Today's Message Index:
----------------------
1. 05:06 AM - Re: latching relays (markcs)
2. 05:06 AM - Re: latching relays (user9253)
3. 06:43 AM - Re: latching relays (Robert L. Nuckolls, III)
4. 06:43 AM - Re: Avionics installation tools and supplies (Robert L. Nuckolls, III)
5. 09:45 AM - latching relays (Fred Klein)
6. 03:34 PM - Re: latching relays (Robert L. Nuckolls, III)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: latching relays |
Fred,
I know you asked Bob for his opinion on self latching relays, but thought I would
through my two penneth in.
Self latching relays operate in a number of different ways including the use of
permanent magnets and cam mechanisms to achieve the latching. I suppose that
there are two main perceived advantages of these devices for an aircraft:
1. Once latched they do not require power to hold them open (but with your Sube
you have a fairly meaty alternator so that should not be an issue for you, especially
if you install an essential bus that does not require a made contactor
to provide power to your ignition system).
2. Once latched they are closed unless they are positively unlatched and so
any failure in the wiring etc will not cause them to unlatch, but see comment
above ref the use of an essential bus.
Contactors are very simple devices and have proved extremely reliable in practice.
One of the principle benefits of a simple battery contactor is its function
as your last port of call isolation device for your main electrical systems.
If you have a fault either with a stuck starter on the the ground or perhaps
an electrical fault in the air that causes smoke in the cockpit your ultimate
get out of jail card is to switch off the battery contactor, and in flight with
an electrically dependent engine operate the essential bus depending on your
electrical architecture. If the wiring fails to a latching relay at the same
time as your fault you cannot release it but if the wiring fails to a battery
contactor it will release under its own steam.
If I am sailing a boat, the issue is somewhat different. With a major fault and
unable to release the latching relay I can normally gain access to the battery
and release the positive terminal or if that isn't possible most boats I have
sailed have battery isolation switches for all battery banks which would isolate
the fault - both scenarios are not possible in an aircraft. So your fault
isolation logic would seem to me to need to be different
Just food for thought.
Mark
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=333524#333524
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: latching relays |
A designer needs to ask, "if this part fails, how will I deal with it?" If a latching
relay fails to open when commanded to, how will the electrical power be
shut off? In case of a fire or imminent forced landing, the power needs to
be shut off immediately.
What is safer, a master contactor that fails open or one that fails closed? The
engine will keep running with a failed contactor. And the essential bus will
keep powering critical equipment. Your marine friend might not realize that
an airplane can keep flying with the master contactor off. Simpler is better.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=333525#333525
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: latching relays |
>
>What do you have to say about "latching relays" functioning as battery
>contactors?
A couple of List members have accurately captured the thought
processes unique to aircraft systems design. The
well considered failure modes effects analysis speaks
to Plan-B . . . mitigating the effects of any
particular failure. It also seeks to identify whether or
not the failure is passive (fail safe) or active (oh @#$@#!
how do I turn this thing off!).
I've considered the latching contactor often since
it was introduced to us on the List a few weeks back.
I've not yet discovered the right words and reasoning
one might apply to say, a design review at Hawker-Beechcraft
suggesting incorporation of the device onto one of their
airplanes.
Bob . . .
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Avionics installation tools and supplies |
At 11:29 PM 3/10/2011, you wrote:
>I hope this is allowed here -
Absolutely. Thanks for the heads-up. Are
you flying now?
Bob . . .
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
Mark, Joe, Bob,
Your wisdom is very much appreciated...thank you...I have much to learn.
Though I've been active on the matronics Europa-list, I've just joined
here and look forward to a time when I might have some wisdom to share
as well...til then, I fear I'll just be askin questions.
Fred
do not archive
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: latching relays |
At 12:39 PM 3/11/2011, you wrote:
>
>Mark, Joe, Bob,
>
>Your wisdom is very much appreciated...thank you...I have much to learn.
>
>Though I've been active on the matronics Europa-list, I've just joined
>here and look forward to a time when I might have some wisdom to share
>as well...til then, I fear I'll just be askin questions.
Good . . . 'cause for sure, we can't build your
airplane for you. Here is where you'll find lots
of recipes for success and some help on sorting through
the options. What ever you decide to do will perform
as advertised. Questions are the place to start . . .
Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|