---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Fri 03/11/11: 6 ---------------------------------------------------------- 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 _____________________________________ Time: 05:06:46 AM PST US Subject: AeroElectric-List: Re: latching relays From: "markcs" 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 _____________________________________ Time: 05:06:49 AM PST US Subject: AeroElectric-List: Re: latching relays From: "user9253" 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 _____________________________________ Time: 06:43:31 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 06:43:31 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 _____________________________________ Time: 09:45:33 AM PST US From: Fred Klein Subject: AeroElectric-List: latching relays 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 _____________________________________ Time: 03:34:05 PM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: 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 ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.