Narrative:

I was doing high altitude glider flying in a mountain wave. Through pre-agreement with leesburg, va, FSS, the pre- designated window was open to 23000 ft. During the flight, the hose supplying oxygen became disconnected from the mask. As it took me a while to realize this, I did not pay close enough attention to time and started my descent later than I should have, and landed approximately 20 mins after sunset at grant county airport. I feel that this was caused by 2 things. One being the tube slipping off the mask and two: my not viewing that portion of the mask as a distinct connection. The mask -- one no. X high concentration see-through adult oxygen mask, patent no. Y. The clear plastic oxygen delivery tube is attached to the mask by sliding over a plastic nipple. At first glance, it appears to have been glued or sealed on. If the tube is tugged on without twisting, there is a bit of resistance. However, if the tube is slightly twisted on the nipple, the tube easily slides right off. Although the directions imply that the mask INS intended for medical use, it is distributed in a clear plastic bag marked aviation oxygen on a label. Since this mask uses a connection that appears sealed but easily can slip off, this mask should be prohibited from being used in aviation flight by pilots. Connection should be more robust. This mask may be ok if a lip on the nipple and clamp over the hose were used. This hose connects to the nipple at a location on the mask below the wearer's mouth which is also out of sight from the person's view. The pilot -- for oxygen system, we are taught price -- to check pressure, regulator, indicator, connections, emergency bail out bottle. As the pilot, I failed to check the tube where it joined onto the nipple of the mask as being a connection. I erroneously saw it as a sealed connection and did not check it as frequently as I should have.

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Original NASA ASRS Text

Title: A SAILPLANE PLT SUFFERED HYPOXIA WHICH CONTRIBUTED TO HIS LNDG AFTER DARK.

Narrative: I WAS DOING HIGH ALT GLIDER FLYING IN A MOUNTAIN WAVE. THROUGH PRE-AGREEMENT WITH LEESBURG, VA, FSS, THE PRE- DESIGNATED WINDOW WAS OPEN TO 23000 FT. DURING THE FLT, THE HOSE SUPPLYING OXYGEN BECAME DISCONNECTED FROM THE MASK. AS IT TOOK ME A WHILE TO REALIZE THIS, I DID NOT PAY CLOSE ENOUGH ATTN TO TIME AND STARTED MY DSCNT LATER THAN I SHOULD HAVE, AND LANDED APPROX 20 MINS AFTER SUNSET AT GRANT COUNTY ARPT. I FEEL THAT THIS WAS CAUSED BY 2 THINGS. ONE BEING THE TUBE SLIPPING OFF THE MASK AND TWO: MY NOT VIEWING THAT PORTION OF THE MASK AS A DISTINCT CONNECTION. THE MASK -- ONE NO. X HIGH CONCENTRATION SEE-THROUGH ADULT OXYGEN MASK, PATENT NO. Y. THE CLR PLASTIC OXYGEN DELIVERY TUBE IS ATTACHED TO THE MASK BY SLIDING OVER A PLASTIC NIPPLE. AT FIRST GLANCE, IT APPEARS TO HAVE BEEN GLUED OR SEALED ON. IF THE TUBE IS TUGGED ON WITHOUT TWISTING, THERE IS A BIT OF RESISTANCE. HOWEVER, IF THE TUBE IS SLIGHTLY TWISTED ON THE NIPPLE, THE TUBE EASILY SLIDES RIGHT OFF. ALTHOUGH THE DIRECTIONS IMPLY THAT THE MASK INS INTENDED FOR MEDICAL USE, IT IS DISTRIBUTED IN A CLR PLASTIC BAG MARKED AVIATION OXYGEN ON A LABEL. SINCE THIS MASK USES A CONNECTION THAT APPEARS SEALED BUT EASILY CAN SLIP OFF, THIS MASK SHOULD BE PROHIBITED FROM BEING USED IN AVIATION FLT BY PLTS. CONNECTION SHOULD BE MORE ROBUST. THIS MASK MAY BE OK IF A LIP ON THE NIPPLE AND CLAMP OVER THE HOSE WERE USED. THIS HOSE CONNECTS TO THE NIPPLE AT A LOCATION ON THE MASK BELOW THE WEARER'S MOUTH WHICH IS ALSO OUT OF SIGHT FROM THE PERSON'S VIEW. THE PLT -- FOR OXYGEN SYS, WE ARE TAUGHT PRICE -- TO CHK PRESSURE, REGULATOR, INDICATOR, CONNECTIONS, EMER BAIL OUT BOTTLE. AS THE PLT, I FAILED TO CHK THE TUBE WHERE IT JOINED ONTO THE NIPPLE OF THE MASK AS BEING A CONNECTION. I ERRONEOUSLY SAW IT AS A SEALED CONNECTION AND DID NOT CHK IT AS FREQUENTLY AS I SHOULD HAVE.

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.