|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||0601 To 1200|
|Locale Reference||airport : zzz.airport|
|Altitude||msl bound lower : 20000|
msl bound upper : 21000
|Controlling Facilities||artcc : zzz.artcc|
tracon : cmh.tracon
|Operator||general aviation : corporate|
|Make Model Name||Cessna 310/T310C|
|Operating Under FAR Part||Part 91|
|Flight Phase||cruise : level|
|Affiliation||company : corporate|
|Function||flight crew : single pilot|
|Qualification||pilot : atp|
pilot : cfi
|Experience||flight time last 90 days : 41|
flight time total : 2662
flight time type : 1240
|Anomaly||aircraft equipment problem : critical|
altitude deviation : overshoot
inflight encounter other
non adherence : clearance
|Independent Detector||other flight crewa|
|Resolutory Action||flight crew : overcame equipment problem|
|Problem Areas||Flight Crew Human Performance|
We were flying aerial photo flight lines in a C310 at FL200. Because of the nature of aerial photo work we were on a block clearance from FL200 through FL210. After about 2 hours in-flight; I realized that I was short of breath. After checking flow rate and hook-ups; I found that the re-breather bag on my mask had fallen off. It had apparently been held on with some tape and moisture had softened the adhesive. I got the bag back on; but continued to feel a little shaky; but couldn't immediately identify any other hypoxia symptoms. Not long after we were near the end of the flight; and I elected to end the flight a few mins early. I did not report the mask problem. I asked ATC to arrange clrncs down to our destination and released the autoplt to descend to the lower end of our altitude block. On reaching FL200; I pushed the button to re-engage the altitude hold; but apparently double tapped it because it didn't fully engage. About 30 seconds alter; I looked at altitude and was approximately 400 ft low. I immediately corrected; but not before setting off alarms at center. I had failed to verify that the autoplt engaged; and was then slow to monitor altitude. Subsequently; during my descent; I was cleared down to 15000 ft but registered 14000 ft in my head. I later found out that tapes showed I did read back 15000 ft. ATC corrected me approximately 700 ft low. Even after landing; I continued to feel a little shaky. While that could have been emotion driven; I really believe that I continued to suffer the effects of hypoxia. I had inspected the mask prior to flight and everything seemed secure; but it clearly needed a positive attachment such as a wire tie (there is a retention bead on the end). The wire tie has been added. Overall conclusion is that oxygen masks in unpressurized GA aircraft need the same level of inspection and maintenance as all other portions of the aircraft. Additionally; adhesive tape should never be used as a primary method of securing anything -- especially where moisture is present.
Original NASA ASRS Text
Title: FLYING HIS UNPRESSURIZED C310 AT BLOCK ALTS OF FL200 TO 210; SINGLE PLT DISCOVERS HIS OXYGEN REBREATHER BAG HAD FALLEN OFF ALLOWING O2 TO DETOUR PRIOR TO INHALING. NOTICES MODEST HYPOXIC SYMPTOMS BUT CONTINUES HIS MISSION PRIOR TO DESCENDING AFTER REATTACHING THE BAG. SEVERAL VERTICAL TRACK ERRORS ON DESCENT CAUSE HIM TO RETHINK THE LEVEL OF DETERIORATION OF HIS FLT SKILLS.
Narrative: WE WERE FLYING AERIAL PHOTO FLT LINES IN A C310 AT FL200. BECAUSE OF THE NATURE OF AERIAL PHOTO WORK WE WERE ON A BLOCK CLRNC FROM FL200 THROUGH FL210. AFTER ABOUT 2 HRS INFLT; I REALIZED THAT I WAS SHORT OF BREATH. AFTER CHKING FLOW RATE AND HOOK-UPS; I FOUND THAT THE RE-BREATHER BAG ON MY MASK HAD FALLEN OFF. IT HAD APPARENTLY BEEN HELD ON WITH SOME TAPE AND MOISTURE HAD SOFTENED THE ADHESIVE. I GOT THE BAG BACK ON; BUT CONTINUED TO FEEL A LITTLE SHAKY; BUT COULDN'T IMMEDIATELY IDENT ANY OTHER HYPOXIA SYMPTOMS. NOT LONG AFTER WE WERE NEAR THE END OF THE FLT; AND I ELECTED TO END THE FLT A FEW MINS EARLY. I DID NOT RPT THE MASK PROB. I ASKED ATC TO ARRANGE CLRNCS DOWN TO OUR DEST AND RELEASED THE AUTOPLT TO DSND TO THE LOWER END OF OUR ALT BLOCK. ON REACHING FL200; I PUSHED THE BUTTON TO RE-ENGAGE THE ALT HOLD; BUT APPARENTLY DOUBLE TAPPED IT BECAUSE IT DIDN'T FULLY ENGAGE. ABOUT 30 SECONDS ALTER; I LOOKED AT ALT AND WAS APPROX 400 FT LOW. I IMMEDIATELY CORRECTED; BUT NOT BEFORE SETTING OFF ALARMS AT CTR. I HAD FAILED TO VERIFY THAT THE AUTOPLT ENGAGED; AND WAS THEN SLOW TO MONITOR ALT. SUBSEQUENTLY; DURING MY DSCNT; I WAS CLRED DOWN TO 15000 FT BUT REGISTERED 14000 FT IN MY HEAD. I LATER FOUND OUT THAT TAPES SHOWED I DID READ BACK 15000 FT. ATC CORRECTED ME APPROX 700 FT LOW. EVEN AFTER LNDG; I CONTINUED TO FEEL A LITTLE SHAKY. WHILE THAT COULD HAVE BEEN EMOTION DRIVEN; I REALLY BELIEVE THAT I CONTINUED TO SUFFER THE EFFECTS OF HYPOXIA. I HAD INSPECTED THE MASK PRIOR TO FLT AND EVERYTHING SEEMED SECURE; BUT IT CLEARLY NEEDED A POSITIVE ATTACHMENT SUCH AS A WIRE TIE (THERE IS A RETENTION BEAD ON THE END). THE WIRE TIE HAS BEEN ADDED. OVERALL CONCLUSION IS THAT OXYGEN MASKS IN UNPRESSURIZED GA ACFT NEED THE SAME LEVEL OF INSPECTION AND MAINT AS ALL OTHER PORTIONS OF THE ACFT. ADDITIONALLY; ADHESIVE TAPE SHOULD NEVER BE USED AS A PRIMARY METHOD OF SECURING ANYTHING -- ESPECIALLY WHERE MOISTURE IS PRESENT.
Data retrieved from NASA's ASRS site as of May 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.