Doing Service Bulletin 18-02-02 Part 2 of 3

The part 1 post for Van’s Service Bulletin 18-02-02 covered the steps necessary to perform the needed modifications to the WD-1207 & WD-1208 stabilator horns. Here in part 2, the steps necessary to prepare the stabilator for the new hinge brackets will be covered.


The hinge bracket work begins by removing the existing HS-1213A & HS-1213B hinge brackets along with the HS-1210 hinge stops from the stabilator assembly. The removed HS-1213A & HS-1213B hinge brackets are relegated to the scrap box … but the HS-1210 hinge stops and all hardware are to be saved for reuse (I’ll be replacing all the bolts that screw into nutplates during final assembly).

The existing HS-1213A & HS-1213B hinge brackets along with the HS-1210 hinge stops are to be removed from the stabilator assembly … save the four round HS-1210 hinge stops and discard all the HS-1213A&B hinge brackets.

Hinge bracket assembly on the right has been removed and will be discarded … the one on the left is next on the hit list.


At this point some rivets need to be removed and new rivet holes drilled. Because of limited room in the hangar the majority of the following photos in this post will show the work performed on the hinge brackets for the left side of the stabilator … keep in mind, the same work also needs to be performed for the right hinge bracket as well.


Once the old hinge brackets are removed, the next step involves removing six rivets (three on each side) common to the HS-1202 forward spar and each of the HS-1212 ribs inside the stabilator’s spar box. For most all builders/owners these rivets will be pop rivets so the mandrel is driven out and the rivets are drilled out. However, as can be seen in the photo below, the DOG Aviation RV-12 was constructed using solid rivets at this location which complicates matters a tad bit.

The pink arrows point to the three rivets on the left side that need to be drilled out …. For most all RV-12’s these three rivets will be pop rivets and NOT the solid rivets shown here in the photo. These three rivets also need to be removed from the right side as well.


Unfortunately, my work was made just a little more difficult in that solid rivets were used at this location during assembly of the DOG Aviation RV-12. Normally, when removing a solid AN470AD4 rivet, the center of the rivet is center-punched then a small lead hole is drilled to act as a guide for the larger #30 drill bit.  There was plenty of room to drill the center rivet to #50 then final drill to #30 to remove the rivet. However, did not have the room necessary to drill the other two rivets close to the stabilator’s skin because the chuck on the drill would not clear the skin. If there is not room to drill a lead hole, it makes getting the #30 drill bit perfectly centered and keeping it that way while drilling extremely difficult to say the least.


Fortunately for me, earlier in the build when completing the Service Bulletin to upgrade the F-1206F bearing bracket, I had a special tool machined for me by Mike at Cleaveland Aircraft Tool that sits over the head of an AN470AD4 rivet. The tool has a hole down the center for a drill bit and assures perfectly centered drilling of an AN470AD4 rivet head … it works great! I had two made, one for drilling #50 lead holes and one for drilling #30 holes.

The two custom made drilling guides assure a perfectly drilled AN470AD4 rivet … one guide is used to drill #50 lead holes and the other for drilling #30 holes.

The drilling guide with a #30 drill bit inserted … this setup drills through the center of an AN470AD4 rivet every time.


When using the drill guides, it is necessary to stop often to clean the drill bit’s flutes because there is nowhere for the shavings to go so they become packed in the flutes. So using the drill guide takes a little extra time and some patience … but the end result is a perfectly drilled rivet without enlarging the existing rivet hole. Thus far, I’ve had superb results every time I’ve used the drill guides to remove a rivet. After the three rivets on each side were drilled out it was possible to retrieve the six tails from inside the spar box by lifting the stabilator up and moving it around until the all the rivets fell through the holes for the counter weight. Takes a little patience and perseverance but the rivets are retrievable.

Using the drill guide and a 12” #30 drill bit to remove a rivet close to the stabilator skin.

At this point, I deviated slightly from the plans and stepped ahead a bit because it was one of the last days with fairly warm temperatures and I wanted to prime those areas on the stabilator skin that will be covered by the HS-01231C stabilator hinge gussets. Two rivets need to be removed from the stabilator prior fitting each one of the four HS-01231C stabilator hinge gussets. After removing the two rivets each hinge gusset will cover, the HS-01231C stabilator gussets were attached with Clecos so tape could be placed around the edges of the gussets to reveal the area on the stabilator skin that needs to be primed. Now the stabilator needs to be flipped over so the same four rivets on the other side can be removed … and that side prepared for priming.

My fingers are pointing towards the two HS-01231C stabilator hinge gussets sitting in position on the stabilator. Looking closely, one can see the heads of the two pop rivets under the gussets that need to be removed prior to installing the gussets.

The four pink arrows are pointing to the four pop rivets that need to be removed on this side of the stabilator prior to installing the two HS-01231C stabilator hinge gussets. The same four rivets also need to be removed on the other side of the stabilator for the two stabilator hinge gussets that will be attached to that side.

The HS-01231C stabilator hinge gussets temporarily secured in place with Clecos so tape can mark the footprint for priming.

Primed area on the stabilator skin where the HS-01231C stabilator hinge gussets will sit. This is the first light coat … it was followed by another light coat topped with a heaver coat. After the primer dried the stabilator was flipped over so the other side could be primed as well. (Also of note: Sharp eyes may have noticed the dimple in the primed area which resulted from removing the flush rivet that was there … the dimple will be filled with the head from drilled out flush so there will be no voids under the HS-01231C gusset).
After the primer was left to dry overnight, it was time to jump back and pick up the steps in the service bulletin where I left off by securing the new HS-01231D hinge doubler plate to the stabilator spar with three Clecos using the rivet holes of the rivets that were just removed. I would suggest screwing the four bolts into the assembly at this time to hold alignment for drilling. With the HS-01231D hinge doubler Clecoed in place and the four bolts in place, the remaining four #40 holes are used as guides to final drill #30 all four of the remaining holes into the stabilator’s  HS-1202 front spar.

Match drilling #30 one of the remaining four remaining holes in the HS-01232 hinge doubler into the stabilator’s HS-1202 front spar.


Once the drilling is completed, the HS-01232 hinge doublers are removed for deburring and then each one is riveted in place using seven LP4-3 pop rivets. I used both a pneumatic rivet puller and the close quarter hand rivet puller to rivet the new HS-01232 doubler onto the stabilator’s HS-1202 forward spar.

Using the pneumatic rivet puller to pull one of the LP4-3 pop rivets used to secure the HS-01232 hinge doubler onto the stabilator’s HS-1202 forward spar.

Completed riveting of the HS-01232 hinge doubler onto the stabilator’s HS-1202 forward spar.

With both HS-01232 hinge doublers now riveted in place, work begins on preparing the new hinge brackets. Following the steps in the Service Bulletin the new hinge brackets are comprised of two pieces … the actual hinge bracket HS-01231A and a second piece HS-01231B that has flanges used to create the “box”. These two pieces are riveted together to form the inboard and outboard hinge brackets. The only difference between the two assembled hinge brackets is the outboard hinge brackets receive a K1000-4 nutplate … so prior to riveting the two parts together there is a need to machine countersink two of the HS-01231A hinge brackets for the AN426AD3-4 rivets that are used to attach the K1000-4 nutplates.

The HS-01231A (actual thick hinge bracket) and HS-01231B (thin part with the flanges) are riveted together to form the new hinge bracket assembly.

As can be seen in this photo, the new inboard hinge bracket assemblies on the left are identical to the new outboard hinge bracket assemblies on the right … however, the outboard hinge bracket assemblies on the right receive K1000-4 nutplates and countersinking for the AN426AD3-4 rivets that secure the nutplates.


Next the newly riveted inboard and outboard hinge bracket assemblies are temporarily bolted onto the stabilator’s HS-1202 forward spar so additional drilling can take place. (For this step I used shorter AN3-3A bolts with washers to save wear on the nutplate’s threads). Later, after the last of the drilling is completed, the hinge brackets need to be removed for deburring.

The new hinge brackets temporarily bolted onto the HS-1202 forward spar.

With the new hinge bracket assemblies temporally bolted in place, the HS-1210 hinge stops are attached to the hinge bracket assembly to help hold proper spacing during drilling of the flanges. The HS-01231C stabilator hinge bracket gussets are secured to the stabilator with Clecos using the two holes previously created when drilling out the rivets on stabilator’s spar. Time to drill ... the holes in the HS-01231C gussets are used as drilling guides to match drill into the stabilator’s skin and spar plus the flanges on the new hinge bracket assemblies. Note: At this time the three holes along the inboard edge of the HS-01231C gussets are only drilled to #40 … NOT #30 as all the remaining holes will be.

The HS-01231C secured with Cleco’s …. Amazingly the holes in the HS-01231C gussets lined up almost perfectly with the flanges on the hinge bracket assembly … close enough to be able to get two #40 Clecos into the holes prior to match drilling. The holes in the HS-01231C gusset common to the inboard flanges on the hinge bracket assemblies are match drilled to #40. All the remaining holes in the gusset are drilled to #30.

Using the holes in the HS-01231C gusset to match drill #30 through the stabilator skin and through the outboard flange on the hinge bracket assemblies. The process is repeated for the remaining three HS-01231C stabilator hinge bracket gussets.


Here is the second place I deviated from the service bulletin’s instructions. At this point, due to clearance issues, the instructions would have the builder/owner drill the aft most inboard #40 hole in all the HS-01231C gussets to #30 so a pop rivet can be used at this location … this is because the head of the mounting bolt will interfere with a rivet squeezer. I decided NOT to enlarge this hole to #30 and will just remove the bolt and set the rivet with a pneumatic squeezer then reinstall the bolt. This will result in a consistent look with all three rivets being the same AN470AD3-3.5 … admittedly, more work though.

As can be seen in this photo, the rivet holes with arrows pointing to them are the ones that the instructions would have the builder/owner drill to #30 for a pop rivet due to the bolt head being in the way to squeeze a solid rivet. I’ve elected to just remove the bolt to get the clearance needed for the rivet squeezer so will be setting a solid rivet at this location as opposed to leaving the bolt alone and drilling the hole larger for a pop rivet.


And finally, the third place I deviated from the plans involves machine countersinking the HS-01231C gussets for flush rivets at those locations common to the stabilator’s skin. Did this to keep a consistent look because flush rivets were used on the stabilator’s skins during initial construction. Of course, I only know of one other RV-12 that used flush rivets on the skins so this step will not be a consideration for 99.9 % of RV-12 builder/owners performing the service bulletin.

Test fitting the HS-01231C gusset … after all the match drilling was complete the gusset was removed to machine countersink the five holes common to the stabilator’s skin. Note the inboard aft hole on the gusset is NOT drilled to #30. Also, looking closely, one can see two of the five machine countersunk holes. Machine countersinking the HS-01231C gussets will not be necessary for 99.9% of RV-12’s … the DOG aviation RV-12 is unique in that it was constructed with flush rivets on the stabilator’s skins so performed the countersinking to keep a consistent look.


With all the parts now match drilled, now would be a good time to mark the location and orientation of the HS-01231C gussets and the new hinge bracket assemblies so the parts can be removed for deburring and placed back on the stabilator at the same locations and orientations when drilled.


After carefully marking all the parts to assure proper reassembly, the hinge bracket assemblies and HS-01231C gussets were removed for cleaning and deburring. The holes in the spars were deburred as best as possible. The final assembly and riveting will be covered in the next post.

Doing Service Bulletin 18-02-02 Part 1 of 3

Back in February Van’s Aircraft issued Service Bulletin 18-02-02 involving possible cracks forming on the horizontal stabilator’s front spar. It appears a very tiny number of RV-12’s have developed stress cracks where the bearing bracket mounts onto the stabilator’s front spar. (Some believe the cracks are forming from the common practice of using the seatbelt to lock the control stick full aft which places the stabilator on the stop so it does not move and bang into the stops on windy days. As a result, some believe the energy from strong winds (or passing airplanes) is transferred directly into the spar at the nutplates for the stabilator mounting bolts causing the stress fractures over time).The service bulletin calls for removal of the stabilator and associated hinge brackets for an inspection of the front spar for cracking … if no cracks are found, the inspection is to be performed every 100 hours or annual inspection. If cracks are found, the service bulletin is to be installed immediately.


Just to be clear, NO cracks were developing on the DOG Aviation RV-12 … however, decided while the RV-12 is down for a condition inspection may just as well go ahead and install Service Bulletin 18-02-02 now and be done with it. I’m here to tell you getting the stabilator off and reinstalled just to inspect every 100 hours is not a piece of cake. As such, decided may just as well go ahead and install the service bulletin now as a preemptive strike and have one less thing to worry about. Plus, doing the work now means all the new parts will be on the stabilator when the RV-12 gets painted this coming spring.


Installing the stabilator service bulletin involves removing the inboard and outboard hinge brackets and throwing them away. The old hinge brackets are replaced with a new hinge brackets that sit on a new doubler plate … in addition, supporting parts are added that create a box around the hinge brackets which tie into the stabilator’s skins and spar. There are also additional doubler plates riveted under the stabilator horns for the control cables. This is not a 10 minute job … plan on at least a full day’s work to install this service bulletin.


Prior to attempting this service bulletin, you will absolutely want to procure a 12” long #30 drill bit to easily access some of the rivets that need to be removed and for drilling some of the new rivet holes. (As a side note, builders/owners may want to also consider replacing all the bolts that screw into nutplates with new bolts. In this case that involves replacing 16 AN3-4A bolts and 2 AN4-12A bolts. Is this truly necessary? Probably not. But I have it on very good authority that “ideally” bolts that screw into nutplates should be replaced after each use. Small bolts like these are really inexpensive, so during final assembly, the DOG Aviation RV-12 will receive new hardware at those locations on the stabilator where bolts screw into nutplates).


 Some of the parts included with the service bulletin need to be separated on the band saw … after doing that all the parts were dressed on the Scotch-Brite wheel to remove burrs and smooth edges then prepped for priming. Because my Akzo epoxy primer is now way out of date and changing color, decided to use SEM self-etching primer and place the parts in a hot box for drying.

The parts for the Stabilator service bulletin primed and ready for instillation.

For ease of removal and instillation of the stabilator assembly the RV-12’s tail was lowered by placing the nose gear on blocks so the stabilator was about the same level as the workbench. Before the stabilator can be unbolted from the fuselage a few items need to be removed … starting with the tail cone’s upper and lower faring’s, the pitch trim servo pushrod and of course the upper and lower stabilator cables. Others have reported that the stabilator cables can be removed without unscrewing the adjusting barrels ….. so that was the tact taken. The cables were easily removed by pulling aft on the cables gently and sliding the bolt out. Prior to removing the cables, a piece of safety wire was wrapped around the cable and secured to the tail cone …. Doing this will insure the cable won’t fall into the tail cone if it slips out of the hand. Mike K. gave me a hand removing the stabilator from the tail cone … thanks Mike.

After removing the stabilator cables from the upper and lower stabilator horns, tie wraps were used to help prevent the cables from falling back into the tail cone …. note the safety wire is the insurance policy.


Note: Before discussing the actual instillation of the new parts, fellow RV-12 builders/owners and readers of this Blog should be aware I deviated from the instillation guide in three areas …. I did not drill the control horns per the plans (more on that a couple of paragraphs below), three solid rivets were used on the inboard flanges of the HS-01231B instead of two solid rivets and a pop rivet (more work but done for a consistent look) and lastly because flush rivets were installed on all the DOG Aviation’s RV-12 exterior skins, the rivet holes on the HS-01231C stabilator hinge gussets common to the stabilator’s skins were machine countersunk for flush rivets (99.9 % of builders won’t need to consider this unless, like myself, you used flush rivets on the stabilator’s skins).


OK, let’s get started. The process for the service bulletin begins by making measurements and marking the WD-1207 & 1208 upper and lower stabilator horns to receive six AN426AD3-4 rivets each. The six rivet locations are to be carefully marked and center punched on each stabilator horn. After center punching the horns, the HS-01232 stabilator horn doubler is centered beneath the WD-1207 stabilator horn then match drilled into the HS-1211 spar cap and secured with Clecos.

The HS-01232 doubler is centered under the WD-1207 stabilator horn and between the edges of the spar box and taped in place. Note the center punching for the six holes to be drilled into the WD-1207 horn can be also seen. Also of note, the center punch marks were biased just outboard of the lines to make it a little easier to squeeze the rivets with the pneumatic squeezer (done later).

Prior to drilling, a clamp was used just to make sure the HS-01232 doubler does not move during the drilling process.

Match drilling the #30 holes in the HS-01232 stabilator horn doubler into the HS-1211 spar cap.

Completed match drilling of the HS-01232 stabilator horn doubler into the HS-1211 spar cap.

Here is where I deviated from the plans and why. At this point Van’s would have the builder/owner drill down through the WD-1207 stabilator horn and through the HS-01232 stabilator horn doubler and then into the HS-1211 spar cap. This really bothered me because ultimately the six holes created in the HS-1211 spar cap serve no purpose other than it was easy to do it this way (and admittedly less work). The six holes in the HS-01232 doubler will ultimately receive countersinking for AN426AD3-4 rivets which will be used to attach the HS-01232 doubler to the bottom of the WD-1207 horn leaving the six #40 holes in the HS-1211 spar cap unused  … same applies for the HS-01232 doubler on the other side for the WD-1208 horn.


My solution was to NOT drill the remaining six holes directly into the HS-1211 spar cap … this was accomplished by first removing the WD-1207 and moving it to a drill press, drilling a #50 lead hole at the six center punched rivet locations, then stepping up the six holes to the final size of #40.

Completed drilling of three rivet holes to #50 on one side of the WD-1207 horn … three down three to go.

The newly drilled WD-1207 horn was bolted back in place over the HS-01232 stabilator horn doubler. Next, the six #40 holes in the WD-1207 horn were used as guides to partially drill into the underlying HS-01232 stabilator horn doubler just enough to leave a nice deep dimple but not enough to drill completely through the piece. Tape was placed on the HS-01232 to note correct orientation and the WD-1207 horn was removed so the HS-01232 doubler could be taken over to the drill press and final drilled using the deep dimples as a guide for the #40 drill bit.

Newly drilled WD-1207 horn bolted back in position so the newly drilled #40 holes can be used to match drill the underlying HS-01232 doubler.

Using the #40 holes in the WD-1207 as guides, one can see the HS-01232 doubler was drilled just enough to create nice dimples that can be used to complete the drilling on the drill press.

The HS-01232 doubler with the newly created six holes … note the spar cap in the background came out unscathed without the additional six holes (that would not be used for rivets) had the service bulletin instructions been followed exactly as written.


To complete the work on the WD-1207 the six #40 holes in the HS-01232 doubler need to be machine countersunk from the bottom for AN426AD3-4 rivets. Next the HS-01232 doubler is riveted onto the WD-1207 stabilator horn. To accomplish this task the pneumatic squeezer was outfitted with the little used “no hole yoke” and the WD-1207 stabilator horn was covered with blue tape to prevent scratches.

A “no hole” yoke was used on the pneumatic rivet squeezer to secure the HS-01232 doubler to the bottom of the WD-1207 stabilator horn using AN426AD3-4 rivets.

Completed riveting of the HS-01232 doubler to the WD-1207 stabilator horn.

Test fit of the WD-1207/HS-01232 doubler assembly on the stabilator spar … fits good.

Gee, this was so much fun let’s flip the stabilator over and do it all again for the WD-1208 stabilator horn on the other side using the same process. After riveting the HS-01232 doublers to both the WD-1207 & WD-1208 stabilator horns, both horn assemblies are set aside and will be installed later.


I’m very happy … this portion of the service bulletin turned out great! And with no extra holes in the HS-1211 spar cap. Admittedly, it took more time doing the drilling this way and lots of care needs to be taken to assure proper alignment … just move slowly if considering performing the work the way I did it. Next up is installing the new hinge brackets which will be documented in the next post.

Mr. Sandy Ballast Receives First Passenger Ride In The DOG Aviation RV-12

Due to having done some modifications such as adding the modified “Bender baffle” and moving the voltage regulator onto the baffle … plus, installing interior baggage carpet and padded side panels to the interior I know the weight and balance has changed since the time the first W&B measurements were made.


Because the plan is to do some flight testing with the airplane loaded close to gross weight, felt it prudent to make new weight and balance measurements before blindly trying to test fly the RV-12 near the forward and aft CG (center of gravity) limits. As such, all the fuel was drained from the fuel tank and the airplane was leveled on the scales so new weight measurements could be obtained. For those interested, the procedure for determining weight & balance was covered in the August 10, 2016 post found at the following link.


Performing weight & balance measurements on the RV-12


After taking the new weight measurements, the weight and balance sheets were updated to reflect the changes and per FAA regulations, an updated copy is kept inside the aircraft. Also updated the aircraft maintenance log books as well.


My CG did move forward some as I expected it would from the modifications. As it sits, the DOG aviation RV-12 will hit the forward CG limit when there is only one gallon of fuel left in the tank when I fly solo … and with a 230 pound passenger, the forward CG limit will be hit with 3 gallons of fuel left. So I feel I’m in the sweet spot because I know when the RV-12 gets painted, the CG will move aft … so hitting the forward CG limit after painting should not be an issue when giving rides to most people who are capable of comfortably fitting into the RV-12 cockpit.


Chad (an A&P mechanic that works on lots of airplanes on the field) was nice enough to loan me 230 pounds of sand bags for the test flight …. Thanks Chad!  I borrowed one 50 pound of play sand and three 60 pound bags of tube sand. The plan was to get close to gross weight but not over while keeping near the center of the RV-12’s CG range which is 80.49 inches to 85.39 inches. With myself, 230 pounds of sand, 19 gallons of fuel and no baggage, the takeoff CG was 82.66 inches. Although not perfectly in the center of the CG range 82.66 inches is close enough. In this configuration, the CG will slowly move forward as fuel is burned and at approximately the 3 gallon point the forward CG limit will be met. As such, I plan to fly down to about 5 gallons so as to get close to the forward CG limit and check out the handling. Because the RV-12 is a proven design, I don’t expect any control issues or surprises.


After removing the passenger’s seatback and seat bottom cushion the 50 pound bag of play sand was placed on the passenger seat floor. Because the sand bags have been used quite a bit, some were showings signs of wear … so as an insurance policy, the decision was made to place all the sand bags into trash bags just in case there was an unwanted rupture.

First 50 pound bag of play sand placed into a trash bag and placed on the passenger seat floor.


The next three 60 pound bags of sand are of the tube variety and those were placed upright on the 50 pound bag of sand. This arrangement actually worked out quite well in that the sand bags did not interfere with the flap handle or the ELT mounted on the far right … and more importantly did not interfere with control stick movement. Cargo straps were placed around the bottom of the tube sand bags and fed through the handle for spar pin as an anchoring point to prevent the sand bags from sliding to the left towards the flap handle. A second cargo strap was placed higher up and secured to the fuselage cross brace.

Mr. Sandy Ballast bravely volunteered to become the first passenger to receive a flight in the DOG Aviation RV-12. With the three bags of tube sand positioned two aft and one centered forward there was plenty of clearance between the stick and Mr. Sandy Ballast.


The test flight occurred during a beautiful hot morning. The air was perfectly smooth throughout the flight and even though Mr Sandy Ballast was very quiet during the entire test flight, I think he had a great time as the airplane made tight turns, stalls, and some touch-and-go landings.


There were no surprises during the test flight … the extra weight and warm temperatures (high 80’s) make for a little longer ground roll than when solo. Climb-out was good just not as sporty compared to being solo. Landings were uneventful, but I did notice more brake was required to slow down and the stopping distance was longer than when flying solo. All the things one would expect with a heavy passenger.


The RV-12 is simply a nice flying Light Sport aircraft.