As I approached the end of the build manual I was expecting the last part to contain instructions for loading the software into the Skyview HDX, adding the fluids, and doing the first engine start. None of this was there. There were no directions for finding additional documents that would walk me through this stuff. Turns the documentation is there and I had to find out about it by reading other blogs and digging around on the RV-12 forums on vansairforce.net. The first thing I should have gone to is called the Production Acceptance Procedure (always referred to as the PAP) which only exists because the RV-12 can also be had as a factory-built S-LSA airplane. Other experimentals, E-LSA or EAB, don't have this document. Early in the PAP another document is referenced, a read-me file on the downloads page at vansaircraft.com.
This read-me file contains all of the steps required to download the Skyview software, settings files, databases, sensor definitions and current TFRs. It explains how to tell the software what equipment is installed and how to calibrate this equipment, including how to calibrate the stabilator position for takeoff, how to calibrate the fuel system, ADAHRS, AOA, autopilot servos and other stuff. In other words, this is an absolutely vital document. I went as far as I could in this, then came to some stuff that required the engine to be running. Somewhere in here I discovered the PAP and everything started to become clear.
The reward for completing the steps in the read-me file was that I got to see the Skyview HDX all lit up in all its glory. This was pretty exciting for me and I spent quite a bit of time staring at it. On the right in the picture is my iPad running Foreflight propped up on the map box door. I'm planning to mount it approximately in this position but standing off the instrument panel a bit and tilted toward me in the left seat.
At this point, with some fear and trepidation, I tried the landing light, navigation lights and strobe lights. They all worked! After patting myself on the back for doing such a great wiring job (prematurely, it soon became evident) I proceeded to test the Garmin GTR-200b radio. This involved plugging a headset into the jacks on the pilot and co-pilot sides, which resulted in a loud squeal in both and an even louder string of swear words from me. A wiring problem!
I'm convinced that 95% of all wiring problems involve a faulty ground, but where? Since managing electrons is not something I'm good at, I enlisted the help of my EAA Technical Councilor, Dan Berry, to help track it down. Like me, Dan is a mechanical engineer, but unlike me, Dan is a wizard with electrical things. After studying some electrical diagrams that he pulled up on his phone from somewhere on the internet, he decided that the fault must lie somewhere in the wiring at the left wing root. To get to it, I had to pull the wing.😡 This task is not as onerous as it might first seem since the RV-12 is designed for easy wing removal, very similar to that of a glider.
I see a lot of talk on the forums about systems that allow one person to remove a wing unassisted. Mine is simple: a 4x8 sheet of plywood with legs on casters. The top of the table is just below the inboard end of the wing. Moving blankets get stuffed between the table top and the bottom of the wing, accounting for dihedral. When the spar pins are pulled, the table and wing can be easily pulled away from the airplane.
After removing the mountain of crap that had grown up atop my wing table, I pulled the left wing just enough to allow the wiring to be accessed. The tube seen going from the wing root into the side of the fuselage takes a pressure signal from the AOA port on the wing leading edge to the ADAHRS box mounted in the tail cone.
After Dan made some measurements to confirm his original diagnosis, I discovered that two of the seven wires going into the Molex plug shown had pins which were not properly inserted. I still find this hard to believe since my standard procedure with Molex or d-sub pins is as follows: crimp the pin, tug the pin on the wire, insert the pin into the female plug, tug the wire to ensure proper insertion.
The blue connector shown automatically connects the wires from the fuselage to the nav and strobe lights and the stall warning vane when the wing is installed. A corresponding one on the right side also has the wire for the landing light. With the headset plugs hanging out in the air as shown and the blue plug not connected, the radio worked great. Problem solved! Turns out, one problem was solved and one was yet to be revealed.
Happily, I re-installed the wiring in the fuselage, re-installed the wing and plugged in the headset: loud squeal. As Tom Cruise's sidekick said in the movie Risky Business, sometimes you just have to say WTF (abbreviated here due to the family nature of this blog).
Somehow, when the two halves of the blue plug came together, the squeal starts. The nav and strobe lights work fine, which leaves the stall vane. Turns out that by moving the stall vane around, I could make the squeal start and stop. In its relaxed state, this normally-open switch was closed. This new "squeal" I was hearing was the stall warning horn! The switch/vane assembly can be reached (barely) by removing an inspection plate. Sticking my phone in the wing, I got a picture of the assembly (shown).
The assembly consists of the microswitch and vane sandwiched between two plates. When I built this thing I remember fearing that if I over-torqued the bolts I might crack the plastic housing of the switch. The result was an assembly which was no where near rigid enough. I could grab the outer plate and move it relative to the inner one. Another self-inflicted wound. Nothing to do but remove, re-torque and re-install. Turned out to be one of the more challenging and frustrating things I've had to do on the build.
The really maddening thing is that most people with AOA disconnect the stall vane after certification, which no doubt I'll do, making all this a waste of time. But, being an E-LSA it must be built exactly like the ASTM prototype. Right?
Off topic: more Colorado wildlife in my back yard recently. Look at the rack on that one guy to the right.
