October 2011 Archives

Misc Panel Wiring

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I finished up all of the isolation diode wiring and tidied up the wires.  I then torqued all of the screws down with a torque screwdriver.

One of the last things to be wired through the isolation diodes was the autopilot servos.  I wired them up through a pullable circuit breaker and then down to the wires under the seats.  Afterward, I fired up the SkyView system and verified it could see the pitch servo.  After a quick servo firmware update, I calibrated it temporarily and then verified the autopilot controlled it correctly.

You can see here that I also wired up the hobbs meter.  The positive side is wired to the battery bus and the negative side is wired to the normally open side of the oil pressure switch.  I verified the current draw with an amp meter to determine the fuse size (1 amp is way more than enough).

Here are the three wires to the oil pressure switch.  The bottom wire is ground, the middle is the normally open contact to the hobbs switch, the the top is the normally closed wire that runs to the annunciator control circuit.  When the engine is running and oil pressure is applied, the switch closes which grounds the hobbs meter and starts it running while simultaneously opening the line to the annunciator control circuit which extinguishes the oil pressure light.

I also used some 20AWG shielded wire to connect up the mag switch.  On the mag end, the center conductor is connected to the far post, while the shield is split off and wired to the ground post on the mag.  I little heat shrink keeps everything tidy.

On the switch end, the shielded wire comes in on the bottom and has a similar split,  The center conductor is also connected to a tap wire that includes a 30kΩ resistor.  This wire goes to the SkyView EMS to provide RPM indication.  The Lightspeed ignition also provides RPM indication, so the SkyView has redundant sources for this info.

Cleaned Out the Garage

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It has been a long time since the garage was cleaned out thoroughly, so I pulled the plane out into the driveway and gave everything a good once over.

After pulling the plane back in the garage, I started wiring up the starter switch.  I installed all of the wires in the back of the switch, but haven't hooked any of them up to anything.  The two red wires will be hooked to the starter switch pin on the VP-X which is only enabled when the engine isn't running.  The black wire is the ground wire for the internal light.  The white wire with the red stripe is the switched power wire to the starter contactor.  The VP-X manual calls for a 18AWG wire for the starter, but the starter only pulls about 3.6A.  Given how little time these wires are asked to carry that current, the temperature rise in a 22AWG wire is just fine, so that is what I used.

I wired up the engine start switch tonight.  The internal light illuminates when the switch is active.  Pressing is results in a satisfying clunk of the starter contactor (the starter wire is disconnected of course).

Robert at pilotlights.net has started carrying new 7A dimmers.  I ordered a couple to see if they'll work to control the seat heaters.  The seats draw about 2.7A each, and I'll have one of these per seat, so that gives plenty of margin.  I ran these at 2.7A for awhile, and the heat sink only gets 6-7ºF above ambient.

I pulled out my seats and hooked up the dimmers (bypassing that huge bundle of wire, connectors, relay and switch in the lower right that come with the seats).  The dimmers work beautifully with the seats.  The voltage varies linearly with the knob position.  I had a little scare when the current through the seat bottom suddenly dropped to almost zero (~10mA).  I checked the dimmer and voltage at the seat, and everything looked good.  After a few minutes of head scratching, the current suddenly jumped back to the original value.  Apparently, the seat heaters have thermistors built in to them to prevent over-heating.

I drilled a couple of holes in the subpanel for the ELT audio box.  This emits beeps to indicate that the ELT is transmitting or when performing a self-test.  I also cut and installed modular plugs on the end of the cable and fabricated a custom short cable for the run from this box up to the remote.

Here's the other end of the cable from the audio box.  After installing this, I put the ELT switch in the armed position and hit the test button on the remote to perform a self-test.  Initially, the ELT reported a high VSWR error which makes sense since I hadn't yet installed the ELT antenna.  I quickly threw a BNC connector on the end of the antenna cable and connected the antenna.  Re-running the self-test indicated that all systems were functioning properly.  I still need to confirm that the ELT is properly receiving position data from the GTN, but I need to fabricate a small test circuit to do that.

I received another order from Aircraft Spruce with some 18AWG shielded wire.  The piece that came with the electronic ignition wasn't long enough to run from the unit to the switch, then to the breaker, and finally to the battery bus.  I used a solder sleeve to join the shields of two pieces and then connected their center conductors to the NO side of a 1-3 switch.

From the switch, the wire runs to the breaker where a similar connection is made.

The center conductor of the shielded wire is connected to the batter bus (the upper right fuse here).  Another solder sleeve is used to connect an 18AWG black wire to the shield.  The installation manual specifies that this should be directly connected to the battery, but I'm trying to limit unprotected wires in the aircraft as much as possible.  Connecting this here adds only a couple of connections over the recommended wiring method, and these are very high reliability connections.

That black wire then runs to the ground block.  I drilled a hole through the firewall to anchor the other end of the ground block and attached the wire there.  I doubt this is significantly more reliable than one of the fast-on connectors, but it's about as reliable a connection as you can make short of connecting it directly to the battery ground terminal.

I had a little more energy, so I quickly fabricated the ELT data verification circuit and hooked it up to the wire that I left sticking out of the ELT connector.  I fired up the avionics and verified that after the GTN had acquired a GPS fix, the light started flashing about once a second to indicate that the ELT was receiving valid position data.

I wired up the remaining annunciator lights (other than the "Canopy Unsafe" light).  The final three were the landing and taxi lights as well as the fuel pump.  This unfortunately unveiled a flaw in the annunciator control circuit I designed.  Basically, for annunciator lights that are triggered high, I was assuming the transistor base voltage would be shed through the load when the load was turned off.  The problem is that for certain types of loads (e.g. LED lights), the load resistance is pretty high at low voltages.  This has the effect of causing the transistor base voltage to fall pretty slowly after the load is turned off, which causes the annunciator light to dim slowly.  I really need to couple the base and emitter with a resistor to provide an alternate path for the base voltage to drain.  I'll have to redesign the circuit and have new PCBs made.

Installed Control Cables

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I installed the control cables in the bracket and clamped it to the panel with a couple of c-clamps.  You can see that I offset the bracket to the right so that the three engine controls are centered on the panel.  I did this to give myself more knee room.  It will be very rare that I fly with someone as tall as me (6' 4"), and no one will ever take off or land from the right seat, so their knee room isn't as important.  The small knob on the right is the parking brake.

The throttle cable comes through the hole below the cabin heat box.  I haven't installed the eyeballs in the firewall yet since I'm just trying to make sure the cable lengths are correct and determine where they will run.

The throttle cable attaches to the custom bracket I made and then to the throttle arm.  The length and fit of the parts is perfect.  I can easily adjust the throw so that the knob is sticking out about 1/8" when the throttle bracket hits the stop (you do this so that you know you're hitting the control arm stop and not just the cable stop).  I'm going to replace this all-metal stop nut (which is acceptable) with a drilled bolt, castle nut and cotter pin (which is preferred).

The mixture cable penetrates the hole just under the manifold and runs just above where the oil cooler will be mounted.  I'll use some adel clamps to keep everything from rubbing on the oil cooler flange.

The cable then drops below the engine mount tube holding the oil cooler and on up to the mounting bracket.

The forward end of the cable connects to the mixture idler arm.  I had to lengthen the small pushrod at the other end of the idler arm to get the mixture control arm to contact the stop, but in the end it works beautifully.

The prop cable penetrates the far left hole (right in this picture since we're looking aft) at a pretty severe angle since it needs to mount to the governor on the back of the engine.

The end of the cable attaches to the governor control arm.  After some adjusting, the throw on the prop governor is perfect as well.  I do need to replace this bolt though.  It's too short and I want to use a castle nut and cotter pin just like the other control cables.  I did have to reverse the bolt from the orientation specified in the plans since it's just about impossible to insert/remove the bolt the other way since there is not enough space between the control arm and back end of the governor.

With the engine controls in their final location, I marked both sticks and cut them off.  I'm using the teak grips, so they extend the sticks a couple of inches or so.  For reference, I cut 4 1/4" off the pilots stick and 3 11/16" off of the co-pilot's stick.  This puts the bottom of the grips (and therefore the hand) the same distance from the pivot point for either stick.

I needed to cut this much off to ensure the grip clears the throttle when at idle.  This gives me a comfortable clearance even with my finger on top of the grip.  It might be a little tight if my hand is resting on the throttle at the same time, but I don't want to cut off any more than I need to.

I installed both sticks and the push-rod that connects them.

The pushrod transfers the aileron control between the sticks and between the wings.  I did forget to install the aileron trim clips the first time I installed the pushrod.

Here's where the clip should be installed.  When the ailerons are in the neutral position, the clip points at the end of the trim servo arm.  The clip is bent out away from the pushrod just enough that the trim spring doesn't touch the pushrod.

When the stick is in the full forward and left position, the spring is attached to the trim servo arm so that the spring is very slightly extended.  This prevents the spring from ever going slack regardless of the position of the controls.  There will be another spring tying the co-pilot's stick to the other hole in the trim servo arm.

The bundle of wires from the pilot's stick exits through the bottom (between the bearings) and is tied to the connecting pushrod in a couple of spots to prevent interference with the trim spring and the adjacent rib.  The bay just inboard of the stick will provide room for the wire bundle to flex as the stick is moved.

I finished the aileron trim by installing the right clip and attaching the spring between the clip and the servo arm with some 0.041" safety wire.

I adjusted the length of the safety wire so that the sticks naturally rest vertically when the servo arm is in the neutral position.  I ran the trim to both ends and moved the sticks in all directions to ensure that nothing could snag or interfere with the sticks.  I had to adjust the bend in the servo arm slightly to keep the safety wire from interfering with the rib just to the right of center.

Next up, I installed the dimmers for the seat heaters.  The control cable to the right is for the cabin heat, so all of the heat controls are located together.

I prepped the wires and attached them to the dimmers.  It's too late to run these wires tonight, so I'll finish these off tomorrow.

I fabricated the headset jack brackets from some 0.040" bent sheet.  These were cut from the original engine control bracket that Van's includes in the kit.  I drilled the holes 1" apart and drill three staggered holes to mount the brackets to the bulkheads.  Here's the copilot's bracket.

And here's the pilot's bracket.  These are mounted high enough that they'll never accidentally be kicked or bumped, but low enough that you can still lean over just a bit to see when plugging in the headset.

I then wired up the pilot's jacks.  The mic jack is on the top and includes two extra wires that are routed to the pilot's push-to-talk button.  I then routed those two wires back to the pilot's stick.

There is just over 1/4" of clearance between the plugs and the face of the bulkhead.  The interior side panels will mount to this face and are approximately 1/8" thick.  This will keep the plugs fairly tight against the side panels without causing them to rub against it.

Here's how I ended up deciding to secure the stick wiring.  The bundle exits the bottom of the stick between the bearings and then wraps around the end and back up the side where it is anchored with a couple of zip ties.  It then curves over and is anchored to the adjacent rib with an adel clamp.

Because the bundle curves away from the stick pretty much right at the pivot point, the length hardly changes as the stick is moved.  The position with the least slack is with the stick in the aft left position.

Moving the stick to the fore right position creates the most slack in the bundle.  I'm really happy with this arrangement as the bundle has very little flex and has no chance of interfering with the control stick or aileron trim.

I finished wiring up the pilot's stick grip tonight.  The bundle from the stick terminates at the connector on the left so that the stick can be removed without having to disassemble any of the wiring.

In the next bay to the right, the ground wires split off and are grounded to the rib with a #8 screw since these are just ground sense wires.  I cleaned off the primer and used some Noalox anti-oxidant compound to ensure a good ground.  The yellow wires from the autopilot servos are tied together here and connected to ground through a 5kΩ resistor which allows the SkyView system to detect a broken autopilot disconnect wire.  They can also be shorted directly to ground through the CWS button on the stick which triggers the CWS and autopilot disconnect functionality.  Six of the wires (four trim wires and PTT wires) proceed from here up behind the subpanel.

With the final four connections made on the J2 connector, I installed the connector shells on J1 and J2.  Finally, I fired up the avionics and verified that I can transmit on the radio, control the autopilot, and drive the trim.  I did notice one oddity though.  When I first tried running the trim with the coolie hat, the aileron trim ran backward from the way it should have.  I hooked up the laptop and double checked that the coolie hat was wired up correctly and it was.  Reversing the motor addressed this problem, but created another.  When I go to the VP-X page on the SkyView and scroll to the roll trim device, the Left and Right buttons at the bottom of the screen now are reversed.  I also configured the trim widget on the engine control page and noticed another oddity, when I trim all the way to the right, the arrow moves all the way to the left.  Looks like it's time to contact Dynon again.

I spoke with Dynon this morning and they were already aware of the reverse trim issue.  The fix will require software updates to both the Dynon SkyView and the VP-X, but those aren't out yet.  It's not blocking anything for me right now, so I'll just wait for the updates.

I moved ahead and finished the power and ground wires for the seat heaters.  I *think* this will be the last ground wire that attaches to the firewall ground block.

Next up, I started wiring the interior lights.  I had been planning on wiring the cabin lights (in the roll bar support channel) directly to the battery bus so that I can turn them on without turning on the master switch.  I originally ordered a linear dimmer module from Perihelion Design.  This has the nice feature that when the knob is turned off, the dimmer draws absolutely no power.  A while back though, I decided to switch to a PWM dimmer from pilotlights.net.  The dimmer provides a much smoother and more linear brightness ramp, but unfortunately it draws between 6 and 13 mA even when the output is open.  At 13 mA, that would completely drain my battery in ~54 days, but it would drain enough power to affect starting in quite a bit less time.  I don't really see a way around this since the dimmer has to be connected prior to the switch that routes power to either the white or green cabin lights, so there's no way to shut off power to the dimmer if it's wired directly to the battery bus.  I've decided to just move the cabin lights to the interior lights circuit on the VP-X.  This will eliminate the current drain but will unfortunately mean I will have to turn on the master switch to turn on the cabin lights.
I wanted to make some more progress on the interior lights, but I first needed to determine if I have to shorten the LED light strip that will illuminate the glare shield.  Although the light strip is shorter than the edge of the glare shield, I wanted to make sure the end lights weren't visible since the glare shield curves down on each end.  In order to determine that though, I needed to install the glare shield trim.  I determined the centerline and clamped the template in place to mark the holes.

I then drilled the holes and mounted the glare shield trim.  This is padded and has a nice french seam on the facing edge.  I then sat in the plane to determine if the trim will hide all of the lights in the LED light strip.  Fortunately, it does and I can go ahead and install it.

I determined the centerline of the light strip and then adhered it in place.  I'll paint these mounting screws to match the surrounding surface before installing the trim permanently.

On the left end of the light strip, I installed some nylon sleeving and heat shrink tubing and then tucked it behind the brace.

I used some E6000 to adhere the cable in the channel.  The cable will exit the canopy through a hole in the brace that I need to drill.

I used some popsicle sticks and tape to hold the cable down in the channel while the E6000 cures.  I'll finish routing the wire after that.

I decided to get back to the seat heater wiring.  I need the cables coming from the seats to be easily removable whenever the seats are removed. I picked up some power jacks from Radio Shack and wired up a couple of these adaptors.

I then drilled a couple of 5/16" holes in the inboard seat ribs and seat pan on both sides.

Here is the adaptor installed.  I then ran the wires for the right seat heater, hooked them up and verified proper operation.

I'll use these corresponding plugs on the ends of the cables coming from each seat bottom and seat back.

I finished running the wires for the left seat heaters.  I had to pull the pushrod back so that I could install a few zip-tie bases to anchor the wires to the seat rib.

I drilled a hole for the glare shield wire bundle and installed a rubber grommet.  I installed another zip-tie base to secure the wire next to the fuel sender and installed the rest of the wires to the dimmer and panel ground block.

I meant to install the vent ducts earlier to ensure that nothing interferes.  Unfortunately, I ran the pilot's side headset wires right through the duct path.  They're not long enough to route over the duct, so I'll have to route them under it.  It's not that big a deal, but you should install these as soon as the panel goes in to avoid running into any interference later.  Most things have some flexibility about how they're routed, but these can pretty much only run here.

Ran Copilot PTT Wires

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I spent most of the night cleaning out the garage and organizing my wire drawer (it had become a real rats nest), but I did manage to secure the copilot's wire bundle to the adjacent rib and install a molex connector at the end.  I snaked the wires on the other side of the connector up behind the panel and over to where the copilot's headset jacks are installed.

Vertical Power released version 1.3 of their VP-X firmware today.  I installed it and it resolved the issue with the reversed trim buttons on the SkyView.  Now, whether I press the coolie hat on the stick to the right or press the "Right" button on the SkyView, the stick goes right.

I spent the rest of the night messing around with the oil cooler position.  I think I'm finally pretty happy with the location.  I ended up turning the oil cooler over from the way I had it so that the oil cooler hoses attach on the bottom.  With the oil cooler mounted on the baffles, it's higher than the oil return line on the engine, so oil drains out of the oil cooler automatically during oil changes.  With the oil cooler mounted on the engine mount or firewall, it's below the oil return line, so most of 1 qt of oil would be trapped in the oil cooler during oil changes.  I did some research on this, and this is not too uncommon on certified airplanes, and the way to deal with it is to make the oil hoses enter from the bottom and put a tee in the lowest fitting.  One side of the tee will go back to the engine, and the other side will just contain a cap.  During oil changes, this cap can be removed to drain the oil out of the cooler and hoses.
When I purchased the autopilot servo to install in the wings, Dynon had not yet announced that it couldn't be updated to work with the SkyView without using one of the first gen products.  Even after they announced that, I thought for a long time that I would be using a D6 as my backup EFIS and could update the firmware with that.  Once I decided to using the TruTrak Gemini instead, that meant I needed to have Dynon do the firmware update.  I mailed my roll servo back to Dynon last week and got it back today.  I'll get my wings back tonight and reinstall it soon.
I picked up my wings from my next door neighbor where he's graciously stored them for the past nearly two years.  I'm going to be mating them to the fuselage in about a week.  Since I'll be moving to the airport in a few months, I'll probably just end up storing them on the side of my house till then.

I installed a male DB-9 connector on the end of the wires from the roll servo.  I took this picture mostly to document the wire positions in the connector.  Not easily visible is the black wire that is connected to pin #2 (straight behind the red wire and just to the left of the green wire).

Here's the finished connector with some expandable nylon sleeving over the bundle.

I reinstalled the roll servo and torqued/safety wired the bolts.  I then temporarily hooked up the servo to the SkyView network and calibrated it.  I'll have to redo the calibration once the wings are on, but everything seems to be working properly.

I installed a small microswitch to sense when the canopy is latched.  The switch is only activated when the latch finger is rotated back and the catch is in place.  I ran a wire from the annunciator control circuit back to here.  It will be grounded locally when the switch is open.

Attached Empennage

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My goal for today was to get the empennage attached to the fuselage.  I came out to the garage early and fabricated the rear elevator pushrod since I'd need it to hook up the elevators.

My buddy Andre dropped by to help me attach the empennage.  I then pulled the plane most of the way out of the garage to make some more room, then placed the horizontal stabilizer in place.  The forward spar sits on a couple of spacers that Andre fabricated for me.

The rear spar sits on a couple of 3/16" drill bits to space it up off the deck.  I measured the tooling holes to ensure that the stabilizer incidence is 0º.

I then laid out the holes that will be drilled in the forward spar.  The outer holes (right in this picture) penetrate this angle, the spacer, the aft deck, the longeron, and the cross brace.  There's over 1/2" of material here that is bolted together.

I then drilled the holes.  The outer ones can be drilled and reamed straight on, but I had to use the angle drill to do the inner ones.

I then laid out and drilled the holes through the aft spar and attach bars.

We then hung the elevators and drilled the pushrod attach hole.  Andre then helped me temporarily attach the vertical stabilizer.

Jenn came out a little later and snapped this picture of me working on positioning the vertical stabilizer.

Getting the vertical stabilizer positioned accurately took much longer than the horizontal stabilizer.  The stabilizer has to be perpendicular to the horizontal stabilizer, tipped back at the right angle so that the hinge brackets are in a straight line, then twisted so that the front edge is 1/4" left of centerline.  It took quite a number of iterations before I had everything nailed.

I then fabricated and clamped the up elevator stop.

This is then drilled to the vertical stabilizer rear spar.

I removed the stop and drilled the remaining holes, then reinstalled it and match drilled the longerons to the stop.

I then installed a washer between stop and the vertical stabilizer rear spar on the left side.  This helps establish the cant in the vertical stabilizer.

The ruler indicates the fuselage centerline.  You can see how the forward end is shifted left (we're looking aft in this picture).  This counteracts the natural left turning tendency of the aircraft.

After triple checking all of the measurements, I drilled the splice plate to both the horizontal and vertical stabilizer front spars,

I then drilled the lower vertical stabilizer rear spar to the tailwheel attach bracket and then installed the rudder.  There is a little interference with the vertical stabilizer top fairing.  I'll have to trim it back slightly.  It's really late though, so I disassembled everything and put the plane back in the garage.

I hooked up the canopy switch wires and verified the annunciator light illuminated appropriately.

I attached the ground wire to one of the canopy latch pivot block mounting bolts on the back side of the bulkhead.

I also installed a connector and some zip-tie bases in the roll bar support channel and hooked up the cabin light.

Finally, in preparation for mounting the wings this Friday, I fabricated the flap pushrods.  I cut the tubes from some 5/16" stock with 0.058" wall thickness and then drilled/tapped the ends for the 1/4"-28 bearings.

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