Wow, thanks for all the advice. I intend to follow the "KISS" principle here and only make this as complicated as my L3CC requires. If they'll let me use just a single SPST switch per altimeter, I probably will.
Casey On Wed, Jun 22, 2011 at 11:28 PM, w9ya <[email protected]> wrote: > Hey Casey; > > Personally, I would never trust multiple pole switches for reliability over > a single pole unless the poles were redundant. i.e. wired in parallel. > ...... I repaired high end equipment for many years and this comes from real > world experience with real world (and highly stressed equipment in high > stress) situations. As has been mentioned the removal of power via the > normal power switch is complete in this design. And at a given size the > larger sized contacts of a single pole switch *usually* means higher > reliability. (Opening up some of the standard switches can be quite > illuminating in this regard.) > > The point of flying the required two altimeters is to have a redundant > system. So wiring two separate altimeters and two separate power supplies > via one interlocked switch CAN create a single point of failure. And that's > a bad idea. i.e. I *never* fly multiple pole switches or even multiple > switches for each altimeter system. *** Instead, you fly two power switches, > one for each of the two altimeters you will be flying. > > Curiously I had TWO L3CC's and both were quite in agreement and completely > against the multiple switches per altimeter layouts. And from what I was > told by one of them, his opinion was 'earned' the hard way. Then again I ran > redundant timers instead of altimeters, each with it's own power switch and > lift-off trips, so extra switches made no sense whatsoever. And multiple > pole switches are a bad idea too for all the reasons stated above. Off was > really off and if I had a switch fail to fully "make", I should know during > altimeter/timer verification routines that run immediately after turning the > unit on and this was part of the pre-flight checklist. I had a second unit > running in case one altimeter system/power-switch failed during flight. (The > timers fired 3/4 sec. apart so as not to over-pressurize the chute > container. > > GOOD LUCK on your flight Casey and you picked an OUTSTANDING altimeter to > fly with ! > > - Bob Finch > > > On Wed, Jun 22, 2011 at 10:17 PM, George Shaiffer <[email protected]>wrote: > >> Casey >> Multi-pole slide switches are available and can be simply mechanically >> interlocked to the on posiion. 4 pole dt are not that uncommon. >> still a single point of failure but on a single actuator. >> George Shaiffer >> >> ------------------------------ >> Date: Wed, 22 Jun 2011 21:01:04 -0700 >> From: [email protected] >> To: [email protected]; [email protected] >> CC: [email protected] >> Subject: Re: [altusmetrum] Telemetrum Switch Wiring for NAR Level 3 >> >> >> Thanks for the advice, guys. I'm still in the early stages, just scoping >> a parts list. I believe my planned backup unit (a Raven) also has a common >> rail for its outputs. So in total, I'd need to switch four circuits to >> separately isolate the outputs. >> >> I was thinking about using DPST switches, but after getting burned by a >> switch on my Level 2, I'd rather not run my primary and backup through a >> single point of failure. I could run each altimeter and its own outputs >> through a single DPST, but that almost seems to defeat the purpose of having >> separately-switched outputs. >> >> I'll run all this by my L3CC, once I figure out who that's going to be. >> >> >> Thanks again, >> Casey >> >> On Wed, Jun 22, 2011 at 7:59 PM, Bdale Garbee <[email protected]> wrote: >> >> On Wed, 22 Jun 2011 18:22:11 -0700, Casey Barker <[email protected]> >> wrote: >> > I was hoping I could get away with just the one switch for the >> Telemetrum, >> > plus whatever switch(es) my (heterogeneous) backup needs. Otherwise, I >> can >> > see my avionics bay quickly turning into a bit of a rat's nest. >> >> Keith's advice is spot-on. You need to talk to your L3CC about this. >> They don't all feel the same way, and what one thinks is great another >> may be very uncomfortable with. >> >> I personally used a separate DPST switch to break the common return from >> the igniters on each of the two altimeters in my L3 project to satisfy >> my L3CC's expectations. >> >> I'd be happy to review your proposed design before you build it if you'd >> like. >> >> Bdale >> >> >> >> _______________________________________________ altusmetrum mailing list >> [email protected] >> http://lists.gag.com/mailman/listinfo/altusmetrum >> >> _______________________________________________ >> >> altusmetrum mailing list >> [email protected] >> http://lists.gag.com/mailman/listinfo/altusmetrum >> >> > > _______________________________________________ > altusmetrum mailing list > [email protected] > http://lists.gag.com/mailman/listinfo/altusmetrum > >
_______________________________________________ altusmetrum mailing list [email protected] http://lists.gag.com/mailman/listinfo/altusmetrum
