..."he was low on the approach, 4 reds on finals."
Weather minimums required this to be an ILS approach, (ILS Rwy-06 minimums 800 meters). Keep in mind that the ILS electronic glide path at many airports is not always precisely aligned with the VASI/PAPI, it often varies, as may be apparent in this approach to Rwy-06 at HAV.
Before turning "red," the left outer PAPI light in fact, remained illuminated
white until 150 feet on short final, which technically is within visual glide-path limits of narrow body airplanes as this Fokker. The R/A altitude announced "50" (feet) crossing the threshold, and that's not "low." (B747 threshold crossing heights at standard ILS installations is typically 53 feet).
On this required ILS approach, there was no (below) "glide-slope" warning, so the flight path must have been within the limits of the electronic glide path.
As a side note: Why would you give preference to the visual glide path guidance on short final during an ILS approach when on profile?
Especially if it were a coupled approach, on-glide-path, . . . would you suddenly go-around if you caught a visual glimpse of four "reds" on a PAPI, on short final at 100, or 150 feet?
