<< >> NASA ASRS Report 520420, July 2001

An A320 flight crew inadvertently descended 250 ft lower than assigned altitude due to incorrect altimeter setting.

Attributes
ACN	520420
Time
Date	200107
Day	Tue
Local Time Of Day	0001 To 0600
Place
Locale Reference	intersection : bucko
State Reference	WV
Altitude	msl bound lower : 32750 msl bound upper : 33000
Environment
Light	Night
Aircraft 1
Controlling Facilities	artcc : zob.artcc
Operator	common carrier : air carrier
Make Model Name	A320
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 191
ASRS Report	520420
Events
Anomaly	altitude deviation : overshoot altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Resolutory Action	flight crew : returned to assigned altitude flight crew : overrode automation flight crew : overcame equipment problem
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

Descending from FL390 to FL330, I preset local iad altimeter 30.31 and inadvertently failed to return the altimeter setting to standard 29.92. The aircraft was on autoplt #2 at the time. Upon leveling at FL330, the captain noticed the discrepancy between his correct instruments set to 29.92 and the autoplt leveling at an altitude based on 30.31 hg. When he pointed it out, I immediately reset the knob to standard and read FL327.5 on the altimeter. I disconnected the autoplt and expedited a climb back to FL330. The flight continued without further incident. No other aircraft were affected by this temporary deviation and no discussion ensued with ATC.

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Original NASA ASRS Text

Title: AN A320 FLT CREW INADVERTENTLY DSNDED 250 FT LOWER THAN ASSIGNED ALT DUE TO INCORRECT ALTIMETER SETTING.

Narrative: DSNDING FROM FL390 TO FL330, I PRESET LCL IAD ALTIMETER 30.31 AND INADVERTENTLY FAILED TO RETURN THE ALTIMETER SETTING TO STANDARD 29.92. THE ACFT WAS ON AUTOPLT #2 AT THE TIME. UPON LEVELING AT FL330, THE CAPT NOTICED THE DISCREPANCY BTWN HIS CORRECT INSTS SET TO 29.92 AND THE AUTOPLT LEVELING AT AN ALT BASED ON 30.31 HG. WHEN HE POINTED IT OUT, I IMMEDIATELY RESET THE KNOB TO STANDARD AND READ FL327.5 ON THE ALTIMETER. I DISCONNECTED THE AUTOPLT AND EXPEDITED A CLB BACK TO FL330. THE FLT CONTINUED WITHOUT FURTHER INCIDENT. NO OTHER ACFT WERE AFFECTED BY THIS TEMPORARY DEV AND NO DISCUSSION ENSUED WITH ATC.

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.