Electric Flap Travel Adjustment

[777drvr]

Hi Guys,

I've used a bunch of search terms and can't seem to find the answer to this one . I recently did a control deflection check on my recently purchased RV-4 and found that my electric flaps only extend to 25 deg. .

How do I increase the travel to the specified 40 deg. ?

Marc

[Steve Sampson]

Marc, gaining the full travel from the mechanism requires everything to be adjusted just right. It is almost CERTAINLY not a function of the motor assembly, but the geometry of the mechanism upon which the motor acts.

This picture shows most of the mechanism. If the geometry is wrongly set you will easily loose the total travel.

What I would check is that:

1) the length of the lever against which the motor pushes is correct.
2) That the distance from the pivot point to the attachment of the screwed rod is correct.(You have the crucial dwg that defines this? If not perhaps I can find, photo and send. If the builder made it wrong it should not be too hard to make up a new lever arm.)
3) That the angle of the lever at full retract and full deploy is equal. If it is not you will loose travel.

Once you have those set correctly you need to make sure that at the limit of the retraction the flaps are indeed fully up, but no more, by adjusting the pushrods that come through the wall of the fuse. Once that is all correct I think you should find you have the full travel that VANS requires, or even a couple of degrees extra. I suspect the extra degrees are lost under air load.

I spent a long time on this because stopping is very important to me because of the length of my strip.

If that is less than clear, just ask.

[Steve Sampson]

I missed out a bit. The screwed rod also needs to be adjusted in the same way as the lever previously described, to ensure the movement is maximised.

[777drvr]

Hi Steve,

Unfortunately , I don't have drawings . I'm going out to the hangar to do more trouble shooting . I guess the throw of the actuator is fixed and the total movement is determined by a ratio at the lever ?

Marc

[Steve Sampson]

Yes, thats correct. I will take a picture for you but its lashing down with rain and dark here, so I wont go looking for the drawing in my hangar until tomorrow. I will take a picture.

[Steve Sampson]

Marc, in fact I found the instructions in a folder beside my desk so look here. I think it is telling to see the note that is highlighted. I seem to remember that I had to make the arm a second time possibly to get the last little bit of movement, though a very slight increase of the distance results in a big change. Good luck!

PS Double click the pictures to get larger images.

[777drvr]

That's very helpful Steve ! I had a look at the plane and found :
- the actuator stroke is 5"
- when disconnected from the drive the flaps are capable of 40 deg
- 1/2" more stroke is required at the flap horn to get 40 deg
- my pushrod mount on the ratio bar is only 1 7/8" but there is another hole farther out that isn't used .

Here's a picture . If the angle isn't too great , I think using the other hole would do the job.




Marc

[Steve Sampson]

It sounds as though you are progressing. You might want to try it in the outer hole, or it looks as though you have enough room to drill a second hole between the two. As you move further out the load on the motor increases, but thats the only(but important ) downside.

Good luck.