Friday, December 14, 2007

Tanis Responds

I heard from Jeff Jorgenson, Marketing Manager for Tanis Aircraft Products, after running the previous blog, and he provided a couple of additional insights. First, he agrees that after shutdown, it's moot whether humidity in the crankcase is really a problem since most parts are covered with oil, which will take a while to drain off.

"The general rule we use," Jeff says, "is that the oil coating probably remains optimal for a week or two. In perfect conditions, it may last a few weeks, but it really depends on how much you’re willing to gamble with your engine. We tell people if you don’t fly at least once a week, then the Engine Dehydrator is something you should consider investing in."

I was expecting Jorgenson to say that parts become vulnerable in a day or two, but a week sounds reasonable. (It turns out Tanis has done ample research in this area. It's hard to make blanket generalizations, because of the many variables involved. In any case, Jorgenson is not just shooting from the hip when he says that in perfect conditions, the oil coating may protect engine parts for "a few weeks.")

Jorgenson also commented on a factor I forgot to mention: salinity. "You also mentioned that Coastal Areas where the humidity is higher might increase the risk of corrosion," he points out. "While this is true, we believe the salty air may have more of an impact in these areas as well, so the need to use a dehydrator between flights is highly recommended. Certainly a week of having salt-water in the engine seems like a long time to us. We can’t really remove the salt, but we can take out most of the humidity. Standing water eventually evaporates into the dryer air so it gets removed over a longer period of time."

It'll be interesting to see how customers fare with the Tanis Engine Dehydrator over time.

Monday, December 10, 2007

Active Dessication the Tanis Way



The Tanis folks have come up with an interesting idea: a small, electric air-recirculation unit that passes crankcase air through dessicant crystals to keep your engine's innards dry (and cut down rust formation on steel parts, presumably). Tanis has found that after a flight, humidity inside the crankcase can be from 85% to 98% (which makes sense, because I'd expect even a small amount of ring blowby to force an enormous amount of water vapor into the case). After hooking the dehydrator unit up, the humidity can be drawn down to around 10%, according to Tanis. (You "hook it up" by attaching one hose to the oil filler neck and the other to the crankcase breather line.)

Interestingly, Tanis claims: "We have taken up to one cup of water out of a hot simulated crankcase without reactivating the desiccant. At that point it would not pull the relative humidity below 27% and the desiccant was pink indicating it was time to reactivate." (The desiccant crystals can be reactivated by heating them for four hours. You can do this right in the unit: Just open a little door and flip a switch. An LCD screen shows humidity and temperature in real time.)

Tanis has a FAQ document that makes interesting reading, and the User's Guide is available online as well.

Sporty's is selling the Tanis Dehydrator for $649.

Is it worth it? Clearly, if it makes your engine last longer, it is worth it. So the real question is, of course, whether it will extend the life of a real engine under real conditions. (And clearly, I don't have the answer to that!) We know that a steel part, put in a humidity closet, will rust quickly. And your crankcase is indeed a humidity closet, of sorts. But your camshaft (and most other steel parts in the engine) is coated with engine oil after a flight. Oil is a pretty good barrier to oxidative attack. Most engine parts also have a thin carbon coat from oil being "cooked down" (but I don't think there's enough of a carbon film on cam lobes or lifter faces to provide any help there).

So the question that lingers in my mind is: How long does it take for enough oil to drain off of, say, an O-320 camshaft to allow oxidation to start accelerating? I don't have the answer to that, although I'm sure this is something that could be adequately simulated in a test lab. I'm not worried about crankcase humidity being 98% after engine shutdown, because in the first minutes after shutdown, parts are pretty well covered in oil. But a day later? That's another matter.

Where does this leave us, then?

I don't have a lot of science to back me up on this one. But I think most people would agree that being based in a coastal area (where it's humid year-round) doesn't do anything good to the inside of an engine between flights. (And it's well-accepted that inactivity is bad for an engine.) So if I were based in a humid part of the world and my plane wasn't stored in a humidity-controlled hangar, I'd be strongly inclined to invest in the Tanis device.

But let's be clear on what a "humid part of the country" is. It's not just coastal areas. At http://ggweather.com/ccd/avgrh.htm, I found a chart of average humidity values (night and day, for each month of the year) for 280 U.S. cities. I ran a quick analysis of the data and found that there are only 5 cities where humidity doesn't exceed 50% at least one month out of the year. Amazingly, 80% of the cities experience an average humidity of 80% (or more) at least one month out of the year. I have to admit this comes as a shock to me.

So unless you live in the desert (and never leave it), you're going to encounter a lot of humidity, at least part of the time.

More reason to consider the Tanis device.

Friday, December 7, 2007

World's Largest Crankshaft



This photo is not fake in any way. It's a 300-ton crankshaft from a Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine, the largest engine of its kind in the world.

Each cylinder of the engine displaces 1820 liters to produce a total engine horsepower of 108,920 hp at 102 rpm. Read all about it here.

Tuesday, December 4, 2007

FADEC for All Continentals

Jim Campbell's interview with incoming Teledyne Continental Motors president Rhett Ross is available now as a podcast. It's 16 minutes long and well worth a listen. Ross is obviously still acclimating to the new assignment, but he handled Campbell's questions with aplomb.

The surprise takeaway for me was when Ross said that TCM's ultimate goal is to be able to offer FADEC (Full Authority Digital Engine Control) for all Continental engines, whether for new aircraft or for the aftermarket.

That would be a historic step in the right direction, wouldn't it?

Sunday, December 2, 2007

Shakeup at ECI

Somehow I missed the news about ECI undergoing a reorg a few weeks ago. Details are here.

The restructuring gives Engine Components, Inc. four business units: a "customer interface business unit"; a repair station (named EC Services); Airmotive Engineering Corporation (new parts engineering); and a fourth unit, Air Cooled Motors, will focus on manufacture of new cylinders, crankcases and crankshafts.

Former president Ed Salmeron resigned
"to pursue a personal opportunity with the State Farm organization."

Not sure what it all means. As I find out more, I'll publish details here.