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Elevator / horizontal stabiliser balancing

This is necessary after fitting the TKS leading edge panels. Basically one has to remove some metal from the lead block in the balancing weight.

What I find curious is that the Socata instructions show it done without the trim tab operating rod, or any other partial mass of the operating linkages. In the diagram below, I show the trim tab operating rod with the coloured line. About half the mass of the rod is a part of the elevator out-of-balance mass so IMHO it should be taken into account

The bit which sticks out on the left is the lead weight and this shows how much weight has to be removed – about 1kg

I thought elevator (and all other control surface) balancing was really critical to avoid flutter and resulting disintegration, but here they are disregarding some (admittedly small) masses which clearly form a part of the control surface.

I wonder if @pilot_dar is still around here these days…

Shoreham EGKA, United Kingdom

They could also have considered all of the other masses when setting the spec, but then reduced it to a “simpler” number to make it easier for the mechanics. This seems likely as the test procedure seems to involve removing the elevator from the aircraft and measuring it on a jig of some sort.

United States

I think they need elevator removal, onto a jig which pivots it about its normal mounting bolt holes, because

  • you cannot access the balance weight otherwise, because it is about 1m inside the rear hull section
  • the bolt friction (they use a particular type of bearing which allows some misalignment) would make balancing less accurate

The balance weight reduction is shown as exactly 1kg which is dead curious how they achieved that Especially with the TKS add-on weight being dependent on how much sealant is used to attach the panels – anywhere from nearly zero (they are riveted after all) to “loads”.

Shoreham EGKA, United Kingdom

Shoreham EGKA, United Kingdom

While doing this, I noticed something interesting, which had been there for 15 years, courtesy of Socata

Shoreham EGKA, United Kingdom

The “smooth part of the bolt” is called the grip or the shank.

Andreas IOM
6 Posts
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