Narrative:

While on an IFR flight, just east of the lake hughes VOR at FL240 in IMC, the pilot started having difficulty flying the aircraft. I was along as a passenger in the right seat and was reading a book. I looked up to see the aircraft 400' low, in a left 30 degree bank and off course. I asked the pilot if he was ok and he replied that he was dizzy. He looked disoriented and did not seem able to recover his assigned altitude or course. He then said that his arms and legs were numb. I suggested that he call ZLA and start descending. He attempted to call center but did not reach for the microphone; rather, he pushed on the yoke push-to-talk switch and spoke into his (non-microphone equipped) O2 mask. He then started to check his O2 mask, at which time I reached over for the microphone and called ZLA and told them that we needed to descend immediately. They advised that we could expect a descent clearance in some # of mi. I declared an emergency and restated that we needed to descend immediately to 14000'. ATC then cleared us to descend to FL220. I started an emergency descent and again advised ATC that I was declaring an emergency due to an O2 system failure and was descending immediately to 14000'. I'm not sure ATC understood what I was saying since another voice on the frequency had to also tell ATC that we had declared an emergency, when he again questioned my declaration. During this descent I did not know what the O2 system failure was, or if I merely had a better response to anoxia. While descending through FL210, we noted that the pilot's O2 mask had separated from its feed hose. Upon correction, the pilot immediately recovered and we cancelled our emergency descent. The pilot was able to continue the flight uneventfully at FL200.

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Original NASA ASRS Text

Title: GA SMA DECLARED AN EMERGENCY WHEN THE PLT STARTED TO LOSE CONSCIOUSNESS AFTER HIS O2 HOSE CAME LOOSE FROM HIS O2 MASK.

Narrative: WHILE ON AN IFR FLT, JUST E OF THE LAKE HUGHES VOR AT FL240 IN IMC, THE PLT STARTED HAVING DIFFICULTY FLYING THE ACFT. I WAS ALONG AS A PAX IN THE RIGHT SEAT AND WAS READING A BOOK. I LOOKED UP TO SEE THE ACFT 400' LOW, IN A LEFT 30 DEG BANK AND OFF COURSE. I ASKED THE PLT IF HE WAS OK AND HE REPLIED THAT HE WAS DIZZY. HE LOOKED DISORIENTED AND DID NOT SEEM ABLE TO RECOVER HIS ASSIGNED ALT OR COURSE. HE THEN SAID THAT HIS ARMS AND LEGS WERE NUMB. I SUGGESTED THAT HE CALL ZLA AND START DSNDING. HE ATTEMPTED TO CALL CENTER BUT DID NOT REACH FOR THE MIC; RATHER, HE PUSHED ON THE YOKE PUSH-TO-TALK SWITCH AND SPOKE INTO HIS (NON-MIC EQUIPPED) O2 MASK. HE THEN STARTED TO CHK HIS O2 MASK, AT WHICH TIME I REACHED OVER FOR THE MIC AND CALLED ZLA AND TOLD THEM THAT WE NEEDED TO DSND IMMEDIATELY. THEY ADVISED THAT WE COULD EXPECT A DSNT CLRNC IN SOME # OF MI. I DECLARED AN EMER AND RESTATED THAT WE NEEDED TO DSND IMMEDIATELY TO 14000'. ATC THEN CLRED US TO DSND TO FL220. I STARTED AN EMER DSNT AND AGAIN ADVISED ATC THAT I WAS DECLARING AN EMER DUE TO AN O2 SYS FAILURE AND WAS DSNDING IMMEDIATELY TO 14000'. I'M NOT SURE ATC UNDERSTOOD WHAT I WAS SAYING SINCE ANOTHER VOICE ON THE FREQ HAD TO ALSO TELL ATC THAT WE HAD DECLARED AN EMER, WHEN HE AGAIN QUESTIONED MY DECLARATION. DURING THIS DSNT I DID NOT KNOW WHAT THE O2 SYS FAILURE WAS, OR IF I MERELY HAD A BETTER RESPONSE TO ANOXIA. WHILE DSNDING THROUGH FL210, WE NOTED THAT THE PLT'S O2 MASK HAD SEPARATED FROM ITS FEED HOSE. UPON CORRECTION, THE PLT IMMEDIATELY RECOVERED AND WE CANCELLED OUR EMER DSNT. THE PLT WAS ABLE TO CONTINUE THE FLT UNEVENTFULLY AT FL200.

Data retrieved from NASA's ASRS site as of July 2007 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.