Beech 1900
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Human Factors
The aircraft had overnighted due to it not being able to pressurize. We had a Mechanic with us who worked on the aircraft. He was unable to fix it; so he did MEL 21-9. My First Officer then did a standard walk around; and noted no discrepancies. We then flew the aircraft unpressurized per the MEL. After bringing the aircraft to the hangar; the mechanics found the problem to be a missing outer window on one of the emergency exits. As stated earlier my First Officer noted no discrepancies on his walk around. The mechanics have said its possible the window had a bad seal and fell out in flight.
BE1900 reports ferrying an aircraft that will not pressurize to a maintenance base; where it is discovered that the outer window of one of the emergency exits is missing.