B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 220; Flight Crew Total 15000; Flight Crew Type 5000
Confusion; Human-Machine Interface; Situational Awareness; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Weight And Balance
Flight Crew Overcame Equipment Problem
Procedure; Aircraft
On the takeoff roll the nose came up and had to be manually held down with a stab trim of 4 ¼ [ANU]. Heavy nose [down] pressure was needed to accelerate in the climb. After reaching 250 KTS the jet operated normally. An ACARS was sent to Dispatch who said they would look into it. We decided to add 20 KTS to our [Ref speed] as a precaution against an aft CG problem. On descent we were cleared direct TRANN and slow to 210 KTS. As the speed approached 210 with the autopilot engaged the trim started cycling down then up repeatedly; not being able to find center. Even going flaps 1 and then flaps 5 the trim continued to constantly cycle up then down. We turned off the autopilot and hand flew to the runway keeping our 20 KTS addition without further incident.
[Report narrative contained no additional information.]
A B737 exhibited characteristics consistent with an excessively aft CG during the takeoff roll and on approach. The flight crew added a precautionary 20 KTS to the landing speeds.