H-Stab Electric Actuator Adjustment

Been trying to set my Series 5 (newer style actuator) stabilizer actuator travel (first time) and not having any luck using the directions in Chapter X, "Rigging of Flight Controls", page 40-41, steps 33-34. Also, I have read and attempted the different threads on this forum concerning same, which are basically, the steps in the manual.

The longest actuator length, fully extended (aircraft nose down), with the rod end and jamb nut screwed completely into the actuator; the horizontal stab tube and the fuselage tube hit (binding the actuator). If I take the jamb nut off and screw the rod end all the way into the actuator, then there is about 1/4" of clearance between the tubes. This has been the only way that I have been able to have any clearance without binding the actuator. There is no way I will be able to get the 7/16" clearance.

There is no way to adjust the stroke of the actuator, despite what the manual says. The manual states, "As the shaft is rotated, stroke of the actuator will be shortened if the rotation is clockwise". That does not work with the actuator I have. I have not be able to replicate this. Disconnecting the links and the rod end from the stab, rotating the actuator shaft "clockwise" until the correct distance between the tubes is correct, then reconnecting everything....once the actuator is run full travel down and back up, it is once again tube-to-tube contact.

I have tried numerous combinations of things. None work. The actuator shaft stroke is what it is, there is no way to shorten it. The only adjustment is the rod end. Which leaves me in a bind....

Went out again this morning and tried the procedures a couple more times. Just incase the 10 or so times I did it last night were different. No change. I removed the actuator and measured the stroke from the lower pivot to the top of the actuator (with rod end removed):

Extended: 19.250"
Retracted: 15.375"

Stroke travel is: 3.875"

Don't know the correct length.

You can't change the stroke range of the actuator-don't try. What you can change is the distance the actuator rod sticks out of the tube, but the stroke range will remain the same. Just disconnect the links to the rod and screw it into or out of the tube until you get what you want, then reconnect the links. Will probably take several tries. Trust us, it does work. You do have some fine adjustment available by screwing the spherical rod end in or out, but that is not the main method of adjustment. I suggest screwing the rod end in to some middle point and then lock the jam nut and leave it there.

This subject has popped up before as the instructions do not outline what you are doing beforehand.

The only adjustment to the actuator total length is via the ROD END. The actuator will always run full up and full down and the actuator shaft extended length is not adjustable.

Prior to doing adjustments, the horizontal stab is mounted in the fuselage with the actuator attached at both ends.

The manual instructs you screw the ROD END all the way into the actuator.

There are two ways to do this.

You can disconnect the rod end and scissors from the horizontal stab and risk dropping all the shims, washers, nut and bolt into a hard to reach location; and, have the horizontal stab fall on your head while you try to make adjustments. OR…

Disconnect only the scissor link keeping the rod end connected to the stab. The actuator will support the horizontal stab while you do the trial and error adjustments.

Next, loosen the rod end jam nut and rotate the actuator shaft counter-clockwise to screw the rod end all the way into the shaft. Turning the actuator shaft counter-clockwise will screw the rod end inward. Simple and you don’t drop parts.

Temporarily connect the scissor (use a rubber band) and apply power to run the actuator out full length. ( a small 9 volt battery will do this just fine) Now measure the clearance between the fuselage and the horizontal stab. The setting is 7/16 +/- 1/16. If your horizontal stab is hitting the fuselage you have the wrong rod end installed, the rod end in the wrong holes, (it goes in the forward holes) or the rod end is not screwed in all the way.

To make adjustments you disconnect the scissor and rotate the actuator shaft. Rotating the shaft changes the rod end extension but also screws the actuator in or out at the same time. Because the actuator length temporarily changes you must apply power again to extend the actuator to full length. It takes a few tries to get it right.

When the adjustment is correct, lock the rod end with the jam nut and permanently attach the scissor link.

Just for reference my actuator compressed length from hole to hole is 15.50 inches. and the extended length is 19.675 inches.

One final note: Screwing the actuator shaft in or out manually never changes the stroke or end points. Only the rod end extension changes the total length.

John Pitkin
Greenville, TX

You are correct John; I was remembering wrong.
I'm not sure why N14ND is having trouble with the actuator being too long even with the rod end all the way in. Must be something to do with the mounting of the bottom end of the actuator, or the H stab.

Thanks John, I have read your instructions in a previous thread. And followed it... doesn't work for this installation. Basically, impossible to get the actuator any shorter in length (p/n 61012.101). Don't know if the newer actuators are shorter. Yes, I have it installed correctly into the correct hole on the h-stab tab. Pretty hard to get the scissors to work correctly on the aft side of the actuator otherwise. There is only one location at the lower fuselage pivot. Yes, I have the correct rod end (supplied with actuator) installed with p/n 10001.116 bushing pressed in, AN316-4 (thin) check nut in installed. With the rod end and check nut screwed in all the way in as far as it will go into the actuator (bottomed out) actuator length from hole-to-hole is:

fully extended 20.00"
retracted (compressed) 16.00".

Sounds like a great time to call Kitfox for support.

Jeff

Low and Slow (N14ND),

I stuck my head in the tail cone and it appears there is enough room to re-drill the lower mounting tabs in the fuselage. You could move the bottom end of the actuator aft and down enough to get you the 1/2 inch or so that you need. It's tight and you'll need an extended length bit to reach but it might work for you. Even if you've already covered the fuselage it will only leave a 3/16 hole in the fabric. The bottom end is only bolted finger tight with a castle nut so it's doable without a wrench.

John

No covering on the fuselage yet. As for the fuselage mounting tabs, there's no room to re-drill a lower mounting hole the required distance. I would have to remove the existing tabs and reweld tabs moving them farther aft on the fuselage which would change the thrust angle of the actuator.

Niand,

I'm including a picture of my lower mounting tabs just for reference. What mine looks like does not help you other than comparison to confirm your actuator is too long. Not by much, however, as my actuator is only 3/8 inch shorter than yours at full extension. My tabs would allow relocation of about 1/2 inch.

The other variances I can think of would be the location of the mounting holes on the fuselage, mounting holes on the horizontal stab, style of rod end and actuator tolerance. None of which seem to fit your situation.

Maybe the good folks at Kitfox can help you out.

Let us know what the folks in Idaho say.

John