1 STUDY UNIT FOUR AIRCRAFT LANDING GEAR INSPECTION 4.1 4.2 4.3 4.4 4.5 4.6 4.7 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fixed Gear Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Retractable Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Landing Gear Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tire Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wheel and Brake Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 4 5 7 11 14 This study unit reviews basic procedures for aircraft landing gear inspections for both fixed and retractable landing gear, based on the guidance found in AC 43.13-1B. The term “fixed gear” applies to aircraft equipped with wheels, floats, or skis (amphibians utilize a combination of retractable wheels and floats or floating hulls), whereas retractable gear equipped aircraft can only have wheels or skis. For the sake of simplicity, floats, skis, and amphibious aircraft landing gear will not be covered in this study unit. The landing gear on most aircraft is rugged in its design and often works well with a minimum of maintenance. Hence, it is an easy system to take for granted; that is, until it fails. With proper inspection and maintenance, the landing gear on the aircraft you inspect will likely give many years of trouble-free service. 4.1 GENERAL 1. The landing gear on an aircraft is divided into two categories: a. b. 2. For the purposes of inspection and maintenance, retractable gear is further divided into a. b. 3. Fixed Retractable Normal retraction systems, which are usually hydraulic, electric, or some combination thereof, but which can be manual with a lever in the cockpit. Emergency systems, which can be in the form of backup electric/hydraulic systems, gravity operated free-fall systems, or a pneumatic backup (e.g., on the Piper Aztec, PA-23, pressurized gas is discharged into the down side of the normally hydraulic actuators). In order to conduct an adequate inspection of an aircraft’s landing gear, the entire structure of the gear must be inspected in accordance with the manufacturer’s inspection procedures. This inspection includes a. b. c. d. e. f. g. h. i. Any item that may be attached to the main gear (e.g., fairings) Shock absorbing struts Wheels Brakes Gear hydraulic system (actuators, switches, and linkages) Gear doors and all associated parts All bolts and fittings – for security and condition, especially in torque links, as these tend to become especially loose due to operational loads Nose wheel shimmy dampers – for looseness due to operational loads The entire structure – for cracks, nicks, cuts, or corrosion damage and other damage potentially causing stress concentrations and eventual failure Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact email@example.com. 2 SU 4: Aircraft Landing Gear Inspection 4. Prior to the inspection and before removing any accumulated dirt, closely observe the area being inspected while the wingtips are gently rocked up and down. Excessive motion between normally close-fitting landing gear components may indicate wear, cracks, or improper adjustment. If a crack exists, it will generally be indicated by dirt or metallic particles, which tend to outline the fault. Seepage of rust-inhibiting oils, used to coat internal surfaces of steel tubes, also assists in the early detection of cracks. In addition, a sooty, oily residue around bolts, rivets, and pins is a good indication of looseness or wear. 5. Cleaning and Lubrication. In order to conduct a proper inspection, aircraft landing gear must be clean to facilitate better inspection. Following the inspection, the gear should be lubricated in accordance with the manufacturer’s instructions. a. b. c. d. If cleaning is necessary, it is recommended that only a mild, easily-removable, pH-neutral cleaning solution be used, as highly corrosive cleaning agents may become trapped in close-fitting surfaces and crevices only to cause future problems. Inspection of components should include a thorough visual inspection. Other inspection means such as dye-penetrant, magnetic particle, radiography, ultrasound, or eddy current may be required. The type of material, size, age, degree of use, operational history, and most importantly, manufacturer’s recommendations will dictate the type of inspection means to use. Following the cleaning and inspection, wear points, such as those listed below, should be lubricated: 1) Gear up and down latches 2) Jack screws 3) Door hinges 4) Pulleys 5) Cables 6) Bellcranks 7) Pressure-type grease fittings In order to prevent component failure due to grease compatibility problems, 1) 2) 3) e. Use only manufacturer approved greases. Never mix different kinds of grease without prior manufacturer approval. Follow manufacturer instructions for cleaning, purging, and lubricating of components. Jacking the aircraft may be necessary in order to achieve proper lubrication. 1) f. 6. While the aircraft is on jacks, the main gear support bushings should be checked for wear in accordance with the manufacturer’s guidance. During winter operation, excess grease may congeal and cause increased loads on any retraction system motors or pumps. This is a condition which can lead to premature failure. As such, proper cleanliness and lubrication are especially important in aircraft exposed to these conditions. If a crack is found in a landing gear member, the part MUST be replaced. 4.2 FIXED GEAR INSPECTION 1. During a 100-hr. or annual inspection, all fixed-gear aircraft should be jacked up so as to relieve the weight of the aircraft from the wheels in order to facilitate a more thorough inspection. During this inspection, check the gear components for a. b. c. d. Excessive wear and play Deterioration Corrosion Proper alignment Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact firstname.lastname@example.org. 3 SU 4: Aircraft Landing Gear Inspection 2. Many older aircraft employ rubber shock cords (bungee cords) for shock absorption. These cords are subject to deterioration with exposure and age and must therefore be thoroughly inspected for a. b. c. d. e. Age – replacing cords after 5 years in service is recommended. Fraying of the braided sheath. Narrowing or “necking” of the cord. Wear at any contact points with the structure. Excessive stretch. Piper Cub bungee cord landing gear transfer landing loads to the airframe (left and center). Rubber, donut-type shock transfer is used on some Mooney aircraft (right) 3. Bungee cords are color coded with interwoven threads (into the cotton sheath that surrounds the strands of rubber cord) according to date of manufacture as an aid in determining the life of the cord. a. b. c. This color code is repeated in 5-year cycles. Two spiral threads are used to indicate the year coding and one thread is used for the quarter of the year. The table below indicates the color-coding system used for aircraft shock cords. Years Ending With 0 or 5 1 or 6 2 or 7 3 or 8 4 or 9 Color Black Green Red Blue Yellow Quarter 1st 2nd 3rd 4th 1st Color Red Blue Green Yellow Red Bungee Cord Color-Coding System WARNING: Removal and replacement of aircraft shock cords can be extremely dangerous if not done correctly! Several aircraft mechanics have been injured or killed when the lever they were using to stretch the bungee snapped back, striking the mechanic. If this procedure is new to you, it is advisable that you seek experienced help for this procedure. 4. Struts a. Spring-oleo type struts should be examined for leakage, smoothness of operation, looseness between moving parts, and play at the attachment points. 1) b. Check that springs are not worn or broken and that the piston is free of nicks, cuts, or rust. 2) The exposed lower end of the oleo struts is especially susceptible to corrosion and damage. 3) Small nicks and cuts can be burnished to a smooth contour. Air-oil struts should be inspected in a similar manner to spring-oleo struts. 1) 2) 3) Strut extension distance should be checked in accordance with manufacturer’s recommendations. Also check for proper gas charge over the hydraulic portion of the cylinder. Defective O-ring seals usually cause a “bottoming” of the strut. CAUTION: Prior to removing or disassembling an air-oleo strut, remove all gas pressure. Even a small amount of gas pressure can cause injury or damage. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact email@example.com. 4 SU 4: Aircraft Landing Gear Inspection 5. Nose gear inspection. Inspect all nose gear assembly components including mud scrapers and slush deflectors for damage. Also, inspect the nose gear steering assembly for a. b. c. d. Torque link/tube security (scissors). Control rods – security. Rod end bearings – security. Shimmy dampers – inspect for leakage around the piston shaft and at fluid line connections for abnormal wear or looseness around pivot points. Also check for proper rigging of the piston in the cylinder and condition of the external stops on the steering collar. e. Cables – proper tension. f. Turning stops for proper location and condition. NOTE: Towing some aircraft with rudder locks installed may damage the steering linkage and rudder control system. In addition, exceeding steering or towing stop limits should be followed by a close inspection of the nose wheel steering assembly. A broken steering stop will allow turning beyond the design limit, transmitting excessive loads to surrounding structures, and to the rudder control system. To prevent this, ensure that the nose wheel steering arc limits are painted on the steering collar or fuselage. 6. Tail wheels. It is often necessary to disassemble, clean, and re-rig tail wheels depending upon operational use. During this procedure, the inspector should check for a. b. c. d. e. Loose or broken bolts. Broken springs. Lack of lubrication. General condition. Steerable tail wheels should be checked for proper steering action, steering horn wear, clearances, and security/condition of steering springs and cables. 4.3 RETRACTABLE GEAR 1. An inspection of retractable landing gear should accomplish the following: a. b. c. d. e. 2. All applicable items previously mentioned in the inspection of fixed gear Actuating mechanisms – for looseness in any joint, trunnion, or bearing Leakage of fluid from any hydraulic line or unit Smoothness of operation Operational check of the extension and retraction mechanism Operational (retraction) test. During this test, observe the landing gear system for a. b. c. d. e. f. g. h. Smoothness of operation. Warning horn operation. Operation of the indicating systems. Clearance of tires in wheel wells. Operation of landing gear doors – for proper sequencing and closure upon retraction (rigging). Also inspect gear doors for cracks and deformation. Gear door hinges are particularly susceptible to progressive cracking, potentially leading to failure and possible gear jamming. Also check for proper safetying of the hinge pins and the integrity of the hinge attachment hardware. Inspect wheel wells for proper routing of components and related tubing or wiring, which could interfere with the travel of the gear door actuating mechanism. Inspect micro-switches for security of attachment, cleanliness, general condition, and proper operation. Check for chafing, proper wire routing, and terminal cover protector installation in addition to any dust boots. Be sure to follow the guidance found in the manufacturer’s maintenance instructions. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact firstname.lastname@example.org. 5 SU 4: Aircraft Landing Gear Inspection 3. With the aircraft still on jacks, it is a good opportunity also to inspect for a. b. c. d. e. Looseness of mounting points. Play in torque links. Condition of the inner strut cylinder. Play in wheel bearings and in actuating linkages. Inspect blow-down gear bottles. Check for corrosion or damage, and weigh the bottles to check for proper gas charge. NOTE: AC 43.13-1B CHG 1 Page 9-12 Para 9-19 contains the following information with respect to retread tires: Mechanics should be aware that retread tires can be diametrically bigger than a “new” tire. While this does not pose a problem on fixed landing gear aircraft, it may pose a problem on retractable gear aircraft. Due to a 5 to 8 percent expansion of the tire caused by the ambient temperature, if a retread tire is installed on a retractable gear aircraft, it is strongly recommended that a retraction test be performed. This is to ensure the tire will not become wedged in the wheel well during take-off and landing operation. Although that note is contained in an FAA Advisory Circular, some believe that it is somewhat at odds with standard industry practices. The FAA provides strict guidelines to repair stations that perform retread operations, and these guidelines state that the retreaded tire dimensions must comply with industry (TRA and ETRTO) accepted practices. It is accepted practice for a tire, whether new or a retread, to properly fit the application for which it is intended to be installed (within the manufacturer’s allowable tolerances), so a retreaded tire that is dimensionally larger or smaller than a new tire should be removed from service. Perhaps in the past when production tolerances for replacement parts were not so rigid as they are today, it may have been common for retread tires to be of unusual dimensions, but this should not occur under the guidance of current regulations. Still, the FAA’s advice is sound, and a retraction test would be a good way of eliminating doubt. f. As the aircraft is being lowered from the jacks, a test of the anti-retraction system (i.e., limit switches) can be made. In every case, the test should reveal that the gear handle cannot be placed into the up position unless the shock strut is fully extended. 4.4 TYPES OF LANDING GEAR PROBLEMS 1. Crack-prone areas on any landing gear include a. b. c. d. e. 2. Bolts Bolt holes Pins Rivets Welds Concerning bolts, the most susceptible areas for bolts are at the radius between the head and the shank, and in the location where the threads join the shank, as shown below. Typical bolt cracks. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact email@example.com. 6 SU 4: Aircraft Landing Gear Inspection 3. Cracks primarily occur at the edge of bolt holes on the surface and down inside the bore as shown in the following figures. Typical cracks near bolt holes. Typical bolt hole cracks. 4. Typical failures in riveted joints or seams are indicated by deformation of the rivet heads and skin cracks originating at the rivet holes. 5. Cracks and subsequent failures of rod ends usually begin at the thread end near the bearing and adjacent to or under the jam nut as shown below. Typical rod-end cracks. 6. Concerning welds, cracks develop primarily along the edge of the weld adjacent to the base metal and along the centerline of the bead. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact firstname.lastname@example.org. SU 4: Aircraft Landing Gear Inspection 7. 7 Elongated holes are especially prevalent in taper-pin holes and bolt holes or at the riveted joints of torque tubes and push-pull rods, as shown below. Typical torque tube bolt hole elongation. 8. Deformation can occur in landing gear control rods and tubes and is most often noticeable as stretched, bulged, or bent sections. Visual detection of this type of defect is sometimes difficult; therefore, a touch inspection may be necessary to reveal this type of defect. Placing a shop light at an oblique angle to a suspected deformed section may highlight deformed sheet-metal sections at landing gear attachment points. 4.5 SPECIAL INSPECTIONS 1. A hard or overweight landing necessitates a special structural inspection of the aircraft to include the landing gear. During the gear inspection a. b. c. d. 2. Inspect landing gear support trusses for cracked welds, sheared bolts/rivets, and buckled structures. Wheels and tires should be inspected for cracks and cuts. Upper and lower wing surfaces should be inspected for wrinkles, deformation, and loose/sheared rivets. Any damage found during this inspection should result in a further detailed investigation. Alignment of the wheels of an aircraft is also a consideration, especially after a hard landing. a. b. c. d. Normally, this is set by the manufacturer and only requires occasional attention. The aircraft’s main wheels must be inspected and adjusted, if necessary, to maintain the proper tow-in or tow-out and the correct camber. Tow-in and tow-out refer to the path a main wheel would take in relation to the airframe longitudinal axis or centerline if the wheel was free to roll forward. Three possibilities exist: 1) e. The wheel would roll either a) Parallel to the longitudinal axis (aligned), b) Converge on the longitudinal axis (tow-in), or c) Veer away from the longitudinal axis (tow-out). The manufacturer’s maintenance instructions give the procedure for checking and adjusting tow-in or tow-out. Wheel alignment on an aircraft. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact email@example.com. 8 SU 4: Aircraft Landing Gear Inspection 3. A wheel bearing inspection may be required after a hard landing, excessive side-loading, or hot brakes. a. Once cleaned, the wheel bearing is inspected. 1) b. There are many unacceptable conditions of the bearing and bearing cup, which are grounds for rejection. 2) In fact, nearly any flaw detected in a bearing assembly is likely to be grounds for replacement. Common conditions of a bearing that are cause for rejection are as follows: 1) Galling—caused by rubbing of mating surfaces. a) The metal gets so hot it welds, and the surface metal is destroyed as the motion continues and pulls the metal apart in the direction of motion. Galling is caused by rubbing of mating surfaces. The metal gets so hot it welds, and the surface metal is destroyed as the motion continues and pulls the metal apart in the direction of motion. 2) Spalling—a chipped away portion of the hardened surface of a bearing roller or race. Spalling is a chipped away portion of the hardened surface of a bearing roller or race. 3) Overheating—caused by lack of sufficient lubrication results in a bluish tint to the metal surface. a) b) The ends of the rollers shown were overheated causing the metal to flow and deform, as well as discolor. The bearing cup raceway is usually discolored as well. Overheating caused by lack of sufficient lubrication results in a bluish tint to the metal surface. The ends of the rollers shown were overheated causing the metal to flow and deform, as well as discolor. The bearing cup raceway is usually discolored as well. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact firstname.lastname@example.org. SU 4: Aircraft Landing Gear Inspection 4) 9 Brinelling—caused by excessive impact. a) b) It appears as indentations in the bearing cup raceways. Any static overload or severe impact can cause true brinelling that leads to vibration and premature bearing failure. Brinelling is caused by excessive impact. It appears as indentations in the bearing cup raceways. Any static overload or severe impact can cause true brinelling, which leads to vibration and premature bearing failure. 5) False Brinelling—caused by vibration of the bearing while in a static state. a) b) c) d) Even with a static overload, lubricant can be forced from between the rollers and the raceway. Submicroscopic particles removed at the points of metal-to-metal contact oxidize. They work to remove more particles spreading the damage. This is also known as frictional corrosion. It can be identified by a rusty coloring of the lubricant. False brinelling is caused by vibration of the bearing while in a static state. Even with a static overload, it can force the lubricant from between the rollers and the raceway. Submicroscopic particles removed at the points of metal-to-metal contact oxidize. They work to remove more particles spreading the damage. This is also known as frictional corrosion. It can be identified by a rusty coloring of the lubricant. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact email@example.com. 10 SU 4: Aircraft Landing Gear Inspection 6) Staining and surface marks—located on the bearing cup as grayish black streaks with the same spacing as the rollers and caused by water that has gotten into the bearing. a) It is the first stage of deeper corrosion that follows. Staining and surface marks on the bearing cup that are grayish black streaks with the same spacing as the rollers are caused by water that has gotten into the bearing. It is the first stage of deeper corrosion that will follow. 7) Etching and corrosion—caused when water and the damage caused by water penetrates the surface treatment of the bearing element. a) It appears as a reddish/brown discoloration. Etching and corrosion is caused when water, and the damage caused by water, penetrates the surface treatment of the bearing element. It appears as a reddish/brown discoloration. 8) Bruising—caused by fine particle contamination possibly from a bad seal or improper maintenance of bearing cleanliness. a) It leaves a less than smooth surface on the bearing cup. Bruising is caused by fine particle contamination possibly from a bad seal or improper maintenance of bearing cleanliness. It leaves a less than smooth surface on the bearing cup. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact firstname.lastname@example.org. SU 4: Aircraft Landing Gear Inspection c. 11 The bearing cup does not require removal for inspection; however, it must be firmly seated in the wheel half boss. 1) There should be no evidence that a cup is loose or able to spin. Bearing cups should be tight in the wheel boss and should never rotate. The outside of a bearing cup that was spinning while installed in the wheel is shown. 2) The cup is usually removed by heating the wheel in a controlled oven and pressing it out or tapping it out with a non-metallic drift. a) b) c) d) The installation procedure is similar. The wheel is heated and the cup is cooled with dry ice before it is tapped into place with a non-metallic hammer or drift. The outside of the race is often sprayed with primer before insertion. Consult the wheel manufacturer’s maintenance manual for specific instructions. 4.6 TIRE INSPECTION 1. Inspect aircraft tires to ensure they are in proper balance. a. b. 2. A tire, tube, or wheel with a heavy spot will result in uneven tire wear and flat spotting as the heavy spot will cause the same spot on the tire to impact the runway first during each landing. This can cause excessive vibration and lead to premature failure. When servicing components on an aircraft which may leak fluid onto the aircraft tires, take precautions to protect the tires as many of these fluids can lead to tire deterioration. Cover tires to protect from harmful chemicals and from the elements when parked outside for long periods of time. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact email@example.com. 12 SU 4: Aircraft Landing Gear Inspection 3. When inspecting aircraft tires, pay particular attention to the following: a. b. Tread wear. Remove tires when the tread has worn to the base of any groove at any one spot on the tire or is worn to the minimum tread depth specified by the manufacturer. Any fabric showing through in the tread area is cause for replacement of the tire. Uneven wear. If there is excessive tread wear on one side of the tire, it can be dismounted and turned around; however, any possible wheel misalignment causing this problem should be investigated. NOTE: Wheel alignment also should be considered on any aircraft where directional control is reported to be a problem during ground operations. c. Tread Cuts. Look for cuts in the tread and any other foreign object damage. Remove tires that have the following: 1) 2) 3) 4) 5) Cuts into the carcass ply (the reinforced structure of the tire which lies beneath the outer visible rubberized coating). Cuts extending more than half of the width of a rib (raised tread section between two tread grooves) and deeper than 50% of the remaining groove depth. Weather checking, cracking, cuts, and snags extending down to the carcass ply in the sidewall and bead (next to wheel flange) areas. Bulges in any part of the tire tread, sidewall, or bead areas that indicate a separation or damaged tire. Cracking in a groove that exposes fabric or if cracking undercuts tread ribs. Remove an aircraft tire from service when the depth of a cut exposes the casing outer plies of a bias ply tire or the outer belt layer of a radial tire (A); a tread rib has been severed across the entire width (B); or, when undercutting occurs at the base of any cut (C). These conditions may lead to a peeled rib. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact firstname.lastname@example.org. SU 4: Aircraft Landing Gear Inspection d. e. f. g. 13 Flat spots. Flat spots need not be addressed providing they are not causing significant imbalance or provided there is no exposed fabric. Beads. Pay particular attention to the tire bead area, or the area next to the wheel flange for damage. Excessive heat generated through heavy braking can be transmitted to the tire at this point, causing premature tire damage and failure. In addition, damage such as nicking or gouging in this area can cause stresses to concentrate here, leading to tire failure. Tire Clearance. Look for marks on tires, wheel wells, and landing gear indicating tires are rubbing due to clearance problems caused by over-inflation or damage. Surface Condition. Look for irregular wear patterns on the tire such as may be caused by under- or over-inflation (see below). Heavy center tread wear indicates overinflation, and heavy edge tread wear indicates under-inflation. Examples of tread wear indicating over-inflation and under-inflation. WARNING: When inflating tires, always adhere to the manufacturer’s recommended inflation pressure. Also, whenever possible, inflate tires in a safety cage to prevent injury should the wheel fail. NOTE: When inflating aircraft tires, nitrogen is recommended. Do not use oxygen. Additionally, wear protective eye wear to reduce the risk of injury when inflating/ deflating aircraft tires or when working with an inflated tire. WARNING: Deflate tires: 1) prior to removing them from an aircraft, 2) prior to ANY type of wheel maintenance, or 3) prior to shipping them. Failure to deflate tires prior to maintenance can result in serious injury or death, in addition to equipment damage. WARNING: When servicing aircraft tires, personnel should stand either in front of or to the rear of the wheel and avoid approaching from either side of the tire. This will minimize injury should a blow-out occur. This is also good practice when approaching landing gear on an aircraft which has just experienced heavy operational brake usage. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact email@example.com. 14 SU 4: Aircraft Landing Gear Inspection 4. The inspection of a mounted tire presents a good opportunity to check wheel alignment. a. b. Improper wheel alignment can cause reduced tread life and directional control problems during ground operations. Follow the airframe manufacturer’s instructions for this inspection. But as a general guide, 1) 2) 3) 4) Place the aircraft on jacks so that the weight of the aircraft is completely on the jacks. Place the aircraft in a level flight attitude as determined by the manufacturer. Establish a proper centerline for the gear from which to create jigs and then take the measurements in order to check for deviation from the centerline. Alignments are made by adding or subtracting washers from the pivot point where the top and bottom torque link assembly mate. 4.7 WHEEL AND BRAKE INSPECTION 1. Wheels. Inspect wheels carefully for cracks, corrosion, dents, distortion, and faulty bearings. a. b. c. d. e. f. g. h. i. 2. All Brakes. Disassemble and inspect the brakes periodically and examine parts for a. b. c. d. e. f. g. 3. Check for bolt-hole elongation in split-type wheels and recondition by installing inserts or other approved means. Inspect the through bolts and associated nuts visually and by magnetic particle machine if possible (follow manufacturer’s recommendations). Also check for elongation of the bolts. Check tubeless tire wheels for damage to the flange area and for proper valve sealing. Ensure the sealing O-ring between the wheel halves is free of damage and deformation. Clean and inspect wheel bearings; replace if excessively worn or overheated. Maintain bearings and races as matched sets. Grease retaining felts in the wheel assembly should be inspected for a soft, absorbent condition. Recondition or replace if necessary. Remove all corrosion from wheel halves and apply corrosion prevention measures. Prime with zinc chromate primer or equivalent and at least two finish coats. Although minor dents do not affect the airworthiness of the wheel, replace any wheel that wobbles in any way during rotation. When bolting wheel halves together, use the correct torque value and torque with a star torque pattern unless otherwise directed. Check the torque value periodically during service. Wear Cracks Warpage Corrosion Elongated holes Overheating – indicated by discoloration Repair or replace as necessary in accordance with manufacturer’s recommendations. Hydraulic Brakes. Inspect entire brake hydraulic system from reservoir to brake pads for brake fluid level, fluid leakage, twisted lines, or otherwise damaged components. Copyright © 2015 Gleim Publications, Inc. All rights reserved. Duplication prohibited. Reward for information exposing violators. Contact firstname.lastname@example.org.