LJ35 PF descended through assigned altitude.

Attributes
ACN	523420
Time
Date	200108
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : har.vortac
State Reference	PA
Altitude	msl bound lower : 27250 msl bound upper : 28000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Operator	general aviation : corporate
Make Model Name	Learjet 35
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine
Experience	flight time last 90 days : 150 flight time total : 11000 flight time type : 6500
ASRS Report	523420
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance
Resolutory Action	flight crew : returned to assigned altitude none taken : detected after the fact
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

The flying sic descended through the assigned leveloff altitude. First indication was altitude alerter. Total deviation was 750 ft. There was no conflict and the recovery was completed without center noticing. All altitude calls, readbacks, and confirmations were made by both crew members. The flying sic thought we were cleared to FL250 (an expect clearance). At the time of the deviation I was coordinating heading changes with center for thunderstorm avoidance. Fatigue was also a factor on my part.

Original NASA ASRS Text

Title: LJ35 PF DSNDED THROUGH ASSIGNED ALT.

Narrative: THE FLYING SIC DSNDED THROUGH THE ASSIGNED LEVELOFF ALT. FIRST INDICATION WAS ALT ALERTER. TOTAL DEV WAS 750 FT. THERE WAS NO CONFLICT AND THE RECOVERY WAS COMPLETED WITHOUT CTR NOTICING. ALL ALT CALLS, READBACKS, AND CONFIRMATIONS WERE MADE BY BOTH CREW MEMBERS. THE FLYING SIC THOUGHT WE WERE CLRED TO FL250 (AN EXPECT CLRNC). AT THE TIME OF THE DEV I WAS COORDINATING HEADING CHANGES WITH CTR FOR TSTM AVOIDANCE. FATIGUE WAS ALSO A FACTOR ON MY PART.

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.