Appendix 1 to ETSO-C135a - Minimum Performance Specification for Large Aeroplane Wheels, Brakes, and Wheel and Brake Assemblies

• ED Decision 2010/010/R found in: CS-ETSO Amdt 17 - European Technical Standard Orders (Oct 2026)

###### Appendix 1 to ETSO-C135a – Minimum Performance Specification for Large Aeroplane Wheels, Brakes, and Wheel and Brake Assemblies *ED Decision 2010/010/R* **CHAPTER 1** **INTRODUCTION** 1.1 PURPOSE AND SCOPE. This Minimum Performance Specification defines the minimum performance standards for wheels, brakes, and wheel and brake assemblies to be used on aeroplanes certificated under CS-25. Compliance with this specification is not considered approval for installation on any large aeroplane. 1.2 APPLICATION. Compliance with this minimum specification by the applicant is required as a means of assuring that the equipment will have the capability to satisfactorily perform its intended function(s). Note: Certain performance capabilities may be affected by aeroplane operational characteristics and other external influences. Consequently, anticipated aeroplane braking performance should be verified by aeroplane testing. 1.3 COMPOSITION OF EQUIPMENT. The words “equipment” or “brake assembly” or “wheel assembly,” as used in this document, include all components that form part of the particular unit. For example, a wheel assembly typically includes a hub or hubs, bearings, flanges, drive bars, heat shields, and fuse plugs. A brake assembly typically includes a backing plate, torque tube, cylinder assemblies, pressure plate, heat sink, and temperature sensor. It should not be inferred from these examples that each wheel assembly and brake assembly will necessarily include either all or any of the above example components; the actual assembly will depend on the specific design chosen by the applicant. 1.4 DEFINITIONS AND ABBREVIATIONS. 1.4.1 Brake Lining. Brake lining is individual blocks of wearable material, discs that have wearable material integrally bonded to them, or discs in which the wearable material is an integral part of the disc structure. 1.4.2 BROPMAX - Brake Rated Maximum Operating Pressure. BROPMAX is the maximum design metered pressure that is available to the brake to meet aeroplane stopping performance requirements. 1.4.3 BRPMAX - Brake Rated Maximum Pressure. BRPMAX is the maximum pressure to which the brake is designed to be subjected (typically aeroplane nominal maximum system pressure). 1.4.4 BRPRET - Brake Rated Retraction Pressure. BRPRET is the pressure to which the brake inlet pressure must be reduced to cause full piston retraction after a brake is sufficiently pressurised to extend all pistons. 1.4.5 BRPPMAX - Brake Rated Maximum Parking Pressure. BRPPMAX is the maximum parking pressure available to the brake. 1.4.6 BRWL - Brake Rated Wear Limit. BRWL is the brake maximum wear limit to ensure compliance with paragraph 3.3.3, and, if applicable, paragraph 3.3.4 of this Appendix 1. 1.4.7 D - Distance Averaged Deceleration. D = ( (Initial brakes-on speed)2- (Final brakes-on speed)2)/(2 (braked flywheel distance)). D is the distance averaged deceleration to be used in all deceleration calculations. 1.4.8 DDL - Rated Design Landing Deceleration. DDL is the minimum of the distance averaged decelerations demonstrated by the wheel, brake and tyre assembly during the 100 KEDL stops in paragraph 3.3.2 of this Appendix 1. 1.4.9 DRT - Rated Accelerate-Stop Deceleration. DRT is the minimum of the distance averaged decelerations demonstrated by the wheel, brake, and tyre assembly during the KERT stops in paragraph 3.3.3 of this Appendix 1. 1.4.10 DSS - Rated Most Severe Landing Stop Deceleration. DSS is the distance averaged deceleration demonstrated by the wheel, brake and tyre assembly during the KESS Stop in paragraph 3.3.4 of this Appendix 1. 1.4.11 Heat Sink. The heat sink is the mass of the brake that is primarily responsible for absorbing energy during a stop. For a typical brake, this would consist of the stationary and rotating disc assemblies. 1.4.12 KEDL - Wheel/Brake Rated Design Landing Stop Energy. KEDL is the minimum energy absorbed by the wheel/brake/tyre assembly during every stop of the 100 stop design landing stop test. (paragraph 3.3.2 of this Appendix 1). 1.4.13 KERT - Wheel/Brake Rated Accelerate-Stop Energy. KERT is the energy absorbed by the wheel/brake/tyre assembly demonstrated in accordance with the accelerate-stop test in paragraph 3.3.3 of this Appendix 1. 1.4.14 KESS - Wheel/Brake Rated Most Severe Landing Stop Energy. KESS is the energy absorbed by the wheel/brake/tyre assembly demonstrated in accordance with paragraph 3.3.4 of this Appendix 1. 1.4.15 L - Wheel Rated Radial Limit Load. L is the wheel rated maximum radial limit load (paragraph 3.2.1 of this Appendix 1). 1.4.16 R - Wheel Rated Tyre Loaded Radius. R is the static radius at load “S” for the wheel rated tyre size at WRP. The static radius is defined as the minimum distance from the axle centreline to the tyre/ground contact interface. 1.4.17 S -Wheel Rated Static Load. S is the maximum static load (Reference CS 25.731(b)). 1.4.18 STR - Wheel/Brake Rated Structural Torque. STR is the maximum structural torque demonstrated (paragraph 3.3.5 of this Appendix 1). 1.4.19 TSBR - Brake Rated Tyre Type(s) and Size(s). TSBR is the tyre type(s) and size(s) used to achieve the KEDL, KERT, and KESS brake ratings. TSBR must be a tyre type and size approved for installation on the wheel (TSWR). 1.4.20 TSWR - Wheel Rated Tyre Type(s) and Size(s). TSWR is the wheel rated tyre type(s) and Size(s) defined for use and approved by the aeroplane manufacturer for installation on the wheel. 1.4.21 TTBT - Suitable Tyre for Brake Tests. TTBT is the rated tyre type and size. TTBT is the tyre type and size that has been determined as being the most critical for brake performance and/or energy absorption tests. The TTBT must be a tyre type and size approved for installation on the wheel (TSWR). The suitable tyre may be different for different tests. 1.4.22 TTWT - Suitable Tyre for Wheel Test. TTWT is the wheel rated tyre type and size for wheel test. TTWT is the tyre type and size determined as being the most appropriate to introduce loads and/or pressure that would induce the most severe stresses in the wheel. TTWT must be a tyre type and size approved for installation on the wheel (TSWR). The suitable tyre may be different for different tests. 1.4.23 VDL - Wheel/Brake Design Landing Stop Speed. VDL is the initial brakes-on speed for a design landing stop (paragraph 3.3.2 of this Appendix 1). 1.4.24 VR - Aeroplane Maximum Rotation Speed. 1.4.25 VRT - Wheel/Brake Accelerate-Stop Speed. VRT is the initial brakes-on speed used to demonstrate KERT (paragraph 3.3.3 of this Appendix 1). 1.4.26 VSS - Wheel/Brake Most Severe Landing Stop Speed. VSS is the initial brakes-on speed used to demonstrate KESS (paragraph 3.3.4 of this Appendix 1). 1.4.27 WRP - Wheel Rated Inflation Pressure. WRP is the wheel rated inflation pressure (wheel unloaded). **CHAPTER 2** **GENERAL DESIGN SPECIFICATION** 2.1 AIRWORTHINESS. The continued airworthiness of the wheels (without brakes) and wheel and brake assemblies must be considered. See chapter 4 of this Appendix 1, titled “DATA REQUIREMENTS”. 2.2 FIRE PROTECTION. Except for small parts (such as fasteners, seals, grommets, and small electrical parts) that would not contribute significantly to the propagation of a fire, all solid materials used must be self-extinguishing. See also paragraphs 2.4.5, 3.3.3.5 and 3.3.4.5 of this Appendix 1. 2.3 DESIGN. Unless shown to be unnecessary by test or analysis, the equipment must comply with the following: 2.3.1 Lubricant Retainers. Lubricant retainers must retain the lubricant under all operating conditions, prevent the lubricant from reaching braking surfaces, and prevent foreign matter from entering the lubricated cavity. 2.3.2 Removable Flanges. All removable flanges must be assembled onto the wheel in a manner that will prevent the removable flanges and retaining devices from leaving the wheel if a tyre deflates while the wheel is rolling. 2.3.3 Adjustment. The brake mechanism must be equipped with suitable adjustment devices to maintain appropriate running clearance when subjected to BRPRET. 2.3.4 Water Seal. Wheels intended for use on amphibious aircraft must be sealed to prevent entrance of water into the wheel bearings or other portions of the wheel or brake, unless the design is such that brake action and service life will not be impaired by the presence of sea water or fresh water. 2.3.5 Burst Prevention. Means must be provided to prevent wheel failure and tyre burst that might result from over- pressurisation or from elevated brake temperatures. The means must take into account the pressure and the temperature gradients over the full operating range. 2.3.6 Wheel Rim and Inflation Valve. Tyre and Rim Association (Reference: Aircraft Year Book-Tyre and Rim Association Inc.) or, The European Tyre and Rim Technical Organisation (Reference: Aircraft Tyre and Rim Data Book) approval of the rim dimensions and inflation valve is encouraged. 2.3.7 Brake Piston Retention. The brake must incorporate means to ensure that the actuation system does not allow hydraulic fluid to escape if the limits of piston travel are reached. 2.3.8 Wear Indicator. A reliable method must be provided for determining when the heat sink is worn to its permissible limit. 2.3.9 Wheel Bearings. Means should be incorporated to avoid mis-assembly of wheel bearings. 2.3.10 Fatigue. The design of the wheel must incorporate techniques to improve fatigue resistance of critical areas of the wheel and minimise the effects of the expected corrosion and temperature environment. The wheel must include design provisions to minimise the probability of fatigue failures that could lead to flange separation or other wheel burst failures. 2.3.11 Dissimilar Materials. When dissimilar materials are used in the construction and the galvanic potential between the materials indicate galvanic corrosion is likely, effective means to prevent the corrosion must be incorporated in the design. In addition, differential thermal expansion must not unduly affect the functioning, load capability, and the fatigue life of the components. 2.4 CONSTRUCTION. The suitability and durability of the materials used for components must be established on the basis of experience or tests. In addition, the materials must conform to approved specifications that ensure the strength and other properties are those that were assumed in the design. 2.4.1 Castings. Castings must be of high quality, clean, sound, and free from blowholes, porosity, or surface defects caused by inclusions, except that loose sand or entrapped gases may be allowed when serviceability is not impaired. 2.4.2 Forgings. Forgings must be of uniform condition, free from blisters, fins, folds, seams, laps, cracks, segregation, and other defects. Imperfections may be removed if strength and serviceability would not be impaired as a result. 2.4.3 Bolts and Studs. When bolts or studs are used for fastening together sections of a wheel or brake, the length of the threads must be sufficient to fully engage the nut, including its locking feature, and there must be sufficient unthreaded bearing area to carry the required load. 2.4.4 Environmental Protection. All the components used must be suitably protected against deterioration or loss of strength in service due to any environmental cause, such as weathering, corrosion, and abrasion. 2.4.5 Magnesium Parts. Magnesium and alloys having magnesium as a major constituent must not be used on brakes or braked wheels. **CHAPTER 3** **MINIMUM PERFORMANCE UNDER STANDARD TEST CONDITIONS.** 3.1 INTRODUCTION. The test conditions and performance criteria described in this chapter provide a laboratory means of demonstrating compliance with this ETSO minimum performance standard. The aeroplane manufacturer normally defines relevant test parameter values, however these may also be derived from published aircraft data for applicants for supplementary type certificates (STC). 3.2 WHEEL TESTS. To establish the ratings for a wheel, it must be substantiated that standard production wheel samples will meet the following radial load, combined load, roll load, roll-on-rim (if applicable) and overpressure test requirements. For all tests, except the roll-on-rim test in paragraph 3.2.4 of this Appendix 1, the wheel must be fitted with a suitable tyre, TTWT, and wheel loads must be applied through the tyre. The ultimate load tests in paragraphs 3.2.1.3 and 3.2.2.3 of this Appendix 1 provide for an alternative method of loading if it is not possible to conduct these tests with the tyre mounted. 3.2.1 Radial Load Test. If the radial limit load of paragraph 3.2.2 of this Appendix 1 is equal to or greater than the radial limit load in this paragraph, the test specified in this paragraph may be omitted. Test the wheel for yield and ultimate loads as follows: 3.2.1.1 Test method. With a suitable tyre, TTWT, installed, mount the wheel on its axle, and position it against a flat, non-deflecting surface. The wheel axle must have the same angular orientation to the non-deflecting surface that it will have to a flat runway when it is mounted on an aeroplane and is under the maximum radial limit load, L. Inflate the tyre to the pressure recommended for the Wheel Rated Static Load, S, with gas and/or liquid. If liquid inflation is used, liquid must be bled off to obtain the same tyre deflection that would result if gas inflation were used. Liquid pressure must not exceed the pressure that would develop if gas inflation were used and the tyre was deflected to its maximum extent. Load the wheel through its axle with the load applied perpendicular to the flat, non-deflecting surface. Deflection readings must be taken at suitable points to indicate deflection and permanent set of the wheel rim at the bead seat. 3.2.1.2 Yield Load. Apply to the wheel and tyre assembly a load not less than 1·15 times the maximum radial limit load, L, reference CS 25.471 through 25.511, as appropriate. Determine the most critical wheel orientation with respect to the non-deflecting surface. Apply the load with the tyre loaded against the non-deflecting surface, and with the wheel rotated 90 degrees with respect to the most critical orientation. Repeat the loading with the wheel 180, 270, and 0 degrees from the most critical orientation. The bearing cups, cones, and rollers used in operation must be used for these loadings. If at a point of loading during the test bottoming of the tyre occurs, then the tyre pressure may be increased an amount sufficient only to prevent bottoming. Three successive loadings at the 0 degree position must not cause permanent set increments of increasing magnitude. The permanent set increment caused by the last loading at the 0 degree position may not exceed 5 percent of the deflection caused by that loading or 0·005 inches (0·125mm), whichever is greater. There must be no yielding of the wheel such as would result in loose bearing cups, liquid or gas leakage through the wheel or past the wheel seal. 3.2.1.3 Ultimate Load. Apply to the wheel used in the yield test in paragraph 3.2.1.2 of this Appendix 1, and the tyre assembly, a load not less than 2 times the maximum radial limit load, L, for castings, and 1.5 times the maximum radial limit load, L, for forgings. Reference CS 25.471 through 25.511, as appropriate. Apply the load with the tyre and wheel against the non-deflecting surface and the wheel positioned at 0 degree orientation (paragraph 3.2.1.2 of this Appendix 1). The bearing cones may be replaced with conical bushings, but the cups used in operation must be used for this loading. If, at a point of loading during the test, it is shown that the tyre will not successfully maintain pressure or if bottoming of the tyre occurs, the tyre pressure may be increased. If bottoming of the tyre continues to occur with increased pressure, then a loading block that fits between the rim flanges and simulates the load transfer of the inflated tyre may be used. The arc of the wheel supported by the loading block must be no greater than 60 degrees. The wheel must support the load without failure for at least 3 seconds. Abrupt loss of load-carrying capability or fragmentation during the test constitutes failure. 3.2.2 Combined Radial and Side Load Test. Test the wheel for the yield and ultimate loads as follows: 3.2.2.1 Test Method. With a suitable tyre, TTWT, installed, mount the wheel on its axle and position it against a flat, non-deflecting surface. The wheel axle must have the same angular orientation to the non-deflecting surface that it will have to a flat runway when it is mounted on an aeroplane and is under the combined radial and side limit loads. Inflate the tyre to the pressure recommended for the maximum static load with gas and/or liquid. If liquid inflation is used, liquid must be bled off to obtain the same tyre deflection that would result if gas inflation were used. For the radial load component, load the wheel through its axle with load applied perpendicular to the flat non deflecting surface. Apply the two loads simultaneously, increasing them either continuously or in increments no greater than 10 percent of the total loads to be applied. If it is impossible to generate the side load because of friction limitations, the radial load may be increased, or a portion of the side load may be applied directly to the tyre/wheel. In such circumstances it must be demonstrated that the moment resulting from the side load is no less severe than would otherwise have occurred. Alternatively, the vector resultant of the radial and side loads may be applied to the axle. Deflection readings must be taken at suitable points to indicate deflection and permanent set of the wheel rim at the bead seat. 3.2.2.2 Combined Yield Load. Apply to the wheel and tyre assembly radial and side loads not less than 1·15 times the respective ground limit loads, reference CS 25.485, 25.495, 25.497, and 25.499, as appropriate. If at a point of loading during the test bottoming of the tyre occurs, then the tyre pressure may be increased an amount sufficient only to prevent bottoming. Determine the most critical wheel orientation with respect to the non-deflected surface. Apply the load with the tyre loaded against the non-deflecting surface, and with the wheel rotated 90 degrees with respect to the most critical orientation. Repeat the loading with the wheel 180, 270, and 0 degrees from the most critical orientation. The bearing cups, cones, and rollers used in operation must be used in this test. A tube may be used in a tubeless tyre only when it has been demonstrated that pressure will be lost due to the inability of a tyre bead to remain properly positioned under the load. The wheel must be tested for the most critical inboard and outboard side loads. Three successive loadings at the 0 degree position must not cause permanent set increments of increasing magnitude. The permanent set increment caused by the last loadings at the 0 degree position must not exceed 5 percent of the deflection caused by the loading, or 0·005 inches (0·125mm), whichever is greater. There must be no yielding of the wheel such as would result in loose bearing cups, gas or liquid leakage through the wheel or past the wheel seal. 3.2.2.3 Combined Ultimate Load. Apply to the wheel, used in the yield test of paragraph 3.2.2.2 of this Appendix 1, radial and side loads not less than 2 times for castings and 1·5 times for forgings, the respective ground limit loads reference CS 25.485, 25.495, 25.497, and 25.499, as appropriate. Apply these loads with a tyre and wheel against the non-deflecting surface and the wheel oriented at the 0 degree position (paragraph 3.2.2.2 of this Appendix 1). The bearing cones may be replaced with conical bushings, but the cups used in operation must be used for this loading. If at any point of loading during the test it is shown that the tyre will not successfully maintain pressure, or if bottoming of the tyre on the non-deflecting surface occurs, the tyre pressure may be increased. If bottoming of the tyre continues to occur with this increased pressure, then a loading block that fits between the rim flanges and simulates the load transfer of the inflated tyre may be used. The arc of wheel supported by the loading block must be no greater than 60 degrees. The wheel must support the loads without failure for at least 3 seconds. Abrupt loss of load-carrying capability or fragmentation during the test constitutes failure. 3.2.3 Wheel Roll Test. 3.2.3.1 Test Method. With a suitable tyre, TTWT, installed, mount the wheel on its axle and position it against a flat non-deflecting surface or a flywheel. The wheel axle must have the same angular orientation to the non-deflecting surface that it will have to a flat runway when it is mounted on an aeroplane and is under the Wheel Rated Static Load, S. During the roll test, the tyre pressure must not be less than 1·14 times the Wheel Rated Inflation Pressure, WRP, (0·10 to account for temperature rise and 0·04 to account for loaded tyre pressure). For side load conditions, the wheel axle must be yawed to the angle that will produce a wheel side load component equal to 0·15 S while the wheel is being roll tested. 3.2.3.2 Roll Test. The wheel must be tested under the loads and for the distances shown in Table 3-1. ***TABLE 3-1 Load Conditions and Roll Distances for Roll Test*** <table bgcolor="#d9d9d9" cellpadding="7" cellspacing="0"> <col/> <col/> <tr valign="top"> <td bgcolor="#808080"><p align="center"> <b>Load Conditions</b></p> </td> <td bgcolor="#808080"><p align="center"> <b>Roll Distance Miles (km)</b></p> </td> </tr> <tr valign="top"> <td bgcolor="#d9d9d9"><p align="left"> Wheel Rated Static Load, S</p> </td> <td bgcolor="#d9d9d9"><p align="center"> 2 000 (3 220)</p> </td> </tr> <tr valign="top"> <td bgcolor="#d9d9d9"><p align="left"><a name="_Hlk83979722"></a> Wheel Rated Static Load, S, plus a 0·15xS side load applied in the outboard direction</p> </td> <td bgcolor="#d9d9d9"><p align="center"> 100 (161)</p> </td> </tr> <tr valign="top"> <td bgcolor="#d9d9d9"><p align="left"> Wheel Rated Static Load, S, plus a 0·15xS side load applied in the inboard direction</p> </td> <td bgcolor="#d9d9d9"><p align="center"> 100 (161)</p> </td> </tr> </table> At the end of the test, the wheel must not be cracked, there must be no leakage through the wheel or past the wheel seal(s), and the bearing cups must not be loose. 3.2.4 Roll-on-Rim Test (not applicable to nose wheels). The wheel assembly without a tyre must be tested at a speed of no less than 10 mph (4·6 m/s) under a load equal to the Wheel Rated Static Load, S. The test roll distance (in feet) must be determined as 0·5VR2 but need not exceed 15,000 feet (4,572 meters). The test axle angular orientation with the load surface must represent that of the aeroplane axle to the runway under the static load S. The wheel assembly must support the load for the distance defined above. During the test, no fragmentation of the wheel is permitted; cracks are allowed. 3.2.5 Overpressure Test. The wheel assembly, with a suitable tyre, TTWT, installed, must be tested to demonstrate that it can withstand the application of 4·0 times the wheel rated inflation pressure, WRP. The wheel must retain the pressure for at least 3 seconds. Abrupt loss of pressure containment capability or fragmentation during the test constitutes failure. Plugs may be used in place of over-pressurisation protection device(s) to conduct this test (reference CS 25.731(d)). 3.2.6 Diffusion Test. A tubeless tyre and wheel assembly must hold its rated inflation pressure, WRP, for 24 hours with a pressure drop no greater than 5 percent. This test must be performed after the tyre growth has stabilised. 3.3 WHEEL AND BRAKE ASSEMBLY TESTS. 3.3.1 General. 3.3.1.1 The wheel and brake assembly, with a suitable tyre, TTBT, installed, must be tested on a testing machine in accordance with the following, as well as paragraphs 3.3.2, 3.3.3, 3.3.5 and, if applicable, 3.3.4 of this Appendix 1. 3.3.1.2 For tests detailed in paragraphs 3.3.2, 3.3.3, and 3.3.4 of this Appendix 1, the test energies KEDL, KERT, and KESS and brake application speeds VDL, VRT, and VSS are as normally defined by the aeroplane manufacturer. 3.3.1.3 For tests detailed in paragraphs 3.3.2, 3.3.3, and 3.3.4 of this Appendix 1, the initial brake application speed must be as close as practicable to, but not greater than, the speed established in accordance with paragraph 3.3.1.2 of this Appendix 1, with the exception that marginal speed increases are allowed to compensate for brake pressure release permitted in paragraphs 3.3.3.4 and 3.3.4.4 of this Appendix 1. An increase in the initial brake application speed is not a permissible method of accounting for a reduced (i.e., lower than ideal) dynamometer mass. This method is not permissible because, for a target test deceleration, a reduction in the energy absorption rate would result, and could produce performance different from that which would be achieved with the correct brake application speed. The energy to be absorbed during any stop must not be less than that established in accordance with paragraph 3.3.1.2 of this Appendix 1. Additionally, forced air or other artificial cooling means are not permitted during these stops. 3.3.1.4 The brake assembly must be tested using the fluid (or other actuating means) specified for use with the brake on the aeroplane. 3.3.2 Design Landing Stop Test. 3.3.2.1 The wheel and brake assembly under test must complete 100 stops at the KEDL energy, each at the mean distance averaged deceleration, D, normally defined by the aeroplane manufacturer, but not less than 10 ft/s2 (3·05 m/s2). (Reference CS 25.735(f)(1)). 3.3.2.2 During the design landing stop test, the disc support structure must not be changed if it is intended for reuse, or if the wearable material is integral to the structure of the disc. One change of individual blocks or integrally bonded wearable material is permitted. For discs using integrally bonded wearable material, one change is permitted, provided that the disc support structure is not intended for reuse. The remainder of the wheel/brake assembly parts must withstand the 100 KEDL stops without failure or impairment of operation. 3.3.3 Accelerate-Stop Test. 3.3.3.1 The wheel and brake assembly under test must complete the accelerate-stop test at the mean distance averaged deceleration, D, normally defined by the aeroplane manufacturer, but not less than 6 ft/s2 (1·83 m/s2). (Reference CS 25.735(f)(2)). This test establishes the maximum accelerate-stop energy rating, KERT, of the wheel and brake assembly using: a. The Brake Rated Maximum Operating Pressure, BROPMAX; or b. The maximum brake pressure consistent with the aeroplane’s braking pressure limitations (e.g. tyre/runway drag capability based on substantiated data). 3.3.3.2 For the accelerate-stop test, the tyre, wheel, and brake assembly must be tested at KERT for both a new brake and a fully worn brake. a. A new brake is defined as a brake on which less than 5 percent of the usable wear range of the heat sink has been consumed. b. A worn brake is defined as a brake on which the usable wear range of the heat sink has already been fully consumed to BRWL. The proportioning of wear through the brake for the various friction pairs for this test must be based on service wear experience or wear test data of an equivalent or similar brake. Either operationally worn or mechanically worn brake components may be used. If mechanically worn components are used, it must be shown that they can be expected to provide similar results to operationally worn components. The test brake must be subjected to a sufficient number and type of stops to ensure that the brake’s performance is representative of in-service use; at least one of these stops, with the brake near the fully worn condition, must be a design landing stop. 3.3.3.3 At the time of brake application, the temperatures of the tyre, wheel, and brake, particularly the heat sink, must, as closely as practicable, be representative of a typical in-service condition. Preheating by taxi stops is an acceptable means. These temperatures must be based on a rational analysis of a braking cycle, taking into account a typical brake temperature at which an aeroplane may be dispatched from the ramp, plus a conservative estimate of heat sink temperature change during subsequent taxiing and takeoff acceleration, as appropriate. Alternatively, in the absence of a rational analysis, the starting heat sink temperature must be that resulting from the application of 10 percent KERT to the tyre, wheel and brake assembly, initially at not less than normal ambient temperature (59°F/15°C). 3.3.3.4 A full stop demonstration is not required for the accelerate-stop test. The test brake pressure may be released at a test speed of up to 23 mph (10 m/s). In this case, the initial brakes-on speed must be adjusted such that the energy absorbed by the tyre, wheel and brake assembly during the test is not less than the energy absorbed if the test had commenced at the specified speed and continued to zero ground speed. 3.3.3.5 Within 20 seconds of completion of the stop, or of the brake pressure release in accordance with paragraph 3.3.3.4 of this Appendix 1, the brake pressure must be adjusted to the Brake Rated Maximum Parking Pressure, BRPPMAX, and maintained for at least 3 minutes (Reference CS 25.735(g)). No sustained fire that extends above the level of the highest point of the tyre is allowed before 5 minutes have elapsed after application of parking brake pressure; until this time has elapsed, neither fire fighting means nor coolants may be applied. The time of initiation of tyre pressure release (e.g., by wheel fuse plug), if applicable, is to be recorded. The sequence of events described in paragraphs 3.3.3.4 and 3.3.3.5 of this Appendix 1 is illustrated in figure 3-1. 3.3.4 Most Severe Landing Stop Test. 3.3.4.1 The wheel and brake assembly under test must complete the most severe landing braking condition expected on the aeroplane as normally defined by the aeroplane manufacturer. This test is not required if the testing required in paragraph 3.3.3 of this Appendix 1 is more severe or the condition is shown to be extremely improbable, normally by the aeroplane manufacturer.. This test establishes, if required, the maximum energy rating, KESS, of the wheel/brake assembly for landings under abnormal conditions using: a. The Brake Rated Maximum Operating Pressure, BROPMAX; or b. The maximum brake pressure consistent with an aeroplane’s braking pressure limitations (e.g. tyre/runway drag capability based on substantiated data). 3.3.4.2 For the most severe landing stop test, the tyre, wheel and brake assembly must be capable of absorbing the test energy, KESS, with a brake on which the usable wear range of the heat sink has already been fully consumed to BRWL (Reference CS 25.735(f)(3)). The proportioning of wear through the brake for the various friction pairs for this test must be based on service wear experience or wear test data of an equivalent or similar brake. Either operationally worn or mechanically worn brake components may be used. If mechanically worn components are used, it must be shown that they can be expected to provide similar results to operationally worn components. The test brake must be subjected to a sufficient number and type of stops to ensure that the brake’s performance is representative of in-service use; at least one of these stops with the brake near the fully worn condition, must be a design landing stop. 3.3.4.3 At the time of brake application, the temperatures of the tyre, wheel, and brake, particularly the heat sink, must, as closely as practicable, be representative of a typical in-service condition. Preheating by taxi stops is an acceptable means. These temperatures must be based on a rational analysis of a braking cycle, taking into account a typical brake temperature at which the aeroplane may be dispatched from the ramp, plus a conservative estimate of heat sink temperature change during taxi, takeoff, and flight, as appropriate. Alternatively, in the absence of a rational analysis, the starting heat sink temperature must be that resulting from the application of 5 percent KERT to the tyre, wheel and brake assembly initially at not less than normal ambient temperature (59°F/15°C). 3.3.4.4 A full stop demonstration is not required for the most severe landing-stop test. The test brake pressure may be released at a test speed of up to 20 knots. In this case, the initial brakes-on speed must be adjusted such that the energy absorbed by the tyre, wheel, and brake assembly during the test is not less than the energy absorbed if the test had commenced at the specified speed and continued to zero ground speed. 3.3.4.5 Within 20 seconds of completion of the stop, or of the brake pressure release in accordance with paragraph 3.3.4.4 of this Appendix 1, the brake pressure must be adjusted to the Brake Rated Maximum Parking Pressure, BRPPMAX, and maintained for at least 3 minutes. No sustained fire that extends above the level of the highest point of the tyre is allowed before 5 minutes have elapsed after application of parking brake pressure; until this time has elapsed, neither fire fighting means nor coolants may be applied. The time of initiation of tyre pressure release (e.g., by wheel fuse plug), if applicable, is to be recorded. The sequence of events described in paragraphs 3.3.4.4 and 3.3.4.5 of this Appendix 1 is illustrated in Figure 3-2. 3.3.5 Structural Torque Test. The Wheel/Brake Rated Structural Torque, STR, is equal to the torque demonstrated in the test defined in 3.3.5.1 of this Appendix 1. 3.3.5.1 Apply to the wheel, brake and tyre assembly, the radial load S and the drag load corresponding to the torque specified in paragraph 3.3.5.2 or 3.3.5.3 of this Appendix 1, as applicable, for at least 3 seconds. Rotation of the wheel must be resisted by a reaction force transmitted through the brake, or brakes, by the application of at least Brake Rated Maximum Operating Pressure, BROPMAX, or equivalent. If such pressure or its equivalent is insufficient to prevent rotation, the friction surface may be clamped, bolted, or otherwise restrained while applying the pressure. A fully worn brake configuration, BRWL, must be used for this test. The proportioning of wear through the brake for the various friction pairs for this test must be based on service wear experience of an equivalent or similar brake or test machine wear test data. Either operationally worn or mechanically worn brake components may be used. An actuating fluid other than that specified for use on the aeroplane may be used for the structural torque test. 3.3.5.2 For landing gear with one wheel per landing gear strut, the torque is 1·2 (SxR). 3.3.5.3 For landing gear with more than one wheel per landing gear strut, the torque is 1·44 (SxR). 3.3.5.4 The wheel and brake assembly must support the loads without failure for at least 3 seconds. 3.3.6 Wheel to Brake Clearance There must be no interference in any critical areas between the wheel and brake assembly (with fittings) up to limit load conditions, taking into account the axle angular orientation. Lack of interference can be established by analyses and/or tests. If chosen, testing shall be conducted per the following methods: 3.3.6.1 Radial Limit Load Wheel and Brake Clearance Test. With a suitable tyre, TTWT, installed, mount the wheel and brake on a suitable axle, and position it against a flat, non-deflecting surface. The wheel axle must have the same angular orientation to the non-deflecting surface that it will have to a flat runway when it is mounted on an airplane and is under the maximum radial limit load, L. Inflate the tyre to the pressure recommended for the Wheel Rated Static Load, S, with gas and/or liquid. If liquid inflation is used, liquid must be bled off to obtain the same tire deflection that would result if gas inflation were used. Liquid pressure must not exceed the pressure that would develop if gas inflation were used and the tyre was deflected to its maximum extent. Load the wheel through its axle with the load applied perpendicular to the flat, non-deflecting surface. Reference CS 25.471 through 25.511, as appropriate. If the radial limit load of paragraph 3.3.6.2 of this Appendix 1 is equal to or greater than the radial limit load specified in this paragraph, the test specified in this paragraph may be omitted. Determine the most critical wheel orientation with respect to the non-deflecting surface. Apply the load with the tire loaded against the non-deflecting surface. If multiple critical orientations are determined, repeat the testing for each critical orientation. The bearing cups, cones, and rollers used in operation must be used for this loading. If at a point of loading during the test bottoming of the tire occurs, then the tire pressure may be increased an amount sufficient only to prevent bottoming. 3.3.6.2 Combined Limit Load Wheel and Brake Clearance Test. With a suitable tyre, TTWT, installed, mount the wheel and brake on a suitable axle, and position it against a flat, non-deflecting surface. The wheel axle must have the same angular orientation to the non-deflecting surface that it will have to a flat runway when it is mounted on an airplane and is under the maximum radial limit load, L. Apply to the wheel and tyre assembly radial and side loads not less than the respective ground limit loads. Reference, CS 25.485, 25.495, 25.497, and 25.499, as appropriate. If at a point of loading during the test bottoming of the tyre occurs, then the tyre pressure may be increased an amount sufficient only to prevent bottoming. Determine the most critical wheel orientation with respect to the nondeflected surface. Apply the load with the tyre loaded against the non-deflecting surface with the wheel in the most critical orientation. The bearing cups, cones, and rollers used in operation must be used in this test. A tube may be used in a tubeless tire only when it has been demonstrated that pressure will be lost due to the inability of a tyre bead to remain properly positioned under the load. The wheel must be tested for the most critical inboard and outboard side loads. If multiple critical orientations are determined to apply, repeat the testing for each critical orientation. 3.4 BRAKE TESTS. The brake assembly must be tested using the fluid (or other actuating means) specified for use with the brake on the aeroplane. It must be substantiated that standard production samples of the brake will pass the following tests: 3.4.1 Yield & Overpressure Test. The brake must withstand a pressure equal to 1·5 times BRPMAX for at least 5 minutes without permanent deformation of the structural components under test. The brake, with actuator piston(s) extended to simulate a maximum worn condition, must, for at least 3 seconds, withstand hydraulic pressure equal to 2·0 times the Brake Rated Maximum Pressure, BRPMAX, available to the brakes. If necessary, piston extension must be adjusted to prevent contact with retention devices during this test. 3.4.2 Endurance Test. A brake assembly must be subjected to an endurance test during which structural failure or malfunction must not occur. If desired, the heat sink components may be replaced by a reasonably representative dummy mass for this test. The test must be conducted by subjecting the brake assembly to 100,000 cycles of an application of the average of the peak brake pressures needed in the design landing stop test (paragraph 3.3.2 of this Appendix 1) and release to a pressure not exceeding the Brake Rated Retraction Pressure, BRPRET. The pistons must be adjusted so that 25,000 cycles are performed at each of the four positions where the pistons would be at rest when adjusted to nominally 25, 50, 75, and 100 percent of the wear limit, BRWL. The brake must then be subjected to 5 000 cycles of application of pressure to BRPMAX and release to BRPRET at the 100 percent wear limit. Hydraulic brakes must not exceed a total leakage of 5cc during the test. 3.4.3 Piston Retention. The hydraulic pistons must be positively retained without leakage at 1·5 times BRPMAX for at least 10 seconds with the heat sink removed. 3.4.4 Extreme Temperature Soak Test. Hydraulic brakes must not exceed a total leakage of 5cc during the following tests. Subject the brake to at least a 24-hour hot soak at the maximum piston housing fluid temperature experienced during a design landing stop test (paragraph 3.3.2 of this Appendix 1), conducted without forced air cooling. While at the hot soak temperature, the brake must be subjected to the application of the average of the peak brake pressures required during the 100 design landing stops and release to a pressure not exceeding BRPRET for 1000 cycles, followed by 25 cycles of BROPMAX and release to a pressure not exceeding BRPRET. The brake must then be cooled from the hot soak temperature to a cold soak temperature of - 40°F (-40°C) and maintained at this temperature for at least 24 hours. While at the cold soak temperature, the brake must be subjected to the application of the average of the peak brake pressures required during the KEDL stops and release to a pressure not exceeding BRPRET, for 25 cycles, followed by 5 cycles of BROPMAX and release to a pressure not exceeding BRPRET. 3.4.5 Leakage Tests (Hydraulic Brakes). 3.4.5.1 Static Leakage Test. The brake must be subjected to a pressure equal to 1·5 times BRPMAX for at least 5 minutes. The brake pressure must then be adjusted to an operating pressure of 5 psig (35 kPa) for at least 5 minutes. There must be no measurable leakage (less than one drop) during this test. 3.4.5.2 Dynamic Leakage Test. The brake must be subjected to 25 applications of BRPMAX, each followed by the release to a pressure not exceeding BRPRET. Leakage at static seals must not exceed a trace. Leakage at moving seals must not exceed one drop of fluid per each 3 inches (76mm) of peripheral seal length. **CHAPTER 4** **DATA REQUIREMENTS** 4.1 The applicant must provide the following data with any application for approval of equipment. 4.1.1 The following wheel and brake assembly ratings: a. Wheel Ratings. Wheel Rated Static Load, S, Wheel Rated Inflation Pressure, WRP, Wheel Rated Tyre Loaded Radius, R. Wheel Rated Maximum Limit Load, L, Wheel Rated Tyre Size, TSWR. b. Wheel/Brake and Brake Ratings. Wheel/Brake Rated Design Landing Energy, KEDL, and associated brakes-on-speed, VDL, Wheel/Brake Rated Accelerate-Stop Energy, KERT, and associated brakes-on-speed, VRT, Wheel/Brake Rated Most Severe Landing Stop Energy, KESS, and associated brakes- on-speed, VSS (if applicable), Brake Rated Maximum Operating Pressure, BROPMAX, Brake Rated Maximum Pressure, BRPMAX, Brake Rated Retraction Pressure, BRPRET, Wheel/Brake Rated Structural Torque, STR, Rated Design Landing Deceleration, DDL, Rated Accelerate-Stop Deceleration, DRT, Rated Most Severe Landing Stop Deceleration, DSS (if applicable), Brake Rated Tyre Size, TSBR, Brake Rated Wear Limit, BRWL. 4.1.2 The weight of the wheel or brake, as applicable. 4.1.3 Specification of hydraulic fluid used, as applicable. 4.1.4 One copy of the test report showing compliance with the test requirements. NOTE: When test results are being recorded for incorporation in the compliance test report, it is not sufficient to note merely that the specified performance was achieved. The actual numerical values obtained for each of the parameters tested must be recorded, except where tests are pass/fail in character. 4.2 Prior to entry into service, a component maintenance manual (CMM), covering periodic maintenance, calibration, and repair, for the continued airworthiness of installed wheels and wheel and brake assemblies, including recommended inspection intervals and service life.  ***Figure 3-1. Taxi, Accelerate-Stop, Park Test Sequence***  ***Figure 3-2. Most Severe Landing-Stop, Park Test Sequence*** [Amdt ETSO/6]