飞机轮胎介绍

,Aircraft System Aircraft Tires,Classification of Tires Type Size Ply rating (层数） Tube or tubeless,Classification of Tires Type tire Characteristic: Low pressure, piston-power aircraft. Construction character: The section width is relatively wide in relation to the bead diameter. Designating Method: Section width and rim diameter 9.50-16 tire: the section width is 9.5 inches, the rim diameter is 16 inches.,Classification of Tires Type tire Characteristic: Extra-high pressure, jet aircraft. Construction character: Ply rating from 4 to 38. Designating Method: Outside diameter and section width 3813 tire: The outside diameter is 38 inches, the section width is 13 inches.,Classification of Tires Type tire Characteristic: Jet aircraft， high load-carrying ability,Ply rating: 4 to 38 Construction character: Low profile. Designating Method: Outside diameter, section width and rim diameter. 3011.50-14.5 tire: The outside diameter is 30 inches, The section width is 11.50 inches, The rim diameter is 14.5 inches.,Classification of Tires Designating Method: A Type VIII or three-part nomenclature tire is identified by 3 parameters: overall diameter, section width, and rim diameter. They are arranged in that order with the first two separated by an “X” and the second two separated by a “.” For example: 18 X 4.2510 designates a tire that is 18 inches in diameter with a 4.25-inch section width to be mounted on a 10- inch wheel rim.,Bias or Radial Tire Another means of classifying an aircraft tire is by the direction of the plies used in construction of the tire, either bias or radial. Traditional aircraft tires are bias ply tires. The plies are wrapped to form the tire and give it strength. The angle of the plies in relation to the direction of rotation of the tire varies between 30and 60.,Bias or Radial Tire In this manner, the plies have the bias of the fabric from which they are constructed facing the direction of rotation and across the tire. Hence, they are called bias tires. The result is flexibility as the sidewall can flex with the fabric plies laid on the bias.,Ply Rating It is just a strength index but in the past. Tires are given a ply rating, rather than specifying the actual number of layers of fabric material used in the carcass. The ply rating of a tire relates to its maximum static load and its inflation pressure.,Tube or Tubeless Tires Tubeless tires: one-tenth of an inch thick inner liner “TUBELESS”on the sidewall Tube tires: no inner liner, smoother inside surface. no “identification ” on the sidewall,Construction of Tire Automobile and truck tires 1. different specifications from those used for aircraft tires. 2. to operate for long periods of time. 3. a relatively large but steady load at reasonably high rotational speeds 4. a relatively small amount of deflection （变形）. Car Tires: a continual deflection of only about 12 to 14%.,Construction of Tire Airplane tires 1. strong enough to absorb the tremendous loads exerted on them at touchdown. 2. they must operate at very high speeds. 3. the ground roll duration is limited. 4. a deflection of between 32 and 35%, more than twice that allowed for automobile tires,BEAD（胎缘） The beads are made of bundles of high-strength carbon- steel wire, with one, two, or three of these bundles used in each side of the tire. The most important part of a tire. To provides a firm mounting surface for the tire on the wheel. All of the ground forces on the tire terminate in the bead. Figure 9-71,Rubber Apex Strips (橡胶填充层) Definition: To pack and streamline the round bead bundles, so the fabric will fit smoothly around them with no voids.,Flippers（隔离层） Definition: Layers of rubber and fabric enclose the bead bundles to insulate the carcass plies from the bead wires. Function: Because the greatest amount of heat in the tire is concentrated in the bead area, this insulation increases the durability of the tire.,CARCASS and TURN-UPS （胎体和重叠层） layers or plies of rubber-coated nylon-cord fabric. the cords of the fabric at an angle of approximately 450 to the length of the strip the strips extend completely across the tire and lap back over the beads to form the ply turn-ups. each successive ply of the fabric is placed in such a way that the cords cross each other at approximately 900 to balance the strength of the carcass.,CHAFERS （胎缘包覆层） Definition: Layers of fabric and rubber wrap around the edges of the carcass plies and enclose the entire bead area. Function: They provide chafe resistance between the bead and the wheel.,UNDERTREAD （底胎面） Definition: A plies of specially compounded rubber placed over the carcass. Function: To provide good adhesion between the tread and the carcass.,TREAD REINFORCING LAYER （胎面加强层） Definition: One or more plies of nylon fabric strengthens the tread. Function: 1. to opposes the centrifugal forces that try to pull the tread from the carcass during high-speed operation.,TREAD REINFORCING LAYER （胎面加强层） 2. It also stabilizes the tread on the cord body and prevents it from squirming（蠕动) or moving. 3. This reinforcement does not enter into the ply rating of the tire, but it is used as a guide for the retreader when buffing the tire to remove the tread.,TUBELESS TIRE LINER （无内胎轮胎衬层） Definition: A special compound of rubber that is less permeable than the rubber used in the rest of the tire. a thin coating of rubber over the inner ply cords protects the liner from chafing. Function: The liner acts as a container for the air and minimizes the amount of air that seeps out through the casing plies.,TREAD （胎面） Definition: The wearing surface on the outer circumference of the tire. Characteristic: 1. It is made of specially compounded rubber. 2. A pattern of grooves molded into its surface to give the tire the required traction (附着力） according to the type of runway surface the aircraft will encounter.,TREAD PATTERNS Plain Tread Plain, or smooth, tread is used on some helicopter and on very light airplanes. All weather tread 1. All-weather treads have a rib tread in the center and diamonds molded into the shoulders 2. The diamond-shaped tread pattern is effective for aircraft operating on grass or hard-packed dirt, and the rib tread in the center gives good traction on hard surfaced runways【Figure 9-72,Rib Tread The rib tread is the most popular tread pattern found on modern aircraft today. 1. use on hard-surfaced runways. 2. long tread wear life 3. good traction 4. exceptionally good directional stability. Figure 9-73 The width and depth of the grooves , their placement on the tread are determined by operating conditions of aircraft for which they are designed.,CHINE(胎脊、偏转器） Chines or deflectors molded into the upper sidewall of tire on the nose wheel. Tires for dual nose wheel installations have chines on one side only, Single nose wheel installations have dual chines (deflectors)，one on either side of the tireFigure 9-74 Function: To prevent water or slush from being thrown up by the nose wheel and entering the engines， Figure 9-74,SIDEWALL Definition: A rubber covering that extends from the tread down to the bead heel Function: To protect the carcass from injuries such as cuts or bruises and from exposure to moisture and ozone.,VENT HOLES Definition: Vent holes in the lower sidewall to allow the air seeping into sidewall to escape. These holes are marked with paint and must be kept open when the tire is retreaded. Function: When the tire was heated, to avoid ply separation and the tread to be thrown from the tire.,TIRE INSPECTION ON THE AIRCRAFT Most inspection on the aircraft Scheduled inspections of the tires The technician should take a look at the tires any time work is being done in the vicinity of the gear.,轮胎充气的基本要求 1. 如果将轮胎始终维持在正确压力，轮胎寿命会更长。 2. 如果用干燥的空气给轮胎充气，确保氧气含量不超过5%。 3. 如果轮胎压力比正确压力低5%或更低，则为轮胎充气。 4. 如果轮胎压力比正常压力低5%15%，给轮胎充气并在24 小 时后检查。 5. 如果轮胎压力比正常压力低1530%，拆卸并更换机轮和轮胎组件。 6. 如果轮胎压力比正常压力低超过30%，拆卸并更换机轮和轮胎组件。如果轮胎在压力下降后机轮转动并承担飞机重量，更换安装在轮轴对侧的机轮和轮胎组件。,Heat Damage The greatest enemy of an aircraft tire is heat. Heat resource: 1. The heat generated within the tire as it rolls over the ground, the sidewalls flex and cause internal heat 2. The heat from external sources such as the brakes or hot runway surfaces.,Inflation Pressure 1. The pressure should be checked Daily inspection Preflight inspection 2. Differences in air pressure between dual mounted tires should cause concern. It defeats the purpose of dual mounted tires 3. Any pressure difference should be corrected and noted in the aircraft logbook. Consult the aircraft service manual to determine the exact tire pressure tolerances.,Inflation Pressure Inflation pressure should always be measured when the tire is cold. Two to three hours should elapse after a flight or before the pressure is measured. Tire pressure check is the most important parts of routine preventive maintenance. The pressure in the aircraft service manual, rather than that listed in the tire manufacturers product manuals. Reason: tire pressures vary from one aircraft design to another.,Inflation Pressure The pressure specified in the airframe manufacturers manual is for a loaded tire, If serviced and inflated off the aircraft, the inflation pressure should be four percent less than the pressure specified. ( 180psi, 187psi in the AMM) Pressure gauges should be periodically calibrated. Inflation pressure of a tire varies with the ambient temperature by about one percent for every five degrees Fahrenheit.,Inflation Pressure 1. If a tire is inflated and allowed to stabilize with a pressure of 180 psi in a shop where the temperature is 70F. 2. And the airplane is rolled outside where it remains overnight with a temperature of 0F, the pressure will drop by 14% to about 155 psi. 3. Obviously, tire would then be seriously under-inflated and should be reinflated to 180 psi.,Inflation Pressure An airplane is to fly into an area where the temperature is much lower than that of the departing point. Theoretically, the pressure should be adjusted before the airplane leaves. 1. The temperature at the departing airport is 100F . 2. The airplane is to land at the another airport where the temperature is 40F. 3. The pressure should be increased before takeoff.,Inflation Pressure 4. If the tire requires 187 psi, the 60F temperature drop will require the pressure to be 12greater, or 210 psi. The maximum allowable safe-inflation pressure in AMM could not been exceeded. Nylon tire will stretch and increase their volume enough to cause pressure drop after they are first inflated. The pressures should be adjusted 12 to 24 hours after first installation. Conclusion: Every 5F temperature drop will require the inflation pressure to be increased 5.,Over-inflation It causes more centerline wear on the tread than that on the shoulder. When a tire is worn in this way, it has much less resistance to skidding than when its tread wears uniformly.,Over-inflation,Under-inflation It causes over deflection Excess heat within the tire. (45% deflection, three times heat builds up in tire) Tread worn away on the shoulders more than in the center. Tires showing this pattern of wear should be carefully examined for evidence of hidden damage.,Under-inflation,TREAD CONDITION Basic strength of a tire is determined by its carcass, a tire loses nothing of its strength as long as the tread does not wear down to the body plies. It should be removed for retreading while there is still at least 1/32-inch of tread left at its most shallow point.,Correct Inflation Pressure Normal Wear The correct inflation pressure will wear the tread uniformly. Figure 9-76,Abnormal Wear of Tire Tread 1. Uneven tread wear Cause: the landing gear is out of alignment. Measures: Wheel alignment should be checked so it conforms to the specifications of the aircraft service manual. If the uneven wear is slight and the landing gear is not adjusted, the tires may be removed, carefully inspected, and reversed so the wear will even out.,Abnormal Wear of Tire Tread 2 Tread wear in spots Cause: malfunctioning brakes improperly torqued bearings worn strut parts landing with brakes engaged.,Tread cut A tire should be removed form service if the tread is cut across more than one-half of a rib width Cause: glass, rock, or metal Figure 9-80 grooved runway Figure 9-82 Note: remove glass, rock, or metal with a blunt awl or screwdriver.,Tread burn A tire should be removed form service if the tread shows the burning mark on the contact point with the runway or water on the runway. Figure 9-81 Cause: hydroplaning (打滑） a locked brake,Inspection of Tread 1. If the cord body plies are visible, the tire cannot be retrodden. Figure 9-79 2. If the tread reinforcement just is showing, the tires are possibly retrodden. 3. Any time the tread is cut more than halfway across a rib，or any of the carcass plies are exposed，the tire should be removed from serviceFigure 9-80,Inspection of Tread 4. bits of glass, rock or metal embedded in the tread should be carefully removed with a blunt awl or a small screwdriver. 5. Tires showing burn at the point of contact should be removed from service. 6. Operating on grooved runways can cause chevron-shaped (V-shape) cuts across the ribs of a tire. If they extend across more than one-half of the rib, the tire should be removed from service.,Inspection of Tread 7. Any damaged or suspect area of the tire should be marked with a light-colored marker before deflating the tire. 8. Any tread damage should be carefully evaluated by a licensed retreading agency to determine whether or not the tire is repairable.,Sidewall Purpose: It protects the carcass plies from damage, either from mechanical abrasion, from deterioration by chemicals，or by the sun. 1. if small snags, cuts , weather cracks dont expose the cords, the tire should not be removed for maintenance. 2. Check for open holes on the sidewall. The vent is used to relieve the air diffused into the body plies from the tire compartment in order to protect the plies from separation.,Procedure of Tire Removal 1. jack the aircraft up. 2. when the weight is off, deflate the tire using a deflator cap. 3. removed the cover of inflation valve. 4. remove the wheel. 5. clean, inspection and repack the bearings with proper grease, protect it from damage.,Procedure of Tire Removal 6. put the wheel on a flat surface, the bead separated from the bead seat area of the wheel using a straight push as near to the rim as possible. Figure 9-83 Caution: No kind of tire tool should be used to pry the bead from the wheel, because the wheel can become nicked or scratched- stress concentrations at the point of the nick or scratch that could lead to wheel failure.,Procedure of Tire Removal 8. remove the wheel bolts, then remove the wheel halves from the tire. 9. for the tubeless tire, the O-ring between the wheel halves should be inspected for damage.,Replacement of Tire 1. Aborted take-off 2. Severe brakes 3. The fusible plug has melted and the tire was deflated. 4. If one tire in a dual installation fails, another one should be replaced at the same time.,Inspection of Inner Liner cracks bulges or blisters（凸起） Caution: 1. bead should not be spread more than the section width of the tire. 2. force used to spread the beads should not be concentrated in one area. 3. improper spreading method can kink（纽结） the wire bundles and the tire must be scrapped.,Inspection of the marked area 1. inflate the tire 2. cuts should be opened up enough to check the depth. 3. Punctures that do not exceed one-quarter inch on the outside of the tire, one-eighth inch on the inside, never puncture the tire.,Inspection of Bead & Adjacent Area 1. Severe damage from tire tools and chafing the rim. 2. Damage from excessive heat such as an unusual appearance or texture.,Rejection of Tire The following tires must be scraped: Any evidence of breaks caused by flexing（弯曲）. This type of damage is often associated with other damage that may not be visible. Bead damage to more than the chafers, or any damage that would prevent the bead of a tubeless tire from sealing to the wheel. Any evidence of separation between the plies around the bead wire.,Rejection of Tire The following tires must be scraped: Any injury that would require a reinforcement. Kinked or broken beads. Weather cracks or radial cracks in the sidewall that extend into the cord body. Blisters or other evidence of heat damage. Cracked, deteriorated, or damaged inner liners of tubeless tires.,Storage of Tire All new and retreaded tires should be stored in a cool, dry area, out of direct sunlight and away from any electrical machinery (Ozone damage). The temperature should be kept between 32 F and 80F. The tires should be stored vertically in special racks with the tire supported on a flat surface which is at least three or four inches wide.,Storage of Tire Stack tire horizontally: 1. they should not be stacked more than five tires high for tires with a diameter of up to 40 inches. 2. not more than four tires high for those with a diameter between 40 and 49 inches. 3. not more than three high for tires with a diameter larger than 49 inches. Figure 9-84,Aircraft tubes Two type: 1. Unreinforced rubber tube for normal application. 2. Special heavy-duty reinforced tube include a layer of nylon fabric molded to inside circumference to protect it from chafing against the rim and from heat caused by brake application. Material: a specially compounded natural rubber Leakage causes: A hole or defective valve,Tube Inspection Leakage: spread a drop of water over the end of the valve to check if the core is perfect. if the leak is not in the valve, the tube must be removed, inflated and put into a water container to check for leakage as following:,Tube Inspection 1. when inflating a tire that is not in a tire, only enough air is used to round it out. 2. check t