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 02.05.06
Most airplanes have electrical systems. They need some way to
recharge the airplane’s battery. Depending on a plane’s
vintage and mission requirements, it may have a generator or an
alternator.
Generators
Advantages of generators include:
- Simplicity. Basic generator design dates back to the Industrial
Revolution.
- Output. For a given size, a generator will develop more power
than an alternator.
- Self-excitement capability. It doesn’t take any reserve
of electricity for a generator to, well, generate. You can run a
generator to restore electrical power when the battery is
completely dead.
Disadvantages of generators include:
- Weight. Generators are heavy, not usually a good thing in
aircraft design.
- Movement 1. Generators have many rotating parts that can wear
out quickly.
- Movement 2. Most generators need to spin at 2200 rpm or more to
generate electricity. Battery power is being depleted any time the
engine is run below that speed (such as during taxi).
- Engine power drain. Spinning bulky generators robs power from
airplane engines.
Alternators
Advantages of alternators include:
- Weight. Alternators have light weight for the power output, a
result of (relatively) modern electronics.
- Movement 1. Alternators have far fewer moving parts than
generators, making them more dependable.
- Movement 2. Alternators can develop output at 1200 rpm or so,
charging the battery even when on the ground.
Disadvantages of alternators include:
- Lack of self-excitement capability. Most alternators require a
small reserve of battery power to get them started.
- Power output. For a given weight, alternators are less powerful
than generators.
Mainly because of self-excitement concerns, back-up electrical
systems have historically used a standby generator. Recent
improvements in alternator design, however, have added
self-excitement capability to some models, resulting in
lightweight, capable and dependable back-up power.
Aero-tip of the day: Learn the type, capability
and operating characteristics of the recharging system in the
airplane you’re flying.