Hi Q
We did this particular dance some time back.
It's a funny old logic system and gets its inputs from flap requests and EDP output pressure. The flap logic in 'Roller' powered aircraft is different to the P&Ws and GEs. The flap logic inputs are as given in the MM. The EDP failure case is always looking at the EDP output pressure and, if that drops below the stipulated cut-in pressure, the ADP will run AND CONTINUE TO RUN until the EDP pressure increases above 1600 psi. (N.B. The 12 - 14 second run parameter is disabled as long as the EDP pressure remains below 1600 psi)
When I was still active in the 400 arena, we checked this area with Boeing, including the apparent anomalies of cut-in pressures on RR as against other power plants. I posted the results here about two years or so ago but the recent Pprune software upheaval may well have consigned the archive to the great 'wheely-bin' of the ether.
I will do a search through my papers to see if I still have the original correspondence and post, if successful.
Rgds