Federal R & D—Outmoded Management Policies

Investigation of dynamic structural models suitable for the simulation of large aircraft

“…Upon investigation, it was discovered that the fuselage and tail had two principal low-frequency modes of vibration creating a self-excited oscillation involving coupling between the modes. 1 In one mode, the left and right elevators oscillated about their hinges 180° out of phase, while in another mode the fuselage oscillated in torsion. 1 The early problems faced by Professor Langley and by the Handley Page 0/400 bomber showed an early indication of the interdisciplinary role that aeroelasticity would play in not only aircraft control but also in structural design.…”

“…1 In one mode, the left and right elevators oscillated about their hinges 180° out of phase, while in another mode the fuselage oscillated in torsion. 1 The early problems faced by Professor Langley and by the Handley Page 0/400 bomber showed an early indication of the interdisciplinary role that aeroelasticity would play in not only aircraft control but also in structural design. The size and flexibility of modem aircraft have created a type of aircraft in which the structural modes are on the same order of magnitude as the short-period rigid body modes.…”

“…Perhaps the first designer affected by aeroelasticity was Professor Samuel P. Langley of the Smithsonian Institution. 1 The best explanation given for the wing failure which destroyed Langley's machine on the Potomac River houseboat in 1903 was wing torsional divergence. 1 Theoretically, torsional divergence speed is the speed at which the wing, untwisted, experiences no aerodynamic moments.…”