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 good pilots, we're all in this
together.
Aero-Tips 02.25.06
Cylinder Head Temperature (CHT) is the most critical engine
indication, as far as longevity is concerned. Oil temperature
control, on the other hand, is vital for both short- and long-term
engine health. The most overlooked component to engine
cylinder and oil temperature management is no
secret—it’s baffling.
Virtually all piston aircraft engines are air-cooled.
Ambient air flow through the cowling is not sufficient to cool the
engine at high power, however, and it cannot target “hot
spots” like the aft side of cylinders or a rear-mounted oil
cooler. To increase and direct air flow aircraft
manufacturers design baffles that form a tight seal around the
bottom and rear of the cylinders. Some installations include
extra baffles in other areas of the compartment. Cooling air
that flows into the cowling is now forced to follow a specific
path, hitting the cylinder “hot spots” and the oil
cooler.
This Installation Sucks
Still, ram-air cooling is not sufficient. The volume of air
must be increased. That’s why you’ll find a gap,
or cutout, in the lower rear of engine compartments. All it
takes is a little “lip” in the rim of the cutout to
deflect slipstream air slightly—creating low air pressure at
the cowling outlet. Many larger engines have cowl flaps in
this area to increase the pressure reduction, and air flow, at low
forward airspeeds. “Escape air” through the
outlet sucks large volumes of cooling air into and through the
engine compartment. An airtight seal created by the baffling
makes air flow where it’s needed.
(Note: a few engines use “updraft cooling,” with
air flow from the bottom up. “Escape air” in
these installations goes out through louvers on the upper cowling
sides—like lots of little cowl flaps).
Aero-tip of the day: Inspect the engine
baffling carefully during walk-around and more thoroughly once a
month or so. Have cracked, broken or missing sections of
engine baffles repaired or replaced without delay.