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 reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2006 SAE International All rights reserved. No part of this publication m
3、ay 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: 724-776-4970 (outside USA)
4、 Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org AIR5120 AEROSPACE INFORMATION REPORT Issued 2006-11 Engine Monitoring System Reliability and Validity RATIONALE This guide was developed to assist program managers, designers, developers, and customers with the devel
5、opment and verification of a highly reliable engine monitoring system. TABLE OF CONTENTS 1. SCOPE 3 1.1 Purpose. 3 1.2 Introduction . 3 2. REFERENCES 3 2.1 Applicable Documents 3 2.1.1 SAE Publications. 4 2.2 Definition of Terms 4 3. GENERAL CONSIDERATIONS . 5 3.1 Overview . 5 3.2 General Validity a
6、nd Reliability Requirements 6 4. DESIGN AND DEVELOPMENT ACTIVITIES.6 4.1 System Specification. 6 4.2 Hardware. 7 4.2.1 Electronics. 8 4.2.2 Sensors . 9 4.2.3 Cabling/Connectors 9 4.3 Software 10 4.3.1 Design . 10 4.3.2 Data Validation 11 4.3.3 EMS Algorithms 11 4.4 EMS BIT 12 4.5 Human Element Facto
7、rs . 13 4.5.1 Introduction . 13 4.5.2 Non Physical Factors 13 4.5.3 Physical Factors 15 4.5.4 Training Impacts 16 4.6 Operational Design Considerations for Introduction and Support of the EMS . 17 4.6.1 Documentation 18 4.6.2 Data Flow 20 4.7 Development and Technology Insertion . 21 5. VERIFICATION
8、 ACTIVITIES 22 5.1 Strategy and Approach . 22 5.2 Simulation Tests 23 5.3 Manufacturers Systems Rig/Bench Testing. 23 5.4 Airframe Systems Integration Laboratory Environment/Iron Bird (Static Aircraft) Facility 24 5.5 Engine Test (Sea Level Static however, systems providing immediate access to the d
9、ata are typically the most costly and may not be implemented. Care must be taken to ensure that the data flow from the aircraft to the ground-based system, as defined during design phase, is validated and adjusted during entry into service. One method of improving efficiency is to compress all data
10、from a flight into a single end-of-leg report that is transmitted at the completion of the flight. This method however increases the time between the data recording and its availability. This must be considered when deciding which methods to use. Finally, the continuous recording or rolling history
11、data is typically used only in the situation that a fault occurs. This type of data provides additional information for troubleshooting the event. However, for the data to be useful, an appropriate quantity of data surrounding any possible event must be recorded. In addition, infrastructure must be
12、in place to quickly access and analyze this information. 4.6.2.3 Within Ground-Based System Once the data reaches the ground-based system, procedures must be available to guide the data analysis and the recommended actions. These procedures must clearly document the operation of any ground-based sof
13、tware and guide the operator in interpreting the results to accomplish any necessary action. The entire data stream should be tested with sample data or seeded faults to ensure that the proper analyses can be performed and appropriate actions initiated. Both accuracy and timeliness of responses shou
14、ld be evaluated. 4.7 Development and Technology Insertion In certain applications the specified requirements of the EMS functionality or system implementation are outside the capabilities of mature computational techniques and systems but are yet known to exist. Implementation of the enhanced techni
15、ques or technologies is therefore known to be required at some point in the EMS life cycle. This may be in the form of new hardware such as sensors or electronic units or software. In some cases advanced software techniques that improve data interpretation and correlation may achieve the specified r
16、equirements. When developing an EMS, consideration of both the initial and long term reliability and the associated development path is important. Proactive management of that growth activity must also be included during the development process to maximize systems validity and reliability. All of th
17、e reliability and validity considerations for hardware and software development mentioned previously apply during the development and insertion of maturing technology. Two potential benefits that may exist during this phase that may not have existed during the original development phase are the exis
18、tence of actual operational data and an operational platform on which final verification testing can be executed. Such actual data can facilitate a more reliable system. The process will typically include: Review of the available signal data, analysis and correlation procedures Identification of new
19、 analysis, processing and correlation and integration techniques Testing of the new techniques on existing data, covering healthy and faulty engine conditions Initial assessment of diagnostic and prognostic capabilities Initial assessment of False Alarm Rates and probability of detection Copyright S
20、AE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5120 - 22 - Review of implementation options and requirements (e.g., whether the techniques should be incorporated into the airborne or ground based part o
21、f the system) Development testing Verification testing (e.g., bench testing of the engine or via an implementation plan which phases the introduction of the improvement) 5. VERIFICATION ACTIVITIES 5.1 Strategy and Approach Verification of EMS performance should be viewed as a process and not just a
22、formal test sequence at the end of the engine development cycle. Realistic testing at the appropriate level is necessary throughout the design and development process. The earlier in the design cycle that problems can be uncovered and addressed the more cost effective the process will become and the
23、 more likely a successful production introduction will result. The strategy of tiered verification through simulation test, rig/bench test, factory and flight test, etc. enables an EMS reliability growth process. Further reliability growth is likely after the system has been fielded and the engine a
24、nd EMS continue to mature (refer to Section 6). Formal verification of specific EMS functions can be addressed at each of these test tiers, to a greater or lesser extent, depending upon the specific functions. For example, the EMS diagnostic algorithms that utilize engine and control system sensor d
25、ata can be well exercised with a simulation test approach. Engine and control system modeling is a fundamental part of the design/development process and therefore use can be made of these tools for EMS verification activities. Other EMS functions, such as oil debris detection, are better addressed
26、at the rig or bench test phase, where the system can be exposed to critical physical properties such oil flow, temperature, air entrainment etc. It is important to recognize that each EMS function is adequately verified starting at the earliest practical stage in the design/development process. The
27、construction of a verification matrix can be of use in ensuring an adequate approach for a complex EMS. TABLE 1 - PARTIAL EXAMPLE OF EMS VERIFICATION MATRIX EMS Function Simulation Rig/Bench Aircraft Iron Bird (i.e., static aircraft) Engine Test Flight Test Oil Debris Algorithm Sensing Perf. System
28、Perf Fault Report System Perf System Perf Diagnostics Algorithms Algorithms System Perf Fault Reports Data Transfer Algorithms System Perf System Perf Life Usage Algorithms Algorithms Data Transfer System Perf System Perf Vibration Algorithms Algorithms Fault Report System Perf System Perf In genera
29、l, simulation testing, rig/bench, and iron bird (static aircraft) testing provides the opportunity to verify that the EMS function correctly detects, isolates and reports the appropriate fault(s). Some fault injection may also be practical (ground engine test for example), but the opportunity to per
30、form such tests diminishes due to cost and practical limitations as we move to the right on the above matrix. The major value of engine and flight testing is to ensure that the EMS as a whole functions correctly under real world operating conditions, particularly with respect to data transfer, fault
31、 reporting and those features that utilize transient and aircraft generated data. A primary goal of this testing tier should be to verify that the EMS is free of nuisance faults and false faults. These test tiers can be considered as negative testing approaches. Copyright SAE International Provided
32、by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5120 - 23 - 5.2 Simulation Tests The widespread use of powerful computers in industry nowadays allows extensive simulation testing of EMS algorithms. These tests can include numerou
33、s test vectors to simulate the variations normally experienced in a fleet of engines throughout the life cycle. The setting of EMS algorithm limits and logic gates and the use of diagnostic tools and approaches must account for the following variations: Engine to engine performance quality variation
34、s. Accuracy and bias variations in the sensors utilized by the EMS. The effects of long term deterioration as the engines age and are refurbished. Operating environmental variations such as altitude and mach effects. Consideration must also be given to the engine operational phases during which the
35、EMS is active, e.g., engine starting, power range, transient conditions, flight phases, shutdown, etc. These may be simulated to some degree, depending upon the level of modeling sophistication. In order to include as much practical realism as possible into the simulation test, actual engine and fli
36、ght data from prior engine tests or from similar applications should be acquired. This data should include the typical variability in parameter levels experienced during the various phases of operation and flight. For verification purposes, a suite of test vectors should be developed and executed at
37、 the end of the design phase, formally documenting the status of the design at that time. As subsequent design improvements are made, this verification test should be updated as necessary and rerun. 5.3 Manufacturers Systems Rig/Bench Testing Prior to engine testing, a rig or bench checkout of contr
38、ol system functionally is normally performed. This environment is perhaps the most useful of all test tiers for verifying EMS performance since it offers a flexible test environment in which actual hardware and software can be “exercised” and fault injection performed. Depending upon the capability
39、in the rig facility most or all of the following EMS functionality can be verified: Data flow to/from the EMS and engine/aircraft components, internal to EMS, and between the EMS and external data users. Accuracy and response of dedicated EMS sensors including include oil level, oil pressure/tempera
40、ture, oil debris, and accelerometers. Diagnostic performance by conducting a structured fault injection test. Failures can be injected by physical means such as disconnecting connectors, shorting pins, etc., as well as by uploading temporary software adjustments to the digital engine controller or r
41、ig engine model. Correct storage of EMS data. The properties of the required data stored should be verified, i.e., data records, contents of data records, scaling of parameters etc. Specific EMS subsystem performance. A good example of this is the verification of the oil debris monitor capture and i
42、ndication efficiencies under specified fluid flow, temperature and pressure conditions. Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-,-SAE AIR5120 - 24 - 5.4 Airframe Systems Integration Laboratory
43、Environment/Iron Bird (Static Aircraft) Facility This facility enables verification of the interface(s) between the EMS and the aircraft subsystems. This interface on modern systems is typically a digital bus and two functions can be verified; the electrical characteristics of the bus interface, and
44、 the bus data exchange (to and from the EMS). Traditionally, the Airframer has conducted a verification test at his facility, but there is a trend towards providing most of this capability at the engine manufacturers facility also, to enhance the development process. Typically this integration testi
45、ng can verify the following: EMS fault reporting. The systems integration laboratory usually includes actual airframe computers, avionics etc., connected together in a pseudo aircraft/cockpit configuration. EMS detected faults are typically introduced by simulation and the data flow and display requ
46、irements verified. EMS data stored within aircraft mounted equipment. Verify correct number of data records, contents of data records, scaling of parameters etc. EMS data transfer to and from the aircraft. This may be through removal of solid state memory, interaction with support equipment or even
47、through a wireless interface. Correct response to Bus commands from airframe equipment. 5.5 Engine Test (Sea Level Static typically only a few pilots may fly the aircraft, the “flight test” missions may not bear any relationship with service missions, engine/aircraft installation variations are limi
48、ted, etc. A field service evaluation (military) or compliance testing (commercial) provides real world operation on multiple aircraft with several pilots, mission types, etc., and is therefore more representative of how the EMS will be utilized long term. This type of test series is highly recommend
49、ed since it offers the opportunity to track system performance over several months (6 months or so) or a specific number of flights (perhaps 200 or more) and offers the additional benefit of obtaining real-world user feedback. As for previous system level test tiers, all hits, misses, false alarms, should be thoroug
