Narrative:

After we had started our initial descent and I increased the rate of descent slightly; I heard a 'thump' or 'snap' followed by an extreme sensation of cabin climb (my ears). It took me a second or two to assess what was happening while the cabin masks were deploying and I was trying to interpretation the 'cabin rate' needle; which was pegged to the right (strange looking because I had flown other planes with a normal indication to the right; so it took me a second; even though physically I knew what was happening. It was about this time that I started to feel 'funny' and 'warm.' it then all came to me about what exactly was going on and what I had to do (I guess it was at this time that my training took over). I then immediately tried to don my mask; and it wouldn't fit over my headset. I just held to my face with my right hand and flew the airplane with my left and continued breathing while notifying ATC I needed lower (I was already in a fast descent); and that we had a pressurization failure. I think initially he cleared me to FL190. I insisted lower and he asked if I was declaring an emergency. I replied 'affirmative' and he cleared me to (I think) 6000 ft. We descended; returned to ZZZ safely. Upon notifying maintenance and some inspecting they discovered that the air-to-ground squat switch linkage had been removed from its mount (disconnected) to perform system testing on the ground and had failed to reconnect it. I failed to catch it on my preflight. Apparently it was positioned in such a way as to allow the aircraft to pressurize on takeoff; but must have moved to the 'on-the-ground position' when I began my descent; and dumped the cabin because it thought we were on the ground.

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Original NASA ASRS Text

Title: KINGAIR BE200 PLT HAS PRESSURIZATION LOSS; DECLARES AN EMER AND LANDS.

Narrative: AFTER WE HAD STARTED OUR INITIAL DSCNT AND I INCREASED THE RATE OF DSCNT SLIGHTLY; I HEARD A 'THUMP' OR 'SNAP' FOLLOWED BY AN EXTREME SENSATION OF CABIN CLB (MY EARS). IT TOOK ME A SECOND OR TWO TO ASSESS WHAT WAS HAPPENING WHILE THE CABIN MASKS WERE DEPLOYING AND I WAS TRYING TO INTERP THE 'CABIN RATE' NEEDLE; WHICH WAS PEGGED TO THE R (STRANGE LOOKING BECAUSE I HAD FLOWN OTHER PLANES WITH A NORMAL INDICATION TO THE R; SO IT TOOK ME A SECOND; EVEN THOUGH PHYSICALLY I KNEW WHAT WAS HAPPENING. IT WAS ABOUT THIS TIME THAT I STARTED TO FEEL 'FUNNY' AND 'WARM.' IT THEN ALL CAME TO ME ABOUT WHAT EXACTLY WAS GOING ON AND WHAT I HAD TO DO (I GUESS IT WAS AT THIS TIME THAT MY TRAINING TOOK OVER). I THEN IMMEDIATELY TRIED TO DON MY MASK; AND IT WOULDN'T FIT OVER MY HEADSET. I JUST HELD TO MY FACE WITH MY R HAND AND FLEW THE AIRPLANE WITH MY L AND CONTINUED BREATHING WHILE NOTIFYING ATC I NEEDED LOWER (I WAS ALREADY IN A FAST DSCNT); AND THAT WE HAD A PRESSURIZATION FAILURE. I THINK INITIALLY HE CLRED ME TO FL190. I INSISTED LOWER AND HE ASKED IF I WAS DECLARING AN EMER. I REPLIED 'AFFIRMATIVE' AND HE CLRED ME TO (I THINK) 6000 FT. WE DSNDED; RETURNED TO ZZZ SAFELY. UPON NOTIFYING MAINT AND SOME INSPECTING THEY DISCOVERED THAT THE AIR-TO-GND SQUAT SWITCH LINKAGE HAD BEEN REMOVED FROM ITS MOUNT (DISCONNECTED) TO PERFORM SYS TESTING ON THE GND AND HAD FAILED TO RECONNECT IT. I FAILED TO CATCH IT ON MY PREFLT. APPARENTLY IT WAS POSITIONED IN SUCH A WAY AS TO ALLOW THE ACFT TO PRESSURIZE ON TKOF; BUT MUST HAVE MOVED TO THE 'ON-THE-GND POS' WHEN I BEGAN MY DSCNT; AND DUMPED THE CABIN BECAUSE IT THOUGHT WE WERE ON THE GND.

Data retrieved from NASA's ASRS site as of January 2009 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.