Development of envelope protection systems for rotorcraft

Modern rotorcraft are constrained by complex flight envelopes. Simplified operational envelopes restrict the true maneuvering performance of the aircraft. Tactile cueing systems can be used to protect against envelope violations and provide carefree handling qualities, but require algorithms to detect approaching limits before they are exceeded. Dynamic trim estimation using neural networks is an effective method for detecting limits that are reached in quasi-steady flight. The present study extends this method to include adaptation to variations in weight and balance parameters or modeling errors. The system is applied to provide angle of attack and load factor protection on the XV-15. A modified algorithm is developed to provide envelope cueing for parameters that impinge on limits in the transient response and is applied to limit longitudinal flapping on the XV-15.