Narrative:

Departure airport was 1.5 visibility in 1300 ft RVR. Destination airport was reporting 3500 ft sct 10 miles visibility. Approximately 25 min into flight at cruise FL350 the right thrust reverser 'trans' annunciator illuminated with the corresponding horn. Immediate action of the crew was activation of the 'emergency stow' switch. Crew then followed the appropriate emergency checklist and made a precautionary landing at ZZZ1. A safe landing was made with no incident. On the post flight inspection performed by the crew determined that the right hand thrust reverser did in fact become unlatched. A company mechanic was dispatched to inspect and repair the faulty thrust reverser. On inspection by the mechanic, it was determined that a mounting screw for the latching solenoid was not tightened properly. The aircraft was in maintenance the prior day. During that time the thrust reverser system was worked on. The thrust reversers were bolted shut for the return flight back to ZZZ1. A ferry permit was obtained for that flight. The ferry flight was made uneventfully back to ZZZ1. Callback conversation with reporter revealed the following information: the reporter stated the warning system has an amber light when the thrust reverser is unlatched and transiting accompanied by a warning horn. When in full reverse a green light is illuminated. The reporter indicated they received the amber light with the warning horn sounding and immediately hit the restow switch which operated. Post flight inspection indicated the reverser was unlatched. When the company technician arrived and inspected the thrust reverser, it was found that the latching solenoid mounting bolts were not tightened. The airplane was in maintenance the day before the flight and the thrust reverser was worked. Reverser was locked in the forward thrust position and maintenance ferried aircraft to home base.

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Original NASA ASRS Text

Title: A FALCON 10 IN CRUISE AT FL350 DECLARED AN EMER AND DIVERTED DUE TO R THRUST REVERSER TRANSITING WARNING LIGHT ON AND WARNING HORN SOUNDING. CREW IMMEDIATELY ACTIVATED EMER STOW.

Narrative: DEPARTURE ARPT WAS 1.5 VIS IN 1300 FT RVR. DEST ARPT WAS RPTING 3500 FT SCT 10 MILES VIS. APPROX 25 MIN INTO FLT AT CRUISE FL350 THE R THRUST REVERSER 'TRANS' ANNUNCIATOR ILLUMINATED WITH THE CORRESPONDING HORN. IMMEDIATE ACTION OF THE CREW WAS ACTIVATION OF THE 'EMER STOW' SWITCH. CREW THEN FOLLOWED THE APPROPRIATE EMER CHKLIST AND MADE A PRECAUTIONARY LNDG AT ZZZ1. A SAFE LNDG WAS MADE WITH NO INCIDENT. ON THE POST FLT INSPECTION PERFORMED BY THE CREW DETERMINED THAT THE R HAND THRUST REVERSER DID IN FACT BECOME UNLATCHED. A COMPANY MECHANIC WAS DISPATCHED TO INSPECT AND REPAIR THE FAULTY THRUST REVERSER. ON INSPECTION BY THE MECHANIC, IT WAS DETERMINED THAT A MOUNTING SCREW FOR THE LATCHING SOLENOID WAS NOT TIGHTENED PROPERLY. THE ACFT WAS IN MAINT THE PRIOR DAY. DURING THAT TIME THE THRUST REVERSER SYSTEM WAS WORKED ON. THE THRUST REVERSERS WERE BOLTED SHUT FOR THE RETURN FLT BACK TO ZZZ1. A FERRY PERMIT WAS OBTAINED FOR THAT FLT. THE FERRY FLT WAS MADE UNEVENTFULLY BACK TO ZZZ1. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE WARNING SYSTEM HAS AN AMBER LIGHT WHEN THE THRUST REVERSER IS UNLATCHED AND TRANSITING ACCOMPANIED BY A WARNING HORN. WHEN IN FULL REVERSE A GREEN LIGHT IS ILLUMINATED. THE RPTR INDICATED THEY RECEIVED THE AMBER LIGHT WITH THE WARNING HORN SOUNDING AND IMMEDIATELY HIT THE RESTOW SWITCH WHICH OPERATED. POST FLT INSPECTION INDICATED THE REVERSER WAS UNLATCHED. WHEN THE COMPANY TECHNICIAN ARRIVED AND INSPECTED THE THRUST REVERSER, IT WAS FOUND THAT THE LATCHING SOLENOID MOUNTING BOLTS WERE NOT TIGHTENED. THE AIRPLANE WAS IN MAINT THE DAY BEFORE THE FLT AND THE THRUST REVERSER WAS WORKED. REVERSER WAS LOCKED IN THE FORWARD THRUST POSITION AND MAINT FERRIED ACFT TO HOME BASE.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.