As ground resonance is called a dynamic interaction in helicopters between rotor system and the helicopter airframe at the landing apparatus . This condition is dangerous as it can destroy the helicopter within a very short time.
Ground resonance is often triggered by the landing impact, which acts on the landing device and thereby causes a temporary deformation of the rotor system. The rotor mast is accelerated in one direction relative to the rotor circle due to the ground force. Swivel joints or the elastic mounting of the rotor blades in the case of jointless rotor heads lead to a displacement of the rotor blades in the rotor plane, which creates an imbalance. If the oscillation caused by this imbalance hits the natural frequency of the helicopter on the landing gear, the entire helicopter begins to oscillate.
In terms of design, attempts are made to suppress the ground resonance by means of damper systems in the rotor and the landing device. The natural frequency can also be shifted to less critical areas by designing the helicopter cell and landing device. However, ground resonance cannot be completely ruled out. In order to escape an incipient ground resonance, the pilot must immediately take off again in order to eliminate the reaction forces of the landing device (see video).
A well-known example is the V1 prototype of the Bo 105 , which was completely destroyed due to ground resonance before the actual flight tests began.
- Ground resonance Boeing CH-47 Chinook - side view
- Ground resonance Boeing CH-47 Chinook - rear view
- Establishing ground resonance and emergency procedures
- Video on Spiegel.de
- heli-chair.com: Ground Resonance of a Helicopter. Retrieved February 18, 2012 .
- Walter Bittner: Flight mechanics of the helicopter. Technology, the flight dynamics system helicopters, flight stability, controllability . 3rd, updated edition. Springer, Berlin et al. 2009, ISBN 978-3-540-88971-7 , pp. 92 ff .
- helis.com: What is Ground Resonance. Retrieved February 18, 2012 .
- Bückeburg helicopter museum: Bölkow Bo-105B. (No longer available online.) Archived from the original on October 18, 2012 ; Retrieved March 2, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- military-page.de: MBB (Eurocopter) Bo105. (No longer available online.) Archived from the original on June 14, 2009 ; Retrieved March 2, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.