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 03.25.06
Oil temperature and oil pressure are two of the most vital
indicators of immediate engine health. The analogy to the
body’s temperature and blood pressure is not too far off --
if one or the other is excessively high (or low), trouble may be on
the way.
Engine oil temperature and pressure, however, are even more
closely inter-related that your body’s “operating
indications.” Oil is a fluid that becomes less or more
viscous, or “slick”, as its temperature changes.
Pressure and temperature, then, will vary predictably relative to
one another.
Note: Modern multi-weight and partially
synthetic oils are modified to provide adequate viscosity over a
wide temperature range, creating year-‘round oils and those
that accommodate use from the frigid mountains to the searing
desert in a single flight. The dictum that the two indications work
together still holds.
Inverse Proportionality
In an essentially closed system (like an airplane engine), if
the engine is running when oil is cold, then oil pressure will be
correspondingly high. Conversely, as oil warms the pressure should
drop. Okay, maybe it’s not mathematically inversely
proportional, but the term gets the idea across for our
purposes.
- In the figure Condition 1 shows typical oil temperature and
pressure just after engine start. Oil is still cold (left gauge),
so pressure is expected to be high (right).
- In typical normal running (Condition 2), oil has reached its
running temperature and pressure has dropped to its normal
indication. These should remain steady for most of the flight.
- Condition 3 is one possible abnormal indication. Oil
temperature is rising and pressure has dropped -- for some reason
(oil leak, blocked oil line, etc.) the system isn’t going to
continue cooling and lubricating the engine properly. The important
point is that the two indications together make sense. If you see
high oil temperature with normal oil pressure, or low pressure with
a normal or cool temperature, you have a discrepancy that requires
close monitoring and a landing at the nearest airport with
maintenance available -- but it may well be a gauge error, not a
true oil problem. But if the inverse proportionality of high
temp/low pressure holds true, you need to think about putting it
down at the closest airport regardless of services…and be
ready to land it in a field.
Aero-tip of the day: There’s logic to the
combination of indications relating to a common aircraft system.
Know the logic and you can accurately “gauge” the
health of the system, then make decisions accordingly.