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 > >
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