Let’s take a break from some of the more depressing subjects out there (eg, labor strife) and talk about something cool. Once again, science has proven its awesomeness with a “nanostructure surface” that can make metals repel ice. This would be huge for aviation in so many ways.
Thanks to the Ideas Market blog over at the Wall Street Journal, I found out about this paper put together with the thrilling name “Liquid-Infused Nanostructured Surfaces with Extreme Anti-Ice and Anti-Frost Performance.” Sounds thrilling, right? Let’s talk more about what it actually means.
Airplanes and ice have a love-hate relationship. Airplanes hate ice, but ice loves cozying up to a wing or a tail and causing all kinds of problems. Airplanes are built in very specific ways to ensure that the wings can provide enough lift for the aircraft at various speeds. When ice builds up on a wing, it disrupts the airflow by altering the shape of the wing surface. Even minor changes can have a major impact on lift. The list of accidents due to ice is very long, but some of the more famous are the Air Florida accident at Washington/National and the American Eagle crash over Roselawn, Indiana.
Icing can be a problem at any stage of flight. Before departure, it’s incredibly critical, and that’s why airplanes will “de-ice” before taking off. Have you ever sat at the gate and all of a sudden seen a nasty liquid being sprayed over the aircraft? That’s deicing fluid. Sometimes, it will happen at the end of the runway right before takeoff. Different airports have different ways of dealing with it and the various conditions will impact how often it needs to happen and where. The fluid is meant to melt any ice that might be on the airplane. There is also an effort to use “anti-icing” to create a temporary barrier to prevent ice from forming again. In severe icing conditions, this may not work for very long. As we saw with the Air Florida accident, waiting too long in bad weather can very easily result in disaster.
In the air, it’s a different story since it’s not very easy to find a way to spray the airplane up there. There are three ways to de-ice in the air. Some airplanes (like the one that crashed in Indiana) use de-icing boots that sit on the leading edge of the wing. They inflate to break the ice and then it blows off in the slipstream. There is also a system that uses “bleed” air, meaning it takes air that is diverted off from the engine. The heat is used to melt the ice. Additionally, there are mechanical heating systems that can heat the wings to melt ice.
All of this is no fun and it’s costly. The deicing systems add weight to the aircraft. The need to deice on the ground snarls traffic and delays aircraft left and right. This doesn’t even address the issue of disposal of the deicing fluid. It’s a real mess. So if there’s a way to prevent ice from forming and have it built into the wing, then there should be a huge market for it.
What is being proposed is the use of what they call “SLIPS” — slippery, liquid-infused porous surfaces. Catchy acronym. But, um, what? Well, a previous study gives a little more light into what this is. You start with a “nanostructure surface,” which is really something very, very tiny with little itty-bitty holes in it. Then you infuse a liquid into the holes that naturally does not mix with water. You’ve all done the experiment as a child putting oil and water together only to see them stay separate, right? It’s that idea. So when water comes into contact with this surface, it will be repelled and ice won’t form.
Yes, the idea is simple and extremely awesome. And apparently, it works in some very cold temperatures. These SLIPS are just applied to metal surfaces, so they don’t require any special type of metal. The potential for something like this is tremendous.
I’m sure we’re still fairly far out from having a workable application, but the idea should have bean counters and ops folks alike salivating.
Sounds like a nice idea, but how far is this from a) Trial by Airbus / Boeing, b) Tentative approval by relevant Govt Aviation Authorities, c) Going into use on an aircraft carrying passengers ?
Suspect that it’s all still quite a few years away
Most assuredly it is several years away, but the concept is sound. You can buy pants now that are infused with nano particles that assist in repelling stains. Most sunscreen you buy uses nano-titanium and other nano-metals to “repel” harmful UV rays. When I was doing my graduate studies I worked around the nanotechnology lab and they were working on a nano-scale delivery mechanism for chemotherapy drugs. The chemo would be direct injected into an individual cancer cell.
There are huge potential upsides to thinking on the nano scale. Now, I worked on the ethics side of the coin and there were many concerns about ethics, disposal, safe handling, etc. As with all science there is a double edged sword lurking under all the discoveries. Still, if we could remove or substantially reduce the instance of icing on aircraft the benefits would be huge. Reduced pollution from the glycol, reduced delay, reduced change of incident. It would certainly be a huge plus.
Quite a ways I would imagine. I imagine the FAA is going to want a significant amount of substantiation before they approve this as an alternate method of compliance for de-icing requirements and flight into known icing conditions…
I understand the benefit to airplanes, but this would be huge for helicopters.
There should be a health study on the current system of de-icing planes. At the end of most winters, there’s so much GLYCOL fluid, de-icing fluid on the ramps and taxi-ways, that it’s ingested into the engines and bought into the CABIN through the air vents. I visually see it all the time. A light haze in the cabin. Niiiice, we breath that in: http://en.wikipedia.org/wiki/Deicing_fluid#Chemical_Composition
Given the EU’s use of the precautionary principle I would have been surprised if they didn’t have such a study already so I did a quick search.
It turned up that there are EU regulations around propylene glycol, but it is focused on food safety. European legislation limits the presence of propylene glycol as food additive to 1-3 g/kg in the final foodstuff (0.1-0.3%). A full acceptable daily intake (ADI) of 0 ? 25 mg/kg bodyweight has been assigned for propylene glycol by the European Commission´s Scientific Committee on Food.
Ethylene glycol has some very strong studies linking it to reproductive issues, but the exposures are higher and longer than what a passenger would experience. A crew however may be subject to high enough exposure levels. (ec.europa.eu/social/BlobServlet?docId=3865&langId=en)
Wow, thanks Jason. I fly some 40 to 50 flights per month. So, exposure to these chemicals do concern me. Crewmembers do have a variety of work related concerns. Radiation exposure, Ozone toxicity, recycled air, airborne diseases, etc..etc..etc.
Search for ‘MSDS propylene glycol’ to get a good idea of what’s currently known about it. It seems to be fairly toxic but only when ingested. Inhalation isn’t necessarily good, but the toxic limit is on the order of kilograms, not milligrams.
Besides, it is a lot better than anything comparable (ethylene glycol, methanol)
Regardless of whether there’s a proven link or not, it still seems like good policy to do something that would eliminate any exposure. Besides, the other benefits are so great that this can only be positive.
The main question is how durable and long-lasting the surface is.
Good point.. But depending on the ease of application this might be something that airlines just reapply to the surfaces in question every summer or so..
I’m a deicer at DIA. We love our masochistic work which is carried out in terrible conditions to very – very exacting standards. Only under exceptional circumstances would the glycol mix enter a cabin. if it did, passengers would have to disembark and we would be terminated. We are watched by FAA, airline officers, pilots and crew and our own safety officers. This is a job that allows zero tolerance for mistakes, involves passing exams each year and on the job training. You are in good enthusiastic hands when on the deice pads.
it’s the residue that comes into the cabin when engines are started, NOT when you’re out there spraying the fuselage/wings. We all know the pancake syrup smell that results when YOU spray. I’m talking about a light haze in the CABIN, coming from the air vents. Engines are NOT running when you spray.
There is a fourth way to deice while in flight. It is used typically in smaller non turbine aircraft, and involves a gel being seeped out from the leading edge. I have flown a Mooney that had this system. There were little tanks in the wings that store the fluid.
I dont know if it is used much if at all any longer though. Probably due to environmental concerns since there is no way that stuff was good for anyone.
Yes, this system is still used extensively under the name TKS. It’s main problems are
1) You must turn the system on BEFORE ice begins to accululate. How do you know you’re in an icing situation until you start accumulating ice? If you turn the system on when you think there MAY be ice, you’re liable to be out of fluid when you really need it. (Some systems have a de-ice setting that may break loose existing ice.)
2) It’s used mainly in light planes (such as Mooneys), which already are sensitive to extra weight. 5 gallons of TKS fluid weighs quite a bit.
3) The fluid may not be available at an airport along your route. If you used up what you had and can’t refill, you’re grounded until icing is no longer forecast.
All that being said, I’d much rather have TKS than nothing! It would give me some options if I flew into light-to-moderate icing conditions.