Effect of multiple engine placement on aeroelastic trim and stability of flying wing aircraft Conference

cited authors

  • Mardanpour, P; Richards, PW; Nabipour, O; Hodges, DH

fiu authors


  • Effects of multiple engine placement on utter characteristics of a back- swept flying wing resembling the HORTEN IV are investigated using the code NATASHA (Nonlinear Aeroelastic Trim And Stability of HALE Air- craft). Four identical engines with defined mass, inertia, and angular mo- mentum are placed in different locations along the span with different offsets from the elastic axis while fixing the location of the aircraft c.g. The aircraft experiences body freedom utter along with non-oscillatory instabilities that originate from flight dynamics. Multiple engine placement increases utter speed particularly when the engines are placed in the outboard por- tion of the wing (60% to 70% span), forward of the elastic axis, while the lift to drag ratio is affected negligibly. The behavior of the sub- and supercrit- ical eigenvalues is studied for two cases of engine placement. NATASHA captures a hump body-freedom utter with low frequency for the clean wing case, which disappears as the engines are placed on the wings. In neither case is there any apparent coalescence between the unstable modes. NATASHA captures other non-oscillatory unstable roots with very small amplitude, apparently originating with flight dynamics. For the clean-wing case, in the absence of aerodynamic and gravitational forces, the regions of minimum kinetic energy density for the first and third bending modes are located around 60% span. For the second mode, this kinetic energy density has local minima around the 20% and 80% span. The regions of minimum kinetic energy of these modes are in agreement with calculations that show a noticeable increase in utter speed at these regions if engines are placed forward of the elastic axis. © 2012 AIAA.

publication date

  • August 15, 2013