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Elevator Down Stop

claycookiemonster

claycookiemonster

Well Known Member
Checking elevator travel today. Up travel is nicely within the tolerances of plus 25-30 degrees at plus 27 degrees, and both elevator horns are in contact with the stops at that point. The challenge is the down travel.

One elevator horn contacts the stop at 22 degrees down (range is 20 to 25) however the other horn is about 1/16" from contacting the stop at that point. My concern is if we file the stop away to allow the horn that is NOT contacting, we may exceed the 25 degree limit.

The F811D-1 elevator down stop has already been riveted in place. Another option would be to drill it out and replace it with another stop which will contact both horns but not exceed the travel limit.
 
Align the elevators and drill the hole for the elevator push tube. One done, the elevators are joined. At that point you can figure out if you need to file or grind down the elevator stop (I suspect you will be pretty close as is).

But, measure six times, file once.

Carl
 
I've just installed those components and my observation is that whichever horn contacts the stop (if the horns are not level with each other) will set the overall travel, since the horns are bolted and held together via the end of the pushrod.
It's puzzling that your elevator horns are level on one edge but not the other, unless they are perhaps different sizes? Or maybe the stop was installed out of square? In any case I think you only need to worry about filing down the stop a little bit at a time until you get the desired travel, but it sounds like you already have 22 degrees so technically there is no need to do anything, since it is within limits. The outer limits are design limits not target limits.
 
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Both elevators are held neutral by the counterbalances. The horns are ever so slightly off-set, which the plans anticipate. Given this, one horn will hit the stop before the other. The directions clearly say that the stops can be filed or ground so that both horns contact the stop at the same time. That makes sense.

My question is, by filing the stop down where the first horn hits so that it can move a bit further to allow the other horn to hit the stop, the elevators will travel just a bit further than they currently do.

Given that the down travel is already 22 degrees out of a maximum of 25 degrees, I'm concerned that allowing a bit more travel may allow the elevators to exceed the maximum travel.

Or I can ignore that the horns to not contact the stop at the same time, and allow one horn to be about 1/16" short of the stop when the other hits.

Or, behind Door #3, I can reinstall the elevator stop part to try and address this.
 
Options

Of the available choices I think "Door #3" would be least preferred since it would involve drilling out rivets through 1/4" of combined plate and then reaching beneath the rear deck to buck and install the replacement.
I think I would leave it as-is. But one way of predicting the additional travel that would result from filing off one side is to insert a temporary 1/16 shim to see what influence it has on the travel.
I expect that normally the horns shouldn't ever bang hard againet the stops, unless the plane has been left out in the wind without any control locks fitted. :(
 
I'm not flying yet, but for what it's worth, I've got about the same gap as you and I believe that one stop hitting before the other isn't a big enough deal to get the file out. I left plenty of meat on the stops and went for the lower limit of travel, so that if it starts to get a divot on the one that hits first I can smooth it out at that point and sort of let it find it's own happy place.

I'll admit it makes me a little uncomfortable to have that steel horn banging into an aluminum angle, so I've got in the back of my mind that eventually I might cushion that area with a piece of caterpillar grommet or something if it looks like it's getting beat up too much. But considering how beefy everything is back there, I think that would likely be years (decades?) from now.
 
I have plenty of margin with the elevator down. But to the get minimum 25deg in the up position, I had to grind the elevator stop.
 
Just to complete the lap here, I'll just post the advice I got from the Mother Ship today: "You can file away the stop in an attempt to get both horns to hit at the same time, but check the travel as you do this, and STOP filing when you reach the limit, even if they are not hitting together."

So, the travel limits are real LIMITS, while the goal of having the horns hitting together is nice, but secondary if you have to choose.

Makes sense to me.
 
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