Air carrier flight crew reported not complying to briefed climb power setting resulting in a 'terrain too low' warning. Crew added thrust and continued climb.
Synopsis
Air carrier flight crew reported not complying to briefed climb power setting resulting in a 'terrain too low' warning. Crew added thrust and continued climb.
Narrative
Was flying the noise abatement departure procedure off of 20R leaving SNA. At 800AFE; turned off auto throttles and pulled back power. I focused on the note on the departure procedure stating not to delay in thrust reduction; and I overshot the 78% thrust target. We then heard the caution chime and I assumed it was the TLA (Throttle Lever Angle) NOT TOGA" caution that happens on that departure. However my captain and I were both startled to hear the GPWS "terrain" callout followed by the "landing gear" audible alarm. My captain called gear up; and I told him they were already up; as they were already raised at their proper time. By this time I had also returned the thrust levers to thier proper 78% position; and all aural alarms ceased. We then flew the rest of the procedure as published and debriefed when we got out of sterile. Cause: My action of overshooting the target power caused the plane to slow its climb; prompting the "terrain" callout. The "landing gear" callout then added confusion and startle delay to our corrective action. Suggestion: When flying the noise abatement procedure leaving SNA or other similar noise abatement procedures that require a thrust reduction; reduce thrust at a more appropriate rate to balance not overshooting the thrust target; and not delaying the reduction. Also; as stated on the departure plate; any abnormal condition such as the "terrain" callout we received should have resulted in stopping the noise abatement procedure and responding with the appropriate terrain avoidance procedure."
Second reporter narrative
I was PF performing the noise abatement procedure takeoff in SNA. We briefed the plate together during our arrival brief. Upon reaching 600 feet; the FO disconnected the AT (autothrottles) as briefed. Upon reaching 800 feet; the FO started to bring the power back as directed but brought the thrust back too far. We continued climbing and heard a Terrain too low" warning. We also heard a "Landing Gear" warning. I was confused and called for gear up; thinking I had missed that somehow. The gear was already up. I then noticed that the N1 was set to around 63% and told the FO to put it at 78.1% as directed by the complex departure. At this point the aural warnings stopped. This all happened very quickly. We continued the climb with no further issue. Cause: Improper application of complex departure procedure. Suggestion: Ensure thrust setting is correct on complex departure procedure.Respond properly to EGPWS (Enhanced Ground Proximity Warning System) warning as outlined in SOP even with this specific complex departure procedure."
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.