To: YouWillSee,
First of all I will say (and this may come as a shock to some of you) the Robinson helicopters are just as good as any other helicopter as long as they are flown within the restricted flight envelope.
What started this whole thing off is that I wrote a report and sent it to the NTSB. I made two points in the report among others and every thing stemmed off of that.
The points are:
1) The design of the rotorhead is such that the helicopter does not follow in the same sense as the cyclic stick is moved. The certification requirements state that in order to determine the sense of flight in relation to cyclic stick movement the certifying party must use a device sometimes called a stick plotting board. The FAA allows a slight deviation between stick placement and aircraft direction of flight. This, the FAA says, is caused by pitch coupling. They allow a degree or two but not 18 degrees (approximate). This would have been discovered in the certification process. My report asked the question of Robinson and the FAA if this test was performed and was it determined that the differences between stick movement and flight direction were excessive.
2) The second point related to sideslip and out of trim flight. The certification requirements state that the helicopter under certification demonstrate both flight characteristics. The certification requirements state that the helicopter be flying at .6 VNE and the pilot pushes his left rudder pedal to the stops and hold it in that position and then return the pedals to the neutral position and repeat the test by pushing the right pedal to the stops and holding it there and then return to neutral. The helicopter must demonstrate out of trim by +/- 10 degrees.
Let us assume that these tests were performed and the design of the R22 demonstrated that it was capable of compliance. Several years later the R22 was dropping out of the sky in large numbers because the rotor systems either hit the fuselage or just came off. Because of this, the FAA the NTSB and Robinson launched an investigation. With out a consensus between the three parties the FAA commissioned Georgia Tech Aeronautics department to investigate the matter. Their report among other things concluded that sideslipping and out of trim flight would set up high flapping loads that could cause the rotor problems. As a result of this, the FAA set up the restrictions that are printed on the last page of section four of the respective POHs for the 22 and the 44.
My report asked the question if the restrictions were placed on flight operations and pilots were restricted from sideslipping and out of trim flight then the helicopter no longer met the requirements of certification. If either helicopter were presented now to the FAA and they were told that this helicopter can’t be sideslipped or flown out of trim it would be immediately be rejected.
Regarding stick input during zero G flight let us assume that the pilot has corrected for the 18 degree offset and the cyclic is placed forward and right of the rigged neutral position. As such, the helicopter is flying forward and not to the left. If the helicopter enters the zero G condition with the cyclic in this position the following can happen:
1) If he pulls straight back he will not add to the right roll set up by the tail rotor thrust.
2) If he pulls back and slightly to the left he will add to the right roll component.
3) If he pulls back and further to the left he will compensate for the 18 degree offset and not add to the right roll component
4) If he pulls back and even further to the left he will introduce a left roll component causing high flapping loads and possibly lose his rotor system or cause a rotor incursion.
With the intensity of pucker factor being so high during a zero G condition which direction would you move the cyclic if you were in that situation. Refer to my point 1 above and think about the sense of aircraft movement relative to cyclic stick displacement. Does this sound right? What if these same conditions existed in your automobile?
REGARDING YOUR LAST QUESTION ABOUT CHANGING THE RULES RELATIVE TO RMS Vs. ENGINEERING I WOULD STAND A BETTER CHANCE OF CHANGING THE BIBLE TO RECOGNIZE GOD AS BEING FEMALE.
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The Cat
[This message has been edited by Lu Zuckerman (edited 06 November 2000).]
[This message has been edited by Lu Zuckerman (edited 06 November 2000).]