Date: 201510
Local time of day: 1201-1800
Location: SCT.TRACON, CA
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class E SCT
ATC / advisory: TRACON SCT
Second aircraft: Skyhawk 172/Cutlass 172
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types
Detector: Automation Aircraft RA; Automation Aircraft TA; Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Took Evasive Action; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Procedure; Human Factors; Airspace Structure
Primary problem: Procedure

Narrative: Departing PSP via the CATHEDRAL ONE departure assigned 8;000 feet via clearance then amended to 5;000 feet from Tower as we were cleared for takeoff. 26;000 [thrust] as per Takeoff Performance System (TPS) and max power due to variable winds resulted in a high rate of climb. PSP departure handed us off to SOCAL and upon checking in with them they cleared us to 10;000 feet as we were making the right turn to the PSP VOR. Approaching 5;000 feet at 250 KTS SOCAL alerted us to traffic at 6;000 feet and we saw it on TCAS. We were still in the 180 degree turn to PSP and the traffic was north of us (forward and left as we turned). At no time did they restrict our climb and we heard them trying to alert the C-172 of our position to which we heard him reply negative contact.I searched but could not see the traffic visually (VFR >60 NM visibility) and I noticed our closure on the TCAS target. We then got an TA which immediately became a RA with the command 'monitor vertical speed/climb' immediately followed by 'descend; descend now' command with the accompanying displays on the FDs. FO is the pilot flying and he responded to the RA; but with the momentum of our climb rate to an abrupt descent we closed to at least 500 feet and I only saw the aircraft (C-172) just as we passed directly underneath him as we began the descent in response to the RA. I told SOCAL we were responding to an RA with no reply as they were talking to the C-172. We descended back to 5;000 feet +\- accelerating to 270 KTS unintentionally; then resumed the departure once clear.Note: This entire event took just several seconds. Altitudes and airspeed are approximate; as I was primarily searching for the traffic and then scanning the PFD and ND intermittently.Lessons learned:1) The TCAS works and needs to be promptly responded to regardless of how abrupt the maneuver.2) Know your physics; The mass; speed and energy of our 150 knot aircraft is difficult to change directions in a timely manner.3) There was a severe lack of coordination between PSP Tower/Departure and SOCAL. Had we not been cleared above 5;000 feet; I doubt I'd be writing this. At no time did we hear SOCAL give us or the C-172 any maneuver instructions that would have given us greater separation.4) PSP is class D airspace and no separation services are provided to VFR aircraft. In 3 turns in/out of PSP this month; this is the 3rd incident in which our aircraft's flight path was interfered with by GA traffic. The first time resulted in my having to break off the approach and over fly the airport. In that same incident; the controller had to give the GA pilot an 800 number to call for a violation.5) The commercial airlines operating to PSP need to petition the FAA to have the airspace over PSP to be upgraded to class C to safely control and manage the GA aircraft in relation to the commercial aircraft around that airport. The GA aircraft are 'funneled' over the PSP ATA due to the surrounding terrain causing these close encounters. I'd be very surprised if there are not ongoing safety concerns because of this.




Synopsis: B737-800 Captain experiences an airborne conflict with a C172 at 6;000 feet during the CATH1 departure from PSP. TCAS commanded a descent while the aircraft was climbing at a high rate of speed and 5;500 feet was reached before descent begin. The reporter has some comments on ATC handling of the incident.