C210 pilot attributes radio tuning error to hypoxia.

Attributes
ACN	654855
Time
Date	200504
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : cew.vortac
State Reference	FL
Altitude	msl single value : 15000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu.artcc artcc : zjx.artcc
Operator	general aviation : personal
Make Model Name	Cessna 210 Centurion / Turbo Centurion 210C 210D
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : commercial pilot : instrument
Experience	flight time last 90 days : 41 flight time total : 905 flight time type : 225
ASRS Report	654855
Person 2
Affiliation	government : faa
Function	controller : radar
Events
Anomaly	non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Supplementary
Problem Areas	Environmental Factor Flight Crew Human Performance
Primary Problem	Environmental Factor

Narrative:

I had been flying at 15000 ft MSL almost all day. As I neared the end of my second 3 1/2 hour leg; someone on the ZHU frequency mentioned that they had needed to get in touch with an aircraft and that they had used 121.5 to do so. Hearing this reminded me that I should monitor 121.5 when able. I promptly tuned #2 to 121.5 and put it on speaker. Center frequency was quiet for 5 mins or so; and I checked my chart to see whose sector I was in. Then I realized I'd missed a handoff because I'd changed the wrong radio. Contacted jax immediately and was greeted normally; so I suppose I wasn't off houston for long. The incident scared me a little and made me think of hypoxia. I'd had a headache and felt fatigued for much of the flight. I checked my oxygen supply -- all looked normal. Still; I turned up the flow. Upon getting more oxygen; my head soon felt better. In fact; I felt much better overall. I'll watch for these symptoms more closely in the future.

Original NASA ASRS Text

Title: C210 PLT ATTRIBUTES RADIO TUNING ERROR TO HYPOXIA.

Narrative: I HAD BEEN FLYING AT 15000 FT MSL ALMOST ALL DAY. AS I NEARED THE END OF MY SECOND 3 1/2 HR LEG; SOMEONE ON THE ZHU FREQ MENTIONED THAT THEY HAD NEEDED TO GET IN TOUCH WITH AN ACFT AND THAT THEY HAD USED 121.5 TO DO SO. HEARING THIS REMINDED ME THAT I SHOULD MONITOR 121.5 WHEN ABLE. I PROMPTLY TUNED #2 TO 121.5 AND PUT IT ON SPEAKER. CTR FREQ WAS QUIET FOR 5 MINS OR SO; AND I CHKED MY CHART TO SEE WHOSE SECTOR I WAS IN. THEN I REALIZED I'D MISSED A HDOF BECAUSE I'D CHANGED THE WRONG RADIO. CONTACTED JAX IMMEDIATELY AND WAS GREETED NORMALLY; SO I SUPPOSE I WASN'T OFF HOUSTON FOR LONG. THE INCIDENT SCARED ME A LITTLE AND MADE ME THINK OF HYPOXIA. I'D HAD A HEADACHE AND FELT FATIGUED FOR MUCH OF THE FLT. I CHKED MY OXYGEN SUPPLY -- ALL LOOKED NORMAL. STILL; I TURNED UP THE FLOW. UPON GETTING MORE OXYGEN; MY HEAD SOON FELT BETTER. IN FACT; I FELT MUCH BETTER OVERALL. I'LL WATCH FOR THESE SYMPTOMS MORE CLOSELY IN THE FUTURE.

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.