Whereas PAPI, due to its ACROSS pos. to the RWY´s long. axis, creates CONVERGENT, i.e., DIFFERENT DEGREEE G/S´ . Therefore, following 3W´s - 1 R will only bring the a/c in a steeper desc. but the wheels to a height equal to the lower g/s on the VASIS if followed.
Yes.
Shouldn´t I be intersecting the whites and reds in my way down in order to follow the ILS down to 200´ ?
If the ILS and the PAPI are aligned and both at 3°, then you must be seeing 2 whites and two reds the whole way down the ILS,
unless the glideslope antenna (on the aeroplane) is on a different vertical level to the cockpit, in which case there may be a slight difference (as Intruder alluded to). If the GP antenna is below the cockpit eg under the nose somewhere, the pilots will (may) see a very slightly steep indication on the PAPI which would get worse as the aircraft got closer to touchdown. If this is practically the case I don't know, never having flown a big, long jet (too much fuel in the fuel tanks for me...).