N6030X(at)DaveMorris.com
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 Posted: Sat Mar 17, 2007 4:29 pm Post subject: Dragging certified aircraft screaming and kicking into the |
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Bob, for those of us who have certified airplanes and want active
notification of low voltage, EI sells a cheap ($285) voice
annunciator that will say "Check Bus Voltage" in a soft female voice
right into your headset if the voltage drops below 13V, without being
hooked to anything but power. (She'll say 16 other things, too, if
hooked up to various instruments' alarm outputs). It certainly
always gets my attention when I chop the power on approach and switch
on the landing light and she reminds me that I'm now sucking some
battery power.
Also there may be some people who think the annual battery condition
test is a complicated process that requires construction of devices
with light bulbs and timers and things. I did it yesterday without
removing the battery from the airplane. You can do it by replacing
whatever crappy ammeter came with your airplane with a Volt-Ammeter
like the one from EI. I simply switched on the master and enough
additional devices to pull about 4.5A of current (which I have
determined in advance is more than sufficient for a daytime VFR cross
country in my plane), and then checked back every 15 minutes to see
how the voltage was holding up. After 90 minutes, I stopped the
test, as the voltage was still holding at 11.81 Volts. That gave me
the warm fuzzy that I could take as long as 90 minutes to find my
destination and still be assured of plenty of voltage to run my COM
radio, transponder. (By the way, I flew today all the way from
Dallas down to the 50's diner at Brenham in that amount of time, so
90 minutes is a very long time!) To make the condition test really
accurate, one could power up a few more devices and find out if the 4
hour current rating is valid while going to lunch or cleaning up the
hangar. (Not sure I would want to fly for more than 4 hours without
a pit stop and with no alternator.)
Since my certified airplane (1960 vintage Mooney) does not have an
E-bus, I have taken the battery load chart, derated it by 20% to be
really conservative, and posted a synopsis of Current versus Time in
a small chart below my volt-ammeter. (Photo:
http://tinyurl.com/38tpwn ) If I suffer a generator failure, I can
switch the meter to Amps, turn off devices I don't need, look up the
time I should have for that current on the chart, and start my
stopwatch. It's not as quick and efficient as an E-bus, but it
should get the job done without causing me to break a sweat, and it
doesn't require an STC or a 337 or any other governmental
bureaucratic safety-inhibiting nonsense. It's doubtful any of the
authors of dark and stormy night stories ever went to the trouble to
create a little chart like that. It takes 10 minutes to do.
I also keep in my flight bag a handheld comm radio with a
rechargeable battery pack and a separate alkaline battery pack.
Zeftronics makes a line of modern voltage regulators to replace the
horrible Delco Remy mechanical gizmo from the 60's with a nice device
that features OV and LV lights as well as Overvoltage protection
using an external relay.
Those are just some of the things I have discovered that hopefully
some of the certified people on this list might find useful.
Dave Morris
www.N6030X.com
At 05:46 PM 3/17/2007, you wrote:
| Quote: | If I owned a certified machine, I would endeavor to
(1) add ACTIVE NOTIFICATION OF LOW VOLTAGE. (2)
install and MAINTAIN an RG battery. (3) Modify
the architecture to turn the avionics bus into an
E-BUS. (4) When an if the stock alternator craps,
I'd get a modern automotive adaptation in place.
These simple changes alone would elevate the spam
can's SYSTEM reliability by a quantum jump. Implementation
of an e-bus/bat-maintenance protocol makes the vast
majority of demonstrated concerns go away. Virtually
every dark-n-stormy night story I've read that concerned
electrical systems would never had been written had
the owner-operators of the subject airplanes availed
themselves of the knowledge and understanding offered
to you here on this List.
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