Date: 201406
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: Marginal
Weather elements / visibility: Turbulence
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Landing
ATC / advisory: Tower ZZZ
Aircraft component: System Monitor: Indicating and Warning
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Human-Machine Interface; Situational Awareness; Troubleshooting; Communication Breakdown
Second reporter function: Pilot Flying; Check Pilot
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Other / Unknown; Inflight Event / Encounter Unstabilized Approach; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution
Contributing factors: Weather; Aircraft; Human Factors
Primary problem: Aircraft

Narrative: I was the pilot monitoring for the approach. The Captain/pilot flying (PF) had the autopilot and autothrottles engaged and had intercepted the ILS. At approximately 1;500 feet we were visual with the runway so the Captain disengaged the Autopilot; however he was unable to get the Master Warning or Autopilot Disconnect aural siren to stop. He then reconnected the autopilot and unsuccessfully tried again to disconnect the autopilot; however the master Warning and Disconnect Siren would not stop. I also unsuccessfully tried my disconnect switch. At approximately 1;000 AGL; the PF was getting high on the glideslope so I stated to him that he was 'high; fast and the 600 FPM rate of descent was not adequate.'  He did not make any correction nor did he acknowledge me. I then said again; 'Captain; did you hear me!' He stated that he did hear me and then initiated a correction. However; at approximately 600-700 AGL we were still approximately 145 KTS which was approximately 20K above planned approach speed (Vref was 117 + 5K Additive). He stated that he was fast and at 500 feet he intended to go around. At 500 feet we were approximately 15 knots above approach speed......I then called '500 feet; unstable.' He then said 'landing' and continued to land the airplane. It is of my observation that the approach was unstable at 500 feet by approximately 15 KTS fast. A go-around may have been more appropriate than landing the aircraft. However; given the distraction and hindrance to communications between PF and PM from the autopilot Siren; and the fact that there were thunderstorms 7NM off the departure end of the runway; we landed the aircraft.


Second narrative: We further slowed then to about 150-160K. By this time; I believe we were still prior to the FAF. Then; I called for Flaps 25; and finally Flaps 30. Looking to slow to the Vapp; 124K. The checklists were all completed. However; we were above the glideslope (GS) somewhere around here as I visually had picked up the field and runway. I elected to click off the autopilot and at this point the autopilot warning horn started blaring very loudly as I had attempted numerous times to silence it with the yoke disconnect button. I always try and state to the first officer; 'autopilot disconnected' when it's quiet with no warning horn sounding with that double click to do so. He had tried as well with his yoke button with ZERO success. I remember saying 'This doesn't seem to be working out; go-around' around 700 feet AFE. When we did get to just passing the 500 feet AFE; the First Officer said; 'I think it's best that we land.' I quickly reconsidered his plea and had said 'Landing' after it was apparent that the Vapp speed was down to around 130 KIAS. However; we now got below the GS and the PAPI was red/red. The airspeed seemed to actually be dropping even with the autothrottles connected. I cobbed the power a handful and shoved up the throttles to level it out some being that we had a red PAPI; etc... The wind had shifted from about 240 degrees direction to 030 degrees surface winds at about 10-15 KTS. The VSI seemed to never have exceeded 1;000 FPM for the most part during the 5-700 feet AFE and down to the touch down portion of this unstabilized approach and landing. We finally landed successfully and the landing touchdown part was quite normal.


Synopsis: While shooting an ILS approach in stormy weather the flight crew of a B757-200 was distracted by the autopilot disconnect siren that failed to silence after disengaging the autopilot. The approach became unstable but; after considering a go-around; they elected to land due to the distractions of the still blaring siren and the presence of thunderstorms in the area.