An Aircraft Technician reports strong pressure by their Repair Station company Management to hurry and finish a calculated rudder balance procedure on a B737-300 aircraft that resulted in four additional weights being added to the rudder moment when four weights actually needed to be removed.

Narrative

The aircraft in question was at another Maintenance Repair Organization (MRO) facility for a rudder repair. The aircraft Operator; (a 121 Air Carrier); requested a copy of calculated rudder balance paperwork for a rudder balance which was performed after a paint visit approximately six months prior. Upon review and recalculation of the rudder balance; it was discovered that a mathematical error was made in the calculation. Issue: While performing the original calculated rudder balance per Structural Repair Manual (SRM) 51-60-07; the Rework Weight (RW) was incorrectly signed as a positive number; when it should have been signed as a negative number. As a result; the final trial Check Balance Moment Weight was incorrect. This resulted in four additional rudder weights being added to the rudder; when there should have been four weights removed. As a result; this aircraft flew for six months with a rudder that was out of the allowable check balance moment range. Contributing factors: There was strong pressure by Management to hurry and finish the aircraft so that it could be delivered on time. This rush to complete the work and get the aircraft out created an atmosphere where the time wasn't taken to double check the calculations.