Repairman Certificate Granted By FAA

As frequent readers of the DOG Aviation Blog may have noticed, the baffle project has stalled out a bit ... I hit a roadblock while preparing to delve into the wiring. It is not going to derail the instillation but there will be a parts delay. I’ll post more about that in a separate post in the next day or two.


One of the things I had been putting off through the winter months was making a trip to the FAA’s FSDO (Flight Standards District Office) to obtain a repairman certificate. The repairman certificate allows the annual condition inspections required by the FAA to be performed by me. Often times the repairman certificate can be applied for at the time of the airworthiness inspection. However, in my area, the FAA has split the duties between MIDO (Manufacturing Inspection District Office) and FSDO …. where MIDO inspects newly constructed aircraft and issues the airworthiness certificate and the FSDO issues the repairman certificate.


A huge benefit of building an experimental airplane (special airworthiness certificate) versus purchasing a certificated airplane such as a Piper or Cessna (standard airworthiness certificate) is that the FAA allows the builder of an experimental airplane to perform the mandated annual condition inspections … but ONLY IF the builder applies for the repairman certificate and can prove 51% or more of the work constructing the aircraft was done by the builder. Owners of standard airworthiness certificated aircraft (such as a Piper or Cessna, ect.) are not allowed to perform the FAA mandated annual condition inspection … they MUST use a FAA licensed aircraft inspector to perform the annual condition inspection.


For the benefit of the non-aviation reader viewing the DOG Aviation Blog, here is a quick synopsis of the rules for experimental amateur built aircraft (E-AB). During the certification process, the builder MUST PROVE to the FAA beyond a shadow of a doubt that over 51% of the airplane was built by the builder. The 51% rule applies to all E-AB airplanes … which the FAA allows to be constructed by individuals as a “recreational and educational experience”. The reasoning behind the 51% rule for E-AB aircraft is so aircraft kits can’t be professionally assembled as a cottage industry then sold to the general public and also so individuals can’t pay to have others assemble the aircraft for them. Upon receiving the special airworthiness certificate for an E-AB aircraft, the builder can then apply for a repairman certificate which allows the builder to perform the annual condition inspections required by the FAA … but ONLY on the specific experimental aircraft the builder constructed. Also worthy of noting, at no time can a person other than the original builder of an E-AB aircraft apply for a repairman certificate for that experimental aircraft.


One of the many reasons for establishing the DOG Aviation Blog was to have a method of documenting the building activities so the FAA could look at the Blog and see many hundreds of photos with me in them performing various stages of assembly on the RV-12 accompanied with an in depth write-up of the building process. This proved useful during the certification process and once again last week when I applied for a repairman certificate. So armed with the DOG Aviation Blog, my builder’s log book, a binder with hundreds of photos with me in each photo and the 8610-2 application form for the repairman certificate … a trip was made to the FSDO to yet again prove to the FAA that over 51% of the RV-12’s construction was done by myself.


During the initial phone conversation with the FAA to schedule the interview, we discussed the documentation the inspector expected me to provide. At that time, I mentioned the DOG Aviation Blog and passed along the WEB address of the Blog so the inspector could peruse the Blog prior to my appointment. The day of the appointment I was met by two FAA employees ... while walking into the conference room, I casually asked if they had taken a look at the DOG Aviation Blog and was told “Yes! and there is no question about it, you built the airplane”. So my tip to fellow builders would be: Consider establishing an online Blog or builder log containing plenty of photos showing you performing the various phases of construction and parts fabrication. Of course, it is also in the builder’s best interest to keep a hand written builder log for the inspectors to peruse. My hand written builder log is brief,  just showing the date, which parts were assembled or prepared during each work session and time spent working, whereas, the DOG Aviation Blog contains a very detailed synopsis of each work session.


Since there were no doubts about my qualifying for the repairman certificate under the 51% rule, the interview became more of pleasant meeting to verify that the paperwork was filled out correctly and to discuss the quality of Van’s plans and components. Because the inspectors had taken a good look at the DOG Aviation Blog, not a lot of time was spent looking at the hand written builder log. However, the hundreds of photos I brought were looked at with great interest…   as it turns out, one of the gentleman is giving some serious thought to building a Van’s airplane. So he was very interested in the assembly process/instructions and the various models Van’s manufactures.


An hour later, I left the FSDO with a temporary repairmen certificate in hand. As it turned out the day I visited the FSDO was also my birthday, so receiving the coveted repairmen certificate was one of the best birthday presents ever.

Another monumental day at DOG Aviation and good reason to smile. In my hand is a temporary issuance of the coveted repairman certificate. The repairman certificate will allow me to perform the annual condition inspections on the DOG Aviation RV-12.

Installing a “Bender Baffle” Piggybacked With Regulator Relocation Mod - Part Five

Decided to initially drill all the holes in the baffle using a #19 drill bit so  #8 hardware can be used to mount the baffle plate onto the shafts … however, when measuring for the holes, I used minimum edge clearances recommended for #10 holes just in case a switch is made to #10 hardware. As mentioned in the previous post, all the holes in the shafts were drilled to #40 so the baffle could be secured onto the shafts using Clecos …. but that didn’t work out because the Cleco pliers did not have enough clearance to install the Clecos with the baffle in place. Ultimately, a long rivet was used in the first hole drilled to hold the baffle position while a hole in the upper shaft was marked for drilling by hand spinning a drill bit in the hole. After drilling one of the holes in the baffle pate for the upper shaft, the assembly was put together using two rivets to hold positioning so the remaining four holes could be marked using the drill bit.

My fingers are pointing to the two rivets holding the baffle’s position so the remaining holes can be marked for drilling.

As the two rivets were holding the baffle plate’s position the remaining four holes needing drilling were marked by inserting a drill bit into the pre-drilled holes in the shafts and spun by hand. Marking one of the holes in the lower shaft by spinning a drill bit in the hole to make marks on the baffle plate.


Once the remaining holes were marked, the hole locations were center punched and drilled using a tiny drill bit to make a lead hole followed by a #40 drill bit. Next the assembly was secured with Clecos and match drilled on the drill press stepping up to a to a final size of #19 for #8 hardware. If at a later point it is deemed necessary to go with #10 screws, there is still enough material to do so.

The baffle plate secured onto the upper and lower shafts with Clecos ready for match drilling to final size. Note the upper shaft is still quite long, this will be shortened when the exact position for the pivot arm is determined.

Using the drill press to match drill the baffle plate to the shafts with a #30 drill bit … during the next pass went to #19.

After drilling the holes with a #19 drill bit for #8 hardware, the assembly was installed in the air duct for a trial fit using some temporary hardware store #8-32 screws and nuts. All the parts for the baffle fit nicely together and the baffle has a good range of motion.

Test fitting of the baffle assembly in the air duct … baffle in the open position ... looking good.

Baffle closed …. looking good but as one can see, there is very little clearance between the edges of the baffle plate and the fiberglass.


Even when the baffle is in the closed position, there needs to be some airflow … so it is suggested that when the baffle is in the closed position, there should be approximately 1/8" to 1/4" of clearance between the baffle and the air duct. Decided to go with 1/8" because the bushing flange and washer make the gaps at the top and bottom just under 1/4" anyway ... so figure if necessary, it is easier to remove material than put it back on. To mark the 1/8" gap on the baffle plate, a scrap piece of 1/8" aluminum was placed against the fiberglass sides and used to mark the outer edges of the baffle plate for trimming. The baffle plate was then removed and trimmed on the band saw.

Using a scrap piece of 1/8" aluminum to mark the baffle for final trimming to create a 1/8" gap between the fiberglass and the baffle. The red cut line can be seen on both sides of the baffle plate.


Looking closely at the next photo one can see the results of the test fitting after trimming the excess material off the baffle plate. Now when the baffle is in the closed position, there is a 1/8" gap between the fiberglass and baffle plate.

 Now when the baffle is in the closed position, there is a 1/8" gap between the fiberglass air duct sides and baffle plate.

Decided this was a good place to stop for the work session. Next up will be working out the details on installing the regulator onto the baffle plate and working out the details necessary to control the baffle’s movement from inside the cockpit.

Installing a “Bender Baffle” Piggybacked With Regulator Relocation Mod - Part Four

This work session began by using the cardboard baffle template to cut a piece of .090" aluminum for the baffle. Because the baffle will have a significant amount of wind pressure applied to it during flight when in the closed position, felt it needed to be of a thicker material even though mounting the voltage regulator onto the baffle will add a significant amount of stiffness. Decided to go with .090" aluminum which is also what Bender used for his original design. The baffle is still slightly larger than necessary, so it will need a little material removed from all the edges after the positioning  is finalized.

A piece of .090" aluminum was marked using the cardboard template then cut to size. A little additional trimming will be required all around once the final positioning for the baffle is established.


Now that the bushings are bonded in place and the baffle plate cut, moved on to making the two shafts that will slide into the bushings and secure the baffle. Felt it best to create a flat spot on each shaft for mounting the baffle … so decided on making a 3" long flat spot. This was accomplished by removing enough material to make a flat area for the aluminum baffle plate to mate onto. I think 3” is enough surface area for three holes and also keeps the holes within minimum hole edge distances (two times the hole size measured to the center of the hole based on #10 hardware). Now is the time it would be nice to have a milling machine … I see a lot of sanding/filing/measuring/repeat in my future.


The process for making the shafts began by using the band saw to remove a 3" thin strip of metal from the aluminum rod to create the beginnings of a flat spot. Next a belt sander was turned upside down and clamped onto the workbench and used to smooth down the flat spot enough to remove the scores left from the band saw. This was somewhat dangerous and NOT a method I would recommend …. but you work with the tools you have. I would caution about trying to use the belt sander to get to the final size ...  it is very easy to begin rounding the edges, so I just used it to get the beginnings of a smooth 3" long flat. To get to the finished size, required A LOT of hand filing and sanding with a sanding block until the final thickness of 13/32" was achieved … so basically 3/32" was removed from the rod. Oh, also used flat back riveting plate with sticky sandpaper on it to get the flat spot as close to perfect as possible. Seemingly, removing 3/32" leaves enough of a flat spot for good support for the baffle plate, yet leaves the shaft thick enough to support the three mounting holes that will need to be drilled.

Using the belt sander to begin smoothing the roughness left from the band saw.

After a little hand filing and use of a sanding block and a flat back riveting plate covered with sandpaper, a uniform final thickness of 13/23" was achieved.

The finished flat spot ready for drilling the mounting holes. As one can see, the shaft thickness at the flat spot measures 13/23". One down, one to go.


After completing the 3" flat spots on both shafts, the three mounting holes for each shaft were marked and drilled to #40. The actual final assembly will begin with establishing the correct positioning of the baffle while in the closed position and drilling one of the mounting holes in the baffle. Because brass washers will be used between the bushings and baffle, a little excess material will need to be removed from both ends of the baffle to establish the correct spacing.

A brass washer with a 1/2" hole in it will be used between the baffle and the bushings.

The goal was to first establish the fit of the bottom shaft first … then strive for a snug fit to the upper bushing with a minimum amount of up and down play by trimming the upper edge of the baffle to achieve a non-binding fit to the upper washer/bushing that just has a very small amount of vertical movement. This is the reason why the cardboard baffle template was left a little long … it insures the capability of being able to make a snug fit. Prior to cutting the lower shaft to length, some measurements were made based on 3" for the flat spot, 3/32" for the brass washer, 1/2" bearing depth plus 1/8" + excess at the bottom of the bearing … so the lower bushing shaft was cut to a length of 3 24/32".

Completed lower bushing shaft with #40 holes drilled … The #40 holes will be enlarged later to accommodate the mounting hardware either #10 or #8 ... haven’t decided just yet.


My game plan did not work quite as envisioned: My initial thought behind only drilling the holes to #40 at first was … mark the first hole to be drilled into the baffle by inserting a #40 drill bit into one of the holes in the lower shaft then spin the drill bit by hand to leave a mark on the baffle so a #40 hole can be drilled in the baffle. Once the first hole is drilled, the plan was to secure the baffle onto the shaft using a stubby #40 Cleco to hold positioning so the remaining holes in both the upper and lower shafts could be marked, then drilled in the baffle. The roadblock I discovered was due to the shape (angle and length) of the handles on the Cleco pliers …. the handles on the Cleco pliers hit the side of the cowling long before allowing even a stubby Cleco to be inserted into the hole in the baffle. Ultimately, a long #40 rivet was used to hold the alignment of the baffle on the lower shaft.

Baffle plate in place with the upper hole on the lower shaft drilled into the baffle. Looking good so far it is starting to come together and look like a baffle assembly. Due to the clearance issues mentioned above, used a long #40 rivet at the location my finger is point towards as a pin to hold positioning so the remaining holes can be marked ... it can be seen if one looks closely at the photo.


Before drilling the holes for the upper shaft, the top edge of the baffle will require a little more trimming to accommodate the brass washer.  This seemed like a good place to quit for the evening.

Installing a “Bender Baffle” Piggybacked With Regulator Relocation Mod - Part Three

This post will cover mounting a terminal barrier block which will be used as an interface between the existing RV-12 wiring harness and the wiring harness that will run to the Silent Hektik F-4118 regulator mounted inside the lower cowl on the baffle plate.


RV-12 builders planning to relocate the voltage regulator inside the lower cowl's air duct please take note of the following regarding the use of quick disconnect connectors for the wiring:


The wiring connector dilemma: Mounting the regulator on the baffle plate inside the air duct creates a wiring challenge because the wiring will need to be disconnected every time the lower cowl is removed. On a new aircraft like mine, removing the lower cowl will occur more frequently during the initial flight testing and then taper off to a few times a year for oil changes and condition inspections.  This, in and of itself, creates some issues. What’s the big deal you may be asking yourself? Just use a connector that has pins rated for the maximum current the Rotax 912 can produce (approximately 18 amps). Well, that’s easier said than done and here’s why ....


Because the regulator is a high current device, ANY connector utilized needs to have pins rated for high currents. Sticky wicket #1: … sure there are plenty of connector styles available on the market but ones with pins rated 15 – 20 amps are quite limited. Sticky wicket #2 and the main reason I suggest builders DO NOT use any quick disconnects for the regulator wiring is: ... if one looks deeper into the application data sheets for the connectors, unfortunately, you will quickly discover all the connectors that have pins rated for high current have a VERY LIMITED INSERTION LIFE CYCLE, with the majority of connectors being under 10 insertions. This means that after removing the cowling just 10 times (some were as low as 6) the pins in the connector would need to be replaced in order to remain within the max current specification the connector’s pins are rated at. The best connector I could find is a very popular expensive military connector rated at 20 amps per pin and that only has a life span of 25 insertions. Because of the limited insertion ratings of the connectors, I decided it best to forget about using a quick disconnect connector altogether and would suggest others do so as well …  at the currents we are talking about, a little increase in resistance at the connector pin can begin to create a considerable amount of heat at the connection leading to oxidation which increases the resistance generating more heat etc.,  to the point of melting insulation. This application requires a continuous low resistance connection … period.


My solution will be to use a very high quality screw-down terminal block rated for high temperature environments. Suggest others doing this not use the lesser quality plastic terminal blocks … you want the good stuff for this application. I chose a Cinch 6-142 phenolic terminal barrier block which is a 6 circuit barrier block rated at 30 amps per circuit and able to withstand temperatures to 300 degrees. Astute RV-12 builders may be asking themselves why use a 6 circuit barrier block when only 5 wires are run to the Ducati regulator? The answer is both the Ducati and Silent Hektik F-4118 regulators obtain their ground from the case being bolted to the aircraft airframe ... so this necessitates running a sixth wire that will be bolted to the regulator's case to supply the necessary ground for the regulator. So a ground wire will be run from the ground block on the DOG Aviation RV-12's firewall to the sixth terminal in the Cinch terminal block to provide the necessary ground.

The Cinch 6-142 phenolic terminal barrier block.

Decided a good and easy location to mount the Cinch terminal barrier block would be on the two rudder pedal studs that protrude the nutplates on the RV-12’s firewall shelf. Two 3/4" coupler nuts were screwed onto the protruding studs and blue Loctite was placed on the threads to prevent the nuts from coming loose.

Plenty of threads to protruding the nutplates to install coupler nuts to use as a mounting point for the Cinch 6-142 terminal barrier block.

3/4" long stainless coupler nuts with 10-32 threads were screwed onto the portion of the rudder pedal mounting bolts that protrude the nutplates. Loctite 242 (blue) was placed onto the threads prior to installing the coupler nuts.


Next a small mounting plate was fabricated with an offset to mount the Cinch terminal block. The small offset was used so there would be easy access for a screwdriver to remove the wires, The offset is not really necessary …. however, without the offset the coolant hose blocks easy access to some of the screws and would require the use of a stubby screwdriver. The Cinch 6-142 terminal block has an exposed bottom … meaning if one were to look up from the bottom one can see the metal inside. Although not necessary, I decided to cut a thin strip of Neoprene and use it as a sealing gasket under the connector block.


The Cinch terminal blocks can use various mounting accessories. The DOG Aviation R & D department decided on using fast on connectors the side of the connector block that interfaces with the existing wiring which normally connects to the Ducati regulator. The beauty of this is ... if I decide to leave the Ducati regulator mounted on the firewall shelf as a spare, should the Silent Hektik regulator fail, the wires can easily be unplugged from the Cinch terminal block and moved back to the Ducati regulator. The wiring harness going to the regulator inside the lower cowl will have #8 ring terminals terminating at the Cinch terminal barrier block. This will allow the wires to be easily disconnected whenever the lower cowl needs to be removed. Sure it will be a bit of a hassle removing six screws every time the lower cowl needs to be removed, but the screw down terminal block will provide a very solid and low resistance interface connection between the existing wiring and the extension wiring to the regulator inside the lower cowl's air duct.

Fabricated mounting plate and the Cinch 6-142 terminal barrier block attached to the rudder petal bolt studs via two stainless 3/4" 10-32 coupler nuts. The Ducati regulator can be seen in the background and there is more than enough wire to easily reach the Cinch terminal barrier block.


Looking at the above photo, one can see that there are two 3/8" coupler nuts on the terminal block these will support a cover plate made from high temperature plastic that will cover the wires and connections when the final wiring is completed.

Installing a “Bender Baffle” Piggybacked With Regulator Relocation Mod - Part Two

Have finally gotten around to continuing work on the modified “Bender baffle” and during a few small work sessions, worked out the final positioning for the bushings ... this was after changing my mind a few times in an effort to maximize the full open position for the baffle. In the previous post, there is a photo of a box representing the size of the voltage regulator tapped onto to the cardboard baffle. This was used to see if there is enough clearance to mount the regulator on the baffle and clear the cowl throughout the baffle’s range of motion.

As can be seen, the bushing location has changed several times … this is the final location.

When playing around with the baffle’s position decided to move the baffle as far forward as practical so made another cardboard template because the curve on the cowl was just a little different at the new location.

New cardboard baffle made with a slightly different curve to match the new mounting location.

A dowel rod was wrapped with painters tape and slipped into the upside-down lower bushing ... the masking tape was used on the dowel rod to make a very tight fit with the bushing. Next the cardboard baffle was taped onto the dowel rod to verify the clearances ...  the cardboard baffle was swung open and closed with the cardboard regulator mockup in place and seemingly, the regulator mockup clears the side of the cowl nicely.

Baffle in closed position.

Baffle in open position.

Now that the lower pivot point has been determined, it is time to punch a hole for the bushing. The position for the bushing was traced onto the blue masking tape. To find the center of the hole for drilling, a 1/2" pilot point drill bit was slipped into the bushing and spun a little to create a center point mark that was used to begin the drilling process. A tiny lead hole was drilled followed by progressively larger bits until a step drill could be used. Because of the limited room under the air duct due to the curve of the cowl, the step drill could not be used to go directly to the final size so I stopped at 1/2". Next a Dremel tool with a sanding drum was used to take the hole close to the final size followed by a little hand sanding so a nice tight bushing fit could be achieved.

A 1/2" pilot point drill bit was used to find the center point for drilling the mounting hole for the bushing.

After drilling the 1/2"  hole for the bushing, a scrap piece of 1/2" rod was placed in the bushing to hold position so the bushing’s diameter could be traced so the final 5/8" hole could be made.

Using a Dremel tool outfitted with a small sanding drum to get close to final hole size of 5/8" for the bushing.

Tweaking the hole by hand to achieve a nice tight bushing fit.

Because the air duct’s fiberglass is fairly thin, decided it would be best to add a doubler plate to help support the added mass of the voltage regulator … so cut a piece of .032 aluminum and drilled a 5/8" hole in it for the bushing to seat into. I came to this conclusion while trying to mark the upper bushing location and discovered I could not get the exact same location twice. This was caused, as I later discovered, by pushing down on the bushing to prevent it from moving  while attempting to mark the upper bushing location. By pressing down on the lower bushing, it caused the fiberglass air duct to flex a little .... a little flex at the lower bushing end was creating a lot of movement 14" away at the other end of the dowel rod.

The .032 aluminum doubler plate cut and ready for final instillation this should eliminate the flex and provide good support for the bushing.

Was planning on just riveting the doubler plate onto the air duct, but finally decided it would be best to bond it onto the air duct with a mixture of resin and flox so it would be really solid without any flex. The bottom of the doubler was sanded to scuff it up a bit along with the fiberglass it will mate onto ...then rivet holes were drilled. To prevent the fiberglass from being stressed while riveting, some #4 brass washers were procured to slip onto the rivet so the shop head could form on the washer as opposed to crushing the fiberglass.

Drilled doubler plate ready for a little resin/flox mixture and riveting.

Completed lower bushing instillation. A thin coating of flox is bonding the doubler to the air duct. Not in the photo ... small #4 brass washers were slipped onto the shafts of the rivets on the underside of the air duct so the shop heads would form on the washers as opposed to crushing the thin fiberglass.


Now need to complete the same operation for the upper bushing.  After the flox mixture cures, the upper bearing location will be marked and drilled.