|
|
Yesterday during preflight inspection, I noted some binding in the
aileron when near the left stop. The planned formation flight was
aborted with no regrets.
A trick I learned from Robin Reid was to keep the control in the bound
position while disassembling to isolate the bind.
I shoved a towel into the aileron-tip gap to hold the aileron still, trapping
the bind, while disassembling the system. Removing the bolt at the base of
the stick, I found the bind was in the left side. Progressively splitting the
system, the bind was isolated at the left aileron. On removing the aileron,
the problem was found. (Photo 348)
The aileron counterweights were installed inside a thin-wall steel tube
bonded and wrapped to the curved extension of the lower skin. After 1000+
hours, the lead rod has loosened and slid out the open end of the tube
where it can foul against the pushrod.
320/360 builders with sharp eyes will note that the pushrod attachment
is single-shear on the 235, where it is double-shear on the later model.
Most builders would have mounted the lead weigh to the web and wrapped
with 2 BID as described in the manual. This method appears to be less
awkward to assemble and adds rigidity to the counterweight portion.
For a permanent repair, I removed the weights, sanded the inside of the
tube, and reinstalled the cleaned weights with a structural adhesive.
A chicken-rivet was also added to prevent the rods from moving. (Photo 355)
The same modification was made on the right side as well.
This may be a completely unique problem to one particular aileron on one
airframe. Or it could be a potential problem for others to look for at
your next
inspection.
Lessons learned or reinforced:
+ Do a good preflight inspection
+ If something doesn't feel right - it isn't right
+ Especially in primary controls, any problems should be investigated
all the way to the source while on the ground.
+ Intermittent problems are easier to find when they can be trapped in
the defect state.
+ Look for the unintended consequences of any design change
-bob
|
|