NASA's One-Man Stealth Copter

Over the years, there've been plenty of store-it-in-your-garage one-man "personal helicopter" designs (most of which never flew, of course). It's pretty much been sci-fi until now -- and still is -- but this design from NASA's Langley Research Center in Hampton, VA actually looks plausible. Watch the video and decide for yourself.

The Puffin, to be unveiled on January 20 at an American Helicopter Society meeting in San Francisco, is a 3.7-meter-long, 4.1-meter-wingspan craft made of carbon-fiber composites, denting the grass at an empty mass of 135 kilograms, not including 45 kilograms of rechargeable lithium phosphate batteries.

Unfortunately, you won't get far in the Puffin: the endurance (with current battery technology) is less than half an hour. (And of course, the whole thing is just CGI at this point. No prototype has been built, much less flown.) But it looks as if it could actually survive an episode of MythBusters. Which is more than you can say for certain other one-man pocket rockets.

To mentor or not to mentor?

Not long ago I was presented with a unique request: A friend wanted to know if I would act as her mentor if she took up flying. I was flabbergasted.

flab⋅ber⋅gast
  /ˈflæbərˌgæst/ [flab-er-gast]
–verb (used with object)
to overcome with surprise and bewilderment; astound.

Yes, flabbergasted. Because for one thing, until that moment I really had no idea that the person in question was seriously considering flying lessons. It came (as we say) "out of the blue."

For another thing, no one had ever asked me to mentor him or her before, per se. It would be something new. I would have to prepare; brush up on a few things so as not to appear stupider than I already am. Worse, I might actually have to know my stuff.

And for yet another thing, this person lives 640 nautical miles (as the gull flies) from me. Any mentoring would have to be done by phone, e-mail, IM, or telepathy.

Not to kill the suspense, but I told my friend sure, if you sign up for lessons I'll do whatever mentoring you like.

As I write this, she has chosen a flight school and has applied for (and gotten) her Alien Flight Student Program clearance from TSA. Also, I've sent her a copy of Fly the Engine. And despite that, she still wants to fly. ;)

So now comes the hard part, for me: Learning to see everything through the eyes of an ab initio student; coming to grips with "beginner's mind" -- one of the hardest things there is.

Wish me luck.

2000-degree turbocharger?

Well, almost. It seems Mitsubishi has lately been shipping a turbo that can withstand 1050-deg. (C) heat with three times the turbine-blade creep life of Inconel. The alloy being used is MarM, which is cobalt-based rather than nickel-based. For details, see http://www.mhi.co.jp/technology/review/pdf/e453/e453001.pdf.

Do infrequently flown engines rust?

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.

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.

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.