Power Failure Questionaire Help

I wanted to start a new thread related to my other thread "Surviving
Flight Recorder Power Failures". Thanks for all your comments.

I plan on asking the SSA to allow me to give a presentation (at the
next convention) on how soaring electronics all bolts together and the
proper wiring techniques. I get a lot of questions on this topic as
there seems to be lots of confusion on the topic. Also when I look
under the "hood" of some sailplanes, I shudder at the cabling jobs that
I witness. And no, contrary to popular belief, ACE hardware does not
have an aviation aisle.

It occurs to me that I want to put together a comparison of how popular
flight recorders handle power failures. Towards that end I have come
up with a few questions to ask the manufacturers. Do you have more to
suggest?

Multiple power sources
1) Can your device support multiple power sources? I.E. multiple
batteries.
2) How do you switch between the different power sources or are the
sources combined? How are they combined (diode, etc)?

Backup Batteries
1) Does your device have a internal or external "backup" battery?
Is it a true battery or another type of device (i.e. large capacitor).
2) How long with the backup power source last?
3) At what main battery voltage does the backup battery engage?
4) Does this battery charge itself from the main battery input?
5) What features are retained or lost when on the backup battery?
a. GPS output (to PDA)?
b. Output to external display?
c. Internal display?
d. Other?

Flight Logs
1) If there is a power outage of short duration, is the flight log
maintained?
2) How long of a gap in time without power is allowed and still
maintain a single log file?

This topic is kind of funny when you think about it. We sailplane
pilots used to pride ourselves on being immune to "power failures" as
opposed to power pilots who would wet their pants at the thought of
losing power. We need nothing but the sun and our brains to keep us
aloft. Now I can think of at least two times in the past year I've
heard sailplane pilots announce over the radio they were terminating
their flights because they had electrical problems and their flight
computers were not functioning properly.

On Fri, 17 Jun 2005 18:44:03 UTC, T o d d P a t t i s t
wrote:

Not directly They recommend an external 22,000 mfd
capacitor.

Are you sure it's not 22,000uF? 22,000mF = 22F is a blinking large
capacitor (not impossible, these days - I've used a 10F one).

cap - less than a second, alternate battery - multiple days.

22F @ 12V is about 2As ... more than 2A seems a bit unlikely for a
logger.

Not trying to pick holes, just interested.

Ian

On Fri, 17 Jun 2005 19:08:42 UTC, wrote:

Now I can think of at least two times in the past year I've
heard sailplane pilots announce over the radio they were terminating
their flights because ... their flight
computers were not functioning properly.

It's happened to me. The slide rule froze up ... I just flewon till it
remelted ...

Ian


--

On Mon, 20 Jun 2005 14:00:20 UTC, T o d d P a t t i s t
wrote:

"Ian Johnston" wrote:

On Fri, 17 Jun 2005 18:44:03 UTC, T o d d P a t t i s t
wrote:

Not directly They recommend an external 22,000 mfd
capacitor.

Are you sure it's not 22,000uF? 22,000mF = 22F is a blinking large
capacitor (not impossible, these days - I've used a 10F one).

Sorry, yes it's micro 10^-6 not milli 10^-3

Mind you, since capacitors in the 10F range are available, not too
expensive, and about the size of an AA battery, it might be worth
using one. Just be careful folks - Very Nasty Things Indeed will
happen if you short one of these suckers. Stick a discharge resistor
across it for a start.

Ian

Ian Johnston wrote:
On Mon, 20 Jun 2005 14:00:20 UTC, T o d d P a t t i s t
wrote:


"Ian Johnston" wrote:


On Fri, 17 Jun 2005 18:44:03 UTC, T o d d P a t t i s t
wrote:


Not directly They recommend an external 22,000 mfd
capacitor.

Are you sure it's not 22,000uF? 22,000mF = 22F is a blinking large
capacitor (not impossible, these days - I've used a 10F one).

Sorry, yes it's micro 10^-6 not milli 10^-3


Mind you, since capacitors in the 10F range are available, not too
expensive, and about the size of an AA battery, it might be worth
using one. Just be careful folks - Very Nasty Things Indeed will
happen if you short one of these suckers. Stick a discharge resistor
across it for a start.

Ian

The 22,000 uF cap recommendation was a very ugly hack recommended by
the manufacturer, trying to respond to the rules change. Doesn't
work very well, since the half second of hold time reported is somewhat
short of the 5 minutes in the rules.

Worse yet, it causes huge surge currents when it's connected to the
battery, which could blow fuses, diodes, or damage switches. Just
adding the cap is a terrible idea. I'd never do that, without additional
circuitry to handle the potential problems. The supercaps would be
a disaster without additional circuitry.

T o d d P a t t i s t wrote:
"Ian Johnston" wrote:



Mind you, since capacitors in the 10F range are available, not too
expensive, and about the size of an AA battery, it might be worth
using one. Just be careful folks - Very Nasty Things Indeed will
happen if you short one of these suckers. Stick a discharge resistor
across it for a start.


You also want to worry about the initial inrush current. My
initial setup seemed to work fine during testing and
installation. On the next day, however, the fuse blew when
I turned it on as the capacitor charged.


No kidding. The capacitor recommendation was an ugly hack recommended
to try to do something about an ill-considered rules change, which
really wasn't an actual rules change. It's been confusing people for
years. Following is from a 2001 posting from the manufacturer:




Hello All,

after successful reinstalling my newsreader, some advice from us as the
manufacurer of the Volkslogger would be useful (yes, I know, we should be
more active, or active at all, at this newsgroup, and from now on we will
....):

The circuit diagram in the VL manual is only a sample. In some cases
(depending on the inner resistance of the Capacitor, if is an array of
goldcaps or a real capacitor), a serial resistor is needed to avoid fuse
blowing (but not too much resistance because of voltage drop). The
Volkslogger itself draws about 120 miliamps at 12 V.

You can also use an array of 10 AAA accumulator cells.

Background:
------------------
When the Volkslogger got approval, the said requirement was not part of the
standard. We tried to build it into our firmware during the time, but we
didn't know which time frame should be used and if it would be approved by
IGC/GFAC and decided to let it as it was.

Until now, no firmware upgrade introduced this requirement, but now that it
is a wishfull ("should") part of the standard, we will think about it over
winter time. But be sure, we have much other things to develop (new
ultralight plane flight information system with color map etc., see our new
homepage www.ulfis.de )

I hope I helped you a little bit...

best regards

--
Georg Garrecht
Garrecht Ingenieurgesellschaft, manufacturer of the Volkslogger
Germany
www.garrecht.com

T o d d P a t t i s t wrote:
David Kinsell wrote:


The capacitor recommendation was an ugly hack recommended
to try to do something about an ill-considered rules change, which
really wasn't an actual rules change.


I agree it's an ugly hack, but a simple one for which I
already had the required components. Plus, it was successful
in solving my problem.

The recommendation in the manual was just to use the monster cap.
That never should have found its way into the manual. Even if
somebody uses a big enough fuse to avoid blowing, caps have a
surge current rating which was no doubt exceeded. Having one
of those things explode in your panel wouldn't be pleasant.


I use a center-off double throw
switch to select battery A or B. The VL is so sensitive to
loss of power that throwing the switch through the center
off position caused a reset half the time. I couldn't
safely check battery voltages or select the new battery
without risking a reset..

A better way of avoiding the problem is just having one battery.
If you have room for two inadequate batteries, then you certainly
could carry one battery big enough to last the whole flight. If
you're not switching, then there's no problem and you don't have
to use all the funny hardware that gets thrown into systems trying
to fix the problem. More importantly, it avoids the need to keep
guessing when the first battery is getting weak, and trying to flip
the switch before the FR resets.

It's sad but somehow amusing that SLA batteries adequate to solve
the problem have been readily available for well over 20 years, but
people seem to keep struggling with it. I fly with a Cambridge 20,
which like most recorders in the field today can't tolerate a power
loss for more than a tiny fraction of a second. But I've never
had a single problem with multiple logs being created. Turn on
the master switch, go fly, and it just works. A 5 A-H battery can
power a normal panel for 6 hours no problem at all. Helps if
you get the voltage right, but that's another discussion . . .


Dave



T o d d P a t t i s t - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)

T o d d P a t t i s t wrote:
David Kinsell wrote:


A better way of avoiding the problem is just having one battery.
If you have room for two inadequate batteries, then you certainly
could carry one battery big enough to last the whole flight.


1) The glider has 3 built in locations for the standard 12v
7-8AH battery. It's not designed to take larger batteries.
They are large enough for 90% of my flights if fully
charged.

Fine. Wire them together and form one larger battery in the
glider. That way you don't have to keep monitoring one battery,
trying to switch before having problems with the FR. And you
avoid the silly solution of a monster electrolytic.

Those caps are cardboard cylinders filled with caustic liquid,
and a pressure vent to hopefully avoid a rupture. Of all the
components used in modern electronics, they have absolutely the
worst reliability of anything. Putting one in a panel, for
no good reason, is not a good idea.



2) I prefer the redundancy of two batteries. I've posted
recently as to why. I know you disagree, but if you'd
camped at a glider field, without easy access to
electricity, as many times as I, you might prefer the dual
solution too.

You're missing the point. If you can carry multiple inadequate
batteries, you can certainly carry one adequate battery. Switching
between multiple batteries in no way extends the life, it just
opens the door to failures based on funny hardware, or letting
the voltage drop too low before switching.




If
you're not switching, then there's no problem and you don't have
to use all the funny hardware that gets thrown into systems trying
to fix the problem.


A switch and a cap is "funny hardware"? It's about as
simple as it gets.

Much simpler to avoid the switching in the first place, and
forget about the cap trying to hold up the system voltage
as you're doing the switch.







More importantly, it avoids the need to keep
guessing when the first battery is getting weak, and trying to flip
the switch before the FR resets.


I've never had an FR reset due to low battery. The first
sign is always the radio.





It's sad but somehow amusing that SLA batteries adequate to solve
the problem have been readily available for well over 20 years, but
people seem to keep struggling with it. I fly with a Cambridge 20,
which like most recorders in the field today can't tolerate a power
loss for more than a tiny fraction of a second. But I've never
had a single problem with multiple logs being created. Turn on
the master switch, go fly, and it just works. A 5 A-H battery can
power a normal panel for 6 hours no problem at all. Helps if
you get the voltage right, but that's another discussion . . .


Dave



T o d d P a t t i s t - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)



T o d d P a t t i s t - "WH" Ventus C
(Remove DONTSPAMME from address to email reply.)