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3、y 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: +1 724-776-4970 (outside US
4、A) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AIR5925AAEROSPACEINFORMATIONREPORTAIR5925 REV. A Issued 2007-02 Revised 2013-07 Superseding AIR
5、5925 Measurement Uncertainty Applied to Cost-Effective Testing RATIONALEThe purpose of this revision is to align the methodology, nomenclature, and terminology with AIR1678 Revision B.TABLE OF CONTENTS 1. SCOPE 41.1 Introduction . 41.2 Concluding Remarks . 52. REFERENCES 62.1 Applicable Documents 62
6、.2 Applicable References 63. THE PRELIMINARY TEST PLAN . 63.1 Introduction . 73.1.1 General . 73.1.2 The Worked Example . 73.2 Defining the Test Objectives and Customer Requirements 93.2.1 Test Article 93.2.2 Test Objectives . 103.2.3 Test Requirements and Uncertainty Levels 103.2.4 Limitations . 11
7、3.2.5 Risk Assessment 113.3 Defining the Test Process . 123.3.1 Outline Test Procedure . 123.3.2 Outline Measurements 123.3.3 Initial Uncertainty Analysis 143.3.4 Presentation of Results . 193.3.5 Resources . 193.4 Summary . 204. DEFINED MEASUREMENT PROCESS (DMP) (FIGURE 7) . 204.1 Measurement Chain
8、 Definition 214.1.1 Calibration . 214.1.2 Instrumentation Installation Effects . 224.1.3 Data Acquisition 224.1.4 Data Reduction . 23SAE AIR5925A Page 2 of 56 4.1.5 Errors of Method (and Other Non-Instrumentation Effects) 234.1.6 Example Measurement Chain Definition 244.2 Elemental Uncertainty Analy
9、sis 254.2.1 Random Standard Uncertainty 264.2.2 Standard Systematic Uncertainty 264.2.3 Uncertainty of Empirical Data . 274.2.4 Example Elemental Uncertainty Analysis . 274.3 Results Parameter Uncertainty Analysis 304.3.1 Influence Coefficients 304.3.2 Overall Uncertainty of Result 304.3.3 Correlate
10、d Systematic Errors 314.3.4 Example: Installation Effects and Errors of Method for PT2 Measurement 324.3.5 Test Type Considerations . 334.3.6 Pareto Analysis of Uncertainty Contributions . 334.4 Example Results Parameter Uncertainty Analysis . 334.4.1 Analysis at Takeoff Condition . 334.4.2 Analysis
11、 at Cruise Condition . 364.5 Summary . 385. FINAL TEST PLAN . 395.1 Introduction . 395.2 Prepare Final Test Plan Proposal . 395.3 Test Team and Customer Review 395.4 Modify and Finalize Test Plan . 405.5 Summary . 405.6 Example Final Test Plan . 406. PRELIMINARY TEST AND REVIEW (FIGURE 13) . 416.1 I
12、ntroduction . 416.2 Check Out Test Plant and Instrumentation Performance . 416.2.1 Test Article 416.2.2 Facility . 426.3 Review 426.3.1 Assess Results 426.3.2 Compare Actual Uncertainty with Predictions . 426.4 Application to Example . 446.5 Summary . 457. ACTUAL TEST (FIGURE 18) 467.1 Work to Test
13、Plan 467.2 Monitor Measurements and Results During the Test . 467.3 Data Release 477.4 Analysis of Actual Results . 477.5 Performance Data Example 487.6 Post-Test Uncertainty Determination Example . 507.6.1 Cruise Condition 517.6.2 Take-Off Condition 527.6.3 Conclusion 527.7 Summary . 548. POST-TEST
14、 REVIEW AND REPORT (FIGURE 24) 548.1 Compare Performance Results to Predictions . 548.2 Prepare Final Test Report . 558.3 Update Lessons Learned File . 558.4 Conclusion 569. NOTES 56SAE AIR5925A Page 3 of 56 FIGURE 1 AIR5925 MAP . 5FIGURE 2 PRELIMINARY TEST PLAN . 6FIGURE 3 TYPICAL IN-FLIGHT THRUST
15、DETERMINATION PROCESS . 8FIGURE 4 PRELIMINARY TEST PLAN DIAGRAM . 13FIGURE 5 PARETO ANALYSIS OF IN-FLIGHT THRUST PARAMETER UNCERTAINTIES (TAKE-OFF) . 16FIGURE 6 PARETO ANALYSIS OF IN-FLIGHT THRUST PARAMETER UNCERTAINTIES (CRUISE) . 18FIGURE 7 DEFINED MEASUREMENT PROCESS 20FIGURE 8 CALIBRATION HIERAR
16、CHY 22FIGURE 9 EXAMPLE PRESSURE MEASUREMENT SYSTEM . 25FIGURE 10 PARETO ANALYSIS OF IN-FLIGHT THRUST PARAMETER UNCERTAINTIES (TAKE-OFF) . 36FIGURE 11 PARETO ANALYSIS OF IN-FLIGHT THRUST PARAMETER UNCERTAINTIES (CRUISE) . 38FIGURE 12 FINAL TEST PLAN . 39FIGURE 13 PRELIMINARY TEST AND REVIEW 41FIGURE
17、14 MEASUREMENTS FALL WITHIN UNCERTAINTY PREDICTION 43FIGURE 15 MEASUREMENTS EXHIBIT SYSTEMATIC ERRORS FROM PREDICTION . 43FIGURE 16 MEASUREMENTS EXHIBIT RANDOM ERRORS FROM PREDICTION 44FIGURE 17 PLOT OF COMPRESSOR DISCHARGE PRESSURE PROFILE 45FIGURE 18 ACTUAL TEST 46FIGURE 19 EXAMPLE OF A PERFORMANC
18、E CURVE PLOTTED AGAINST A COMPARATIVE DATA CURVE-FIT . 49FIGURE 20 RANDOM UNCERTAINTY LIMITS FOR THE COMPARISON BETWEEN TEST DATA ANDPREVIOUS INFORMATION (INCLUDES SUSPECT POINT) . 49FIGURE 21 RANDOM UNCERTAINTY LIMITS FOR THE COMPARISON BETWEEN TEST DATA ANDPREVIOUS INFORMATION (SUSPECT POINT REMOV
19、ED) . 50FIGURE 22 POST-TEST UNCERTAINTY PARETO ANALYSIS (CRUISE CONDITION) 53FIGURE 23 POST-TEST UNCERTAINTY PARETO ANALYSIS (TAKE-OFF CONDITION) 53FIGURE 24 POST-TEST REVIEW AND REPORT 54TABLE 1 UNCERTAINTY ANALYSIS FOR IN-FLIGHT THRUST DETERMINATION (ON-WING PHASE - TAKEOFF CONDITION) . 15TABLE 2
20、UNCERTAINTY ANALYSIS FOR IN-FLIGHT THRUST DETERMINATION (ON-WING PHASE -CRUISE CONDITION) 17TABLE 3 EXAMPLE ELEMENTAL UNCERTAINTY SUMMARY TABLE 28TABLE 4 UNCERTAINTY ANALYSIS FOR IN-FLIGHT THRUST DETERMINATION (ON-WING PHASE - TAKEOFF CONDITION) . 34TABLE 5 UNCERTAINTY ANALYSIS FOR IN-FLIGHT THRUST
21、DETERMINATION (ON-WING PHASE - TAKEOFF CONDITION - IMPROVED PT2) . 35TABLE 6 UNCERTAINTY ANALYSIS FOR IN-FLIGHT THRUST DETERMINATION (ON-WING PHASE -CRUISE CONDITION) 37TABLE 7 EXAMPLE OF PRESSURE RAKE MEASUREMENTS (PSIA) 44TABLE 8 EXAMPLE OF PERFORMANCE DATA (TAKE-OFF CONDITIONS) 48TABLE 9 POST-TES
22、T UNCERTAINTY ANALYSIS FOR IN-FLIGHT THRUST DETERMINATION (CRUISE CONDITION) . 51TABLE 10 POST-TEST UNCERTAINTY ANALYSIS FOR IN-FLIGHT THRUST DETERMINATION (TAKE-OFF CONDITION) . 52SAE AIR5925A Page 4 of 56 1. SCOPE The report shows how the methodology of measurement uncertainty can usefully be appl
23、ied to test programs in order to optimize resources and save money. In doing so, it stresses the importance of integrating the generation of the Defined Measurement Process into more conventional project management techniques to create a Test Plan that allows accurate estimation of resources and tro
24、uble-free execution of the actual test. Finally, the report describes the need for post-test review and the importance of recycling lessons learned for the next project. 1.1 Introduction Uncertainty analysis is a practical, scientific tool that is used to estimate the uncertainty of test measurement
25、s and of test results determined from the measurements. Prior to actually running a test, the methodology of uncertainty analysis allows the experimenter to learn much about the potential accuracy of a test result and to assess the relative effects of various error sources on the total test uncertai
26、nty. After data is obtained in the test, uncertainty analysis is used to quantify the goodness of the experimental results. There has been an increase in the awareness of uncertainty analysis over the past several years, and some of the key sources of information on it are given in References 2.1.1.
27、1, 2.1.2.1, 2.2.1, and 2.2.2. Unfortunately, the planning, design, and execution of testing programs is still too frequently carried out without reference at the planning stage to the detailed needs of the recipient/end-user of the test results and consequently without proper regard to the required
28、uncertainty of the test measurements. A common scenario is that a test is planned within budgeted costs and timescales, utilizing facilities which are not optimal to the testing program but which are either already available or are readily accessible at reasonable cost. If the assessment of the unce
29、rtainty of the results takes place after the testing has been completed, then there is a risk that the accuracies actually obtained fail to meet the desired, sometimes contractual, requirements.Obviously, cost-effectiveness in the use of testing resources is vitally important within both industrial
30、and academic environments, and the scenario described above is based upon this necessity for economy. Finding that test results are too uncertain to be used effectively is not cost effective. However, the application of measurement uncertainty methodologies to the planning of the test program can be
31、nefit not only the final accuracy of the test but also the cost effectiveness of its execution. The action of defining the measurement processes, including the detailed breakdown of calibration hierarchies and elemental error sources, ensures that the test that is performed actually provides the req
32、uired level of measurement uncertainty. It is not cost-effective to obtain a greater accuracy than is required. In this way, the use of expensive laboratory or industrial scale testing facilities may be optimized and real savings made. The purpose of this report is to present a clearly defined appro
33、ach to the application of uncertainty methodology to the planning and conduct of cost effective test programs. The report is written for the aero engine-testing environment, and in particular for the determination of in-flight thrust. However, the approach described in the report can be applied to a
34、lmost any experimental setting and is recommended to all who undertake testing programs with cost constraints. The report begins by defining the basic requirements for a preliminary test plan from which estimates of resources, timescales, etc. may be drawn. It emphasizes the need to address the actu
35、al needs of the “customer” (whoever that may be) at the initial stages of planning. The required uncertainty of the test results must be established through expert dialogue between the supplier/test engineer and the customer/user. At this stage in the test program, an initial uncertainty analysis is
36、 performed using knowledge of the probable instrumentation uncertainties and experience of similar testing work. This initial uncertainty analysis helps to identify potential problems and to verify that the test has some reasonable probability of meeting the required uncertainty for the test results
37、.Potential problems with both human and material resources, schedules, and other major test issues are identified in this initial phase of the test program. The preliminary test plan section of the report stipulates the need to recognize the limitations, risks, and the importance of a clear definiti
38、on of program accuracy requirements. SAE AIR5925A Page 5 of 56 The report continues with the description of the development of the Defined Measurement Process (DMP) in detail. The DMP is comprised of three parts: Definition of the measurement chain, including details of the type and number of instru
39、ments to be used and their calibration requirements. An elemental uncertainty analysis, in which all possible sources of both systematic and random error are defined and estimates are made of the uncertainties associated with each error source. A results uncertainty analysis, where the effects of pr
40、opagation of the elemental uncertainties into the results are assessed. Using this procedure, an estimate of the uncertainty of the final results is obtained and can therefore be compared to the original requirement. Where there is a discrepancy, in the sense that the uncertainty is either greater o
41、r smaller than what is demanded, the test plan can be modified, the DMP revised, and a new uncertainty estimate made. The uncertainty analysis gives significant guidance on where the problems are and what needs to be corrected. By iteration of these processes, the test plan can be optimized prior to
42、 or during the initiation of any actual testing work. This optimized plan may then be reviewed and agreed upon by the customer, if necessary, before a final Test Plan is published. Once the test plan is finalized, the next stage is to perform a preliminary test and to review the results obtained. Th
43、e quality of the data can be checked against the expectations from the DMP, and the discrepancies can be investigated. Comparisons are made between the current test results and expected results obtained from similar tests or model simulations. These comparisons provide checks of the uncertainty esti
44、mates and help to identify problems with the test program. The report emphasizes the importance of planning this preliminary test into the program since it offers the last, but most effective opportunity for revisions to the test plan before formal testing commences. Following the execution of the t
45、ests, the actual results must be analyzed and their uncertainties estimated. Since much of the groundwork for this exercise will have been carried out already in an earlier stage, the effort required here is reduced. Finally, a post-test review is recommended, where the results obtained and the unce
46、rtainties associated with them are compared with predictions and discrepancies are investigated. Such investigations should be reported openly and may be used to assist in planning the next similar testing program. 1.2 Concluding Remarks Measurement uncertainty is a tool that can be applied to test
47、programs in order to optimize resources and save money. Sections 3 through 8 of this document describe how this tool is used, with an example. Figure 1 gives a roadmap of the report.FIGURE 1 - AIR5925 MAP SAE AIR5925A Page 6 of 56 2. REFERENCES 2.1 Applicable Documents The following publications for
48、m 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 references cited herei
49、n, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 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.2.1.1.1 AIR1678B, Uncertainty of In-Flight Thrust Determination 2.1.1.2 AIR17
