Ground Resonance Rattles Brazilian Chopper to Bits
What: Corpo de Bombeiros Militar do Estado do Pará Helibras HB 350BA Esquilo
Where: Benevides Brazil
When: Feb 22, 2012
Who: 4 aboard, no fatalities
Why: The rescue chopper vibrated itself apart after landing.
“Ground resonance” occurs when a sitting helicopter’s rotors become unbalanced while spinning. A resident expert says this can happen because of a hard landing; the best way to get it to stop is to pull collective and break contact with the ground. (At the time, that would feel counter intuitive, I would think!)