An S80 overshot its assigned altitude when the altitude alerter is not set to the correct altitude.

Attributes
ACN	415160
Time
Date	199809
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : lga
State Reference	NY
Altitude	msl bound lower : 6750 msl bound upper : 7000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90
Operator	common carrier : air carrier
Make Model Name	MD-80 Super 80
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	415160
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
ASRS Report	415161
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Lga 225 degree radial, 20 DME. We were given a clearance to descend and maintain 7000 ft. The first officer set the altitude in and I confirmed it. Passing through 6800 ft, the first officer noted that the altitude arm window was now set at 8000 ft. I stopped the descent. We did not descend 300 ft below 7000 ft but we came close.

Original NASA ASRS Text

Title: AN S80 OVERSHOT ITS ASSIGNED ALT WHEN THE ALT ALERTER IS NOT SET TO THE CORRECT ALT.

Narrative: LGA 225 DEG RADIAL, 20 DME. WE WERE GIVEN A CLRNC TO DSND AND MAINTAIN 7000 FT. THE FO SET THE ALT IN AND I CONFIRMED IT. PASSING THROUGH 6800 FT, THE FO NOTED THAT THE ALT ARM WINDOW WAS NOW SET AT 8000 FT. I STOPPED THE DSCNT. WE DID NOT DSND 300 FT BELOW 7000 FT BUT WE CAME CLOSE.

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.