B787 flight crew reported an unstabilized approach which resulted in descending below the glide path in visual conditions. The pilot stopped the descent; corrected to the glide path and landed.
Synopsis
B787 flight crew reported an unstabilized approach which resulted in descending below the glide path in visual conditions. The pilot stopped the descent; corrected to the glide path and landed.
Narrative
Leading up to event: observed from jumpseatCleared direct ZZZZZcleared visual XXR1600 was set in ALT SELECT windowHigh on path but correcting PF selected FLCH and went flaps 20 gear downLNAV was captured PF called for flaps 30VNAV was not armed PF called for touch down zone elevation to be set in the ALT SELECT windowBecause VNAV was not armed we ended up sinking below the VNAV pathWe ended up 3 red and one white on the PAPIWe were still in FLCH at 900 ft PM Selected VS At the point we realized we had dipped below the path the pilot flying clicked off the Autopilot to get back on the path. At the same time the auto throttles became disengaged and we ended up about 8 to 10 kts. below REF speed. PF Promptly recovered and auto throttles we re engaged. We were stable at 500 ft and an unrvenful landing was performed on XXRIn the future I believe we should have initiated a go around. It was a learning experience for the entire crew. A root cause of this even was not verifying FMA's (Flight Mode Annunciators)
Second reporter narrative
Was held high at 5;000MSL then given a turn direct to ZZZZZ on the visual XXR. There was some confusion if cleared for the visual or not due to ATC giving point outs to parallel traffic and asking if we could slow in time to avoid overtaking that traffic. Direct ZZZZZ was input in the FMC and LNAV engaged. When confirmed cleared for the approach the ZZZZZ crossing altitude was input in the MCP (Mode Control Panel) (still in FLCH mode). During this time attention was focused on slowing and maintain visual with the parallel traffic. Approaching ZZZZZ the PF attempted to run a check but failed to confirm that FMA (Flight Mode Annunciator) had transitioned to VNAV. In the a portion of the check the PF asked the PM to set TDZE. Passing ZZZZZ the aircraft descend approximately 1 degree below GP and the PF turned off the autopilot and manually corrected towards the GP. The airspeed then started to decay to approximately 5-7 < vREF and the PF manually increased thrust. There was initially some confusion in the cockpit as to why the auto throttles were not holding airspeed. This was cleared up with the realization that FLCH was still engaged. The PF corrected to on-speed and GP and landed uneventfully. With time distortion it is difficult to accurately remember the exact height but best recollection indicates that FLCH may have been engaged down to 900' AGL.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.