Corporate jet crew reported a CFTT event after misinterpreting the PDC they received which was 'No SID; fly runway heading.' ATC provided a vector to correct the initial turn the crew made to avoid terrain.
Synopsis
Corporate jet crew reported a CFTT event after misinterpreting the PDC they received which was 'No SID; fly runway heading.' ATC provided a vector to correct the initial turn the crew made to avoid terrain.
Narrative
On Departure from BOI enroute to ZZZ I was the PF. We had received a clearance of No SID; fly runway heading. I briefed the PNF the BOI3 departure as that is what we filed and did not catch the discrepancy between filed and accepted clearance through PDC as that was what programmed in the FMS. On departure through our safe altitude; the PNF selected direct to the first fix on the flight plan and I accepted LNAV navigation. ATC subsequently advised a terrain alert and issued a turn to the south. We were subsequently notified of a possible deviation and continued on course to ZZZ. My initial reaction to my PNF selecting direct to the first fix was questionable but he had stated the clearance was 'No SID' so I agreed with the turn on course and asked for LNAV mode resulting in a turn that had ATC take action. I feel I did not brief adequately to head off the confusion of an expected clearance vs a received clearance. A contributing factor is we were 'cleared for takeoff' without a runway heading or cleared on course statement.
Second reporter narrative
We received our clearance via PDC that stated 'NO SID; CLEARED AS FILED'Both the PF and I (PM) missed the 'Fly runway heading' below.On takeoff clearance we received 'Aircraft X cleared for takeoff runway 10 right'We were not given a heading with our takeoff clearance.On takeoff we were in heading mode and in the FMS the BOI3 was loaded. Subsequently after takeoff; above our TOSA; I entered direct VALYY into the FMS to clean up the flight plan and remove the BOI3 as that was not what we were cleared. I then stated 'I've got us direct VALYY' to the pilot flying and NAV mode. This initiated a turn to the left towards VALYY. The controller immediately responded with a vector to the right; which we followed.After a post flight discussion we believe this could have been prevented with a more thorough review of our clearance and detailed takeoff briefing. Additionally we discussed a contributing factor as not being assigned a heading or fix with our takeoff clearance.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.