Narrative:

During climb out I as the pilot in command was sitting right seat and performing copilot duties running checklists and radios; with nothing abnormal noted. Passing through FL200; while talking on radio; I felt in my ears pressure building and instantly the cabin altitude light and horn activated. We confirmed pressurization needle pegged. We performed emergency memory items descending immediately to 15;000 ft negating need to don masks; while I coordinated with ATC our required immediate descent. After completing checklist; I reengaged APU and its pressurization. You could feel it in your ears; but the cabin would not pressurize. At the first opportunity the passengers were notified all was okay and of our plan to safely divert to [nearest suitable airport]. I then balanced time changing flight plan and checklists with ATC and coordinating with company operations. Upon uneventful landing my first officer and I assisted passengers in moving them and their belongings to a standby aircraft. We did the required post flight and write ups for maintenance. After consulting with company operations and assistant chief pilot; it was determined the most efficient recovery for our passengers was for my first officer and I to continue on in the second aircraft. As a crew we discussed our capability on continuing; and decided we could indeed safely continue as aircrew on the second aircraft.

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Original NASA ASRS Text

Title: An HS125-800XP Captain reported loss of pressurization climbing through FL200. A rapid descent and diversion to nearest suitable ensued.

Narrative: During climb out I as the Pilot in Command was sitting right seat and performing copilot duties running checklists and radios; with nothing abnormal noted. Passing through FL200; while talking on radio; I felt in my ears pressure building and instantly the Cabin Altitude light and Horn Activated. We confirmed pressurization needle pegged. We performed emergency memory items descending immediately to 15;000 FT negating need to don masks; while I coordinated with ATC our required immediate descent. After completing checklist; I reengaged APU and its pressurization. You could feel it in your ears; but the cabin would not pressurize. At the first opportunity the passengers were notified all was okay and of our plan to safely divert to [nearest suitable airport]. I then balanced time changing flight plan and checklists with ATC and coordinating with Company Operations. Upon uneventful landing my First Officer and I assisted passengers in moving them and their belongings to a standby aircraft. We did the required post flight and write ups for Maintenance. After consulting with Company Operations and Assistant Chief Pilot; it was determined the most efficient recovery for our passengers was for my First Officer and I to continue on in the second aircraft. As a crew we discussed our capability on continuing; and decided we could indeed safely continue as aircrew on the second aircraft.

Data retrieved from NASA's ASRS site as of April 2012 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.