A Method for Estimating Critical Flight Loads on a Small Aircraft Fuselage Using Numerical Methods, Conventional Design Tools, and Risk Assessment Techniques
The STOLMA One bush plane is a heavily modified version of an existing light aircraft designed for medical evacuations from jungle and short-field runways. The primary structural modifications are a fuselage extension, increased wingspan, increased horizontal tail span, and a loading door in the aft fuselage. For the design, analysis, and testing of the new structure, no aerodynamic data existed, no full-scale wind tunnel was available, and CFD models for the entire aircraft were deemed unreliable. A conservative method for estimating flight loads on the fuselage is presented. Aerodynamic characteristics of the horizontal tail and vertical tail are modelled with a panel method numerical solver. Design calculations are performed for individual components of the flight loads. Flight maneuvers are selected from appropriate flight manuals for the class of aircraft and mission profile under consideration. Load components are combined according to the maneuvers selected within each part of the flight envelope. The discrete portions of the flight envelope are assembled in a risk assessment matrix, and the test loads are selected accordingly. In a selected example, in order to simulate the steep climb portion of a chandelle maneuver, the STOLMA One fuselage extension assembly is tested with a downward load of 2,000 kg located 3.8 m aft of its respective CG. This test is considered a conservative evaluation of the structure’s performance at ultimate loads.
Keywords - Critical Flight Loads, Light Aircraft Testing, Medical Evacuation Aircraft, Panel Method.