Date: 201809
Local time of day: 0601-1200
Location: SNA.Airport, CA
Flight conditions: Mixed
Weather elements / visibility: 10
Light: Daylight
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class C SNA
ATC / advisory: TRACON SCT
Reporter organization: Air Carrier
Reporter function: Pilot Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Situational Awareness; Time Pressure; Confusion; Communication Breakdown
Second reporter function: Pilot Not Flying; Captain
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: SNA ATIS - 1400 FT scattered using RNAV (GPS) Y 20R approach. 20R ILS NOTAM out of service. The RNAV (GPS) Y was loaded into the FMC and briefed. On handoff to SoCal Approach; the controller advised us to expect RNAV (RNP) Z 20R starting at KLEVR (IAF). The approach was loaded and briefed accordingly. Approximately 3 NM from KLEVR; SoCal canceled our approach clearance and assigned us a heading and new altitude of 3000 FT; with 'expect vectors to EHVOX (IF) on the RNAV Z.' After passing approximately abeam KLIPP waypoint on the RNAV Z; ATC gave us a right turn direct to the FAF waypoint ZETOV. Since we had just been vectored off the approach at KLEVR that required an RF leg (Ball note 6 on Approach Plate) and while still under IFR control; we questioned the controller about the assigned vector. ATC responded by giving us a right turn to a 270 degree heading. The controller then assigned us the RNAV (GPS) Y 20R Approach. The new approach was loaded and re-briefed. We were then assigned a north heading followed by a right turn to the southeast towards HUKEM. Due to the additive conditions of multiple approach changes from Y to Z back to Y and multiple vectors and altitude changes; our expectation bias was to have us join the RNAV Y Approach at SAGER (IF) based on the previous expect clearance on RNAV Z to EHVOX (IF). We tried to clarify our clearance with the controller at that point; but there was a complete breakdown in communication with ATC since neither of us had a shared mental model of how the approach was going to be conducted; so we decided that the safest course of action was to initiate a Visual Approach by calling the airport 'in sight' thus eliminating any further controller confusion. ATC then cleared us for the Visual Approach to Runway 20R. The remainder of the approach and landing were normal. The biggest issue in our case is with ATC changing their minds multiple times on a close-in approach assignment. It does not allow the crew time to fully brief the approach except for the big items. Also; when issued an expect clearance; and then given a clearance that differs from that; adds a layer of confusion since there is very little time to clarify what is expected unless it is obviously clear or explained in the clearance.


Second narrative: [Report narrative contained no additional information.]


Synopsis: B737-700 flight crew reported confusion resulted when ATC changed the clearance multiple times on arrival into SNA.