LEAR 35 PRESSURIZATION CONTROL FAILED. FLT CREW DECLARED EMER; APCH AND LNDG COMPLETED UNEVENTFULLY.

Narrative

NIGHT VMC ON AN IFR FLT PLAN; WITH 8 PAX ON BOARD. WE WERE AT 13000 FT MSL ON THE ARR INTO ZZZ WHEN THE CABIN PRESSURIZATION FAILED IN THE AUTO MODE AND ALLOWED THE CABIN PRESSURE TO DROP; ACTIVATING THE EMER PRESSURIZATION. WE COMPLIED WITH THE APPROPRIATE CHKLIST AND REQUESTED A LOWER ALT. WE NOTIFIED APCH THAT WE WOULD BE UNABLE TO COMPLY WITH THE ARR ALTS AND NEEDED A REROUTE TO AVOID MOUNTAINOUS TERRAIN. APCH WAS UNABLE TO REROUTE US; THUS WE EXERCISED COMMAND AUTH AND DECLARED AN EMER; AND ASKED FOR DIRECT TO ZZZ ARPT. AT THAT TIME THE ARPT WAS IN SIGHT; AND WE WERE CLRED DOWN TO 10000 FT. THE CABIN PRESSURE STABILIZED AT THE LOWER ALT AND A LNDG WAS MADE VISUALLY WITHOUT FURTHER INCIDENT. THE INABILITY TO RECEIVE AN IMMEDIATE REROUTE FROM ZZZ CTLRS PROMPTED THE DECLARATION OF AN EMER IN ORDER TO DEVIATE FROM THE STAR RESTRS FOR ALT CLRNC OVER MOUNTAINOUS TERRAIN AT NIGHT. (AS INFO; THIS ARR ROUTING IS OVER MOUNTAINOUS TERRAIN; WHERE OUR CURRENT DIRECT ROUTING AT THAT TIME WAS DIRECT TO THE ARPT AND NOT OVER MOUNTAINOUS TERRAIN.)