While installing the flap drive I noted that the flaps would occasionally lock
up before arriving at the full down position. This never happened during bench
testing and only occasionally after the outrigger wheels were temporarily put
in place while establishing the flap travel. The cause was the threads on
the bolt connecting OR4 and OR5 sometimes contacting W21.
My wings were built according to issue 2 Rev 1, the thin blue book. The
drawings in this book show the bolt oriented with the head on the OR4 side.
However, the manual updates for the 4 ring binder, issue 5 show this bolt with
the head on the OR5 side. Reversing the bolt per this later drawing solved
the problem, although scratches in W21 remain from contact with the bolt's
threads.
It seems to me that reversing the orientation of a bolt without calling
attention to the change in a note is a fairly subtle way of introducing a
change, particularly one which could prevent an awkward situation in flight.
I know I missed it and it leaves me a bit unsettled wondering what other
subtle changes I may have missed....
Or is there a set of notes which I missed?
After observing the random way that the above lockup occurred I started
looking carefully at the overall way the outrigger operates. I noted that the
connection between OR4 and OR1 is much looser than most connections in the
Europa. There is about 45 mils of side play possible as OR4 slides along the
bolt connecting it to OR1. In addition, the hole in OR4 is about 8 mils larger
than the bolt, which helps to make this a fairly loose joint. The result of
this is that the aft end of OR4 can travel sideways a fair distance, leading
to a question about the width of the slot in the fiberglass for OR4 which
allows the outrigger to operate.
I made this slot in the fibergalss about 4/10 inch wide and OR4 always seemed
to hit the middle of it during bench checking. Due to the loose jointedness
of OR4, it can easily be pushed off center so that it contacts the glass
either side of the slot, preventing operation of the outrigger and flaps. To
ensure clearance in the extreme positions this slot would have to be widened
to about an inch, a considerable change from its present size. The manual
doesn't provide guidance on the needed slot width (don't see any mention at
all of the slot in my manual or updates), but given the randomness I observed
in the hangup due to bolt orientation, I'm leaning in the direction of the one
inch slot. An alternative, of course, would be to add washers to the 0R4/OR1
joint to reduce sideplay, but I am loath to make a change to the design which
might compromise operation.
So, what have others found as an operable width for this slot?
Regards, John A044
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