The Eagle Receives A Rudder Trim Tab

During the second test flight where the RV-12 was flown for over an hour and away from the home field’s traffic pattern, it was noticed there is a yaw component that needs addressed. To keep the airplane flying without yaw, it required a constant pressure on the right rudder. This is not unusual for a RV-12 without rudder trim … in fact, I would say it is the norm. As mentioned in a previous post, this was expected because I can’t remember seeing any RV-12’s at Oshkosh that didn’t have a trim tab or a wedge on the left side of the rudder. Van’s now has a trim tab available for the RV-12, but unfortunately it came out after the DOG Aviation RV-12’s rudder was completed.


A few weeks ago I ordered a bunch of goodies for the RV-12 such as a canopy cover, sun shade and a trim tab which will be installing now before the temperatures plummet … I wanted to use AKZO primer which is temperature sensitive, so instead of flying more at this time, we are spraying paint. The part number for Van’s trim tab for the RV-12 is R-01220 … the trim tab comes predrilled and pre-bent for the amount of trim that is typically needed at cruising speeds to achieve flight without yaw.

The pre-bent R-01220 trim tab and associated AD-41-ABS rivets used for instillation.

Installing the R-01220 trim tab on a completed rudder requires the removal of one rivet … the lower aft rivet on the left side on the rudder. Prior to removing the rivet and begin drilling, decided to prime the mating area first because the temperatures were forecasted to get much colder than would be suitable for the Akzo epoxy primer to cure properly. The trim tab was held in position and a line was traced around the trim tab so the area could be masked off and sprayed with primer along with the mating surface on the trim tab.

After placing the trim tab in position, a line was traced around it to denote the area that would require masking and scuffing with a ScotchBrite pad.


A one ounce batch of primer was mixed up and the RV-12 was rolled outside and the primer was airbrushed onto the rudder and trim tab along with a couple of other small parts that I want to install in the future.

Akzo primer was airbrushed onto the surface of the rudder where the trim tab will be installed.

As mentioned above, the lower aft most rivet on the left side of the rudder requires removal so the mandrel requires being pounded out so the rivet can be drilled and removed. Those following the DOG Aviation Blog know flush rivets were used during construction, so the rivet being removed is a flush rivet … this will require dimpling the corresponding hole in the trim tab. All the remaining holes that will be drilled will NOT be dimpled because the rudder is now built and there is no access. Also, the rivets are so close to the trailing edge that there is not room for the dimple dies … so the trim tab will only receive one dimple where the flush rivet is being removed and the remainder of the rivets will not be flush.

My finger is pointing towards the only rivet that requires being removed. This rivet hole is used to orientate the trim tap in the correct position while match drilling the remaining holes into the rudder. Because a dimple already exists here, the trim tab will be dimpled only at this location.


Not wanting to just pound on the rudder with a hammer while the rudder was on its stop, decided it best to ask for assistance … so asked Bernie if he could come by the hanger for a few minutes to give me a hand. Bernie held a rag covered block of wood on the right side of the rudder on the rib opposite of the rivet being removed. I used a hammer to pound out the mandrel in the center of the rivet using a mandrel from another rivet that was tapered on the end a little on a Scotch-Brite wheel. Once the mandrel was removed, the head of the rivet was drilled until it popped off so the remaining portion of the rivet could be pushed in clear of the rivet hole. After the rivet was successfully removed, the F-01220 trim tab was secured onto the rudder with a Cleco so the bend line on the trim tab could be aligned with the aft edge of the rudder. Once in position, the trim tab was taped in place so it would not move while drilling.

Match drilling the rudder trim tab to the aft left side of the rudder. Notice the drill has a drill collar. It was adjusted to only allow the drill to penetrate just a little deeper than the skins so the drill bit would not hit the opposite side of the rudder.


After drilling, the rivet holes in the trim tab and the rudder’s skin were deburred. To install the R-01220 trim tab, the lone dimpled hole received a flush rivet and the remaining nine rivet holes received the AD-41-ABS rivets supplied with the trim tab.

Using the hand rivet puller to rivet the F-01220 trim tab onto the RV-12’s rudder. The lower left hand rivet is a flush rivet because the rudder was already dimpled at this location … the remaining nine rivets are AD-41-ABS rivets.

Completed instillation of the F-01220 rudder trim tab on the DOG Aviation RV-12.

Flight Testing The DOG Aviation RV-12

It has been a few weeks since the first flight but at this point there has now been a few hours of phase one flight time logged on the RV-12. For those non-aviation readers of the DOG Aviation Blog not familiar with the rules for initial flight testing, here is a quick rundown. The FAA imposes a flight testing period called “phase one” testing. The required phase one “fly off” time period will vary depending on the certification type of aircraft. Because the DOG Aviation RV-12 was built and certificated as E-AB (experimental- amateur built), the FAA’s rules dictate the required phase one fly off time be 40 hours. The FAA will assign a flight testing area (this area can be negotiated within reason) for the phase one flight testing. During the phase one flight testing of the aircraft, the pilot must conduct all test flights within the boundaries of the assigned phase one testing area solo … no passengers allowed. After the phase one testing is completed, the shackles are lifted and the airplane is free to fly wherever the pilot desires … also, at this point, passengers can be given rides in the aircraft.


Being a “test pilot” is something not to be cavalier about … it needs be taken quite seriously and methodically as confidence in the aircraft is gained all the while slowly expanding the flight parameters. My hope was to have more time on the RV-12 by now, but the weather has not cooperated as much as I had hoped. There have been rainy days, days with very low clouds and days that although sunny, had way much more wind than I felt comfortable with for the first few hours of flight testing. Admittedly, thus far, I’ve been overly conservative on my weather requirements but there is no shame in that … in fact, it is prudent.


The RV-12 flies really nice and I'm very pleased with it thus far. But it can be made to fly even better ... in that, there are a couple of minor issues that need to be addressed. Now that I’ve got more hours on the RV-12 and have been up to fast cruse speeds there are two small issues that need addressed. First there is a slightly heavy left wing. It only requires fingertip pressure on the stick to keep the airplane level, but it will not fly level if the finger is removed. Letting go of the stick allows the left wing to slowly drop off from level and the aircraft begins to roll to the left. Having a heavy wing is quite common and for the most part fairly easy to resolve. The solution Van’s suggests trying first is reshaping the aft edge of the flaperon on the LIGHT wing (the right wing in my case). I made a small adjustment a couple of days ago and flew the RV-12 again yesterday and although slightly better it was not enough correction. After landing, I carefully used a pair of seeming pliers to tighten the bend (ever so slightly) on the aft edge of the right flaperon so will see if that was enough. Van’s says it does not take much to get the desired results so I did not get very aggressive. This type of tweaking requires lots of patience … make a small adjustment and go fly … repeat … until satisfied with the results.


The other small issue that I knew would be present at cruse speeds is yaw. The right foot needs to constantly apply steady pressure on the right rudder pedal to keep the aircraft flying straight without any yaw. Of course, that gets tiring after a while, so a rudder trim tab will be necessary. Read more about that instillation in the next post.


The other issues that were discovered after the first flight appear to be resolved. The oil line that had a smear of oil on the fitting was tightened and is not showing any signs of leakage now. Also the oil that was found dripping from the bottom of cylinder #1’s rocker arm cover was traced back to the exhaust stud during inspection and cleaned off. Now after the after the second flight of well over an hour, is almost cleared up now. After removing the cowl for inspection a slight amount of dark oil was found under the exhaust flange stud for the #1 cylinder as can be seen in the photo below.

Using an inspection mirror to view the small dark oil mark coming from cylinder #1’s exhaust pipe flange stud.

As can be seen in the above photo, the amount of dark oil is now just a small streak after over an hour of flying. The first flight only lasted fifteen minutes and there was oil all the way under the rocker arm cover and a drip onto the lower cowling. Now after an hour, there is just a small streak of dirty looking oil, so I’m convinced this is either oil left over from the machining process or an anti-seize lube of sorts … my money is on lubricant left over from the machining process working its way out of the thread gallery for the stud.


The other unexpected issue discovered a week ago was a small fuel leak coming from the fuel valve on the bottom of the gascolator. At first I thought it was a leak from the valve not sealing correctly ... but upon closer inspection, it was determined the fuel was actually leaking from the threads on the fitting. The fitting was tightened … twice in fact, and although the leak diminished somewhat, it did not stop.

The CAV-110 fuel valve can be seen here screwed into the bottom of the gascolator.

Close-up photo of a CAV-110 fuel drain valve.

I ended up deciding on just replacing the CAV-110 fuel valve and also used a different type of thread sealant (TiteSeal) on the threads … seemingly no issues now.

The Eagle Flies!!!! The Long Awaited For First Flight

Monday morning was a monumental occasion at DOG Aviation. A little over four years after beginning assembly of the DOG Aviation RV-12 the time had finally come for the Eagle to leave the nest and take me along for the ride. To the best of my knowledge, the DOG Aviation RV-12 is the first RV-12 to fly that is constructed using flush rivets on all the exterior surfaces ... I only know of one other RV-12 in Florida that is being constructed with flush rivets and it has not flown yet.


With the help of ground crew members Mike T. and Bernie, the RV-12 was rolled out of the hangar and into the brisk 48 degree morning air.

Ground crew member Mike T. was an attendee for the maiden voyage event.

Ground crew member Bernie handed me his phone so I could receive good luck wishes from Mike K. the remaining ground crew member who, unfortunately, couldn’t be present.



After the well wishes were out of the way, got myself strapped in and began working through items on the pre-start checklist.

Inside the cockpit preparing the RV-12 for the maiden voyage.

Gee, this looks serious. Also of note: One can see Mike’s new small video camera clamped onto the right seat frame … more on that below.


The Rotax 912 engine was started easily enough but it did require leaving the choke on a little to keep the engine running smoothly. This was by far the coldest day that the engine was started so when the choke was pushed off (as I have been doing during the warmer days) the engine instantly cut out and required a restart. This time, a little choke was left on until the engine warmed up to the point that easing off on the choke didn't result in a loss of RPM. With the choke now off and the engine warming up slowly, the RV-12 was taxied around to the other side of the hangars and a call was made to controllers to obtain taxi clearance to the far side of the airport to get to the active runway.


A little back story about the camera that can be seen I the previous photo ... Mike  T. came by the hangar last week and said he had a surprise me. Mike unzipped a small bag revealing a small video camera that could be used to document the first flight …. Very cool! The camera could transmit to Mike’s smart phone so the video could be watched on the phone while the camera angles were being adjusted. Sweet setup! The “plan” was to turn on the video camera after a successful run-up was made prior to taking the runway. Well, unfortunately that didn’t happen … with all the adrenalin, excitement, and first flight concerns, plus interfacing with the air traffic controllers, I simply forgot to reach over and turn the camera on.


After the run-up and forgetting to turn on the video camera (sorry Mike), the RV-12 was rolled onto runway 1 at KCAK to begin its maiden voyage towards the broken clouds high overhead.  After lining up with the runway’s centerline, power was applied and the Rotax 912 engine quickly accelerated the RV-12 down the runway with seemingly no effort and easily pulled the RV-12 off the ground and towards the clouds, taking me along for the ride.

Bernie snapped this photo of the DOG Aviation RV-12 just after the crosswind turn.

Admittedly, I was taken a little by surprise at how fast the RV-12 seemingly leaped off the runway and began gaining altitude. I was expecting to be on the ground a little longer based on the RV-12 transition training taken in California. But then it occurred to me … that was with an instructor in the aircraft more than doubling my own weight and also in much hotter 95 degree air compared to the much denser 48 degree air currently at the airport. The takeaway for fellow RV-12 builders about to fly the bird for the first time …. everything will happen quicker than when you were in the RV-12 with an instructor receiving transition training. The RV-12 accelerates quicker, gets off the ground quicker and climbs quicker … it is impressive.

Return from the future: Below is a short video of the DOG Aviation RV-12's first test flight that Mike made with his cell phone.


I had no intentions of making the first flight long or even working on Van’s flight test cards. The sole goal for the first flight was to get the bird in the air and fly a loop or two around the airport and land for inspections. As it turns out, due to traffic, I was instructed to extend the downwind and wait for the tower to call my turn to base. This took me much farther from the field than I would have desired for the first flight…  but time wise, it probably almost worked out to making two tight loops around the runway, so when given the OK to make the turn to base, the decision was made to just land and taxi back to the hangar.


Unfortunately, there are no photos of the takeoff or landing which is unfortunate. (Mike did get a short video on his phone of me flying overhead which I’ll post when I receive it). Making an initial flight from a larger class C airport does not lend itself to on field photographic activities. One can’t just walk out to the edge of the runway with a camera in hand and snap away without dealing with airport security and a likely a very long conversation with TSA personnel.


The return to terra firma was nice and smooth along with being centered on the runway. Just the way you want the first test flight to terminate … uneventful. Although the time in the air was relatively short, I didn’t notice any control issues with the RV-12, but then again, I did not get it up to cruising speed either. Did notice right rudder was needed to prevent yaw, but knew that would be the case since the rudder has no trim tab yet. Notice the word yet … the DOG Aviation procurement department decided to order a sun shade and canopy cover through Van’s and along with the order, had Van’s include the trim tab for the RV-12. Unfortunately, the trim tab was not available when construction began on the rudder four years ago.

The "RV grin" … after a successful first test flight in the DOG Aviation RV-12. In a way, my late friend, fellow pilot and Oshkosh partner Marty Dippel was also able to partake in the first flight of the DOG Aviation RV-12 … in that, I was wearing Marty’s leather flight jacket.


After the above photo was taken, the RV-12 was rolled back into the hangar and the upper cowl was removed for inspection. My friend Bernie noticed a drip of an oily substance on the bottom cowl's aluminum heat shield under cylinder #1. I ran my hand under the valve cover gasket and got some dark oil on my fingers. The first thought was the valve cover gasket was leaking … but the darkness of the oil didn’t make sense. Upon further investigation with a mirror, the substance appeared to be coming from an exhaust stud that secures the flange for the exhaust pipe to the exhaust port on the cylinder. The oily substance is very dark, so there is no way its oil leaking from the engine. Our conclusions, it is likely a lubricant left over from the machining process or some type of anti-seize lubricant used during assembly. This assessment was made based upon further inspections of the other cylinders which revealed the same thing occurring but to a much lesser degree. Unfortunately, we cleaned it up before I thought of taking a photo for the blog.

Return from the future: This is a photo taken using a mirror that shows the area around the #1 cylinder exhaust flange stud that the dark oily substance mentioned above was coming from. This photo was taken after a little over an hour of flight time. Now there is just a little streak of the dark oil … which seems to confirm to me the oil that was dripping after the first flight was likely from the machining or assembly process. The tipoff for me is that the oil is dark and dirty looking ... if it were actually engine oil, the oil would be clean looking like the oil in the oil tank.


The only actual possible leak found during the inspection was a small smear of oil on the bottom of the fitting for the oil line coming from the oil cooler where it attaches to the right side of the engine. Not sure if this was an actual leak or a smear of oil from when the oil line was installed … but just to be on the safe side, the fitting was made a few degrees tighter with a crows foot wrench. So this will be a location I will need to be keeping my eyes on during the next few flights.


Return from the future: After tightening the oil line fitting mentioned above a tad more, there is no longer any signs of leakage.

Carburetor Balancing Completed With CarbMate

Getting impatient and wanting to move forward I was looking around for an alternative source for the vacuum gauges when I stumbled upon the CarbMate TS-111 in stock at a local racing store (Summit Racing) at a fair price. I have read where other Rotax 912 owners have used this unit to balance the carburetors with good results, so decided to get one on will call and made the drive to Summit and picked it up.

The CarbMate TS-111 carburetor syncing device. A single row of LED’s are used to show the user if the second carburetor has a higher or lower vacuum than the reference carburetor. When both carburetors are synchronized, the green “happy face” LED in the center lights up.


So today the RV-12 was rolled outside and fired up and the CarbMate TS-111 was used to balance the carburetors. Because I decided to use the vacuum ports on the intake manifolds, it was necessary to block off the crossover tube. This is done by flattening the rubber hose from the manifold to the crossover or balance tube. On my newer engine the right side hose is just a little longer than the one on the left side for this very reason. Older Rotax 912 engines require the balance or crossover tube be shortened a little to use the method I used. I want to make a better hose clamp but for the time being what I used did work well. The setup consisted of two pieces of aluminum that were compressed onto the balance tube hose using a C clamp to compress the hose flat thus blocking it off.

C clamp and two pieces of aluminum were used to flatten out the rubber hose on the balance tube to block the balance tube. After this photo was taken electrical tape was wrapped around the components to insure no flying pieces from prop blast should something come lose.


 The CarbMate worked OK … but I still would prefer gauges.  The CarbMate only has one row of LED’s so one carburetor is considered to be the reference and the second carburetor is adjusted to match the “reference” carburetor. When the second carb is adjusted to match the reference carburetor, a green LED lights up in the center of the display showing a “happy face”. So you don’t really know what the actual vacuum is for either carb … only that they match or the second carburetor has a higher or lower vacuum than the reference carburetor. So the CarbMate works well for syncing the carburetors, but is not a good trouble shooting tool like a set of good gauges would be.


Based on the advice of a well-known Rotax mechanic, I used a higher RPM of 3500 to balance the carburetor off idle setting. This is because at 3500 RPM the carburetor is no longer using the idle circuit. The carburetor adjustment for off idle was performed first then the balance was performed at idle. All this took a few cycles of starting the engine then shutting down and making an adjustment and climbing back into the cockpit and checking the results.

As can be seen, at 3,500 RPM I was able to obtain a center green “happy face” on the CarbMate TS-111.


After the carbs were synced, the upper cowling was installed and the RV-12 was taxied over to the on field compass rose to adjust the compass.  What’s next? The sky’s the limit.