B737 flight crew descends below minimum altitude during lda approach to dca.

Attributes
ACN	571590
Time
Date	200301
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dca.airport
State Reference	DC
Altitude	msl bound lower : 800 msl bound upper : 1000
Environment
Flight Conditions	IMC
Weather Elements	Snow
Light	Night
Aircraft 1
Controlling Facilities	tower : dca.tower
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Navigation In Use	ils localizer only : 19 other Other
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 : atp pilot : multi engine pilot : flight engineer pilot : cfi
Experience	flight time last 90 days : 250 flight time total : 16000 flight time type : 5000
ASRS Report	571231
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : multi engine pilot : private pilot : commercial pilot : instrument
Experience	flight time last 90 days : 200 flight time total : 10500 flight time type : 5000
ASRS Report	571590
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : published procedure non adherence : clearance non adherence : far
Independent Detector	other flight crewa other flight crewb
Resolutory Action	none taken : anomaly accepted
Supplementary
Problem Areas	Flight Crew Human Performance Weather
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During approach, we possibly descended below 1000 ft slightly before 4 DME fix with specified minimum altitude of 1000 ft. Contributing factors: significantly worse WX than on ATIS from 40 mins before (ATIS 55 mi overcast 10 mi visibility). Actual WX estimated 10 mi overcast 2 sn. No WX update from approach or tower. Anticipated breaking out of clouds much earlier. Attention of pilots not to stray into P56 prohibited areas. Night and snow. Unfamiliar approach (first time for both pilots). FMS not optimized for lda approach with 41 degree turn to runway for landing.

Original NASA ASRS Text

Title: B737 FLT CREW DSNDS BELOW MINIMUM ALT DURING LDA APCH TO DCA.

Narrative: DURING APCH, WE POSSIBLY DSNDED BELOW 1000 FT SLIGHTLY BEFORE 4 DME FIX WITH SPECIFIED MINIMUM ALT OF 1000 FT. CONTRIBUTING FACTORS: SIGNIFICANTLY WORSE WX THAN ON ATIS FROM 40 MINS BEFORE (ATIS 55 MI OVCST 10 MI VISIBILITY). ACTUAL WX ESTIMATED 10 MI OVCST 2 SN. NO WX UPDATE FROM APCH OR TWR. ANTICIPATED BREAKING OUT OF CLOUDS MUCH EARLIER. ATTN OF PLTS NOT TO STRAY INTO P56 PROHIBITED AREAS. NIGHT AND SNOW. UNFAMILIAR APCH (FIRST TIME FOR BOTH PLTS). FMS NOT OPTIMIZED FOR LDA APCH WITH 41 DEG TURN TO RWY FOR LNDG.

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.