Gear Up: Maintenance of Older Machines

** Here’s our Cheyenne at Aircraft Engineering
in Bartow, Florida, split at the “C” flange
while the hot section is performed.**

Have you ever noticed how old married couples sometimes start to look like each other? Or that ardent dog lovers possess a startling resemblance to their bassett hounds? Crazy as it sounds, I fear that I am beginning to look like my airplane.

The 1980 Cheyenne I that my wife, Cathy, and I own is not necessarily a bad doppelgänger to have at my age, but the parallels are beginning to take on a certain eerie quality. Though I am more than twice as old as the 32-year-old turboprop, we’re at about the same spot in our respective life expectancies. If we use the rule of “dog years,” I’d say the airplane and I are at identical points in the trajectory of our lives. In a sense, we’re both old and not worth much, but still running well and somewhat oblivious to the actuarial facts of life.

We both require a certain amount of maintenance. For me, the issues have revolved around an old eye injury (a risk for glaucoma), another ophthalmologic thing called “vitreous detachment” (sounds vaguely risqué to me) and more frequent visits to the gym. For the airplane this year, it has boiled down to a “hot section.”

A hot section involves inspection and replacement or repair of the bits that are exposed to the highest temperatures in the PT6 engines that adorn the Cheyenne. The compressor turbine disc, compressor turbine blades (pricey as we will see), shroud housing and combustion liner, among other parts, comprise the hot section inspection.

There was great discussion with Bill Turley and Mike Naab of Aircraft Engineering in Bartow, Florida, about “what to do with the engines.” Since ours are closing in on TBO, we had some serious decisions to make. As our hull value has decreased in this down market, engine overhauls have become problematic. How can I possibly explain to Cathy that we need to invest at least $150,000 per engine when the airplane itself isn’t worth that kind of money? Then there are the horror stories of engines taken apart for overhaul and “additional items are identified,” making the cost even higher. With the parts scattered on the shop floor, it is hard to turn back, much like when the plumber has taken apart the toilet and tells you the price has just gone up.

We all agreed, however, that a hot section inspection was a reasonable intermediate thing to do on the left engine. The right engine had enjoyed a hot section a few years ago. It was during this time that I learned about the expensive little things inside those engines. Bill joked that I should make a necklace out of the turbine blades, as they were as valuable as diamonds.

Bill Ahern at Southeast Turbines came to Bartow, where the left engine was “split” at the “C” flange. A special hoist held the front part of the engine and the propeller in midair while the hot section was inspected. Soon came the word: The guide vanes had burned through (see photo), and that fact mandated all new turbine blades. These little babies roll out of the factory at $265 apiece. Good thing there are only 58 of them.

By the time the vane ring ($7,900 — the price of a fine used motor boat) and an “I.E” duct, whatever that is, ($3,714 — the price of a week’s high-end small boat luxury cruise) were totaled up with everything else, the parts were $37,531. Oh, and if I wanted those parts installed, the labor was an additional $8,370.

On time and on budget, the airplane was returned to service, and we took off from Tampa, Florida, for Delaware on our first flight. The left engine started just like it used to, hotter than the right one. At altitude, the left engine burned a little hotter than the right one — just like it used to. It also burned slightly more fuel. I did not conclude from these measurements that I had erred in getting a hot section. I chose a different take-home message: I came away with renewed and profound respect for the turbine engine and the PT6 in particular. It is said that, if you can start them, they will not fail. This is a little disingenuous because PT6s can provide excitement (very infrequently), but it is rarely the engine itself that fails. Rather some item bolted to the engine, like a fuel control unit or starter generator, causes the trouble.

When it comes to the maintenance of my own personal machinery, I’ve wrestled with screening tests and preventive medicines. I have been reluctant to start taking statins (like Lipitor) because I think they are most useful in people with high risk for heart attack and stroke (smokers, hypertensives, etc.). I am very aware of the “this can’t possibly happen to me” syndrome, but the recent, relatively arcane, news that there may be some association between statins and Type II diabetes caught my attention. In an effort to lower my LDLs (low density lipoproteins — the bad cholesterol — just remember L stands for lousy), would I increase the likelihood of diabetes?

The controversy about surveillance for prostate cancer is a topic dear to every man’s heart. A recent study showed no evidence in randomized trials of net benefit of screening. The accompanying editorial pointed to overdiagnosis and overtreatment prompted by elevated PSAs (prostate specific antigens). As one urologist friend of mine said, we may have put more men in diapers than we’ve cured of the disease.

When it comes to the human borescope, though, I am all for it. Colonoscopy has been shown repeatedly and definitively to reduce the chance of death from colon cancer. Much as I enjoy the prep for this test, I reason that it is better than wearing a bag in the future. If you are over 50, get one.

Late in my flying career, I have learned about and flown airplanes even more competent than my own turboprop. My recent experience as a Lear 31A first officer has acquainted me with speeds of Mach 0.81 and altitudes of Flight Level 450. This is about twice as fast and twice as high as a Cheyenne. But the fuel burn is significantly greater in the jet, and the cost of ownership is commensurably higher. It is a magnificent experience to be sitting in the front seat of a machine capable of such wonderment. Don't be misled: If I could afford it, I'd have a jet. Without the resources, though, our airplane is a privileged ride in its own right. I guess one could say that I have had my head turned, but I also know and am comfortable with my roots.

So, it seems that my airplane and I have drifted into a long-term relationship that may be longer than either of us expected. I have come to love the airplane, and, after 13 years of ownership and 1,700 hours in it, I have a sense of what to expect of its power and grace. Soon I will have owned this airplane longer than any other in my life. Now that we've added the Garmin G600 and Avidyne EX500, I can't imagine parting ways. She's good for 240 knots on 400 pounds (60 gallons) of jet-A per hour with a five-hour range. The interior is holding up very well, thanks to the fine work of Duncan Interiors, and the paint is good.

Just like me, we’re both running well. The price of fuel may curtail the amount of flying we do, but I am pretty sure that what flying I do will be in N2458W. I’d like to say that my physical appearance is approximating the airplane’s, but alas, there’s no good way short of plastic surgery to rearrange the lines on my face. In that respect, the dog is prettier than the owner. With a bit of luck, though, the airplane and I can have an immediate future filled with satisfaction, assuming I don’t require a hot section any time soon. Right now, I couldn’t afford it and I definitely don’t want to get split at the “C” flange.

Dick Karl
Dick KarlAuthor
Dick Karl is a cancer surgeon who appreciates the beauty and science involved in both surgery and flying. Dick’s monthly Gear Up celebrates the human side of flying. He writes about his enthusiasm for both the machines and the people who fly and maintain them.

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