Date: 201710
Local time of day: 1201-1800
Location: HNL.Airport, HI
Flight conditions: VMC
Weather elements / visibility: Cloudy; 10
Light: Daylight
Aircraft: B767-300 and 300 ER
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B HNL
ATC / advisory: TRACON HCF
Aircraft component: ILS/VOR
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance; Flight Crew FLC Overrode Automation; General Maintenance Action
Contributing factors: ATC Equipment / Nav Facility / Buildings; Aircraft
Primary problem: Aircraft

Narrative: PHNL Pilot Monitoring; Weather: scattered clouds 10 miles visibility. Cleared for ILS 08L PHNL; 3000 FT until established. Upon LOC; capture Approach mode selected on FMP (Flight Management Panel).Aircraft intercepted and descended on the glideslope in visual conditions with runway in sight. 'Autopilot' EICAS message Annunciator with amber line through glideslope mode annunciator on Captain and First Officer PFD (Primary Flight Display). When fluctuating ILS indications displayed; autopilot was disconnected and ILS indications returned to normal and stabilized approach completed.Aircraft had descended to approximately 2300-2400 FT MSL prior to [FGTRE] fix which has a 2700 FT glideslope intercept altitude. ATC did not query our altitude. After landing; Left IRS fault EICAS message displayed. Autopilot EICAS message and fluctuating ILS indication and Left IRS fault entered in [the logbook] after gate arrival.I think the degraded condition with the engaged Autopilot in the Approach mode caused the aircraft to descend below glide path. Reinforces the importance of monitoring the automation and flight path to verify the aircraft is performing to the level of automation selected.

Callback: Reporter stated that another aircraft had landed before they did; and that aircraft had exited the runway farther down the runway than the reporter's aircraft did. The reporter speculated that the previous aircraft might have disrupted the glideslope by being near to the glideslope transmitter when the incident occurred. He stated that no more information was available to augment his report.

Second narrative: Aircraft intercepted glideslope and began descending. Shortly after GS intercept; Autopilot EICAS message with aural warning; and amber line through GS on FMA. Glideslope indication disappeared completely and then reappeared at top of indicator. Disconnected Autopilot and leveled off.


Synopsis: B767 flight crew reported that the aircraft descended below GS intercept altitude; EICAS message indicated a glideslope problem; the autopilot was disconnected; and a stabilized approach was completed manually. After landing; an IRS EICAS message was received.