Date: 202012
Local time of day: 0601-1200
Location: ZZZZ.ARTCC, FO
Flight conditions: VMC
Aircraft: Beech 1900
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Cruise
ATC / advisory: Center ZZZZ
Aircraft component: Pressurization System
Component problem: Failed
Reporter organization: Contracted Service
Reporter function: Captain; Pilot Flying
Human factors: Troubleshooting; Time Pressure; Communication Breakdown; Distraction; Physiological - Other; Workload
Anomaly: Aircraft Equipment Problem Critical; Flight Deck / Cabin / Aircraft Event Illness / Injury
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Air Traffic Control Issued New Clearance; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Operating at FL190. After cruise checklist was completed; cabin altitude was indicating approximate 10;000 feet. After 5 to 10 minutes' elapsed; I felt a change in pressure inside the aircraft. When I crosschecked the cabin altitude climb was indicating 4;000 feet climbing; a minute later; the cabin altitude warning illuminated. This was followed by aircraft memory item and checklist. I pulled O2 knob located left upper just left of the external power switch and as I pulled the mask I placed the O2 mask on emergency mode and no oxygen was flowing. I placed it back on normal operation and nothing happened. I switched the mic to the O2 mask and advised ATC for urgent descent 10;000 feet. I discovered that ATC was unable to hear me at all.  I looked over and the switch for the microphone was placed on oxygen mask and nothing seemed to fix the problem. The cabin altitude was indicating roughly about 20;000 to 21;000 feet from what I recall. I switched again to my headset and requested '...priority; need to descend now to 10;000 feet pressurization problems.' As soon as I talked to ATC; I started immediate descent memory item and checklist; while descending; I took the First Officer mask to see for O2 flow and no O2 was flowing; I double checked the O2 handle.  I pulled both located on the Captain left hand side upper and lower; and nothing resulted for O2 function. Since I was indicating 60 miles from my departure airport; I decided to return since for my judgment it was unsafe to continue the flight without O2 flow; no O2 mask microphone and pressurization problems. Upon reaching 10;000 feet the cabin stabilized and the cabin altitude indicator was no longer illuminated with a cabin altitude about 9;000 feet.ATC gave me instructions to descend to 5;000 feet and while at it; the cabin altitude started to jump 5;500 feet up followed by a descent to 4;000 feet and this continued all the way to 3;000 feet. At that moment; I was feeling uncomfortable since my ears where hurting and I knew I was not feeling 100%. At 3;000 feet; I turned off my bleed air and flew the aircraft unpressurized. Why ? I had 'ears popping' several times at this time and I wanted to make the little time left comfortable in order to make a safe landing; since this constant climb and descend from the cabin was making me feel really weak. Landed the aircraft successfully without any major issues. After landing Maintenance and Station manager met me at the airplane.  I took  time at the crew van to see if I felt better and I did.  This resulted in a maintenance write up for 3 items.  Unable to control cabin altitude; O2 Mask Mic not operating; O2 not flowing properly.




Synopsis: BE1900 pilot reported aircraft lost pressurization; oxygen masks; and oxygen masks microphone failed during cruise resulting in a return to departure airport.