What have I gotten myself into!: Ch 22 - Electrical/Avionics

Pitch servo installation

With spring warmth at hand, I decided to get cracking on the pitch servo installation.

I had a pretty good idea of where the servo should go. I wanted the heavy steel mass as far forward as possible to help with the center of gravity (CG), but I knew this location would require dismantling some of my previous work, and perhaps relocating and rewiring the entire ground bus.

Aside from getting installed in a forward location, the pitch servo would also need to connect to the elevator pushrod. The place I had in mind was right in front of the engine instruments, on the right fuselage sidewall, where a bracket already existed from the vacuum filter days, though it was currently being used by the ARINC module.

Bracket supporting the vacuum filter (before "steam gages" replacement)

Vacuum bracket liberated during EFIS installation

ARINC module looking for a home

Vacuum bracket repurposed as ARINC support

The area behind the engine instruments is pretty spacious, but more importantly it is right over the top of the elevator control tube.

Looks like the ARINC module might need to find itself a new home

I spent quite some time figuring out how to make this location actually work, but eventually I ran into an unforeseen problem.

While busy congratulating myself on how smart I had been reusing the existing bracket once again, I noticed that my compass was indicating 60º off its normal reading. Initially confused by it, I tried moving the servo slightly, and the compass just went nuts!

That’s when it donned on me that the big hunk of steel was rendering the compass useless. I really should have known.

Double “DOH!”

Oh... it looks so obvious now!

So, I tried moving the servo all over the cockpit while observing the compass. Sadly, any place within two feet of the compass adversely affected the compass readings. There was a slight possibility of installing it way up front in the nose, forward of the canard, but the connection to the elevator rod would have been at a terrible angle, and I would have had to really tear this plane apart to do it. Some things are just better done while building the plane rather than afterward.

Never fear though, I had a plan B up my sleeve, although it wasn’t as good as plan A for moving the CG forward...

Because the LongEZ has a rear control stick, I might still be able to connect to the elevator control tube there, perhaps without inconveniencing the passenger too much. The plan was still to place the servo as far forward as possible, which now meant against the front seat, then connect it somehow to the tube in question.

Often a one-man building team, I leveraged velcro power to help me find a new place for the servo, and hold things together while I pondered on the new setup.

Investigating an alternative pitch servo location

After talking it over with my friend Wade, plan B started making a lot of sense, and as a bonus I wouldn’t even need to machine a new connector if I attached the servo rod directly to the rear stick. All I needed was a longer bolt and a few washers.

That just looks made for it

Please forgive the huffing and puffing on the next video, as I was laying with my chest on the left longeron, feet on a step stool, trying to get a good shot for you.