Peter wrote:
However, AIUI, the STC(s) in question here require the removal of instruments which were previously primary for that parameter(s).
As I mentioned above, you only normally require standby instruments if the SSA quantitative failure probabilities of your new system don’t meet those specified in AC23-1309-1E. So if your numbers are good, you won’t call-up standby instruments and may well want to get rid of existing instruments to minimise the probability of an un-annuciated failure leading to a display of misleading data.
Without seeing the full STC certification data pack for an individual project (the FHA, SSA and fault-tree analysis) you aren’t going to get the answer you’re looking for.
