can be misinterpreted, and the resultant write-up in the aircraft discrepancy portion of the aircraft flight record book may be vague or misleading. To gain further insight regarding the vague discrepancy, the maintenance crew should question the pilot who experienced the malfunction. Isolating the mechanical and hydraulic portion of the flight control system from systems that provide automatic input will serve to pinpoint the actual problem area. The MIM provides troubleshooting/ trouble analysis aids and appropriate schematics. The MIM allows for the systematic checking out of the system and associated components. In some MIMs these aids are general in nature and limited to the more common causes of failure. Several MIMs combine the operational checkout procedures with trouble analysis aids. Steps of the checkout procedures are performed in rigid sequence, and any discrepancy must be corrected before proceeding to the next step. A thorough knowledge of the system involved and consistent use of the mechanical and hydraulic schematics will expedite the trouble analysis process. Excessive time required for troubleshooting should be documented on a separate VIDS/MAF. This will separate the actual repair time from troubleshooting time. Separate VIDS/MAFs provide more accurate input information to the Maintenance Data Reporting System. When the malfunction has been determined and corrected, the complete system should be opera- tionally tested. Testing should occur in all modes of operation to verify system integrity. Quality assurance inspection during repair progression, testing, and of the end product is a must. When prescribed in the applicable periodic maintenance information cards, test flight requirements are mandatory. The test flight pilot is briefed by a qualified quality assurance representative regarding the nature of the discrepancy and corrective action taken. ALIGNMENT AND OPERATIONAL CHECKS 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. 9-24