To: Ho Lung Chun or, can I call you Ho?
Since you are a self-described expert on helicopters and especially Robinson Helicopters please answer the following as I have been wondering about it for several years.
When the Robinson is rigged the collective setting is made first placing the swashplate in a level position and the helicopter is also leveled and the extremes of swashplate collective movement are established. In this level position the cyclic stick is in the neutral position along the longitudinal axis with equal fore and aft travel. When the cyclic is moved from the neutral position until it contacts the forward fixed stop the blade is set to a specific pitch. When aft cyclic travel is established by moving the cyclic from the full forward position past the neutral mid position until it hits the aft stop the pitch is measured and the required pitch is greater than the pitch for forward cyclic. If the pitch must be adjusted it will change the pitch set for the forward cyclic condition. If the pitch has to be changed the mechanic is told to check if the forward pitch has been changed but he is not told what to do if there is a change in the setting.
Based on the above procedure I have a few questions:
1) If the cyclic is in the neutral position longitudinally and the swashplate level there is equal movement from that point to the forward and aft stop. If this is the case, how can the pitch setting for the forward and aft cyclic rigging be different?
2) If the setting for aft changes the setting for the forward position what does the mechanic have to do? If he readjusts the setting to accommodate the aft setting then the forward setting will again be different from the aft setting and have to be reset which causes the mechanic to play Ring-Around-The-Rosie with no specific instructions as to what to do.
3) Can you lease explain the 18-degree offset?
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4) How did the helicopter get certified with fixed control stops when the certification requirements state that there must be adjustable stops?