36-13 -> 15: Elevator Control Stops

The process of checking the elevator stops was a bit confusing, there are elevator deck stops, as well as control stick stops. At the beginning i didn't fully understand what the purpose of each was, but in essence it is simple: The aft decks stops are there to control the deflection of the elevator - after which, if you kept pulling on the stick you can over-stress the control system. The stick stops are there to prevent this overstress. 

As such - the elevator system must hit the aft deck stops, just before they hit the control stick stops.

To achieve this, the plans have you check the forward and aft deflections of the stick bases versus the seat angles. This is to make sure that you have enough range in the stick stops, to achieve the required actual elevator deflection. You also make sure that both sides hit the stick stops at the same time - i only needed to file the lower left side a little bit to ensure they hit at the same time. 

Next up, to check the deflections of the elevators, i needed to install the horizontal stab and elevators. This meant a large re-organisation of the shed - i was luckily able to fit the installed HS between the spray booth and the opposite wall of the shed with about 2cm on each side. 

Haven't seen these in a while!

Once i had the HS out, we tried to lift it into position, only to discover i had mis-measured where the hole for the elevator trim wires exited the aft deck - so i had to de-pin the connector and remove this wire. A new hole was drilled in a more appropriate location. 

The tape represents exactly where the middle spar of the HS is located - doh!

A new hole.

Just fits! 

I then spent around 4 hours gently filing away the aft deck in order to get the required elevator travel. The forward travel was pretty close - this didn't need a lot of filing. But the up elevator (the aft end of the aft deck) needed a lot of filing. 

Wanting to achieve the maximum travel, i was aiming for 30 degrees up, and 25 degrees down.

This was how the elevator horns initially contact the aft deck angle

And the forward deck angles.

The level was zero'd with the elevator counterbalance arms in trail.

25 degrees nose up was not enough.

but 25 degrees of nose down was within spec

I filed at the same angle the arms would hit the aft deck to increase the contact surface area.

After filing away i achieved almost 30 degrees. I could not go any further without the arms contacting a rivet on the aft vertical bulkhead.

It was a fair bit of filing! 

A good solid contact area

An error - don't do this! 

At this point, i forged ahead and checked that the control stick stops were not in contact at the time when the elevator horns were contacting the aft deck. This was an error - what i realise now, is that in order to check the control stick stops, you must have the aft elevator pushrod adjusted to the correct length (using the bell-crank jig). I ended up not filing off very much anyway - mostly just the primer. So i was lucky in this regard. But for anyone following; do not check the stick stops until the aft elevator pushrod is installed and adjusted to the correct length. 

Here i have used some paper strips and a needle file to make sure the control stick stops were contacting after the elevator aft deck stops - but should have waited until the aft elevator pushrod was installed. 

The saga of the aft elevator pushrod

The 2 forward elevator pushrods are adjusted to an accurate length during construction, and are therefore of a fixed length in the control system. The plans give you a paper template to set the angle of the elevator bellcrank, which effectively puts the sticks at the neutral pitch angle. However, this does not guarantee that the elevators are in trail. So the idea is that you adjust the length of the AFT pushrod, while the sticks are in this neutral position (using the template), such that the adjustment leaves the elevators in trail. This ultimately means with the stick neutral, the elevators are in trail. 

Sounds simple! 

What ended up happening was that i stuck the paper template to a piece of Masonite, and cable tied it into position. I used to clamps to hold the bellcrank in the neutral position (or so i thought!). 

 I then clamped the elevators into trail position and compared where the end of the pushrod was in relation to the holes in the elevator arms. I measured this distance, then removed the aft pushrod and increased the length of the pushrod by the measured length. This was a very big increase in length and saw both of the rod ends at the very end of their possible adjustment (the plans call for having at least 1/2 of the threads engaged). Something seemed off here, but i persisted. 

It was a long way off!

I used a bit of card with tape on it to measure the distance.

I then setup the pushrod on the bench, and increased the length by 1/2". 

The rod ends were marked to ensure 1/2 thread engagement

I then reinstalled the pushrod, expecting it all to be perfect, but the controls were hitting the aft deck stops WAY before they were hitting the control stick stops. Something was not right! So i clamped the elevators in trail once again, then realised that the clamps holding the bellcrank in position had moved. I had adjusted the aft pushrod with the bellcrank NOT in the correct position. Doh! 

My clever / fancy plan to adjust the pushrod on the bench was a failure! 

So in the end, i removed the pushrod and re-set it back to the plans length. I left the jam nuts loose so i could adjust the rod ends in-situ and climbed into the aircraft. I was able to adjust the forward rod end by just winding it in/out, and the aft rod end by rotating the whole pushrod. Once at the right length, i then removed it, and did the fine adjustment to make sure the rod ends were planar / tightened the jam nuts. 

A lesson learned - try and do something fancy is not always the best way. Simple is king. I got there in the end though! 

Since i was in the baggage area, i was able to hold the bellcrank template in position. 

All correctly adjusted. 

Once this had been done properly, i then re-checked the control stick stops and they needed a very small bit of filing to make sure that paper was able to slip between the stop at full elevator deflection in each direction. 

Job done! (finally). 

Here is a little summary:

36-11: Slop in the right hand stick

When the control stick sticks were installed, i noted that the right hand stick had some wobble in it. If i held the left hand stick against the stop, the right hand stick had a fair bit of play. You can see it in the video below:

Unsure if this was normal, I asked the question on VAF while at the same time sent an email to support to see if this was an issue. The forum members suggested using a beer can or some shim stock. I tried a soda can and aluminium tape etc but was not happy with how it turned out. One layer of aluminium tape was too thin, and two was too thick. The soda can was way too thin. I was investigating shim stock, however at the same time support decided to send me a new control stick base. 

Once the base had been received, I drilled the holes in the base to #19 then #12 all the way through, as well as doing the other preparatory steps such as drilling the lower bolt holes to #12, and filing the powdercoat smooth. I then checked that the stick fitted (which it did) and installed the new base into the aircraft. 

Thankfully with both right hand bolts installed the slop is almost totally gone. I think for final installation, one layer of aluminium tape should be sufficient to remove all of the slop. I also re-checked that the sticks were parallel. 

The new control base installed, with the stick temporarily installed.

36-02 -> 14: Flight Control Push Rods / Elevator Bellcrank / Control Stick Bases / Drilling Control Sticks

Elevator Pushrods & Control Stick Pushrod

To make up the pushrods, i deburred all the parts then used some 3D printed pushrod drill guides, which my dad printed on his resin printer, to match drill the rivet holes. Each pushrod was primed, then riveted together. 

The 3D printed guides are great and were downloaded for free from Mountain Ride Aviation! 

I double checked the idler bars cleared the flanges - this was done when the flanges were first prepped for installation, but i double checked again.

The stick link pushrod was cleaned and scuffed. 

These are the Mountain Ride Aviation drill jigs

These are such a simple and great idea.

I marked the shoulder of the end caps to make sure the end cap was in evenly, before drilling the first hole. I then drilled the hole opposite making sure the marks were even with the end of the pushrod tube.

Too large for the booth.

The end caps were riveted on using pull rivets, then they were hung in the paint booth and painted satin white to match the remainder of the elevator control powdercoated parts. 

Once the pushrods were dry, i used some wooden blocks with bolt holes drilled in them and screwed to the bench to set the correct pushrod lengths as per the plans. 

The nail was there to hold the end of the tape measure at the location of the centreline of the bolt.

I could then accurately measure where the other block needed to go, and screw it in place.

I was then able to adjust the rod ends evenly to achieve the correct length and also the correct rod end orientation.

Once at the correct length, the jam nuts were tightened and torque sealed.

To tighten the jam nuts on the larger tubes, i used some vice grips and some padding to hold them in place...

... and a carefully placed washer to make sure the whole pushrod remained co-planar during the tightening of the second rod end. It's easy to accidentally rotate the assembly when tightening the jam nut on the opposite end - then the rod ends are not parallel to each other. 

Both ends are co-planar.

The plans length was cross-checked, then torque seal applied to the jam nut.

The 3 tubular elevator pushrod tubes, along with the hexagonal solid stick pushrod.

Elevator Bellcrank & Mount

The elevator bellcrank parts were prepped, deburred and primed, riveted together then painted satin white along with the idler arms. The idler arms were installed. The elevator bellcrank mount was prepped and primed and nutplates installed. 

Painted satin white to match the rest of the powdercoated controls system parts

Nutplates installed

Control Stick Bases / Drilling the Control Sticks

The control stick bases needed to be installed before installing any of the pushrods, but before than can happen i needed to match drill the sticks to the bases. The sticks i am using are the Tosten CS8 pre-wired sticks, so this was done with the grips installed, as i didn't want to have to fish the wires back down the sticks. However, as it turns out, i didn't like how the wires were just exiting a bare edged hole in the steel, so removed the grips anyway at a later time. If i were doing this again, i would have just removed the grips for drilling. For anyone following, the aluminium inserts are match drilled to each stick, so make sure you don't swap them around - the grub screw won't fit. 

To do the drilling, the grips are clamped to a flat surface, then you are supposed to make the Molex mounting tab parallel to the bench. In my case, this tab was not perfectly aligned with the axis of the bolt - so i aligned the bolt with the work surface instead for the drilling. I used waaaaaay too much super glue and ended up having a hell of a time getting the bases separated from the sticks. 

This was the setup - the stick was clamped to the bench using an over-centre clamp i had in the shed.

I used the long mounting bolt to align the stick bases, then superglued them in place.

Aligned nicely

The sticks were then drilled progressively using a #19, then reamed to 3/16" (instead of using a #12). 

I had to clamp the sticks and use a big punch and twist the bases off - too much superglue!

This was the bare hole for the wires to exit from...

... so i added a grommet into the hole instead.

Control Stick Bases / Stick Pushrod Installation

The control stick bases were installed first. The stick pushrod was installed between the bottom of the sticks, with a nut installed on only one end (as this needs to be adjusted). Of course, i had to get some glory shots of the sticks in place!

The large steel capture washers for the outsides of the bearings were scuffed and cleaned up, then soaked in T-9 to help prevent them rusting.

As always some PTFE on the bolts to help prevent corrosion.

The washer wrenches were not exactly the right size for the weirdly sized 5702-75-60 washers, but a cable tie allowed me to hold them for insertion

I used a piece of camcord to hold the sticks in a vertical position for measuring, then adjusted the stick pushrod so the sticks were parallel, then installed the final hardware on the remaining side. 

Since the fuselage was tiled over for access, a piece of camcord held the sticks in a vertical position for measuring.

Initial measurement at the stick base was 527mm...

... and 531mm at the stick top. So the stick pushrod needed to be lengthened.

Final measurement was 523mm at the stick base..

... and 525 at the stick top. This was as close as i could get it. 

Elevator Pushrod Installation

The idler arms were installed with the final hardware, and the elevator pushrods could then be installed in order.

The forward most pushrod gets installed from the tailcone, then snaked through all the holes into position

It was a tight fit into the powdercoated arm - the ball kept rotating as i tried to push it in.

The solution was to use a long bolt in the eyelet ball, which meant i could push it in straight - until the shoulders just grabbed. Then the bolt could be removed and the eyelet slid in fine. 

I used a mirror to align the rod end ball.

Tapping the bolts in was super fun!

Likewise, doing up the nut meant being very creating with tools to get onto the nut. 

I could not imagine how much harder this would have all been without a rotisserie!

Next up i attached the centre pushrod to the bellcrank, then installed the bellcrank to the bellcrank ribs. I also installed the autopilot pitch servo bracket at this time. Since the bolts were being installed into nutplates, i measured the running torque to ensure the correct torque value was used. 

The nutplates actually had quite a low running torque

The 2 middle pushrods had their hardware installed at the idler arms. 

The last step was to install the aft (the longest) pushrod. I installed this onto the bellcrank, then torqued the bolt (and applied torque seal). This was in error - i should have just left this with a loose bolt - as this pushrod needed to be adjusted later. More on that in a future post! 

Fwd pushrod connection to the stick assembly.

A look between the 2 spars.

Idler arms where the forward and middle pushrods meet

Aft pushrod and bellcrank.

Of course, i had to pop the sticks in and pretend i was flying!