Date: 201511
Local time of day: 0601-1200
Location: SJC.Airport, CA
Flight conditions: VMC
Light: Daylight
Aircraft: Medium Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Takeoff / Launch
Airspace: Class C SJC
ATC / advisory: TRACON NCT
Aircraft component: Transponder
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Confusion
Second reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: Upon calling Departure; the Air Traffic Control notified us that we were squawking the wrong transponder code and assigned us a heading in line with the SID. He immediately reminded us of the proper code for that flight. I put the transponder in standby mode until I entered the correct code but then I failed to return it to the number two position. After flying on that heading for a few minutes I queried the controller about our next vector towards our route. He didn't remember who or where we were. I caught that the transponder was still in standby and eventually he vectored us on course. I didn't finish going through our PDC and my First Officer missed my oversight. Normally I run a little top-to-bottom flow of the PDC but this time I zeroed in on the change in the route and I never got back to the rest of it. I brief four key areas of the PDC in my briefings but I don't expect the same technique from my First Officers. In the future I will listen for those four items and verbally add them myself if need be. I will also stop placing the transponder in standby while changing codes.


Second narrative: We departed KSJC normally. Tower handed us off to NORCAL departure. We called NORCAL and they asked us to change our transponder code. This is when the Captain realized he had forgotten to set the proper code and I realized I had not double checked it. In setting the new code the Captain turned off the transponder in order to not trigger 77** codes and then due to task saturation did not reset the transponder on. We were given a heading and altitude by NORCAL which we replied with and complied with. After maintaining the assigned heading and altitude longer than normal we queried NORCAL who apparently had forgotten about us. NORCAL asked who we were and where we were and we responded and the Captain realized the transponder was off and turned it on. NORCAL then found us and gave us vectors and everything was fine from then on. Captain forgot to set the transponder code when entering in the PDC clearance. I forgot to verify the transponder code was not set. Extra attention needs to be given during the programming of clearance into the aircraft systems and other pilot should fully verify this has been done properly.


Synopsis: Flight crew took off with the improper transponder code set. Upon receiving the correct code from ATC; the crew left the transponder in the Standby mode while flying the ATC-assigned heading. ATC had apparently lost track of the flight until queried by the crew.