B737-800 crew descended below the minimum altitude outside the FAF on runway 31 at lga.

Attributes
ACN	533012
Time
Date	200112
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : jfk.airport
State Reference	NY
Altitude	msl bound lower : 900 msl bound upper : 1600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : lga.tower
Operator	common carrier : air carrier
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer only : 31
Flight Phase	descent : approach
Route In Use	approach : instrument non precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 250 flight time total : 8000
ASRS Report	533012
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude altitude deviation : overshoot non adherence : company policies non adherence : far non adherence : published procedure other anomaly other other spatial deviation
Independent Detector	atc equipment : msaw other controllera other flight crewa other flight crewb
Resolutory Action	controller : issued alert flight crew : returned to assigned altitude none taken : detected after the fact
Supplementary
Problem Areas	Flight Crew Human Performance Company
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Setting up for the localizer runway 31 approach into lga, clearance was given to intercept final approach course, maintain 1600 ft till established. Before altitude capture had begun, captain spun MDA, 600 ft in the autoplt altitude window. Aircraft continued below 1600 ft. Air crew noticed discrepancy at 900 ft and corrected back to 1600 ft until final approach procedure. Tower advised crew that they had received a low altitude warning.

Original NASA ASRS Text

Title: B737-800 CREW DSNDED BELOW THE MINIMUM ALT OUTSIDE THE FAF ON RWY 31 AT LGA.

Narrative: SETTING UP FOR THE LOC RWY 31 APCH INTO LGA, CLRNC WAS GIVEN TO INTERCEPT FINAL APCH COURSE, MAINTAIN 1600 FT TILL ESTABLISHED. BEFORE ALT CAPTURE HAD BEGUN, CAPT SPUN MDA, 600 FT IN THE AUTOPLT ALT WINDOW. ACFT CONTINUED BELOW 1600 FT. AIR CREW NOTICED DISCREPANCY AT 900 FT AND CORRECTED BACK TO 1600 FT UNTIL FINAL APCH PROC. TWR ADVISED CREW THAT THEY HAD RECEIVED A LOW ALT WARNING.

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.