The role of shock waves was first analyzed by Holt Ashley. A phenomenon that impacts stability of aircraft known as "transonic dip", in which the flutter speed can get close to flight speed, was reported in May 1976 by Farmer and Hanson of the Langley Research Center. Buffeting Buffeting is a high-frequency instability, caused by airflow separation or shock wave oscillations from one object striking another. It is caused by a sudden impulse of load increasing. It is a random forced vibration. Generally it affects the tail unit of the aircraft structure due to air flow downstream of the wing. The methods for buffet detection are: Pressure coefficient diagram Pressure divergence at trailing edge Computing separation from trailing edge based on Mach number Normal force fluctuating divergence Prediction and cure In the period 1950–1970, AGARD developed the Manual on Aeroelasticity which details the processes used in solving and verifying aeroelastic problems along with standard examples that can be used to test numerical solutions. Aeroelasticity involves not just the external aerodynamic loads and the way they change but also the structural, damping and mass characteristics of the aircraft. Prediction involves making a mathematical model of the aircraft as a series of masses connected by springs and dampers which are tuned to represent the dynamic characteristics of the aircraft structure. The model also includes details of applied aerodynamic forces and how they vary. The model can be used to predict the flutter margin and, if necessary, test fixes to potential problems. Small carefully chosen changes to mass distribution and local structural stiffness can be very effective in solving aeroelastic problems. Methods of predicting flutter in linear structures include the p-method, the k-method and the p-k method. For nonlinear systems, flutter is usually interpreted as a limit cycle oscillation (LCO), and methods from the study of dynamical systems can be used to determine the speed at which flutter will occur. Media These videos detail the Active Aeroelastic Wing two-phase NASA-Air Force flight research program to investigate the potential of aerodynamically twisting flexible wings to improve maneuverability of high-performance aircraft at transonic and supersonic speeds, with traditional control surfaces such as ailerons and leading-edge flaps used to induce the twist. Notable aeroelastic failures The original Tacoma Narrows Bridge was destroyed as a result of aeroelastic fluttering. Propeller whirl flutter of the Lockheed L-188 Electra on Braniff Flight 542. 1931 Transcontinental & Western Air Fokker