B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 218
ATC Issue All Types; Conflict Airborne Conflict
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Took Evasive Action
Procedure; Airspace Structure
Our takeoff altitude limit was changed from 7;000 feet as per the Pre Departure Clearance (PDC) to 'climb and maintain 3;000'' after takeoff. We took off; I was flying; and then we received a clearance from Departure Control to climb to 4;000 feet. Then we were given a climb to 6;000 feet. I did notice multiple TCAS targets in the area. Then we were given a Controller change. He called us without us checking-in and gave us an immediate descent to 4;000 feet. I reacted quickly to initiate a descent to 4;000 feet. Passing around 5;000-5;500 feet; we received a significant climb RA opposite of what ATC was telling us to do. Again; I reacted promptly to initiate and follow the climb RA as instructed and taught to do so. I followed the TCAS RA advisory until 'Clear of Conflict' was heard and a climb to 14;000 feet was given to us by ATC. I have always been taught to follow a TCAS RA instructions. That is great technology; and the rest of the flight was uneventful.Perhaps change the departure procedure out of Ontario; or have the airspace more clear through that valley on the PRADO. There were a lot of VFR targets. Maybe even a VFR corridor.
I was pilot monitoring from ONT on the PRADO Departure from Runway 26R; our clearance was initially to 4;000 feet. Soon after takeoff; Departure cleared us to 3;000. There was much traffic south of ONT at this time. On Departure frequency; the [controller] then cleared us to 4;000 feet; and then to 6;000 feet. We switched to Departure frequency and as we were climbing through approximately 5;500'; [ATC] told us to immediately descend to 4;000 feet. The pilot flying disconnected the autopilot and began an immediate descent towards 4;000 feet when soon after we got a significant climb RA opposite to his call. We immediately responded to the climb RA and called Departure to let him know we were responding to a climb RA. He then cleared us higher and there was no further conflict.I am not sure what happened to cause this problem. However; we immediately responded to the Controllers call to descend; and then immediately followed the subsequent significant climb RA thinking that the Controller's direction might have been in error.
B737 flight crew departed ONT on the PRADO departure and was cleared to 6;000. The next Controller gave them an immediate descent to 4;000 feet and the climb was reversed just as the TCAS issued a climb RA which was complied with.