I remember a discussion many moons ago about the FW magnetic switches. Unless things have changed, they were not considered appropriate for L3 certification (at that time) by a fair number of TAPS unless there was a mechanical switch involved. (Heck, why do both?) The FW mag switch (I have a couple) work well. Many TAPS wouldn't accept it and I suspect the L3CC's didn't like them either. That was several years ago and views might have changed since then. I would not start a project for an L3 certification without getting the mag switches cleared with the TAP/L3CC. If they say "no", it's best to know that right away so one can plan on using mechanical switches at least to get the cert out of the way before they find out they have to change out the electronics bay.
I've flown a single altimeter in a near minimum diameter project with a FW mag switch without problem. Gets 10k' on a J and has a GPS tracker nosecone.
I like the mag switches and I do a startup test with bare contained ematches on an installation to make sure the mag switch defaults to "off" with the battery applied or I turn it off with the magnet if not. When that test is cleared, I disconnect the battery, load the charges and leave the battery disconnected. When I arrive at the field, I connect the battery and make sure the mag switch is "off". Put rocket on pad, swipe with magnet on the outside marked arrows and wait for the altimeter to cycle and give the ready beep. Simple.
Kurt Savegnago
Sometime after that infamous 1,313-post TRF thread regarding Wi-Fi and magnetically-actuated DD altimeter switches was finally locked, the following was announced.
Your SOP is sound, as I interpret it and the 18 October 2020 Tripoli announcement.
Inhibited NOW apparently means the powered-up Wi-Fi or magnetic switch is in the OPEN state (and thus, the DD altimeter is unpowered). The announcement clarified that simply because the remote-control switch is
itself powered (as it MUST be to function), the pyro system is considered inhibited so long as that powered, electronically-actuated switch is in the OPEN state and NOT supplying power to the DD altimeter.
No separate mechanical switch is necessary to achieve the "inhibited" state, thankfully.
But even under Tripoli's original NFPA 1127 interpretation, wireless switching of "unapproved" switches (like the Featherweight magnetic switch) was still allowed by Tripoli in a high-power rocket design. It just demanded that, post-RSO inspection, a separate e-switch power-up/e-match connection area was established safely away from the crowd before power was applied to the electronic switch OR before a pyro-initiating e-match/glow plug/flash bulb (or the like) was electrically connected to the pyro terminals.
BTW, the Featherweight magnetic switch retains whichever state, open or closed, it was in when power was last disconnected from it. Best practice seems to be to magnetically switch it to the OPEN state (altimeter OFF) before its battery is disconnected. That way, it will not spontaneously power up the DD altimeter the next time the battery is connected to the switch.
Good skies,
GlueckAuf