Date: 201701
Local time of day: 0601-1200
Location: ONT.Tower, CA
Flight conditions: VMC
Light: Daylight
Aircraft: Cessna 180 Skywagon
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Climb
Airspace: Class C ONT
ATC / advisory: Tower ONT
Second aircraft: B737 Undifferentiated or Other Model
Reporter organization: Personal
Reporter function: Single Pilot
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown; Confusion; Distraction; Situational Awareness; Workload
Anomaly: ATC Issue All Types; Airspace Violation All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft RA; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Clearance
Contributing factors: Human Factors; Environment - Non Weather Related; Airspace Structure; Procedure
Primary problem: Airspace Structure

Narrative: Explanation of a possible altitude deviation in a Cessna. I requested a flight following to Mojave Airport with a departure to the North and a cruise altitude of 8500 ft with CNO Ground Control. I received an altitude restriction of 2000 ft; a squawk code and instruction to contact ONT tower for the northbound transition. I took off and I leveled at 2000 ft when I was instructed to contact ONT tower. I switched frequencies and there was complete congestion on the frequency with aircraft repeatedly blocking each other and the controller. I found an opportunity to check in and advised we were restricted to 2000 ft. The controller called traffic at my two o clock: a 737 climbing out of ONT. I replied: 'Aircraft X; looking for traffic.' Immediately after my reply I had the traffic in sight but I was unable to report it in sight due to frequency congestion for approximately one minute; all the while I was maintaining visual contact with the 737. Right as the 737 was about to pass overhead and above me; I was able to report it in sight to Tower and requested higher. Tower replied 'Aircraft X maintain visual separation from that traffic caution wake turbulence.' More transmissions blocked the frequency and I was unable to reply. Several seconds later when the 737 was above and behind us; still in my sight; the controller repeated 'Aircraft X maintain visual separation from that traffic caution wake turbulence.'By the time I was able to reply 'Wilco [call sign]' we had flown underneath the aircraft and were clear of it and never encountered any wake turbulence. At this point we were at a position Northwest of ONT; still in their airspace and my passenger in the right seat; a licensed pilot; called attention to traffic ahead at our same altitude in the Cable Airport traffic pattern. I saw the traffic immediately; there were at least three airplanes in the pattern which is at 2;243 MSL and we were approaching them. I was still unable to communicate with Ontario tower due to frequency congestion and I initiated a climb in the interest of safety. In the climb my passenger and I were both visually scanning for traffic and using our on-board ADS-B for additional traffic awareness. As we were overflying the final approach at Cable; Ontario tower called us and said 'Aircraft X I did not issue you a climb; you were restricted to 2000 ft. Contact SoCal Departure.' I replied 'Aircraft X switching to departure; I apologize for the climb.' Upon checking in with SoCal; they gave me a phone number to contact regarding a possible pilot deviation. Instead of continuing with our original plan; I elected to fly to Mojave and land to make the phone call as expeditiously as possible. On the phone; the controller told me the 737 had received a TCAS alert and maneuvered to avoid me.From my perspective this event was triggered mainly due the congestion on the Ontario tower frequency. The primary reason for my climb was to avoid traffic in the Cable airport traffic pattern; with which we had an imminent conflict; and we were not on their frequency. From my position I could see clearly that there would be no further conflicts if I climbed straight ahead. If this action created a TCAS RA with the 737 I sincerely apologize; but I do believe I was acting at all times in the interest of safety.




Synopsis: C180 pilot reported of a transition through ONT and CCB that caused an RA. Pilot had all traffic insight; but could not advise ATC because of frequency congestion.