Cessna 340/340A
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Commercial
Flight Crew Last 90 Days 16.25; Flight Crew Total 727; Flight Crew Type 125.1
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Overcame Equipment Problem
Aircraft
Was enroute at 23;000 ft MSL over Kansas when I started to feel strange. I looked at the pressure differential and it was I think at cabin pressure of 10;000 ft. I was at 23;000 ft for a little over an hour when the controller thought I was getting hypoxic and had me descend to 10;000 feet MSL. In the descent I put on supplemental oxygen from an oxygen tank on board with a mask. At 10;000 feet I felt normal again and continued the flight at 10;000 ft. I have never been to altitude chamber that was recommended to me but now I agree that was a terrific suggestion. I checked the pressurization system and it is not working correctly and am getting it repaired. I think the controller was well trained to realize hypoxia conditions and was correct in having me descend to a level that doesn't require supplemental oxygen. I now know what hypoxic conditions fell like and will be more aware on other flights.
C340 pilot reported a pressurization failure resulting in a hypoxic condition.