After installation of winglets the two SMYD’s have different partnumbers! (see IPC) SMYD #2 is -1XX. SMYD #2 is calculating the wing loads. When the wings get overloaded, it reduces spoiler deflection with 50%. After performing the SMYD BITE – Ground test, only SMYD #2 is generating a complaint: YD Servo Loop (MSG 22-22006).
When performing the Servo Loop test, it is nesseccary to insert FMC ZFW (approx 54 tons for B737-700) first! This is not mentioned in the AMM or FIM! The SMYD #2 needs a valid FMC G/W signal for calculations. Thanks to Jan H. for his input.
