Airwork: Time to Pull the Plug?

After 33 years, the engine in my 1976
Cessna Cardinal, with almost 450
hours passed TBO and 20 years since
it was overhauled, may have reached
retirement age.
Tom Benenson

Tom, I've got bad news for you," Brian says when I answer the phone.

The phone call isn't a surprise. I've expected the call every time my airplane was in the hands of a mechanic during the last year or so, but it isn't welcome.

The Lycoming IO-360 in my 1976 Cardinal RG was overhauled in 1989. Since that time I've logged 2,440 hours on the engine. Lycoming recommends a TBO (time between overhauls) of 2,000 hours or 12 years, so the engine has performed much better than expected. The TBO is advisory, not mandatory (unless the airplane is used in revenue service under Part 135 or 121), so as long as the engine is performing as it should and the oil analyses and oil filter inspections aren't showing unusual levels of metal, there's no reason not to let the engine soldier on. The oil analyses have been very positive. In fact, the most recent one from Blackstone Labs concluded: "Nice report at 2,429 hours SMOH."

On a recent flight to rendezvous with Jon, a friend I am meeting for lunch at Schenectady (KSCH) Airport in New York, when I do the run-up before takeoff and switch to the left magneto, the engine shakes and runs very roughly. The J.P. Instruments engine analyzer indicates the No. 2 cylinder isn't happy. Back on both it runs smoothly. I lean the mixture even more aggressively and run up the power to attempt to burn off any carbon buildup on a spark plug. It takes awhile, but eventually the engine runs smoothly and the mag drops are even and well within parameters. I assume the problem is carbon buildup and leaning the mixture has fixed the problem. The short flight to Schenectady is uneventful.

Then, after lunch, when I taxi out to fly home, the mag check again raises flags. This time it's the No. 4 cylinder on the JPI that isn't happy. I tell the controller I need to taxi back to the FBO. Jon, who is getting ready to depart, hears my radio call and asks the controller if he can contact me. "Tom, you want me to wait?" he asks.

"Yeah, Jon, maybe you better. I may have to leave the airplane here and, if so, I'll need you to fly me back to Columbia County."

I taxi back to the FBO where Jon is waiting. Before I shut down the engine, I lean it and again do the mag checks. This time the check is again fine. Standing outside the airplane, Jon indicates it sounds fine. After checking it several more times, I decide it's safe to fly home. Again, the flight is uneventful.

When I get back to Columbia County, I turn the airplane over to Brian Gaylord. Before opening the airplane, he is pretty sure the problem is with the plugs. They looked marginal when the airplane was in for a recent previous problem that was solved with a prop governor overhaul/rebuild and a new tachometer. Maybe after 33 years my airplane is starting to show signs of aging.

Then comes the phone call.

Richmor Aviation at Columbia County manages and maintains an impressive fleet of business jets, but when it comes to major concerns with piston-engine airplanes, it calls in experts from its other bases. Brian enlisted the help of Joe Femia, a mechanic based at Schenectady, who, as the owner of a Piper 140, is very familiar with piston engines.

Joe tells me that as soon as he started the airplane, the engine ran roughly. That wasn't what I had experienced. With me, the airplane had started smoothly and it wasn't until I did the mag check after it had been running for at least five or 10 minutes that it ran roughly. Joe also says that, while it was running roughly, he did a mag check and the magnetos were fine. After shutting down the engine he went over the injectors and the plugs, and again everything checked out fine.

Although the engine wasn't exhibiting the typical symptoms of "morning sickness," which is caused by sticking valves, that seemed the most likely source of the problem. Brian and Sal, the chief mechanic, were convinced that, considering the age of the engine, and without knowing what was wrong, it simply wasn't safe to fly the airplane.

Not what I want to hear. After much discussion, Sal agrees to investigate further but with the understanding that even if the shop can determine what is wrong and if the problem can be corrected, he will make a logbook entry advising that the engine be overhauled. "With an engine that has high time, if something happens, we'll be exposed, so it's really for our protection," he admits. "And yours," he adds, in case you decide to sell the airplane.

When I tell Mac McClellan what is going on and describe the situation, he suggests that because of when it occurs, the problem is likely to be an ignition problem and might be caused by an intermittent problem with the mag. I like that idea. A rebuilt or even new mag will be much better on our pocketbook than a new or overhauled engine.

I explain to Joe that the reason I think the mag is the source of the problem is that the only times I have the problem is when I do the mag check after the engine starts normally and when taxiing out to the departure end of the runway. Although I never have the problem at the initial start, Joe insists that the time he ran the engine, the severe shaking occurred as soon as the engine started.

We decide to start it again and see what happens. So Joe and I pull the airplane out of the hangar. I start it. It runs smoothly. After a couple of minutes I do the mag check. It continues to run normally. For the next 10 to 15 minutes or so, I continue to do the mag check, but I'm never able to introduce the problem.

Despite no problem, I still think there might be an intermittent problem with the mag and prevail on Joe to pull the mag and take it apart to be sure.

Brian's curious: "What will you do if Joe finds it is the mag that's causing the problem?"

To me, that seems a no-brainer. "Well, I'll simply have it repaired and keep flying the airplane. All the other indicators are positive, and the oil analyses have continued to be positive and normal. So there's no real reason not to."

Thinking about it, though, I was reminded of what Mike Busch said when I attended one of his Savvy Aviator Seminars. He argued against prematurely sending an engine to the parts bin simply because it had reached its actuarial age. "You don't euthanize a person when he reaches that age. Why euthanize an engine when it reaches TBO?"

Instead, Mike recommends that you monitor the engine's health and overhaul strictly "on condition." There are three valid reasons, he says, to overhaul or replace an engine: first, if there's a bottom-end problem such as cams or bearings that requires splitting the case; second, if there's a top-end problem on a very high-time engine and repairs are deemed uneconomical; and third, "if you've lost faith in the engine."

I was beginning to lose faith in the engine. Late in the afternoon, Brian calls with Joe on the speaker phone. They've found nothing wrong with the mag. Could it be an intermittent sticking valve? But if it is intermittent, it will be hard to determine which one, and if it happens in flight, it could lead to a rapid loss of oil and engine failure.

My wife, Judith, and I sit down to consider our options. The decision tree has a number of branches. How do you sell an airplane that's not airworthy? Can you find someone willing to buy an engine and have it installed before being able to fly the airplane? Even if the current problem can be diagnosed and repaired so the airplane can be flown, the current market is so depressed it's a bad time to have to sell any airplane. And a high-time engine is going to depress the airplane's value even further.

When I speak with Guy Maher, who is considered an expert in the selling and buying of Cardinals, he points out, "In the thrilling days of a few years back, even rough airplanes would bring pretty decent prices, and they'd be linear in value drop from those in nicer shape or better equipped. Now, many of the planes have 'problems' (and so do their owners) and their value drop is steeper from those that have nice P & I [paint and interior], good engine and late radios. …" Then he reminds me: "You have that custom paint job, which means a lot to you but may hurt in resale too."

One option is to sell the airplane. Another is to overhaul the engine, but does that make sense since it was already overhauled once, 20 years ago and with 2,440 hours on the clock? Do we buy an overhauled engine, a new engine or a factory-remanufactured engine? If a new or factory-remanufactured engine, do we go with the Lycoming IO-360 that's served us so well, or do we opt for the more expensive 210 horsepower IO-390 for which Lycoming recently received an STC specifically for the Cardinal RG?

On the other hand, does it even make sense for us to keep the airplane? Fixed costs for insurance, the hangar (which we talk about giving up) and databases are about $8,500 a year. In the previous 12 months, we spent just under another $10,500 for maintenance and fuel. Interestingly, that $19,000 total is more than my annual salary. I'm not an accountant, but even I can tell "that dog won't hunt!"

So, do we take the approximately $30,000 to $40,000 from our savings, savings that are supposed to sustain us for the next 20 years, to buy and install an engine? And after making it airworthy again, do we continue to deplete our nest egg for the intangible advantages of owning our own airplane?

Will the pleasure we get from owning and flying the airplane balance the cost of a new engine with the understanding we won't get back what it costs but with the hope the market will improve so that, when we do have to sell the airplane, it'll bring more than it will now?

Is it time to pull the plug? We have to talk.


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