1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE 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 2014 SAE International All rights reserved. No part of this p
3、ublication may be reproduced, stored in a retrieval 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: +1 724-776-497
4、0 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/ARP5941AEROSPACERECOMMENDED PRACTICEARP5941 Issued 2008-03 Reaffirmed 2014-10 Aer
5、ospace Fluid Power - Contamination Sensitivity - Considerations for Establishing Test Procedures for Flight Control ActuatorsRATIONALE ARP5941 has been reaffirmed to comply with the SAE five-year review policy. TABLE OF CONTENTS 1. SCOPE 2 2. APPLICABLE DOCUMENTS 2 2.1 SAE Publications. 2 2.2 NFPA P
6、ublications 2 2.3 National Aerospace Standards Publications. 2 2.4 ISO Publications 3 3. BACKGROUND 3 3.1 Introduction . 3 3.2 History . 3 3.3 Requirements 4 4. TEST PROCEDURES 4 4.1 General . 4 4.2 Endurance. 5 4.2.1 Conditions for Endurance Test . 5 4.2.2 Detailed Test Procedure . 5 4.2.3 Success
7、Criteria for Endurance Test 6 4.3 Silting Test 6 4.3.1 Conditions for Silting Test . 6 4.3.2 Success Criteria for Silting Test 7 4.4 Test Setups . 7 5. NOTES 7 1. SCOPE This SAE Aerospace Recommended Practice (ARP) describes the design conditions under which tests should be conducted to demonstrate
8、satisfactory performance of a flight critical servo-actuator under the maximum allowable particulate contamination in the associated airplane hydraulic system. Additionally, this document also describes the recommended tests and the required acceptance criteria. 2. APPLICABLE DOCUMENTS The following
9、 publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of 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 refer
10、ences cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. The documents listed herein and referenced throughout the text should be consulted in the design of the contami
11、nation sensitivity test setup and the conductance of the test. 2.1 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. ARP219 Procedure and Method for Conducting Te
12、st of Hydraulic Components in Contamination Controlled System ARP598 Aerospace Microscopic Sizing and Counting of Particulate Contamination for Fluid Power Systems AS4059 Aerospace Fluid Power - Cleanliness Classification for Hydraulic Fluids J2470 Hydraulic Fluid Power - Valves - Method for Assessi
13、ng the Lock Sensitivity to Contaminants 2.2 NFPA Publications Available from National Fluid Power Association, 3333 N. Mayfair Road, Suite 211, Milwaukee, WI 53222-3219, Tel: 414-778-3344, . T.3.9.18 R1-1978 Flow degradation for fixed displacement hydraulic pumps - (Note: Withdrawn without a superse
14、ding document) T.3.5.48 1994 Procedure for Evaluating Hydraulic Fluid Power Valves (Note: Rescinded, revised version issued as SAE J2470) 2.3 National Aerospace Standards Publications Available from Aerospace Industries Association, 1000 Wilson Boulevard, Suite 1700, Arlington, VA 22209-3928, Tel: 7
15、03-358-1000, www.aia-aerospace.org. NAS 1638 Cleanliness Requirements of Parts Used in Hydraulic Systems (Note: Inactive for new design and superseded by AS4059) SAE INTERNATIONAL ARP5941 2 OF 72.4 ISO Publications Available from American National Standards Institute, 25 West 43rd Street, New York,
16、NY 10036-8002, Tel: 212-642-4900, www.ansi.org. ISO 11171 Hydraulic fluid power - Calibration of automatic particle counters for liquids 3. BACKGROUND 3.1 Introduction The primary risks to satisfactory operation of flight critical servo-actuators due to particulate contamination could be valve jammi
17、ng through blockage or silting and valve erosion. Fluid contamination may be a single cause affecting operation of both control and monitor components such as a control valve and a by-pass valve, which are supposed to be independent. The airframe manufacturer and/or group applying the part to the ai
18、rplane should determine whether or not these tests apply to a part. It may be relevant to apply this to parts that are not flight critical, and, conversely, it may not be relevant to apply this to parts that are flight critical. These tests also include a segment that assures the components fault to
19、lerance for particulate contamination conditions during which the allowable level may be unintentionally exceeded during airplane operation. Provided herein are Background for the rationale of the test Definitions when such a test is to be performed Outlines of the tests to be conducted Success crit
20、eria for the tests. What is not provided herein are How the test is to be conducted How the contaminants are to be induced How the contaminant level is to be controlled The composition of the contaminant. The reason for the absence of these parameters is: No commonly accepted method exists nor is th
21、ere agreement as to what can realistically be implemented. Nevertheless some guidance is provided. The specifics of these tests are to be established between the Procuring Agency and the Supplier. 3.2 History Typically, Flight Control actuators were designed to specifications requiring operation wit
22、h maximum contamination levels of NAS 1638 Classes 7 or 8. NAS 1638 has been superseded by AS4059 and the contamination classes of AS4059 are equivalent. They were qualified utilizing test stands and aircraft with contamination levels meeting those requirements. Typically the test stands were mainta
23、ined at even cleaner levels. Commercial aircraft fleet surveys have revealed that the fleet operates often at higher-than-recommended contamination levels (as high as Class 12 was reported). They did so without experiencing any noticeable performance degradation. This observation provided some of th
24、e background for the above mentioned SAE recommendation, namely to allow operation at Class 9 level, or better. Most aircraft manufacturers currently define maximum in-service particulate contamination as NAS 1638 or AS4059 Class 9. This followed the recommendation by the SAE A-6 Committee to the FA
25、A. SAE INTERNATIONAL ARP5941 3 OF 7At one time an evaluation test was performed on a flight control actuator with controlled contamination levels at NAS 1638 Classes 9, 12 and eight times that of Class 12. This actuator was a mechanical input servoactuator with an integrated yaw damper piston contro
26、lled through an electro-hydraulic servovalve. The test was conducted by cycling the mechanical input as well as the yaw damper circuit. Acceptance tests were conducted after completion of the cycles for each contamination level. Note, that during the test, there were a few hydraulic pump failures, b
27、ut the actuator continued to operate. The unit performed acceptably for an extended period of time but showed significant wear, especially erosion in the main control valve area. This test demonstrated again a basic premise: Current flight control actuators are designed to cope safely with increased
28、 contamination. Furthermore, Their performance degrades gradually. They are insensitive to silting. Wear does accelerate with increased contamination levels. However, it is recognized that future designs (materials, material combinations, clearances, etc.) of flight control actuators may not have as
29、 good a fault tolerance as the existing flight control actuator designs and their historical characteristics of sensitivity to contamination. The tests described herein are intended to provide a vehicle to assure that the contamination tolerance sensitivity of a new flight control actuator design is
30、 acceptable. 3.3 Requirements These tests shall be conducted if the basic design, material combinations and/or clearances differ from the ones currently employed. They are listed in Table 1. Some of these tests shall be conducted, if the qualified component is reworked or reconditioned using differe
31、nt materials combinations or clearances. TABLE 1 - DESIGN DATA FOR CURRENT FLIGHT CONTROL ACTUATORS Combination Material Surface Finish Min / Max Diametral Clearances (Inch) Power Piston Rod / Gland Chrome Plate / Al-Ni Bronze Chrome Plate / Anodize Al Alloy Chrome Plate / Be-Cu 0.002 - 0.006 Servov
32、alve Sleeve / Slide Nitralloy / Nitralloy 52100 / Nitralloy 440C / 440C 0.000100 - 0.000250 See Note below Bypass Valve Sleeve / Slide Same As Servovalve 0.000100 - 0.000250 NOTE: A minimum diametral clearance of 0.000150 inches is recommended. 4. TEST PROCEDURES 4.1 General There shall be two tests
33、. The first one is to determine the life characteristics of the newly designed flight control actuator. The second one is to define the adequacy of the new design against performance degradation due to silting. SAE INTERNATIONAL ARP5941 4 OF 74.2 Endurance This test shall be conducted in addition to
34、 the normal endurance test in the same manner except as outlined below. It is intended to be patterned on the typical load-stroke-temperature qualification test. Additionally, a total of 20 typical flight cycles shall be part of this test. However, these tests shall be conducted in two phases as fol
35、lows: Phase I: 40% of the original total endurance test cycles shall be repeated under the same conditions as well as 16 flight cycles, equally distributed between the endurance test layers. These will be conducted on a dedicated test bench in which the particulate contamination level is to be maint
36、ained between AS4059 Class 8 and 10. Its permissible to start this test with clean hydraulic fluid. However, within the first layers of the test, the prescribed contamination level needs to be achieved. Gradual clean up of the system is allowed. Furthermore, contaminants need to be added to assure t
37、hat 35% of the new (40%) cycles will be conducted at the maximum contamination levels (Class 10). Phase II: 10% of the total original test cycles shall be conducted at room temperature and 50% stroke and load as well as 4 flight cycles while maintaining the contamination level between Classes 10 and
38、 12. The maximum performance degradation during each phase of the test shall be assessed with two measurements. An acceptance test shall be conducted per Specification before and after each Phase. The component shall be considered qualified if the results of the final dynamic acceptance tests are wi
39、thin the success criteria established in 4.2.3. 4.2.1 Conditions for Endurance Test The unit shall be operated at the normal operating supply and return pressures and with the ambient temperature at the normal operating level. 4.2.2 Detailed Test Procedure Prior to the test verify that the actuator
40、complies with the applicable acceptance test procedure. It is suggested to take measurements of internal diameter of the sleeve and external diameter of the spool in at least four places in the honed length and two directions 90 degrees apart looking at the end of the spool and sleeve. They should b
41、e taken before and after completion of the tests to establish wear. Prepare the test fluid prior to the test to meet the proper contamination level and mix of contaminants. The test fluid shall be between the AS4059 classes specified in 4.2. Submit fluid samples for analysis and enter the AS4059 cla
42、ss in the test log sheet. Once the test is started the sample valve can be opened to allow a sample to be taken so that the fluid contamination can be monitored during the test. The sampling should be into two 100 ml sample bottles one of which shall be processed by ARP598 and which shall be conside
43、red the designated contamination level of the test system. The other sample bottle shall be processed by automatic particle counter (APC) calibrated to ISO 11171. These tests shall be repeated at least three times throughout the tests for Phase 1 and twice for Phase 2. The results of the ARP598 test
44、s and APC will not necessarily be in agreement. Record the contamination classes in the test log sheet. The use of an in-line contamination monitoring system to continuously monitor the fluid contamination level during the test is optional. SAE INTERNATIONAL ARP5941 5 OF 7Start the Phase I testing a
45、s follows: Mount the test unit in the endurance test fixture. Apply the loads as specified in the applicable test procedure. Apply pressure to the unit as specified in the applicable test procedure. Cycle the unit in accordance with the applicable test procedure Periodically open the sample valve du
46、ring the test and take a sample of the test fluid. Enter the fluid class in the test log sheet. Continue cycling until the test is completed. Conduct an acceptance test on the test unit. Conduct the Phase II test in the same manner as for Phase I. 4.2.3 Success Criteria for Endurance Test The test u
47、nit shall be considered to have passed the contamination test if for the frequency range of interest: The final dynamic performance (amplitude ratio) shall not degrade more than 25% from the initial performance and That the final measured phase lag of a flight control actuator is not more than 15 de
48、grees greater than the initially allowed phase lag, or as specified in the specific test procedure. The peak-to-peak command for the frequency response test is not more than 2% of the total actuator stroke. The mode select valve response time is within 130% of the initial time. These criteria are re
49、commended and should be reviewed and modified as necessary given the requirements agreed upon between the procuring activity and supplier of the equipment. 4.3 Silting Test This test shall be conducted for critical components that are typically in a “Standby Mode”. They are pressurized for a whole flight, but are called upon to function without hesitation, when needed to overcome the failure effect
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