Narrative:

On departure from sjc; runway 30R we were complying with the LOUPE1 SID which requires a right turn to heading 120 degrees at 1.8DME to cross the 047R/sjc at or below 5000 ft. Navigation mode was selected at 400AGL; the departure had been properly input into the FMS and checked prior to departure. The aircraft was left configured for a dirty turn and the captain (PF) engaged the autopilot at approximately 2000 ft just prior to the turn southeast. I checked in with norcal departure and the aircraft initiated the right turn towards heading of 120. However; the initial bank angle commanded by the FMS was only approximately 15 degrees. After monitoring the departure; we determined that the angle of bank was not going to be sufficient and was not increasing further. It appeared our turn was wider than we had planned. I commented to the captain that we needed to turn tighter to remain on course; he agreed and proceeded to pull the heading select knob; taking control of the turn manually increasing bank angle. At about the same time; norcal departure mentioned that we needed to tighten the turn and I told him we were doing just that when we rolled out on the heading of 120; we were on the FMS planned path (magenta line) for the departure. The aircraft was then again placed in navigation mode; cleaned up; and we proceeded with the remainder of the departure with no further issues. Under a situation such as this we should be making any first turn approaching; or greater than 90 degrees from runway heading in heading mode and not navigation mode; unless the aircraft is accelerated and cleaned up prior to the turn. This will ensure that appropriate bank angle is used; rather than assume the FMS will comply with SID turning requirements. If left to its own devices; the FMS will continue to overshoot those turns by only commanding 15 degrees of bank until aircraft is cleaned up and speed increased to satisfy turn logic and then return to the course line.

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Original NASA ASRS Text

Title: Air carrier departure via the LOUPE1 SID from SJC was unable to accomplish the south easterly turn within the required parameters in the NAV MODE. Flight crew intervened with heading select commands to increase turn rate.

Narrative: On Departure from SJC; Runway 30R we were complying with the LOUPE1 SID which requires a right turn to heading 120 degrees at 1.8DME to cross the 047R/SJC at or below 5000 FT. NAV mode was selected at 400AGL; the departure had been properly input into the FMS and checked prior to departure. The aircraft was left configured for a dirty turn and the captain (PF) engaged the autopilot at approximately 2000 FT just prior to the turn SE. I checked in with NorCal Departure and the aircraft initiated the right turn towards heading of 120. However; the initial bank angle commanded by the FMS was only approximately 15 degrees. After monitoring the departure; we determined that the angle of bank was not going to be sufficient and was not increasing further. It appeared our turn was wider than we had planned. I commented to the Captain that we needed to turn tighter to remain on course; he agreed and proceeded to pull the HDG select knob; taking control of the turn manually increasing bank angle. At about the same time; NorCal Departure mentioned that we needed to tighten the turn and I told him we were doing just that When we rolled out on the heading of 120; we were on the FMS planned path (magenta line) for the departure. The aircraft was then again placed in NAV mode; cleaned up; and we proceeded with the remainder of the departure with no further issues. Under a situation such as this we should be making any first turn approaching; or greater than 90 degrees from runway heading in HDG mode and not NAV mode; unless the aircraft is accelerated and cleaned up prior to the turn. This will ensure that appropriate bank angle is used; rather than assume the FMS will comply with SID turning requirements. If left to its own devices; the FMS will continue to overshoot those turns by only commanding 15 degrees of bank until aircraft is cleaned up and speed increased to satisfy turn logic and then return to the course line.

Data retrieved from NASA's ASRS site as of April 2012 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.