The Savvy Aviator #29: Fix It Now!

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If something isn't quite right with your aircraft, don't just live with it; fix it now. Deferred maintenance often winds up being more expensive, and sometimes it's downright dangerous.

The Savvy Aviator

Sometimes I just can't fathom what makes aircraft owners do some of the things they do. Particularly amazing to me are some of the mechanical problems that aircraft owners elect to live with rather than fix.

Now I'm just as averse to spending money as the next guy (and probably more than most). In fact, I've made something of a crusade out of saving money on aircraft maintenance, and these days I conduct weekend seminars to teach other aircraft owners how to do the same.

On the other hand, I have always had something close to a zero-tolerance policy about mechanical problems. When something isn't right on my airplane, it drives me nuts until I fix it. Invariably I fix such problems right away, rather than putting them off.

Nearly four decades as an aircraft owner has taught me that it's usually cheaper to fix a problem sooner rather than later ... sometimes a great deal cheaper. Not to mention that continuing to fly with a known mechanical deficiency can sometimes be hazardous to your health.

Fuel Leak

Apparently some aircraft owners don't share my fix-it-now philosophy. Check out this email that I recently received from an aircraft owner:

"Shortly after I bought my airplane last year, I noticed a drip coming from under the aircraft which pooled just to the left of the nosewheel. The drip occurred with the frequency one drip probably every five seconds while the aircraft sat static with the fuel selector on either the left or right tank. Obviously one of the very important shutdown tasks for me was to turn the fuel selector off in order to stop the leak. I never established whether the fuel leaked while the engine is running.

"After not flying for the past month, I went out to my airplane last week. The aircraft was leaking fuel despite the selector being in the off position. There was a big pool of avgas beneath the airplane, and the fuel gauges indicated that I had lost almost all the fuel in my tanks ... at $4.75 a gallon!

"Not understanding why the fuel now leaked regardless of fuel selector setting, I started the aircraft, taxied it around to warm-up the engine and then left it at the maintenance hanger.

"I am being told by the very competent maintenance supervisor that originally it was simply a fuel selector gone bad. However, they are now telling me that given that the aircraft now leaks in any position, it's also a bad engine-driven fuel pump. Usually I'd say let's fix the selector and see if that resolves the problem altogether but I am concerned about the fuel pump going out at some critical time. Please advise."

Here we have an owner who knowingly flew his airplane for a year with a known, significant fuel leak in the engine compartment. He only brought it to the attention of his mechanic when he could no longer stop the leak when the aircraft was parked by turning off the fuel selector. Now he's asking whether it would be OK to fix the fuel selector and continue flying with the fuel leak in the engine compartment unaddressed.

Good grief! I cannot imagine operating my lawnmower with a known fuel leak, much less my airplane. What is this owner thinking?

Exhaust Leak?

While still scratching my head over that one, I heard from the owner of a Cessna 340 that made me start scratching my head again:

"I don't push the engines hard, running at 65% power or lower most of the time. However, despite a published service ceiling of 27,000 feet, the engines really don't perform well over 15,000 feet. I routinely fly over that altitude, but the cylinder-head temperatures get a little high, and the engines burn more oil.

"Sometimes I have trouble with the wastegates functioning properly at altitude, too, and I get some bootstrapping of manifold pressures (needle separation), which is unpleasant at best (because the engines get out of synch), and is dangerous at worst (because the bootstrapping could be due to an exhaust manifold leak). So as a practical matter, I only climb over 21,000 if it is absolutely necessary."

An exhaust leak at the cylinder exhaust port, if caught early, can often be fixed with a cheap gasket. If you let it go, you're probably looking at a costly cylinder rework job, or in extreme cases (as shown here) a whole new cylinder.

It baffles me how this owner can be sufficiently knowledgeable to recognize that his aircraft has a turbocharging problem that prevents it from operating properly at altitude, and even understands that the problem could well be due to an exhaust leak, yet continues to fly the aircraft with that known deficiency.

Doesn't he understand that turbocharged twin Cessnas have a ghastly history of exhaust-related accidents, many of them fatal? Doesn't he know about AD 2000-01-16 that requires repetitive inspection of his exhaust system every 50 hours, and pressure testing at every annual inspection? What is this owner thinking? (For that matter, what is his A&P thinking?)

Starter Adapter Slipping

The beat goes on. Here's a post I saw recently on a popular Internet aviation forum:

"On my departure from Pensacola on Sunday afternoon, I turned the key to start the engine (a TCM IO-520) and I could hear the starter motor, but the prop wouldn't turn. It did actually turn slightly, but then just sat there.

"I have noticed frequently in the past that the prop turns a little and then stops and then a second or two later it continues. Once the prop starts turning, the engine usually fires on the first turn and starts right up.

"On my previous airplane, my A&P told me to turn the prop until I hear the click and it would help to start. So I turned everything off, got out of the plane and turned turn the prop by hand until I heard it click. I turned it again until I heard it click a second time just for good measure. I then got back in the plane and it fired right up like normal.

"When I stopped for fuel at Zephyrhills on the way home, the engine started right up with out having to do the prop trick.

"I figured I would monitor it and if it acted up again to call in my A&P for a surgical procedure, but after thinking about it this morning I thought I would come to the forum here and see what others have to say."

If you try to start a TCM engine and the starter motor turns but the prop doesn't, you can bet that the starter adapter is slipping (top). This indicates that the spring and shaftgear (lower left and right) are worn. If you catch the problem early, it can be repaired for a few hundred dollars by installing an undersize spring. If you let it go, you may wind up buying a new shaftgear for thousands of dollars, or perhaps even a new engine for tens of thousands.

Replies to this owner's post explain that he was suffering from the classic symptoms of a TCM starter adapter that is severely worn and slipping. What bothers me is that the owner's description makes it obvious that he's been aware of this slippage problem for a long time, yet did nothing about it. Even after the slippage got so severe that he nearly found himself stranded in Pensacola, his first thought was to "monitor it" and only bring it to the attention of his A&P "if it acted up again."

This owner's approach was clearly to do nothing about the starter adapter slippage until it becomes so bad that he simply cannot tolerate it any more. This is truly a "penny wise, pound foolish" attitude because every time a TCM starter adapter slips, it "makes metal" inside the engine. If the owner is really lucky, most of that metal will be caught by the oil filter and won't circulate through the engine, contaminate the bearings and plug up the small passages in the hydraulic valve lifters. If he's not so lucky, he could easily find himself buying a $30,000 engine overhaul.

Yet this owner is hardly alone. Countless owners of TCM-powered aircraft have slipping starter adapters, but elect to live with the problem rather than fix it. Not smart.

Fix It Now!

I could go on and on with similar examples, but by now I'm sure you've got the idea. Any time you become aware of something on your aircraft that isn't quite right, the smart thing to do is to bring it to the attention of your mechanic pronto. If the mechanic agrees that the problem is one you can prudently defer fixing until the next scheduled maintenance cycle, fine. But it's often the case that the fix-or-defer decision is a "pay me a little now or pay me a lot later" proposition.

An exhaust leak at an exhaust-riser flange might be solved with a simple gasket if addressed early. If left unaddressed until the cylinder exhaust flange has been severely eroded, the jug will probably have to come off for expensive rework or replacement.

A slipping TCM starter adapter if caught early can usually be fixed for several hundred dollars or so by installing an undersize spring. If allowed to continue slipping until the shaftgear is worn beyond limits, you're looking at thousands of dollars to repair -- or if you get unlucky, a new engine.

A fuel leak caught early can often be fixed by tightening a B-nut or replacing a chafed line. If ignored, it can cause a fire, loss of the aircraft, and perhaps even loss of life.

So don't just scribble the discrepancy on a Post-It note so you can squawk it at the next annual inspection. Fix it now -- or at least discuss it with your mechanic before making a fix-or-defer decision. It's usually the smart and prudent thing to do, and it might just wind up saving you big bucks.

See you next month.


Want to read more from Mike Busch? Check out the rest of his Savvy Aviator columns.