Avionics News July 2015 - 28

MORE POWER TO THE PANEL
Continued from page 27

generally, anyone who works on airplanes will have a
baseline of what the voltage and ripple are and what is too
excessive."
If your test shows it's not developing full power, then
there are a few things you can check. One of the biggest
culprits is the belt drive.
"If it's a belt-driven alternator, proper belt tension and
belt condition are important to ensure maximum power
generation," Quave said. "Along with belt tension, check
the alternator's air flow cooling - baffling, blast air
plumbing, exhaust component and heat shield condition are
also important. Lastly, check the security of the alternator
case bonding to the aircraft's ground plane."
"Next, make sure you have low resistance connections
between the alternator's output, the aircraft bus and battery
terminals," Ingle said. "Be especially attentive to the areas
where you have the connectors crimped to the cable. If one
or more is incorrectly attached, you can build electrical
resistance, which will add to the total voltage drops within
the system."
And don't overlook the battery's condition. "Operating
with a weak battery can shorten the alternator's life," Quave
said. "It will make higher load demands, especially while
operating on the ground where cooling air flow to the
alternator is minimal."
Use caution when doing a load dump
Talking to a few avionics shop representatives, one question
they often receive from pilots who have recently done a
panel upgrade is: How long will their new avionics operate
on battery power alone?
Unfortunately, there isn't an easy answer. There are
factors that go into the equation: battery condition,
connector health and types of avionics you need to use.
"There are a couple of ways to determine the battery's
useful time in that airplane," Ingle said. "You can run the
engine and turn the alternator off, then wait five or 10
minutes, as defined in F 2490-05, then shed all but the
essential avionics and equipment and see how long it takes
to run the battery down. Or you can just turn the battery
master on and do the same process. It may not be quite as
accurate, however."
Quave said that while a load dump procedure is often
used and even called out in some aircraft pilot operating
handbooks, it must be done the right way and with caution.
"If the alternator is making 20 amps and, for whatever
28

AVIONICS NEWS

*

JULY

2015

reason, you switch off all the loads by turning off the
alternator switch - if you do that under full load, you'll
see an electrical kick-back event," Quave said. "All the
alternator's energy has to go somewhere, and the moment
it is switched off, the magnetic field will collapse back on
itself in the rotor and induce a very high voltage surge at the
output.
"That surge can be upwards of 120 volts DC, and while
the alternator's diodes have a high reverse-voltage rating,
that won't protect them from this much energy. It can be
harmful to the aircraft's systems."
Quave explained that if you want to do a load dump or
load check, the proper way is to leave the alternator on and
then, starting with the highest load and progressing to the
lowest, turn off systems in sequence until you have just the
essential avionics and equipment online. This will safely
reduce the amplitude of the voltage spike that the alternator
will have to absorb when you turn it off.
"From the alternator's perspective, the best way to test
the battery's duration is to unload the system and then
gradually return the systems you need to continue flight and
see how long the battery will last under those conditions,"
Quave added.
I need more power, Scotty
Even after all your troubleshooting and checking, the
legacy unit just won't pump out the power you need. So
what's next?
"Now, with the electrical load analysis standards guide,
we are looking at the aircraft's electrical system a lot
closer than we used to," Ingle said. "If you don't know the
total power requirements of an installation, you can run
into problems, especially if there isn't much margin in the
system's total output."
According to FAA Advisory Circular 43.13-1B,
Acceptable Methods, Techniques and Practices for Aircraft
Inspection and Repair, an electrical load analysis is
simple. You just have to check the generator or alternator
out ratings and limitations that are set forth by the unit's
manufacturer against the total electrical loads that can be
imposed on the unit by all the installed equipment.
When the total load can exceed 80 percent of the output
load limits of the unit, the total electrical load must either
be reduced or the capabilities of the installed generating
capacity of the charging system must be increased.
If you've added up all the loads of the equipment your
customer wants and your ELA shows it totals 82 percent of
Continued on page 30



Table of Contents for the Digital Edition of Avionics News July 2015

Point of Communication
AEA Now
The View from Washington
International News and Regulatory Updates
ADS-B Strategy Accelerated
Member Profile
More Power to the Panel
Legacy of Small Town Airports
A Conversation With...
Current Status of ADS-B Deployment in the U.S.
Member Profile
Garmin’s G3X Touch
Artisanal Avionics
The Standy Power Dilemma b
What’s Working?
Business Basics
Aviation Aces
What’s New
Marketplace Classifieds
Avionics News July 2015 - Intro
Avionics News July 2015 - Cover1
Avionics News July 2015 - Cover2
Avionics News July 2015 - 1
Avionics News July 2015 - 2
Avionics News July 2015 - 3
Avionics News July 2015 - Point of Communication
Avionics News July 2015 - 5
Avionics News July 2015 - AEA Now
Avionics News July 2015 - 7
Avionics News July 2015 - 8
Avionics News July 2015 - 9
Avionics News July 2015 - 10
Avionics News July 2015 - 11
Avionics News July 2015 - The View from Washington
Avionics News July 2015 - 13
Avionics News July 2015 - International News and Regulatory Updates
Avionics News July 2015 - 15
Avionics News July 2015 - 16
Avionics News July 2015 - 17
Avionics News July 2015 - ADS-B Strategy Accelerated
Avionics News July 2015 - 19
Avionics News July 2015 - 20
Avionics News July 2015 - 21
Avionics News July 2015 - Member Profile
Avionics News July 2015 - 23
Avionics News July 2015 - 24
Avionics News July 2015 - 25
Avionics News July 2015 - More Power to the Panel
Avionics News July 2015 - 27
Avionics News July 2015 - 28
Avionics News July 2015 - 29
Avionics News July 2015 - 30
Avionics News July 2015 - 31
Avionics News July 2015 - Legacy of Small Town Airports
Avionics News July 2015 - 33
Avionics News July 2015 - 34
Avionics News July 2015 - 35
Avionics News July 2015 - A Conversation With...
Avionics News July 2015 - 37
Avionics News July 2015 - Current Status of ADS-B Deployment in the U.S.
Avionics News July 2015 - 39
Avionics News July 2015 - 40
Avionics News July 2015 - 41
Avionics News July 2015 - 42
Avionics News July 2015 - 43
Avionics News July 2015 - Member Profile
Avionics News July 2015 - 45
Avionics News July 2015 - Garmin’s G3X Touch
Avionics News July 2015 - 47
Avionics News July 2015 - 48
Avionics News July 2015 - 49
Avionics News July 2015 - 50
Avionics News July 2015 - 51
Avionics News July 2015 - Artisanal Avionics
Avionics News July 2015 - 53
Avionics News July 2015 - 54
Avionics News July 2015 - 55
Avionics News July 2015 - The Standy Power Dilemma b
Avionics News July 2015 - 57
Avionics News July 2015 - 58
Avionics News July 2015 - 59
Avionics News July 2015 - What’s Working?
Avionics News July 2015 - 61
Avionics News July 2015 - 62
Avionics News July 2015 - 63
Avionics News July 2015 - Business Basics
Avionics News July 2015 - 65
Avionics News July 2015 - 66
Avionics News July 2015 - 67
Avionics News July 2015 - Aviation Aces
Avionics News July 2015 - 69
Avionics News July 2015 - 70
Avionics News July 2015 - 71
Avionics News July 2015 - 72
Avionics News July 2015 - 73
Avionics News July 2015 - What’s New
Avionics News July 2015 - 75
Avionics News July 2015 - 76
Avionics News July 2015 - 77
Avionics News July 2015 - Marketplace Classifieds
Avionics News July 2015 - 79
Avionics News July 2015 - 80
Avionics News July 2015 - Cover3
Avionics News July 2015 - Cover4
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