Date: 201510
Local time of day: 0601-1200
Location: BWI.Tower, MD
Flight conditions: VMC
Light: Dawn
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B BWI
ATC / advisory: Tower BWI
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Ground Incursion Taxiway
Detector: Person Flight Crew
When detected: In-flight; Taxi
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: ATC Equipment / Nav Facility / Buildings; Airport; Human Factors
Primary problem: Ambiguous

Narrative: While on arrival into BWI; ATC changed runways from 33L to 15R and gave us a vector. About 10 miles out; we were cleared to 'fly heading 180 and join the Localizer' for 15R. On autopilot; we selected 180 heading and VOR/LOC. The aircraft captured a Localizer signal and starting turning east. It was apparent on the ND (Navigation Display) that it was not capturing the proper course. We deselected VOR/LOC and used Heading Select to go back to a 180 heading. I looked at the ILS ID on the PFD and crosschecked it against my ILS chart; but the IDs did not match. The airport had neglected to change the Localizer (same frequency) from 33R to 15L (the ID was for 33L). We picked up the airport visually; and were cleared for the visual.Then; once on the visual; I started to configure and was showing all white on the PAPI for 15R. I started to descend a bit; but felt low. I asked the Captain if he too saw all white; and he did. We referenced the VNAV on the ND it showed us about 200 ft low; which matched what I felt we were seeing out the window. We made a slight correction; and followed the VNAV down to the runway. The PAPIs showed all white all the way to the ground; even though we felt we were on proper glidepath; if not a tad low; with about a 650 fpm descent all the way down. We reported both the LOC and the PAPI to BWI ground. Potomac Approach and BWI need better coordination during runway change to ensure that the LOC is changed properly for the active runway. Not sure what to do about the PAPI; but it needs fixing.After landing; our gate was occupied; so we were cleared to join T Abeam terminal C. We thought we'd joined T; but Ground said 'You're on A; no problem; make a right on T short of E.' As we taxied back; we realized what had happened. Where T and A split; there is confusing signage on the ground in BWI. There is an arrow pointing left to 'join T' but what it really needs to say is 'straight'. We took the (harder) left and joined A by accident. Change the painted signage on the ground to indicate 'straight' to stay on T instead of a left turn.




Synopsis: B737 First Officer reports being switched to Runway 15R during arrival but ATC forgets to activate the localizer for Runway 15R. During the approach the PAPI shows all white even when low on the approach path. ATC is advised. After landing a taxiway incursion occurs which the First Officer believes is the result of an improperly placed arrow on the taxiway.