Thrust control malfunction accommodation system and method

#The invention relates generally to thrust controls for aircraft engines, and more specifically to a thrust control system to promptly correct a thrust control malfunction, thereby ensuring that no single fault of an aircraft's propulsion control system will result in an unaccommodated thrust control malfunction.

#Malfunctions in aircraft power plant thrust control systems can result in uncontrollable high engine power levels that are potentially hazardous or catastrophic for aircraft operation. A particularly hazardous situation is when a thrust control system failure results in one of the aircraft's engines continuing to operate at a high power condition and not responding to a throttle command to reduce power during takeoff, approach or landing. Typically, when this failure mode occurs, the actual thrust either increases to a significantly higher than commanded thrust and/or remains at a high level when the thrust levers are set for low thrust. If one engine fails to respond to a command to reduce power, a high asymmetric thrust condition occurs, creating a high lateral force on the aircraft that is very difficult for a pilot to control. Even if the asymmetry can be controlled, the excess thrust may cause the airplane's stopping distance to exceed the available runway length. In such cases, exceptional skills and prompt flight crew action may not be adequate to avoid risks to aircraft safety.

#Some recent thrust limiting systems have reduced the potential for this failure mode to occur, but have not eliminated the risk. Known limiting systems include automatic engine shutdown and thrust cutback features, but are designed to be activated only if the engine rotor speed exceeds specified levels. These levels will not necessarily be exceeded in the event of a thrust control malfunction. Increased traffic and congestion, as well as the increased use of parallel taxiways and runways have increased the potential for an aircraft experiencing such a failure to impact other aircraft, ground support equipment, or a terminal. Thus, such a failure could potentially impact the occupants of multiple aircraft, terminal spaces, and/or ground support personnel.

#The present invention will become more fully understood from the detailed description and accompanying drawings, wherein;

#FIG. 1 is a schematic of an aircraft engine control system that includes a thrust control malfunction accommodation (TCMA) circuit, in accordance with a preferred embodiment of the present invention;

#FIG. 2 is a graphical representation showing the execution of a software package included in the engine control system shown in FIG. 1, during four scenarios of normal engine operation; and

#FIG. 1 is a schematic of an aircraft engine control system 10, in accordance with a preferred embodiment of the present invention, including a thrust control malfunction accommodation (TCMA) circuit 16. In this preferred embodiment, TCMA circuit 16 is included in an electronic engine control (EEC) 18 that is mounted on an aircraft engine. EEC 18 includes a first processing subsystem 20a, or channel A, and a second processing subsystem 20b, or channel B. TCMA circuit 16 includes a first EEC channel relay switch 22, a second EEC channel relay switch 28 and a diode 32. First EEC processing subsystem 20a, i.e. channel A, and second EEC processing subsystem 20b, i.e. channel B, each have a dedicated processor 34, a dedicated memory device (not shown), and dedicated input sensors (not shown). Unless otherwise specified, the adjectives “first” and “second”, as used herein are not intended to imply an order of importance or a sequence, but merely used to arbitrarily identify two similar objects or components.

#System 10 includes the EEC 18, a thrust lever 36, digital Aeronautical Radio Incorporated (ARINC) data bus lines 46, an electrical load management system (ELMS) 52, a high pressure shutoff valve (HPSOV) 58, and a hydro mechanical unit (HMU) 64. Thrust lever 36 is electrically connected to EEC processing subsystems 20a and 20b. ARINC data bus lines 46 are electrically connected to EEC 18. ELMS 52 is electrically connected to TCMA circuit 16 within EEC 18 and HPSOV 58. HMU 64 is electrically connected between HPSOV 58 and EEC 18. HMU 64 includes a first fuel metering valve (FMV) torque motor 66, a second FMV torque motor 68, and a feedback device 70. First torque motor 66 is controlled by EEC first processing subsystem 20a and second torque motor 68 is controlled by EEC second processing subsystem 20b.

#Additionally, system 10 includes a first voltage input 72 and a second voltage input 76 that supply predetermined voltages to system 10, for example 28 volts DC. First input 72 is electrically connected to a fire relay switch 82 and second input 76 is electrically connected to a run coil 88 and a cutoff coil 96, both included in ELMS 52. A HPSOV closed coil 100 is connected to fire relay switch 82, an ELMS relay switch 102 and diode 32. Furthermore, system 10 includes a fuel control relay switch 108 that is electrically connected to run coil 88 and cutoff coil 96. When in the run position, ELMS relay switch 102 is electrically connected to EEC relay switch 22. When in the cutoff position, ELMS relay switch 102 is connected to HPSOV closed relay switch 100 and diode 32. A HPSOV open coil 118 is electrically connected to EEC 18 at an output 124.