B757-200
Confusion; Distraction; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance
Flight Crew Diverted; General Declared Emergency; General Maintenance Action
Aircraft
In cruise flight at FL350 the aircraft warning system showed the following indications: Master Warning light; red CONFIG light; red flaps light and the aural warning siren. The warning siren could not be silenced except when throttles were in idle which made intra-cockpit and ATC communications extremely difficult. Decision was made to divert and declare an emergency. During the descent when the throttles were retarded to idle; the warning siren stopped. Approach and landing were uneventful. There were no known deviations from ATC clearances or operational procedures. We may have been able to continue to our original destination if the warning siren could have been silenced easily. In our situation; dark night and over water; it seemed unsafe and intolerable to continue in cruise flight with the constant blare of the siren in our ears. When a malfunction causes the airplane to think it is on the ground when in flight and the Takeoff Configuration Warning siren comes on; the distraction level in the cockpit is extremely high which could lead to any number of pilot errors. Recommend providing the pilots with a way to silence the siren when necessary.
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A B757-200 air/ground switch failed in cruise and because of the Master Warning light with a Warning Horn; the red CONFIG and FLAPS lights; an emergency was declared and the flight diverted.