Simulation based verification is a critical element of the development of an aircraft engine’s Full Authority Digital Engine Controller (FADEC). The FADEC is comprised of the Electronic Engine Controller (EEC) providing control and safety for the gas turbine engine, the fuel metering unit, the engine health monitoring system, and several other components. Real-time, hardware-in-the-loop simulation rigs are used to perform development, integration, and certification tests on each component of the FADEC and on the combined, integrated set of components. These simulation based test systems are used to test the FADEC to demonstrate that it is compliant with the airworthiness requirements and to generate the evidence that is submitted to the regulator body to achieve certification.
The airworthiness requirements for the EEC can be summarized as:
- The EEC must match the control system percent of available power or thrust controlled in both normal operation and failure condition, and range of control, specified for the engine – in other words, the EEC should operate as documented in the engine manuals
- The EEC must be designed and constructed so that any failure of aircraft-supplied power or data will not result in an unacceptable change in power or thrust, or prevent continued safe operation of the engine
- The EEC must be designed and constructed so that no single failure or malfunction, or probable combination of failures of electrical or electronic components of the control system, results in an unsafe condition
- The EEC must have environmental limits, including transients caused by lightning strikes, specified in the instruction manual – and environmental tests must be performed to demonstrate
- The EEC must have all associated software designed and implemented to prevent errors that would result in an unacceptable loss of power or thrust, or other unsafe condition, and have the method used to design and implement the software approved
The above airworthiness requirements are for the EEC only. Beyond the requirements listed above, the EEC and other safety-critical electronic systems found in an aircraft must also have software developed in compliance with DO-178B/C which dictates software certification requirements and process. Furthermore, there is a range of other requirements associated with the complete gas turbine engine (ex: fire protection, bird ingestion, parts manufacturing, life-limited parts, etc).
Certification is obtained by producing evidence to show that the engine’s FADEC meets these requirements. Evidence is generated using analysis, open-loop test methods, and simulation-based closed-loop test methods. Simulation based testing of the FADEC is typically the responsibility of the engine and FADEC supplier(s).
Engine Test Rig
A gas turbine engine test rig is a tool used by all major aircraft engine manufacturers and FADEC component suppliers. The test rig combines:
- real-time simulation processors
- sensor emulation I/O:
- thermocouple sensors
- pressure sensors
- LVDT sensors
- resolver sensors
- strain gauge sensors
- fuel flow sensors
- potentiometer sensors
- torque sensors
- actuator and load emulation I/O:
- torque motor emulators
- solenoid emulators
- stepper motor emulators
- igniter emulators
- aircraft databus (ARINC-429, ARINC-664, MIL-STD-1553) interface and emulation
- emulated aircraft power
- reconfigurable signal mapping interface
- electrical fault insertion system
- gas turbine simulation model
- software framework providing real-time services on the rig and desktop tools for performing comprehensive test related activities
Applied Dynamics is the largest commercial supplier of gas turbine engine test rigs. The ADvantage Framework provides the software platform that layers on top of commercial-off-the-shelf computer equipment to create a cost effective solution that can be seamlessly woven into our customers development and verification processes.