Sensenich Propeller Installed – Another Welcomed Milestone

As mentioned in the previous post, one of the Sensenich provided mounting bolts to be used for mounting the propeller’s inner hub to the propeller flange on the Rotax ULS engine was the wrong size. Friday the correct propeller bolt was received from Van’s and immediately taken to the hanger to be put to use installing the Sensenich propeller onto the DOG Aviation RV-12.

Armed with the correct bolt, it’s time to begin instillation of the Sensenich propeller.

The RV-12 utilizes a Sensenich 2A0R5/R70E Rev. F two blade, composite, adjustable pitch (only ground adjustable, not during flight) propeller. The root of each composite blade has a round flange that seats into recesses in the inner and outer hubs and become sandwiched between the hubs. While the hub bolts are loose, the propeller blades can be twisted independently of one another to obtain the desired propeller pitch. There is a pitch gauge provided with the propeller that slips into holes in the forward hub so the blade can be twisted until a pin touches the gauge … but Van’s now suggests using the Sensenich gauge as a starting point during assembly and setting the final pitch using a digital level with a Van’s provided tool that slips onto the edge of the propeller.

The Sensenich 2AOR5/R70E two blade, composite, ground adjustable propeller blades.

To begin the instillation, the inner hub needs to be bolted onto the propeller flange on the Rotax 912 ULS engine along with the S-1202 spinner plate. The hub instillation is easy …  six bolts, six nuts and six bushings and twelve NordLock washers are used to mate the inner hub and S-1202 spinner plate onto the flange on the Rotax engine. Double sets of NordLock washers are used … one under the head of the AN5-15A bolt and another on the backside of the flange bushings under the lock nut. Once a bolt is inserted through the propeller flange on the engine, a flanged bushings are inserted from the aft side of the propeller flange on the engine and slid into recesses on the aft side of the propeller hub. Once the propeller’s hub and S-1202 spinner plate are in place the bolts are torqued to 18-20 foot pounds.

Propeller’s inner hub and S-1202 spinner plate attached onto the engine’s propeller flange. The bolt and NordLock washer in my right hand is inserted from the front of the propeller hub. The flange bushing, NordLock washer and lock nut in my left hand go on the aft side of the propeller flange on the engine … the flange bushing are inserted through  holes on the propeller flange and slide into recesses in the propeller’s hub … NordLock washers and lock nuts hold it all together.


Installing the propeller’s separate blades, outer hub, Van’s S-1208 spacers and S-1203-1 front spinner bulkhead is a hand full of parts for one person to juggle at one time so I gave Bernie a call for 5 minutes of assistance …fortunately Bernie was out running errands on his motorcycle and not too far from the airport. The order of assembly begins with placing both propeller blades in the recesses on the inner hub. Next an AN5-24A bolt with a NordLock washer is placed through the S-1203-1 front spinner bulkhead then the S-1208 spacer is slid over the shaft of the bolt and the bolt is inserted into the propeller’s outer hub. The easiest way to assemble all the parts is to first insert all the bolts with NordLock washers through the S-1203-1 front spinner then slide on all the S-1208 spacers so the parts can be mated to the prop hub as one assembly. While the propeller blades are being held in position, the outer propeller hub is placed over the blades. With one person holding the outer hub in position over the two propeller blades, the other person brings the previously assembled parts in position and inserts the bolts into the outer hub and threads the bolts into the inner hub. With Bernie’s assistance holding one of the propeller’s blades, and firmly pressing the outer hub against the two blades, the parts were installed without mishap. Because the propeller blades are composite and hollow, the blades are quite light for their size so there was no fighting necessary to keep them in position.

Bernie positioning one of the propeller blades to fit into the recess in the inner hub. Of note: The pin that is used with the aforementioned Sensenich pitch tool is visible just above the pitot tube protruding from the propeller blade’s round root.


Prior to torqueing the bolts for the propeller, there is a procedure in the new version of the instructions that instructs the builder use a digital level to set the pitch of each propeller blade. The process begins with leveling the propeller by setting blocks of wood on the flat spots on the hubs and spanning the wood with the level and adjusting the prop position for level.

Because the center of the propeller hubs are rounded, two blocks of wood are used to elevate the digital level to clear the round center of the prop hubs so the blades can be leveled. The blades are positioned at level.


After leveling the propeller blades, the digital level is to be placed on the canopy rail and zeroed making the canopy rail a reference point … this is done so the propeller can be removed for inspections and installed back to its original position or for making pitch adjustments that are consistent and repeatable . After zeroing the level to the canopy deck, without turning the level off it is to be placed on a Van’s provided metal tool appropriately named TOOL-00002. The TOOL-00002 is hung from the propeller and the digital scale is placed up against the tool to read the pitch angle. According to the instructions, an initial pitch of 71.4 degrees is to be achieved which should get the propeller in the ball park for the initial engine start. Later, prior to the first flight, the pitch may need to be adjusted if the engine’s maximum ground RPM does not fall into a desired range.


Of course, at DOG Aviation there has been a steady diet of modifications … so modifying the TOOL-00002 prop tool to make it more user friendly seemed to be the thing to do. Before Van’s began including the TOOL-00002 adjustment tool with RV-12 powerplant kits, builders were making their own fixtures for digital levels so accurate propeller pitch adjustments could be made. One digital level was suggested because it has a 1/4-20 threaded hole in the bottom of the level for a tripod mount making it easy to attach to a fixture for measuring the angles of the propeller’s blades. At the beginning of the RV-12 project the DOG Aviation procurement department purchased one of the levels. Unfortunately, the Van’s tool did not have mounting a hole for the digital level so after checking clearances, decided to drill a hole in the TOOL-00002 prop tool so the digital level could be attached directly to the tool using a 1/4" bolt. Admittedly, I’m not too thrilled with the Van’s tool compared to some I have seen other builders make … but it does work.

A single 1/4" hole was drilled into the TOOL-00002 pitch tool so a digital level can be attached to the pitch tool without relying on the anemic magnets on the bottom of the level.

Return from the future: The position of the level in the above photo is incorrect. Nick a fellow builder caught this error. The blade should be pitched so the level leans to the left and NOT to the right as in this photo. The TOOL-00002 with digital level attached sitting on a propeller blade ready to be used to fine tune the propeller blade’s pitch.


Using the fixture in the above photo each propeller blade was adjusted to 71.4 degrees after the level was zeroed to the canopy deck. I found as the bolts were tightened, the settings changed a bit because the bolts were left a little to lose initially. After snugging up the propeller bolts a little but leaving them lose enough to be able to move the blades with two hands, the pitch was adjusted again. This time as the bolts were cinched down the pitch did not move. The propeller bolts were torqued in three stages to a final torque of 19 foot pounds.

After adjusting the pitch for each blade to 71.4 degrees (using the canopy deck as a zero reference) the six AN5-24A bolts were tightened in three steps to a final torque of 19 foot pounds.

Completed instillation of the Sensenich 2AOR5/R70E two blade, composite, ground adjustable propeller on the DOG Aviation RV-12. Need to attach the spinner next.


Return from the future: The euphoria was short lived. Fellow builders reading the DOG Aviation Blog take heed …. There is no point in setting the final pitch or torqueing the propeller bolts until after the spinner is completed, because the propeller blades MUST come off to complete the spinner instillation as I just found out reading ahead. My bad, I missed that in the last sentence in 47-05 step 5 of the plans during the initial reading. Drilling the holes for the spinner's nutplates needs to be done from inside the flanges on the S-1202 and S-1203-1 spinner bulkheads.

Exhaust Temperature Probes Installed & Prop Bolt Woes

While the Loctite 241 used to glue the S-1207 bushing into the spinner cured, decided to continue chipping away at small tasks along with preparing items that will be used for the oil line purging process which will remove air from the Rotax’s oil lines and internal oil galleries and replace it with oil. Photos of the setup will be posted when the purging takes place. Another small task that needed finishing was instillation of the two exhaust temperature probes.


The two Dynon supplied exhaust temperature probes for the Rotax 912ULS engine are to be inserted into predrilled holes in the #3 and #4 exhaust pipes. The temperature probes come with a machined flange that only allows the probes to be inserted into the exhaust pipe to a pre-determined depth. A band clamp is part of the probe and wraps around the exhaust pipe ... when tightened around the exhaust pipe, the band clamp pulls down on the probe’s flange to keep the probe firmly seated to the exhaust pipe. Instillation is quite easy, in that the probes are inserted into the exhaust pipe, the band clamps are wrapped around the exhaust pipe and tightened down … presto done. Well not quite, the wires from the probes need to be wire tied in place.  I found this to be the most time consuming part of the task, especially for the #3 cylinder because after being attached to an adjacent water line with wire ties and routed aft, the probe wire is wire tied onto the fuel supply line and follows it upward … unfortunately, there is only room for one hand to get to this area. I found a hemostat was quite helpful here to act as a second hand  to hold the wire tie at a few locations.

Tightening the band clamp to keep the exhaust temperature probe for the #3 cylinder firmly seated in the exhaust pipe.

Routing of the #3 cylinder’s exhaust temperature probe's wire aft along the water line.

Not having room for a second hand, using a hemostat to hold one end of a wire tie worked quite well to get the wire tie started ... then the hemostat was moved to help pull the wire tie snug to secure the #3 exhaust temperature probe wire onto the fuel supply line.


Installing the #4 cylinder’s exhaust temperature probe was much easier, in that, the probe’s wire follows the fuel line for the left carburetor … which is totally in the open with great access for the wire ties. At the midway point on the engine, the probe wire is routed aft along the fuel supply line to the spade connectors that will connect the exhaust temperature probes to the Dynon EMS (Engine Monitoring System) in the instrument panel.

Wire for the installed exhaust temperature sensor for the #4 cylinder runs adjacent to the fuel line for the left carburetor and over to the red spade connectors in the background that run to the Dynon EMS.


Prior to beginning the purge test or completing the spinner instillation, the propeller needs to be installed …  so the Sensenich propeller box was opened and parts pulled out to complete the instillation. Another bump in the road was discovered, in that, a bolt of the wrong size was shipped with the propeller. Unfortunately, this was not caught at inventory time because the propeller hardware was left in the bag and only the bolt heads were counted ... so I’m partially to blame for not catching this much earlier. In this case, the propeller and mounting hardware is supplied by Sensenich … NOT Van’s. The problem is Sensenich shipped an incorrect AN4 bolt instead of an AN5 … plus it is way too short. Even though Van’s did not make the screw-up, they are going to send out a replacement AN5-15A bolt ASAP. Below is a photo of the parts that came with the propeller from Sensenich.

Propeller mounting hardware as received from Senenich. Note the bolt in the far right is NOT correct … it should be the same size as the five to the left of it.


While waiting for the bolt to arrive from Van’s decided to look ahead and discovered the engine controls utilize two Adel clamps … one attaches onto the engine mount and the other clamps around the control cables. Discovered the way the oil return line was routed it was somewhat in the way … so it was moved to the right side of the supply fuel line to free up the space for the Adel clamps on the left side of the supply line. Installing dual Adel clamps can often times be a challenge, but fortunately there was just room enough for my Adel clamp tool which really came in handy to hold the Adel clamps together so a screw and nut could be started. The screw will be left lose until all the control cables are installed.

Installing the dual Adel clamps that will support the throttle and choke cables for the Rotax engine. Fortunately there is enough room at this location to use an Adel clamp instillation tool which keeps the bottom Adel clamp compressed together so a screw and nut can be installed through the upper clamp without a fight.

Fuel Tank Installed With Fuel Sump Modification & Bushing Placed In S-1201 Spinner

Saturday was a mixed event day as work bounced between a handful of small tasks, two of which notable … the spinner and fuel tank.


At the tip of the S-1201 spinner there is an epoxy plug that was predrilled at the factory for a bushing to be installed. The “point” on the tip of the spinner needs to be sanded or filed down evenly until a flat spot is created which is the same diameter as the S-1207 bushing. By filing the flat spot to the same diameter as the S-1207 bushing, when inserted into the spinner, it will match the curve of the spinner. The edges of the hole were tapered so the bearing fits snug and the inside of the hole was sanded a little with a fine piece of rolled up sandpaper until the bearing slid into the hole in the spinner. Once a good snug fit was accomplished, the portion of the bushing that is inserted into the spinner needs to be scuffed up with a coarse sandpaper a little so it can be glued onto the spinner with Loctite 241 (blue).

Filing the tip of the S-1201 spinner while rotating the spinner to insure the flat spot being created is even.

Test fitting the S-1207 bushing in the tip of the S-1201 spinner.

S-1207 bushing glued into the S-1201 spinner using blue Loctite 241.

While the Loctite 241 on the spinner and bushing was left to cure, attention was directed to installing the RV-12’s fuel tank. The fuel tank is installed with three bolts … one bolt at the aft end of the fuel tank at the baggage bulkhead and two special bolts used to attach the fuel tank to the center channel. The center channel bolts have evolved over the years the latest version being Rev2 with holes drilled into the center of the bolts to .370. The reason for the head of the bolts being drilled is to protect the fuel tank should there be such a hard landing or event that causes the center channel to buckle or distort. The theory being the bolts will shear off so the fuel tank won’t become distorted during the event and possibly breached. Care needs to be taken when installing these bolts so they are not over torqued … a torque wrench is your friend as the tightening is critical so the bolts do not become over torqued and shear while being tightened  … the standard torque of 20-25 inch pounds for AN3 hardware is used.

Installing the rear attach bolt that secures the aft end of the fuel tank onto the baggage bulkhead.

The two Bolt-00002 Rev 2 - .370 shear bolts that bolt through the center channel and into nutplates on the fuel tank.

Torqueing one of the two shear bolts Bolt-00002 Rev 2 .370 that secure the forward portion of the fuel tank to the center channel.


Prior to installing the fuel tank's outboard shear bolt, a ground wire modification was added. It has been reported by a few RV-12 builders that the pro seal on the fuel tank’s sending unit prevented the sender from getting a good electrical ground … so when the screws for the sender plate were installed last fall, a separate ground wire was added as a preemptive strike. The ground wire connects directly to the fuel sending unit on the fuel tank and runs to the fuel tank’s outboard mounting bolt at the center channel.

My fingers are pointing to the two Bolt-00002 Rev 2 - .370 shear bolts used to attach the fuel tank to the center channel. Note the outboard bolt has the black ground wire modification.


With the RV-12’s fuel tank secured in position, it was time to get underneath the fuselage to attach the fuel supply and return line to the fuel tank. Another modification is being installed here originally developed by Jerry Parr a builder (from England I believe) that adds a fuel sump under the fuel tank along with a CAV-110 aircraft fuel drain valve. Having a fuel sump and drain directly under the fuel tank makes good sense to me and is a modification I wanted to install on the DOG Aviation RV-12. Normally, the supply line sweeps up and connects directly onto a flair fitting on the bottom of the fuel tank. With this modification a short pipe with flared fittings on both ends is made as short as the flaring tool will permit. This short fuel line will connect directly onto the bottom of the fuel tank the other end will attach to an AN826-6D T fitting. The bottom of the T fitting is threaded and connects to an AN910-2D coupler. An AN912-1D reducer fitting screws into the coupler and finally the CAV-110 fuel drain valve screws into the 1/8” threaded hole in the reducer.

Fuel line modification to add a fuel sump and fuel valve directly under the fuel tank. From right to left the parts are a short piece of aluminum fuel line with flared ends, an AN826-6D T fitting, an AN910-2D coupler, an AN912-1D reducer fitting and finally the CAV-110 fuel drain valve.


Frequent readers may recall me posting a photo of this modification about a year or so ago. At that time the parts were ordered from a popular aircraft parts supplier and it was noticed the AN912-1D reducer would only screw onto the AN910-2D coupler 1/8 of a turn or so before binding. I knew the threads on the coupler were OK because other fittings screwed into it just fine … so the issue was with the AN912-1D reducer. I waited until last week and ordered another fitting hoping it would be from a different batch being a whole year later. Much to my dismay, it screwed on a little further … a whopping 1/4 turn before binding. These fittings are not the kind of fittings one can pick up at a local hardware store so the search was on to find some locally and quickly. Fortunately, I remembered race cars also use AN fittings for fuel and nitrous systems … so the DOG Aviation procurement department contacted Summit Racing and as luck would have it, was able to will call the fittings for a same day pick-up. Since this fitting is fairly inexpensive, I ordered two from different manufactures and they both fit just fine. The one from Aeroquip screwed on at least 2 ½ turns by hand so that is the one I went with.

The fuel line sump and fuel drain modification installed onto the bottom of the fuel tank. The main fuel line to the fuel pump attaches onto the horizontal leg of the T.


Unfortunately, a flashlight was not handy to illuminate the fitting at the tank but based on the photo showing all the parts for the modification, the viewer should be able to visualize how the modification connects to the tank. The brass CAV-110 fitting sits entirely below the fuselage skin.

The brass CAV-110 fitting sits entirely below the fuselage skin so a hole needs to be cut into an inspection plate so the fuel valve can protrude.


Return from the future: Creating the hole in the F-1276B cover plate has been completed and thought it would be appropriate to amend this post to show a photo of the completed cover plate thus keeping all the information for the instillation together in one spot. To read the post covering the drilling of the cover plate and information about the chosen grommet click on the following link:


Drilling F-1276B cover plate and grommet instillation.

A photo of the completed DOG Aviation RV-12 fuel line modification using a silicone outdoor rated grommet in the F-1276B cover pate for the CAV-110 fuel valve to pass through.

Preparing The Spinner For Instillation

Spent the afternoon out in the sun cutting away excess fiberglass from the RV-12’s spinner. The plans instruct the builder to transfer some markings on the outside of the spinner to the inside then cut the base of the spinner to within 1/16" of a scribe line that runs around the circumference of the spinner. After the big cut is made, the spinner is to be hand sanded to the scribe line.

Cutting around the circumference of the spinner using a Dremel tool outfitted with a cutting wheel.

Next step involves cutting out slots for the propeller blades. Here is where care needs to be taken because the fiberglass material removed will be used later ... so Van’s suggests using a fine toothed hack saw to make the cuts up the sides to where the curve begins. I elected to use a hand held hack saw and had great results staying right on the edge of the cut lines. The curved portion of the cutout is not used, so step a drill can be used to make a grouping of holes.

The area my finger is pointing towards needs to be removed as one piece. Prior to making the side cuts with the hacksaw blade in my hand, a few #30 holes were drilled as lead holes for a step drill which was used to make connecting holes in the area of the curve.


The hacksaw was used to carefully cut the sides of the slots in the fiberglass material up to where the curve begins so the fiberglass can be removed as a whole piece which will be used later. A sanding block and a bottle were used to sand the edges of the curve to the scribe lines.

After making the cuts with the hand hacksaw, the two pieces like the one I’m holding in my hand need to be saved because they will be reused. later.

Finished spinner … both propeller cutouts have been sanded smooth to the scribe lines.