---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Mon 01/13/14: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 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 _____________________________________ Time: 06:37:52 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: 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 _____________________________________ Time: 04:49:44 PM PST US Subject: AeroElectric-List: Re: How to Toggle Speed Brakes with Momentary On Switch? From: "Eric M. Jones" 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 _____________________________________ Time: 09:18:55 PM PST US Subject: Re: AeroElectric-List: Re: How to Toggle Speed Brakes with Momentary On Switch? From: Eric Page On Jan 13, 2014, at 5:48 PM, "Eric M. Jones" 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. 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