Pilot of an small transport jet deviated from assigned altitude and heading due to hypoxia.

Attributes
ACN	363795
Time
Date	199703
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : vuz
State Reference	AL
Altitude	msl bound lower : 25000 msl bound upper : 35000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Flight Phase	cruise other
Route In Use	enroute airway : ztl
Flight Plan	IFR
Person 1
Affiliation	government : military
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 25 flight time total : 5100 flight time type : 57
ASRS Report	363795
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other other spatial deviation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance controller : provided flight assist flight crew : exited adverse environment other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Pilot became hypoxic, deviated from altitude and heading. After descent from FL350 to FL250, pilot performance improved and flight continued to tyndall AFB without further difficulty. Center may have suspected hypoxia and descended pilot for this reason. ZTL was very helpful. Hypoxia was due to poor mask fit and lack of positive pressure in mask. Mask has been replaced and regulator has been replaced. Pilot has undergone high altitude chamber training and physiological training since this event.

Original NASA ASRS Text

Title: PLT OF AN SMT JET DEVIATED FROM ASSIGNED ALT AND HDG DUE TO HYPOXIA.

Narrative: PLT BECAME HYPOXIC, DEVIATED FROM ALT AND HDG. AFTER DSCNT FROM FL350 TO FL250, PLT PERFORMANCE IMPROVED AND FLT CONTINUED TO TYNDALL AFB WITHOUT FURTHER DIFFICULTY. CTR MAY HAVE SUSPECTED HYPOXIA AND DSNDED PLT FOR THIS REASON. ZTL WAS VERY HELPFUL. HYPOXIA WAS DUE TO POOR MASK FIT AND LACK OF POSITIVE PRESSURE IN MASK. MASK HAS BEEN REPLACED AND REGULATOR HAS BEEN REPLACED. PLT HAS UNDERGONE HIGH ALT CHAMBER TRAINING AND PHYSIOLOGICAL TRAINING SINCE THIS EVENT.

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.