Lighting, Pulse Is OK - But Wig Wag Is Better!

Having an electronics background, it was bugging me not having a schematic drawing to use as reference once the electrical connector wiring  begins … especially since there will be some small changes to the electrical system. It is nice to see the "big picture" sometimes.  Van’s has a schematic drawing online for the builder to download which is drawn in such a fashion, in order to read any of the labeling, it requires zooming so far you lose all prospective. Trying to trace a wire is … well “fun”. Not!

Decided to have the entire schematic drawing printed out on 4 x 3 foot paper and it was still tough to read the labeling, so had the drawing divided into four quadrants and each of those printed onto 4 x 3 foot sheets. Honestly, the schematic would need to be about the size of the side of a cargo van as to be easily read.

                The whole schematic is now on one 4x3 foot sheet … still difficult to read the labeling but it is legible.

The lower quadrant of the above schematic printed on a 4x3 foot sheet … at least now it’s easier to read the labeling.

Lighting - pulse is OK, but wig wag is better!
Although not much is being accomplished in the shop, behind the scenes there has been a flurry of activity. The decision was made to order a second landing light so wig wag lighting would be possible. One thing is clear to me, a plane flying in the pattern with wig wag wing lighting simply commands attention!

Those familiar with the RV-12 lighting kit know, as shipped from Van’s, the lighting kit only has one landing light which is installed in the right wing. Basically, the reason for this is not to over tax the somewhat anemic electrical system of the Rotax engine. The landing light, which is manufactured by AeroLEDs, has the provisions for both steady light and a pulse mode which Van's incorporates. The current draw is 2.6 amps when the landing light is on. In a two light instillation, the pulse mode can become a wig wag mode. For wig wag operation, one light becomes a master and a wire is run from that light's master output to the slave input on the second light which enables wig wag operation. That got me thinking, if one were to add a second light on the left wing but only use the wig wag mode, the total current should still be 2.6 amps … because only one light is illuminated at a time.   A call to AeroLEDs technical support confirmed my suspicions, so an additional light and mounting hardware was ordered from Van’s Aircraft on Monday.

I still plan on running a power lead to the left landing light’s steady on, but will not connect it to the switch on the panel. But it will be there should there be an improvement in the electrical system in the future which allows for more power. To be honest, I’m not planning on flying at night anyway, so doubt the landing light will ever be used as such. But using the wig wag mode of those bright lights … you bet! See and be seen!.

The decision to add an additional light on the left wing created yet another grommet issue … the 437-4 grommets I just ordered proved to be a little tight with the addition of the second shielded cable for the landing light along with the Tygon tubing, so an order was placed through Mouser for 437-5 grommets. These grommets use the same size .437” mounting hole as the 437-4 grommet but have a wire hole of .312” as opposed to .270”. The new grommets just got here today so will see how well they work out tomorrow … suspect there will be plenty of room now and the good news is the new grommets still only require the hole in the ribs being enlarged to the next size up on the step drill from the original hole size.

Labeling Wing Wiring

Not wanting to waste a 60 degree winter day, a little forward progress was made in the shop. The first chore was attaching the mounting standoffs for the electrical connections onto the inboard rib. After playing with electrical, decided it would be a good idea to primer all of the machine countersinks in the spar … so did so with the PTI zinc chromate primer.

While attaching the standoffs onto the left wing, it quickly became evident my stubby Philips head screwdriver was too long for getting onto the mounting screws (plus it required a smaller Philips tip than I had). This required holding the head of the screw with long nose pliers while tightening the standoff. I looked at the rib and realized this would have been easily avoided had the standoffs been attached prior to riveting the rib in place, so I immediately attached the standoffs onto the inboard rib for the right wing.

Builder Tip: I would suggest screwing the standoffs for the electrical connectors onto the left and right wing’s inboard ribs prior to riveting the ribs in place it will make life easier.


The larger snap bushings on order should be here Tuesday or Wednesday at the latest, so even though wires can’t be run through the ribs yet, did make a couple of ground wires and prepped some of ends for the left wing wiring.

One of the play toys procured early on was a Dymo Rhino label machine, which has been used quite a bit making labels to identify small parts in storage containers. One of the reasons it was purchased was because it can also label heat-shrink tubing. Today the first labels were made and have to say, it works great.

The first printed 1/4 inch heat-shrink tubing on a wire to illustrate the size prior to shrinking is sitting on the bottom of the label maker. I was testing the size of the smallest print … very readable.

Mounting Stall Warning Assembly With Socket Head Screws

The socket head screws ordered for securing the stall warning assembly came, so decided to get into the shop for a few minutes and make the change. The size of the Allen head socket in the new screw is 9/64” … the Allen wrench I used is rather long which may be problematic when the wing is assembled. Fortunately, I have an Allen set which attaches to a small ratchet wrench down at the Southern Outpost in case further tweaking is deemed necessary during flight testing.

                                 Stall warning assembly after changing the Philips mounting screws to socket head screws … 
                                 9/64” wrench in lower screw shows accessibility, it clears the keeper plate (barely).


Feel I will come to appreciate this small modification the first time I find myself lying on my back, under the wing, trying to adjust the stall warning assembly so the stall warning alarm sounds at the correct airspeed.

Snap Bushing Mania

Now that the shielded wire for the navigation/strobe wiring has arrived, wanted to see how well the snap bushings accommodated the shielded wire and the Tygon tubing for the AOA plumbing. The verdict … just fine if you never plan on replacing either the tubing or the wire.  There is just barely enough room in the snap bushings provided by Vans to accommodate everything without crushing or deforming the tubing. That said, because the tubing has a relatively “soft” outer surface it doesn’t slide across the insulation of the shielded wire easily once it is in place. I’m afraid should the tubing ever need to be replaced or another wire run, the friction would be so great, it would be very difficult.

                                   Shielded cable and Tygon tubing inside the SB 375-4 snap bushing from Heyco
                                   included in the kit. Everything fits … but it is very snug as can be seen here.


Decided to up the size of the snap bushing to a Heyco SB 437-4 which has an internal hole diameter only .020 larger. Now 20 thousands doesn’t sound like much, but it makes all the difference because now there is just enough extra room to allow the Tygon tubing to slide across the shielded wire with far less friction.

                                             Shielded cable and Tygon tubing inside a Heyco SB 437-4 snap bushing. 
                                             The small amount of extra room contributes to very little binding.


Fortunately, there is no need to change all the snap bushings only the inboard eight bushings on the left wing where there is Tygon tubing and the shielded navigation /strobe wiring running together. Unfortunately, the holes for the bushings will require being enlarged to the next size larger using the step drill bit.

Modifying Stall Warning Assembly Mounting Screws

While following the adjustment procedure Van’s has in their instructions for initial setup of the stall warning micro-switch& vane, I discovered the potential for a nightmare later down the road. The stall warning assembly uses two #8 8-32 Philips head screws to secure the assembly to the two nutplates riveted onto the W-1208-R nose rib. (For those not familiar with nut plates, in a nut shell they are a threaded plate that is riveted to a structure which you don’t have access to the backside of to allow for a wrench and nut, as would be the norm.

The threads on the nut plate are purposely squished a little so a screw can’t back out on its own. However, this requires extra effort when screwing a screw into a nut plate, not to mention requiring extra pressure on the screwdriver to prevent the Philips screw head from stripping.

Even with the W-1202-L skin flexed up to allow for fair access, it was not easy to screw in the two Philips mounting screws securing the stall warning assembly. (OK, admittedly it was quite cold in the shop and my hands are used to 70 degree California winter temperatures, so a small task like this seems like a much larger chore). Frankly, once the wing is fully assembled, I can’t fathom the difficulty involved to make adjustments to the assembly through a tiny inspection hole. The odds of the switch being set perfectly at this point is rather slim, so adjustments are very likely … plus to add to the difficulty, it appears as though it will also require using the left hand if the wing is on the RV-12. Should one of the Philips screws become stripped, and that would be soooo easy, it would be a colossal bummer!

The dollar bill is placed adjacent to the inspection portal to illustrate what “fun” it will be later to make adjustments to the stall warning assembly which is nestled just aft of the leading edge of the wing where there is little room.


In an effort to alleviate the possibility for a screw head becoming stripped and to make adjustments easier, I’ve decided to use socket head cap screws (Allen head) to secure the stall warning assembly, as opposed to using the #8 Philips screws. I feel it will be much easier in such a cramped location with limited visibility to just insert an Allen wrench into the screw head and have a positive fit, substantially reducing the potential for head stripping all together. The socket head cap screws are now on order. Fortunately, the shielded wire I was waiting for was delivered this evening so forward progress on the left wing’s wiring can resume.

Test Fitting Of Stall Warning Assembly

Not much time was spent in the cold shop today but did accomplish the test fitting of the stall warning assembly on the left wing. The instructions have the builder make a 5” ground wire which is attached onto one of the stall warning assembly’s mounting screws. The assembly is then mounted onto the W-1208-R nose rib that has two plate nuts on it.

After the stall warning assembly is mounted onto the rib, the W-1202-L wing skin that has the slot on the leading edge for the stall warning vane is carefully set in place and Clecoed to test the fit. The vane should move freely and not bind on the sides of the slot in the skin. Guess I got lucky because there is no binding and the vane is centered.

                                           Stall warning assembly and ground wire attached onto the W-1208-R rib
                                           that has the two nut plates. Photo taken prior to micro-switch adjustment.

                              Close up of the stall warning vane sticking through the slot in the W-1202-L wing skin.

This view shows how far the stall warning vane protrudes from the leading edge of the wing and also its slight downward angle. It’s been reported the protruding vane has quite an appetite for the pants and legs of unsuspecting souls.

Before working on the RV-12 today, I was filling the tires of DOG Aviation’s support vehicles (without gloves) so by the time the stall warning assembly was mounted and the W-1202-L skin set in place, my hands were chilled to the bone so will move onto adjusting the micro-switch/vane assembly during the next work session after the hands thaw out.

Happy New Years!!

New Years Eve was spent rearranging the shop a little by putting away a folding table which was used as a catch all table. Now the snow blower can be moved from the middle of the shop allowing access into the large box that contains the wing skins. The left wing’s middle skin is needed for testing the fit where the stall warning micro-switch/vane assembly passes through a slot in the leading edge of the skin.

Wanting to get the New Year started off on the right foot by making some forward progress on the RV-12, assembled the stall warning micro-switch/vane assembly per the instructions.  Winter in the shop is not fun … trying to assemble all the small hardware with gloves on was impossible but doing it with numb fingers was only marginally better. Should have fired up the heaters but figured it was hardly worth it for the small amount of time I planned on spending in the shop … although my hands and feet disagreed with that assessment.

                                           The assembled stall warning sub assembly ready to be mounted onto
                                           the W-1208 nose rib previously prepped with mounting plate nuts.

The wiring tools ordered by the DOG Aviation procurement department came in New Years Eve and consists of an automatic wire stripper along with a ratcheting crimping tool made by Tool Aid with seven changeable dies ... the part number of the Tool Aid kit is #18960. The crimping tool will crimp a host of connectors …. . both standard sizes of open barrel Molex  connector pins, standard and miniature insulated and non-insulated ring and spade crimps, Weatherpack terminals, coax cable, even spark plug connectors. Return from the future: Subsequently another die set #18937 was needed for the small .063 Molex open barrel connectors and open barrel connector pins for for tiny wire.

                                Wire strippers and Tool Aid ratcheting crimping tool with seven dies for various wire terminals.

The last item needed before riveting the skins onto the rib skeleton is the shielded cable for the strobe lights … which should be here Friday according to the shippers tracking info. After that the only hold up should be my tolerances to working in the cold holding tools that feel like blocks of ice.