To: Helmet Fire
Let’s first discuss comparative religion. Each religion (Judeo Christian) has it’s own bible and they have their own liturgy yet when it comes down to it they worship the same god. In the helicopter religion there are different liturgies and there are different bibles yet when you get down to basics the bibles and the liturgies describe the same thing but they employ different words. Precession is one point. One religion teaches aerodynamic precession and the other teaches gyroscopic precession. It seems that the definition of coning angle fits into this category. Whether we are talking religion relating to god or the helicopter religion it is difficult to proselytize one individual and bring him into your religion especially if you are trying to convince that person that your religious concepts are better and more pure than his concepts.
Here are a few excerpts from the bible used in my religious worship of helicopters. These words are drawn from the famous blue bible and apply to the worship of Sikorsky helicopters. This bible also addresses helicopters of other faiths. The Bible is the Sikorsky Helicopter Flight Theory for Pilots and Mechanics. This bible unlike other bibles contains illustrations as well as text.
I will speak from the illustrations and then quote from the text.
In the first illustration it describes a blade that has 50,000 pounds of centrifugal force. With no collective added the blade would be in the RADIAL position. With the addition of collective the blade will be generating 3,600 pounds of lift. The blade will rise until the lift forces are balanced out by the centrifugal force. This creates a resultant or ANGLE. It is easy to see if collective were not applied there would be no resultant (ANGLE). In order to raise at the tip to produce the resultant the blade must move on its’ hinge or elastomeric bearing. This upward movement is called FLAPPING. Unlike cyclic flapping the blade flaps up and will stay there until rotor speed increases or decreases or weight is added to the helicopter or weight is dropped from the helicopter.
With reference to the above description the text reads: With reference to figure 18, it may be seen that the rotor blades in rotating form an inverted cone with its’ apex centered at the main rotor shaft. This situation gives rise to the expression “CONING ANGLE”. The coning angle will be less with a low gross weight and greater with a higher gross weight.
The application of cyclic pitch will cause the disc to tilt (oh yes, disc is referenced in the text as well) and this tilting will alter the resultant relative to the radial plane and cause a change in the cone angle. This is what my bible tell me please tell me what description of coning angle is preached in your bible.
Incidentally, flapping to equality is not referenced in my bible. However, gyroscopic precession is.
If you do not understand what is being described as driven axis and driving axis you do not understand what causes leading and lagging. If there is no difference between these two elements there is no leading and lagging. If the difference is minor then lead and lag are minor. The greater the difference the greater the magnitude of leading and lagging. Now, in order to get this difference you must have precession whether it be aerodynamic or gyroscopic. In order to obtain the difference you must have cyclic input. With cyclic input the blades will flap cyclically and all of the other stuff follows. If you did not displace the cyclic there would be; no change in the cone angle, the disc would not precess, there would be no difference between the driven and driving axes and there would be no lead and lag. Every thing that happens in the rotor system is completely interrelated. I’m sure that your bible covers these subjects and based on the arguments on this thread (and others) I’m sure the words used to describe these phenomena are different.
[ 29 November 2001: Message edited by: Lu Zuckerman ]