1、_6$(7HFKQLFDO6WDQGDUGV%RDUG5XOHVSURYLGHWKDW7KLVUHSRUWLVSX EOLVKHGE6$(WRDGYDQFHWKHVWDWHRIWHFKQLFDODQGHQJL neering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any pDUWLFXODUXVHLQFOXGLQJDQSDWHQWLQIULQJHPHQWDULVLQJWKHUHIURPLVWKHVR OHUHVSRQVLELOLWRIWK
2、HXVHUSAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions.Copyright 2016 SAE InternationalAll rights reserved. No part of this publication may be reproduced, stored in a re
3、trieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada)Tel: +1 724-776-4970 (outside USA)Fax: 724-776-0790Email: Custome
4、rServicesae.orgSAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedbackon this Technical Report, please visithttp:/www.sae.org/technical/standards/AIR5556AEROSPACEINFORMATION REPORTAIR5556Issued 2009-05Reaffirmed 2016-04Landing Gear AlignmentRATIONALEAIR5556 has been reaffirmed t
5、o comply with the SAE five-year review policy.1. SCOPE The purpose of this Aerospace Information Report is to provide the industry with methodologies for measuring tire/wheel gear alignment and the range of acceptable alignment settings for various types of non-military landing gear. This AIR will f
6、ocus on the general aviation, corporate, and regional aircraft landing gear but could have applicability to commercial aircraft.2. REFERENCES The following publications for a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue
7、of the other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations
8、unless a specific exemption has been obtained. 2.1 Applicable Documents 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org.AIR1489 Aerospace Landing Gear Term
9、inology 951391 The Aircraft Tire Wear Problem 2.1.2 U.S. Government Available from the Document Automation and Production Service (DAPS), Building 4/D, 700 Robbins Avenue, Philadelphia, PA 19111-5094, Tel: 215-697-6257, http:/assist.daps.dla.mil/quicksearch/. AC 90-89A Amateur Built Aircraft and Ult
10、ra-light Flight Testing Aircraft 3. BACKGROUND Beginning with fixed landing gear in the early days of aircraft development, the correct alignment of the tire/wheel to the centerline of the aircraft has been critical. Fixed landing gear were the easiest to adjust as third party suppliers developedshi
11、ms to be placed between the gear and the mounting point. However, the means to measure the gear alignment has been crude, utilizing carpenters square, duct tape, wooden blocks, etc. This equipment gets the gear close to proper alignment but is not accurate enough to optimize tire wear and reduce gea
12、r load. Some of these methods were developed by the home-built aircraft operators that had the desire to install the gear correctly but not the proper tools. Tire wear due to a misalignment of the landing gear components can be attributed to several factors: braking forces causing a toe-out/toe-in c
13、ondition load causing a positive or negative camber angle poor rigging of the landing gear during aircraft construction axle deflection landing gear component wear runway crown These items show the complexity of the landing gear and the difficulty to account for all the static and dynamic forces act
14、ing on the landing gear assembly. The drag force caused by braking can generate a toe-out condition that changes as a function of the applied braking pressure. The shimmy damper, if installed, has an additional range of motion that can alter the toe condition. Axle deflection from aircraft loading h
15、as been identified in some cases to be a major contributor to camber wear. This can be further impacted in a dynamic mode as the aircraft “bounces” down the runway during takeoff or landing. This AIR focuses on static conditions compensating for aircraft load and landing gear alignment. If some info
16、rmation of axle deflection as a function of braking is known, this can be applied in the final toe and camber settings. It is impossible to account for all of the items that impact gear alignment but an effort should be made to account for as many as possible. 4. REFERENCE DIAGRAM FIGURE 1 - SCHEMAT
17、IC DIAGRAM OF TOE AND CAMBER ORIENTATION FOR MULTI-TIRE GEARS STRUTSAE INTERNATIONAL AIR5556 2 OF 11FIGURE 2 - SCHEMATIC DIAGRAM OF TOE AND CAMBER ORIENTATION FOR SINGLE TIRE GEAR 5. ALIGNMENT PROCEDURES 5.1 Field Expedient Method This is the commonly used method to measure the gear alignment with c
18、ommon tools found in the aircraft maintenance shop. 5.1.1 Measuring Aircraft Toe This is a quick yet accurate method to measure total tire toe. Total toe includes the sum of each tires individual toe measurement. The accuracy of the measurements will be based on the set-up and the precision of the t
19、ools used to make the measurements. This method gives a total toe measurement since it is not referenced from the aircraft centerline but relative to the two landing gears. In a tricycle gear configuration, this will configure the main landing gear parallel to the direction of travel and not necessa
20、rily to the fuselage. Gear alignment is a problem in basic geometry where the objective is to determine the angle if the tire/wheel assembly is out of plane both vertically and horizontally to either the aircraft centerline or the direction of travel. It is normally desirable to measure from the air
21、craft centerline but establishing this centerline can be very difficult and is recommended if more precision equipment is available and the relative measurement must be reduced. Initial Condition (Set-up) Select the aircraft center of gravity (CG) configuration that best represents normal aircraft o
22、perational weight and load distribution. In the absence of a specified typical operational weight, the average of Maximum Landing Weight (MLW) and Maximum Takeoff Off Weight (MTOW) could be used. Verify that the tire is inflated to the correct operational pressure. Verify that all moveable gear comp
23、onents are within manufacturing tolerance. Ensure the aircraft is on a flat and level surface. Verify that the aircraft has been rolled forward along the centerline of the aircraft at least the length of the fuselage to remove any residual forces acting on the landing gear. If the aircraft is equipp
24、ed with a tail wheel, the aircraft should be initially set up in flight configuration (run-on landingconfiguration) with the tail elevated to achieve a wings level condition at the chord. SAE INTERNATIONAL AIR5556 3 OF 11ODLLTan )( 121 = Procedure a) Determine the Outside Diameter (OD) of the tire a
25、long its centerline and record this value. This should be measured parallel to the ground and through the axle centerline. b) Mark a “+” on the leading edge of the tire at a height H1 as close as possible to the tires equator and along the tire centerline for tire number one. Record H1.FIGURE 3c) Ma
26、rk another “+” on the leading edge of the tire along the centerline of the second tire on the opposite landing gear at the same height H1. Make sure that the reference point is the same. d) Measure the linear distance between the two marks as L1.e) Move the aircraft forward along its centerline to r
27、otate the tires 180 degrees. f) Recheck that the height H1 for the “+” of both tires is the same. Adjust the aircraft location if required. g) Measure the distance between the “+” marks rotated 180 degrees as L2.h) Calculate the Total Toe angle: NOTE: The inboard wheel flange could be used if a cont
28、inuous line of sight exists between the front and back of the two wheels. In this case the OD measurement would be replaced by the flange diameter. 5.1.2 Level Method for Measuring Camber The level method is a quick yet accurate method to measure tire camber. Precision of the measurements will be ba
29、sed on the set-up and the tools used to make the measurements. A digital level, if used, will generate good accuracy for this measurement. Initial Condition (Set-up) Select the aircraft center of gravity (CG) configuration that best represents normal aircraft operational weight and load distribution
30、. In the absence of a specified typical operational weight, the average of Maximum Landing Weight (MLW) and Maximum Takeoff Off Weight (MTOW) could be used. Verify that the tire is inflated to operational pressure. Ensure the aircraft is on a flat and level surface. Verify that the aircraft has been
31、 rolled in the forward direction at least the length of the aircraft. If the aircraft is equipped with a tail wheel, the aircraft should be initially set up in flight configuration (run-on landingconfiguration) with the tail elevated to achieve a wings level condition at the chord. Confirm that the
32、level has been properly calibrated. H1LnSAE INTERNATIONAL AIR5556 4 OF 11LCDFGTTan n1n =Procedure a) Place the level on the flat edges of the wheel flange in a vertical position. Be sure that the level does not come into contact with the tire. FIGURE 4 b) Record the Level Contact Distance (LCD) betw
33、een the flange contact points. c) Place feeler gages at either the top or the bottom of the flange contact to center the bubble. Record Feeler Gage Thickness (FGT). VALUE UNIT FGTT FGTB d) Calculate the camber angle (.).where n = top or bottom measurement VALUE .T (positive / negative) Degree .B (po
34、sitive / negative) Degree 5.2 Precision Method There are several types of alignment equipment used on ground tire applications that can be applied to the aircraft tire. All of this professional equipment will provide a very accurate measurement of the landing gear alignment providing the equipment h
35、as the ability to be adapted to the various wheel diameters. Aircraft setup with the use of professional equipment is critical for an accurate measurement of the gear alignment. It is highly probable that the equipment manufacturer will not have set-up procedures for measuring aircraft. The followin
36、g initial conditions can be used to prepare the aircraft for measurement. LCD SAE INTERNATIONAL AIR5556 5 OF 11Initial Condition Select the aircraft Center of Gravity (CG) configuration that best represents the normal aircraft operational weight and load distribution. In the absence of a specified t
37、ypical operational weight, the average of Maximum Landing Weight (MLW) and Maximum Takeoff Off Weight (MTOW) could be used. Verify that the tire is inflated to the correct operational pressure. Verify that all moveable gear components are within manufacturing tolerance. Ensure the aircraft is on a f
38、lat and level surface. Verify that the aircraft has been rolled in the forward direction. Grease plates between the tire and ground may be used in lieu of moving the aircraft. Verify that the aircraft parking brakes are released. Establish the aircraft centerline on the floor by dropping a plum bob
39、line from the fore and aft centerline points on the aircraft fuselage. Draw a line on the floor connecting these two points. Follow the equipment manufacturers recommendations for measuring the toe and camber settings after the initial conditions above have been set. Some equipment that can be used
40、for measuring gear alignment is Ben Mueller Alignment equipment (see Figure 4). This equipment was developed for ground vehicle use but is adaptable to a wide range of aircraft tire/wheel combinations. It has the ability to measure both toe and camber very accurately. A theodalite can also be used t
41、o make these measurements but a separate procedure would need to be developed. FIGURE 5 - BEN MUELLER ALIGNMENT EQUIPMENT Other ground vehicle equipment that can be used to measure toe is the Laser Toe II (Figure 5) produced by Advanced Racing Technologies. This piece of equipment has similar capabi
42、lities as the Ben Mueller in that it can be used easily in the field, fits a wide range of wheel diameters, and measures total toe very accurately. Wheel Clamp Assembly Projector formeasuring toe Cambermeasurement device SAE INTERNATIONAL AIR5556 6 OF 11FIGURE 6 - LASER TOE II EQUIPMENT 5.3 Suggeste
43、d Toe and Camber Settings The final settings of toe and camber on the aircraft depend on many factors as noted in section 1 but should result in the tire/wheel assembly operating within the suggested limits for toe and camber, whether normally or fully loaded, whether subjected to braking or free ro
44、lling. Some knowledge of the resultant axle movements due to aircraft mass changes and drag force changes due to braking is very beneficial for an optimum setting of the gear in relation to the aircraft itself. The following suggested toe and camber settings have been used successfully on several ai
45、rcraft in the field and are based in part on ground vehicle settings. Tire/Wheel Toe Setting In the absence of any manufacturers specifications, the toe setting of the tire/wheel assembly on the aircraft should result in an operational Total Toe between 0 degrees and 0.3 degrees or a single tire Toe
46、 of 0.15 degrees 0.15 degrees relative to the aircraft longitudinal centerline under braked and unbraked conditions/ normal and full static loads.Tire/Wheel Camber Setting - In the absence of any manufacturers specification, the camber setting of the tire/wheel assembly on the aircraft should result
47、 in an operational camber of +0.0 degrees 0.5 degrees relative to vertical under braked and unbraked conditions/ normal and full static loads. How these adjustments can be made varies widely from aircraft to aircraft. Some fixed gear aircraft have the capability of adding shims between the axle atta
48、ch point and the landing gear. Other aircraft may have the capability to adjust a gear component. Check with the aircraft manufacturer to determine whether the gear can be adjusted to make these settings. Some aircraft have no means of adjustment beyond factory settings. 6. TIRE IMPACT OF GEAR MISALIGNMENT 6.1 Toe-in/Toe-out (Yaw) Condition A toe-in or toe-out condition is caused by th
