Small aircraft has altitude deviation on descent, discovers oxygen connection has disconnected.

Attributes
ACN	295246
Time
Date	199501
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lar
State Reference	WY
Altitude	msl bound lower : 11500 msl bound upper : 12000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : private
Experience	flight time last 90 days : 14 flight time total : 1058 flight time type : 435
ASRS Report	295246
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot non adherence : far non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance flight crew : overcame equipment problem other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

On flight from twf to fnl on IFR flight plan on descent I was cleared down to 12000 ft, the controller called for an altitude check as I was passing 11500 ft and they cleared me on down to 11000 ft. I was having a problem with the RNAV set up to go to colln NDB, not that there was a problem with the equipment but I was confused. It was then that I discovered that my oxygen supply hose had come off at the aircraft end connector. I had been at 15000 ft in cruise for about 2 hour 30 min at that time and I don't know how long I had been without oxygen supply, but I recall being very nervous or agitated about 30 mins prior to this event . After I got the oxygen restored just a few mins the feeling and confusion was corrected.

Original NASA ASRS Text

Title: SMA HAS ALTDEV ON DSCNT, DISCOVERS OXYGEN CONNECTION HAS DISCONNECTED.

Narrative: ON FLT FROM TWF TO FNL ON IFR FLT PLAN ON DSCNT I WAS CLRED DOWN TO 12000 FT, THE CTLR CALLED FOR AN ALT CHK AS I WAS PASSING 11500 FT AND THEY CLRED ME ON DOWN TO 11000 FT. I WAS HAVING A PROB WITH THE RNAV SET UP TO GO TO COLLN NDB, NOT THAT THERE WAS A PROB WITH THE EQUIP BUT I WAS CONFUSED. IT WAS THEN THAT I DISCOVERED THAT MY OXYGEN SUPPLY HOSE HAD COME OFF AT THE ACFT END CONNECTOR. I HAD BEEN AT 15000 FT IN CRUISE FOR ABOUT 2 HR 30 MIN AT THAT TIME AND I DON'T KNOW HOW LONG I HAD BEEN WITHOUT OXYGEN SUPPLY, BUT I RECALL BEING VERY NERVOUS OR AGITATED ABOUT 30 MINS PRIOR TO THIS EVENT . AFTER I GOT THE OXYGEN RESTORED JUST A FEW MINS THE FEELING AND CONFUSION WAS CORRECTED.

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.