Date: 201210
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Dawn
Aircraft: Beech 1900
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Landing
ATC / advisory: Tower ZZZ
Aircraft component: Pressurization Control System
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: General Maintenance Action
Contributing factors: Aircraft; Manuals; Procedure
Primary problem: Aircraft

Narrative: The airplane had come out of maintenance and this was its first flight since being released. The mechanics had worked on the pressurization system as part of their scheduled maintenance. During our climb out we noticed that the cabin altitude was indicating below our departure airport elevation with the cabin at max differential. In cruise we observed normal indications. During descent; I set the pressurization correctly to [the airport elevation] and we observed a 1;000 FPM descent all the way during the descent with the cabin remaining at max differential and the cabin altitude went well below zero (approximately 3;000 feet below zero). On final we felt the pressure change and I tried to adjust the rate controller to stop the cabin descent. Since the altitude was way below sea level; I began dumping the cabin (small bursts while on final approach) in an attempt to equalize the pressure for [the airport]. Once we landed the cabin VSI indicated a climb pegged at 6;000 FPM and the pressure equalized. The cabin climbed approximately 9;000 feet in a second which caused extreme discomfort in our ears (we were screaming in agony rolling down the runway). At the gate several passengers complained about the pressurization system as they were deplaning. I instructed the First Officer to go to the new airplane since we were swapping and I contacted Maintenance regarding the pressurization. We had a non-reving pilot riding on board who suggested that we call in sick due to the large change in pressure citing possible issues associated with the decompression (similar to those that a diver might experience) and issues with our ears. When I arrived at the new airplane; I made my suggestion known to the First Officer and called us both in sick as a precaution. The company asked us to go to a doctor who told us not to fly for 24 hours as a precaution.  This event concerned me in a few ways. First: the airplane had come out of maintenance that morning with work being done on the pressurization system. It was apparent to us once airborne that the pressurization system was not acting normally. The system did test properly on the ground during our run up checks. Second: there is no checklist guidance for an airplane that is slow to pressurize; or one that remains pressurized while on the descent. The only checklist guidance is for a cabin altitude high and a cabin differential high. In the case of this flight; neither occurred. The closest would have been cabin differential high but we had no annunciators for that and the gauge was showing max differential; not anything higher. When we noticed the cabin remaining at max differential on the descent and the cabin descending below sea level; it would have been nice to reference something telling us how to remedy the situation. Pressurization problems like this are becoming increasingly common on our fleet.




Synopsis: B1900 flight crew experienced a loss of the cabin pressurization controller and rapid pressure changes resulting in extreme ear discomfort. Flight crew noted a lack of checklist guidance for the problem they encountered.