To: heedm
“There is no magical hand that tries to pull the blade away from the helicopter”.
How can you discount the presence of centrifugal force on a helicopter rotor system? If there were no centrifugal force involved the designers of the rotorhead would not have to build them to take these applied loads. They could only build them strong enough plus a safety factor to accelerate the blades to speed. This would save hundreds of pounds and grossly reduce the cost of the helicopter. When I worked at Sikorsky they were placing the CH-37 Helicopter into service. One of the tests performed involved the installation of strain gages to measure applied and reactive loads. The tensile load on the spindle was 72,000 pounds (approximately). That was for one blade.
If there were no centrifugal forces acting on the blades and reacted by the rotorhead the helicopter would never get off the ground. As I stated previously the centrifugal force balances out the lifting force on the blade and the resultant vector is the cone angle for the rotor system.
As an aside, I once sat in on a training class on the CH-37 at Ft. Eustis, VA and the instructor was asked what would happen if a blade were thrown during flight. His response was that the rotor system being fully articulated the other blades would move to take up the space occupied by the thrown blade. Each blade is balanced to ¼ inch ounce and the rotorhead is balanced to a level close to that. The entire assembly has to be in balance or the centrifugal loading would cause the rotor system to oscillate. A small imbalance would produce small oscillations and a larger imbalance would cause more sever oscillations. The loss of a blade producing 72,000 pounds of centrifugal force would result in total and immediate destruction of the helicopter.
Ask anybody that had the experience of having water collect in a tip cap and then it freezes overnight.
[ 28 November 2001: Message edited by: Lu Zuckerman ]