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.

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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.

FMI: Aero-Tips