What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) On December 19, 2000, at 07:28 local time, a Dehavilland dash 8 series 102 aircraft, bearing registration number N843EX, serial number 335, operating as allegheny airlines as flight 3899 under 14 CFR part 121, departed the broome county airport (bgm) in johsnon city, NY enroute to allentown, PA. Acording to the flight crew, during climb out in level flight, the first officer's attitude directional indicator (ADI) indicated an 8-degree bank to the right. This condition was followed by a series of messages appearing on the 802 panel including HSI mismatch, ahrs data invalid, ADI pitch mismatch and yd disengaged. The crew retuned to the bgm airport and the aircraft was taken to the allegheny airlines maintenance hangar. Maintenance personnel removed and replaced the #2 ahrs and @2 ADI. The aircraft was returned to service. This incident is considered closed.
As the FAA filed it
(-23) ON DECEMBER 19, 2000, AT 07:28 LOCAL TIME, A DEHAVILLAND DASH 8 SERIES 102 AIRCRAFT, BEARING REGISTRATION NUMBER N843EX, SERIAL NUMBER 335, OPERATING AS ALLEGHENY AIRLINES AS FLIGHT 3899 UNDER 14 CFR PART 121, DEPARTED THE BROOME COUNTY AIRPORT (BGM) IN JOHSNON CITY, NY ENROUTE TO ALLENTOWN, PA. ACORDING TO THE FLIGHT CREW, DURING CLIMB OUT IN LEVEL FLIGHT, THE FIRST OFFICER'S ATTITUDE DIRECTIONAL INDICATOR (ADI) INDICATED AN 8-DEGREE BANK TO THE RIGHT. THIS CONDITION WAS FOLLOWED BY A SERIES OF MESSAGES APPEARING ON THE 802 PANEL INCLUDING HSI MISMATCH, AHRS DATA INVALID, ADI PITCH MISMATCH AND YD DISENGAGED. THE CREW RETUNED TO THE BGM AIRPORT AND THE AIRCRAFT WAS TAKEN TO THE ALLEGHENY AIRLINES MAINTENANCE HANGAR. MAINTENANCE PERSONNEL REMOVED AND REPLACED THE #2 AHRS AND @2 ADI. THE AIRCRAFT WAS RETURNED TO SERVICE. THIS INCIDENT IS CONSIDERED CLOSED.