B767 Undifferentiated or Other Model
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Fatigue; Situational Awareness; Human-Machine Interface
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Flight Crew Became Reoriented; General Maintenance Action
Aircraft; Human Factors
Vectored to join the Rwy XX ILS inside ZZZZZ; called the field and cleared for the visual. Disconnected to autopilot to descend and join the glide slope (which was below us). Continued to hand fly since the Aircraft wouldn't lock the glide slope outside the localizer. As localizer came in; the flight directors remained on the horizon and unusable. I asked the FO (First Officer) to turn off and turn on both flight directors to regain their use. At that point (just outside ZZZZZ1) the flight directors were giving us good glide slope and localizer information. We put the gear down and commenced to slow to approach speed inside ZZZZZ1 (still hand flying) and I disconnected the autothrottles somewhere around 1000 ft. AGL. Approximately 600 ft. (inside 3 miles) we received an aural 'Glide Slope; Glide Slope' warning. At that time I noticed that while my flight director in the HUD and on the PFD was centered; the glide slope information was deflected all the way to the top of my display. A quick scan of the FO's PFD showed centered flight director as well. Checking the PAPIs for Rwy XX showed 4 red. I leveled off and added power to fly to the glide slope again; readjusted power; and landed uneventfully. No warnings or cautions were displayed.When we reconnected the Flight Directors inside ZZZZZ; descending on the glide slope; they came back directly where I wanted them showing me on glide slope and on course. I did not check LOC and glideslope annunciations on the PFD. Is it possible they did not capture the glideslope? I would doubt that since I got a Glideslope aural warning. I have no idea why the flight directors both sides had us descending below glide slope inside 3 miles on the approach. Wrote [a maintenance] entry; called [maintenance control] and conferenced in the Avionics tech for a verbal debrief on the gripe.I guess I could have caught the error had I been cross checking the glide slope on the right hand side of the HUD display; but I sit back far enough that I have to make an effort to see it; and it's not in my habit pattern on a visual. I'm normally working lineup; glide slope; airspeed; and any crosswind correction looking outside and through the HUD. It was my error for not scanning the PAPI to detect the gradual settle - which I'll put down to fatigue - but the flight director was centered! Long day. Error captured and uneventful landing - but very troubling to see the flight directors do that.
On visual approach to ZZZ Rwy XX; we were GS/LOC captured; on speed with the AP off. I was looking outside when the PF (Pilot Flying) asked me to cycle the FD's (Flight Directors). This was at approximately 1000 ft.; to my recollection; and I complied; ensuring the correct switches (FD's). After cycling them off then on; all appeared normal and the PF verbalized this. A few moments later; however; we were below GS which I noticed when I looked back outside and saw the PAPI. I remember hearing the aural 'Glideslope' warning once; but I do not remember exactly when this occurred. We did not receive any other alerts. The FD had been centered on my side; but I don't recall the GS indicator position. I did not notice the FMAs (Flight Mode Annunciators); which were likely no longer in approach mode: V/S (Vertical Speed) and HDG (Heading Hold) Hold; as I believe we never re-selected the Approach tile. I was looking outside at the PAPI which was red; and was starting to say this when the PF leveled off. He made airspeed corrections as well. We were red over white and stable at 500 ft. I did note then the GS indicated we were slightly low; consistent with a non-coincident PAPI. Landing was uneventful and we were VMC the entire approach with a visual clearance.The approach appeared normal to me until the PF asked me to cycle the FD's. Even immediately after; the aircraft appeared to be in the correct altitude/attitude. As I was focusing on making sure I had selected the correct switches (FD's); it took that small amount of time for the actual aircraft position to become apparent to me. I viewed my centered FD; which appeared normal; and visually crosschecked the PAPI's; which were abnormal - red over red; at approximately 800-700 ft. This led to a moment of confusion and I was not focused on the FMA's; which were likely in basic mode after cycling the FD's. As far as I remember; we never re-selected the Approach tile. With the delayed recognition of being low; receiving an aural GS alert; leveling off; throttle movement and airspeed monitoring; and thinking about a possible go around; a lot was occurring in quick succession. I failed to recognize the situation early and this could have led to an undesired state if left unchecked.My focus was outside until becoming distracted by the call to cycle FD's. My focus then shifted inside. While doing so; I failed to effectively monitor the aircraft position; PAPI; and FMA status. Focus must be on 'flying the aircraft' first and being a good pilot monitoring. I should have been more proactive in verbalizing the aircraft state; once noticed; and my attention should always be on active monitoring. I should have gathered more information about what the CA (Captain) saw when we cycled the FD's. Finally; my failure to notice the start of deviation from red over white to red over pink would have allowed more of a buffer to correct other failures; such as reselecting Approach tile or verifying the GS indicator against the PAPI as well as cross checking CA/FO indications.
B767 flight crew reported Flight Director malfunction on approach.