Flutter (aviation)
As aeroelastic flutter ( English flutter ) refers to a self-excited oscillation of an aircraft flutter effects of one of the aero-elasticity .
In principle, all parts or masses of the aircraft are involved in this oscillation. The physical influencing variables are the rigid degrees of freedom (translation and rotation) in interaction with the elastic deformations of the aircraft, the mass distribution and the unsteady air forces (on the oscillating aerodynamic surfaces).
Flutter can be influenced by design measures. In general, there is always a limit speed above which flutter occurs. This accordingly limits the safe operating range of the aircraft. Since fluttering usually leads to breakage of the affected component and thus possibly to the crash of the aircraft, special attention is paid to it in the test phase.
The phenomenon first appeared in aircraft in the 1930s, when significantly higher speeds were possible and the mechanisms were initially not understood. Flutter came into the focus of developers for the second time in the 1940s, when it became possible to fly at the speed of sound . For example, at the German Aviation Research Institute in Berlin-Adlershof, u. a. Alfred Teichmann and at the aerodynamic research institute of Hans Georg Küssner worked on it.
Flutter arises when a vibration mode with a second or approximately equal frequency oscillating - for example, a flexural mode and a torsional mode - resonates and these interfere constructively . These natural frequencies are fundamentally due to the design and are excited to different degrees at different flight speeds.
A typical example of the fluttering of aircraft parts are the bending and torsional vibrations of the wings . The rudders ( elevator , rudder , ailerons ) can flutter if the stiffness in the suspension or linkage is too low, which is exacerbated by too much play . Propellers can be excited to flutter by the forces of precession .
Airplane crash caused by flutter in 2006
A tearing of the horizontal stabilizer caused by fluttering led to the crash of a prototype of the Grob G 180 SPn near the works airport on November 29, 2006 and caused the death of the French test pilot Gérard Guillaumaud .
Web links
- Flutter test on the Airbus A380 Video, published November 11, 2009, accessed October 6, 2014
- SB-9 flutter film fluttering at the glider SB 9 of Akaflieg Braunschweig
Individual evidence
- ↑ Aircraft accident data and report in the Aviation Safety Network (English)
- ↑ Investigation report. (PDF; 1 MB) Federal Aircraft Accident Investigation Bureau, April 10, 2010, accessed on May 13, 2013 : “The accident occurred because the horizontal stabilizer was dismantled during flight due to fluttering and the aircraft could no longer be steered as a result . The circumstances that led to the flutter case could not be clearly determined due to a lack of flight data and limited investigation options. "