A dash 8 flight crew descended below the assigned altitude near vcn.

Attributes
ACN	453390
Time
Date	199910
Day	Fri
Local Time Of Day	1201 To 1800
Place
State Reference	NJ
Altitude	msl bound lower : 3700 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : phl.tracon
Operator	common carrier : air carrier
Make Model Name	Dash 8-300
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 3200 flight time type : 500
ASRS Report	453390
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While approaching acy or vcn VOR from the northeast, we were given a descent to 4000 ft MSL. Passing/descending through 3750 ft, I disengaged the autoplt and climbed to 4000 ft. The altitude deviation may have hit 300 ft. The autoplt/flight director was in 'pitch' mode instead of 'altitude select.' 4000 ft was set in the altitude select window. Both pilots thought 'altitude select' was selected and did not know why the flight director was in 'pitch' mode. System worked ok for remainder of flight. Lesson: check, check, and rechk and verify with other pilot/center.

Original NASA ASRS Text

Title: A DASH 8 FLC DSNDED BELOW THE ASSIGNED ALT NEAR VCN.

Narrative: WHILE APCHING ACY OR VCN VOR FROM THE NE, WE WERE GIVEN A DSCNT TO 4000 FT MSL. PASSING/DSNDING THROUGH 3750 FT, I DISENGAGED THE AUTOPLT AND CLBED TO 4000 FT. THE ALTDEV MAY HAVE HIT 300 FT. THE AUTOPLT/FLT DIRECTOR WAS IN 'PITCH' MODE INSTEAD OF 'ALT SELECT.' 4000 FT WAS SET IN THE ALT SELECT WINDOW. BOTH PLTS THOUGHT 'ALT SELECT' WAS SELECTED AND DID NOT KNOW WHY THE FLT DIRECTOR WAS IN 'PITCH' MODE. SYS WORKED OK FOR REMAINDER OF FLT. LESSON: CHK, CHK, AND RECHK AND VERIFY WITH OTHER PLT/CTR.

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.