Flight crew levels on wrong altimeter setting.

Attributes
ACN	317080
Time
Date	199509
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lvz
State Reference	PA
Altitude	msl bound lower : 23500 msl bound upper : 24000
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zny
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 13000 flight time type : 3000
ASRS Report	317080
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Level at 26000 ft, descent to 24000 ft, level off, controller asked are we level? Reported yes at 24000 ft, controller reported us at 23500 ft. We changed xponders and realized the captain's altimeter was set at qnh. Neither pilot remembers switching from sta to qnh. I can only think that when I acknowledged the clearance that I pressed the qnh button. I have no reason for doing so. I pass it off on being very tired. I discussed it with the first officer and this is all we could figure out. All system in the aircraft function normal and nothing was ever detected wrong. The controller said it was no problem and continue descent to 20000 ft. We both took a deep breath and continued without any more problems.

Original NASA ASRS Text

Title: FLC LEVELS ON WRONG ALTIMETER SETTING.

Narrative: LEVEL AT 26000 FT, DSCNT TO 24000 FT, LEVEL OFF, CTLR ASKED ARE WE LEVEL? RPTED YES AT 24000 FT, CTLR RPTED US AT 23500 FT. WE CHANGED XPONDERS AND REALIZED THE CAPT'S ALTIMETER WAS SET AT QNH. NEITHER PLT REMEMBERS SWITCHING FROM STA TO QNH. I CAN ONLY THINK THAT WHEN I ACKNOWLEDGED THE CLRNC THAT I PRESSED THE QNH BUTTON. I HAVE NO REASON FOR DOING SO. I PASS IT OFF ON BEING VERY TIRED. I DISCUSSED IT WITH THE FO AND THIS IS ALL WE COULD FIGURE OUT. ALL SYS IN THE ACFT FUNCTION NORMAL AND NOTHING WAS EVER DETECTED WRONG. THE CTLR SAID IT WAS NO PROB AND CONTINUE DSCNT TO 20000 FT. WE BOTH TOOK A DEEP BREATH AND CONTINUED WITHOUT ANY MORE PROBS.

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.