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DHC6 flight crew during a VFR flight encounters WX; climbs to avoid IMC and exceeds altitude for use of crew oxygen.
| Attributes | |
| ACN | 695177 |
| Time | |
| Date | 200604 |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | atc facility : zab.artcc |
| State Reference | NM |
| Altitude | msl bound lower : 14000 msl bound upper : 15000 |
| Environment | |
| Flight Conditions | VMC |
| Weather Elements | Turbulence |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zab.artcc |
| Operator | general aviation : personal |
| Make Model Name | Twin Otter DHC-6-300 |
| Operating Under FAR Part | Part 91 |
| Flight Phase | cruise : level |
| Flight Plan | None |
| Person 1 | |
| Affiliation | other |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : instrument pilot : commercial pilot : cfi pilot : atp pilot : multi engine |
| Experience | flight time last 90 days : 90 flight time total : 4000 flight time type : 1600 |
| ASRS Report | 695177 |
| Person 2 | |
| Affiliation | other |
| Function | flight crew : first officer |
| Events | |
| Anomaly | inflight encounter : vfr in imc non adherence : far |
| Independent Detector | other flight crewa |
| Resolutory Action | none taken : anomaly accepted |
| Supplementary | |
| Problem Areas | Weather Flight Crew Human Performance |
| Primary Problem | Flight Crew Human Performance |
Narrative:
While en route from north las vegas; nv; we encountered increasing cloud layers. We climbed from 11500 ft to 13500 ft MSL to transit over 1 cumulus layer I thought was a narrow band. It was not skinny; though; and it built quite rapidly. I instructed my very green sic to continue the climb to keep us VFR. I climbed us to 15000 ft or a bit more as we maneuvered to remain VFR. I kept thinking it would be for 'just another min' as visually I thought I saw VFR breaks. However; the vertical development was greater than I had judged. I had a momentary hesitation due to my copilot's inexperience with ATC; but I told her to tell ATC we needed an IFR descent (to get back to the correct altitude). They told us to stand by and they would work at getting a clearance for us. In summary; I estimate I was above the 'required oxygen for crew members' level for approximately 10 mins. We saw a large VFR corridor and made a VFR descent before center could return with a clearance. It was not a good judgement call to judge a cumulous layer on its initial appearance. I do a lot of low level flying in my different jobs; and a little voice told me not to try to hop over this innocuous-looking layer. I will listen to that voice better now.
Original NASA ASRS Text
Title: DHC6 FLT CREW DURING A VFR FLT ENCOUNTERS WX; CLBS TO AVOID IMC AND EXCEEDS ALT FOR USE OF CREW OXYGEN.
Narrative: WHILE ENRTE FROM NORTH LAS VEGAS; NV; WE ENCOUNTERED INCREASING CLOUD LAYERS. WE CLBED FROM 11500 FT TO 13500 FT MSL TO TRANSIT OVER 1 CUMULUS LAYER I THOUGHT WAS A NARROW BAND. IT WAS NOT SKINNY; THOUGH; AND IT BUILT QUITE RAPIDLY. I INSTRUCTED MY VERY GREEN SIC TO CONTINUE THE CLB TO KEEP US VFR. I CLBED US TO 15000 FT OR A BIT MORE AS WE MANEUVERED TO REMAIN VFR. I KEPT THINKING IT WOULD BE FOR 'JUST ANOTHER MIN' AS VISUALLY I THOUGHT I SAW VFR BREAKS. HOWEVER; THE VERT DEVELOPMENT WAS GREATER THAN I HAD JUDGED. I HAD A MOMENTARY HESITATION DUE TO MY COPLT'S INEXPERIENCE WITH ATC; BUT I TOLD HER TO TELL ATC WE NEEDED AN IFR DSCNT (TO GET BACK TO THE CORRECT ALT). THEY TOLD US TO STAND BY AND THEY WOULD WORK AT GETTING A CLRNC FOR US. IN SUMMARY; I ESTIMATE I WAS ABOVE THE 'REQUIRED OXYGEN FOR CREW MEMBERS' LEVEL FOR APPROX 10 MINS. WE SAW A LARGE VFR CORRIDOR AND MADE A VFR DSCNT BEFORE CTR COULD RETURN WITH A CLRNC. IT WAS NOT A GOOD JUDGEMENT CALL TO JUDGE A CUMULOUS LAYER ON ITS INITIAL APPEARANCE. I DO A LOT OF LOW LEVEL FLYING IN MY DIFFERENT JOBS; AND A LITTLE VOICE TOLD ME NOT TO TRY TO HOP OVER THIS INNOCUOUS-LOOKING LAYER. I WILL LISTEN TO THAT VOICE BETTER NOW.
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.