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"I find that the trailing edge of one elevator doesn't match the other
by about 1/8 to 1/4 inch. Should I worry about this? If so, any
suggestions about how to correct it?" Steve Colwell
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Hi Steve,
We noticed a similar problem with our elevator's alignment. I remember
you warned us of this when we talked in December. Our
elevator/horizontal stab alignment was challenging because the
horizontal's trailing edges (top & bottom skins) were too long, crooked,
portions of the elevator leading edges were imperfect, and the
hinges were slightly out of alignment. All these imperfections really
create confusion over what to do for a good fit. For example, if on one
side the elevator/horizontal gap is too small, is it because the skin is
too long, the elevator leading edge is too big, or the hinge(s) are
mounted incorrectly…?
The horizontal's trailing edge skin, when cut correctly, provides a good
reference for the up/down alignment of the hinges. So, we began our
correction by cutting the horizontal's trailing edge skin to a
consistent length. We used the elevator hinge line as the "truth
reference" for cutting the trailing edge -- we cut ours about a half
inch short of the hinge center line (can't remember exactly and not at
hangar to measure). We chose/guessed at this based on examination of
the gap before the cut. We then reattached the elevators and checked
the alignment based on the new gaps. By the way, we use 1/4" aluminum
rods that insert thru a hole in the end of the elevators to quickly
attach them to the stabilizer (an excellent suggestion from someone on
the LML).
Examination of the new gaps made it pretty clear where and which hinges
needed to be shifted (all of ours). One thing that made it easier to
see our problem was comparison of the cord line of the elevators and
horizontal (as viewed from the ends of the horiz/elev). Ours were not
aligned with the elevators in the neutral position. The hinges were
bore-sited okay, but "flying" with a bit of roll. The hinge movements
for proper alignment corrected most of the gaps. The remaining areas
where the gap was too big were caused by asymmetry in the leading edge
of the elevator and were built out with micro to correct.
To move the centerline of the hinges, we elongated the bolt holes (horiz
side) to allow them to be repositioned. We didn’t have to reposition
the weldment because ours is well centered on the elevator leading edge
arc (we did have to move the center hinge, though). We also did not
have to move the elevator side of the hinges for the same reason.
After we'd already started all these corrections, I called Mark
Mahnke/Lancair and he confirmed that this is/was a good approach and
that they're even thinking of modifying the hinges so that they come
with elongated attach bolt holes to allow any necessary alignment
changes. Apparently this is not an uncommon characteristic of the
Legacy kits. I'm not sure if it's a significant flight performance
issue. You may get a bit of a roll torque from the asymmetry. It may
help, though, if it counters the engine and slip stream torque effects.
Mark says one option is to just correct it with body work. We're happy
that we seem to have corrected the underlying problem, though.
Valin (& Allyson) Thorn, Legacy 73, Houston, TX
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