To: 430 Driver
Just imagine if it happened to you without an instructor. If you put it into autorotation and the centrifugal twisting moment didn't return the tail rotor blades to neutral pitch, where would you be?
It just proves that Murphys' law can strike at any time. A similar fracture occured on the cyclic of an R22 in California and the helicopter crashed. Robinson ended up strengthening the assembly.
If Krylian is reading this, Robinson didn't get it right the first time and it took the loss of a pilot and a helicopter to bring it to their attention. Many posts ago I mentioned to a pilot that wanted to purchase an R44 Raven with hydraulic boost. I told him to have the dealer show him if Robinson had modified the upper controls or, if they were still the same as the original R44. If they are the same, the same problem of control linkage failure can occur.
I believe the cyclic failed due to vibratory feedback in the control system. By putting hydraulics in the R44 the servos will eliminate the feedback into the lower control system thus exposing the upper controls to even greater loads due to the blockage provided by the servos. The pilot however will notice a great improvement over the standard R44 and not pay any attention to what is going on in the control system above him.
As an aside I would make this suggestion to any pilot that flies a Bell helicopter with NodaMatic transmission suspension. This suspension provides the smooth ride that all Bell pilots talk about.
If it is possible to remove an inspection panel from the structure containing the transmission assembly have someone look into the panel opening when in flight. It will scare the hell out of you. The dynamic system is beating itself to death but the passengers and pilots get an extremely smooth ride.
To: Kyrilian, let's see if they get it right the first time. Also, let's see if the hydraulics system designers coordinated their efforts with the control and aerodynamics engineers. Not like the engineer at Sikorsky (see above).
To Try_Cyclic
You tell me that I am blinded by my beliefs and will not let any counter argument sway me. From my point of view, you are in the same boat blinded by your loyalty to Robinson helicopters. This is commendable but how do you feel when I tell you that there were 32 loss of control accidents involving rotor loss or rotor incursion with a lot of loss of life and all of it was attributed to pilot error. There were many other loss of control accidents and all were attributed to pilot error according to Jim Hall of the NTSB. Did you read the newspaper article I posted above. It pretty well explains why it is always pilot error.
Jim Hall of the NTSB stated that there may have been more in Europe and in other countries where the FAA and NTSB have no jurisdiction. However, if an investigation was made by the local authorities the FAA and NTSB may not have been there but you know who or his representatives were.
Here we go again. On a Bell if the rotor flaps there is no effect on the phase angle but there is an effect due to pitch coupling which does not relate to the phase angle. Read my posts above. If using your words the Robinson blades flap around the teeter point then there is no pitch coupling. The only way you get pitch coupling on a Robinson is if the blades flap (Move up or down)on the cone hinge in relation to the rotorhead. Other wise it moves as a composite assembly and there is no pitch coupling.
Take a close look at a Robinson swashplate. The 18 degree (approximate) difference is caused by the fact that the pitch horn can't pass the cone hinge. When the blades are disposed over the lateral axis on both a Bell and a Robinson, move the cyclic in any direction and both swashplates move in the same manner.
When the blades on the Bell are in the lateral position and the pilot inputs forward cyclic the pitch horn/pitch link is over the lowest point on the swashplate which means that the advancing blade is at its lowest pitch point. Ths means that due to precession the blade will flap down over the nose.
Now, check the Robinson with the blades in the same position. Move the cyclic so that the swash plate is at its; lowest point over the longitudinal axis. Check where the pitch horn/pitch link are. In order to reach the lowest point the rotating swashplate must rotate another 18 degrees (approximately).
Since the pitch change on the advancing blade is continuing during this 18 degree transition it will not achieve its' lowest pitch until the blade has moved 18 degrees (approximately) past the lateral axis.
With a phase angle of 90 degrees the blades will dip 90 degrees later to the left after the maximum input is made. How difficult is it to understand this scenario?
The two websites that I located are identical. The text was prepared by Paul Cantrell. So what. I stated that the websites were pro Robinson and most likely had the support of Robinson.
The point I made on a previous post was that they discussed the Robinson rotor system and compared it to a Bell 206 rotor head. The text lead you into the discussion of gyroscopic precession and said that it applied to both helicopters. However, when they presented a diagram showing input vs results they used a diagram for a Bell Helicopter and not a Robinson. To do otherwise would expose the secret and it would be contrary to the Robinson training program. At least, those are my feelings.
In a previous post I asked for a descripton in laymans terms how the Robinson blades move in the same way as those of a Bell 206 and achieve a 90 degree phase angle and, dip down over the nose.
Can you provide the explanation and it can come from a Robinson training manual if you wish.
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The Cat
[This message has been edited by Lu Zuckerman (edited 26 November 2000).]
[This message has been edited by Lu Zuckerman (edited 26 November 2000).]