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).

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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.