Dash 8-200
Flight Crew Air Transport Pilot (ATP)
Other / Unknown
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance
Flight Crew Landed in Emergency Condition; General Declared Emergency; General Maintenance Action
Human Factors; Aircraft; Procedure
At just over 10;000 FT and descending into the terminal area we heard a loud bang with an abrupt change in attitude. The aircraft pitched down violently enough for us to come out of our seats. I immediately took a hold of the yoke and disengaged the autopilot to stabilize the aircraft. The airplane responded normally to flight inputs but had a harsh vibration. The vibration increased and decreased respectively to our airspeed. Once the aircraft was stable; I transferred the controls over to my First Officer so that I could communicate with ATC and troubleshoot the problem. There were no abnormal annunciations in the flight deck. We concluded that the best airspeed was 140 knots due to the least amount of vibration. We remained at that airspeed until our final approach and landed without incident.
The reporter states that post flight revealed that a panel on the vertical stabilizer; just below the horizontal stabilizer; had separated from the aircraft. According to the reporter it appeared to the Maintenance Technician involved that the washers that are normally between the fastener head and the panel had been omitted allowing the holes to enlarge until the panel slipped over the head and into the wind stream; separating from the aircraft.
DHC8-200 experiences a loud bang followed by a pitch down vigorous enough to lift the pilots off their seats. Airspeed is adjusted to minimize the vibration being felt; followed by a near normal landing.