Super King Air 200
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor
Flight Crew Last 90 Days 70; Flight Crew Total 5017; Flight Crew Type 678
Workload; Time Pressure
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors; Procedure
Cleared Route:  Heading 255 to join V186 V459 LHS EHF then as filed.  Climb and maintain 4000 feet; expect FL220 in 10 minutes.  ONT Tower cleared us for takeoff from runway 26L with instructions to maintain 3;000 feet on departure.  Prior to takeoff; we waited holding short of 26L for a Heavy to clear runway 26L.  That aircraft had been back taxiing 26L and was positioned behind our aircraft on taxiway S.After takeoff; ONT Tower handed us off to SoCal Approach.  Shortly after checking in with SoCal; the controller cleared us direct POM VOR direct VNY VOR.  Neither waypoint was in the cleared route.  I told the approach controller that information.  Controller responded again with cleared direct POM and an instruction for after POM that I did not fully hear.  At some point conttroller also cleared us from 3;000 feet to 8;000 feet and wanted us to expedite.POM VOR was not part of the cleared route; and therefore it was neither in the GPS flight plan nor tuned into the NAV radio receiver.  Programming the new clearance required a few seconds of time and that seemed to annoy the approach controller.  After getting POM programmed into the GPS and directing the aircraft toward the POM VOR; I queried the controller for the next waypoint clearance.  I understood that after the POM VOR; I was to fly heading 280 to join V459.After getting the POM VOR programmed into the GPS; I was attempting to clean up the remainder of the programmed flight plan when the aircraft (on autopilot and NAV mode engaged) began a left turn to the next waypoint in the GPS which happened to be a point on V186 which was south of the aircraft's position.  The GPS had cycled to the next waypoint; and the turn prediction component of the navigation software lead the turn.  I quickly directed the aircraft back to the POM VOR using HDG mode and after POM turned to heading 280 as instructed.Receiving a new clearance shortly after takeoff is unsafe when it requires new programming of navigation equipment.  A safer solution from the controller would have been to provide a radar vector.  I cannot recall ever receiving a re-route just two minutes after departure while still on an initial assigned departure heading.  The first waypoint of the new clearance (POM VOR) was so close that there was very little time to get the new route programmed before passing that first waypoint (POM VOR) of the new clearance.I suspect that the approach controller had the Heavy departing right behind us; and that approach wanted [us] out of the path of the faster jet. The SoCal approach facility and the ONT Tower should have better coordinated the departures; and SoCal Approach should have been aware of the route on which [we] had been cleared.  SoCal Approach seemed quite confused and overwhelmed.  For my part; I should have simply asked SoCal approach for a radar vector (heading) when it became clear that the controller and I had differing route expectations.I suspect that the original clearance received on the ground from ONT Clearance Delivery was not what the SoCal Approach Controller was expecting because the original clearance received on the ground did not include the POM V264 information.  Again; to reiterate; the POM V264 information was not communicated as part of the IFR clearance received while on the ground.  Furthermore; V264 was never communicated while airborne.
BE20 pilot reported confusion and an unsafe situation when ATC issued a new route clearance just two minutes after departure.