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 02.16.06
For several days we’ve been demystifying operation of an
airplane’s electrical system by comparing it to the flow of
water. Check the last three days' Aero-Tips if you need to catch
up. To stretch the analogy even further, let's talk about
electrical system indicators.
Please note: This visualization is not technically
correct—but it does a superb job of helping pilots comprehend
what's going on with the electrical system to accurately monitor it
and troubleshoot problems. Engineers, mechanics and purists, please
forgive this teaching tool.
There are three common electrical indicators in light
aircraft:
1) Ammeter. Amperage is the
rate of electrical flow. Equate this to gallons per hour in the
water-flow visualization. An ammeter doesn't directly indicate the
rate of electrical flow. Instead, it tells us if the battery
is:
- fully charged, by indicating a neutral position. Think
of it as a pointer attached to the "float" in the "water tank." If
the float is steady at the full line, then the pump (alternator) is
matching the rate of flow. The needle is centered. Life is
good.
- discharging, with a "minus" or "discharge" indication.
The float is dropping, and the pointer moves with it, because the
pump isn't keeping up with flow—the tank's running dry.
- charging, showing a "plus" or "charge" when the float
rises. The tank's overfilling -- meaning the battery may
overheat.
2) Buss voltage gauge Voltage
is analogous to "water pressure." Buss voltage is the "pressure"
available at the distribution point. Normally a "full" battery
alone has either 12 volts or 24 volts. When the alternator "pump"
is "pressurizing" the system, this goes to 14 volts or 28 volts,
respectively.
3) Alternator loadmeter. This measure the
output of the alternator, usually in volts (where it should read 14
or 28, as appropriate), or in percentage of the alternator's
maximum output (e.g., 25%).
Airplanes may have one of more of these indicators.
Aero-tip of the day: It may be helpful to
visualize electricity as the flow of water to better understand its
function. Tomorrow: Time for a quiz!