To: Nick Lappos
What you said about properly serviced oleo struts preventing ground resonance is not always true. In the icebreaker illustration I provided above the struts were properly serviced and they were doing what they were supposed to do when exposed to the externally applied loads caused by the rolling motion of the ship. The helicopter in question was an S-51, which has a very high CG, and it is mounted on tricycle landing gear. Any externally applied load will cause the helicopter to rock/roll on the struts and even though the wheels are up to pressure there is a rolling motion reacted by the tires. The rotor system has independent flapping and lag hinges similar to the heads on the CH-47. As the rotor is brought up to speed the blades will hang back and not being equally disposed at 120-degrees there will be an imbalance in the rotor system until it is brought up to speed. It was during this transitionary period that the out of balance rotor system and the movement of the helicopter on the struts would interact and exacerbate the situation. Because of this we could not keep the helicopter tied down and the only thing keeping it in place were the chocks on the three wheels. If the condition did not worsen then the pilot would keep it on the deck until released by the ships Captain. If the condition did worsen the pilot would immediately lift off to break contact with the rolling deck.
Elephants can be chased away using the method you described but penguins can not be chased from you mind. For the rest of the long weekend try not to think of penguins.