Aero-Tips!

A good pilot is always learning -- how many times have you heard this old standard throughout your flying career? There is no truer statement in all of flying (well, with the possible exception of "there are no old, bold pilots.") It's part of what makes aviation so exciting for all of us... just when you think you've seen it all, along comes a scenario you've never imagined.

Aero-News has called upon the expertise of Thomas P. Turner, master CFI and all-around-good-guy, to bring our readers -- and us -- daily tips to improve our skills as aviators, and as representatives of the flying community. Some of them, you may have heard before... but for each of us, there will also be something we might never have considered before, or something that didn't "stick" the way it should have the first time we memorized it for the practical test.

It is our unabashed goal that "Aero-Tips" will help our readers become better, safer pilots -- as well as introducing our ground-bound readers to the concepts and principles that keep those strange aluminum-and-composite contraptions in the air... and allow them to soar magnificently through it.

Look for our daily Aero-Tips segments, coming each day to you through the Aero-News Network. Suggestions for future Aero-Tips are always welcome, as are additions or discussion of each day's tips. Remember... when it comes to being better pilots, we're all in this together.

Aero-Tips 05.27.06

A reader writes:

I was told it is not good to run an aircraft like I did yesterday: 0.8 hours up and 0.9 hours back. My factory Service Center lead mechanic told that I need to put 1.0 or more each time I start it. What are your thoughts?

I replied:

That's not an issue. As long as the oil gets to "green arc" temperature, to boil out trapped moisture, you're copasetic.

Moisture condenses inside engines when they sit on the ground. Especially in moist climates, the longer the engine sits without running, the more moisture may form inside it.

More importantly, water is highly acidic and corrosive. If oil drains off internal parts of the engine (during extended ground time), leaving bare metal exposed to acidic, wet air, the inside of the engine will begin to pit and rust. Long periods without running correlate very closely with engines that need premature cylinder, lifter and valve replacement.

NOTE: That's why most engine manufacturers recommend moisture-displacing desiccant plugs or bags be placed in an engine that won't be run for more than a couple weeks.

Oil Temperature

Cockpit-indicated oil temperature is not the hottest oil gets in the system—it's merely taken at a point convenient in engine design. Oil in pats of the engine can be at water-boiling temperatures when the temperature indicates near the bottom of the green arc, which is typically around 38 C or 75 F—well below the 100 C/212 F boiling point. Once oil is hot enough to boil off water, the engine is getting rid of acids that would otherwise destroy it from the inside out.

Oil generally won't get hot enough to boil away all the water merely running on the ground. Take the plane around the pattern only once, however, and you'll likely have eliminated any water-in-the-oil threat.

Back to the mechanic's advice: I asked the reader to challenge his mechanic to explain how an extra six minutes (from 0.9 hour to a full one hour) would make a difference. Would flying at a reduced power setting to make the trip last a few minutes longer increase engine longevity? If the headwind is a little stronger, making the flight take six minutes longer, will this make the engine more likely to make its Time Before Overhaul (TBO)? We've not heard back yet.

Life Cycles

Maybe the mechanic was more concerned about engine starting cycles, the number of times in its lifetime it is started. Since oil does drain down from parts of the engine during "off" periods (NOTE: modern engine oils adhere much longer to engine parts than earlier blends), metal is exposed to more wear during a start than any other time. Shorter flights mean more cycles over a lifetime, and less likelihood the engine can withstand the wear to TBO. But if that is the consideration, duration of a flight would not be the issue—more important would be how many times the airplane flies.

Aero-tip of the day: You're far more likely to have trouble-free engine life if you fly the airplane at least once a week. Get the oil up to cruise temperature and you'll burn off corrosion-promoting water in the oil. Beyond that and barring the issue of cycles, duration of a flight should not have a direct bearing on engine life.

FMI: Aero-Tips