Narrative:

Our gulfstream V departed on runway 30R at sjc. Cleared via the loupe one SID; linden transition. This SID requires a right turn to 120 degrees at 1.8 DME sjc VOR. We were cleared to climb to 5000 ft as per our pre departure clearance clearance and as reflected on the SID. Upon turning out towards the 120 degree heading; I checked in with norcal departure reporting climbing to 5000 ft. The designated first officer was at the controls in the left seat. I was the designated captain sitting in the right seat assuming copilot duties. The aircraft was flown in the FMS flight guidance mode with the autoplt engaged shortly after takeoff. The aircraft held course normally through the turn to a 120 heading after the 1.8 DME fix. Shortly after being established on the 120 degree heading; the aircraft; not known to me; began an inadvertent slow turn towards the sjc VOR. We were abruptly told by norcal departure to turn left immediately to a 120 degree heading. The pilot at the controls responded immediately turning the aircraft to the left rolling out on the 120 degree heading. I estimated that we were heading about 160 degrees when we were alerted by ATC. We were advised to contact ATC via telephone. ATC advised me that a loss of separation had occurred between our aircraft and a cessna 182. Later the next day the norcal operations manager stated to me via phone conversation that our position at the time of the occurrence was the 001 degree radial at 5 NM from the sjc VOR. He also stated that he was required to file a deviation report. Significant is the fact that the honeywell FMS navigation database we were using for this SID has the aircraft flying exactly as published on the SID; rolling out on the 120 degree heading; and then slowly directs the flight guidance system to turn towards the sjc VOR. Notably; this SID if flown using the honeywell navigation database actually flies the lost communication procedure as published on the SID; not the published SID procedure. We are trained to use the automation inherent to the gulfstream V to enhance safety by reducing cockpit workload; improving aircraft flight guidance and overall performance. On this occasion it set us up for this occurrence. I was distracted prior to the occurrence accomplishing the after takeoff and climb checklist as is our procedure climbing out of 3000 ft AGL. We never heard from norcal departure about any potential conflicting traffic until we received an immediate left turn command. In fact we heard very little norcal radio communications until the occurrence. We never received a TCAS target threat. This occurrence could have been prevented by: 1) flying the aircraft in heading select mode only; not allowing the FMS/flight guidance to turn the aircraft off of desired heading. 2) revising the honeywell navigation database to reflect a discontinuity between the 120 degree heading and the sjc VOR. 3) specify on the SID 'radar departure.' 4) eliminating the SID from the navigation database. 5) strongly recommending to norcal departure controllers; as they verify climbing traffic; to say; 'maintain heading 120 degrees.' callback conversation with reporter revealed the following information: reporter advised that their chief pilot had discussed the situation with honeywell and was advised that they published two different versions of this departure. One supposedly for general aviation aircraft which presents a continuous lateral navigation procedure back towards sjc after passing the 047 radial; the other as shown on the commercial loupe departure page which reverts to a route discontinuity after achieving the 120 degree heading and requires manual pilot intervention to recapture the departure to sjc based on vectors from nct. Neither the reporter nor the analyst could find any obvious justification for the continuous lateral navigation version.

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Original NASA ASRS Text

Title: FLT CREW OF G5 DEPARTING SJC ON THE LOUPE SID ARE SURPRISED WHEN FMC DATABASE TURNS THEM TOWARD THE SJC VOR VICE 120 DEG HDG FOR VECTORS AS DEPICTED ON THE PROC. LOSS OF SEPARATION RESULTS.

Narrative: OUR GULFSTREAM V DEPARTED ON RWY 30R AT SJC. CLRED VIA THE LOUPE ONE SID; LINDEN TRANSITION. THIS SID REQUIRES A R TURN TO 120 DEGS AT 1.8 DME SJC VOR. WE WERE CLRED TO CLB TO 5000 FT AS PER OUR PDC CLRNC AND AS REFLECTED ON THE SID. UPON TURNING OUT TOWARDS THE 120 DEG HDG; I CHKED IN WITH NORCAL DEP RPTING CLBING TO 5000 FT. THE DESIGNATED FO WAS AT THE CTLS IN THE L SEAT. I WAS THE DESIGNATED CAPT SITTING IN THE R SEAT ASSUMING COPLT DUTIES. THE ACFT WAS FLOWN IN THE FMS FLT GUIDANCE MODE WITH THE AUTOPLT ENGAGED SHORTLY AFTER TKOF. THE ACFT HELD COURSE NORMALLY THROUGH THE TURN TO A 120 HDG AFTER THE 1.8 DME FIX. SHORTLY AFTER BEING ESTABLISHED ON THE 120 DEG HDG; THE ACFT; NOT KNOWN TO ME; BEGAN AN INADVERTENT SLOW TURN TOWARDS THE SJC VOR. WE WERE ABRUPTLY TOLD BY NORCAL DEP TO TURN L IMMEDIATELY TO A 120 DEG HDG. THE PLT AT THE CTLS RESPONDED IMMEDIATELY TURNING THE ACFT TO THE L ROLLING OUT ON THE 120 DEG HDG. I ESTIMATED THAT WE WERE HEADING ABOUT 160 DEGS WHEN WE WERE ALERTED BY ATC. WE WERE ADVISED TO CONTACT ATC VIA TELEPHONE. ATC ADVISED ME THAT A LOSS OF SEPARATION HAD OCCURRED BETWEEN OUR ACFT AND A CESSNA 182. LATER THE NEXT DAY THE NORCAL OPS MANAGER STATED TO ME VIA PHONE CONVERSATION THAT OUR POSITION AT THE TIME OF THE OCCURRENCE WAS THE 001 DEG RADIAL AT 5 NM FROM THE SJC VOR. HE ALSO STATED THAT HE WAS REQUIRED TO FILE A DEV RPT. SIGNIFICANT IS THE FACT THAT THE HONEYWELL FMS NAV DATABASE WE WERE USING FOR THIS SID HAS THE ACFT FLYING EXACTLY AS PUBLISHED ON THE SID; ROLLING OUT ON THE 120 DEG HDG; AND THEN SLOWLY DIRECTS THE FLT GUIDANCE SYSTEM TO TURN TOWARDS THE SJC VOR. NOTABLY; THIS SID IF FLOWN USING THE HONEYWELL NAV DATABASE ACTUALLY FLIES THE LOST COM PROC AS PUBLISHED ON THE SID; NOT THE PUBLISHED SID PROC. WE ARE TRAINED TO USE THE AUTOMATION INHERENT TO THE GULFSTREAM V TO ENHANCE SAFETY BY REDUCING COCKPIT WORKLOAD; IMPROVING ACFT FLT GUIDANCE AND OVERALL PERFORMANCE. ON THIS OCCASION IT SET US UP FOR THIS OCCURRENCE. I WAS DISTRACTED PRIOR TO THE OCCURRENCE ACCOMPLISHING THE AFTER TKOF AND CLB CHKLIST AS IS OUR PROC CLBING OUT OF 3000 FT AGL. WE NEVER HEARD FROM NORCAL DEP ABOUT ANY POTENTIAL CONFLICTING TFC UNTIL WE RECEIVED AN IMMEDIATE L TURN COMMAND. IN FACT WE HEARD VERY LITTLE NORCAL RADIO COMS UNTIL THE OCCURRENCE. WE NEVER RECEIVED A TCAS TARGET THREAT. THIS OCCURRENCE COULD HAVE BEEN PREVENTED BY: 1) FLYING THE ACFT IN HDG SELECT MODE ONLY; NOT ALLOWING THE FMS/FLT GUIDANCE TO TURN THE ACFT OFF OF DESIRED HDG. 2) REVISING THE HONEYWELL NAV DATABASE TO REFLECT A DISCONTINUITY BETWEEN THE 120 DEG HDG AND THE SJC VOR. 3) SPECIFY ON THE SID 'RADAR DEP.' 4) ELIMINATING THE SID FROM THE NAV DATABASE. 5) STRONGLY RECOMMENDING TO NORCAL DEP CTLRS; AS THEY VERIFY CLBING TFC; TO SAY; 'MAINTAIN HDG 120 DEGS.' CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISED THAT THEIR CHIEF PLT HAD DISCUSSED THE SIT WITH HONEYWELL AND WAS ADVISED THAT THEY PUBLISHED TWO DIFFERENT VERSIONS OF THIS DEP. ONE SUPPOSEDLY FOR GENERAL AVIATION ACFT WHICH PRESENTS A CONTINUOUS LATERAL NAV PROC BACK TOWARDS SJC AFTER PASSING THE 047 RADIAL; THE OTHER AS SHOWN ON THE COMMERCIAL LOUPE DEP PAGE WHICH REVERTS TO A RTE DISCONTINUITY AFTER ACHIEVING THE 120 DEG HDG AND REQUIRES MANUAL PLT INTERVENTION TO RECAPTURE THE DEP TO SJC BASED ON VECTORS FROM NCT. NEITHER THE RPTR NOR THE ANALYST COULD FIND ANY OBVIOUS JUSTIFICATION FOR THE CONTINUOUS LATERAL NAV VERSION.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.