DH8 first officer descended below his clearance altitude.

Attributes
ACN	421357
Time
Date	199811
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : clt airport : clt
State Reference	NC
Altitude	msl bound lower : 6580 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : clt
Operator	common carrier : air carrier
Make Model Name	Dash 8-100
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : commercial pilot : instrument
Experience	flight time last 90 days : 250 flight time total : 3800 flight time type : 70
ASRS Report	421357
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 200 flight time total : 11250 flight time type : 250
ASRS Report	421170
Events
Anomaly	altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During radar vector for a visual approach to runway 18R at clt, cleared heading 090 degrees and down to 7000 ft. Autoplt engaged. We descended via 'FPM' vertical speed mode. This can cause overspd warning horn. The warning horn went off. I slowed and the horn silenced. To slow down, I disengaged the autoplt then established proper airspeed and re-engaged autoplt. As attention was given to this task, 7000 ft assigned altitude was busted through to 6580 ft until descent was stopped and 7000 ft was regained. The captain helped by adjusting power and attitude to maintain 7000 ft. The total time out of 7000 ft was approximately 10 seconds and no radio xmissions were made, on the matter at hand. I am new in the aircraft, first month out of training, and this contributed to the incident. Basically, I fixated on the autoplt and readout and descended through the assigned altitude. Supplemental information from acn 421170: first officer was descending to 7000 ft MSL and did not have the flight director set properly and continued descent to 6600 ft before I noticed the deviation. I took over controls and climbed back to 7000 ft MSL.

Original NASA ASRS Text

Title: DH8 FO DSNDED BELOW HIS CLRNC ALT.

Narrative: DURING RADAR VECTOR FOR A VISUAL APCH TO RWY 18R AT CLT, CLRED HDG 090 DEGS AND DOWN TO 7000 FT. AUTOPLT ENGAGED. WE DSNDED VIA 'FPM' VERT SPD MODE. THIS CAN CAUSE OVERSPD WARNING HORN. THE WARNING HORN WENT OFF. I SLOWED AND THE HORN SILENCED. TO SLOW DOWN, I DISENGAGED THE AUTOPLT THEN ESTABLISHED PROPER AIRSPD AND RE-ENGAGED AUTOPLT. AS ATTN WAS GIVEN TO THIS TASK, 7000 FT ASSIGNED ALT WAS BUSTED THROUGH TO 6580 FT UNTIL DSCNT WAS STOPPED AND 7000 FT WAS REGAINED. THE CAPT HELPED BY ADJUSTING PWR AND ATTITUDE TO MAINTAIN 7000 FT. THE TOTAL TIME OUT OF 7000 FT WAS APPROX 10 SECONDS AND NO RADIO XMISSIONS WERE MADE, ON THE MATTER AT HAND. I AM NEW IN THE ACFT, FIRST MONTH OUT OF TRAINING, AND THIS CONTRIBUTED TO THE INCIDENT. BASICALLY, I FIXATED ON THE AUTOPLT AND READOUT AND DSNDED THROUGH THE ASSIGNED ALT. SUPPLEMENTAL INFO FROM ACN 421170: FO WAS DSNDING TO 7000 FT MSL AND DID NOT HAVE THE FLT DIRECTOR SET PROPERLY AND CONTINUED DSCNT TO 6600 FT BEFORE I NOTICED THE DEV. I TOOK OVER CTLS AND CLBED BACK TO 7000 FT MSL.

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.