1,800 psi, and then all gear assemblies should start to retract. When the nose gear nears the up position, be sure the fairing doors are cammed to the closed position, and then check all gear doors to be sure they are closed and locked when the position indicator indicates the up-and-locked condition. Move the landing gear handle down and check to see that the wheel fairing doors open and gear assemblies extend. Visually check all gear assemblies to ensure they are down and locked. With the test stand regulated to 3 gpm at 3,000 psi, the gear should make a complete cycle (up and down) in 12 to 14 seconds. The maximum pressure required to retract and lock the gear is 1,800 psi at 4 gpm. When you check the emergency extension of the gear, first retract the gear normally, secure external hydraulic pressure, place the landing gear handle in the down position, and then pull and hold the emergency extension handle fully aft. Visually check that all gear assemblies are down and locked by observing the landing gear position indicator in the cockpit, and then release the emergency extension handle. It may be neccssary to manually push the gear assemblies to the down-and-locked position. The force required to push the main gear to the locked position should not exceed 20 pounds applied to the axle hub. The force required to push the nose gear to the locked position should not exceed 10 pounds applied at the center line of the axle hub. Make at least one complete normal cycle of the landing gear, and then remove external power and aircraft from jacks. NOTE: Some aircraft require resetting of the landing gear dump valves before recycling the landing gear. Refer to the applicable MIMs. TROUBLESHOOTING Troubleshooting of the landing gear system, like all hydraulic systems, requires that you understand the theory of operation of the particular system and the function and sequence of operation for each component. Troubleshooting steps provided in the MIM are normally aligned with the sequence of events or steps in the operational checkouts. They provide an efficient means of isolating the malfunction. The MIM requires that each step in the operational checkouts be performed in sequence. If trouble occurs during the procedure, it must be corrected before proceeding with the next step. These troubleshooting aids provide a logical cause for many anticipated landing gear malfunctions, including procedures for isolating and remedying the problem. Refer to the system schematic for the particular system and accompanying maintenance instructions, in addition to sound reasoning, to pinpoint the cause for a malfunction in an efficient manner. Some landing gear malfunctions are related to improper maintenance practices, with the lack of proper lubrication being the predominant malpractice. A review of past discrepancies and previous corrective actions may also aid in analyzing malfunctions. Occasionally, discrepancies that are reported as a result of flight are difficult or even impossible to duplicate on the deck. However, too many discrepancies signed off with “Could not duplicate–system checks 4.0,” or similar corrective actions, show up as repeat malfunctions or as the cause of accidents. Every effort should be made to locate a sound logical cause for a reported malfunction by thoroughly checking the system, each component, linkages, clearance, and associated indicating systems. All phases of the operational checkouts must be verified by a quality assurance inspector. Detecting internal leakage of components may require the use of special equipment, such as the ultrasonic leak detection translator or simple isolation of components by disconnecting lines, applying pressure, and measuring for allowable leakage limits. If troubleshooting time is considered significant, use a separate VIDS/MAF showing a common job control number and Action Taken code “Y.” This form provides input data that accounts for the troubleshooting time separately from the actual repair time. ALIGNMENT AND ADJUSTMENT Improper rigging or adjustment of landing gear linkages results in a significant number of unsafe or hung landing gear discrepancies. Most landing gear, when in an overcenter and locked position (up or down), requires very little interference or binding to prevent its initial movement. Alignment of newly installed landing gear assemblies or individual components should be in strict accordance with the procedures outlined in the applicable MIM. Complete assemblies are aligned in a specified sequence, with designated steps throughout the sequence that require quality assurance verification before proceeding to the next step. Landing gear doors may have to be deactivated or disconnected to check for proper up lock actuation and gear up clearances. 12-19