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A while back, there was a lot of discussion
about
> how much space should be left between the control horn and
the horizontal
> stab. The consensus was that you had to leave
space to avoid ice building
> up there, and jamming the
controls. What spacing do you have, and were you
> aware of
any control restriction during your incident? It sounds as
though
> your situation was about as bad as it gets without
disaster, so it would be
> interesting to know if there were any
control effects.
>
> Jerry
Hello Jerry,
> You did not mention whether there was
any evidence of ice around the
> elevator control
horns.
Actually, in reply to Scott's
questions yesterday, I did address this subject. I have included a copy of my
reply below. I have very tight clearance between the elevator counter weights
and the h stab, less than 1/8 inch. I noticed no icing on the
counterweights and no control "freezing". In my situation, if the "solution" to
elevator freezing was to allow sufficient clearance for ice, I would have needed
more than 1 1/2 inches since this is the amount of ice that accumulated on
pretty much all exposed forward facing surfaces. Setting the h stab
angle of incidence correctly so that the counter weights remain "fared"
behind the h stab and so that the h stab and elevator are not fighting each
other is, I believe, much more critical than allowing space for
ice.
- Could you report on the tail plane
icing? I read the story of the
prolonged climb with the ice locking control surfaces on the IV – Ice buildup
on the under surfaces, too? I
have been concerned about the tail because of the sharp leading edges and the
potential for building ice first.
The horned
pattern ("horns" above and below the LE with a forward facing concave shape
between them) was the same on the h stab as the wing. I was aware of the
possibility of freezing the controls and kept moving them rapidly every 30
seconds or so. At no time did any of the controls freeze. My elevator
counter weight is "faired" behind the h stab pretty well and, as far
as I could tell accumulated no ice. One feature of the LNC2 that probably helped
is the fact that there is not very much tail down force required to maintain
level flight. This is one of the things that makes our planes so sensitive in
pitch. In an icing situation, it probably helped prevent a tail plane
stall. BTW I have the small tail.
Bill
Harrelson
5zq@cox.net
N5ZQ
320 950+ hrs
N6ZQ IV
1%
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