A B737-200 descending into bwi misunderstands the cleared altitude and descends to cruise 1000 ft lo...

Attributes
ACN	398957
Time
Date	199804
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : bwi
State Reference	MD
Altitude	msl bound lower : 4000 msl bound upper : 5000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bwi
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other descent other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 23000 flight time type : 17000
ASRS Report	398957
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 8000 flight time type : 2400
ASRS Report	399490
Events
Anomaly	altitude deviation : overshoot inflight encounter : weather non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier flight bhm-bwi. During arrival we had deviated for WX and were being vectored to a downwind for runway 10 at bwi. Approach control cleared us to 5000 ft. I read back 4000 ft. PF and FAA air carrier operations inspector (bhm office) both confirmed 4000 ft. After we had been at 4000 ft for approximately 1-2 mins, controller asked me what our altitude was. When I told him 4000 ft, he said that we had been cleared to 5000 ft, but to stay at 4000 ft, no conflict. Landed without incident. Supplemental information from acn 399490: the captain read back 4000 ft and I descended to 4000 ft. The initial call was a little garbled and we both read back 4000 ft. We also had an FAA inspector on the jumpseat who also heard us read back 4000 ft. The controller did not correct us until we had been at 4000 ft for a min or so.

Original NASA ASRS Text

Title: A B737-200 DSNDING INTO BWI MISUNDERSTANDS THE CLRED ALT AND DSNDS TO CRUISE 1000 FT LOWER THAN ASSIGNED.

Narrative: ACR FLT BHM-BWI. DURING ARR WE HAD DEVIATED FOR WX AND WERE BEING VECTORED TO A DOWNWIND FOR RWY 10 AT BWI. APCH CTL CLRED US TO 5000 FT. I READ BACK 4000 FT. PF AND FAA ACR OPS INSPECTOR (BHM OFFICE) BOTH CONFIRMED 4000 FT. AFTER WE HAD BEEN AT 4000 FT FOR APPROX 1-2 MINS, CTLR ASKED ME WHAT OUR ALT WAS. WHEN I TOLD HIM 4000 FT, HE SAID THAT WE HAD BEEN CLRED TO 5000 FT, BUT TO STAY AT 4000 FT, NO CONFLICT. LANDED WITHOUT INCIDENT. SUPPLEMENTAL INFO FROM ACN 399490: THE CAPT READ BACK 4000 FT AND I DSNDED TO 4000 FT. THE INITIAL CALL WAS A LITTLE GARBLED AND WE BOTH READ BACK 4000 FT. WE ALSO HAD AN FAA INSPECTOR ON THE JUMPSEAT WHO ALSO HEARD US READ BACK 4000 FT. THE CTLR DID NOT CORRECT US UNTIL WE HAD BEEN AT 4000 FT FOR A MIN OR SO.

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.

A B737-200 descending into bwi misunderstands the cleared altitude and descends to cruise 1000 ft lower than assigned.