Dash 8-100
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Critical
Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft; Weather
First Officer was the flying pilot. After rotation First Officer felt the elevator was heavy and oversensitive. After we cleaned up the aircraft and ran the checklist I confirmed that there was a 5 second delay between elevator command and elevator reaction. [I was] asked to return to the airport and notified flight attendant; Operations; and passengers that we were returning to land. I did not declare an emergency; approach was normal until flare; then the pitch became over sensitive; notified Dispatch and Maintenance.
During before takeoff controls check the elevator felt heavy; but with a tail wind on the parallel taxiway; this was normal. The take-off run was normal until Vr; the elevator was slow to respond and over sensitive. The aircraft over pitched to 12-15 degrees and I relaxed the back pressure to 8 degrees and the aircraft nose lowered to about 4 degrees. The aircraft oscillated a few more times until it stabilized into a normal climb attitude. After aircraft clean up and running appropriate checklists; the Captain confirmed that the controls were slow to react; 3-5 seconds between input command and elevator reaction. We discussed if we should continue or not. The Captain and I agreed to return to the field. I flew a wide downwind leg to give the Captain time to call the Flight Attendant; Operations and make a PA to the passengers that we were returning. The Captain did not declare an Emergency because we had control of the aircraft. We configured the aircraft early with gear down; flaps 15 degrees and 1200 RPM. The approach was normal until the flare; and then the elevator was overly pitch sensitive again and oscillated between too high and low for normal landing attitude. The aircraft bounced once and landed firm. We cleared the runway and taxied to the gate. The Captain called Dispatch and talked to Maintenance. The aircraft was taken to the Hangar and the flight was canceled. We found out later; that the elevator servo for the auto-pilot was partially jammed. The servo was removed and replaced.
DHC100 flight crew detects strange elevator response during takeoff and initial climb. The crew elects to return to the departure airport where maintenance discovers the autopilot elevator servo is partially jammed. Tail winds during the elevator check prior to takeoff apparently masked the condition.