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.

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?

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.

Under Attack by the LOP Mafia

The lean-of-peak evangelists are starting to send me e-mail accusing me (essentially) of being a misinformed perpetuator of old wives' tales. I'm grateful for the e-mail, because it reminded me that I hadn't turned on "anonymous comment" capability for this blog. It is now turned on, in case anyone wants to pillory me here, now. (Someone, please try it out to see if it works. Leave a comment!)

I'm not told by the critics exactly what I've said that's an old wives' tale. In an earlier blog, I told how Max Conrad would lean to the point of engine roughness on one mag, then switch back to both mags to get the engine to run smoothly at the leanest possible mixture. That doesn't seem like such a controversial thing.

I do tend to use the term "lean misfire" fairly freely, but I think most people understand what the term means.

I also wrote that I don't like flying behind a rough engine. In other words, I don't pull the mixture knob out until the engine stumbles, then leave the knob there. (Understand, I'm not telling other people what to do; I'm just saying what I won't do.)

But as I say, I'm starting to get rather harsh-sounding mail accusing me (basically) of being ignorant and misinformed on the subject of mixture management, when (as far as I know) I haven't really said anything controversial. Some of these folks seem to be reading meanings into things that aren't there.

In any case, I welcome comments, on this or any subject; leave one below.

Most-Produced Aircraft Engine

Ever wonder which aircraft engine holds the record for being mass-produced in the greatest quantity? It helps to know what the most-produced aircraft are. The airplane at the top of that list (no surprise) is the Cessna 172, with something like forty thousand copies produced. The No. 2 plane, the Polikarpov Po-2, was produced in similar quantity. But the most-produced engine powers neither of those planes.

The tenth-most-produced airplane of all time is the Consolidated B-24 Liberator, with 18,482 manufactured. Each B-24, of course, had four engines. Just counting Liberators, that's almost 75,000 engines.

The most-produced twin-engine plane of all time, the DC-3/C-47, was powered by the same engine that the B-24 was powered by. (Can you guess what it is?) That's another 40,000 engines.

Then you have to factor in all the PBY Catalinas (another 10,000 engines), the Grumman Wildcats, and the 20 or so other aircraft types that flew behind this particular engine series.

Give up? The most-produced aircraft engine of all time is the Pratt and Whitney R-1830, with somewhere near 200,000 copies produced.

Prop Strikes and Crank Failure

The GO-435 crank-breakage incident that I described before may or may not have been related to a prop strike that the plane in question was known to have had (indeed, the Safety Board found it was not), but it makes you think. This is one of those cases where you can't necessarily detect prop strike damage by "dialing out the flange." The engine had prop reduction gearing. On a GO- or GTSIO-series engine, it's unlikely you're ever going to bend the crankshaft by striking something with the propeller.

But crank bending is not the only type of damage that occurs in prop strikes. It's true that in low-rpm incidents, bending is the most likely kind of damage. But in high-rpm/high-power incidents, you have torsional overstress to worry about. (If the crank has counterweights, you also have to worry about counterweight-slamming.) If you've ever been to an engine shop and seen broken cranks from prop-strike engines, you know that the break is seldom at right angles through the crank. More often, the crack opens up at a diagonal angle and the crank almost seems to "unwind" in a helical fashion as the crack propagates. (This makes sense, since most aircraft cranks are manufactured as twisted forgings.) The crack is usually somewhere between the oil slinger and the first conrod throw.

You have to remember that the crankshaft in a Continental or Lycoming engine is nitride-hardened, which makes the surface glass-hard (and glasslike in brittleness). If a prop strike opens up a crank in the nitride layer, it will almost certainly propagate to failure. Maybe not right away, but eventually. Obviously, you can't detect cracks in the nitride layer by dialing the prop flange. A damaged crank can be perfectly straight.

When a prop strike happens, all the attention seems to go to the crank. But again, there are other worries, such as crankcase cracking. A cast-aluminum crankcase is nowhere near as strong as a steel crankshaft, obviously. Yet it's expected to hold the crank in place even as the crank is coming to a sudden stop. Newton's third law applies.

You do remember Newton's third law?

GO-435 Crankshaft Fracture

This photo shows what happened to the crank in a Lycoming GO-435-C2 engine taken from a 1951 Navion that crashed in Burlington, Ontario in 2005. The engine had 2690 total hours and 101 SMOH when the crankshaft broke in flight after takeoff. (Sadly, the pilot stall-spun into the ground.)

Interestingly, even though this engine had undergone a prop strike some 70 hours earlier, the Transportation Safety Board of Canada did not blame the break on the sudden stop. They noted that the gear faces on the planetary reduction gearing showed no evidence of a hard stop. (The fact that the crank broke at the aft end instead of near the front would also be inconsistent, generally speaking, with a prop strike, but the Board didn't mention that fact.)

The Board found that the fatigue failure was progressive and began at a point on the forward fillet radius to the number six connecting rod journal, where some corrosion pitting was evident.

The Board did a detailed examination of the fillet radius and found that "the journal surface showed an absence of case hardening at the origin of the fatigue crack," adding that "The equivalent location on the aft fillet radius and the forward radius 180º from the fatigue crack origin showed acceptable case hardened layers. The number five connecting rod journal also showed the presence of normal case hardened surface layers."

The Board noted: "The deficiency in the material heat treatment condition is believed to have been the result of a manufacturing error."

The crank was manufactured in 1955.

New TCM President to Do Podcast

Back on November 6, I mentioned that Teledyne Continental Motors has named a new president, Rhett C. Ross. I also mentioned that this fellow is virtually invisible on the Web and his background is essentially unknown (to me, anyway).

We should soon know more. I spoke with Jim Campbell of Aero-News Net yesterday and Campbell says Ross has agreed to be interviewed for an Aero-News Net podcast. Stay tuned.

Lycoming Escapes $96 Million Judgment

Last week, a Texas appeals court upheld key portions of a 2005 jury verdict against Lycoming, but set aside a lower court’s order that Lycoming pay $96 million in damages to Interstate Southwest Ltd. of Navasota, Texas. The latter company manufactured what turned out to be defective crankshafts for Lycoming. The cranks in question have failed in flight at least 24 times, leading to the deaths of 12 people.

The lower court found (and last week's ruling upheld the fact) that Lycoming's engineering was at fault, not Interstate's manufacturing process. Moreover, Lycoming was held to have fraudulently concealed information from Interstate. Nevertheless, the "exemplary damages" judgment of $96 million against Lycoming has now been struck down based on deficient evidence. Interstate still gets $10 million in "actual" damages. See http://www.pbn.com/stories/28235.html.

Photo of Lycoming Plant, Circa 1929

I found this great picture of the Williamsport factory (circa 1929) on prime-mover.org. Those are straight-8 L29 engines destined for the Cord automobile. (Hard to imagine one of these engines fitting in a car, but the Cords were great-looking cars.) The Cord automobile was just one of about 150 business undertakings that can be traced to tycoon Errett Lobban "E. L." Cord, who actually bought Lycoming around the time this photo was taken. In 1939, Cord re-organized all of his aviation holdings into the AVCO group (which, in turn, was sold to Textron in the 1980s).

Request

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TCM Gets New President

Did anyone else notice this? Yesterday, Teledyne Continental Motors got a new president. To quote from the press release:

Teledyne Technologies Incorporated (NYSE:TDY) today announced the appointment of Rhett C. Ross as President of Teledyne Continental Motors, Inc., (Piston Engines), effective November 5, 2007. Ross, age 43, succeeds Bryan L. Lewis. Lewis will be retiring on February 1, 2008, after a distinguished 27-year career with Teledyne companies.

Oddly, there is no further information about Ross. This is the only mention of him in the press release. Usually, in this kind of press release, there's a short bio of the new exec, with a glowing description of his track record at the company, etc. In this case, nothing.

Ross is not listed on the Teledyne executive-biographies page. I did a Google search on him and came up with 10 hits, most of them referring to the TCM press release. None of the other hits had anything to say about him.

This seems more than a little queer. Who is this guy, I wonder?

Extra-Large Valves

You think you've seen a lot of valves? Try this one. This is how big the parts are on one of those giant diesel engines that powers an ocean-going vessel (of the oil tanker variety). I'd love to know which is more expensive, a new one of these, or a new exhaust valve for a Lycoming TIO-541.

Extreme Leaning

I'm not a big fan of "extreme leaning," by which I mean continuous operation on the rough side of peak EGT. Leaning an engine until it runs rough due to lean misfire (then leaving it like that) is not something I condone. Call me old-fashioned, but I don't believe in flying behind a rough engine.

But there are times when you need to coax maximum endurance and/or maximum range out of your engine (such as when you are low on fuel), and there's a safe way to do that. It's a technique Max Conrad used on long over-water flights. I forgot to mention it in Fly the Engine and should probably go back and include a mention of it. (Fortunately, kind of quick revision is easy to do when you use Lulu.com as your publisher.) The technique is this:

1. Lean the engine to peak EGT.

2. Switch to one mag.

3. Continue leaning just until you feel the rumble associated with lean misfire.

4. Switch back to both and see if the rumbling stops, which means that the other magneto is providing enough "ignition assist" to cause reliable ignition of the thin air-fuel charge. If the engine is smooth, leave it there and you're done. You've got the engine leaned to where the leanest cylinder will not sustain combustion reliably unless it has both mags contributing to the ignition process.

If switching back to both mags doesn't cure the rumble, start over again and repeat the procedure using the other mag.

This is not something I recommend as an everyday general operating procedure, but it's a good trick to know if you are trying to make the 6966 miles nonstop from Casablanca to El Paso, TX, in an O-360-powered Comanche 180 (as Max Conrad did on November 24, 1959, a record that still stands today).

The iPhone of Engine Monitors

Unfortunately, I can't say much about this one just yet. But I can tell you that before long you're going to see the unveiling of a piece of electronics that is so cool, I can only dub it the iPhone of engine monitors. It's high-tech, it's neat, and it takes engine-monitor capabilities to the next level (in other words, more than just a fancy EGT).

That's all I'm allowed to say for now. Stay tuned for further details.

What Detonation Looks Like

Last time, I showed what preignition looks like, so this time I thought it might be good to take a look at detonation. In this case, we're seeing the result of mild, occasional detonation (such as you would get by overleaning in cruise-climb). The mildness is evident by the fact that only the outer edges of the piston are involved. (Notice the characteristic "sandblasted" look.) The somewhat peened or smoothed-over appearance of the pitted areas, particularly on the left side of the piston (as viewed in this photo), suggest that detonation was encountered only now and then, but over an extended period of engine service. (Over a sufficient period of time, roughness gets "polished out" by the action of lead-containing combustion particulates.)

The positioning of the detonation zones at the far outermost edges of the piston is consistent with operation right at the beginning of detonation onset (in other words, mixture just lean enough to cause incipient detonation, but not lean enough to cause full-on explosive detonation). The mechanism for this is not hard to understand: The abnormal combustion process associated with detonation occurs when unburned fuel and air (far away from the flame front) are heated and compressed past the point of "thermal cracking." There's a short period of time when the fuel molecules actually begin to decompose (split into radicals) on their own, unassisted by combustion with oxygen. Unfortunately, they all tend to do this at once. The radicals so produced then instantly grab onto the nearest oxygen molecules. Instead of steady, slow conflagration, you get an instant bang.

In normal combustion, you don't see fuel molecules crack apart en masse into radicals (detonation precursors) prior to oxidation. Instead, "cracking" happens only inside a very thin flame front. The flame front progresses steadily across the charge volume, creating radicals (in that thin flame zone) as it goes.

So in the engine from which the above piston came, you can imagine that normal combustion happened until the flame front got pretty far away from the spark plug(s). Then the remaining compressed fuel and air at the very edges of the piston went ka-bang!

The engine from which the above piston was taken was not an aircraft engine, but I've seen piston edges that look like this in torn-down Lycomings and Continentals countless times. The next time you visit an engine shop that keeps a garbage bin of old pistons, take a look and you'll see what I mean.

What Preignition Looks Like

Preignition doesn't always burn a hole straight through the center of the piston, but sometimes it does, and this is what it looks like. This is what might be called a deposit burn-through (or for want of a better term, an ash-hole). The entire top of the piston is overlaid with crusty deposit buildup. What likely happened here is that a an amalgam of very-high-melting-point calcium (or other) deposits started to accumulate on the very top of the piston, in the center. After a period of high BMEP (perhaps runaway turbo boost), the deposits, heated to 1500 degrees or more, simply caused the aluminum underneath to soften. (Aluminum melts at 1220 degrees Fahrenheit, or 660 Celsius.) This is clearly a melt-hole rather than a detonation failure. In the latter case, there would be sharp cleavage planes under the lip of the hole, on the back side (the "underneath" side), sort of like what you see on the back side of a bullet hole in a glass window. This piston happens to be from a marine racing engine. But the same thing can happen (has happened!) to aircraft engines. Depending on the source of the preignition (spark plug vs. deposits) and the flame pattern in the cylinder, the piston can either melt through the center, or melt at the edges, or both. More often than not, the entire piston overheats and over-expands in the cylinder bore and starts to make rubbing contact with the barrel wall, giving rise to smearing/scoring or vertical streak-marks on the sides of the piston. You can see some of that at 7 o'clock on this piston as viewed here.

Thankfully, this sort of failure is rare in aviation.

Lycoming High-Squish Piston

Somehow I stumbled across a 2004 patent by Lycoming and Toyota containing some ideas I wouldn't have expected to see from Lycoming.

The patent in question, "Cylinder assembly for an aircraft engine" (U.S. Patent No. 6832589), describes an elegant combustion-chamber design in which a domed piston with special cutouts squishes fuel into a small pocket for rapid-swirl combustion. This general notion has been patented to death in the automotive world, of course, and wasn't new in 2004. But somehow Lycoming and Toyota got the USPTO to sign off on it one more time.

In the above diagram (taken from the patent), I've colored the piston to make it easier to see. Note the close proximity of spark plugs to piston. The "squish zone" (C) calls for a piston-to-cylinder-head clearance of just .047 +/- .016 in., or about enough for five hours of deposit buildup in an O-235, but this wouldn't be for an O-235. This is a high-compression-ratio design for ultra-lean operation on low-octane unleaded fuel, and I guess that's the real punchline.

Combustion Chamber Video

Stop what you're doing right now and go see this video taken from inside an operating engine. Except for the exhaust stroke (which the video skips over for some reason), this clip gives a remarkably informative view into the workings of the Otto cycle.

I was surprised by a couple of things. First, the intake valves (this is a 4-valve engine) spin so fast that they continue to rotate long after they've closed. In fact you can see the intake valve nearest the camera still spinning as the exhaust valve opens.

Another thing that caught my attention is the cyclonic flow pattern of the combusting fuel and air. If you look closely, the flames swirl in a counterclockwise fashion as seen by the camera. The coolest portion of burning charge (bright yellow-orange flame) seems always to be on the intake side of the cylinder (no surprise, I suppose).

Combustion is still underway as the exhaust valve opens. (You can see yellow flames still burning.) The rapid pressure drop as the valve opens makes the fire die down quickly.

This particular engine (I don't know what kind of engine it is) seems to have no detectable valve overlap. In fact, the intake valve doesn't even begin to open until the piston is already traveling downward on the intake stroke. This is extremely late valve opening, indicative of a turbocharged engine.

As they say, a picture is worth a thousand words.

CHT Voodoo

Advice about cylinder head temperatures seems to me to be an area rife with voodoo. On page 143 of the new edition of Fly the Engine, I quote from a recent Lycoming service publication (SSP-400, for Piper Mirage owners) that says this about CHT and cylinder life:

No matter what approved power setting is used, cylinder head
temperatures should not exceed 435 degrees F in level flight
cruise. For optimum service life, cruise cylinder head temperatures
should be maintained below 400 degrees. [emphasis added]

This bit of advice can be traced to statements made in the O-290 manual going back 50 years. I've never seen or heard of any substantiating evidence for it. It's hard to imagine Lycoming running engines for the thousands of test-cell hours of testing that would be needed to gather statistically meaningful data to back such a claim up. If they're relying on "data" from engines in the field, how good could that possibly be? (Think about it. How accurate is the average CHT system? How much CHT data could owners be giving Lycoming?) And why 435 degrees F (224 Celsius), in particular? What's magical about that number? And why, also, 400 F? The only thing magical about 400 is that it's a conveniently round number. It's the same as saying you should keep your cylinders below 859.7 degrees Rankine.

I strongly suspect this decades-old advice is based either on no data, or poor data. I intend to look into it further. Meanwhile, if anybody knows the real story on this, please write to me at fly.the.engine@gmail.com. It's time aviation got past the voodoo stage.

Fly the Engine on Amazon

FTE is on sale at Amazon now, not as an in-stock item but as an item that can be ordered through a private seller (namely me).

It turns out Amazon will let you sell items privately (like eBay, sort of) and take "only" a 15% commission for themselves. I can live with that.

But if you're a publisher and you want Amazon to actually stock your books and fulfill orders directly, they keep 55% of every gross order dollar, plus miscellaneous merchant fees (and a month's float on balances due you). That's fair, right?

Let me see . . . 15%, or 55% . . . I wonder which is better . . .

BTW, Rita and I will be happy to give a quantity discount to anybody who buys 5 or more copies of Fly the Engine (for UPS-ground shipment to a single address). The discount won't be 55%, but it'll be worthwhile. Write to us for details: fly.the.engine@gmail.com.

Cirrus Jet Fat-Wing Design Revisited

Yesterday I heard from Mike Van Staagen, VP of Advanced Development at Cirrus, who saw my AOPA blog of a week or so ago, in which I made light of the Cirrus Jet's short, stumpy wings. He gave me some insight into why the wings are that way. "We're limiting the span to 38.5 feet," he pointed out, "so that the current Cirrus-owner population, which is approaching 4000, can use their existing hangars." This has been a common request, apparently. And it makes good business sense to listen to your customers, so I can see his point there.

He also noted that a thick airfoil cross-section allows for the "lightest possible structure," which I suppose might be true. I don't know. I'm not a structural engineer.

Cirrus is also trying to meet a 61-knot stall speed requirement. This can be approached in different ways, obviously, but starting with a wing that has inherently high induced drag probably doesn't hurt.

Cirrus has prioritized things in such a way as to put aerodynamic efficiency well down the list (which they've admitted all along). Van Staagen notes that even with a short/fat wing, the Cirrus Jet has sufficient power to reach its 25K-foot cruising altitude quickly, certainly quicker than most piston pilots are used to.

But there's a lot of competition in the nano-jet arena (see Philip Greenspun's excellent overview), and not all customers will be basing their decisions on purchase price alone. Some will want a practical long-range cross-country machine that can be justified on the numbers. It remains to be seen whether the Cirrus design will stand up to the competition in a total-ROI sense. Let's face it: if all you want is a snazzy pocket rocket that can get to FL 250 quickly and fly 400 miles before refueling (at a cost well under $1 million), there are any number of L-39s (and other jet trainers) out there right now that can fill the need for $400K. They won't carry 7 people, but the snazz factor is there and you're cruising quite a bit faster than the Cirrus Jet will.

Personally, I think Cirrus is falling into a pattern often repeated in aviation, of designers designing a fine airplane that later needs longer wings. Ted Smith went down this road with the Aero Commander. He did it again with the Aerostar. The original Cessna 421 had short wings; the 421B got longer ones. The Citation I had short wings; they were lengthened in the Citation II. In the Piper PA-28 series, Piper went from a short/fat wing to long/tapered. Peter Garrison eventually lengthened the wings of his Melmoth homebuilt. (The list is a long one if you count military aircraft, airliners, and helicopters that got longer blades.)

I can think of no successful production aircraft that later underwent wingspan reduction.

I'm no aeronautical engineer, but I think history is clear on the fact that adding a bit of wingspan is one of the cheapest ways to increase a plane's utility and efficiency. Payload, range, rate of climb, all increase. Stall speed goes down. Cruise speed, practically unaffected. In a jet, overall fuel economy improves dramatically because you get to high altitude faster.

But if you've got to fit a jet into a piston-aircraft hangar, all bets are off.

I wish Mike and the Cirrus folks well. I can't wait to see their little jet fly. It may be the Grumman Yankee of jets, but you know what? I liked the Yankee.

Shameless Plug

Did I mention that the new 2008 edition of Fly the Engine is 278 pages long and contains 20% new material? Or that it's in stock now and available for immediate purchase? Or that it makes a terrific Christmas gift for your flying friends? Check out this free sample of the book! Order online, it's quick and easy. Go to our order page.

Largest Lycoming

You think you have oil consumption problems? Meet the Lycoming R-7755, a 36-cylinder, 5000-hp, turbosupercharged monster displacing 7,755 cubic inches (bore/stroke 6.375 X 6.75 in.) and weighing a mere three tons, give or take a beer keg.

Two of these babies were built in 1946 (one carbureted, one fuel-injected), for the Convair B-36. Pratt & Whitney won the engine contract, ultimately, with its 28-cylinder R-4360 after the Lycoming proved too unreliable. (Think about that; the R-4360 won on reliability.) Had Lycoming gotten the contract, the B-36 would have gone into the air with 216 cylinders and 432 spark plugs. Imagine trying to keep 432 spark plugs clean, operating on postwar 115/145 avgas.

The R-7755 was innovative in a number of ways. It was liquid-cooled, which is why the cylinders line up in a perfect line (in 9 rows of 4). Each bank of cylinders had an overhead camshaft. (I don't know of another radial with an overhead cam, do you?) Each cam, in turn, had two sets of lobes: one for high power, the other for long-distance economy cruise. When the pilot chose a different setting, the entire cam would slide lengthwise a couple inches to engage the other set of lobes.

The Air Force spent 10 years battling engine problems in the B-36, many of them related to poor cylinder cooling, others involving carb ice and carburetor fires. None of which would have been a problem with the Lycoming R-7755.

Fly the Engine on Google

Today I put some ads up on Google to spread the word about Fly the Engine. Try a search on "EGT systems" or "TBO busting" or just "Fly the Engine," and you should see a Google AdWords ad in the right-hand vertical column of ads.

It took about 30 minutes to set up the Google account and specify the ad's wording, choose the keywords (search terms) it should be linked to, and so forth. The ads went live within an hour. Unreal.

Fly the Engine is Back in Print!

This is an exciting day for me. Through the miracle of print-on-demand, Fly the Engine is back in print once again (for the first time since 1995)! I just "published" it today on Lulu.com; haven't actually seen a hard copy of it yet, but I trust Lulu to do a good job. I've seen their books. They look pretty darn good.

It took a good while to update the original manuscript. All in all, I'm surprised how well the material has stood up over time. But I made quite a few changes, additions, corrections, and deletions; and I added a good bit of new material (resulting in an increase in the page count, to the tune of around 45 pages). This is a true page-by-page revision, not a quickie once-over fluff job.

The book is available for purchase now at http://www.lulu.com/content/1291090 (check out the free online sample, too).

AOPA 2007 in Hartford

I managed to make it to Hartford last weekend and took a few photos while cruising the aisles of the AOPA show. The most popular exhibits seemed to be those of Cessna, Cirrus, and Piper. The latter two brought mockups of their single-engine jets. Piper's was the more convincing by far. It's obvious Piper has thought this one through and can pull it off. The Piper jet's thin, high-aspect-ratio wing and long cabin say it all: This baby is meant to go long distances at high altitudes. This is your upgrade path if you're a Mirage owner.


The Cirrus design doesn't seem particularly well-considered. The wing is almost laughably short and fat, for example, which will cut the plane's rate-of-climb needlessly and severely limit its ceiling. The short fuselage, stubby wings, and V tail spell "Dutch roll" to me. All in all, it looks a bit like a one-off proof-of-concept homebuilt rather than something that's supposed to go into production. The short, fat wings tell me all I need to know, frankly.


Cessna will be using a Thielert turbo-diesel in the 172 next year. They didn't bring a 172 to the exhibit hall, but they did bring a copy of the engine.



The particular Thielert model that will be used in the 172 will produce 155 horsepower and (according to the chief engineer on the project; the guy in the blue shirt) will actually weigh a bit more than a Lycoming O-360. The engine displaces something like 121 cubic inches. It gets much of its horsepower from turbocharging and sheer rpm (1.6:1 gear reduction at the prop). In fact, maybe it gets a little too much horsepower that way.

Time (between overhauls) will tell.

Inaugural Blog

Not much to say in this first post except: Here I am. Back from the undead.

And also: Stay tuned for progress reports on the upcoming new edition of my book, Fly the Engine, soon to be back in print. Hopefully in time for Christmas.