but I'd guess it couldn't handle it. As it was described to me, hydrophobic coatings are put on in two steps. The resultant surface is close to a "tiny bed of nails" whereby the water balls up on the nails since it can't run down between the nails due to surface tension (wonder if surface tension of water is less at higher altitudes). Anyhow, I'd picture the super high wind force would rip off the coating on the front edge of the surface, but maybe it could handle it on the top, bottom and back of the rotor. Since that material has been around for awhile, I'd expect someone has tried it. Good thought though, I'll take a look at it on the web and see how tough it is.
Thanks,
kch

 

[WKTaylor]

Higgler...

Suggest you review SAE AIR 1667A "Rotor Blade Electrothermal Ice Protection Design Considerations".

Regards, Wil Taylor

 

[Higgler]

Thanks, I'll take a look wktaylor. The present requirement looks for a minimum of power required, hence the recent discussion.

kch

 

[thruthefence]

There is a "anti-ice" system, known as TKS, that 'weeps' a glycol solution thru thousands of tiny holes in the leading edge of the wing. Note this is an "anti-ice" system, as opposed to a "de-ice" system, in that it must be actuated before entering icing. I think it was developed in the UK, and was first used on the Hawker series of business jets. It is also used on the Citation 550 SII , and on the single engine Cirrus aircraft. I suppose one could design a 'slinger ring' device to get it to the blades, tho It makes a hellava mess when operating.

 

[WKTaylor]

Folks..

An interesting Article in the Seattle Post-inteligencer follows...

http://seattlepi.nwsource.com/business/1310AP_Water_repellent_Coatings.html

Last updated June 27, 2007 9:18 p.m. PT

Water-repellent coatings hold promise
THE ASSOCIATED PRESS

AUSTIN, Texas -- Aircraft that won't accumulate ice while awaiting winter takeoff. Engine parts with self-cleaning capabilities to boost efficiency. Even automobiles or toilet bowls that require little to no washing. All could be commonplace someday if ongoing research proves successful into "superhydrophobic" - or extremely water-repellent - coatings that are durable enough for metal and ceramics. The idea is that moisture will simply bead up and roll off, picking up dirt particles along the way.

The opportunities are "pretty incredible," said Margaret L. Blohm, who manages the nanotechnology program at the General Electric Co. research arm.

GE's coatings, tentatively expected to be ready for commercialization in five years or so, will probably first target the energy and aviation industries, Blohm said. Other scientists engaged in similar research believe consumer-oriented uses - think self-cleaning cars - aren't too far off, either.

There's little doubt the market for such technology could be lucrative, if it can live up to the early hype.

The aviation industry, for instance, spends large sums to remove ice from airplanes and render them safe for flying. AMR Corp. unit American Airlines alone pays more than $10 million annually for deicing fluid and another $1 million for employee training, according to the company, figures that don't include equipment or lost time and fuel.

But ice wouldn't adhere to an airplane wing finished with a thin, "superhydrophobic" coating.

"We think (GE's effort) offers great promise if in fact it can be applied to aircraft," said Basil Barimo, vice president of the Air Transport Association, a trade group that represents major carriers. "I'm sure the airlines would love to get out of the deicing business."

Blohm said it's too early to estimate the price for such coatings, although she noted that GE's goal is to make them cost-effective for customers.

Research into so-called "hydrophobicity" - or the properties of water repellence - has been focusing for the most part on the surface structure of the lotus, an Asian plant that retains a pristine appearance despite thriving in muddy waterways.

Among other things, the texture of the plant's surface, which consists of microscopic "hills and valleys," creates a thin layer of air that prevents full contact with water or dirt. As a result, water rolls off its leaves, taking the dirt with it.

In recent years, various long-lived coatings have been developed that are modeled after the structure. Products incorporating such technology range from new lines of spill-resistant clothing to house paint dubbed as self-cleaning.

But duplicating the lotus structure for use on steel and other metals has been more problematic.

For one, metal is naturally "hydrophilic," meaning moisture tends to slide, or smear, on it instead of beading up. Metal also is difficult to mold because of its high melting point.

In addition, metal and ceramics often are deployed in extreme conditions - as an engine part, for instance - so any suitable finish must be exceptionally durable.

Fairfield, Conn.-based GE has had success in the lab formulating lotus-style coatings for metal and ceramics and has a number of patents pending, Blohm said, although she declined to reveal precise details of the technology.

Other researchers doing similar work have reported strides as well. C.P. Wong, a scientist at the Georgia Institute of Technology, said his effort to develop a titanium-based "superhydrophobic" coating for use over steel is showing substantial promise.

But both Wong and Blohm said increasing the durability of their respective techniques remains key.

"Durability is the most important aspect for commercial applications," Wong said.

Tentatively, Blohm estimated that GE's initial coatings will last 10 years on the outside before needing to be reapplied or replaced in some fashion. She also considers the most viable early uses for GE's coatings to be those in which "the robustness requirements are less severe."

Examples she cited include gas turbines, in which certain internal parts experience minimal wear but would gain a substantial improvement in efficiency from a self-cleaning capability.

Likewise, such coatings would be valuable to the aircraft industry even if minor chips or worn spots developed over time and left tiny ice patches on planes, she said.

Barimo, of the Air Transport Association, concurred.

"It doesn't have to be a perfect solution, where the aircraft is always pristine," said Barimo, who was familiar with GE's effort. "Even if it just trims a little time off the deicing process ... there are benefits there."

GIT's Wong said he's already been contacted by some interested manufacturers, and he contends that the days of self-cleaning toilets, solar panels or automobiles are a mere two to three years away.

Still, Wong acknowledged he has plenty of work left to do.

"You have to use a lot of really tough materials," he said. "If you lose the durability or the appearance, you'll lose the customer interest."


Regards, Wil Taylor

 

[MikeHalloran]

I'm always suspicious of such "forward looking statements".

On the other hand, you could just try a little Rain-X.

Mike Halloran
Pembroke Pines, FL, USA