Procedures for rigging flight control systems vary with each type of aircraft. Applicable MIMs provide a list of tools, special equipment, preparatory con-siderations, and step-by-step instructions for rigging systems.

On some aircraft, the system rigging divides into a series of sections, such as the control stick, control mechanism, power control actuator, and cables. If only that section of the system has been affected, it may not be necessary to rig the complete system. Pushrods, bell cranks, and idlers are installed so that end play is eliminated. They should be free to rotate without binding. Cables should be inspected for corrosion, broken strands, and proper tension. Correct cable tension is necessary to obtain proper response of the control surface. Low cable tension may cause sluggishness, free play, and flutter of the control surface. Excessively high cable tension will cause increased system friction and may result in damage to pulleys, bell cranks, or the cable itself.

A variety of fixtures, pins, and blocks are available for performing alignment and rigging checks on flight control systems. Neutralizing (locking the controls and linkage in a predetermined position), as described in the aircraft MIM, is required during the alignment and adjustment of the flight controls.

NOTE: Installation and removal of the fixtures, pins, and blocks should not require excessive force. Slight pressure is per-missible because of the system tolerance and temperature effects on the aircraft. Always refer to the MIM for tolerance information.

Figure 9-18 shows the throw board used to check the travel of a horizontal stabilizer. The throwboard is held in place by two wingnut attachment screws. Before tightening these screws, the throwboard is positioned so that the alignment hole at the zero-degree mark is in line with the alignment screw in the aircraft fuselage.

Control surface throws may be measured in degrees and minutes or inches and fractions. Figure 9-19 provides an example of an aileron throw indication in degrees (0) and minutes (). The protractor scale is calibrated in 30-minute increments. The indicator reads 3 degrees 40 minutes obtained as follows:

1. Read 3 degrees 30 minutes, as shown on the protractor scale.

2. Since the indication mark does not fall directly on the calibrated mark of the protractor scale, look for the closest alignment of indicator and protractor calibrated marks in the direction of indicator travel. Read the value from the 0-minute mark on the indicator to the closest alignment, which, in this example, is 10 minutes.

3. Add 3 degrees 30 minutes and 10 minutes to get the true indication of 3 degrees 40 minutes up travel.

Each mode of operation that was affected by alignment or malfunction and subsequent repair action must be operationally checked, and the success of the checkouts verified by a qualified quality assurance representative. All maintenance, including alignment, adjustment, operational testing, and component replacement, must be in accordance with the instructions provided in the applicable MIM.