Blowdown

At higher airspeeds, the 737's maximum rudder deflection is limited by blowdown, helping to prevent flight-control inputs from overstressing the aircraft's vertical stabilizer.

According to Boeing, these movements were consistent with the effects of blowdown on those surfaces as documented during flight tests. However, the outboard aileron split recorded by the FDR after about 0150:27, which is discussed later in this section, was not consistent with the flight test data.

Give these parts a blowdown with your air hose before you put them in the ultrasonic cleaning tank.