This article originally appeared in CESSNA PILOTS ASSOCIATION magazine.
About the Author ...
Mike Busch is editor-in-chief of
AVweb, a member of the technical staff at Cessna Pilots Association, and in a
prior lifetime was a contributing editor for The Aviation Consumer and IFR
Magazine. A 6,000-hour commercial pilot and CFI with airplane, instrument and
multiengine ratings, Mike has been flying for 36 years and an aircraft owner
for 33. For the past 14 of those years, he's owned and flown a Cessna T310R
turbocharged twin, which he maintains himself. In his never-ending quest to
become a true renaissance man of aviation, Mike's on the verge of earning his
A&P mechanic certificate. Mike and his wife Jan reside on the central
coast of California in a semi-rural area where he can't get DSL or cable
TV.
Don't let your engine rust!
Fly frequently. Try not to allow the aircraft to go more than a week or two without flying. Merely running
up the engine on the ramp actually does more harm than good. Turning the prop through by hand doesn't
help, either.You need to get your oil temperature up to 200 F or more to boil off the condensation, and you
can only accomplish that by flying the airplane.
Hangar your aircraft. Whatever it costs, it's worth every penny. Protecting the paint, windows, and
upholstery is just about the least important reason for hangaring an airplane! The real benefit of hangaring is
protection of the airframe and engine against internal corrosion, and protection of fuel bladders, hoses, and
other rubber and plastic parts from deterioration.
Pick your oil carefully. If your airplane sometimes sits unflown for weeks at a time, you might do better
using single-weight oil like Shell 100W or 80W instead. Single-weight oil provides much longer-lasting
corrosion protection than a multigrade oil like 15W-50 or AV-1 because it is molasses-thick at room
temperature. If you operate in cold climates, consider using multigrade in winter and single-weight the rest of
the year.
Keep your engine clean inside.
Keep your induction air filter in good shape. Consider using a Brackett foam filter and replacing it at
least annually.
Check your alternate air door regularly. If it isn't sealing tight or is sucking open, your engine is
breathing dirty unfiltered air.
Install a spin-on full-flow oil filter if your engine is not already so equipped. It will pay for itself very
quickly. An oil screen is simply not enough.
Use spectrographic oil analysis. Take an oil sample at every oil change and send it to the lab. If silicon is
more than 10 ppm, you have a dirt problem.
Never cold-start without a preheat.
How cold is cold? There is no magic temperature. Any start with the engine temperature at or below 32 F
should be considered abusive. Starting at or below 20 F should be a capital crime.
Oil pressure is not the issue! Using multigrade oil in wintertime, lubrication isn't really an issue even at
subzero temperatures. Cold-starts damage your engine because the pistons heat up much faster than the
cylinders do, temporarily reducing piston-to-cylinder clearances to the point where metal-to-metal contact is
unavoidable.
Preheating is easy. Tanis heaters are simply wonderful. In above-zero temperatures, a couple of 100W
shop lights and a blanket can keep engine temperature 40 F above OAT. When away from home, paying for a
night in a heated hangar is worth every penny.
Avoid unnecessary thermal cycles.
Hours don't wear engines out...thermal cycles do! If your engine ran 24-hours-a-day in a test cell at
cruise power, it would probably go 6,000 hours between overhauls. The reason our engines don't last nearly
that long is because we start them up and shut them down and heat them up and cool them down every time we
fly (and sometimes when we don't).
Try not to start your engine unless you intend to fly. Don't taxi your airplane from the hangar to the radio
shop—tow it. Don't stop at the fuel island before taxiing to parking—call for the fuel truck. Whenever you
start your engine, imagine that you just tossed a $20 bill out the storm window.
Get as many hours as you can per thermal cycle. A few long trips are much easier on your engine than a
lot of short hops. Long-range tanks are terrific if they let you cut down on fuel stops. Training flights are the
worst—train in someone else's airplane if you can.
Warm up and cool down gradually.
Don't be in a hurry to take off. Allow plenty of warm-up time between engine start and departure. The
colder the OAT, the more important this is.
Throttle-up very slowly at takeoff. Each takeoff involves going from idle to max power. Do this as
gradually as conditions permit. One excellent technique: (1) taxi into position and hold; (2) throttle-up slowly
to 50% power with brakes locked; (3) check all engine instruments; (4) release the brakes; (5) throttle-up
smoothly from 50% to 100% power while on-the-roll, taking at least 10 seconds to reach full power.
Practice programmed cool-down procedures on every descent. A good rule is to figure out how many
inches of MP you need to lose to transition from cruise to approach or pattern speed, then use your DME,
LORAN, or GPS time-to-station readout to begin a programmed cool-down that many minutes out. Reduce
power no faster than 2" MP every 2 minutes. Use a stopwatch, don't guess.
Use conservative power settings.
If you operate your engine at the high end of the envelope, you are trading performance for longevity.
Your engine will last longer if you use more conservative power settings. This is especially true when it comes
to turbocharged engines.
Cruising at 65% power is an excellent tradeoff. In exchange for the few knots you give up, you gain
significant fuel economy, cooler engine temperatures, longer engine life, and a quieter cabin.
Operate oversquare!
The old saw about never allowing MP to exceed RPM/100 is bunk! Continental authorizes cruise
operation at 1 to 3 inches "oversquare" for most normally-aspirated engines, and allows 9 to 12 inches
"oversquare" for most turbocharged engines. Check the cruise charts in your POH or obtain the Continental
operator's manual for your engine. Operating at minimum RPM and maximum MP (within the allowable
envelope) actually helps your engine last longer.
Cruise at the lowest RPM and highest MP that the book allows for the percentage of power that you
desire. You usually have several possible RPM/MP combinations to choose from at lower altitudes in a
normally-aspirated airplane, and at virtually all altitudes in a turbocharged airplane.
Low RPM operation provides numerous benefits: better cylinder compression, lower frictional losses,
improved propeller efficiency, cooler-running valves, lower EGTs and TITs, and a quieter cabin.
Maintain optimal CHTs (350 -425 F).
High CHTs are bad for your engine. The aluminum alloy used in your cylinder heads begins to lose its
strength as the CHT rises above about 400 F. Excessive CHTs over a long period of time can result in head
cracks or even catastrophic head-to-barrel separations. Even though your CHT redline is 460 F, you should try
to keep your CHTs at or below 400 F for normally-aspirated engines or 425 F for turbocharged engines. Do
this by opening cowl flaps, increasing airspeed, reducing power, and/or enrichening (listed in descending
order of desirability).
Low CHTs aren't great, either. Cooler-than-optimum CHTs (say, in the low 300's F) can result in
increased deposits on spark plugs and exhaust valve stems. The latter will ultimately result in accelerated
exhaust valve guide wear and a premature top overhaul. Try to keep your CHTs at 350 F or more.
Keep baffle seals in tip-top shape.
Flexible baffle seals are crucial to proper engine cooling. If any air is able to leak past the baffle seals
(between the rigid baffles and the cowling), the cylinders can develop serious hot spots. Inspect the baffle
seals at every preflight, and immediately replace any seals that have deteriorated.
Baffle seals must always fold up/forward, never down/backward! Engine cooling requires that there be a
high pressure area above the cylinders and a low pressure are below them. The baffle seals must be oriented so
that this pressure differential presses them tightly against the cowling. Any seals that fold downward or
backward will allow air to bypass the cylinders.
Black rubber baffle seal material is trash. It typically loses its sealing ability in just a few hundred hours.
Always use silicone baffle seal material available from RAM (red) or Victor (blue). It will last to TBO or
beyond.
Fix exhaust leaks immediately.
Exhaust gas is incredibly corrosive. Small exhaust leaks turn into big ones amazingly fast. Exhaust leaks
often occur at the cylinder exhaust ports where the exhaust riser flanges attach. Leaking exhaust quickly
erodes the soft aluminum at the exhaust port, necessitating costly cylinder removal and reconditioning.
Exhaust leaks are easy to spot. They leave telltale red, orange, or yellow stains. Inspect for them every
time you preflight. If you spot a leak (even a tiny one), get it fixed right away.
Lean aggressively (but prudently).
Most pilots operate their engine much too rich. The result is usually trouble: fouled sparkplugs,
accelerated exhaust valve guide wear, and stuck exhaust valves.
Lean as aggressively as the book allows. For Continental engines, lean right to peak EGT at cruise power
settings of 65% or below. At 75% cruise, lean to 50 F rich of peak. For cruise climb, lean to 125 F rich of
peak for best power and extra cooling. Above 75%, operate full-rich—this is normally confined to takeoff or
go-around.
For turbocharged engines, limit TIT to 1600 F (50 below redline). Do this by reducing RPM, reducing
power, and/or enrichening (listed in descending order of desirability).
Lean during all ground operations except for engine start. It is particularly important to lean for taxi and
runup. Since EGT is usually low-offscale at idle power, the best method is to lean for peak RPM at idle. You
should see about a 50 RPM rise as you lean slowly. If you don't, your idle mixture is adjusted too lean—tell
your A&P.
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Don't let your engine rust!
