NAV/PROF question

[ahinterl 1]

When I deviate from the NAV route, but are in the vicinity of it (i.e. not hundreds of miles off), are the PROF information and the vdev pointer still valid sources of information, i.e. can I use them for descend guidance even if I'm not on the magenta path?The question arose this weekend when I flew a manual approach to TNCM. During the descend, I decided to deviate from the magenta route and do the rest of the flight by hand. With AP and AT off, I left the lateral path, turned earlier missing some fixes and approached the runway at an angle different to the calculated NAV path. The vdev pointer seemed to be centered most of the time, but I wonder whether I can rely on it in such situations.Andreas

[downscc 1,327]

I think it can be a reference but I wouldn't rely on it as in flying IFR and using it like a glideslope. I like the MD11's ability to descend on a glide path, set three degrees in and down you go. Pretty slick.

[Check_Airman 3]

Unlike the 744 and 767 Vertical deviation indicator, the MD11's isn't accurate enough to use beyond the FAF. At first I thought it was a PMDG bug until I was told that the use of PROF is prohibited beyond the FAF. As Dan said, your best bet is FPA. It isn't as convenient as the Boeing, but does the job well most days.Paul