Date: 201210
Local time of day: 1801-2400
Location: CVG.Airport, KY
Flight conditions: IMC
Light: Night
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Initial Approach
Airspace: Class B CVG
ATC / advisory: TRACON CVG
Aircraft component: Radio Altimeter
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Commercial
Human factors: Situational Awareness; Training / Qualification
Second reporter function: Pilot Not Flying; Captain
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Executed Go Around / Missed Approach; Flight Crew Took Evasive Action; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: We were being vectored for the ILS 36C at CVG while in night IMC conditions. The aircraft was level at 3;000 FT; heading of 270. ATC advised us to slow to 180 KTS or slower. I retarded the thrust levers; and at around 230 KTS; the Gear Horn sounded. At the same time; the GPWS annunciated 'Terrain; Terrain; Pull Up.' I brought the power forward; and immediately both indications disappeared. We determined that this must have been a malfunction; so we attempted to decelerate to meet the ATC instruction. Once slowing below 200 KTS; the Gear Horn sounded again. ATC gave us a turn to join the localizer; and then cleared us for the approach. As we captured the localizer; the glideslope became unreliable. When the aircraft received the glideslope; the aircraft was not yet in a position to intercept the glideslope. However; the autopilot captured the glideslope; and climbed to intercept it. At this point; we received the GPWS 'Terrain' alert again. The Captain called for a go-around. We alerted ATC that we were going around due to inability to receive the glideslope; and were given vectors for 36L. After the go-around; we reconfigured for the ILS 36L. From this point on; we received no further alerts regarding the Gear Horn; or from the GWPS. We landed on 36L without incident.The event occurred due to a malfunction of the GPWS. We noticed that the left side RA was showing erratic indications while the alerts were present. It is likely that this inaccurate information led to the false alerts. These alerts created a serious distraction; which hindered my ability to hear and communicate with my Captain. My Captain did a great job of evaluating the indications; and in the execution of the go-around. Despite the distractions; he stayed focused on the procedure of the go-around; and his control of the situation made my job significantly easier.


Second narrative: In level unaccelerated flight at 4;000 FT ATC asked that we slow from 230 KIAS to 170 KIAS while joining the ILS to 36C. As the First Officer retarded the thrust levers; the gear horn sounded; the First Officer then advanced the thrust levers slightly and the gear horn ceased. Almost simultaneously; we were given a descending turn and cleared the ILS 36C approach; the gear horn sounded again; GPWS 'terrain; terrain pull up' aural and visual alerts activated. Captain's radar altimeter was erratic. We crossed checked all flight instruments and knew we had leveled off. All warnings ceased and the localizer and glideslope were captured normally. The glideslope was then lost and a go around was initiated by the Captain. We notified ATC of the faulty/unusable glideslope and were directed to climb to 4;000 FT and turn to a heading of 270. The crew executed the go around in accordance with all company policies and procedures. We then executed the ILS 36L approach without further abnormal indications and in a timely manner. After parking at the gate the Captain notified Maintenance Control via cell phone and wrote the occurrence up in the aircraft maintenance forms. Since we were IMC a go around should have been initiated approximately 1 minute earlier even though all flight instruments agreed the aircraft was in level flight at a safe altitude.


Synopsis: CRJ200 flight crew experiences gear and GPWS warnings during vectors for an ILS approach in night IMC. The warnings are initially ignored due to indications that the Captain's radar atimeter is erratic. When the glideslope appears unstable the crew elects to go around and use a different ILS approach.