A B737-200 flight crew descended 300 ft below assigned altitude on descent to dal.

Attributes
ACN	449900
Time
Date	199909
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dal.airport
State Reference	TX
Altitude	msl bound lower : 4700 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : d10.tracon
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer only : 31r
Flight Phase	descent : intermediate altitude
Route In Use	approach : instrument non precision
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : multi engine pilot : instrument pilot : atp
Experience	flight time last 90 days : 151 flight time total : 9300 flight time type : 4200
ASRS Report	449900
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft departed austin bergstrom airport at XA15 on sep/xa/99 for dallas love field in VMC. On descent into dallas, regional approach control directed the aircraft to intercept the runway 31R localizer and descend to 5000 ft MSL. During descent (on the localizer) the captain directed the flight attendants to secure the cabin for arrival on interphone. The '1000 ft to go' company altitude call was given and acknowledged passing 6000 ft. At approximately 5300 ft MSL the captain was observed decreasing rate of descent for leveloff. The copilot then positioned the aircraft's transparent windshield sunscreen to dampen the setting sun glare, then noticed the altitude passing approximately 4800 ft and notified the captain of the 5000 ft altitude required altitude. The captain responded by immediate climb back to 5000 ft. Approach control almost simultaneously cleared the aircraft to 4000 ft and a subsequent visual approach to runway 31R. There was no air traffic collision, avoidance potential nor was there any TCASII traffic proximity indication. However, altitude deviated from that assigned by approximately 300 ft. This was the second flight of the day of the last day of a 4 day pairing. The 4 day trip had included excellent crew coordination, however, this was the first flight in an aircraft without automatic altitude leveloff capability in autoplt operation. Possibly this difference and performance of other cockpit actions during critical leveloff led to this discrepancy.

Original NASA ASRS Text

Title: A B737-200 FLC DSNDED 300 FT BELOW ASSIGNED ALT ON DSCNT TO DAL.

Narrative: ACFT DEPARTED AUSTIN BERGSTROM ARPT AT XA15 ON SEP/XA/99 FOR DALLAS LOVE FIELD IN VMC. ON DSCNT INTO DALLAS, REGIONAL APCH CTL DIRECTED THE ACFT TO INTERCEPT THE RWY 31R LOC AND DSND TO 5000 FT MSL. DURING DSCNT (ON THE LOC) THE CAPT DIRECTED THE FLT ATTENDANTS TO SECURE THE CABIN FOR ARR ON INTERPHONE. THE '1000 FT TO GO' COMPANY ALT CALL WAS GIVEN AND ACKNOWLEDGED PASSING 6000 FT. AT APPROX 5300 FT MSL THE CAPT WAS OBSERVED DECREASING RATE OF DSCNT FOR LEVELOFF. THE COPLT THEN POSITIONED THE ACFT'S TRANSPARENT WINDSHIELD SUNSCREEN TO DAMPEN THE SETTING SUN GLARE, THEN NOTICED THE ALT PASSING APPROX 4800 FT AND NOTIFIED THE CAPT OF THE 5000 FT ALT REQUIRED ALT. THE CAPT RESPONDED BY IMMEDIATE CLB BACK TO 5000 FT. APCH CTL ALMOST SIMULTANEOUSLY CLRED THE ACFT TO 4000 FT AND A SUBSEQUENT VISUAL APCH TO RWY 31R. THERE WAS NO AIR TFC COLLISION, AVOIDANCE POTENTIAL NOR WAS THERE ANY TCASII TFC PROX INDICATION. HOWEVER, ALT DEVIATED FROM THAT ASSIGNED BY APPROX 300 FT. THIS WAS THE SECOND FLT OF THE DAY OF THE LAST DAY OF A 4 DAY PAIRING. THE 4 DAY TRIP HAD INCLUDED EXCELLENT CREW COORD, HOWEVER, THIS WAS THE FIRST FLT IN AN ACFT WITHOUT AUTOMATIC ALT LEVELOFF CAPABILITY IN AUTOPLT OP. POSSIBLY THIS DIFFERENCE AND PERFORMANCE OF OTHER COCKPIT ACTIONS DURING CRITICAL LEVELOFF LED TO THIS DISCREPANCY.

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.