Date: 202012
Local time of day: 0001-0600
Location: VVNB.Airport, FO
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Final Approach
ATC / advisory: Tower VVNB
Reporter organization: Air Carrier
Reporter function: Relief Pilot; Captain
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Situational Awareness; Communication Breakdown; Human-Machine Interface
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Unstabilized Approach
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action
Contributing factors: ATC Equipment / Nav Facility / Buildings; Airport; Human Factors; Software and Automation
Primary problem: ATC Equipment / Nav Facility / Buildings

Narrative: During arrival to HAN; I was a jumpseat observer. We were at 2;000 ft. on the localizer; cleared for the ILS [Runway] 11 Left approach. Just outside the Final Approach Fix; I heard the Captain (Pilot Flying); say glideslope captured; and he set the missed approach altitude of 5;000 ft. in the altitude alerter. I was confused; because looking at the FO's (First Officer's) PFD (Primary Flight Display); I could see that we were below the glideslope; and it was no captured. I could not see the Captain's PFD to verify whether or not the glideslope was captured. The aircraft started descent from 2;000 ft.; even though we were not on the glideslope. I called out to check the glideslope and/or altitude. I did not have a hot mike; and maybe they weren't hearing me. The aircraft passed the Final Approach Fix approximately 500 ft. low. I called out the glideslope deviation again. The other jumpseat observer was also telling them to climb; and I yelled 'Go Around'. Then we got a GS caution with a line strike through the FMA on the PFD. At approximately 1;200 ft.; the go around was finally initiated with full scale deflection indicated on FO's PFD.During the surprise go around; we were instructed to maintain heading and climb to 5;000 ft. At some point the autopilot was disconnected; and situational awareness was deteriorating. The aircraft was veering to the right of track; 20 degrees nose up; and not following the flight director commands of 10 degrees nose up. I called out something like 'Who's flying the airplane; fly the airplane!' The flying pilot then steered back toward the flight director; regained control and the autopilot was re-engaged. After reaching 5;000 ft. we were vectored back for another approach to Runway 11 Left.Also of note; there was runway/taxiway construction at HAN airport that could have possibly created a glideslope anomaly. Though I could not see the Captain's flight instruments; it is possible there may have been a loss of glideslope indication at the start of the event. On the FO's PFD; I could see that the ILS was identified; and localizer/glideslope were displayed at all times.The Pilot Monitoring should have noticed on his instruments that the aircraft was not on glideslope; and should have called out the deviation immediately. When I saw the deviation; I was trying to alert the crew to fix the situation. I should have called out go around immediately.


Second narrative: While inbound on the localizer for RNWY (Runway) 11L; the glideslope was captured and the 'G/S' FMA was active. Shortly after capturing the glideslope; the 'G/S' FMA blinked and had a yellow strikethrough. The glideslope then started to fall beneath us; while the autopilot tried to increase the rate of descent. The Pilot Flying switched to V/S [Vertical Speed]; and rolled in more V/S down to stay on glideslope with a more than normal descent rate. I instructed to 'level off; level off' followed by 'climb back to 2;000 ft. It was then I noticed the glideslope dot had blinked and reappeared at two dots high; indicating we were low. The Captain in the observer seat then said 'Go Around; Go Around'. The Pilot Flying initiated the go around with the 'TOGA' [Takeoff Go-Around] switches and sometime thereafter turned off the autopilot. He then hand flew the go around to 5;000 ft. and present heading. After notifying Tower of our missed approach; we were told to contact Approach frequency. During this event; with my seat position; I was only able to observe the Captain's PFD [Primary Flight Display]. After landing safely and gathering all facts observed between crewmembers; it was apparent that the autopilot tried to capture a false glideslope and failed; thus giving us the yellow strikethrough the 'G/S' FMA."


Synopsis: Air Carrier Flight Crew reported un-stabilized approach.