I received the updated nose gear door plunger system from Lancair in early April. Lancair was hesitant to send me the system because they knew there were some minor problems with the system and not all the parts had been acquired. Upon my insistence, Lancair sent me the parts they had without any installation instructions, all of which was fine with me. I figured that if I could build a plane I could modify the nose gear door closing system to work just fine. The following are the changes I made to that system to make it work.
1. The upper linkage provided was 3/8" too long, which caused the linkage to contact the nose gear strut before the strut hit the gear up stop. Shortening the linkage provides 2 benefits; first, the nose gear strut properly hits the gear up stop, and second, the travel of the plunger is reduced such that the doors rotate the needed 90 degrees to full open instead of much greater than 90 degrees due to the longer plunger travel. When the doors open past 90 degrees the actuating rods are rotated outward and over extend the ball joint end.
2. The bolt provide by Lancair holding the upper and lower linkage is a AN3-44A, however this bolt is one size too short. An AN3-45A is needed. Lancair did not have this size bolt so I ordered it from Aircraft Spruce.
3. The brackets (Legacy P/N 4761) on the gear doors need to be located directly under the plunger linkage and a distance from the door hinge centerline, which will allow the nose wheel to pass by the doors without any contact. I found that the proper position is with the linkage attachment point directly over the edge of the hat section that stiffens the door. Installation of the brackets was accomplished by drilling out the AN426AD3-5 rivet attaching the hat section to the door and replacing it with a MS26495-S52 screw with a _" thick phenolic spacer between the hat section and the bracket. The second mounting screw passes through the center of the hat section and I slid another phenolic spacer inside the hat section to prevent deformation of the door when the screw was tightened. I used the MS21042-3 all metal stop nuts on the end of the screws.
4. You need to fabricate the proper length pushrods to attach the plunger to the gear doors. This can be easily done using a 2" piece of stainless steel 10-32 all-thread. The pushrod was assembled using a BJ-04 ball joint to connect to the door bracket and a HFC-3 rod end to attach to the plunger linkage. The ball joint and rod end were installed using AN315-3 check nuts.
The plunger needs to be located with the doors closed because the plunger is also the up stop on the nose gear. The 2 lower mounting bolts go through the phenolic reinforcing block on the tunnel close-out, but the two upper bolts go through the core laminate. De-coring the area around the upper bolts and filling the area with epoxy-flox is required.
Jim Thomas #166