1. The information contained in this document is Volvo Aero Corporation Proprietary Information and it shall not – either in its original or in any modified form, in whole or in part – be reproduced, disclosed to a third party, or used for any purpose other than that for which it is supplied, without the written consent of Volvo Aero Corporation. Any infringement of these conditions will be liable to legal action. Derivation of diagnostic requirements for a distributed UAV turbofan engine control system

2. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 2 Content  Background on gas turbine engine control system evolution  Control system and target application used in this study  Safety related requirements and analysis method  Analysis result and conclusions Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19

3. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 3 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Jet engine control system begins Patent GB588083A, Fuel system 1940 1960 1980 2000 2020

4. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 4 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Gas turbine control system evolution Increase of pressure ratios, higher turbine inlet temperatures along with axial compressors and afterburning increased the stress of internal components and the need for more precise control. The evolution of more and more complex hydromechanical control systems continued during the 50’s and 60’s. 1940 1960 1980 2000 2020 P3T4

5. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 5 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 RM8 GG-control

6. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 6 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 RM8 A/B control

7. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 7 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Electronic Gas turbine control systems  Continued evolution of aircraft performance triggered the need for rapid acceleration/deceleration and surge free operation in military applications. Normal operation should not require attention from the pilot. 1940 1960 1980 2000 2020 The invention of the transistor in the late 40’s and the introduction of integrated circuits in the 60’s enabled more advanced control systems. Electronic ’supervisory control systems’ were added to the hydro mechanical systems to improve functionality and accuracy of the control system. Analog control units have gradually been replaced with digital units.

8. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 8 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Gas turbine control systems today 1940 1960 1980 2000 2020 Today’s FADEC systems have orders of magnitude better throughput than the first FADECs, enabling: - High level software development tools. - Faster execution speed. - Monitoring of engine health Issues with safety, reliability, tolerance to (electric) disturbances etc. have been kept under control despite the rapid technology evolution of electronics.

9. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 9 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Gas turbine control systems today Various benefits and drawbacks of both hydromechanical and electronic control systems have all been outmatched compared to the benefits of using software to implement complex control and monitoring functions. 1940 1960 1980 2000 2020 ©SAFRAN, All rights reserved During the past 35-40 years, FADEC systems have matured.

10. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 10 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Gas turbine control systems today 1940 1960 1980 2000 2020 FADECs have become generic. High complexity, reduction of cost, improved maintenance etc. can be dealt with in different ways, for example have Hispano-Suiza and BAE Systems created FADEC International. http://www.geae.com/education/theatre/genx/ The ‘FADEC 3’ design is currently used in GEnx, GE90-115B, GE CF6, CFM56 and GP7200 engines.

11. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 11 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Gas turbine control systems tomorrow 1940 1960 1980 2000 2020 Desired characteristics: o Lower cost (non-recurring and recurring) o Lower weight o Better reliability o Better flexibility for hardware upgrade o Better Engine Monitoring Capability How?

12. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 12 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Gas turbine control systems tomorrow InputSignal processingOutput Actuator Sensor InputSignal processingOutput Actuator Sensor Cost Weight Reliability Flexibility Monitoring 1940 1960 1980 2000 2020

13. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 13 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 UAV gas turbine control system 1940 1960 1980 2000 2020 FVG CVG WFM T5 T1 NLNH PS3 T25 Inlet FanCompr. Turbines T1 FVG NL T25 CVG NH PS3 WFM T5 Engine inlet temperature Variable guide vanes in the fan Fan speed Compressor inlet temperature Variable guide vanes in the compressor Compressor speed Compressor outlet pressure Fuel flow Low pressure turbine temperature The probability for improper engine thrust shall be less than 10 -5. The probability for mission abort shall be less than 10 -3. The probability for an unscheduled maintenance action after a mission shall be less than 10 -3. The probability that a single failure in the control system causes improper thrust shall be less than 10 -7. Requirements Power1 Power2 External bus WFM2 T1 NLT25NHPS3T5 CVG1 CVG2WFM1 FVG CU1 CU2

14. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 14 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Control system analysis Node Permanent fault rate, p Transient fault rate, t Sensor10 -5 per hour10 -3 per hour Servo10 -5 per hour10 -3 per hour CU10 -5 per hour10 -3 per hour Power2. 10 -5 per hour0 Bus5. 10 -6 per hour0 EventRate Repair  r =360 per hour False alarm rate f = 10 -2 per hour

15. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 15 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Control system analysis

16. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 16 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Control system analysis

17. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 17 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Control system analysis

18. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 18 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Control system analysis result Category cctcct ccpccp ccsccs Failure prob [. 10 -6 /h] Comments A 11don’t care 0.003 Ideal system, lower failure bound B 0.99 0.9990.136 Excellent coverage C 0.99 1.32 Very good coverage on all levels. 0.990.90.991.44 0.9 0.9991.56 D 0.5 16.12 An ideal system level coverage compensates for bad node level coverage. 0.99 0.956.57

19. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 19 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Control system analysis result Category cctcct ccpccp ccsccs Failure prob [. 10 -6 /h] Comments E 0.99 0.913.1 The coverage of transient faults and system coverage are most important 0.90.99 13.3 0.9 0.9913.4 0.990.9 14.3 F 0.90.990.9130 Even though the node level diagnostics is excellent, the overall failure probability is high if system level error diagnostics is missing. 0.99 0131 0.9 132 0.990.90143 000.99156 G 0.90.9901300 Just for comparison. 0.9 01310 000.91340 0.5 06540 00013000

20. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 20 Conclusion Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19  A method to translate high level safety and reliability requirements into coverage factors for a distributed gas turbine control system has been presented.  The coverage factors represent diagnostic requirements, i.e. the required error handling capability for the nodes of the system.  The method use simple Markov chains in combination with Fault Tree Analysis to capture essential safety related properties.  Distributed system architecture is the way forward to manage the never ending complexity growth of ’FADEC’ systems. It allows for: Partitioning of a complex system into simpler sub systems Flexibility to add more functionality and computational capacity Physical distribution enables standardisation of nodes and competition among manufacturers

21. Volvo Aero Corporation Proprietary Information. This information is subject to restrictions on first page. Department, Name 10110 Utg. 12 Slide 21 Flygteknik 2010 - Derivation of diagnostic requirements 2010-10-19 Thank You for your attention and welcome to