brake-lever rod on the top of the instrument is movedto the closed position. This locks the pointer in place.Then, the lever assembly is released and theinstrument removed from the cable with the pointerlocked in position. After the reading has been noted,the brake-lever rod is moved to the open position, andthe pointer will return to zero.The tensiometer, like any other measuring instru-ment, is a delicate piece of equipment and should behandled carefully. Tensiometers should never bestored in a toolbox.Temperature changes must be considered incable-type systems since this will affect cabletensions. When a temperature is encountered that islower than that at which the aircraft was rigged, thecables become slack because the aircraft structurecontracts more than the cables. When temperatureshigher than that at which the aircraft was rigged areencountered, the aircraft structure expands more thanthe cables and tension is increased.The cables in any cable linkage system are riggedaccording to a temperature chart that is contained inthe applicable maintenance instructions manual. Thischart will give the proper tensions for the varioustemperature changes above and below thetemperature at which the system was rigged.Rig PinsRig pins are used in rigging control systems.Figure 9-24 shows a rigging pin kit used on one of theNavy’s aircraft. As you can see, rig pins may come invarious sizes and shapes and may be designed for oneor many installations. You should refer to the specificmaintenance instructions manual for use and selectionof rig pins.ThrowboardsThrowboards are special equipment used onspecific aircraft for accurate measurement of controlsurface travel. See figure 9-25. Each throwboard hasa protractor scale that indicates a range of travel indegrees. Zero degrees normally indicates the neutralposition of the control surface. When the throwboardis mounted and the control column or stick is inneutral, the trailing edge of the control surface shouldbe aligned to zero. As the control column or stick ismoved to its extreme limits, you can read thecorresponding degree indication on the throwboard.If the travel of the control surface is out of limits, youshould adjust cables, push-pull rods, and control limitstops to obtain the correct control surface travel.When you are inspecting and rigging control surfaces,the specific maintenance instructions manual shouldbe consulted.Figure 9-25.—Typical throwboard used for rigging rudder and rudder tab controls.9-31
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