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gert.v(at)sbcglobal.net
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 Posted: Thu Aug 31, 2006 4:33 am Post subject: Is EFIS vulnerable at engine start? |
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for the record, I am NOT worried about it, but it stands to reason that
many an EIS are build on the same platform as the accompanying EFIS, if
a company recommends to not turn on the EFIS and the EIS is on the same
platform, should it then not follow to have that switched off too?? I
just think it is funny that u want to buy a $$$$ EIS but the mfg
recommends to have it off at a important time.
Yes, i know, u can always add another switch to u stick to switch it on
el-pronto when the engine catches 
Robert L. Nuckolls, III wrote:
| Quote: |
<nuckollsr(at)cox.net>
At 08:10 PM 8/30/2006 -0500, you wrote:
>
>
> begs the question, what about the current crop of electronic engine
> instruments, ya all keep them off till u engine is running.
> What good are they if u can't have them on during engine start
> so u wait till the engine is running, switch u electronic instruments
> on to discover u have no oil pressure, oops....somehow i don't think
> i want Blue Mountain to check my oil pressure if i have to have their
> system off during engine start.
The risks are exceedingly low. I suppose there are
folks who tell tales of having lost an engine when a pump
shaft sheared on startup . . . but think about it. Just
how highly stressed are the oil pump parts? If one is
really worried about a bullet proof oil pressure indication
at startup, perhaps a pressure switch and "OIL P WARN" light
in the annunciator panel is called for.
I wouldn't put engine instrumentation on the e-bus. 99.999% of
the time, engine instruments show the same things they said
the last time you looked at them. Loss of some engine functionality
in addition to loss of alternator on same tank of fuel is exceedingly
remote. Or, one could install an SD-8 for unlimited endurance on
an 8 Amp e-bus and flip the instrumentation on from time to time.
Bob . . .
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gregcampbellusa(at)gmail.
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| Posted: Thu Aug 31, 2006 6:51 am Post subject: Is EFIS vulnerable at engine start? |
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I don't have a Dynon yet - but based on my experience with the Chelton Sport:
I would say "yes" you do want a separate power switch (for each screen),
and "no" you don't want it on during engine start (if the voltage causes it to reboot).
My original design had the EFIS screens fused directly to the E-Bus
as I couldn't see a time when I would ever want to turn them off.
Turning the EFIS screens off is no big deal, but turning the
AHRS off and getting an in-flight restart was a big deal
when I had the Crossbow NAV425.
If I start with just one battery, the EFIS would stay on just fine.
If I cross-connect both batteries for the start, the starter would
spin a little faster, but both EFIS screens would usually reboot.
If the batteries were low - then using both batteries and not having two EFIS
screens drawing a couple of extra amps each would be a nice option.
The Chelton doesn't have an ON/OFF switch on the EFIS, (or I haven't found it
The other place it would be nice is if you're trying to shed some load.
I have two screens, but I can easily get by with one. Turning one off in flight
wasn't an option before. And those screens DO put out the heat.
And finally - if one of the screens acted up & did something weird,
it would be nice to be able to shut it off to avoid the distraction.
So... for all these reasons, I plan on adding a power switch to each
EFIS screen. My current plan is to continue using fuses,
but add a DPDT ON-OFF-ON switch, possibly with a "guard".
With the guard down, it would be in the "normal ON" position and
connected to a fuse in the E-Bus. In the "center OFF" position
the screen would be off. In the "alternate ON" position with the guard up,
it would be connected to a different fuse directly on the main bus.
This gives me the ability to:
1) reboot just one screen
2) turn off one screen (to save power, heat, etc..)
3) take a "second shot" if the first fuse pops, by switching to the "alternate ON"
4) gain back the voltage lost through the diode to the E-Bus (the second fuse goes direclty to Bus1)
IF the battery is ever getting really, really, low - that last 0.4v might make a difference.
The Chelton "small screens" run considerably warmer than the Dynon.
I've been flying with the Chelton's for over a year and my system is still evolving.
One other thing I discovered is that my Grand Rapids EIS "fades out" long before
the other screens stop running in a low voltage situation. It continues to put out
valid engine data to the Chelton, but you won't be able to see it on the EIS.
Consider what you would do if you smelled electrical smoke in the cockpit !?
Reaching over and shutting off the master switch might be overkill, or it could
be your first choice. The airlines teach that once you've made the situation
"survivable" you should usually stop troubleshooting.
Turning off the master switch in-flight needn't leave you clueless,
so my backup instruments include mechanical gages for:
airspeed, altimeter, VSI, compass, and MP. A battery backed Dynon
wouldn't be bad either!
Greg
[quote][b]
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N1DeltaWhiskey(at)comcast
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| Posted: Thu Aug 31, 2006 7:20 am Post subject: Is EFIS vulnerable at engine start? |
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FYI, the Dynon is set to come on when powered (mine is via fuse from the e-bus). If it were necessary to turn it off for starting (not), a simple push of the lower left button for 2 secs. turns it off.
Doug Windhorn
[quote] ---
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trigo(at)mail.telepac.pt
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| Posted: Thu Aug 31, 2006 1:27 pm Post subject: Is EFIS vulnerable at engine start? |
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| Quote: | So... for all these reasons, I plan on adding a power switch to each
EFIS screen. My current plan is to continue using fuses,
but add a DPDT ON-OFF-ON switch, possibly with a "guard".
With the guard down, it would be in the "normal ON" position and
connected to a fuse in the E-Bus. In the "center OFF" position
the screen would be off. In the "alternate ON" position with the guard up, it would be connected to a different fuse directly on the main bus.
This gives me the ability to:
1) reboot just one screen
2) turn off one screen (to save power, heat, etc..)
3) take a "second shot" if the first fuse pops, by switching to the "alternate ON"
4) gain back the voltage lost through the diode to the E-Bus (the second fuse goes direclty to Bus1)
|
Greg
I am planning something similar, but some time ago I realized that when one wants to go from "normal ON" to "alternate ON", or backwards, it is not possible without rebooting the unit, since you will have to pass by the central OFF position of the DPDT switch, which will cut power to unit. How can this be solved?
I looked for a OFF - ON - ON switch but didn't find it. Does it exist?
Carlos
[quote][b]
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nghertner(at)verizon.net
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| Posted: Thu Aug 31, 2006 2:34 pm Post subject: Is EFIS vulnerable at engine start? |
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On 8/30/06 9:10 PM, "gert" <gert.v(at)sbcglobal.net> wrote:
| Quote: |
begs the question, what about the current crop of electronic engine
instruments, ya all keep them off till u engine is running.
What good are they if u can't have them on during engine start
so u wait till the engine is running, switch u electronic instruments on
to discover u have no oil pressure, oops....somehow i don't think i want
Blue Mountain to check my oil pressure if i have to have their system
off during engine start.
A DeMarzo wrote:
> And I think that I would spring for a $10 switch as just a tiny bit
> more protection on my $3000 instrument.
>
> Spikes Happen
>
> Al
> General Aviation - Pricing People Out Daily
>
>
>
> On 08/30/2006 7:56:01 AM, Bill Denton (bdenton(at)bdenton.com
> <mailto:bdenton(at)bdenton.com>) wrote:
>> Dynon disagrees...
>>
>> The following exchange came from
>> Dynon's message board:
>>
>> Question: "I've just installed my D10A and as
>> advised in the instructions wired it through a 2 amp fuse. Since I
>> didn't order the internal battery, I did not connect the "stay
> alive" wire and also did not install a separate power switch. The unit
> comes on when I turn on the master switch without my pressing the unit's
>> power button. I assume this in normal, but can I have problems with
> power
>> spikes during engine start? Should I install a separate power switch in
>> the Dynon circuit? If not, should I turn off the EFIS before engine
>> start?"
>>
>>
>> Answer, from Dynon Support:
>>
>> "The EFIS is indeed
>> designed to come alive when power is applied.
>>
>> Many customers install the EFIS in exactly the same electrical
>> configuration you have set up. The unit will not be damaged by having it
>> on during engine start, but it may reboot if the voltage momentarily
> drops
>> below 10V.
>>
>> Also, since you did not purchase the internal battery, you may want to
>> connect the keep alive wire to power the clock when your master
> switch is
>> off. Otherwise it will reset after every power
> *
>
>
> *
You can hook up a back up battery either for the Blue Mountain alone with a
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diode in the circuit available on their website, or as I am doing use the
back up battery for the emergency bus to power up the efis before start up.
Lory Ghertner
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Dennis Glaeser
Joined: 10 Jan 2006
Posts: 53
Location: Rochester Hills, Michigan
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| Posted: Thu Aug 31, 2006 7:10 pm Post subject: Is EFIS vulnerable at engine start? |
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----------------------------------------------------------------------------
----------------------------
I am planning something similar, but some time ago I realized that when
one wants to go from "normal ON" to "alternate ON", or backwards, it is
not possible without rebooting the unit, since you will have to pass by
the central OFF position of the DPDT switch, which will cut power to
unit. How can this be solved?
I looked for a OFF - ON - ON switch but didn't find it. Does it exist?
Carlos
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---------------------------
The switch you are looking for is the Master Switch that B&C sells (the
S-10 - $19.50).
See:
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?11X358218#s700-2-10
This is a double-pole switch, which may be more than you need, but getting a
single pole version will be a $pecial order item from someplace like Digikey
or Mouser or OnlineComponents and probably take a while to get.
Dennis Glaeser
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Paul LeDoux
Joined: 10 Jan 2006
Posts: 13
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| Posted: Fri Sep 01, 2006 12:13 am Post subject: Is EFIS vulnerable at engine start? |
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you could wire in a pushbutton, normally open, switch, to bypass normal switch, and push it in to keep power on the unit while you operate the "normal on" to "alternate on" switch. If added switch failed then you would be back as before push button switch was added. I would add PB switch adjacent to existing switch.
Paul
[quote][b]
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oldbob(at)BeechOwners.com
Guest
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| Posted: Fri Sep 01, 2006 6:10 am Post subject: Is EFIS vulnerable at engine start? |
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Good Morning All,
Since I am an electrical neophyte, I should stay out
of this discussion, but may I mention that several
airliners I flew in a previous life had two basic
types of switches used for system control.
Most were the familiar snap type which "broke" the
first circuit before "making" the next. Others were
made such that the second circuit was connected before
the first was disconnected. Naturally, the old style
were called "break before make" and the others called
were "make before break".
How they worked mechanically is way beyond me, but it
does seem that a "make before break" style switch
might be s just what you want.
Hopefully, they are available at a cost and weight
that would work!
Happy Skies,
Old Bob
AKA
Bob Siegfried
Stearman N3977A
Downers Grove, IL
LL22
Happy Skies,
Old Bob
--- PSILeD(at)aol.com wrote:
| Quote: | you could wire in a pushbutton, normally open,
switch, to bypass normal
switch, and push it in to keep power on the unit
while you operate the "normal
on" to "alternate on" switch. If added switch failed
then you would be back as
before push button switch was added. I would add PB
switch adjacent to
existing switch.
Paul
|
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gregcampbellusa(at)gmail.
Guest
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| Posted: Sat Sep 02, 2006 6:12 pm Post subject: Is EFIS vulnerable at engine start? |
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I considered a "Make before Break" switch on the
"ON-OFF-Alternate ON" switch, as well as a
momentary switch in parallel with the other switch.
This could work well, but only as long as BOTH the
"ON" and "Alternate ON" sources were ON THE SAME BUS.
The hazard would be if either "source" were on a different bus,
then if you use a small SPST switch to keep the EFIS alive
while you switch from "ON" to "Alternate ON", you face a very likely risk
of running MANY amps through a switch (& fuses) designed for FEW amps.
At a minimum, you'd probably smoke either or both fuses
protecting the EFIS, and then the EFIS would be dead.
A workable alternative would be a momentary OFF-(ON) DPST switch,
where each source is protected by a diode so it could ONLY feed the EFIS,
and would not attempt to serve as a cross-connect between the busses.
By putting the diodes on the momentary switch, you avoid having the diodes
permanently dropping the voltage going to the EFIS. When you're load shedding,
you're probably least likely to want to have "extra" diodes in series with your EFIS.
This starts to get a bit complex. The "pain" of having an EFIS screen reboot
is fairly low. It might take 30 seconds or so. In the meantime, you could
leave the other EFIS screen on and barely miss the first one.
Much more important is keeping the AHRS system up & running.
The new Pinpoint Inertial AHRS supports two power inputs.
But the point is... you can't just casually switch to a "make-before-break" switch
without considering what the sources are. You don't want to try running your
landing light, pitot heat, nav lights, etc.. thru a switch & fuse rated at 5 amps.
Greg
[quote][b]
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