Door arm stop Bellcrank Uplock Uplock push-pull tube Door actuator .22 ± .03 inches overcenter Push-pull tube Push-pull tube Gear strut Bellcrank Torque tube Side link Side brace lock link Bellcrank Landing gear actuator Spring scale Adjustable link B A B A Figure 13-49.  Over-center adjustments on a small aircraft main gear.  Landing Gear Retraction Test  13-29 2.  Check all switches, lights, and warning devices for  proper operation. 1.  Check the landing gear for proper extension and  retraction. The following is a list of general inspection items to be  performed while swinging the gear: The proper functioning of a landing gear system and  components can be checked by performing a landing gear  retraction test. This is also known as swinging the gear. The  aircraft is properly supported on jacks for this check, and  the landing gear should be cleaned and lubricated if needed.  The gear is then raised and lowered as though the aircraft  were in flight while a close visual inspection is performed.  All parts of the system should be observed for security and  In addition to the amount the side brace links are adjusted  to travel over center, down lock spring tension must also be  checked. This is accomplished with a spring scale. The tension  on this particular gear is between 40 and 60 pounds. Check the  manufacturer’s maintenance data for each aircraft to ensure  correct tensions exist and proper adjustments are made. Retraction tests are performed at various times, such as  during annual inspection. Any time a landing gear component  is replaced that could affect the correct functioning of the  landing gear system, a retraction test should follow when  adjustments to landing gear linkages or components that  affect gear system performance are made. It may be necessary  to swing the gear after a hard or overweight landing. It is  also common to swing the gear while attempting to locate  a malfunction within the system. For all required retraction  tests and the specific inspection points to check, consult  the manufacturer’s maintenance manual for the aircraft in  question as each landing gear system is unique. proper operation. The emergency back-up extension system  should be checked whenever swinging the gear.  To adjust the over-center position of the side brace locking  link, the aircraft must be placed on jacks. With the landing  gear in the down position, the lock link end fitting is adjusted  so that the side brace links are held firmly over-center. When  the gear is held inboard six inches from the down and locked  position and then released, the gear must free fall into the  locked down position. 