To: Helo Teacher
Regarding left cyclic in a hover. I was under the impression that the mast was tilted to counter the propeller effect of the tail rotor.
I read the FAA Rotorcraft Flying Handbook and it agrees with your statement about inflow and cyclic stick position. Of course the same handbook addresses helicopter aerodynamics by describing the aerodynamics of an autogyro. However I will accept your explanation.
Regarding a 20 degree offset of the stick, that is not what I am saying. I stated that the pitch horn must travel an additional 18 degrees in rotation in order to achieve full pitch input. It is the displacement of the stick relative to the rigged neutral to compensate for the 18 degree difference.
That might equate to only several degrees of displacement from the rigged neutral setting of the cyclic. What with moving the cyclic to the left to compensate for propeller effect and then moving it to compensate for the inflow how do you actually know where the cyclic is when you are flying forward?
One pilot mentioned that with the cyclic grip in his hands he rests his arm on his lap and it is in that way he knows where the stick is. I have a question. which way and in what direction did he move the stick before achieving what he felt was the right place prior to resting his arm on his lap?
Regarding flapping angles and or loads I was not specifically addressing zero G. Although the rotor system is not controllable at that time, flapping angles and loads are still present. I was addressing any maneuver that would generate high enough angles as to transmit the associated loads into the rotorhead, via contact of the spindle with the internal down stops for the blades, resulting in mast bumping.
Now back to the questions in my post above.
How do you (or for that matter anyone) explain the statements made in the pro Robinson website which:
Provided an illustration of both a Bell and Robinson rotorhead and included a listing of all of the major parts thereof.
They then went into a discussion of gyroscopic precession and explained what it was.
To illustrate Gyroscopic precession relative to pitch input, still talking about the Robinson helicopter, they provided a diagram that applied to the Bell. Was it because they didn't want to address the 18 degree disparity of the two systems or, they assumed that they were the same.
For any given pitch input the swashplates on both helicopters move in the same manner. To fly forward or backward the swashplate tips forward or backwards. To fly left or right the swashplates tip left or right. On the Bell the pitch horn leads by 90 degrees and on the Robinson it leads by approximately 72 degrees.
If as the Robinson website says,the Robinson has a phase angle of 90 degrees just like a Bell please tell me how the Robinson compensates for the 18 degree difference and still has a precession angle of 90 degrees placing the tip path down over the nose.
Instead of commenting on what I said relative to stick position in my above post please log onto the websites provided and download the diagrams. All of the explanations are on the diagram. I would also suggest you ask for a report via my email address. I would be more than happy to send it.
I have one question of a personal nature. Where is Kenora? On the map I have I checked the X/Y locaters and it puts you in New York State just above Buffalo
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The Cat
[This message has been edited by Lu Zuckerman (edited 24 November 2000).]