Date: 201709
Local time of day: 1801-2400
Location: N90.TRACON, NY
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B N90
ATC / advisory: TRACON N90
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Communication Breakdown
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Air Traffic Control; Person Flight Crew; Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Became Reoriented
Contributing factors: Human Factors; Airspace Structure; Procedure
Primary problem: Airspace Structure

Narrative: We were on radar vectors for the RNAV GPS RWY 31 Approach into LGA. We were communicating on frequency 134.9. On the downwind northeast of LGA; the controller cleared us 'Direct To' CHALN IAP on the RNAV GPS RWY 31. We were not cleared to intercept the final; nor cleared for the visual; nor cleared for the approach. Approaching CHALN IAP myself and my FO (First Officer) noticed an aircraft approaching the final inside CHALN from the south side of the final approach course approximately 1.5 to 2 NM at our 2 O'clock position. Reaching CHALN at approximately 90 degree intercept to final my FO and I both concluded that the controller was taking us through the final for spacing on the preceeding Aircraft. Of note the frequency was congested and we could not get a word in to get clarification from the controller on what he wanted after passing CHALN IAP. We continued on the heading we were on after passing CHALN until it became apparent that we were approaching JFK airspace. I; at this point; was telling the FO that we needed to tell the controller we needed a right turn back towards LGA. Before the FO could do this the controller came up and gave us an immediate right turn to heading 360 with a climb to 3000 feet from 2000 feet. The controller then made a comment to the effect 'I thought you were smart enough to intercept final'. I then indicated we would call TRACON when on the ground. The controller then made a comment to the effect that 'yes if we could figure out how to use the phone'. Once on the ground I called NY TRACON and spoke with a controller. I asked for a supervisor and it was indicated to me that there was no supervisor present. I explained the situation my Flight was in while on Radar vectors. He indicated to me that it was EXPECTED of me to turn final after reaching the IAP. I told him that was not our clearance and he reiterated that this is what most pilots do operating in this airspace. I realize after reaching CHALN IAP I should have entered a standard holding pattern on the course that I was on inbound to CHALN IAP. This in my mind was a dangerous proposition because once back inbound to CHALN at 2000 feet I would have been nose to nose with the aircraft that was following me causing without a doubt an RA maneuver. This event occurred because of an improper clearance in the terminal environment along with the fact the frequency was quite congested at the time. As a crew we were assuming what the controller was trying to do with us when we should have immediately upon receiving the clearance direct to this waypoint questioned what was expected once arriving over the waypoint. To prevent this from happening in the future it is my opinion that the controllers should comply with their handbook with regards to issuing ambiguous clearances and we as pilots should not assume what the controller may be wanting to do with us especially in a crowded frequency congested terminal environment.


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


Synopsis: The flight crew of a Boeing 737 reported that ATC cleared them 'Direct To' a way point without further instructions or clearances after they arrived at the way point.