Modifying RMS plus and RMS std. delays

[UhClem]

This requirement from the 2018 version of NFPA 1122 would seem to permit manufacturer permitted alterations to model rocket motors:
4.19.3 No person shall alter the components of a reloadable model rocket motor or use the contents of a reloadable rocket motor reloading kit for a purpose other than those specified by the manufacturer's instructions for the reloadable rocket motor or reloading kit.

If that were the case, why was nearly identical language in 1127 changed?

Another interesting point is that 1127 still treats reloadable and single use motors differently. There is a flat prohibition on altering single use motors but there is an exception for reloadable motors which was added expressly for the purpose of authorizing delay adjustment. So what does that mean for Aerotech DMS motors? It would appear that adjusting those delays is still prohibited by NFPA 1127.

But 1127 never stopped anyone from adjusting CTI delays.

 

[Steve Shannon]

If that were the case, why was nearly identical language in 1127 changed?

Another interesting point is that 1127 still treats reloadable and single use motors differently. There is a flat prohibition on altering single use motors but there is an exception for reloadable motors which was added expressly for the purpose of authorizing delay adjustment. So what does that mean for Aerotech DMS motors? It would appear that adjusting those delays is still prohibited by NFPA 1127.

But 1127 never stopped anyone from adjusting CTI delays.

I went back and tracked the evolution of this requirement. It’s really interesting. One of the steps in its life was to accommodate user adjustments to delays, but there were some politics that went on as well, with one manufacturer arguing that manufacturer permitted should also be approved by the certification organization and another arguing that nobody knew their motors better than the manufacturer and thus no certification of motor changes is necessary. That passed for one version with the certification language intact with only the one manufacturer voting “No”. Then there was an error. Finally the wording requiring that such changes be approved by the certifying organization was dropped as being redundant. I’m still trying to understand the final meaning.