Today's Message Index:
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1. 06:37 AM - Re: Z-12 Essential Bus Questions (Robert L. Nuckolls, III)
2. 04:49 PM - Re: How to Toggle Speed Brakes with Momentary On Switch? (Eric M. Jones)
3. 09:18 PM - Re: Re: How to Toggle Speed Brakes with Momentary On Switch? (Eric Page)
Message 1
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| Subject: | Z-12 Essential Bus Questions |
At 11:39 AM 1/11/2014, you wrote:
Thanks Bob. I read your recent, excellent
article on DO-160 testing. With EAB airplanes,
can we count on all the devices installed having
seen the same testing? Im planning on a bunch
of Garmins experimental avionics offerings and
Im not sure those boxes see the same testing as
their certified hardware. Ive Googled it a few
times but cant find anything. I need to ask
Garmins Team X about it. So thats why Im a
bit shy to risk putting all the avionics through engine start power cycling.
DO-160 isn't something that people shy away from
to be complied with only when mandated by the
customer . . . or the government.
It's design guidance that says, "If you want your
product to perform as advertised in the proposed
application (in this case, airplanes) then expect
to experience the following kinds of stresses.
The prudent designer of electro-whizzies for
any market has an intense interest in KNOWING
the nature source and magnitude of upsetting
stresses to their product . . . putting
an admonition into the operating manual to
"turn off during engine cranking" is a sad
anomaly that grew out of a knee-jerk reaction
to a spate of failures in solid state avionics
about 50 years ago. It went uncorrected for
decades after the lights of understanding came
on.
Garmin, nor anyone else I know, has a dual-path
development philosophy that says, "Do all the
good testing on products for TC aircraft and
we can let the OBAM market slide."
Good point about the every flight usefulness of
at least getting a radio up without bring all
your avionics up so yes, why not add a few
other essentials and provide a path around the battery contactor as well...
Sorry about my pictogram schematics sometimes
requiring more study than a basic schematic. The
power grid is a bad example of the benefits in my
wiring drawings. I have about 10 drawing layers
covering the various systems where the wiring
schematic is laid out in a kind of topology of
the airplane a top down view of the airplane in
cartoon form. It helps me visualize where
components and wires need to be within the
airplane and where connectors might be most
useful. On these drawings are also included the
basic wiring schematic and other key info related
to that system like pin outs for connectors, part
numbers, etc.. The power grid example in my
email was an excerpt from its overall page and
didnt include the ancillary stuff. Working them
up helps me get my novice head around the
problems involved and collect a lot of key related data in one place.
Understand. It's a powerful visualization tool for
assisting in your understanding and planning. But
its a variant on the language common to the
vast majority of practitioners which impedes
the rapid and accurate transfer of functional
understanding to others.
Bob . . .
Message 2
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| Subject: | Re: How to Toggle Speed Brakes with Momentary On Switch? |
Switch Design 101:
Each switch is to be labled describing its function. The condition of the switch
must be apparent from its mechanical position, whether or not power is applied.
Airplanes have no momentary bi-stable switches.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=416870#416870
Message 3
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| Subject: | Re: How to Toggle Speed Brakes with Momentary On |
Switch?
On Jan 13, 2014, at 5:48 PM, "Eric M. Jones" <emjones@charter.net> wrote:
> Switch Design 101:
>
> Each switch is to be labled describing its function. The condition of the switch
must be apparent from its mechanical position, whether or not power is applied.
>
> Airplanes have no momentary bi-stable switches.
>
> Eric M. Jones
The overhead panel of the airplane I fly at work is littered with both momentary
contact and bi-stable latching switchlights. These devices have legends that
are illuminated from behind, and which present a flat black face when not illuminated.
Unless the illumination is on, the position of these switches is not
immediately apparent (even the latching variety, as their "on" state is only
~1/8 inch different than "off" and they don't all stick out the same amount).
For some of them, even legend illumination doesn't necessarily match switch position,
as some aircraft systems activate and deactivate automatically (i.e. fuel
boost pumps).
When the aircraft is running, all switchlights dark is considered normal operation.
Abnormal conditions illuminate switch legends. If the aircraft were powered
down, you would have to examine each switchlight closely to be sure of its
position, at least one of them would be impossible, and several would require
lifting a plastic guard to see clearly.
This type of switchlight is common to every large turbine aircraft with which I'm
familiar.
Eric
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