Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 116
No Specific Anomaly Occurred Unwanted Situation
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings
While on the visual approach into LEX Runway 4; inside the final approach fix and following the precision approach path indicator (PAPI) lights with two white and two red lights indicating on glide path; we started to feel we were low according to our actual sight picture. After referencing the electronic glide slope from the ILS we saw we were slightly more than half scale deflection low and corrected back onto the glide slope. We received a 'GLIDESLOPE' GPWS indication while correcting. When back on the glide slope we looked out at the PAPI again and saw it still showed two white and two red lights despite the change in glide path. The ILS chart for runway 4 does not mention that the glide slope and visual glide path are not coincident. I believe when we noticed we were low on the glide slope; the PAPI should have been indicating three reds and a white or maybe even four reds.There is something wrong with the alignment of the PAPI equipment for the runway. It should not have shown us to be two white and two red lights that low on the glide slope. The conditions were visual and easily fixed once we referenced the electronic glide slope fully.The Airport Operations Staff and the FAA need to conduct an alignment of the PAPI equipment. There could be a situation in low visibility or very dark conditions where an aircraft arrives at the minimum decision altitude; has the runway environment or approach lights in sight and relies on the PAPI to help keep the pilot's eyes outside to land; which could lead to an issue where they either see themselves as too high according to the PAPI (if it's aligned too low) or; if it only indicates two white two red at any altitude; may follow the PAPI to an unsafe landing either outside of the touchdown zone or short of the runway.
Air carrier Captain reported a problem with the alignment of the PAPI lights at LEX airport.