1.   BA engineers removed two rudder units from the aircraft after it returned to Heathrow.

2.   If so, further tests must be done to see if the whole rudder power control unit must be replaced.

3.   Mechanics later removed and replaced the main rudder power control unit on the jet.

4.   Parker is the manufacturer of the rudder power control unit.

5.   She said Boeing has completed and approved the basic redesign of the rudder power control unit and submitted it to the FAA for review.

6.   That case also called for replacement of the main rudder power control unit.

7.   The company, however, told the NTSB that under certain extreme, hypothetical failure conditions, the rudder power control unit could malfunction.

8.   The FAA said it had received reports of two in-service malfunctions of rudder units.

9.   The rudder power control unit is similar to a power steering unit in a car.

10.   The screw is used to retain a spring on the rudder control unit.