Plane & Pilot
Tuesday, February 22, 2011

Caring For Your Aircraft

Part I: Advice from the top engine shops

We all know about TBO (Time Between Overhauls or Time Before Overhaul), and we put money aside—mentally, if not in fact—for engine work with every flying hour, because major work is inevitable. However, many of us don’t fly long enough and often enough to reach published TBO, so discovering that we need major engine work is a near-universal surprise.

Flying fewer hours doesn’t help: Both Teledyne Continental Motors (TCM, Lycoming ( call for major work after 12 years, regardless of time flown. Many factors can mandate early heavy maintenance, perhaps hundreds of hours short of published TBO.

The best plan is to fly long and often, and follow the manufacturer’s instructions for maintenance. Commercial operators and schools pile on the hours, and since downtime means lost revenue, maintenance is usually a front-row consideration—but the rest of us don’t have the fun of flying 20 or more hours a week. Budgets are tight, and we maintain the mental image of when the engine last came from the shop fresh in our memories. What should we watch for, and when it’s time, where do we send our engines?

When It’s Time
Certainly, if there’s a sudden or noticeable loss of power, if we whack something with our prop, or if there’s an odd noise—these clues can’t be overlooked. But our engine’s normal calls for help approach us slowly, so we tend to mentally adapt by adding a little more oil, allowing more takeoff distance, or climbing a little slower. We may not even notice slight increases in vibration or more-frequently-fouled plugs. When the “normal” CHT or EGT seems to trend cooler (or hotter) over months, well, everything happens for a reason. Are we losing our engine, or did the baffling get a tear in it? As wear and incipient failure creep up on us, our engines are begging for an overhaul. It’s our job to not ignore them.

Understanding your engine, and knowing what signs to look for, is key to safe flight.  
We can avoid surprises by paying attention: Cut open every single oil filter and look inside—that’s the only way we’ll understand what’s “normal” for our engines. Sending our oil out for analysis, too, gives good clues, but only after a baseline is established. Do frequent compression checks, and log the results. Think about it whenever you add oil—the circumstances, the previous flight(s) and conditions. Has anything changed? What? Why?

Where To Do The Work
Our local mechanics keep us in the air, and generally do a decent job of diagnoses, tuning and adjustments, and parts replacement, but most don’t get the constant practice needed, have the specialized staff, or have the equipment necessary for heavy-duty remedial work. Dedicated engine shops are just that: dedicated. They don’t do annual inspections, they don’t adjust your rudder trim, they do engine work. It’s useful to note, for instance, that if a shop isn’t an FAA Repair Station, it doesn’t have a requirement to periodically calibrate all its equipment. So, when it’s time for major work, it’s usually a good idea to take your engine to a major shop.


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