Date: 201602
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: 0.75
Light: Daylight
Aircraft: Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Communication Breakdown
Second reporter function: Pilot Flying; Captain
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Procedure; Weather; ATC Equipment / Nav Facility / Buildings
Primary problem: Ambiguous

Narrative: On arrival Approach held us due to poor weather. After being released from holding; we were at the front of the train for approach. Current ATIS was calling for 3/4 SM visibility with -SN. Upon checking the RNP Availability Forecast (RAF); we discovered that 0.11 was N/A for a 30 minute window that was just beginning; and it would certainly be in effect throughout the duration of our approach and landing. Approach then cleared us for the RNAV (RNP) Y approach. Looking at the approach plate; the visibility minimums are RVR 50 or 1 SM for RNP 0.11; however; minimums are 1 1/4 SM for RNP 0.18 which is all the RAF supported flying for this 30-minute window.I queried Approach about the visibility to which the Controller replied that it was 'one mile.' I responded that we needed 1 1/4 SM to legally fly the RNAV Y Approach based on the RAF; and he didn't seem to understand what I was referring to. At that time; another company crew stated 'you must be looking at the RNAV Z; he wants the RNAV Y' which was incorrect. The RNAV Z is a GPS Approach; not an RNP Approach; and we didn't have the weather to fly it even if we wanted to. After several exchanges with Approach in which I was adamant that we needed 1 1/4 SM to fly the RNAV (RNP) Y Approach; he recleared us (and the arrival train behind us) for the ILS.Perhaps this is already an ATC procedure; I don't know; but perhaps Approach should view and understand the RAF prior to clearing aircraft for approaches that they cannot legally fly.


Second narrative: We experienced poor weather and ground stops throughout the day. Our flight; was delayed for about 110 minutes. We finally took off and made our way to [our destination]. Prior to starting the descent; the PNF (FO) checked ATIS multiple times as it changed every few minutes. The last ATIS prior to our landing reported 3/4 SM -SN RNAV (RNP) Y approaches in use. The RNAV (RNP) requires a RAF of .11 to use the 5;000 feet RVR or 1 minimums. ATIS was not reporting any RVR; but Approach claimed Tower was calling the RVR better than 6;000 feet. Okay; not bad; but the RAF report was calling for a .11 outage; right in the middle of our landing. Therefore; my FO and I decided it would not be legal to fly the approach since the next higher minimums (RAF .18) needed 1 1/4 miles. No mention of RVR. We needed the ILS since it offered minimums with both RVR and SM and the 6;000 feet RVR reported by Tower.It required many radio calls to Approach to help them understand the situation. It appeared they didn't understand what we were trying to get across to them. They continued to give the RNAV Approach clearance to other crews coming in. Some; like us; responded they were unable and requested the ILS. Shouldn't they be smarter about this stuff?


Synopsis: Air carrier flight crew reported being cleared for an RNP approach that they could not legally fly due to a RNP Availability Forecast (RAF) .11 outage. Other crews were not aware of the NOTAM and this crew had difficulty convincing ATC that an ILS approach was required.