A BE300 super king air, descended below assigned altitude as it approachs tpa, fl.

Attributes
ACN	381853
Time
Date	199710
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : tpa
State Reference	FL
Altitude	msl bound lower : 4300 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : tpa
Operator	other
Make Model Name	Super King Air 300
Operating Under FAR Part	Part 91
Flight Phase	descent other
Route In Use	approach : visual enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 80 flight time total : 12600 flight time type : 500
ASRS Report	381853
Person 2
Affiliation	government other
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 90 flight time total : 10000 flight time type : 300
ASRS Report	381960
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Descending for a visual approach to runway 36L at tpa, was reaching 4300 ft MSL when ATC advised traffic at 12 O'clock position, 5 mi at 4000 ft. I advised first officer to confirm with ATC that we were cleared to 4000 ft (altitude alerter had been set for 4000 ft and first officer confirmed he thought we had been cleared to 4000 ft). ATC advised we were cleared to 5000 ft. We climb immediately back to 5000 ft. When on ground called TRACON and talk to watch supervisor. I stated we had thought we were cleared to 4000 ft and the first officer set altitude alerter to 4000 ft. He confirmed tape verified our clearance to 5000 ft and we acknowledged 5000 ft. I had been listening to ATIS when the clearance was given and assumed the first officer was correctly setting the assigned altitude. We broke the chain of checks when I was listening to ATIS and the first officer was talking to ATC. This negated a reason for having 2 pilots. I learned that in the future don't assume the other pilot is correctly providing critical flight information and confirm assigned altitudes when you did not actually hear them assigned. Supplemental information from acn 381960: during letdown was cleared to descend to 5000 ft but erroneously entered 4000 ft in altitude alerter. Captain descended to 4300 ft when advisory of traffic at 4000 ft caused crew to question our assigned altitude. Questioned ATC which advised 5000 ft. Aircraft immediately was climbed from 4300 ft to 5000 ft. Must constantly guard against human error and crew must xchk each other.

Original NASA ASRS Text

Title: A BE300 SUPER KING AIR, DSNDED BELOW ASSIGNED ALT AS IT APCHS TPA, FL.

Narrative: DSNDING FOR A VISUAL APCH TO RWY 36L AT TPA, WAS REACHING 4300 FT MSL WHEN ATC ADVISED TFC AT 12 O'CLOCK POS, 5 MI AT 4000 FT. I ADVISED FO TO CONFIRM WITH ATC THAT WE WERE CLRED TO 4000 FT (ALT ALERTER HAD BEEN SET FOR 4000 FT AND FO CONFIRMED HE THOUGHT WE HAD BEEN CLRED TO 4000 FT). ATC ADVISED WE WERE CLRED TO 5000 FT. WE CLB IMMEDIATELY BACK TO 5000 FT. WHEN ON GND CALLED TRACON AND TALK TO WATCH SUPVR. I STATED WE HAD THOUGHT WE WERE CLRED TO 4000 FT AND THE FO SET ALT ALERTER TO 4000 FT. HE CONFIRMED TAPE VERIFIED OUR CLRNC TO 5000 FT AND WE ACKNOWLEDGED 5000 FT. I HAD BEEN LISTENING TO ATIS WHEN THE CLRNC WAS GIVEN AND ASSUMED THE FO WAS CORRECTLY SETTING THE ASSIGNED ALT. WE BROKE THE CHAIN OF CHKS WHEN I WAS LISTENING TO ATIS AND THE FO WAS TALKING TO ATC. THIS NEGATED A REASON FOR HAVING 2 PLTS. I LEARNED THAT IN THE FUTURE DON'T ASSUME THE OTHER PLT IS CORRECTLY PROVIDING CRITICAL FLT INFO AND CONFIRM ASSIGNED ALTS WHEN YOU DID NOT ACTUALLY HEAR THEM ASSIGNED. SUPPLEMENTAL INFO FROM ACN 381960: DURING LETDOWN WAS CLRED TO DSND TO 5000 FT BUT ERRONEOUSLY ENTERED 4000 FT IN ALT ALERTER. CAPT DSNDED TO 4300 FT WHEN ADVISORY OF TFC AT 4000 FT CAUSED CREW TO QUESTION OUR ASSIGNED ALT. QUESTIONED ATC WHICH ADVISED 5000 FT. ACFT IMMEDIATELY WAS CLBED FROM 4300 FT TO 5000 FT. MUST CONSTANTLY GUARD AGAINST HUMAN ERROR AND CREW MUST XCHK EACH OTHER.

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.