The First Condition Inspection – Tips For Builders

Have procrastinated a little getting this post written but the good news is, the first condition inspection has revealed no significant issues with the DOG Aviation RV-12. However, I did run across a couple of speed bumps that created delays. One time consuming task was looking up the torque values for all the hardware on the airplane. I’m not referring to the standard torque values for AN3 or AN4 bolts which builders have well memorized by the time the airplane is completed … no, I’m talking about the myriad of parts that have unique torques such as Matco brake hardware, the Rotax engine hardware, propeller bolts, etc. Plus, there is the time spent sifting through the documentation for additional information such as tire pressures, stabilator cable tensions, nose gear breakout forces, etc.


Tip for builders: My suggestion is while assembling the RV-12 each time you run across a nonstandard torque value, breakout force, gap measurement or pressure reading document it on a list that can later be tailored to suit your needs via a word processor or spreadsheet. Having a list that shows torque values, clearances, breakout forces, spark plug gaps, etc. will make the first condition inspection on your RV-12 or any kit aircraft move along so much faster and all inspections thereafter. In fact, I would also suggest taking things one step further by making a complete list or spreadsheet of inspection due dates for items such as testing of the transponder and the required quarterly ELT test … in addition, include expiration/replacement dates for items such as the batteries in the ACK E-04 (I did record the main battery for the ELT in the avionics log but did not record the battery dates for the associated remote panel indicator or audio alert indicator) along with dates for firewall forward items such as fuel pump replacement, rubber hoses, brake fluid, coolant, etc. Wish I had thought about creating those lists during the construction process. Moving forward, assembling a meaningful list related to inspection items along with perhaps keeping a white board in the hangar will make future inspections much less time consuming. I spotted a white board in the hangar across from me and thought it was a good idea so took a photo of it to use as a guideline for making my own white board.

Photo of a whiteboard spotted in a hangar across from me. There seems to be merit in creating a white board for keeping a visual on major inspection due dates and time related items such as oil changes.


Decided to begin the condition inspection at the nose of the aircraft and move aft. Van’s documentation suggests checking the torque of the propeller hub after the first six hours … I went beyond that knowing the annual was nearing. For the benefit of non-aviation readers of the Blog, the two Sensenish propeller blades are captured between two half hubs … the one called the mount hub is bolted to a mounting flange attached to the propeller shaft coming out of the gear reduction unit on the front of the Rotax 912ULS engine and the other is called a clamp hub which captures the two propeller blades and is bolted to the mount hub. Unfortunately, to check the mounting bolt torque on the mount hub, it requires removing the clamp hub and both propeller blades. It would be nice if the bolt heads sat in a recess or up against a stop so the bolts would not rotate allowing the bolt torque to be checked without removing the blades … but sadly, that is not the case so the clamp hub and blades need to be removed to gain access to the mount hub bolt heads. As it turns out, the nuts on two of the six bolts moved slightly when the torque was checked … the required torque is 18-20 foot pounds so I was shooting for 19.5 lbs. to allow for a little drag in the locknut.

These are the nuts and bolts that attach the mount hub onto the mounting flange. Unfortunately, to properly check the bolt torque it requires the removal of clamp hub and propeller blades to gain access to the heads of the bolts.


Avid readers of the DOG Aviation blog may recall when the propeller blades were first installed they were pitched wrong and after posting photos of the work session, I received an Email from a fellow builder who caught the error (thanks again Nick). This required loosening the clamp hub bolts a couple of extra times while readjusting the blades. Unfortunately, Nord-Lock washers self-destruct a little each time a bolt is loosened, so they are only effective for a few cycles because the capturing ridges on the washers get worn down easily. Knowing this, I figured the Nord-Lock washers should be replaced since they had been exercised a few times already… so prior to beginning the condition inspection, I purchased new Nord-Lock washers at a local bolt & nut supply. Well, much to my surprise, when about to use the new Nord-Lock washers, I discovered they were a much smaller outer diameter than the Nord-Lock washers supplied by Sensenich with the propeller kit. This resulted in a parts delay because I needed to order new Nord-Lock washers directly from Sensenich. So my tip to fellow RV-12 builders is to plan ahead and have some spare Nord-Lock washers on hand when planning to remove the prop mounting bolts … just make sure the Nord-Lock washers are the larger diameter ones.

On the left is a used Nord-Lock washer removed from the propeller hub and split in half to reveal the worn ridges on the washer. On the right is a new Nord-Lock washer split in half so the locking ridges can be seen.  Also note the outside diameter of the standard Nord-Lock washer on the right that was procured locally has a much smaller outside diameter than the Nord-Lock washers supplied by Sensenich on the left.


The new Nord-Lock washers received from Sensenich were placed in the digital caliper and measured in at 21/32". So fellow builders attempting to locally source Nord-Lock washers for the propeller bolts, make sure you purchase washers that have an outside diameter of 21/32" … otherwise you will need to place an order through Sensenich.

The Nord-Lock washers that Sensenich supplies for the RV-12 propeller utilizes a washer with an outside dimeter of 21/32" which is a larger OD than typical for a 5/16" diameter bolt.


After replacing the Nord-Lock washers that hold the clamp hub in place, the propeller blades were pitched with a digital level to 71.4° using the method in Van’s plans along with the Van’s pitch tool. Got the pitch even better than the first time around … now both blades are within .05° of one another. For those not familiar with the process of adjusting the RV-12’s propeller blades, the following is a link to a post that covers that procedure:
Link to the procedure for adjusting the Sensenich propeller blade pitch on the RV-12.


About the only item I found that NEEDED correcting was the temperature thermostat for the Reiff heating system … it had popped off the oil tank. Frankly, I was not surprised to see this because when installing the Reiff heating system I began by scuffing up the aluminum on the bottom of the engine and cleaning with Acetone then mixing the epoxy and attaching the heating pad to the bottom of the engine. Then without thinking I slathered the thermostat for the oil tank with epoxy and affixed it to the side of the oil tank …. only to realize, darn (not the word I used at the time) I had not yet scuffed the oil tank and cleaned it with Acetone before applying the epoxy. Figured it was too late to do much of anything, so the thermostat would either stick, or not … which ended up being the case. To correct the problem all the old epoxy was cut off the thermostat and the oil tank with a razor and both the oil tank and thermostat were roughed up with sandpaper and a jewelers file. Reiff suggests using JB Weld as a substitute for the epoxy they supply with the heater kit, so that is what was used for the repair. The JB Weld was applied in two applications. The first application was to the bottom and sides of the thermostat so a piece of safety wire could be placed around the oil tank and tightened to keep the thermostat pressed against the oil tank while the epoxy cured. After the epoxy cured, the safety wire was removed and a second application of epoxy was used to cover the top and sides of thermostat. Hopefully this will no longer be an issue … but moving forward, this will be an area I will be keeping an eye on especially now that winter is coming and I’ll be using the heater.

My finger is pointing to the oil tank thermostat for the Rieff heating system  that was epoxied back onto the oil tank using JB Weld epoxy. This time both the thermostat and oil tank received a good scuffing and cleaning with Acetone … hopefully the thermostat it will stay affixed to the oil tank.

Switching To “Newest” & “Improved” Carburetor Floats

For a large portion of time during the construction of the DOG Aviation RV-12 there have been some issues with the Rotax 912 ULS engine’s carburetor floats. The root of the problem revolves around some carburetor floats absorbing fuel and sinking in the float bowls. Apparently, the material the floats were made from (looks to me like some sort of special foam plastic with a hard outer coating or sealant) tend to adsorb fuel which causes them to get heaver so they begin sinking in the carburetor bowls. The sinking floats allow more fuel into the carburetor bowls than desirable … which begins to create a rich mixture as the engine becomes flooded with excess fuel.


A few years back when this began to become problematic, Rotax changed the manufacturing process and tested the floats. The newer tested floats were given dimples for identification so they can be distinguished from the older non-dimpled floats and were supposed to be “the fix” for the fuel absorption issue. Rotax issued a service bulletin suggesting that all non-dimpled floats should be replaced with ones that are dimpled as pictured below. And, if not replaced, the non-dimpled floats required being checked at regular intervals (25 hours or 60 days) by using one of two methods …. either remove the floats and weigh each pair (the pair must weigh less than 7 grams) or pass a displacement test where a measured amount of fuel is injected into the carb with a syringe while looking at the overflow orifice until fuel flows out of it. Depending on the amount of fuel it takes to see fuel exiting the overflow orifice, one can determine if the floats are soaked with fuel or not. Either way, it is a pain in the butt.

Going back a few years, per a Rotax service bulletin, older non-dimpled carburetor floats in Rotax 912 engines are to be replaced with floats that are dimpled such as the ones shown in these photos.


However, as time went on, it was realized that even the newer “dimpled” replacement floats were developing the same problem of adsorbing fuel and sinking in the carburetor bowls … it just did not occur as often. Now Rotax has changed the floats yet again and given them yet another new part number of 861-188. It is my understanding Rotax has also changed the material the floats are made from and is now making the floats from a denser material. The “newest” floats can be identified by what appears to be the loss of the brass sleeve or bushing that passes through the float. In fact, there is still a brass bushing but it is much shorter and centered in the hole making it difficult to see. This next statement is purely a guess on my part: I suspect because the material the newest floats are made from is denser, it is very likely also heaver … so to keep the measured weight for each float the same as the old floats, the amount of brass used for the bushing was reduced.

The old style float is on the left and the “newest” style 861-188 float is on the right. The maximum weight remains the same … both floats weighed together must weigh less than 7 grams. (They typically weigh slightly under 3 grams each out of the box).


Admittedly, I was not currently experiencing issues with the floats in the DOG Aviation RV-12 but decided to make a preemptive strike and just replace the floats with the “newest” 861-188 floats now that they are available. When ordering the newest floats, the DOG Aviation procurement department also purchased a float bracket gauge (part number 877-730) so the float arms could be accurately adjusted to parallel. To use the float bracket gauge the main jet is removed and the gauge is screwed to the base of the carburetor in place of the main jet.  Glad the gauge was purchased because the float bracket arms were adjusted by sight the last time the carb floats were changed … but the gauge reveled that although close (think it was around .024"), the float bracket was out of spec which is listed between .016" to .020" measured between the gauge and the float bracket arm using a feeler gauge. With the 877-730 gauge in place, the float bracket arms were adjusted to .018" which is the sweet spot per the maintenance manual.

The Rotax 877-730 float bracket arm gauge in position after removing the main jet. The float bracket arms are tweaked so the gap between the float bracket arm and the gauge is .016" - .020" … I chose to adjust the arms to .018" as can be seen here.


Hopefully, by switching to the newest style 861-188 carburetor floats at this time, it will eliminate the likelihood of carburetor float issues in the future.

Condition Inspection - Rotax 912ULS Differential Pressure Check

One of the tasks I wanted to perform during the condition inspection was a check of the differential pressure of the Rotax 912ULS engine. According to the maintenance manual, this could have been delayed until the engine has 200 hours but thought creating a baseline now would be a good idea.  The differential cylinder pressure test involves a special testing apparatus called a Differential Cylinder Pressure Tester. The test apparatus consists of a built in pressure regulator and two matched pressure gauges. The pressure gauges are connected together via an orifice and valve. The size of the orifice will change depending on the displacement of the engine … typically, engines with a cylinder bore smaller than 5" will need a tester utilizing a .040" orifice and, of course, the Rotax 912ULS engine falls into this category. (A tester for larger bore engines typically utilize a .060" orifice).

The ETC Model E2A differential cylinder pressure tester with 12mm adapter hose.

To accommodate various spark plug hole and thread sizes, the ETC Model E2A differential cylinder pressure tester pictured above can be ordered with various hoses that have the proper threads for the spark plug holes on the engine being tested. The correct adapter hose for the Rotax 912ULS engine requires a 12 mm thread to screw into the engine’s spark plug holes.


A differential cylinder pressure tester IS NOT a compression tester in that it does not read the actual compression value for a cylinder as one would with the typical compression testing gauge. Instead, the differential cylinder pressure tester gives an overall indication of how well the piston rings and valves are sealing. This is accomplished by connecting the tester to an air compressor then adjusting the regulator on the tester so the left gauge displays 80 psi … this becomes the reference pressure. The test reading is obtained by placing the cylinder under test to top dead center and slowly opening the valve to allow the pressure to enter the cylinder under test. While making sure the left reference gauge still displays 80 psi (adjust regulator if necessary) the reading on the right gauge is recorded. The difference between the left reference gauge and the reading on the right gauge establishes the differential which can be represented as a percentage. According to the Rotax maintenance manual, the maximum permissible differential is 25% so that would be a reading as low as 60 psi on the right gauge.

With the valve off (facing down) and the ETC Model E2A differential cylinder pressure tester connected to an air compressor, the regulator knob on the tester is adjusted until the left reference gauge displays 80 psi.


Caution: One can become seriously hurt while performing this test if not very careful. The instructions caution the user of potential dangers and suggest the testing be performed while a helper holds the propeller when opening the valve to apply air pressure to the cylinder under test. This is truly good advice especially if new to using a differential pressure tester because if the cylinder is not at a perfect top dead center, there will be a tremendous amount of rotational force applied to the propeller. I have helped perform this test in the past and was well versed in what can happen if not careful. It can be done by yourself, but it is tricky. After the left gauge is adjusted to 80 psi place a finger in the spark plug hole of the cylinder being tested and turn the propeller until you begin to feel the compression stroke pushing air out of the cylinder then screw in the 12 mm adapter hose into the spark plug hole. While tightly holding the propeller, very SLOWLY open the valve just enough to allow a little air to pressurize the cylinder enough to feel some torque being applied to the propeller. Next slowly move the prop back and forth a little while watching the right gauge … the object is to move the propeller to the position where a peak reading is obtained. The peak reading will occur when the piston is at or very near top dead center. At this point, while holding onto the propeller really tightly continue SLOWLY opening the valve further until it is full open and record the reading on the right gauge … then close the valve and wait a little for the air to bleed out of the cylinder. If done correctly, it is very easy to hold the prop at top dead center with one hand …. however, if you are off a little it takes both hands to prevent the prop from moving.


Unfortunately, because of the inherent danger of performing the differential pressure testing by myself, I felt it was not safe to try fiddling with a camera to obtain photos showing pressure readings on the right gauge. All the cylinders showed approximately a 1% drop which is about what I would expect from a virtually new engine since there is always a small amount of air that gets past the rings even on new engines.

Removing The U-1220 Main Gear Legs For Priming

Savvy RV-12 builders following the Blog may have noticed the gear legs on the DOG Aviation RV-12 were not primed … even though the gear legs are just about the only component on the RV-12 that Van’s assembly instructions make a special note in bold print informing the builder to MAKE SURE the gear legs are primed with a high quality primer, preferably epoxy primer. During the late fall massive primer session for the finishing kit parts, the gear legs were overlooked because they were at the bottom of a crate with cardboard over them …. out of sight, out of mind. This oversight was not noticed until it was time to install the gear legs so the decision was made to continue moving forward and deal with it later …. and later would be now. Because the gear legs are showing signs of the beginnings of corrosion, as can be seen in the photo below, felt it would be best to make it right during the condition inspection.

The beginnings of surface corrosion can be seen because of the lack primer on the gear leg. Priming the U-1220 gear legs is called for in the plans … Van’s recommends an epoxy primer as a first choice. The corrosion developing on both gear legs looked pretty much the same as this right main gear leg.


Removing the main gear legs involves removing the wheel and axle/brake assembly. Decided to take a short cut and not remove the brake lines from the calipers. This was accomplished by removing the wheel nut after removing the two bolts that secure the outboard brake pad … this allows the wheel/rotor assembly to be removed from the axle leaving the caliper and inboard brake shoe attached to the axle assembly. After the wheel was removed from the axle, a thick paint stir stick (the thick type used to mix 5 gallon pails of paint) was quickly used as a substitute rotor and the outboard brake pad was bolted back on finger tight. The reason for placing the thick paint stick between the brake pads is to prevent the brake piston in the caliper from popping out of the caliper and creating a huge mess of brake fluid everywhere. Felt this would be a good idea because the brake assembly will be off the gear legs for a few days, so didn’t want any unexpected surprises similar to what a friend experienced with his airplane’s caliper piston popping out overnight and draining all the brake fluid onto the floor of his hangar.

My finger is pointing to the paint stick placed between the two brake pads to prevent the piston from popping out of the caliper during the extended time the brake assembly will be off the aircraft.


After removing the axle assemblies from the gear legs, each gear leg was easily unbolted from the center channel and removed. The gear leg removal was a piece of cake … (but the same could not be said when it came time for reassembly). The corrosion on the gear legs was cleaned up by soaking the gear legs in Alumiprep 33 which is basically phosphoric acid with cleaners formulated to clean aluminum. Long time readers of the DOG Aviation Blog may recall Alumiprep 33 was also used when preparing all the wing ribs for primer. Because the surface of the gear legs are not perfectly smooth, a brass wire brush was used to help clean down into the pores of the metal.

In addition to being a product to clean and prepare aluminum for priming, Alumiprep 33 is also a great product for helping to remove surface corrosion on aluminum.


After using Alumiprep 33, it is necessary to give the parts a good rinse with water. Although not called for, I used distilled water for the rinse water. Unfortunately, after using Alumiprep 33 and rinsing the parts off really well ... as soon as the parts are dry, they need to be primed immediately. This made for a long work session by the time all the spray gun cleanup was completed.

Both U-1220 main gear legs freshly primed with Akzo epoxy primer and ready to reinstall.

Reinstalling the gear legs was a total fight … not fun … in fact, it was a pain in the neck both literally and figuratively. The difficulty stems from lack of access. When the gear legs are first installed on the RV-12 access is good because, in addition to the access hole in the belly skin, the F-1275G cover plate is not installed yet. Without the cover plate in position, the gear hardware is easily accessed with both hands. However, after the main gear legs are installed, the left and right F-1275G cover plates are riveted onto the fuselage leaving only a tiny slot for the gear legs to pass through.

Photo of the F-1275G cover plate … this plate is not riveted in place until after the gear legs are installed. As one can see from the photo, when the F-1275G cover plate is riveted in place, it eliminates all access for a second hand to reach the gear leg mounting hardware. This is one area where I feel using nutplates to secure the F-1275G cover plate would have been a great idea …. but in reality, once the main gear legs are installed, there is no need to remove them on a regular basis. That said, having the F-1275G cover plate secured with screws would sure make checking the bolt torque much simpler.


The lack of access created a huge problem dealing with the U-1202 outer attach bracket and associated bolts … this is because only one hand barely fits into the inspection hole on the belly of the airplane making it seemingly impossible to hold the bracket (which is about 6" or so further in from the access hole) and install a bolt at the same time all with one hand. After fighting and fighting with the hardware inside the center channel for a very very long time and exhausting my entire dictionary of choice cuss words, Bernie came up with a brilliant idea that was simple and truly worked quite well … once we learned the “how to”, quick progress was made. Bernie suggested sliding a wooden dowel rod or brass rod into the gap between the gear leg and fuselage skin to hold the bracket in place so the mounting bolt could be inserted. This worked out great! As an example, I could roughly position the U-1202 attach bracket and Bernie inserted the rod to hold the bracket in position so I could let go of the bracket and free my hand  for inserting a bolt into the bracket and subsequently up into the center channel. This method also came in handy when torqueing the bolts on the attach bracket … I could not see the bolt when my hand was in the access hole, so I would hold the socket end of the torque wrench so I could feel it slip onto the bolt then Bernie reached in with the rod and pushed up on the torque wrench to keep it in position on the head of the bolt while I repositioned my hands to the handle to begin torqueing the bolt.

Bernie’s idea of inserting either a brass rod or dowel rod through the gap adjacent to the gear leg and pressing up on the U-1202 bracket or the torque wrench to free my hand for a few moments worked great.


With both main gear legs now reinstalled, bolted and torqued down ... the axle, caliper and brake assemblies were reinstalled on the gear legs. Decided to switch the wheel bearing grease to a full synthetic grease so the wheel bearings were washed in mineral spirits (akin to Stoddard fluid) and blown out with compressed air. This was repeated three or four times until the bearings were spotless. I would caution fellow builders not to let the bearings spin when blowing them off with compressed air …. it is always a temptation, but it is truly not good for the bearings. After hand packing the bearings with fresh full synthetic grease, the wheels were placed back on the axles.


The following was mentioned previously in the Blog the first time the wheels were installed ... but bears repeating. The wheel assemblies used on the RV-12 are manufactured by Matco. The wheel bearings supplied by Matco for the wheel assemblies used on the RV-12 ARE NOT the typical automotive wheel bearing so the procedure for tightening the axle nut is different. On a car, the axle nut is tightened until there is a slight drag placed on the wheel bearings then the axle nut is backed off a little and locked in place with a cotter pin. This method will not work for the Matco wheels used on the RV-12 because the bearings used by Matco have a built in grease seal. The procedure for tightening the axle nut on the Matco wheel is to tighten the axle nut while slowly rotating the wheel … all the while looking at the grease seals. The grease seals will spin with the wheel until such time as there is sufficient pressure applied to the bearings by the axle nut that the pressure prevents the grease seals from spinning when the wheel is rotated. This is UNLIKE a car wheel because the axle nut IS NOT backed off from this point. In fact, if the cotter pin won’t drop into one of the holes in the axle, the axle nut is TIGHTENED a little further until it does. The result is not a free spinning wheel, but one that has a little bit of drag … this is fine, because the bearings are designed this way.

RV-12 Nose Gear Fork Upgrade/Modification

Now that the DOG Aviation RV-12 is out of service for the annual condition inspection felt it would be a good time to change the nose wheel fork to the new WD-1230-1 RV-12 gear fork Van’s Aircraft has changed over to. The reason behind this change stems from a few RV-12 builders experiencing cracking of the nose forks adjacent to the welds and in a couple of cases, a complete collapse of the nose fork. It is felt that extensive flying from sod fields was a major contributing factor to the stress cracks forming.


To Van’s credit, the nose fork was redesigned and made from much thicker materials and the nose wheel mounting hardware was also changed in such a fashion to allow for full torqueing of the wheel axle without pressing on the bearings. (With the old assembly, the wheel nut was tightened until the wheel bearing was compressed creating a drag on the wheel then the nut was backed off 1/4 turn… the new hardware allows the axle nut to be tightened to full torque specs for the hardware without compressing the bearing to the point of placing a drag on the wheel).


Because the DOG Aviation RV-12 will be flown almost exclusively from paved runways, I was not going to change the nose wheel fork to the new model. What tipped the scale in favor of making the switch now was discovering wheel pants (still sitting on the shelves) installed on the old nose wheel fork can be reinstalled on the new nose wheel fork assembly … but it requires drilling six new  mounting holes. So, should I switch to the new nose fork at a later date after installing the wheel pants on the old style fork, it means there will be six vacated holes that will need to be filled, sanded and of course the wheel pants will need repainting. After hearing that, decided to just switch over to the new wheel fork now and that way there won’t be any issues when attaching the wheel pants when I get around to it. So the new nose fork was ordered along with the hardware changes necessary to install the wheel fork and wheel pants.

Photo of all the parts that come with the new wheel fork assembly and the additional hardware for the wheel pant attachment. The bag contains wave washers, new wheel spacers, longer bolts for the tow bar mounting point and a longer axle bolt with lock nut.


The above parts were separated where necessary, edges smoothed then the parts were prepared for primer then sprayed. One major difference that is quickly apparent is how much thicker the material is on the new nose fork which is very evident when looking at how the wheel pants will mount. As can be seen in the photo below, the old nose wheel fork was bent forming a flange that the wheel pants attach onto with nutplates … because the new wheel fork material is so much thicker, aluminum brackets need to be riveted onto the new nose wheel fork using long AN470AD4-9 rivets so there is a mounting surface for the wheel pants. One tip here, if priming, try not to get any primer inside the bushing the axle passes through or the two bushings that are on either side of the wheel because it will need to be removed to allow the axle bolt to pass through the tight fitting bushings … ask me how I know?


Frequent readers of the DOG Aviation Blog know I embrace modifications that make sense to me … so prior to installing the new nose fork, decided to add a grease fitting so the two bushings inside the nose fork can be kept well lubricated. The modification was quite easy ... just drilled a hole in the front of the new nose fork and tapped it for a standard grease fitting thread.

As one can see in this photo, the new WD-1230-1 nose wheel fork for the RV-12 on the left is much beefier than the old nose wheel fork on the right which was thin enough to bend creating a mounting flange for the wheel pants. The new wheel fork is too thick to bend like that, so there are rivet holes along the upper edge what will allow for mounting a bracket onto the side of the wheel fork for later use to mount the wheel pants. Also of note, one can see the grease fitting modification that was added to the nose fork.


Decided to begin the condition inspection by placing the RV-12 on a sawhorse so the new nose wheel fork could be installed. The new nose wheel fork comes with longer AN5 bolts for the toe bar attachment points (all the old washers are reused). Because I plan on installing the wheel pants in the near future, also riveted the mounting brackets in place. With the nose fork now ready to install, the swap was easy … but I did run into a small confusing hiccup by not looking at the new drawings. At first, I incorrectly “assumed” that the two Belleville washers and flat washer that were under the castle nut of the old nose wheel fork would be reused … but the hole in the gear leg for the cotter pin was not visible. I quickly figured out if the flat washer was removed, the hole for the cotter pin would be visible … when all else fails read the instructions. After referring to the new drawing, sure enough, it was discovered the large flat washer is not used with the new nose wheel fork … the castle nut now rides directly on the Belleville washers.


Prior to installing the cotter pin, one thing that needs to be checked is the preload tension … which should be between 18-20 pounds. A piece of wire was placed through the holes for the axle bolt and attached to a digital fish scale. The fish scale is pulled on until the fork swings and the castle nut is progressively tightened to compress the Belleville washers until the nose wheel fork swings at the desired 18-20 pound pull. The assembly ended up around just slightly over 20 foot pounds because that is where the existing hole for the cotter pin aligned with a slot in the castle nut.

The flat washer in my fingers is not used with the new WD-1230-1 RV-12 nose gear fork assembly.. only the two Belleville washers and the castle nut are reused to mount the nose gear fork onto the nose gear leg. The mounting brackets for the wheel pants can be seen here riveted onto the nose fork with AN470AD4-9 rivets.

Completed instillation of the new WD-1230-1 nose gear fork with grease fitting modification on the DOG Aviation RV-12.


With the nose wheel fork upgrades now complete, decided to direct my attention to the main gear legs which were overlooked during the priming session for the finish kit parts. More about that in the next posting.