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CAUTION - WING ATTACH BOLTSFrom CP52, Page 5 (July, 1987)
We recently heard from a
Cozy builder who had been chasing a minor but annoying vibration in his aircraft for some
time. He finally traced it to the fact that his wing attach bolts were slightly loose
allowing his wings to move a little in flight. After he tightened the three 1/2"
bolts in each wing (the Cozy uses the Long-EZ wing and wing attach system) the vibration
went away. He checked several Long-EZs in his area and found a couple of them with
the same problem. We had not had anything like this reported to us before and we checked
the two Long-EZs we have here at RAF, both were solid.
The way to check for this problem is to have someone put their
hands on the joint between the centersection spar and the wing to feel for excess movement
while you lift at the wing tip. A small amount of movement, less than 1/16" at the
wing root leading edge, is normal. If excessive movement is detected, you must remove the
wing bolt covers and torque the bolts. It is difficult to use a torque wrench in this
area. We simply used two ratchet wrenches, each 6" long, and pulled about as hard as
we could. It takes two people to do it right.
Since a person can pull with about 75lbs of force with one hand,
we can calculate the torque - 75x5=375in/lbs or 31ft/lbs. Using this method, we have never
had one of these bolts work loose. A 1/2-20 aircraft bolt can handle 600in/lbs (50ft/lbs)
of torque. However, with the glass plies in between the aluminum hard points, we would
recommend no more than 400in/lbs (33ft/lbs) of torque on these bolts.