To: Grey Area
I find this very difficult to say, as it may seem like a personal attack on you as an Instructor.
I ran a training program for the U S Army a long time ago. I managed my department, which dealt with flight controls and flight theory for three different types of Sikorsky helicopters. I taught mechanics and maintenance officers. When I started on this job I had just came from Sikorsky and while at Sikorsky I attended seven schools on different helicopters including auto pilot school. After finishing the classroom studies I worked on the shop floor and did everything from riveting to flight test. Oh yes, when I was In the USCG I attended two other Sikorsky schools.
When I started to teach I knew everything there was to know about Sikorsky helicopters. My students were in most cases high school graduates with limited mechanical experience. When they got to my classes they had only completed a two-week course on rotorblade repair. Knowing what I knew of the classes that they were yet to attend, I not only taught flight controls I taught hydraulics, dynamic systems and power train. Some really fantastic training devices that replicated the flight controls and dynamics systems of the three helicopters enabled this.
When I was on the platform I was dead serious and I taught what I had learned which was well beyond the comprehension level of the students. It took several months before I mellowed out and started to use humor as a means of enhancing education.
It is my personal belief that if you are teaching your flight students as described in your post you are talking over their heads. I would strongly suggest that you teach the technical aspects of helicopter flight theory by simplifying that, that is too technical too fully understand by a neophyte student pilot. Look at the posts above. Fully qualified pilots don’t fully understand what you were talking about. I would guess that the only participant on this forum that understands what you said is Kyrilian and he is a grad student in aeronautics at MIT.
I also take exception to your use of the term control rigging necessary to achieve a 90-degree advance angle. There is a control system and there is rigging of the flight control system. The design of the control system is a fixed entity that the mechanic and/or pilot can do nothing about. On the other hand, the mechanic/pilot can rig the control system to achieve the necessary blade angles and control ranges to achieve safe flight. It is a very good thing to teach the student how his control system works and what happens at the top end when the bottom end is moved in any given direction. The results of that movement are manifested in pitch change that results in lift differential and in turn causes the precession of the blade disc. Also, you state that this is done to show the student about how the 90-degree advance angle is achieved. Here you admit to a 90-degree advance angle but above, you stated that there was no precession angle and that disc tilt was achieved by a bunch of mathematical formulae that I didn’t understand no, did many of our fellow postees.
Your bit about flapping to equality can be better described as the coning angle which is the result of weight being lifted and the centrifugal forces developed by the spinning rotor system.
You teach that centripetal reaction and blade mass will both oppose lift. That’s nice to know but nothing can be done about it as these forces were factored into the design and, it clouds the students' mind.
Just one word in closing “SIMPLIFY”
I’ll shut up for now.
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The Cat
[This message has been edited by Lu Zuckerman (edited 16 December 2000).]