Position of a screw bolt for aircraft flaps


Newbie here, and I want to use the Arduino to display the position of a 3" bolt that when turned changes the position of the flaps on my airplane. Currently I just look out the window and try to remember how many times I’ve turned the handle to know the approximate location of the flaps. I would like to connect it to a small display that would should flap position from up to down in percentage or even just the number of cranks from a set point would work too. I’ve attached a picture of the mechanism for reference. The brass nut on the bolt goes up and down which pushes the rod back or pulls it forward depending on which way you turn. I’m wondering that mechanism I could use to determine the bolt position? And any suggestions or help would be much appreciated!

thanks in advance!


An encoder or ten-turn potentiometer turned by the bolt?

A photo of the mechanical arrangement would be useful.

Would having such a device working incorrectly compromise safety? If so then this is not a suitable project - Arduino's are not rated for safety critical systems.

I just updated the post with a picture.

The turn handle can be cranked about 8 turns up and 12 turns down from neutral position (flaps level with wing). So a total of about 20 turns is possible.

Not room for an encoder, and 20 turns rules out 10-turn pots... The other end of the axle might be better? Or have some angle-measurement on the coupling plate (ordinary pot would be enough) Possibly via another linkage arm.

Forgot to add that it won't compromise safety. If anything it would make things safer as it would add another means of verifying flap position.

The other linkage at the back is a slider that moves forward and aft about 3". An angle measurement wouldn't work either as the plane is usually changing angle of attack as the flaps are adjusted. Really need some sort of slider potentiometer(?) that could show the current location of the brass nut? Or the number of turns the bolt has mad from a known position...

this is a tough one...

I meant angle relative to the frame, not an IMU.

A VERY simple arrangement may be to mount two hall sensors between the handle and the mounting frame and attac a magnet to the handle. A simple counter sketch on the Arduino should tell you how many times the handle has been turned and because you use two sensors, it can tell which direction the handle has been turned. I've not physically tried anything like this so its only a suggestion.


I'd use the slider pot method, as you mentioned robarchibald, attached via a short linkage to the triangular plate, and detect it's position rather than that of the screw thread. With careful selection of the attachment point, you should be able to avoid pushing the slider pot beyond it's range. You could leave a safety margin at each end, and use most of the slider's travel. That would give you a nice analogue voltage reading of position that you could map to whatever range you want and print on a 16char x 1 line LCD display. ie 0 to 10, 0 to 100, -10 to +10 etc.

I would suggest that a non contact method is required as if you are sitting in said aircraft caa or faa approval will be needed for the modification.

Can you post a pic of the mechanical arrangement ?

I mean a bigger picture.

There was a similar thread recently. Sticking a barcode on the angle plate and using an optical sensor could work.

Its still a mod though which will need to be approved.

Can you post a link to the aircraft involved ?

Boardburner2: Sticking a barcode on the angle plate and using an optical sensor could work.

Good idea.


I'm for the pot. Something like that:

rotary sensor

coupled to the lower left bolt, and fixed to the triangle. This rotary encoder sound great. I saw some pot like this encoder with a nice hole that could fit on the bolt.