Avionics News November 2012 - 22

MODERNIZING ELECTRICALS
Continued from page 21

with its own switch integral to the box. The alternator churns out the power demanded by the rest of the system to power radios and recharge the battery. A voltage-control unit or regulator applies varying amounts of power to the alternator to meter its output to match system demand – from a high level after engine start (to recharge the battery used to start the engine) down to a trickle matching the demand of other components once the battery reaches full charge. The shop owner was correct. The first work should concentrate on updating the entire electrical system on the old plane in question. But, before starting work, it’s worth working with the customer to outline the system as he or she ultimately envisions it. That’s a large percentage of the defining-and-planning work a customer can outline for himself/herself in the comfort of home and, in the process, define the system needed.

When the charging system can’t keep up with the loads imposed on it, some of the deficit is made up by the battery. This can be an issue at night when running all the lights and radios.
position-reference boxes that work with the transponder for ADS-B Out service. Have the customer list all those load ratings and total them. Now, you have the minimum acceptable level of alternator output needed for the system the owner desires. Of course, more would be better as a cushion and for growth, in the event the aircraft will get more gear later.

THE CUSTOMER’S CHECKLIST
The electrical system makeover has a few givens: a generating source, a storage source (the battery), breakers to protect individual components and switches to power them. Components are the place to start. Many will have a fixed location, and some will have their own integral switches. Help the owner/pilot define where, how many and what type of lights (strobes, position lights, beacons, landing and taxi lights) the pilot desires. Providing the customer with a large diagram – a line drawing of the airplane – can help. They can place icons designating the gear location and indicating its rated current need at all the appropriate places: a red running light drawing X amps, left wingtip; a green one, same amperage, right wingtip; a white running light in the tail – also the same amperage. Finally, landing and taxi lights – and rotating beacons. Every item’s power draw must be listed, from the landing gear motor to strobes, running lights to radios, and any out-of-sight sensors. On a panel diagram, the pilot can draw in the equipment planned: primary flight display and multifunction displays, GPS, comm and nav radios, transponders (and ADS-B type) as well as any components used but not seen, such as remotely mounted attitude and air-data sensors, autopilot servos and any encoders or
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WHAT IF IT’S EXCESSIVE?
When the charging system can’t keep up with the loads imposed on it, some of the deficit is made up by the battery. This can be an issue at night when running all the lights and radios. But, if it’s an issue in the planning phase, it can be resolved before the execution phase. Consider, for example, directing the owner toward new, approved light emitting diode-technology lighting, or LEDs. With an alternative LED solution available for virtually every lighting need planned, the customer can start planning on any difference in cost well before the time to install. Recognition lights, anti-collision, beacons, landing and taxi lights – all of them are available in LED alternatives that draw far less current than the units they replace, sometimes by as much as 70 percent. The LED alternative means the owner can install lights that might total 35 amps of current draw using old technology, and actually only need 15 to 20 to power the LEDs. Once you are set on a total load – lights, radios, display screens, datalink receivers and the like – you can help the customer match the need with an alternator; hopefully, one with a bit of output to spare beyond the listed demand. The client also can begin to look where to mount

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2012

Avionics News November 2012

Table of Contents for the Digital Edition of Avionics News November 2012