A320 flight crew is issued a low altitude alert by tower during approach to dca.

Attributes
ACN	560812
Time
Date	200209
Day	Sat
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dca.airport
State Reference	DC
Altitude	msl single value : 780
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dca.tower
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : cfi pilot : atp
Experience	flight time last 90 days : 210 flight time total : 15000 flight time type : 2000
ASRS Report	560812
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	non adherence : published procedure
Independent Detector	other controllerb
Resolutory Action	controller : issued advisory
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

On a visual approach into dca, ZDC river visual runway 19. Just prior to key bridge (1/2 mi) instead of leveling off at 900 ft MSL I slowly drifted to approximately 780 ft MSL. First officer recognized the altitude at 820 ft and called it out. I leveled at approximately 780 ft. We were on visual approach over the potomac river. On the visual approach chart there is a 'recommended' altitude of 900 ft MSL at the 3 mi distance by the key bridge over the river. I was flying visually in the correct position on speed over the river. Maybe 5 seconds after noticing my altitude and leveling, the tower called us for a low altitude warning. I immediately climbed to 900 ft. During this entire time I was over the river, in control of the aircraft and in my opinion no where near any obstacles. I'm still not clear as to why I was called from tower for a low altitude alert. If tower wants us to be at 900 ft at the 3 mi river visual approach reference point, it should be listed as a minimum altitude, not a recommended altitude on the approach chart!

Original NASA ASRS Text

Title: A320 FLC IS ISSUED A LOW ALT ALERT BY TWR DURING APCH TO DCA.

Narrative: ON A VISUAL APCH INTO DCA, ZDC RIVER VISUAL RWY 19. JUST PRIOR TO KEY BRIDGE (1/2 MI) INSTEAD OF LEVELING OFF AT 900 FT MSL I SLOWLY DRIFTED TO APPROX 780 FT MSL. FO RECOGNIZED THE ALT AT 820 FT AND CALLED IT OUT. I LEVELED AT APPROX 780 FT. WE WERE ON VISUAL APCH OVER THE POTOMAC RIVER. ON THE VISUAL APCH CHART THERE IS A 'RECOMMENDED' ALT OF 900 FT MSL AT THE 3 MI DISTANCE BY THE KEY BRIDGE OVER THE RIVER. I WAS FLYING VISUALLY IN THE CORRECT POS ON SPD OVER THE RIVER. MAYBE 5 SECONDS AFTER NOTICING MY ALT AND LEVELING, THE TWR CALLED US FOR A LOW ALT WARNING. I IMMEDIATELY CLBED TO 900 FT. DURING THIS ENTIRE TIME I WAS OVER THE RIVER, IN CTL OF THE ACFT AND IN MY OPINION NO WHERE NEAR ANY OBSTACLES. I'M STILL NOT CLR AS TO WHY I WAS CALLED FROM TWR FOR A LOW ALT ALERT. IF TWR WANTS US TO BE AT 900 FT AT THE 3 MI RIVER VISUAL APCH REF POINT, IT SHOULD BE LISTED AS A MINIMUM ALT, NOT A RECOMMENDED ALT ON THE APCH CHART!

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.