CAPT OF CPR CL601-3A ON ILS APCH DSNDS BELOW GS AND ALLOWS AIRSPD TO DROP BELOW VREF. CAPT HAD TURNED OFF THE GPWS.

Narrative

I WAS THE FO (PNF) ON THE LAST LEG OF A 2-DAY TRANSCONTINENTAL CPR FLT. I WAS FLYING FOR THE FIRST TIME WITH THIS PARTICULAR SENIOR CAPT; A FELLOW WITH A REPUTATION AS A CANTANKEROUS AND BITTER PLT WITH GOOD SKILLS BUT A LOW REGARD FOR STANDARD OP PROCS. WE WERE VECTORED FOR A NIGHT; VFR; ILS RWY 16 APCH AT HPN. WINDS WERE LIGHT; WE WERE LIGHT AFTER A 5 HR TRIP; AND HAD PLENTY OF RWY AVAILABLE. THE RWY IS SERVED WITH AN ILS AND 4 LIGHT PAPI. BOTH WERE OPERATING; AND THE ILS WAS TUNED ON BOTH PLTS' EFIS DISPLAYS. WE STARTED OUT 1 DOT HIGH AS WE DSNDED PAST THE MARKER; AND AS THE APCH PROGRESSED; WE SANK LOWER AND LOWER ON THE GS AND OUR SPD DROPPED WELL BELOW VREF. I MADE THE DEV CALLOUTS REQUIRED BY COMMON SENSE AND THE COMPANY SOP; TO WHICH THE CAPT RESPONDED WITH A GRUNT OR A SLIGHT THROTTLE MOVEMENT. I DID NOT SUSPECT INCAPACITATION. BY THE TIME WE WERE 1/2 TO 3/4 MI FROM TOUCHDOWN; WE WERE AT FULL FLY-UP GS DEV AND ALL RED PAPI LIGHTS; WITH THE SPD AT VREF -5 KTS. WONDERING WHY THE GND PROX SYS HADN'T SOUNDED; I LOOKED OVER TO SEE THAT THE CAPT HAD DISABLED THE GPWS CALLOUTS. WE LANDED WITHOUT INCIDENT. KNOWING HIS LIKELY RESPONSE; I DID NOT ASK THE CAPT ABOUT THE APCH. HE NEVER BRIEFED THAT IT WOULD BE OUTSIDE OF SOPS OR EXPLAINED WHY HE HAD FLOWN IT AS HE DID. I BROUGHT THE INCIDENT UP WITH OUR COMPANY'S TRAINING CAPT. I AM SUBMITTING THIS RPT BECAUSE IT IS AN INCIDENT THAT VIOLATED COMMON SENSE IF NOT THE FARS AND SOPS. WE DRAGGED THIS AIRPLANE ACROSS THE TREETOPS.