Wednesday, November 30, 2016

The Reiff Preheating System -- Part 2

For the most part the last week has not been conducive to flying (nor will this week for that matter) so there has not been a rush to finish up the Reiff preheating instillation. Yesterday it was actually in the mid 50’s so decided to take advantage of the mild temperatures and head to the hangar and finish up the Reiff preheating system instillation on the DOG Aviation RV-12 … which at this point only requires installing the wiring.

Installing the wiring is very straight forward … the long wire with the Molex connectors at both end connects onto the wire from the Reiff  “HotStrip” affixed onto the bottom of the engine. The wire was routed adjacent to the aluminum tube for the fuel pump venting that traverses under the cylinders on the right side of the engine.
Routing the long wire with the Molex connector on both ends along the aluminum tube for the fuel pump vent.

The long wire was routed aft along the aluminum tube for the fuel pump vent. From there it then swings outward to follow the engine mount aft and upward at the rear of the engine alongside the oil tank where it follows the supply oil line over to the battery box area. The wire continues downward along the  side of the battery box/oil tank bracket where it plugs into a Y that connects to the main power cord. There is also a second Y that supplies power  to the thermostat that controls the temperature of the Reiff “HotBand” for the oil tank.
The path chosen for the wire to the Reiff “HotStrip” can be seen here wire tied alongside the aluminum fuel pump vent line under the right side of the Rotax 912ULS engine.
A photo of the routing along the aft portion of the engine where the wire is attached onto the engine mount with wire ties.

Van’s plans would have the builder drill two holes into the F-1201E-R oil tank side bracket so wire ties can be used to secure the electrical wiring. I was not fond of that idea because earlier RV-12’s developed cracks a little further aft of this location, which is why a second F-1201G brace was added.
Van’s plans calls for drilling two holes approximately where my fingers are pointing so wire ties can be inserted and routed to the holes for the oil tank mounting band further to the right.

Not wanting to drill holes in this area required a little fudging around to allow the Reiff wiring to be secured to the side of the F-1201E-R bracket … finally decided to take a different path and used a wire tie run through the hole for the oil tank mounting band and around through the lightening hole in the F-1201G braces this was done at the top and bottom F-1201G braces. The down side of this is that the wire ties are at an angle and wanted to skew the wires so to correct that complication, another wire tie was then slid under the first wire tie at each location to give me a place to secure the wires which I decided to place in a slit vinyl tube. Two tubes were used at the top and bottom of the F-1201E-R side bracket. In order to be able to secure all three of the  Molex connectors together to improve the instillation, I loosened the “HotBand” and rotated the band so the screw for the band clamp is now on the outboard side of the oil tank … this allowed for more slack in the wire allowing the Molex connector for the “HotBand” to be grouped with the other two.
Completed instillation of the Reiff preheater wiring along the side of the F-1201E-R side bracket.

To complete the instillation, the power cord was routed so the Reiff preheating system can be plugged into AC power by opening the oil door and plugging the Reiff system into an extension cord. The power cord also has a ground wire that should be connected to a ground point. I elected to crimp a ring connector onto the ground wire and connected it directly onto the negative terminal on the battery. The AC power cord is plenty long so it needed to be fan folded and wire tied onto the supply oil line to keep things tidy. The  AC plug for the Reiff preheating system was left on top of the supply oil line and to the side of the oil filler cap on the oil tank. This location keeps the plug out of the way when checking the oil level in the tank yet allows the plug to be accessed through the oil door opening in the upper cowl when use of the Reiff preheating system is desired.
Upper view of the completed instillation of the power cord for the Reiff preheating system.

After the wiring was installed and secured, the Reiff preheating system was plugged into AC power for a test. No arks, sparks or smoke and no tripped breakers … a good sign. Both the “HotBand” for the oil tank and the “HotStrip” for the engine began getting warm …a job well done.

Tuesday, November 22, 2016

Winterizing the RV-12 --- The Rieff Preheating System - Part 1

Knowing that winter was quickly approaching northeastern Ohio, a few weeks ago the DOG Aviation procurement department purchased a Reiff preheating system specifically configured for the Rotax 912 engine. The Reiff preheating system is designed to keep the engine and oil tank warm … improving cold weather starts and reducing engine warm up times.

As mentioned in the last post, Thursday’s test flight after working on the carburetors was kept short … but it also served the purpose of warming up the engine. Only two warm days remain before a forecasted instant 50 degree drop in temperature grips northeast Ohio, so decided after Thursday afternoon’s test flight was completed, the time had come to begin installing the Rieff preheating system for the Rotax 912 engine while the engine was warm and air temperatures at the hangar were still in a range that the epoxy could be kept warm enough to cure. The main reason about being concerned about the temperature stems from the slow cure epoxy used to install a couple of components in the Rieff preheating system onto the Rotax engine. The epoxy used requires near 70 degree temperatures to cure correctly and even at that, the cure time is 24 to 48 hours … that will be hard to accomplish in an unheated hangar when nighttime lows are 20 degrees and highs for the day around the mid 30’s. So I needed to sacrifice two wonderful 70 degree flying days to let the epoxy cure.

Rieff offers three preheating system kits specifically designed for the Rotax 912 engine. They are available in different wattages … 150, 250 and 350 watts. Because the winters in northeast Ohio are not as severe as some locations in the US, the DOG Aviation procurement department chose the 150 watt version based on the info from Rieff about the heating capabilities of the 150 watt system. The Rieff WEB site states “PERFORMANCE (standard 150 watt system) -  RV-12 aircraft in a hangar with two tennis balls plugging the air inlets, towel stuffed in oil cooler inlet, and blanket over the cowl Ambient temp 20-23F …. After 12 hours of heating time oil temp was 96F (temp rise of about 75F above ambient) Temp measured by Dynon engine monitor”. Based on that information, I feel the 150 watt system should work nicely here in northeastern Ohio. If it is much colder than 20 degrees, I think I would likely prefer staying at the house reading a good book.

The 150 watt Reiff preheating system for the Rotax 912 engine chosen for the DOG Aviation RV-12 consists of two heating elements, a thermostat, a pack of epoxy, wire ties and wires with premade connectors. One of the heating elements is for the oil tank and the other heating element is for the engine case. The heating element for the oil tank is a long 50 watt “HotBand” stainless band clamp which has an orange colored heating element affixed onto the band. The second heating element is a 100 watt "HotStrip" and attaches onto the bottom of the engine casing with the epoxy. The thermostat is attached onto the oil tank and it too requires being affixed using epoxy.
The 150 watt Rieff preheating system for the Rotax 912 engine. The kit consists of  a “HotBand” 50 watt heater for the oil tank, an associated thermostat, a “HotStrip” 100 watt heating pad for the engine casing, associated wires with preinstalled connectors and a package of slow curing epoxy.

Instillation is fairly straight forward, the “HotBand” clamp is installed around the oil tank and snugged down, but not over tightened … over tightening will damage the heating element. The areas on the engine and oil tank that will have epoxy applied are to be scuffed with a ScotchBrite pad and cleaned with solvent to remove oils. The smooth side of the “HotStrip” also receives a scuffing with a ScotchBrite pad and cleaning with solvent.
My right hand is pointing to the 50 watt Rieff “HotBand” that is snugged up around the oil tank. My left hand is pointing to the thermostat that was slathered with epoxy and affixed to the oil tank using masking tape to hold its position while the epoxy cures.

Next, a socket is used to roll over the plastic epoxy package to mix the two part epoxy components together. The epoxy is then slathered onto the bottom of the 100 watt “HotStrip” and it is affixed onto the bottom of the engine casing on the right side adjacent to the #1 cylinder. I used a piece of wood wedged between the oil cooler and the “HotStrip” to keep the strip seated firmly onto the engine casing. I later discovered this area presented more of a challenge than I thought it would in that, the engine casing is at an angle and much to my surprise the “HotStrip” slid away from where I had originally placed it. It is OK but now it looks much messier because there are smears of epoxy all over the bottom of the engine. If I had it to do over, I think I would have used a piece of duct tape to prevent movement in addition to the wood or a foam block to keep upward pressure on the “HotStrip” while the epoxy cures.
Using a piece of wood to keep upward pressure on the “HotStrip” to keep it pressed up onto the engine casing. The unexpected result of this is that the “HotStrip” moved a little. Fortunately, the 100 watt “HotStrip” slid towards the case screws and not the other way where it would likely have fallen off the bottom of the engine due to the slope in the engine case at this location.

While the epoxy cures on the engine, the remaining epoxy in the package is to be placed in a freezer overnight because it will be used again the next day. The following day, the remaining epoxy is used to overlap the edges of the “HotStrip” this will prevent it from falling away from the surface of the engine should it loosen up from the epoxy on the bottom of it.

To offset the cooler night time temperatures, a piece of plastic covered with a moving blanket was placed over the engine. Two halogen shop lights were used to create heat … one placed under the oil tank area and the other placed under the engine near where the epoxy was applied to the “HotStrip”. The halogen lamps generate quite a bit of heat so, until the temperatures make the big plummet forecasted, the two lamps should allow the epoxy to stay warm enough during the evening hours so it cures nicely. Only have 36 hours for this to pan out after that ... winter will arrive in northeastern Ohio in one big blast.
A piece of plastic and moving blanket are being used to trap heat from two halogen lights so hopefully the epoxy can cure correctly on the thermostat affixed to the side of the oil tank and the “HotStrip” affixed onto the bottom of the engine casing.

The day after the above photo was taken, a quick trip was made to the hangar to check on the progress … the epoxy appeared to be curing nicely so the remaining epoxy was applied to the edges of the "HotStrip"  per the instructions and left to cure. Have not completed the wiring because  decided to stay hunkered down at the house. We were in the 70’s on Friday and on Saturday plummeted to lows in the 20’s with daytime highs in the 30’s with snow. After 35 years out in California the first winter cold and snow usually keeps me in the house until I get acclimated to the cold ... (which truthfully never happens). I still need to finish up on the Rieff preheating system ... the wiring connectors still need to be installed and dressed out with wire ties. Sounds like a good project when we get back into the 40’s.

Sunday, November 20, 2016

Takeoff Loss Of Power Experienced - After Fix Video

Earlier last week I was planning on making a trip to the furthest airport in my phase one fly off area. The air was cool and crisp, clear skies and very light winds …. a perfect day to begin working on seriously attacking the flight test cards.

After getting the oil temperature up and performing the preflight run-up, took to the active runway and decided on a 65 – 70 knot climb out. The engine was running good down the runway and developed over 5200 RPM as the climb out began. At about 250 feet off the deck I caught a whiff of fuel and a moment later there was a partial loss of power. I had lost approximately 1,200 RPM … I quickly throttled back some then advanced the throttle a little but the engine seemed “flat” so it was throttled to keep the engine around 4300 RPM where the engine was running OK and seemingly smooth , decided it best to abort the flight so called the tower for clearance to return to terra firma to conduct a “little FBI Double-O-Seven-type investigatin” to coin a lyric from a Jr. John song.

One of the really nice features of the Dynon SkyView is there is a built in flight data recorder that constantly records a plethora of parameters …  input from all of engine and fuel sensors, GPS, transponder, autopilot, airspeed, altitude, attitude, ect., ect. By default, the sampling rate is 16 times per second (this can be changed in the setup menus) which provides approximately 2 hours of very detailed data capture. If the sampling rate is lowered, then much more than 2 hours of storage can be obtained … as an example, a sample every 10 seconds will result in 150 hours of flight data storage.

Decided it best to make a data dump of the SkyView's log to a flash drive and try to analyze what happened ... this is done by saving the SkyView's data logs onto a flash drive plugged into the USB port. But before delving into that, I should mention the USB port under the instrument panel base connects to one of the USB ports on the back of the Dynon SkyView. The under the panel USB port is used for a plethora of tasks such as upgrading the SkyView’s firmware and allowing for the monthly updating of navigational data bases. In addition, third party chart software can also be utilized by the SkyView to display FAA sectionals, IFR approach plates and detailed airport diagrams called “Safe Taxi”.  Plus, the USB port allows flight plans to be loaded into the SkyView or saved from the Skyview along with allowing the pilot to make backups of all the SkyViews internal settings and the biggie for me at the moment, exporting of the SkyView’s user data logs. All of this can coexist on one flash drive ... it just requires plentiful storage space on the flash drive.

Some of the above features such as FAA sectionals, IFR charts and “Safe Taxi” airport diagrams require leaving a flash drive in the under the panel USB port so the SkyView can access the data as needed. This can present a problem, because a typical flash drive would extend down from the bottom of the instrument panel and could very easily be snapped off from contact with the knees or an arm. So one of the many niceties the DOG Aviation procurement department has recently purchased consists of two tiny PNY 32 Gig Elite-X USB flash drives. They are small  in stature (yet big on available storage space) … they are just long enough for the fingers to get on them to pull them out of the USB port. At 32 Gig, there is plenty of storage for the software revisions, monthly updates, third party charts, flight plans, saving internal settings and the biggie at the moment, saving the user data log recordings … with plenty of room left over. Two of the flash drives were purchased so one flash drive can be at the house to get updated with the latest maps, ect, then taken to the airport and swapped for the one in the SkyView.
As one can see in the above photo, compared to a rivet, the PNY 32 Gig Elite-X Fit flash drive is tiny and will not be subject to breakage from the knees because it barely extends beyond the USB port.

OK, back to the user data log dump … after making a safe landing and taxing back to the hangar, the flight data logs were saved onto one of the PNY flash drives to take home for analysis. Saving the user data logs to a flash drive plugged into the USB port is accomplished by pressing and holding buttons 7 & 8 on the SkyView to enter into the Setup Menu. The first item in the Setup Menu list is System Software … selecting this will bring the user to a sub-menu that has an entry of Export User Data Logs. Selecting Export User Data Logs will save the data logs onto the flash drive plugged into the USB port on the bottom of the RV-12’s instrument panel. The files are saved as a .csv file which is a computer file standard meaning … comma separated values. The Microsoft Excel spread sheet is capable of opening and displaying the contents of this type of file.

A tip for those builders using Excel to view the SkyView’s data log:  Do yourself a favor, after opening the data log file with Excel, click on the View tab on the top of the window and click on Freeze Panes … then select Freeze Top Row. What this does for you is freeze the top row which is where the name for each column is located … such as RPM, EGTL, EGTR, Fuel Pressure, Fuel Flow, ect. Freezing the top row allows the spreadsheet to be scrolled to where the event being analyzed takes place without losing the name for what the column represents. The user has to analyze what the numbers mean and form a picture in “your mind’s eye” as to how the numbers correlate with one another. So a lot of back and forth scrolling is needed … but there is a better way.

Getting high tech … deciphering the SkyView data log can be taken to the next level by using a service provided by a company named Savvy Analysis. Savvy Analysis offers a service for pilots that allows the Dynon SkyView’s user data log to be uploaded and converted into a graph chart which is visually much more meaningful …. various parameters can be selected by the user to be charted simultaneously, very cool!! And best of all, the service is free … unless you want them to analyze the data log results for you. Below is a copy of the Savvy Analysis chart showing the “event”… once I had the chart on the computer screen, I converted it into a .jpg file to post here on the Blog.
Uploading the Dynon SkyView’s data log to Savvy Analysis for conversion into a chart will yield an easy to look at chart of the event… which greatly aids in analysis of the event. Here the sudden loss of RPM can be seen accompanied with a cooling of the left cylinder’s exhaust gas temperature (EGT) while the right EGT remain unchanged. Looks like the carburetor for the left side went rich, probably due to the carburetor’s float needle valve getting stuck on a piece of debris.

As can be seen in the above chart, the Rotax 912ULS is turning out a steady 5,200 RPM during the climb out then instantly drops to roughly 4,000 RPM the exhaust temperature on the left side of the engine also takes a drop suggesting there was a rich mixture coming from the left carburetor. Also of note, at the time of the “event” the fuel pressure dropped from roughly 5.5 PSI to around 5 PSI which, to my way of thinking, would correlate with a stuck needle valve in the left carb reducing the fuel pressure because of the momentary excess flow of fuel. It is not a fuel pump issue because the minimum pressure for the Rotax 912ULS engine is 2.2 PSI so that is not an issue.

There are only a few things that would contribute to a carburetor going rich … excess fuel pressure (not the case here) choke being applied (it was full off) which leaves … floats sinking in the bowl, debris preventing the needle valve from closing, bad needle valve or float level adjustment being off … all of which require removing the bowls from the carburetors. So the bowls on both carburetors were removed for inspection. All the floats appeared to be floating nicely. Just to be sure, each float was weighed at 3 grams and each pair weighed 6 grams … so they are spot on weight wise. The left carb bowl (suspected problem one) had just one little speck of debris in it. I decided to turn on the master switch and use the electric fuel pump to flush out the float needle valves while moving them up and down with the float bracket. Next a check was made to see if the needle valves would stop fuel from flowing when closed … all seemed well. Also checked the arms on the float bracket which should parallel the body of the carburetor when in the closed position … both float brackets appeared to be correct. Interestingly, the right carburetor had much more debris in the bowl than the left carb did and also had a very small flake of what appeared to be a flat black paint or coating that appeared to come from the float brackets. This got me off on a short tangent thinking perhaps the wiring for the EGT probes got switched or the probes were attached to the wrong port on the engine monitor… I used a heat gun on the right exhaust pipe near the EGT probe to verify the Dynon SkyView data log file recorded the heat on the correct sensor … fortunately, it did so the “event” was a left carburetor event for sure.

After the carburetor bowls were placed back onto the carburetors, decided to make a test flight with a shallower climb out of 80 knots. The test flight reveled no engine problems. Engine RPM remained constant around 5,250 on the climb out until I pulled back on the throttle … so for the next few flights, will plan on staying in the traffic pattern for a handful of takeoffs and landings so I can incrementally steepen the climb outs to make sure the issue has been resolved. Below is a couple of videos of the takeoff and landing after working on the carburetors. The videos are heavily edited to meet the under 100 Meg requirements of Blogger. Unfortunately, the camera switched files just as I landed so there is a little skip in the video at that point as I landed with a slight thump. Also will have to make improvements on mounting location for Mike’s camera to get it a little sturdier so the camera does not rattle.

A takeoff video made after working on the carburetors all seemed to go well … had a steady 5,250 RPM on climb out although it was a shallower climb out than when I had the “event”.

During the landing, I kept the RV-12 purposely high until on final then slipped a bit to lose the excess altitude which can be seen during the period of time when the horizon looks canted while on final to the runway.

I would have flown a few more loops around the pattern but needed to get on the ground to install a winter heating system that requires temperatures around 70 degrees to cure the epoxy properly … and there are only two warm days left before the winter plunge. More on the  heating system in the next post.

Saturday, November 12, 2016

The Eagle’s Heavy Wing Issue - Solved!!!

A big shout-out to Tom in Kentucky …  thanks for posting on the VAF forums about your observation that your RV-12’s wing skins aft of the rear spar were not flat. It seems that Tom, much like myself, had a heavy wing … although Tom’s was the right wing and the DOG Aviation RV-12 had a heavy left wing. As mentioned in an earlier post, during early flight testing, I discovered a heavy left wing and followed Van’s suggestion of flattening out the aft edge of the flaperon on the light wing (right wing in my case). After flatting the aft edge just a little bit, went for a test flight and still had a heavy left wing, but seemingly slightly better.

Before bending more flaperon metal, decided to have a look on the VAF forums to see what others have done. I knew the rod end bearings were set correctly, so was looking for other options. Fortunately, I ran across Tom’s thread and read where Tom discovered the upper wing skins aft of the rear spar on his RV-12 were not flat … after Tom flattened the wing skins in this area, his RV-12 flew hands off without rolling. As mentioned in the previous post, decided to have a look at mine and sure enough, discovered I too had places on both wings where the skins were either low or high and proceeded to level this area on both wings.

Today I made a very late afternoon test flight during very calm conditions at the airport … the winds were very light with an occasional gust to 7 knots. There was no turbulence, so the RV-12 flew like it was on rails … I’m happy to report Tom’s suggestion regarding leveling the wing skins aft of the rear spar really made a HUGE!!! difference … no more heavy left wing!! Yay!!! The DOG Aviation RV-12 now flies level hands off.

A tip for fellow RV-12 builders that discover they too have a heavy wing: I would suggest prior to bending flaperon metal or adjusting rod end bearings (especially if you were meticulous when installing them), the builder should first consider taking a very good look at the skins aft of the rear spar. Drop the flaps to gain some clearance, then adjust the skins flat using a straight edge and block of plywood as documented in the previous post.  Fly again and if there is still a heavy wing, then look elsewhere … possibly getting draconian with the aft edge of the light flaperon or adjusting rod end bearings.

I’ve been holding off on really delving into the test flight cards since I have 40 hours to fly off, there is really no rush … so figured it best to tweak the RV-12 to obtain straight level flight first and then proceed to working through the flight test cards once the RV-12 flies straight ... which I'm happy to report, now it does.

Thursday, November 10, 2016

What To Do About The Heavy Wing?

After installing the trim tab and prior to making a test flight, a seeming tool was used to ever so slightly flatten the aft edge of the “light “ (in my case the right) flaperon in the hopes of reducing the heavy left wing. This is the Van's suggested method for correcting the issue.
Using a seeming tool with tape on the jaws to ever so slightly change the shape of the trailing edge of the right (light) flaperon.

After making a slight adjustment to the right flaperon, the RV-12 was taken for a few loops around the pattern to see how well the rudder trim tab worked and if there was any improvement with the heavy left wing issue. I would have preferred to have flown away from the airport for an hour or so but there was an approaching storm front, so I just remained in the pattern for a couple of loops. Since I did not get up to cruising speeds, not sure if any adjustments to the newly installed trim tab will be required … but initial indications are the trim tab has helped quite a bit with correcting the yaw component. Now onto the roll issue.

As for the heavy left wing, there was seemingly a very slight improvement, but the left wing is still heavy. So will need to delve into it a little more before bending more flaperon metal. Went online and did a little research on the VAF forums to see what others have done to resolve their RV-12 heavy wing issues. There was quite a mixed bag of solutions and combinations thereof posted by builders. Some involved adjusting the rod end bearings that support the flaperons to the wing, some involving adjusting the shape of the trailing edge of the flaperons and one in particular that caught my attention … adjusting the upper wing skin aft of the rear wing spar. I’m very confident my issue is not with a rod end bearing adjustment, because I was extremely fussy about making sure all the rod end bearings were screwed into the flaperons the exact same amount and went through great lengths to make sure the measurements Van’s gave in the plans were strictly adhered to, so I’m leaning towards ruling out making any rod end bearing adjustments at the moment.

The one post by Tom, a RV-12 builder in Kentucky, that really caught my eye mentioned he noticed a small difference in the upper wing skins between his left and right wings in the area aft of the rear spar. Tom said reshaping the upper wing skins in this area solved his heavy wing issue. For those not familiar with the way the RV-12’s wing is designed, there is a rear spar that runs along the span of the wing and the upper wing skins overlap this spar by a couple of inches. This is done to present a smoother airflow to the upper surface of the flaperons rather than having a large gap between the rear spar and the flaperons which would create a significant amount of turbulence over the surface of the flaperons. Anyway, I used a straight edge to check this area and sure enough, there were differences between the two wings and even on the same wing. In some places the aft edge of the upper wing skins were high and some places they were low. So using the straight edge and a piece of plywood, the wing skins were massaged until the wing skins aft of the rear spar were fairly straight.

The process begins with raising the flap handle to full flaps to open up the gap between the flaperons and the wing skins to make room for a block of wood. One can see in the following photos that at some locations the aft edge of the upper wing skins were low and other locations were high. Also of note, the amount of deviation was actually a lot more initially, but I began hand massaging the skins before thinking of taking any photos and using a piece of wood to really dial it in as close as possible.
Here one can see the upper wing skin that extends aft of the rear spar is bent down at this location and needs to be raised.
Using a piece of wood to flex the aft portion of the wing skin up to raise it a bit at this location.
In this area, the upper wing skin aft of the rear spar it too high, as can be seen in this photo.

With a lot of patience I was able to get both wings tweaked so the upper wing skins aft of the rear spar are now fairly consistent between the two wings and for the most part, flat aft of the spar. Will need to test fly the RV-12 and see if there is any improvement … I have a good feeling there will be a change, hopefully the one I’m looking for.