"On-Approach" Logic

[Guest emerydc8]

The "on-approach" logic allows the pilot to speed intervene and stay in VNAV PTH. It also lets the pilot set the missed approach altitude in the MCP as long as it's more than 300' above the actual aircraft altitude. I found some information in a 747-400F manual and have pasted it below. My PMDG program does shift into this logic, but it does not seem to be shifting consistent with the conditions published below. Does anyone know when the PMDG 747-400F shifts into this mode? It seems that every Boeing has a different set of conditions that trigger this event.Thanks in advance.____________ApproachThe FMC transitions to "on approach" under the following conditions:

[Tabs 2,790]

Hi, please sign your real name to your posts, it's a forum rule here that you should have read before posting, thanks.Which of the conditions are you seeing inconsistencies with?

[Guest emerydc8]

Sorry. My PMDG 747-400F seems to be going into "on-approach' logic even if I don't select an instrument approach or a runway. I built my own RNAV/VNAV approach to approximate a 3 degree glide slope and put the last waypoint at 50' above the airport. As I was descending in VNAV PTH I kept selecting speed intervene to see if it would go to VNAV SPD when the speed window opened. It did this initially, but somewhere between the third-to-the-last and the second-to-the-last waypoint on that active route, it went into "on-approach" logic (it would stay in VNAV PTH when I speed intervened)In other cases, where I actually selected an instrument approach from the DEP/ARR page, it would go to on-approach logic well before sequencing the first waypoint of that instrument approach. It seems that there are different conditions for each aircraft--and maybe each company--for the on-approach logic. I was just wondering how the PMDG was set up. Thanks,Jon Del Turco