Towards a Failsafe Flight Envelope Protection: The Recovery Shield

Abstract Stall is an Inherent unsafe flight state that has caused catastrophes in civil aviation. Solutions were gradually introduced, such as aerodynamic devices, pilot training, stick shakers and stall warnings. These mitigating, stand alone solutions seemed to have solved the problem to an acceptable level. However, stall as a phenomenon has recurred in a new form, due to changes in operating conditions, flight envelope protection, cockpit automation and crew competence qualifications. Stall accidents, as unintentional loss of pitch control, deal with the malfunctioning of primary flight control surfaces, automation mismanagement and hostile environmental influences during all weather operations. As pitch control is the only primary flight control that has no design redundancy, a new control recovery approach is proposed, introducing new and uncorrupted aerodynamic forces by combining a technical recovery device with enhancing diagnostic abilities for the crew. In designing such a device, synchronizing time required and time available for flight control recovery is a critical design dimension. This contribution elaborates on a control recovery device as an integrated system, consisting of a technical design device, computerized flight control and crew qualifications. A practical application of such a device focuses on stall recovery, as a specific category of flight control recovery.