« Posts tagged wiring

Rockin the clock.

5 hours.

Last time I went flying, there was a very odd glitch.  On the first takeoff of the day, if I do a quick pattern, on base leg before final, I’ll lose my AHRS and compass.   This was intermittent, and I couldn’t reproduce it on the ground.   This week it got worse: If I landed and taxied back to the hangar and shut down the engine, the instruments would come back.  With the engine running, the AHRS and compass are inop.  This is WEIRD.   Strange things happen when voltage dips below 10v, but my backup battery and system voltage both were above 12v.   A quick check of the RCA cables revealed one loose.

Bingo.  RCA cables as aircraft duty connectors are a the worst idea in a collection of bad ideas, but there’s not a lot I can do about it.    Added item to maintenance checklist.   No weirdness from the radio either.

But the futzing around cost me an hour of valuable good weather.  I had planned to get 4 hours of flight time today; I got 2.   That’s only 14 hours left on the Phase 1 countdown clock.   But I need all this crap to stop happening so I can do some real tests.


Even more legal, and some argh

10 hours.

Friday I got the static/transponder test done and that’s now in the logbook.   That took a bit, because I had to chase down some leaks.   And, somehow, I managed to snap off the hose barb that connects to the EFIS’s AOA pressure sensor.   That really, really sucks.   Now, once again, I have to dismount the EFIS and take it to MGL to have the AOA sensor replaced.  Can’t fix the barb.  The good news is that the AOA isn’t really necessary for first flight.   Also, my combination AOA/Pitot doesn’t lend itself well to the usual testing method of slipping a hose over the end of the pitot and hooking it up to the test machine.   But we worked around it by connecting the test line to the fitting where it connects to the pitot tube, so I’m going to assume it works.   We’ll find out.

Static tests eventually worked out OK, and we were able to calibrate using the EFIS’s setup menus.    All good!  Signed off, sticker in the airframe logbook.

Today was about picking up the pieces and extracting the EFIS backup battery for replacement.   I think it got run down too far too often and now it won’t take a charge and tops out at 6v.   To do that, I had to relocate the IO Extender module to someplace that would allow me to get to the screw securing the backup battery in its bracket.   When I had to move the IOX before to get it out of the way of the canopy, I’d put it on the end of a piece of angle behind the EFIS.  This solution was kind of half-assed, and I never actually felt good about it, so this is actually an improvement: I put it on top of the throttle quadrant bracket, up out of the way of everything.   I’ll have to dismount the transponder to make changes to the wiring, but that’s OK, it shouldn’t be necessary to change the wiring much.  It’s much more elegant, and gives me plenty of room behind the EFIS to do what I need to do, plus it’s more secure.

I did have to extend the power and ground wires for the IOX, but I was able to use the trim position wires as-is.  It also enabled a much neater wiring bundle instead of the slightly messy arrangement I had previously.

“Twas the Weekend Before Christmas, and All Through the Hangar…”

4 hours.

“Not a creature was stirring, save this rivet banger…”

This encompasses Saturday through Monday.

With the holidays in full swing, the schedule gets a little weird, but better, because I have a few days off.   I’m keeping a decent balance between building, home obligations, holiday festivities, and the occasional video game.   I’m also coming to terms with the fact that the endgame for this project is approaching rapidly, or so it seems to me.   Last weekend, I’d started on the gear leg fairings.   This weekend, I pretty much got them done.

The most important thing with the gear leg fairings is to build them without any twist in them.   They come taped together from the factory, but Van’s fiberglass is usually so crappy for fit, I didn’t trust them.   The way you verify no twist is to put the leading edge on a flat surface and using a square, insure that both trailing edges line up.   Once that’s done, you can use the full-scale template cut from the plans to mark all the cut lines.   Easier said than done, though.  You really need two squares, one for each end, and another pair of hands, or at least a boatload of tape.   But I found a solution in our hangar that worked very nicely:

IMG_1710That brass thing is a piece of channel from one of those godawful floor-to-ceiling mirrored sliding doors, usually found in cheesy SoCal apartments that saw their last renovation some time before Saddam Hussein rolled his tanks into Kuwait City.   But it makes a very nice, very straight jig for lining up the trailing edges of the gear leg fairings.   Not only that, it provides an excellent platform for match-drilling the hinges.   Some of you are looking at this and saying “hey, those are the wrong size hinges!”  Yes they are.   But it’s what I had.   I used up all my 1/16″ piano hinge on various attempts at the cowl.   If it should come to pass that these hinges cost me knots and fuel, I’ll change them out, but at this point, I want to be done.


A selfie, checking the alignment of the hinge.

With those done, I could check out the fit of my intersection fairings.


Upper intersection fairing fits, sort of.   It needs some work.   It’ll also need to be taped into position to hug the contour of the fuse and cowl, and then a couple of layups on top of that.   After that, it gets trimmed back to where it’s supposed to be.   Van’s fiberglass may be crap, but it’s better than mine and it sure beats fiddling around with modeling clay.

Monday was all about tying up as many loose ends as I could before starting on the wheel pants.   This meant, among other things, getting as ready for the inspection as possible.   I attached the ‘EXPERIMENTAL’ sticker to the roll bar:


This is a bit redundant because the baggage bulkhead cover that came with the interior has it embroidered into the leather, but that won’t be installed during the inspection.   The canopy frame covers this one up when the canopy is down, but I don’t think that matters.   If it does, those stickers are cheap.


This is required by the Feds to be in the airplane in plain view of the occupants.  It’s like a magic amulet to ward off the unadventurous.

Left Gear Leg

Left Gear leg

Left Gear leg works much the same way.

After this, I spent some time doing odd jobs.   I safety-wired the tailwheel chain hardware, then moved to the cockpit, where I zip-tied the wires made loose by the magneto troubleshooting and the addition of the OAT probe.    I also attached bolts in the center section per Van’s SB 12-08-14.   Apparently enough people forget this step that Van’s thought it merited a Service Bulletin.   Guess what?  I forgot it too.   In addition to the close-tolerance bolts that hold the wing spars to the center section, there are two on each side that secure the center section to the vertical bar on the wing spar.  These need some AN4 bolts in there to lock things down.

Part of getting airworthy is checking all the relevant SB’s and AD’s to make sure you don’t have anything hanging in the breeze that might kill you.   The rules on experimental aircraft and AD’s are fuzzy, and are interpreted by various people in various ways, because different sections of the FAR’s appear to contradict each other.    But the safe thing to do is check for AD’s and SB’s that apply to your stuff and fix them if you find any.   If I hadn’t gone through this process, I wouldn’t have found those missing bolts and the inspector would have.

When I moved on to the engine, I discovered some oil running down from the spacer on the right mag and at the oil drain fitting of the #1 cylinder.   This was alarming enough to merit a quick engine test.   I cleaned off the oil and wheeled it out to start up, to verify that the oil was new and not left over from the last time I had to loosen them up to get to one thing or another.

I did a quick runup and brought the cht’s up to operating temperature, but even with good, timed mags, it still stumbled off idle.   Advancing the throttle slowly would bring the RPM up, but moving it smartly, like I would for takeoff, killed the engine.   After consulting VAF and then my AFP manual, it looks like my idle mixture is set too lean.   This will need to be corrected, and I can probably do this tomorrow.  The good news is that I didn’t see any new oil in the spots where I found the drips, so it looks like the oil around the mag spacer was from when I had the mags off, and the oil from the #1 drain line is from the time I had to undo the fitting at the cylinder head to get at either the bottom spark plug or the EGT probe.



Working on engine-start squawks.

7 hours.

Last week’s engine start, while exciting, wasn’t without issues.   The one I thought was going to be most difficult to fix turned out not to be.   The governor operation was reversed, and the fix turned out to be pretty simple.   I just flipped the governor bracket over and mounted it so the cable operates the arm from below.     All I had to do was put a small piece of angle on the side of the arm to secure the #2 fuel injector line.   We’ll have to see about conflict with the cowl.  I put the top cowl on and it looks like there might be about 1/8″ of clearance between the new governor cable arc and the underside of the cowl.  That’s not a huge deal though, and I’d rather put a blister on there than go through the hassle of dismounting the governor and sending it back to American Propeller to see if maybe, just maybe, they can reverse the operation.   Either way, that would cost me in time, in shipping, in ability to test the engine in other ways and debug the two sensor squawks from last time.   The hardest part was the firewall-penetration eyeball.  It’s almost impossible to get to and I still need to torque it down, because it’s not laying flat like it’s supposed to.  I had to take it out so I could get the extra half inch of cable slack necessary for the flipped bracket.

On the others, I had no luck.   No RPM reading, no oil temperature reading, although I have no idea how long it takes the oil to warm up to a minimum of 72 degrees.    The rpm thing is a little scarier because i don’t know if it’s the wiring, the sensor, or the magneto the sensor is attached to.   I’m going to have to break down the wiring of those two pieces and go through it piece by piece.   I really hope the senders aren’t bad, because those things are not cheap.  Replacing both is about a taildragger lesson’s worth.

Speaking of which, I have replaced the ON/ON/(ON) magneto switches with ON/ON DPST  switches.   One side of the switch handles the start circuit and the other handles  the mags.   When the start circuit is enabled, the magnetos are ungrounded.   Since I have two impulse-coupled mags, I can get away with this.   At this point, the starter button on the stick is the only way to kick the engine over now, which is OK, but I plan to install a pushbutton to forcibly engage the starter should the relay the stick button actuates takes a dive.

The magneto timing still needs work.  Even after the switch replacement, the right magneto still makes the engine backfire like mad when it’s on its own.   I’ll need to retime it anyway when I install the new gaskets, but it’s still a royal pain and I’m not keen on doing too many more runs with it in that condition.

Oh, and joy of joys, there’s a small crack in my canopy, in the aft right corner, coming up from the last screw hole on the canopy frame.   I didn’t catch it until now, because it has been  covered with masking tape, which I removed yesterday.   I removed all the protective plastic from the canopy, except for a swatch between the rear canopy and the roll bar brace.   Now the fun is going to be getting that last piece of plastic out from there.  I’ll probably have to dismount the rear canopy, which I would have had to do anyway to get some kind of seal in there.

Engine Start, Part 2.

  1. 5 hours.

Armed with last weekend’s knowledge and suspicion, David and I headed up to OXR to debug and correct the mag and start wiring, then actually start the engine.    We had a copy of The AeroElectric Connection and more importantly, the airport gate card, which allowed us to come and go as we pleased.

Even though we knew what was wrong, it was puzzling, because we were trying to follow Bob’s diagram and make an open circuit for one thing while making a closed circuit for another.   Maddening.

Eventually, we did figure it out and we were rewarded with the sound of an airplane coming to life.

Hooray! Huge milestone, and only three squawks:

  1. No RPM reading.   This is most likely a bad ground or a severed wire coming from the pickup on the magneto.
  2. No Oil Temperature reading.   Maybe this shares a ground with the tach sensor.
  3. (and this is a big one)  Governor operation reversed.   The prop does cycle and the governor doesn’t leak, but it operates the wrong way.   I need to set it up so the prop increases pitch when I pull the blue lever back.

No leaks, no fires, no pieces flying off.   I’d call it a good day!

Engine Start, Part 1.

6 hours.

A tiring and ultimately unsuccessful day.   Dave and I went out to the airport with the intention of starting the engine for the first time.   We were off to a stellar start: I’d forgotten my airport key card; it was still attached to my motorcycle safety vest at home. I didn’t notice it until we were actually in Oxnard, so that sucked.   We did manage to find somebody to let us in, then went about the business of readying the plane for engine start.   We dumped 8 quarts of oil in the tube, then attempted to time the magnetos.    This is harder than it sounds.   Once we actually figured out how to use the buzz box, the cylinder plug, and our own eyes, we got the mags in and timed to the engine.   That’s when the fun started.

We wheeled the plane outside and prepared to start it up.   We left the distributor caps off the mags so we could spin the engine a bit and pre-oil it.   with four plugs removed, we were able to spin the engine around and get oil into all the nooks and crannies and actually see an oil pressure reading come up on the EFIS.      Prop spins, there’s oil, let’s start it!  Foolish us.   Slick magnetos are designed to run when their circuit is open, that is, the two leads connected to them, when connected to each other, make the magneto safe, cold, whatever.   The AeroElectric diagram has you connecting these two switches together in such a way that the right mag fires when you’re starting and the left one doesn’t do squat until the engine’s running, that is, you’ve let go of the spring-loaded upper position toggle because the engine is running.

Somehow, I’d wired it in such a way that the mags were connected/safe when the switches were “on” and the start circuit was on.   The engine spun, but wouldn’t start.   Fortunately, safety wasn’t in question.   The way I had it wired, no matter what position the toggles were in, the mags were grounded, so it’s not like the prop would have taken our faces off.

By the time we’d gotten wind of the problem, it was too late to debug and we were tired.  Tired people working with dangerous things tend to get hurt, so we packed it in and crawled home, after begging to be let out the airport gate.

A Fix and Some Finishing

7 hours.

Although the last three shouldn’t count because I spent them fixing something I should never have had to in the first place.

20130728-192738.jpgThat little corner of aluminum is the bane of my life.    Since I put the wings on, I’ve caught it on shoes, shirts, and finally, the belt on my jeans.   When this happens, it bends.   This time, I bent the crap out of it, so badly, that I had to remove the fasteners on the skin, peel it back, and hammer it flat again.  The light makes it look worse than it is, but it’s still pretty bad.   Fixed now, though.


20130728-192751.jpgThe day wasn’t all bad.   I got the fuel pump overflow plumbed.   I used some of the tubing I had from the MAP sensor install to create a flexible link between the output of the fuel pump to the hard line shown here.   The engine wiggles.  The aluminum tubing doesn’t.   I need a flexible line between the two.

20130728-192805.jpgThe fuel sensors concerned me for a minute.   When I connected the wings, I had some little extra wires that I thought I’d run for spares.   I guess this is why you label things.   After some pondering, I realized these were the fuel level sender wires.   Duh.  The good news is that I didn’t have to do any splicing and apparently I cut them to the right length.   A couple of connectors later and I had fuel level, which was, of course, zero.

No luck on the OAT sender though.   Either my EFIS or the probe is bunk.   OAT reads a steady 32 degrees F.  Have to contact MGL for a new one.

Still more connections.

6.5 hours.

A bit of a late start.   Since I took this week off, yesterday was my first weekday commute to OXR.   I went via PCH, which is nice enough, but it took a little longer, especially during rush hour.

I finished installing the rudder cable linkages to the pedals, so that’s another thing done.   I also got the pitch trim servo wired in.  I’ll need to adjust the throw on the trim servo, but that’s essentially done.

Then I went back to wing wiring.   I got the strobe and lights connected for the right wing, plus the autopilot servo.  It was lots of tedious, fiddly stripping and crimping in small, awkward places, which has an extra coating of suck because I did something to my right elbow and now operating hand tools like crimpers is fairly painful.

Left to do is connecting the VOR antenna wire (This may become an ADSB antenna wire if they phase out VOR) in the left wing and putting in a couple of pieces of UHMW tape here and there.  If I can have lights, strobes and VOR by the weekend, I’ll count myself lucky.


The Thing Has Wings!

3 hours.

This morning, Dave and Peg picked me up from home and we met Derek at the airport to fly up to OXR in his 177RG Cardinal.  It took a while to get out of SMO because somebody’s bizjet blew a tire and was stuck on the runway for half an hour, but we finally got off the ground and got to Oxnard.   There, we put the wings on the RV, which involved a lot of shuffling things around in the hangar space and trying not to bash the other occupants, the structure, or each other, with ungainly airplane parts.

The wings did go on, after a fashion.   Our time here was abbreviated because of earlier runway delays, so the wings are currently held on with the sacrificial hardware store 5/16 bolts I used during the initial alignment and the proper AN5 aft spar bolts.  My hangar mate Ron and a friend of his helped us get the overlap sorted out on the right wing, and all totaled it didn’t really take more than an hour once we arranged everything in the shop and actually began putting the wings on.

It truly was a 4-person job.   Derek, Dave and I wiggled the wing into place, Peg kept the wires from getting fouled, and then I bashed the 5/16 bolts through with the rest of the crew doing precision wiggling where needed.





One thing I should have done is left the flaps off.   We tried getting the left wing on with the flap on and that didn’t go so well, especially when it came time to line up the aft spar holes.   I wound up taking the flap off the left wing, then took the flap off the right wing before we tried to put that on.   So what you see here is the current state, which is the big flat bits that make the plane stay up in the air, stuck to the bit that holds the meatbags off the ground.

As an aside, I’m hoping that when I connect the control push tubes, the sticks are a little more limited in their side to side travel, because currently, my hand just barely grazes the quadrant.

Wings done! Really.

2 hours.

Wings are ready for move to the hangar. Cleaned up/fastened some wiring, perma-mounted the flaps, switched the shop back into fuselage mode.