Adaptive Controls - Details
Engine health parameters such as compressor pressure ratio deteriorate over time to a variety factors that can be modeled as a function of the number of flight cycles. Modern engine controllers often include multimode capabilities that introduce flight safety problems during mode-switching transitions that occur during throttle accelerations. Significant thrust loss and/or stall margin reductions, for example, have been experienced during throttle accelerations. This problem can be especially serious if the thrust loss is unequal between the left- andright-side engines during slow flight speeds such as during takeoff. In such a situation the airplane may yaw excessively causing pilot overload to correct.
The left-hand graph below illustrates the transient thrust loss during a typical throttle acceleration for a conventional multimode controller. Case 3 (6000 engine cycles) displays an alarming response lag during the mode transition at t=27 seconds that exceeds FAA engine acceleration requirements. The behavior using the N&R developed analytic adaptive control system, the response lag problem is eliminated as depicted in the right-hand graph.
