Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew Landed As Precaution; Flight Crew Overcame Equipment Problem
Aircraft
At FL270; approximately one hour after takeoff; flying in icing conditions with wing and engine anti-ice systems selected 'ON'; the right pneumatic duct overheated and the right pressure regulating shutoff valve closed. Followed QRH procedures and opened the isolation valve per the checklist. Approximately 30 minutes later; the left pressure regulating shutoff valve automatically closed; leaving the aircraft with no pneumatic air supply. Attempted to restore the left side pneumatic air supply per the QRH but was not successful. Immediately [notified] ATC while simultaneously starting the APU and both pilots donning oxygen masks. Requested to descend out of icing conditions and get the cabin altitude below 10;000 feet. No more icing conditions after descending below FL190. After descending below 17;000 feet; the aircraft started re-pressurizing with the APU pneumatic system. Aircraft was being stored for over one year in the high desert in Southern California. Aircraft parts fail at a higher rate when placed in adverse weather conditions after being stored for such a long period of time.Very difficult to prevent this type of event when the aircraft is stored for such a long period of time.
B757-200 Captain reported a pneumatic duct overheat and a pneumatic shutoff valve closed; leaving the aircraft with no pneumatic air. Flight diverted to a nearby suitable airport.