Date: 201201
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: IMC
Light: Daylight
Aircraft: Beechjet 400
Operator: Corporate
Operating under: Part 91
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Thrust Reverser Control
Component problem: Malfunctioning
Reporter organization: Corporate
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Weather / Turbulence
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; General Declared Emergency
Contributing factors: Aircraft; Weather
Primary problem: Aircraft

Narrative: The SIC was the pilot flying and the PIC was the pilot not flying. Upon arrival into the airport terminal area; the ATIS report indicated the ceiling to be 200 FT overcast and 1/2 mile visibility; below forecast but still above minimums. Weather at the alternate airport was also checked and was reported to above approach minimums. Approach Control began vectoring the aircraft for the ILS 22. Upon localizer course intercept; ATC advised that the weather had deteriorated to 200 ft overcast and RVR 2;000 FT. Conditions were still above applicable approach minimums of RVR 1;800 FT so the aircraft continued inbound. Approximately 4 miles from the final approach fix; ATC turned the aircraft off the localizer due to loss of traffic separation and advised that the aircraft was now number three for the airport. Due to the lower than expected conditions and the possibility of a missed approach; the PIC re-checked the weather and discovered that the filed alternate had fallen below minimums. Reports were unavailable at other nearby airports due to the aircraft's low altitude and poor reception. During the process of being re-vectored for the approach; the right side thrust reverser 'unlock' light illuminated; accompanied by the master warning flasher. The PIC immediately pushed the 'stow' switch and the SIC began to slow the aircraft. The emergency checklist was completed and it was determined that the reverser appeared to be secure. The aircraft was re-vectored onto final and cleared for the approach approximately 12 miles from the airport. Both of the preceding aircraft had landed safely. Prior to the final approach fix; ATC indicated that the weather was now 200 FT and RVR 1;600 FT'. Because the conditions at the airport and the neighboring airports were now below minimums; and because the aircraft was disabled; the PIC determined that it was necessary to declare an emergency and continue for landing. Although the fuel supply was sufficient for a possible diversion (approximately 1.5 hours remaining); the crew was concerned about further worsening of the conditions in the area and felt the best option was to get the aircraft safely on the ground. ATC was advised of the situation and cleared the aircraft for landing. The procedure was flown to minimums; at which time the approach lights became visible. The pilot flying continued to 100 FT; where the runway threshold was identified and the aircraft was landed without incidence.


Second narrative: Initial weather report going into the airport was 200 FT ceiling and 1/2 mile visibility. On approach we were re-sequenced for slower traffic ahead and the visibility had gone down to 2;000 RVR. During this time we checked our alternate; which had dropped below minimums. Before being turned back for the approach we got a thrust reverser unlock and master warning light. The Captain pushed the emergency stow button and we followed the checklist. A couple of miles outside of the final approach fix we were informed that the visibility had gone to 1;600 RVR. With weather degrading in the surrounding areas; and the thrust reverser unlock light on we didn't want to get to an alternate and be low on fuel. The Captain declared an emergency and we shot the approach and landed without any further problems.


Synopsis: BE400 flight crew reports landing with RVR below published minimums after declaring an emergency due to a reverser unlock light and deteriorating weather in the area.