Not a production issue but I've seen an altimeter fire charges at power-on, after it was loaded vertically on the rail. IIRC the guy it happened to said it was a water damaged altimeter.
Incidentally though, in that particular case the fiberglass nosecone nearly came back down on the guy's head. IMO this particular situation would have been safer if the rocket had been powered on (edit: temporarily, to test) horizontally first, with the nosecone pointed in a safe direction (or better yet, with charges connected but rocket not assembled). Since that incident I have been test powering on my av-bays in exactly that manner prior to coming to the launch site (i.e. charges connected but rocket entirely unassembled).
I will relate that 14 years ago, I had an altimeter firing on ascent and firing on the pad before two launches. I had just armed the altimeter and was beginning to walk away when the beeping stopped. Thank heavens I knew what that meant and stepped away quickly. I was the only one out there as this was a small launch. The apogee blew and I ran back to put try to put the key in the switch with the nosecone faced away from me. Didn’t make it and the main blew. It was a 4 inch diameter thin walled cardboard Loc tubed rocket that was scratch built.
In both cases above it was a low powered tracking transmitter that dorked the deployment electronics that were kit built available at that time. The kits are no longer made. I didn’t know enough about Rf interference at the time. I had bench tested the altimeters and they responded in a normal fashion BUT I didn’t test them in the presence of a tracking transmitter. That said I believe most modern altimeters are immune to this though I know of one where the maker specifically puts in the instructions not to fly it with an Rf tracker. I have one and fly it in a neat rocket on an H123. It goes to ~1300 feet, doesn’t need a tracker with all the events easily seen. Wows, the non-rocketry laity out there the first time they see a dual deploy. Most certainly, the combined deployment altimeters/trackers were fleshed out and tested by the makers before release and I’ve not heard of a problem with any particular brand.
Other events I heard of is indeed when a defective altimeter, ie. either takes a hard hit or was underwater for awhile, is not tested and blows at the next flight. Some of these stories I read were from some very experienced, respected fliers too. Beware of deployment devices that have taken some hard knocks. I‘d say it’s best to test them a few times on the bench. Doesn’t matter if a mechanical switch is present or not in these situations. Turn it on at the mechanical switch and the charges blow.
Only other issue I’ve read about and are the situations back in the old days (like prior to 2006) where deployment devices would immediately blow the charges if the battery was connected up backwards.
I suspect there are not any of the newer electronics that do that but read the manual of said device from front to cover. If it’s a known characteristic, the maker usually mentions it. Mechanical switch on, charges blow.
As far as Mag switches go. I flew them before the rules came out “locked and loaded”. What I mean is I would have charges connected and connect the battery. With the Featherweight Mag switch I’d then take the magnet to put it into the “off” or I like to call it a standby mode because the switch does draw a tiny bit of current. The Featherweight switch defaults to the “on” mode with the battery connected. I then take it to the RSO table, get it cleared and incidentally there were no issues back then because none had come up yet. Take rocket to pad, swipe the magnet and if all the “beeps” were right, go fly. I have to iterate that since I have the bay open, I have the magnet at the ready in my hand and the second I see that blue LED come on, I swipe it off.
The Eggtimer TRS I did similarly thusly: Connect charges, connect battery, put in standby mode and go to the RSO table. Rocket is totally quiet. Get cleared, did pad setup, activate the TRS from the receiver and go fly.
Again, I did this procedure before any rules were in place and these rockets were 38mm minimum diameter ships where a switch installation would be very hard to do. (Outside of twist and tape!) All my larger rockets have switches as it’s not that hard to install.
I haven’t read the amended rule but I understand with the prior iteration one would get a rocket cleared at the RSO table, proceed to a table in a safe spot just past the RSO table, connect up the battery and initialize the electronics to their safe mode then go fly.
I haven’t flown since the rule change so will have to take a peak at it eventually. If it’s still hard to use Mag switches, I’ll probably retire the two rockets I’ve flown a few times and stick with larger ones.
Let it be known my views on staging are all bets are off. With an electronic device that has a motor igniter on the channel there needs to be a mechanical switch for control. If I was going to do it, I’d also use an altimeter that allowed remote activation by Rf means too. Engage the manual switch, get the heck out of the way, make sure everyone is safe, then activate the staging device to standby for launch mode remotely by Rf.
If one wants to be cautious, do what I do. I’ll start to prep rockets in advance, sometimes a week or so and will put contained ematches (no BP) on the altimeter channels, stand the rocket up and turn on the switch. If the altimeter cycles properly, am reassured the electronics are behaving properly. I will do this before every launch as sometimes I don’t get to fly all that often. This will avoid pad hijinks with the electronics. If Rf tracking is involved and I don’t know if the deployment altimeter is compatible, I’ll set everything up with contained ematches and let the electronics run for up to an hour to see if anything adverse happens. I do know the AIM usb and the Adept 22’s don’t take to Rf well and care must be taken to fly them in the presence of a tracker.
(Obviously, if I know already the tracker/altimeters are compatible, I don’t test them before every flight!)
Kurt Savegnago